PRACTICAL SHIP PRODUCTION 5M? Qraw-MlBook & 1m PUBLISHERS OF BOOKS F O R-^ Coal Age ^ Electric Railway Journal Electrical World v Engineering News-Record American Machinist v The Contractor Engineering 8 Mining Journal ^ Power Metallurgical 6 Chemical Engineering Electrical Merchandising PRACTICAL SHIP PRODUCTION BY A. W. CARMICHAEL, LIEUTENANT COMMANDER, CONSTRUCTION CORPS, U. 8. NAVY. MEMBER SOCIETY OP NAVAL ARCHITECTS AND MARINE ENGINEERS. FIRST EDITION McGRAW-HILL BOOK COMPANY, INC. 239 WEST 39TH STREET. NEW YORK LONDON: HILL PUBLISHING CO., LTD. 6 & 8 BOUVERIE ST., E. C, 1919 COPYRIGHT, 1919, BY THE MCGRAW-HILL BOOK COMPANY, INC. THE MAPLE PRESS YORK PA PREFACE The purpose of this book is to present in convenient form the most important general principles of ship design, with which every naval architect should be familiar, and to describe the various processes in connection with the building of ships. Its nature is intended to be practical rather than theoretical, it being assumed that the principal problem with which the reader is concerned is the quick production of seagoing vessels from plans already in exist- ence rather than the preparation of new plans. The recent unprecedented increase in shipbuilding in the United States has resulted in a corresponding demand for workmen, draftsmen, and naval architects. It has there- fore become necessary for many engineers and technical men, who have never before been confronted with ship- building problems, to transfer their activities from the fields of the various other engineering professions to those of the marine engineer and naval architect. These men are fa- miliar with mechanical processes and have the necessary groundwork in theoretical and applied mathematics to fit them for duties in connection with the production of ships, but lack familiarity with those matters that are peculiar to shipbuilding. It is hoped that this book may aid in furnishing, in compact form, some of the more essen- tial parts of this information. It should also be of value to workmen in shipyards who have only such knowledge of the shipbuilding industry as they have gained from practical experience, and who desire to fit themselves for higher positions. It is manifestly impossible to include in a single volume even a most cursory treatment of all the subjects that are involved in the profession of naval architecture, Since, vi PREFACE however, matters of construction are to be considered more fully than matters of design, it has been possible to include enough matter to give a fairly complete general description of the various processes in the production of a modern steel vessel. A certain amount of space has been devoted to matters of a theoretical nature, but only in so far as it has been believed that these would be necessary for a proper understanding of the methods of construction. Certain diagrams, sketches and illustrations have been inserted where they were considered necessary for a proper understanding of the subject under discussion. Some of the sketches are not accurately proportioned, having been roughly drawn merely for the purpose of showing the principles involved. They should in no sense be consid- ered as working drawings. The subject matter presented is not new, but has been gleaned from many different sources. This book is in the nature of an introduction to a subject upon which many books have been written and of which a complete knowledge can be gained only by reference to these books, and by ex- tended experience. CONTENTS PAGE PREFACE v CHAPTER I REQUIREMENTS OF SHIPS Introductory 1 Buoyancy . 3 Stability 5 Propulsion 11 Steering ' 20 Strength 22 Endurance . 28 Utility 29 CHAPTER II GENERAL DESCRIPTION OF SHIPS Form 31 General arrangement 41 Types 50 Tonnage 61 Materials used in construction 63 CHAPTER III STRUCTURAL MEMBERS OF SHIPS Transverse and longitudinal framing 77 Stem, stern post, rudder, etc 91 Shell plating and. inner bottom 106 Decks 114 Bulkheads 121 Miscellaneous 124 CHAPTER IV DESIGN OF SHIPS Conditions to be fulfilled 130 Choice of principal elements 132 Construction of lines and distribution of weights 133 Principal plans 134 Final calculations 136 Detail plans and specifications 146 vii viii CONTENTS CHAPTER V SHIPYARDS PAGE Site for shipyard 147 Building slip and launching ways . . 156 Yard layout, shops, storehouses, etc 157 Shipyard machine tools, etc 163 Personnel of a shipyard 169 Management 178 CHAPTER VI PRELIMINARY STEPS IN SHIP CONSTRUCTION Ordering material 180 Molds, templates, patterns, etc ^ . . . . 182 Fabrication of material . 185 CHAPTER VII THE BUILDING OF SHIPS Erection 195 Bolting-up, drilling and reaming . 204 Riveting 209 Chipping, calking and testing 219 Protection against corrosion 224 Welding 227 Launching 231 Fitting out 237 INDEX . . 243 LIST OF ILLUSTRATIONS Fio. No. PAGE 1. Rectangular floating log 1 2. Forces acting on floating log 3 3. Centre of gravity and centre of buoyancy 5 4. Change in position of G caused by load on top of log 6 5. Transverse metacentre 6 6. Pendulum ...... 8 7. Variation of righting arm 9 8. Log hollowed out to form a vessel 11 9. Streamlines. 12 10. Developments of ship forms 13 11. "Similar" ships 16 12. Rudder 20 13. Solid and built-up hulls 23 14. Sagging and hogging 25 15. Curves for strength calculation 26 16. "Lines" of a ship -. 33 17. Parts of a ship 38 18. Inboard profile of cargo steamer 43 19. Types of ships 59 20. Shipbuilding shapes 65 21. Rivets 67 22. Types of keels 77 23. Simple transverse framing 80 24. Transverse framing 81 25. Frame, reverse frame, and floor plate 82 26. Intercostal side keelson 84 27. Side stringer 85 28. Cross section of a ship showing longitudinal framing 86 29. Diagrammatic view of cellular double bottom framing 86 30. Cross section of double bottom 87 31. Cross section of cellular double bottom with intercostal longitu- dinals 87 32. Longitudinal section of cellular double bottom showing intercostal longitudinal 88 33. Bracket floor 89 34. Watertight floor, cut by continuous longitudinals 89 35. Stern post and stem 92 36. Cross section of lower portion of cast stem 93 37. Solid cast rudder 95 38. Single plate built up rudder 97 x LIST OF ILLUSTRATIONS FIG. No. PAGE 39. Cast frame of side plate rudder 98 40. Pintle 99 41. Rudder carrier, etc 100 42. Bossing and stern framing 101 43. Bossing of a twin screw vessel 103 44. Propeller struts 104 45. Stern tube 105 46. Arrangement of plates in shell plating 108 47. Systems of shell plating 109 48. Butt lap with tapered liner (seen from outside) 110 49. Butt lap one plate tapered and chambered (seen from inside) 110 50. Stealer 112 51. Bulkhead liner 113 52. Connections of deck beams to frames 114 53. Deck beams and carlings 115 54. Connections at sides of watertight decks 116 55. Butt of deck planking over steel deck 117 56. Stanchion 119 57. Deck girders 120 58. Covers for openings in watertight decks 121 59. Bulkhead 123 60. Portion of engine foundation 125 61. Boiler saddles 126 62. Hawse pipe 127 63. Bitts and chock .128 64. Rail bulwarks, fenders, docking keel, bilge keels 129 65. Value of BM 137 66. Atwood's formula 139 67. Methods of integration 144 68. Making a shipyard 149 69. Building slips 151 70. Keel blocks and piling 152 71. Ship on launching ways - 153 72. Launching 154 73. Shipyard of the Submarine Boat Corporation 160 74. Operation of shipyard machine tools 164 75. Fabricated parts 167 76. Shipfitting work 174 77. Template and mold 184 78. Portion of bending slab, showing frame bending 189 79. Frame beveling 190 80. Flat and centre vertical keel plates in place on blocks 196 81. Drifting 197 82. Erecting double bottom framing 198 83. Portion of double bottom framing completely erected 198 84. Ship in early stage of construction 199 85. View from stern, showing frames, deck beams, and shaft tunnel . . 201 86. Cross section of building slip 202 LIST OF ILLUSTRATIONS xi FIG. No. PAGE 87. Wooden ship under construction 203 88. Reaming 206 89. Effect of unfair rivet holes and improper reaming 207 90. Method of using pneumatic drilling machine 208 91. Driving a rivet 210 92. Improperly driven rivets 211 93. Safe and unsafe loading of ropes 212 94. Safe and unsafe loading of riveted joints . . . 213 95. Cutting out rivets 215 96. Tap rivets 217 97. Calking 220 98. Red lead putty gun 223 99. Electric quasi-arc welding 230 100. Forces acting on ships during launching 233 101. Inclining experiment 239 PRACTICAL SHIP PRODUCTION CHAPTER I REQUIREMENTS OF SHIPS INTRODUCTORY A ship may be defined as a large seagoing vessel. In other words, it is a structure that will float and is capable of making ocean voyages. Its purpose is to furnish a means for over-water transportation. It may be con- sidered as an enlarged boat. It is convenient, however, SIDE ELEVATION END ELEVATION W. De ; i Freeboard 3th Water Line ^ L. W. Water Line i D^ft | 1 PLAN Be lm Longitudinal Centre Line FIG. 1. Rectangular floating log. at the start to consider it as a large floating log, as shown in the three views of Fig. 1. Referring to this figure, the following should be noted: the three principal dimensions are length, beam, and depth. The length is the greatest dimension and is measured horizontally. The beam is the breadth and is measured horizontally 2 PRACTICAL SHIP PRODUCTION . at right angles to the length, or as it is usually expressed, athwartships. The depth is measured vertically or at right angles to the surface of the water. The form is shown by the three views in the figure: side elevation, end elevation, and plan. (These plans are usually called by other names in the case of a ship, as will be seen later.) As the plane of the surface of the water is horizontal, the intersections of this plane with the log appear in the side and end elevations as straight horizontal lines. Each of these lines is called the water line, and each is usually marked by a U W" at one end and "L" at the other. The intersections of a vertical longitudinal plane through the longitudinal axis of the log with the log's form appear as straight lines, the one in the end elevation being vertical and the one in the plan being horizontal. They are usually marked " k" as shown in the figure, and are called centre lines. The draft is the vertical distance to which the log is immersed. The freeboard is the vertical distance that the log projects above the surface of the water. It is assumed that the log has a uniform rectangular section and that it is homogeneous and lighter than water. It will also be noted that it floats with its wider side hori- zontal. The reasons for this will be given later. Such a log represents the simplest form of floating body from which has been gradually developed the modern ship, and in the following pages the various steps in the evolution of such a ship from a simple floating body will be traced and the various requirements of all ships will be discussed. These requirements are as follows: Buoyancy. Stability. Propulsion. Steering. Strength. Endurance. Utility. REQUIREMENTS OF SHIPS 3 1. BUOYANCY Consider a log floating in equilibrium in perfectly still water, as shown in Fig. 1. Assume that the specific grav- ity of the log with respect to the water in which it floats is 0.5. A cross section of the log is shown in Fig. 2. When it is floating thus at rest and in equilibrium, the forces on the log will be balanced as follows: First. The forces of the water on the two ends will balance each other. Second. The forces of the water on the two sides will balance each other. Weight of Log Force of Buoyancy FIG. 2. Forces acting on floating log. Third. The upward pressure of the water uniformly dis- tributed over the bottom of the log will be balanced by the uniformly distributed weight of the log acting vertically downward as shown in the figure. It is therefore clear that the upward force of the water pressure which is called the buoyancy is exactly equal to the weight of the log. But if the space occupied by the immersed portion of the log be replaced by water, the con- dition of equilibrium remains unchanged, and therefore the upward force of the pressure of the water acting on the bottom of the log is exactly equal to the weight of the water displaced by the log, which is, in turn, equal to the weight of the log itself. 4 PRACTICAL SHIP PRODUCTION This is known as the "Law of Floating Bodies/ 7 and the proof given above for the case of a floating body of simple rectangular form may be extended to that of a body of any form by the method of resolution of forces. This law may be briefly stated for all ships as follows: The weight of any ship floating in water, including all that she carries, must equal the weight of the water that she displaces. When the draft at which any ship floats is known, it is possible to calculate the volume of the ship that is below the surface of the water. The weight of the ship plus all that she carries can thus be obtained, provided the density of the water in which she floats is known. In the case of the log referred to above (which has a density of 0.5), it is clear that the log will be half above and half below the water, since the weight of an amount of water of one-half of the volume of the log is equal to the total weight of the log. If the density of the log be in- creased, the amount of the log immersed increases, and if the density becomes greater than 1.0 the log will sink. Similarly, if the weight of a ship with everything that she carries becomes greater than the weight of the volume of water that she is capable of displacing, she will sink. The total weight of the log may be considered as acting vertically downward through its centre of gravity, and the equal force of buoyancy as acting vertically upward through the centre of gravity of the displaced water, or the centre of figure of the under water portion of the log. This point is called the centre of buoyancy. The centre of gravity of a floating object is usually called G, and the centre of buoyancy, B. In the case of the log, G is at the centre of the cross section and B is halfway between G and the bottom of the log. (See Fig. 3.) Since the force of buoyancy acts vertically upward and the weight of the log acts vertically downward, it is clear that for equilibrium G and B must be in the same ver- tical line, for, were this not the case, there would be a REQUIREMENTS OF SHIPS 5 couple tending to produce rotation, and equilibrium would no longer exist. This is another important law of floating bodies, and may be briefly stated: The centre of gravity and the centre of buoyancy of a ship floating in equilibrium in still water must be in the same vertical line. For the two principles just enunciated to be strictly true, it is necessary that the water be entirely displaced by the portion of the floating body that is under water. The "skin" of a ship must therefore be absolutely water-tight. The requirements of buoyancy for all ships and other craft may then be summarized as follows: 'The vessel must FIG. 3. Centre of gravity and centre of buoyancy. be so designed and constructed that it will float, in equilib- rium, in such a position as to displace by its hull an amount of water equal to its own weight. A simple rectangular log of the shape shown in the pre- ceding sketches fulfils this requirement, and such a log, if of sufficient size, might be used as a means for transport- ing merchandise or men over smooth bodies of water. It is probable that the first crude means of over-water trans- portation were logs. There are, however, certain practical difficulties in the way of this means, the principal of which is lack of stability a quality which will be next discussed. 2. STABILITY Let it be assumed that the log be loaded so that it sinks to a position as shown in Fig. 4, and let the total weight of the log and its load be W. The centre of buoyancy B will be 6 PRACTICAL SHIP PRODUCTION at the centre of figure of the immersed cross section, (Fig. 4 being assumed to be a transverse section through the middle of the log), but owing to the added weight on the top of the log, the position of the centre of gravity of the FIG. 4. Change in position of G caused by load on top of log. log and load will be higher than that of the log only. Any weight placed on the top of the log will tend to make it "top heavy." Suppose that the log and load be inclined from the ver- tical position, by some external force, to the position shown FIG. 5. Transverse metacentre. in Fig. 5. The centre of buoyancy, which is the centre of figure of the immersed portion of the log, will move from B, relative to the log, to some position, such as B f . The centre of gravity, G, however, remains unchanged relative to the log. Since the weight of the log and its load W and REQUIREMENTS OF SHIPS 7 the force of buoyancy must still be equal, there will be set up a couple, of force W, and arm GZ, GZ being the distance between the vertical lines through G and B'. If the ver- tical through B f intersects the line BG above G, this couple will tend to produce rotation in the direction shown by the curved arrow and to right the log. If it intersects. BG below G it will tend to produce rotation in the opposite direction, and to capsize the log. If it intersects it at G, there will be no couple and no tendency to rotation in either direction. The first condition (before the external force was applied) is called one of stable equilibrium; the second, one of unstable equilibrium; and the third, one of neutral equilibrium. The point M at which the vertical through B' intersects the line BG, is called the transverse metacentre, or often simply the metacentre. The distance GZ is called the righting arm and it will be noted that the greater the length GZ the greater will be the couple tending to right the log. Also, if e be the angle to which the log is inclined GZ equals GM sin 6, so that for any given inclination the greater the length of the righting arm the greater will be the value of GM. The position of M remains practically constant for small angles of inclination (up to say 10) and the length GM for such angles is known as the metacentric height. The higher M is above G, the greater will be the value of GM , the metacentric height, and of the righting arm, and consequently the greater will be the tendency of the log to right itself when slightly inclined from the upright position. It is apparent from the above that the amount of weight that can be carried on top of the log without unduly reducing the value of the metacentric height, and hence the tendency for the log to remain upright, is very limited. This tendency to remain upright is called initial stability. Since all weight added to the log above its own centre of gravity will result in the location of the combined centre of gravity moving upward, and since M is above G, to start with, the addition of weight on top of the log will reduce the metacentric height, GM. 8 PRACTICAL SHIP PRODUCTION G The metacentric height of any vessel is therefore a very important characteristic, since it is a measure of the vessel's initial stability, or safety against capsizing. The vessel may be considered as a pendulum of which M is the point of support and G the point at which the total mass may be conceived as concentrated. If M be moved down to G the pendulum will pass from a position of stable to one of neutral equilibrium. The instant M passes below G, the . equilibrium becomes unstable. (See Fig. 6.) The metacentric height is, however, im- portant only in that it is a measure of the initial righting arm. The righting arm multi- plied by the total weight of the floating body gives the value of the moment tending to pre- vent capsizing. For angles of inclination greater than about 10 the position of the metacentre changes, so that the righting arm itself must be considered. Let it be assumed that the log be loaded in such a way that its total weight, including the load, be W, and that its centre of gravity be as shown in Fig. 7 (1). Now let it be supposed that the log be inclined by some external horizontal force so that it passes successively through the five positions shown in Fig. 7 (1), (2), (3), (4), and (5). It will be noted that when the log is upright in the water the value of the righting arm GZ is zero, since the forces of the weight and the buoyancy both act in the same vertical line. As the log is first inclined, the length of the righting arm increases at a comparatively rapid rate, as shown in Fig. 7 (2). This is due to the fact that the centre of buoyancy is moving to the right of the figure on account of the increased immersed volume of the log on that side, the centre of buoyancy being the geometrical centre of figure of that immersed volume. It will be noted that after the right hand upper edge of the log is immersed, the movement of B toward the right still t. 6. Pen- dulum. REQUIREMENTS OF SHIPS 9 continues, but at a diminishing rate, because of the water now above the corner which causes the immersed centre of figure to slow down in its movement to the right. An in- clination will finally be reached (as shown in Fig. 7 (3)) at which the righting arm is a maximum, and its rate of in- crease is zero. Any further inclination will produce a di- minution in the righting arm which has already become smaller when the position shown at Fig. 7 (4) has been reached. Finally, at some such inclination as that shown in Fig. 7 (5), the righting arm will again become zero and the stability will vanish. (1) Upright Position (2) Upper Corner Immersed (3) Maximum Righting Arm (1) Angle of Inclination CURVE OF RIGHTING ARMS FIG. 7. Variation of righting arm. This inclination at which the stability vanishes is called the angle of vanishing stability or range of stability, and the inclination at which the righting arm is a maximum is called the angle of maximum stability. A curve is plotted in Fig. 7 showing how the righting arm increases to a maxi- mum, diminishes, and finally vanishes as the inclination increases from that shown in sketch (1) to that shown in sketch (5). From this curve it will be noted that the maximum righting moment occurs when the log is inclined to an angle of about 35 from its upright position, and that if the log be inclined to an angle much greater than 50 from the upright it will capsize. 10 PRACTICAL SHIP PRODUCTION These considerations which have been discussed in connection with the simple rectangular log, apply to all floating bodies, but in the case of ships and other vessels of irregular form, the mathematical calculations involved in obtaining values of the righting arms for various angles of heel become much more involved. It should also be noted that as well as being inclined transversely, the vessel may be at the same time inclined longitudinally, thus mak- ing the problem still more difficult. For practical purposes, however, in the case of ships it is usually sufficient to con- sider transverse inclinations only, since the length of ordinary ships is so much greater than their beam that their longi- tudinal stability is always ample. The elementary principles of stability enunciated above having been carefully considered it will be noted that the use of a log loaded on its top as a means for over-water transportation is very limited. If the weight be placed on the top, the centre of gravity will be raised and the initial stability consequently reduced. Also, the angle to which the loaded log may be safely inclined depends further upon the proportions of the log. Referring to Fig. 7, it will be noted that the amount of the log above water determines the point (2) at which the rate of increase of the righting arm commences to diminish and thus influences the range of stability (since that is the point at which the upper edge of the log becomes immersed). Furthermore, the width of the log influences the maximum righting arm since the point B 3 will be farther to the right, and the length GZ Z (in Fig. 7 (3)) greater if the width of the log be greater. Also, the higher the position in the log of G, which is the centre of gravity, the smaller will be the righting arm. The following points are therefore apparent from the standpoint of stability: first, the width of the log should, as a general rule, be greater than the depth; second, the amount of the log above the water should not be too small ; and third, the centre of gravity of the log and all that it carries should be kept as low as possible. These considerations led to the first step in the evolution REQUIREMENTS OF SHIPS 11 of vessels or floating objects hollowed out. By these means it becomes possible to carry the same load with the position of the centre of gravity much lower, thus increasing the stability and still retaining practically the same freeboard. (See Fig. 8.) A hollowed-out log or dug-out, the rude canoe of pre- historic man, was the first boat. As the need for larger craft was felt, it became necessary to use more than one piece of material, and canoes were then fabricated of wood, skins, bark, and other materials. But the object to be attained was still the same to secure a hollow structure that would keep out the water and permit a larger weight FIG. 8. Log hollowed out to form a vessel. to be carried without endangering the buoyancy and sta- bility. Consideration may now pass from the rectangular log to built-up, box-shaped vessels, which have the same external form and possess the first two requirements of a ship, buoyancy and stability. Such vessels can be safely loaded with large and heavy cargoes, but still are of little practical value unless they can be moved from place to place by water. 3. PROPULSION It is apparent from an inspection of Fig. 1, which may now be considered as representing a large water-tight floating box, that the water would offer considerable resistance in case it were attempted to move such a vessel 12 PRACTICAL SHIP PRODUCTION from place to place. It would, of course, be natural to move the vessel endwise rather than sidewise, but even so, the square ends would offer a great resistance to the water. Figure 9 shows the paths of the particles of water relative to such a vessel moving in the direction indicated by the arrow. These paths of the water particles are known as stream lines. The end of the vessel that enters the water is called the bow, and the other end, the stern. Owing to the sudden change of direction of the stream lines at the bow and stern, considerable energy must be expended in driving Eddy Stern Bow Eddy Eddy FIG. 9. Stream lines. or towing such a vessel through the water. Part of this energy is expended in wave making, part in eddy making, and part in overcoming the friction of the water in contact with the sides, ends, and bottom of the vessel. In order to reduce these various forms of resistance as much as possible, it is desirable to change the form and reduce the length of the stream lines. This consideration naturally leads to the sharpening of the bow and the tapering of the stern of the vessel, as shown in Fig. 10 (a), and a further development is to make the outline a smooth curve, as shown in Fig. 10 (6). For similar reasons it is natural to round off the lower edges, or, as they are called, the bilges of the vessel, as shown in Fig. 10 (c). These changes, and other similar ones made from time to REQUIREMENTS OF SHIPS 13 time, have resulted in the present ship-shape form of most vessels. The most important of these changes, however, have been made at the ends, and most vessels still retain in their middle portion a form that is prac- tically box shaped. This is particularly true of slow moving vessels, such as tramp steamers, oil tankers, barges, etc. Water Line pointed at ends (a) -Bilges rounded off- (0 FIG. 10. Developments of ship forms. Having given the vessel a ship-shape form, it is now possible to have it move from place to place without such an uneconomical expenditure of energy. Among the first means of propulsion of boats and other small craft were poles, paddles, and oars, and finally, sails. It is also possible to tow one vessel by a tow line from another, or from the banks of a canal. Since the intro- duction of steam, however, and with the increase in size of vessels, the majority of all but the smallest have been propelled by machinery at first through the medium 14 PRACTICAL SHIP PRODUCTION of paddle wheels, and finally, by the more efficient means of screw propellers. (Another means is that of the jet propeller, by which a stream of water is forced outwards from the hull so as to drive the vessel ahead, but this method has never been extensively used). At the present time practically all self-propelled vessels are driven through the water by means of screw propellers mounted on shafts at their sterns. The shafts may be rotated by means of gasoline, kerosene, oil, or other internal combustion motors, by steam engines of the reciprocating type, by steam turbines with or without reduction gearing, or by electric motors. The action of the screw propeller may be compared to that of a screw or threaded bolt. Any motion of rotation of the bolt is accompanied by a corresponding motion of translation along its axis. The surfaces of the blades of a screw propeller are simply portions of the surface of a helix or screw, the difference in the action of the propeller from that of a screw in a solid nut being largely due to the slipping of the propeller in the surrounding water. It is possible to determine in advance what will be the effect of a certain propeller in driving a given vessel through the water, provided the amount of power that will be applied to it be known. When a vessel is to be driven by a screw propeller (or by two or more such propellers) it is therefore a great advantage to be able to know in advance how much power will be required to propel the vessel at the desired speed. This is one of the most important considerations in the design of a ship, especially where speed is an important requirement, since the power required will determine the amount of weight and space that must be devoted to engines, boilers, etc. The method in common use for determining the power required for a given ship is known as the method of comparison. For an explanation of this method, a few simple mechan- ical laws must be considered. Power is the rate at which work is done, and work is measured by the force acting multiplied by the distance through which it acts. In the REQUIREMENTS OF SHIPS 15 case of a ship the force acting must be a force equivalent to the resistance to motion offered by the water through which the ship is driven, the distance being the distance through which the ship moves. If it is desired to design an engine to hoist a given weight at a certain specified speed, the problem is a simple one, since the power required is simply the product of the speed times the weight or force to be overcome. In the case of a ship, however, the problem is not so simple since the resistance offered to the ship's motion is influenced to a considerable extent by the action of the particles of water through which the ship passes. A mathematical calculation of the resistance of a ship, even of the simplest form is a very difficult problem, and with the practically infinite number of different forms that it is possible to give to a ship, the problem becomes still further involved. It has therefore been found more desirable to determine the power required to drive a given ship by the practical method of comparison. For instance, if one ship is to be built the exact duplicate, in all respects, of another ship that has already been built and put into service, then the power of the engines required for the con- templated ship, in order to drive her at the same speed as the completed ship under exactly similar conditions, should be the same. This is the simplest case. If the contem- plated ship is to have the same form and proportions as the completed ship, but is to be either larger or smaller, it is natural to assume that there must be some law by means of which the two ships can be compared so as to deter- mine in advance the power that will be required for the contemplated ship. Let it be assumed that it is proposed to build a ship of exactly the same form and proportions as those of another ship already completed and data regarding the performance of which is available, the length of the proposed ship, however, to be different from that of the completed ship. The two ships are shown in Fig. 11, and calling them ships "No. 1" and "No. 2," as indicated, let it be assumed 16 PRACTICAL SHIP PRODUCTION that " No. 2 " is n times as long as " No. 1." Then referring to Fig. 11, the lengths, beams, and depths of the two ships are as follows: L, nL, B, nB, D, nD, respectively. The area of the rectangle circumscribing ship "No. 1" is B X L, and ship "No. 2" is nB X nL or n*BL. The volume of ship "No. I" is a certain proportion of L X B X D, and the volume of ship "No. 2" is the same proportion of nL X nB X nD, or n*LBD. In other words, the ratio on ships " Nos. 2" and "1 " of corresponding linear measurements is n } of corresponding surface measurements is n 2 , and of corresponding volumetric measurements is n 3 . The volume of water displaced by ship "No. 2" is thus n 3 times as great as that displaced by "No. 1," and consequently, the weight, or, as it is CD !< D >: SHIP NO. 1. Ill SHIP NO. 2. ' FIQ. 11. Similar ships. usually called, the displacement, of "No. 2" is n 3 times that of "No. 1." Displacement of "No. 1" equals W; displacement of "No. 2" equals n*W. The displacement being a weight, is also a force, and therefore should be expressed in the same units as the resistance, which is also a force. Consequently, if R be the resistance of ship "No. 1," the resistance of ship "No. 2" should be n*R. Let the speed of ship "No. 1" be Vi and that of ship "No. 2" be 7 2 . Speed is the distance through which the vessel moves per unit of time, or if ti is the length of time required by ship "No, 1 " to travel forward a distance equal to its own length, and t z the time required by ship "No. 2" to travel forward a distance equal to its own length, then REQUIREMENTS OF SHIPS 17 L^ Vi _ ti_ h 1 F 2 "" nL ~ ti n ~h Let the accelerations of ships "Nos. 1" and "2" be, respectively, <* ly and cc 2 . Acceleration is by definition, rate of increase of velocity; " Assuming that gravity is constant, the masses of ships Nos. 1" and "2" are proportionate to their weights, or MI and M 2 are their respective masses, then Mi W The respective resistances being forces, may be expressed as the products of their respective masses and accelerations; consequently or | = Vn But it has been shown that K 2 ti^n Consequently or This simple equation represents a fact that is very useful to ship designers. It may be expressed in words as follows : When comparing one ship with another simitar ship, for the 18 PRACTICAL SHIP PRODUCTION purpose of determining the resistance at any given speed, the respective speeds of the two ships must be in the same ratio as the square root of the ratio of the linear dimensions of the two ships. When speeds are so taken they are known as corresponding speeds. By similar ships are meant ships having the same geometrical form, all corresponding dimensions having the same ratio, and all weights being similarly distributed and varying as the third power of the linear ratio. For example, if ship "No. 2" is to be four times as long as ship "" No. 1," the speed to be used for ship "No. 1" should be one-half of the speed to be used for ship "No. 2" when making the comparison. Since power is measured by the rate at which work is done, and since work is measured by the product of the force overcoming the resistance multiplied by the distance through which this force acts, the power required for the proposed ship may be determined as follows: Let PI and P 2 be the respective powers of ships "Nos. 1 and 2." The forces of resistance are, respectively, R and n*R. The distances through which these forces act in a unit of time are respectively V\ and F 2 , and since power is work done per unit of time, Pi _ flXFi 1 ~ . JL JL P 2 n*R X V 2 n* \/n " n A P 2 = rPPi which may be expressed in words: The ratio of the powers at corresponding speeds of two similar ships is equal to the % power of the ratio of their linear dimensions. This lawls very useful for comparing ships that are similar. This and the preceding law are merely extensions of the principle of mechanical similitude, the application of which to ships was first demonstrated by Mr. Wm. Froude, who was one of England's most prominent naval architects. They are usually combined and expressed in terms of REQUIREMENTS OF SHIPS 19 resistance instead of power, as Fronde's Law of Comparison, as follows: // two ships are exactly similar, and n is the ratio of their corresponding linear dimensions, then if they be run at speeds proportional to \/n, the ratio of the corresponding resistances will be n z . This law furnishes a means for comparing one ship with another similar ship provided their sizes do not differ to any great extent. If, however, no ship has ever been built that has the same form as the ship being designed, it be- comes necessary to make a model of the proposed ship, the resistance of which model can be readily determined, by experiment, in a large long tank called a model tank, by towing the model and measuring its resistance. If it be attempted to apply the law of comparison directly to the results thus obtained by the model experiments it will be found that a serious error is introduced. The reason for this is that the amount of power required to overcome the resistance caused by friction of the water in contact with the vessel does not follow this law. This is largely due to the fact that the particles of water in contact with the surface of the vessel are dragged along to some extent in the direction of motion so that the fric- tion is relatively less on a long large vessel than on a small short model. It is possible, however, to calculate the frictional re- sistance separately, by using the results that have been tabulated from many experiments on surfaces of different characteristics, lengths, and areas. Thus the law of com- parison can still be applied by making the proper correc- tion for friction resistance. The method is briefly as follows: First, the model is towed, and its total resistance measured and recorded. Second, the surface or friction resistance of the model is calculated and taken from the total resistance, thus giving what is known as the residual resistance of the model. Third, from the residual resistance of the model by means of the law of comparison the cor- responding residual resistance of the ship is calculated. 20 PRACTICAL SHIP PRODUCTION Fourth, the friction resistance of the ship is calculated and added to the residual resistance of the ship, thus giving the total resistance of the ship. Fifth, the power required for the ship is then readily calculated. After a ship has been given proper buoyancy, stability, and means for propulsion, it is still necessary that means be provided for directing her from place to place. 4. STEERING A small boat or canoe can be steered after a fashion by a paddle or by oars, and large vessels may be kept on an Rudder Stock -f Rudder^ post VTiller Rudder^ y Rudder SIDE ELEVATION ^ PLAN FIG. 12. Rudder. approximate course or heading by manipulation of the sails or the propellers (where more than one are provided). In order, however, to keep any moving vessel on a steady course with any degree of accuracy, it is necessary to pro- vide her with arudder. Figure 12 shows a rudder fitted to the stern of a vessel. The rudder is a flat vertical plate, hinged to the stern of the vessel, and capable of being rotated horizontally about its forward edge by means of a lever fitted at its head, called a tiller. As the ship moves ahead, when looking in the direction of her motion, that side of the ship that is to the right hand is called the starboard side, and that to the left, the port side. When it is desired to change the direction of the ship's motion to starboard, the tiller (or helm, as it is some- times called) is moved to port. The rudder is thus brought to starboard and offers a resistance to the particles of REQUIREMENTS OF SHIPS 21 water passing the ship on that side. The resulting pressure throws the ship's stern to port and thus alters her course to starboard. Similarly, if it is desired to change the ship's direction to port, the helm is put to starboard. The tiller on all but very small vessels, is moved by means of some sort of a mechanism usually actuated by power, known as a steering gear. It is customary to fit a wheel, called the steering wheel, at some position well for- ward on the ship, which is connected by suitable ropes, rods, shafting, or other means, to the tiller or to an engine that actuates the tiller. Where a steering engine is attached to the tiller the connections from the steering wheel serve merely to cause the steering engine to function, no power being applied directly to the tiller by the connect- ing gear. On large ships, several different steering wheels may be fitted at different locations, any one of which may be used for steering the ship. The vertical post forming the after part of the ship's stern and supporting the forward edge and axis of the rudder, is called the rudder post. The rudder swings about pintles, which are vertical pins, usually attached to lugs on the rudder, fitting into gudgeons, or bearings in lugs which are usually attached to or form a part of the rudder post. Several different forms of rudders are in common use, the size and shape depending in each case upon the type of ship and her size and speed. War ships are usually fitted with balanced rudders, in which a portion of the area is placed forward of the axis, which is extended below the rudder post for that purpose. Rudders of the ordinary type similar to that shown in Fig. 12 are commonly used for merchant vessels. Rudders of both the balanced and unbalanced type may have many different shapes and sizes. For a ship which must turn rapidly, as in the case of most war ships, a much larger rudder is necessary than for merchant vessels. The principal geometrical requirements of. a vessel to make her suitable as a means for over- water transportation 22 PRACTICAL SHIP PRODUCTION have now been considered. The evolution of a simple log of wood hollowed out, shaped and enlarged into a ship, and then provided with means for propulsion and steering, has been traced. Little or no consideration has, however, yet been given to what was inside of the outer hull or skin of the ship, or to the material of which this hull was constructed. As boats and canoes were increased in size it became necessary to make them structures rather than simple hollowed out carved logs. Structural strength had, then, to be considered. 5. STRENGTH Any floating body is subjected to certain stresses that must be taken care of by the material of which it is con- structed. For a floating body to be of practical use in over-water transportation, as has been seen, it must be hollow. The assembled material of which such a floating body is made up is collectively known as the hull. The hull may be considered as performing two functions : First. To keep out the water, and Second. To withstand the various forces exerted by the pressure of the water and caused by the weight of the structure itself and the other weights that it supports. If the hull is made in one piece, as in the case of a canoe carved from a single log, its thickness must be compara- tively great in order to provide the necessary strength and rigidity. This is shown in Fig. 13 (A), which represents a cross section of such a vessel. If a large enough solid timber could be obtained, even a ship might be considered as so fashioned. Were this hull made of concrete, cast iron, or other such material, the same reasoning would apply, but it can readily be seen that for large vessels the thickness and consequently the weight would be practically prohibitive. The hull may, however, be made to fulfil the two func- tions mentioned above by constructing it as a thin skin or membrane supported inside at suitable intervals by REQUIREMENTS OF SHIPS 23 framing. In Fig. 13 (B) is shown a cross section of such a vessel. Here the outer skin consists of wood planking, comparatively thin, which is supported against the pressure of the water by transverse frames. Longitudinal strength is given by the planking itself, and also by a timber running along the bottom of the centre line, known as a keel. The thicker the planking is made, the nearer will the construc- tion of (B) of Fig. 13 approach that of (A), and consequently the less will be the need for the framing and the smaller and more widely spaced may the frames then be. Con- versely, the thinner the planking is made, the greater will be its need for support from the frames. In rough weather a vessel such as that shown in Fig. 13 is liable to be swamped by waves coming over the top, and FIG. 13. Solid and built-up hulls. therefore this top is commonly covered by a deck or planked surface supported by horizontal framing, usually running athwartships, called deck beams. The planking of the deck, sides, and bottom of the vessel may be considered as a continuous membrane stretched over a frame work consisting of the frames and beams. To these is usually added certain longitudinal framing, inside of the frames, consisting of keelsons, longitudinals, stringers, girders, etc., all of which assist in supporting and reinforcing the planking and furnishing strength and rigidity to the structure as a whole. The most satisfactory material for use in the construction of ships is steel, and owing to its great strength, much less volume needs to be devoted to the hull itself, thus leaving 24 PRACTICAL SHIP PRODUCTION more space available for cargo, passengers, machinery, fuel, etc. The planking shown in Fig. 13 (B) is replaced by thin steel plating, and instead of the massive wooden frames, comparatively small steel bars of various cross sections are used. Strength must be provided for a ship in three ways; 1. Strength for the ship as a whole; 2. Local strength; 3. Strength partaking somewhat of the nature of both 1 and 2. Strength of the Ship as a Whole. In the first case the ship must be considered as a large girder loaded with various weights, some concentrated and some distributed throughout its length and breadth, and supported by the buoyancy or upward pressure of the water, which may vary at all points in the length on account of the under water form of the ship. This girder strength of the ship must be considered both transversely and longitudinally, although for ships as ordinarily constructed, transverse strength is usually greater than longitudinal strength and does not require so much investigation. In addition to the stresses caused by the loading of the vessel and the forces of buoyancy, it is necessary to consider the stresses that are set up when the ship is passing through large waves. These stresses are caused by forces that are both static and dynamic, the former being due to the form of the waves and the latter being due to the motion of the vessel through the waves. It is usually customary when designing a ship, to make an investigation of her girder strength by assuming that she is poised either on the crest or in the trough of a wave equal in length to her own length, and on this assumption to calculate the resulting stresses. For ordinary ships the stresses thus obtained will be greater than those that may be expected to be developed in actual service, and the excess thus allowed for in this calculation, which takes account of static forces only, is assumed to be sufficient to offset the stresses caused by dynamic forces. This assump- REQUIREMENTS OF SHIPS 25 tion is based upon the fact that ordinary sized ships seldom, if ever, encounter such large waves. The upper half of Fig. 14 shows a ship poised in the trough of a wave with a crest at each end. In this case some of the support normally given by the water is taken away from the middle portion of the ship and some is added at each end. The vessel thus has a tendency to droop in the middle. This is called sagging. When the crest of the wave comes at the mid-length of the ship, as shown in the lower half of Fig. 14, the reverse is the case, and the ends tend to droop. This is called hogging. Calculations for longitudinal strength may be made both for the condition in still water and with the ship poised on Sagging Hogging FIG. 14. Sagging and hogging. either the crest or the trough of a wave equal in length to its own length. Without going into great detail, the method pursued may be described as follows : 1. From a general consideration of the proportions and form of the ship and the locations of the large important weights, a decision is reached as to whether the most serious strains experienced will be those of hogging or those of sagging, and the case producing the most serious strains is selected. 2. The surface of a trochoidal wave of the same length as the ship and of a height equal to one-twentieth of its length is applied to the plans of the ship, the position of the wave surface being so adjusted that the volume cut by it from 26 PRACTICAL SHIP PRODUCTION the ship is exactly the same as the immersed volume of the ship when floating in still water. 3. Calculations are then made, by means of which a curve is constructed with the ship's length as a base and with ordinates representing the upward force of buoyancy for each point in the ship's length* These calculations are based upon the principle previously explained, that the upward pressure on a floating body is equal to the weight of the water displaced by that body. 4. On this same base line, from detailed calculations of the weights and locations of the members and various parts that make up the ship and all that she carries, another curve is drawn, each ordinate of which represents of Bending Moments rve of Weight* Curve of Shearing Forces Length of Ship, to Scale Bow Curve of Buoyancy I \Curve of Load FIG. 15. Curves for strength calculation. the weight with which the ship is loaded at the point repre- sented by the corresponding abscissa. These two curves may look something like the curves in Fig. 15, which are marked " curve of buoyancy" and " curve of weights" respectively. These curves are drawn for a ship poised with the centre of its length at the trough of the wave, as will be seen by the general shape of the curve of buoyancy. It will be noted that ordinates representing weights are considered as positive and those representing the forces of buoyancy as negative, since they act in opposite directions. 5. A third curve is obtained by subtracting the ordinates of the buoyancy curve from the corresponding ordinates of the weight curve. This third curve is called the curve REQUIREMENTS OF SHIPS 27 of load, and represents the resultant of the vertical forces of weight and buoyancy at each point. It should be noted that for equilibrium the area of the weight and buoyancy curves must be equal and that the area of the load curve above the horizontal axis must be exactly equal to its area below that axis. 6. By the successive integration of the load curve and its integral curve are obtained the curves of shearing force and bending moment, as shown in the figure. 7. The maximum bending moment and the point at which it occurs are then determined, and calculations for the strength of the ship at this point are made to see that this strength is sufficient. This is done by finding the moment of inertia of this section and calculating the maximum fiber-stress, making use of the ordinary T) 7W beam formula: = ^-* If the stress is found to be y I excessive, the size of some of the members must be in- creased in order to reduce it, and a second calculation made to see that a satisfactory maximum stress has been obtained. A similar method might be pursued in the investigation of the transverse strength of a ship if desired. But this is not usually found to be necessary, as the transverse strength is usually more than ample. In war ships and ships of special type, however, such calculations may have to be made. Transverse strength may also be investigated where special conditions require this to be done, by means of the " Principle of Least Work." Local Strength. Local strength must be provided in special cases to meet special needs. For example, at the bow of the ship there is a tendency for the plating to move in and out when the ship is in a seaway. Such movement, called panting ', is provided against by means of special stiffening, such as ram plates, breast hooks, panting stringers, etc. Other cases where local strength is required are gun and turret foundations, supports for boat cranes and 28 PRACTICAL SHIP PRODUCTION davits, masts, engines, boilers, etc., i.e., heavy concentrated weights or fittings that receive heavy sudden loads or shocks. Strength, Partly for Ship as Whole and Partly Local. It is difficult to make an exact distinction between local strength and strength of the ship as a whole in certain cases. For example, the forces of the rudder and pro- pellers must be transmitted to the whole hull. Also if the vessel is towed or is towing, the deck fittings to which the tow-line is attached must transmit practically the entire stress to the whole ship. The same applies to stresses transmitted, in sailing ships, by the masts, and rigging. In general, it must be remembered that all these stresses must be gradually transmitted from the member receiving the full force, to the remainder of the hull. There should be no sudden break in strength, but as the strength is reduced from its maximum to its minimum, it should be tapered off gradually. Any sudden break in strength causes a point of weakness, and is liable to cause failure in an emergency. This general rule applies to structural design throughout. 6. ENDURANCE The next quality which is of great importance only in the case of seagoing vessels is endurance. If a ship is to be suitable for voyages of any great length she must carry enough coal or other fuel to propel her for the required distances, and, if propelled by steam power, must carry enough fresh water for the boilers, or must be provided with evaporators to convert salt water into fresh water while at sea. She must also have space to carry sufficient food and fresh water for all persons on board during the trip. The amount of space and weight that must be devoted to fuel and other consumable weights depends upon the service- for which the ship is intended. It should always be carefully considered in the design. By far the largest percentage of these weights is that required for fuel. In REQUIREMENTS OF SHIPS 29 this connection it is very necessary to know whether the vessel can secure fuel at each of her terminal ports, or ports of call, or whether she can coal (or oil) only at her home port. It is also usually important that she does not carry an unnecessary amount of fuel since this cuts down the space available for cargo, passengers, and other uses, and therefore limits the utility of the ship. In designing a ship, after the type and size of the engines and boilers have been determined, and the kind of fuel that is to be used has been decided upon, the amount of space that must be assigned to fuel is calculated from data on the fuel consumption that may be expected and the length of the greatest voyage that it is intended the ship shall be capable of making. Data regarding the probable fuel consumption is obtained from the results of past experience in other vessels. 7. UTILITY Although a vessel may have all the qualifications that have already been described, there is still one more that must be provided. Arrangements must be made to make the vessel suitable for the use to which she is to be put. These arrangements include the following: 1. Living Accommodations for Officers and Crew. The complement of the ship, which includes the men charged with the care and operation of the engines, boilers, and other auxiliary machinery, the steering and navigating of the ship, her cleanliness, care, and upkeep, and the other duties necessary for her proper maintenance and operation, must be suitably sheltered and fed. This requires sleeping accommodations, eating and toilet facilities, and more or less elaborate systems of lighting, heating, ventilation, plumbing, and refrigeration. 2. Space for Carrying Passengers, or Cargo, or Fuel, or Space Necessary for any Special Service for which the Vessel is to be Used. Special staterooms, dining saloons, galleys, etc., are necessary for passenger ships in addition 30 PRACTICAL SHIP PRODUCTION to those necessary for a ship's complement, and must also have even more elaborate lighting, heating, ventilating, and similar systems than those provided for the crew. For vessels designed to carry cargo, large holds and other cargo spaces fitted with special large openings, and derricks and hoisting engines for loading and unloading cargo must be provided. In case the cargo is of a special type, such as oil or other liquids carried in bulk, or fruits, meats, or other perishable goods, special arrangements must be made for stowing and handling it. In the case of warships, arrangements must be made for turrets, barbettes, guns, torpedoes, mines, armor, maga- zines, etc., together with the necessary machinery for controlling, operating and supplying the battery. 3. Auxiliary Requirements. All ships must have means for anchoring and mooring, boats, and means for hoisting and lowering them, gangways, ladders, and other means for ingress and egress, means for signalling or communication with the shore or with other ships, means for pumping water from one compartment to another, protection against fire, sails (to some extent, at least, in case of break- down of the main engines), special navigational apparatus, various means for interior communication, and many other special arrangements too numerous to mention. All of these arrangements affecting the utility of the ship vary with her size and the service for which she is designed, but all are very important and must be carefully considered during the course of the design. RECAPITULATION The principal requirements of all ships are: 1. Buoyancy. 2. Stability. 3. Propulsion. 4. Steering. 5. Strength. 6. Endurance. 7. Utility. CHAPTER II GENERAL DESCRIPTION OF SHIPS 1. FORM The Lines. The outer form of a ship is a curved undevel- opable surface. It can be represented geometrically by fixing the locations in space of points on this surface. The greater the number of points taken the more accurately will the surface be determined. For convenience it is customary to locate these points by means of co-ordinates or "offsets" measured at right angles to the following three planes: 1. A vertical longitudinal plane dividing the ship into two symmetrical halves. Ordinates perpendicular to this plane are called half -breadths. 2. A horizontal plane parallel to the surface of the water and intersecting the first plane in a line called the base line. Ordinates measured vertically up from this horizontal plane are called heights. 3. A plane at right angles to each of the first two planes, and for convenience often taken at the mid-length of the ship. The intersection of this plane with the ship's surface is called the midship section or dead flat. Ordinates perpendicular to this plane are thus measured longitudi- nally and are usually expressed as distances forward or aft of the midship section, depending upon whether they are measured toward the bow or toward the stern of the ship. (The midship section is usually designated by the symbol 38C). If the surface of the ship be considered as cut by planes parallel to each of these three reference planes, then the intersections of the planes will be curved lines which may be projected upon the three reference planes, the projection of any particular intersection appearing as a 31 32 PRACTICAL SHIP PRODUCTION straight line on two of the planes and as a curved line on the third. A drawing consisting of such projections is called the lines of the ship, and the ^projections on the first plane make up what is usually called the sheer or profile plan; on the second plane, the 'half -breadth plan; and on the third, the body plan. Sueh a set of lines is shown in Fig. 16. Intersections of the ship's surface by planes parallel to the third plane are called cross sections. These are marked in Fig. 16 by numbers 2 to 10 inclusive. Intersections of the surface by planes parallel to the second plane are called water lines. These are marked in Fig. 16: W. L. "A", L. W.I,, 2 W. L., 3 W. L., 4 W. L. "L. W. L." is the usual abbreviation for load water line, which is the intersection of the surface of the ship by the plane of the surface of the water when the ship is floating with her designed load on board and is perfectly upright in the water, or with the base line horizontal. Intersections of the surface of the ship by planes parallel to the first plane are called bow and buttock lines or simply buttocks. One buttock only is shown in Fig. 16, but several are usually drawn. For convenience in drawing the lines it is also customary to take one or more intersections of the ship's surface by a plane or planes perpendicular to the midship section plane but at an angle with each of the other two. Such intersections are called diagonals, and appear as straight lines in only one plan and as curves in the other two. A diagonal is usually shown projected in the sheer plan, but expanded, or in its true shape, in the half -breadth plan. One diagonal only (the bilge diagonal) is shown in Fig. 16. Certain lines of a ship's form (of which only one the line of the deck at side is shown in Fig. 16) have curvature in all three dimensions and therefore appear as curves in all three plans. The drawing of the lines of a ship is simply a problem of descriptive geometry. All offsets must appear in their GENERAL DESCRIPTION Of SHIPS 33 34 PRACTICAL SHIP PRODUCTION actual length in two of the three plans. For example, all breadths can be measured in both the half-breadth and the body plan. (They appear as points in the sheer plan.) During the process of drawing the lines it is necessary that all such offsets be made to agree, in each case, in the two plans, and at the same time the curves or sections of the ship's form that are determined by these offsets must be regular smooth curves. The process of thus adjusting the various offsets is called fairing the lines, and when it has been properly done, all the curves will be smooth and regular and are then said to be fair. A surface or curve is thus spoken of as "fair" when it has a smooth curvature free from humps or hollows. Definitions Applying to a Ship's Form. There are certain terms, dimensions, and names of parts that apply to 'ships' forms in particular. These are used frequently both during the design and construction of ships, and a knowledge of their meaning is essential to all shipbuilders. A few of these have already been explained in the preceding pages and some are indicated in the lines of the ship represented in Fig. 16, but in order to make the subject of form complete they will be included in the definitions given below: 1. Directions on a Ship. The end of a ship that cuts the water when a ship moves ahead is called the bow. The other end is called the stern. The bow and stern form the extremities of the ship's length. Distances measured in the general direction between bow and stern are said to be measured in a fore and aft direction, or longitudinally. Distances measured at right angles to this direction, and horizontally, are said to be measured athwartships, transversely, or in an athwartship or transverse direction. The term amidships means at or near the centre of the ship, considered either in the fore and aft or in the athwartship direction. Inboard means toward the centre, and outboard toward the side of the ship. The terms fore and forward apply to parts of the ship that are, in general, at, near, or toward the bow, while the terms aft and after apply to parts, in general, at, near, or toward the stern. For ex- GENERAL DESCRIPTION OF SHIPS 35 ample, the fore-body of the ship is the portion of her form that is forward of the midship section, or, if the ship has a constant cross section for a portion of her length amidships, that portion forward of this constant cross section. Simi T larly, the afterbody is the portion of the ship's form aft of this parallel middle body, or of the midship section in case no portion of her length is parallel sided. When looking from the stern toward the bow, that side of the ship that is to the right hand is called the starboard side and that to the left hand, the port side. When steaming at night, ships usually show a green light on the starboard side and a red (port colored) light on the port side. Distances measured vertically are spoken of as heights or depths. When speak- ing of a part of a ship under any point of reference it is said to be below instead of using the landsman's "down stairs." The term on deck usually refers to locations on the highest or upper deck, the decks being nearly (but not quite) horizontal surfaces corresponding to the floors of a building on shore. 2. Reference Lines and Planes. The keel line is the line of the fore and aft member running along the centre line of the ship at its lowest part. The base line is the inter- section of the central longitudinal vertical plane of the ship with a horizontal plane through the top of the keel at the midship section (in some cases the keel line and the base line are the same). The load water line (usually marked L. W. L.) is the term applied to the line in the lines of the ship which represents the intersection of the ship's form with the plane of the surface of the water when the ship is floating with her designed load on board. This term is somewhat of a misnomer since it is really applied to the load water plane rather than to the load water line. It is sometimes applied to the trace of the plane of the water with the central vertical plane, and sometimes to the trace of the water surface plane with the transverse plane at the mid-length of the ship, and also to the projection of the intersection of the water surface with the ship's surface on the horizontal plane. The 36 PRACTICAL SHIP PRODUCTION forward perpendicular is the vertical line through the intersection of the forward side of the stem with the load water plane. The after perpendicular is the vertical line through the intersection of the after side of the stern post with the load water plane. The midship section (55!) is the intersection of the ship's form with a transverse ver- tical plane midway between the forward and the after perpendiculars. NOTE. These above-mentioned lines and planes are shown in Fig. 16, in which they should be carefully noted. 3. Molded Dimensions. The molded surface of a ship is the surface passing through the outer edges of all the framing or the inner surface of the planking or plating which forms the outer skin. It is the surface represented by the lines. The length between perpendiculars (L. B. P.) is the distance between the forward and the after per- pendiculars. The length over all (L. O. A.) is the length between the extreme forward and after points of the ship measured parallel to the base line. The molded breadth is the maximum transverse breadth of the molded surface at the midship section. The molded depth is the vertical distance from the base line to the line of the main deck at side at the midship section. The draft is the vertical distance between the bottom of the keel and the water line at which the ship is considered as floating. When measured at the forward end of the ship the draft is called the draft forward, and when measured aft, is called the draft aft. The arithmetical mean of the draft forward and the draft aft is called the mean draft. The difference between the draft forward and the draft aft is called the trim. When the draft aft is greater than the draft forward, the vessel is said to trim by the stern. When the reverse is the case she is said to trim by the bow. When a ship is designed to float normally with a greater draft aft than forward, the difference in the two drafts is called the drag. Load draft is the draft of the ship when floating at the load water line. Extreme draft is the vertical dis- tance of the lowest point of the ship below the surface of GENERAL DESCRIPTION OF SHIPS 37 the water. Freeboard is the height of the ship above the water's surface, or it is the difference between the moulded depth and the draft. Rise of bottom, or rise of floor, or dead rise are all expressions meaning the amount that the straight portion of the bottom rises in the half-beam of the ship. Tumble home is the amount that the side of -the ship is nearer to the centre line at the top than at the level of greatest width. Flare is the opposite of tumble home. (Cross section No. 2 in Fig. 16 has a flare while No. 5 has a tumble home.) Camber (also called crown or round up) is the distance that the centre of the surface of a deck is above its side. Instead of being flat plane surfaces decks usually are curved surfaces of such form that a transverse vertical section will be a curve higher at the centre than at the sides. This transverse curvature is called the camber and is usually expressed as the distance that the arc is above the chord for a given beam. (See Fig. 17.) Sheer is the term applied to the fore and aft curvature of a deck. Decks usually have a longitudinal curvature as well as a transverse curvature, but in this case the ends are higher than the centre. (Note sheer of deck at side in Figs. 16 and 17.) NOTE. The various terms above described are illus- trated in Fig. 16, in which they should be carefully noted. 4. Terms Referring to Form. A few of the most com- monly used terms referring to form of ships are illustrated in Fig. 17, and are defined below. The entrance is the forward under water portion of the ship at and near the bow, which enters the water first as the ship moves ahead. The run is the portion of the ship's form under water at and near the stern which last leaves the water as the ship moves ahead. The stem is the forward edge of the bow which cuts the water when the ship moves ahead. The stern post is the vertical post at the after end of the under water portion of the ship. The bottom is the flat or nearly flat portion of the ship's surface extending out- board on each side from the keel and usually sloping slightly upward. The term " bottom" is also applied, in a general 38 PRACTICAL SHIP PRODUCTION GENERAL DESCRIPTION OF SHIPS 39 sense, to all of the ship's surface below the water line. The sides are the vertical or nearly vertical portions of the ship's surface. Bilge is the term applied to the curved portion of the ship's surface between bottom and side. This is also sometimes called the turn of the bilge. Fore foot is the term applied to the after lower end of the stem or the part of the stem that connects with the keel. Dead wood is a term applied to the portion of the hull at the junction of the stern and stern post with the keel. The boss is the curved swelling portion of the ship's surface around the propeller shaft or shafts. Knuckle, in general, is the term applied to any line forming the intersection of two curved surfaces, and in particular, to the intersection of the upper nearly vertical portion of the ship's surface above water at the extreme stern with the lower more sloping portion of the stern. Quarter is the curved portion of the ship on either side at the extreme stern. Bow (besides meaning the forward end of the ship) is applied to the curved forward portion of the ship on either side of the stem. Bulwarks is that portion of the ship's surface between the rail and the highest complete deck, forming an inclosure or railing around the perimeter of that deck. Rail is the upper edge of the bulwarks. Counter is the term applied to that portion of the ship's surface between the knuckle and the water line near the stern. The rudder post is the vertical post at the stern to which is hinged the rudder. In sailing ships or ships with twin or quadruple screw propellers it is also the stern post. Propeller post is the vertical post at the stern of a single or triple screw vessel through which passes the shaft of the centre propeller. 5. Coefficients of Form. The form of a ship is deter- mined from a number of considerations. First the volume of the under water form must be sufficient to displace an amount of water equal in weight to the total weight of the ship and all that she carries. Then in order to reduce resistance and to provide a good run of water to the pro- pellers the entrance and run must be tapered. Also, the form must be so proportioned as to give the requisite sta- 40 PRACTICAL SHIP PRODUCTION bility. In some cases the draft is limited by the depth of the waters through which the ship must pass. These various requirements are usually somewhat conflicting, and the final determination of the form of the ship is more or less in the nature of a compromise. For example, if in an endeavor to reduce resistance, the ship's form be made too narrow and fine or sharp, sufficient stability may not be obtained. In providing sufficient volume to give the desired displacement the lines may be made so full or " bulging" as to give an unduly high resistance. It will be found that certain classes of vessels have forms that are very nearly the same, and as large numbers of such ships have already been built and put into service it is possible to compare these with contemplated ships. For this purpose it is convenient to refer to certain coeffi- cients and ratios, among the most common of which are the following: block coefficient of fineness, load water-line coefficient, midship section coefficient, longitudinal pris- matic coefficient, vertical prismatic coefficient, ratio of length to beam, ratio of beam to draft. The block coefficient of fineness (usually called simply the block coefficient) is the ratio of the under water volume of the ship to the volume of the circumscribing rectangular parallelepiped, or the rectangular solid of the same length as the L. W. L. and with width equal to the ship's beam and depth equal to the ship's draft. The load water-line coefficient is the ratio of the area of the load water line to the circumscribing rectangle. The midship section coef- ficient is the ratio of the area of that portion of the mid- ship section which lies below the load water line to the area of the circumscribing rectangle. The longitudinal prismatic coefficient is the ratio of the under water volume of the ship to the volume of a cylinder having for length the length of the L. W. L. and for a base the immersed mid- ship section of the ship. The vertical prismatic coefficient is the ratio of the under water volume of the ship to the volume of a cylinder having for height the draft of the ship, and for base the area of the load water line. The terms ratio GENERAL DESCRIPTION OF SHIPS 41 of length to beam and ratio of beam to draft are self- explanatory. A knowledge of these various coefficients gives a general idea of the form and type of the vessel's hull. If the value of the coefficient is high, the lines are said to be full, and if relatively low, the lines are said to be fine. The ratio of length to beam is an index of the fineness of the ship longitudinally, the greater this ratio being, the greater being the fineness and consequently the speed that can be obtained, other things being unchanged. The ratio of beam to draft is, in general, an index of the transverse stability. As an example of the variation in values of the block coefficient in different classes of ships it may be noted that, roughly, these are: Slow cargo vessels 80 Ordinary cargo vessels 75 Sailing vessels 70 Older battleships 65 Later battleships 60 Mail and passenger steamers 60 Cruisers 55 Fast cruisers 50 Destroyers 45 Steam yachts 40 2. GENERAL ARRANGEMENT The lines of a ship determine her geometrical form or molded surface. The ship is actually built by providing a certain frame work, all the outer points of which lie in this molded surface. Over this frame work and attached to it is then fitted a complete envelope of plating or planking which forms the "skin" of the ship, keeps out the water, and assists in furnishing strength. The inner surface of the plating or planking therefore coincides with the outer surface of the frames, or molded surface. The framing is, of course, the important part of the ship and furnishes the necessary structural strength. Using 42 PRACTICAL SHIP PRODUCTION the term, in a general sense, the framing may be said to consist of all the principal members of the ship except the shell. The framing and shell with their various connections are collectively known as the hull of the ship. The principal parts of the hull of every ship are designed to serve, in general, the same purposes, whether the ship be wood, iron, steel, concrete, or a combination of any or all of these. It will therefore be sufficient, in discussing these parts, to consider only the modern steel ship, which repre- sents by far the most common type at the present time. The corresponding members of ships built of other materials perform similar functions, and can be readily compared with those of the steel ship. The general interior arrangement of a typical steel cargo carrying steamer is shown in Fig. 18, which represents a longitudinal centre line section of such a ship. In order to give a general idea of the interior arrangement of all ships the various subdivisions, parts and fittings of this ship will be briefly described. Running longitudinally along the centre of the bottom is the keel, which is connected at its forward end to the stem, a heavy cast or forged steel bar or post bent to the shape shown and extending nearly vertically to the highest point of the bow. At its after end the keel is con- nected to another heavy steel member, usually a casting, called the stern-post or stern-frame, which extends up to the counter. This forms the after end of the ship, and to it is secured the stern framing and the after plating of the shell. The shell plating is supported by frames distributed throughout the length of the ship at regular intervals so as to give it sufficient support. At the bow the shell plating is attached to the stem, and at the stern to the stern post. The transverse frames are given support against fore and aft movement by longitudinal framing running along their inner edges so that the framing of the ship really consists of a net work of fore and aft and transverse members crossing each other approximately at right angles. All of this framing is in turn further supported by the decks and bulkheads, which are described below. GENERAL DESCRIPTION OF SHIPS 43 Is. !* S 11 IE gg ! 44 PRACTICAL SHIP PRODUCTION The upper portion of the main hull is closed in by a com- plete deck which, in Fig. 18, is marked shelter deck. This is the highest complete exposed deck and is often spoken of as the weather deck. As it is usually the principal strength deck, it is often also called the main deck. Sometimes it is called the spar deck, a term derived from its proximity to the masts and spars. This deck consists of a slightly curved and approximately horizontal surface under which are fitted heavy steel beams to the top of which is fastened the deck plating. Below the shelter deck and running parallel to it is another deck called the upper deck, and below that and also parallel to it and to the shelter deck is the second deck. The space between the shelter and upper decks is called the upper 'tween deck, and between the upper and second decks the lower 'tween deck. Decks are usually fitted with a vertical distance between adjacent decks of from six to eight feet. They are given various names depending upon the type of the ship in which fitted. They corre- spond to the floors of a building on shore, and serve to subdivide the space in the ship so that it can be conveniently utilized. They also contribute to the strength of the hull by furnishing a certain amount of both longitudinal and transverse stiffness, and also limit the amount of volume that may be flooded in case the shell plating is punctured. In ordinary sized cargo vessels it is not usual to find more than two 'tween decks. The volume of the hull is further subdivided by means of transverse and longitudinal bulkheads, or partitions, which correspond to the walls of a building. These are flat plated surfaces stiffened by means of vertical bars called bulkhead stiff eners. The transverse bulkheads, as well as dividing the volume of the hull up into separate compartments, serve to furnish transverse strength and to transmit the forces set up by the various weights carried in the ship to the lower portion of the hull. In case of damage to the shell plating below the water line, they serve to limit the amount of GENERAL DESCRIPTION OF SHIPS 45 space in the ship that may be flooded, and are made espe- cially strong for this purpose. It will be noted in Fig. 18 that the transverse bulkheads separate the following compartments: Fore peak tank, No. 1 hold, No. 2 hold, No. 3 hold, coal bunker, boiler room, engine room, No. 4 hold, No. 5 hold, and after peak tank. Longitudinal bulkheads (which are not indicated in the figure) are fitted mainly for purposes of subdivision, being limited in length so that they contribute very little to the longitudinal strength of the ship. The forward and after peak tanks are large compartments located at the extreme ends of the ship just above the bottom. They are connected by suitable piping so that they can be readily filled or emptied of water. They can thus be used for trimming the ship, which is the term applied to the process of raising or lowering one end or the other of the ship. A considerable weight of water can be put into either of these tanks, which, owing to its location at the extreme end of the ship, has a great leverage resulting in deeper immersion of that end. These compartments are also sometimes called the forward and after trimming tanks. The bulkhead at the after end of the fore peak tank is sometimes called a collision bulkhead, since this bulkhead, in the event of damage caused by the ship's running into another ship or obstacle, would prevent water from entering the remainder of the hull. The holds (Nos. 1, 2, 3, 4 and 5, in Fig. 18) are large spaces used for carrying cargo. They extend completely across the ship to the shell plating on each side and up to the second deck. In order to load cargo into the holds and 'tween deck spaces there are provided large rectangular openings in the decks called cargo hatches. The edges of these openings are fitted with vertical plate boundaries called coamings, and covers are provided to fit in these coamings. After a hold has been loaded with cargo the covers are put in place and the loading of the 'tween deck space above can be proceeded with. 46 PRACTICAL SHIP PRODUCTION The remainder of the main portion of the space in the hull is devoted to the requirements of propulsion, there being provided, as shown in Fig. 18, an engine room, boiler room, and coal bunkers. In the engine room are located the main engines, condensers, pumps, and other auxiliary machinery, the engines being connected to the propellers at the stern of the ship by longitudinal shafts. These shafts pass through shaft tunnels, which are long water-tight compartments completely closed in by steel plating so as to be entirely independent of the holds through which they pass. The after end is connected to the weather deck by means of a vertical passage, or trunk, which serves both as a ventilator and as a means for escape for the engine room force in case of emergency. A large vertical inclosure, or trunk, extends from the engine room up to the weather deck where it terminates in a large hatch covered by a skylight. This trunk per- mits large machinery parts to be removed from the engine room and furnishes light and ventilation. The boiler room is located just forward of the engine room and, like the latter, is continued to the weather deck in the form of an enclosure through which passes the uptake, a large duct which connects the boilers to the smokestack. In addition to the boilers this compartment usually contains certain pumps and auxiliaries. The coal bunkers are large compartments used for the stowage of sufficient coal for the longest voyages which it is designed the ship shall make. They are fitted with hatches similar to the cargo hatches, by means of which the coal is dumped into them. It will be noted that No. 3 hold, when not desired for cargo, can be utilized as a coal bunker. Coal bunkers are also located outboard abreast the engine and boiler rooms, on both sides, being separated from them by longitudinal bulkheads. (These are not shown in Fig. 18.) The amount of space devoted in cargo vessels to engines, boilers, and fuel is much smaller than in some other types of ships, since cargo vessels usually cruise at comparatively GENERAL DESCRIPTION OF SHIPS 47 low speeds, and therefore do not require the power and do not have the high fuel consumption that is necessary for high-speed vessels. The holds and 'tween decks are usually numbered con- secutively from forward to aft, the 'tween deck numbers corresponding to the holds directly underneath them. The ship shown in Fig. 18 is fitted with an inner bottom extending for the full length between the fore and after peak tanks: This inner bottom runs approximately parallel to the outer bottom at a distance of about four feet above it, extending to the turn of the bilge on each side where it curves down and joins the outer bottom thus forming a separate double bottom to the ship. This double bottom is divided up into a number of double bottom tanks by means of partitions located directly underneath the trans- verse bulkheads, as shown. These tanks are used for carrying water as ballast when the ship is light or without cargo, and some of them for reserve feed water for the boilers, being suitably connected with piping for filling and emptying. The inner bottom, which forms the upper boundary of these tanks, is often called the tank top. When a cargo ship has no cargo on board, the double bottom tanks must be filled in order to give her sufficient stability, and when in this condition she is said to be in ballast. In order that the ship may be anchored when it is not convenient for her to go alongside of a dock she is provided with two or more anchors shackled to the ends of chain cables. The chain cables pass from the anchors through large passages through the bows of the ship called hawse pipes and over a specially shaped drum of the anchor windlass and down through chain pipes into a large com- partment located just aft of the fore peak tank called the chain locker. The steering engine which actuates the tiller is located in a special compartment just above the rudder at the extreme after end of the shelter deck, called the steering engine room. 48 PRACTICAL SHIP PRODUCTION The extreme forward and after portions of the hull above the peak tanks are utilized for storerooms and living spaces for the crew (called crew's quarters). Quarters for some of the crew are also provided just forward of the steering engine room and also abreast of the engine room and uptake trunks amidships on the shelter deck. The galley (kitchen) and crew's mess room (dining room) are also located amidships on the weather deck, as shown, all of these compartments being inclosed in a deck house formed by continuing the sides of the ship up for a portion of the length and decking over the top. This deck is called the boat deck, since it is utilized for the stowage of the ship's boats. There is also installed on the boat deck the radio room which contains the radio instruments and sleeping accommodations for the radio operators. Just aft of the hatch leading to No. 3 hold is a structure extending up for four deck levels, which consists of officers' staterooms and mess room on two levels, with the captain's quarters above these, and the bridge and chart house on top. The bridge is a semi-enclosed platform extending all the way across the ship and so arranged as to give a good view all around the horizon. It is from the bridge that the ship is controlled and steered, there being located there the steering wheel, compass, and various connections to the engine room and other parts of the ship. The chart house is a small house located just off the bridge for use in plotting the course of the ship on the chart and doing other work in connection with navigation which must be done in a sheltered position. The captain's quarters are directly under the bridge in order that he may have access thereto with the least possible delay in case of an emergency. Two masts are installed as shown (the foremast and mainmast), these serving as supports for the aerial of the radio apparatus, for use in hoisting signals, to provide stations high above the water for lookouts, and as a support for the booms used in loading and unloading cargo. These masts could also be used, in case the machinery should break down, to spread sails. Special derrick posts are GENERAL DESCRIPTION OF SHIPS 49 also installed, as shown, for cargo booms serving hatches not located convenient to masts. Steam winches are located at various points on the weather deck for furnishing power for the gear of the cargo booms and other hoisting arrangements. Air is supplied to the various compartments of the ship by means of special ventilating ducts fitted at their upper ends with hoods or cowls and extending down to the com- partments to which they are to supply air. As has been noted, the after ventilating trunk serves also as an escape hatch from the shaft tunnel. The foregoing brief description will serve to give a general idea of the subdivision and arrangement of the various spaces of this particular type of ship. There is, however, considerable latitude in the arrangement of different types of ships which varies with the purposes for which designed. For example, the amount of space necessary for engines and boilers in a vessel designed to make 25 knots speed would be a very appreciable proportion of her total volume, whereas in a slow tramp steamer it is relatively small. In war ships, with their special requirements of guns, torpedoes, magazines, armor, etc., the interior of the hull is much more cut up than that of the ship shown in Fig. 18. All war ships are much more minutely subdivided in order to limit the damage which may be caused by shell fire or torpedo or mine explosions. Much of the space used for cargo in Fig. 18, would in the case of a passenger vessel be utilized for state rooms, dining saloons, lounges, and other conveniences for the passengers. Vessels de- signed for carrying fuel oil, gasoline, molasses, or other fluids in bulk have the holds replaced by large tanks, extending to the weather deck and terminated by expansion trunks to permit of changes in volume due to variation in temperature. Many of the features illustrated in Fig. 18 are, how- ever, common to practically all large modern steel ships. These include the double bottom, peak tanks, bulkheads, decks, steering gear, anchor gear, masts, ventilation, 50 PRACTICAL SHIP PRODUCTION bridge, engine and boiler rooms, shaft tunnels, and numer- ous other parts. The interior arrangement of any ship must be governed both by considerations of convenience (as in the case of a building on shore) and by requirements of buoyancy and stability, which make it necessary to have the weights of the ship so located as to fulfil the conditions that have been discussed in Chapter I. 3. TYPES OF SHIPS Ships may be classified in several different ways, such as with reference to the material of which constructed, the purpose for which used, the speed, etc. 1. Ships Classified with Reference to Materials of Hulls: (a) Wood. (6) Composite. (c) Iron. (d) Sheathed (e) Steel (bronze, etc.). (/) Concrete. (a) Wooden Ships. The first ships of importance were constructed almost entirely of wood, which formed the keels, keelsons, stringers, knees, beams, planking, floor- ing, ceiling, etc. For many years practically all ships were built of wood, and it was not until well into the nineteenth century that iron appeared as a shipbuilding material. The building of wooden ships thus became more or less of an art, and all skilled shipbuilders were spoken of as shipwrights, a term meaning literally " builders of ships," but now applied only to the workmen who fit and install the wood decks and other wooden parts form- ing integral portions of the hulls. These wooden ships were monuments to the shipwright's skill, and performed excellent service for many years, but as the demand for increase in size appeared, and with the introduction of the use of iron, it was gradually found advisable almost entirely to abandon the use of wood for hull construction. GENERAL DESCRIPTION OF SHIPS 51 The reason for this is that it is very difficult to fasten the various parts of a wooden ship together so as to prevent a certain amount of slipping or sliding of each part on its neighbor. These strains becoming accumulative, in a large ship, would cause such a great total distortion as to make the use of wood for ships of such size practically prohibitive. Very few wooden ships have ever been built to lengths of over 300 feet, while the most successful ones have been little over 200 feet long. When it is remembered that ships are now built with lengths approximating 1000 feet, the limitations of wooden ships are readily seen. Nevertheless, for small vessels designed to operate along the coast or in protected waters wood is a very satis- factory material owing to its cheapness and the ease with which it can be worked. (b) Composite Ships. The difficulties mentioned in con- nection with wooden ships can be considerably overcome by introducing a certain amount of metal into the con- struction. In fact, modern wooden ships of any size usually have certain steel strappings and reinforcing members. When the entire framing of a ship is built of iron, steel, or other metal, but the outer skin is still of wood planking, she is known as a composite ship. Such vessels have the advantage of not requiring dry- docking for purposes of cleaning the bottom so frequently. (c) Iron Ships. Iron came into general use for ships' hulls during the latter part of the first half of the nineteenth century. The principles of iron shipbuilding were, in general, the same as those now applied to steel, the sizes of the various members, however, being necessarily greater for iron on account of its lower strength. Iron is prac- tically never used, however, for shipbuilding at the present time except for certain forgings and for rivets for some merchant ships. Iron has a greater resistance to corrosion than steel, and it is not unusual to find old iron vessels, built perhaps half a century ago, still in an excellent state of preservation. 52 PRACTICAL SHIP PRODUCTION (d) Sheathed Ships. In order to protect the under water hull of an iron or steel ship from fouling, due to various marine growths, it is sometimes customary to sheathe it with wood over the iron or steel plating below the water line, and to cover the wood with sheets of copper secured to the wood with copper nails. This necessitates the use of bronze for the stem, stern posts, struts, etc., in order to prevent galvanic action, and great care must be exercised to see that the copper on the outside of the wood sheathing is thoroughly insulated from the steel or iron shell plating inside. Sheathed ships are stronger than composite ships but of more expensive construction. They are used principally in tropical waters where marine growths are excessive, in order to avoid frequent dry- dockings. (Dry-docking consists in landing the vessel in a large basin, or dry-dock, from which the water can be pumped out so as to render the under water portion of the vessel accessible for cleaning and repairs.) (e) Steel Ships. The steel ship is the type most com- monly built at the present time and has so many advan- tages over all other types that it is practically universally recognized as the modern ship. Wood and concrete ship construction have recently received a great impetus, but this is admitted to be due rather to the suddenly increased need for overseas transportation, which renders the con- struction of all types of ships advisable, rather than to any superiority of these ships over steel ships. The principal advantage claimed for wood and concrete ships at the present time is that their construction will supple- ment rather than replace steel construction, and can be carried on at the same time by utilizing other materials and a different class of labor. It is practically certain that steel ships will be the standard for many years to come and that by far the greatest proportion of ships constructed will have steel hulls. Recent experiments indicate that a great improvement may be made in the methods of steel ship construction by the substitution of electric welding as a means for fastening the various GENERAL DESCRIPTION OF SHIPS 53 parts together instead of riveting. Yachts and small torpedo vessels are sometimes constructed of bronze instead of steel, but the principles of construction are practically the same as for steel vessels. (f) Concrete Ships. Reinforced concrete has been con- sidered for a number of years as a material for ships, and a number of small craft, barges, etc., have actually been built on this principle, but it is only comparatively re- cently that large vessels designed for overseas service have been built of reinforced concrete. However, the recent great demand for ships of all kinds has resulted in a great deal of attention being paid to the construction of reinforced concrete vessels. The principal obstacles in the way of building ships of this material are the relatively great weight and volume of the material required to obtain the necessary strength, the liability of the material to crack when subjected to stress in a seaway, and the dete- riorating effect of the action of salt water on the concrete. It is claimed by the advocates of concrete ships that these obstacles can be largely overcome and that they are more than offset by the advantages, the principal ones of which are cheapness and speed of production, and the fact that the labor required for their construction can be obtained without drawing on the supply of labor necessary for building steel ships. At the present time concrete ships must still be con- sidered as in an experimental stage, and until they have been built in sufficient numbers and operated satisfactorily for continuous and extended periods of time to demonstrate their practicability, the advisability of laying down large numbers of such vessels is open to some question. 2. Ships Classified with Reference to Purpose for Which Used.- (o) WARSHIPS. (I) Battleships. (II) Cruisers. (III) Gunboats. (IV) Torpedo craft. 54 PRACTICAL SHIP PRODUCTION (V) Mining and mine sweeping vessels. (VI) Submarines. (VII) Auxiliary vessels. (6) MERCHANT SHIPS. (I) Passenger vessels. (II) Cargo vessels. (III) Combined passenger and cargo vessels. (IV) Tugs. (c) SPECIAL TYPES. (I) Yachts, house boats, etc. (II) Salvage and wrecking vessels. (III) Dredges. (IV) Fishing vessels. (V) Surveying vessels. (VI) Fire and water boats. (And numerous other miscellaneous types.) (a) Warships (I) Battleships. The term battleship is applied, in general, to warships designed to take part in fleet actions. It is a more or less elastic term sometimes including moni- tors and small coast defense ships, and some vessels that may also be classified as cruisers. The modern battle- ship represents the standard type of warship, from which other types may be considered as developed. It is the largest, most powerful fighting unit, and far more costly than most other types of warships, so that it is usual to compare the strengths of the various navies of the world in terms of the numbers of first-class modern battleships that they possess. (" Battle cruisers" are also included in this classification.) Modern battleships are often called " super dreadnoughts," being developments of the all-big-gun type of ship of which the British " Dreadnought" was the forerunner. They are characterized by great size, strong offensive and defensive powers, ability to keep the sea in all kinds of weather for prolonged periods of time, and fairly high GENERAL DESCRIPTION OF SHIPS 55 speeds. They are especially designed for great strength and safety in case damaged by shell, torpedo, or mine attack, and consequently have numerous water-tight compartments, armored bulkheads, decks, and special under water protection, and their form differs consid- erably from that of a merchant ship. Great beam must be provided in order to obtain the large displacements required and the necessary stability. The displacements of such ships range between 30,000 and 40,000 tons. The guns carried may be of calibres approximating 16" with armor of corresponding thickness. Very powerful engines are necessary to drive these great ships at the required speeds, which may be 21 knots or greater. (II) Cruisers. Vessels of this class are especially char- acterized by higher speed than battleships. They natu- rally lack in protection what they gain in speed and usu- ally have a much smaller armament than battleships. They are variously subdivided into different classes, such as battle cruisers, armored cruisers, protected cruisers, and scout cruisers or scouts. In general, the purpose of cruisers is to serve as auxiliaries to the main battle fleet, doing convoy and scouting duty, protecting commerce, destroying the enemy's commerce, engaging enemy cruisers, etc. Battle cruisers are high-speed battleships in which armor and, in some cases, armament are sacrificed to speed. They may have speeds ranging between 25 and 30 knots. In some cases they have guns of the same calibre as con- temporary battleships. Owing to their very high speed they may be even larger and longer and may cost more to build than battleships. Armored cruisers are less powerful and less speedy than battle cruisers. The distinction be- tween these two classes is not exact since the battle cruiser is a comparatively recent type and may be correctly called an armored cruiser, whereas the old armored cruisers are considerably smaller and slower than battle cruisers. Protected cruisers are even smaller and less powerful than armored cruisers, and have little or no side armor, being provided merely with a protective deck near the water 56 PRACTICAL SHIP PRODUCTION line. They are designed more for convoy and raiding service and should not take a direct part in fleet action. Scouts are light high-speed vessels designed primarily, as their name implies, for scouting service. They have very little protection, moderate armament, good seaworthiness, and a speed in the neighborhood of 35 knots. The general form of all cruisers resembles that of battleships, the lines, however, being considerably finer. (III) Gunboats. For special service in shallow waters' along coasts or in rivers, small warship's known as gunboats are employed. These are usually 'of special design, depending upon the waters in which they are to operate and may be, or may not be, protected by armor. They usually have displacements of under 1000 tons. Often they are converted yachts. (IV) Torpedo Craft. Formerly small, fast vessels were built for the purpose of carrying and launching torpedoes. These were called torpedo boats. To oppose them larger and faster vessels were built along similar lines called torpedo boat destroyers. The building of torpedo boats, therefore, was gradually abandoned, the duties formerly performed by them being transferred to the destroyers and also to some extent to submarines. Destroyers have been gradually enlarged until they now approach scouts in design and are used somewhat for the same duty. They carry both guns and torpedoes and have no armor, and are given very high speeds, between 30 and 40 knots. Their displacements may be as high as 1000 tons or even more than this. Their principal duties at the present time are to convoy merchant ships and to hunt down and destroy submarines. (V) Mining and Mine-destroying Vessels. These are specially equipped vessels of small size and light draft used for sowing mines and for sweeping and destroying them. (VI) Submarines. Submarines are vessels of special construction which enables them either to run on the surface of the sea or to run submerged. Submerged running is accomplished by flooding specially constructed GENERAL DESCRIPTION OF SHIPS 57 tanks so as to destroy all except a very small amount of the buoyancy, the vessel then being directed downward below the surface of the water by the horizontal thrust of the propellers combined with the action of horizontal rudders or hydroplanes. The hull of a submarine has, in general, a cigar-shaped form and a circular or nearly circular cross section. Propulsion on the surface is usually accomplished by means of internal combustion engines, and when submerged, by means of storage batteries and electric motors. There are two general types of con- struction the single hull type and the double hull type. Submarines range in displacements from two or three hun- dred tons upward some very large " submarine cruisers" having been recently constructed. (VII) Auxiliary Vessels. In order to supply and co- operate with the main fleet of a navy certain special types of ships are necessary. Many of these are practically the same as certain types of merchant ships or are readily convertible from them. These include transports, hos- pital ships, colliers, oil tankers, ammunition ships, sup- ply ships, repair ships, training ships, patrol and dispatch vessels, tugs, and numerous other special types. The primary purpose of all warships is to make war and they are all designed with that principal object in view, so that questions of secondary importance to that must always give way to such characteristics as offensive power, safety and ability to continue to fight even when damaged in action, ability to keep the sea for long periods of time, etc. For these reasons they must be designed and constructed with much more care than merchant vessels. (b) Merchant Ships (I) Passenger Vessels. Passenger vessels usually make voyages on a schedule between the same terminal ports. In other words, they run on the same lines and therefore they are usually called liners. They are usually of large size and fairly high speed. Almost all ships that carry 58 PRACTICAL SHIP PRODUCTION passengers carry also a considerable amount of cargo, so that the number of strictly passenger vessels is very limited. Examples of these are the large fast vessels of the various trans- Atlantic lines. Some of these approxi- mate 1000 feet in length and have gross tonnages of 50,000 or 60,000 with speeds of about 25 knots. (II) Cargo Vessels. This class forms the largest of all vessels afloat and handles the world's commerce. For reasons of economy the speed of cargo vessels is usually between eight and twelve knots, even lower speeds being found in the type known as tramp steamers. The main objects sought in a cargo vessel are carrying capacity and economy of operation. Consequently, the form is made very full and the amount of space devoted to the com- plement, engines, boilers, fuel, and water is kept as low as possible. Such vessels are often parallel sided or of uniform cross section for a considerable portion of their length. The main portion of the hull is taken up with cargo spaces. Some cargo ships are propelled by sails, sailing ships at the present time being, in fact, practi- cally limited to cargo carriers, fishing vessels and yachts. The greater number of cargo vessels are, however, propelled by steam. A particular class of cargo vessels are those known as tankers, which are designed for carrying liquid cargoes in bulk. They are usually constructed on the longitudinal or Isherwood system of framing. (III) Combined Passenger and Cargo Vessels. These comprise vessels having the characteristics of both of the two preceding classes, the amount of space devoted to passengers and cargo varying between wide limits. The passengers are housed in the spaces on the upper decks above the cargo. Among such vessels will usually be found the ships of the various coasting lines. The speed of these ships usually ranges between 10 and 20 knots and their tonnage may be almost any figure from 1000 up to 20,000 or 30,000 tons gross, the design varying to meet the particular needs of the service for which built. GENERAL DESCRIPTION OF SHIPS 59 (IV) Tugs. These are comparatively small vessels used principally in harbors and along the coast for towing other vessels or for assisting in handling them about docks and wharves. Seagoing tugs are usually from 150 to 200 feet long. Harbor tugs are considerably smaller. They are given comparatively powerful engines and must be of rugged construction with propellers designed es- pecially for towing. The form of merchant steamers is, in general, the same in all cases, the lines of the fast ones being, of course, finer, Warship Merchant Vessel Yacht FIG. 19. Types of ships. but 'the general characteristics, such as shape of stem and stern, rudders, etc., being nearly always the same. Fig. 19 shows the general form of the profile of a merchant ship, as compared with that of a war ship, of the battle ship or cruiser type, and a yacht. (c) Special Types The various special classes of vessels, such as yachts, dredging, wrecking, and fishing vessels, etc., are too numer- ous to describe in detail. Each is designed to fulfill a 60 PRACTICAL SHIP PRODUCTION special purpose, and usually varies considerably from the others, even of the same class. 3. Ships Classified with Regard to Speed. There is no exact classification of ships with regard to speed, but it is worth noting that extremely few ships have a speed as high as 35 knots, and that speeds as low as 6 or 7 knots are often found in the case of tramp steamers, small sail- ing ships, vessels towing, etc. A rough classification with regard to speeds is given below: Very high speed (30-35 knots). Destroyers.] Scouts. Fast (25-30 knots). Special mail and passenger steamers. Battle cruisers. Moderately high speed (20-25 knots). Battleships. Fast passenger steamers. Slow cruisers. Good speed (15-20 knots). Passenger steamers. Older battleships. Very fast cargo vessels. Steam yachts. Fair speed (10-15 knots). Faster cargo vessels. Slower passenger vessels. Slower steam yachts. Seagoing tugs (not towing). Slow speed (under 10 knots). Slow cargo vessels. Tramp steamers. Sailing vessels. (A knot is a speed of 6080 feet per hour). GENERAL DESCRIPTION OF SHIPS 61 4. TONNAGE OF SHIPS As has been stated in Chapter I, the weight of any ship floating in water, including all that she carries, must equal the weight of the water that she displaces. This weight is called the displacement of the ship and is usually ex- pressed in tons, of 2240 Ibs. each. It will be noted that the displacement is equal to the weight of the ship plus all that she carries, so that the displacement of any ship is variable and depends upon the cargo and other movable weights that she has on board. The displacement of an ordinary cargo vessel, for example, may be three times as much when she is fully laden as when she is light. For this reason a statement of the displacement of a cargo ship, unless the condition of loading is included, gives only an approximate idea of her size. War ships, such as battleships and cruisers, a large percentage of the weight of which is fixed, have comparatively little variation in displacement, and the tonnage of such ships is usually expressed in terms of their normal displacement. In order to express the size of merchant ships it is usual to refer to their gross and net tonnages. These are both based upon certain volumetric measurements, 100 cu. ft. being reckoned as one ton. " Tonnage" in this case, then, really means volume. The gross tonnage is a measure of the internal capacity of the whole ship. The net tonnage is obtained by deducting, from the gross tonnage, allow- ances made for space occupied by officers and crew and their effects, navigation space, and propelling space. The net tonnage is thus really intended to be a measure of the passenger and cargo carrying, or earning power of the ship. The rules for making these measurements were established by the British Board of Trade and have been adopted by practically all civilized countries. The net tonnage is always less than the gross tonnage and is usually about 63 per cent, of it, the reasons for this being that the rules allow a deduction of 32 per cent, for machinery spaces in the cases of ships of which that space 62 PRACTICAL SHIP PRODUCTION is between 13 and 20 per cent, of the gross tonnage and that the other deductions usually amount to about 5 per cent. The great majority of all tonnage usually conies within this class. The dead weight carrying capacity is expressed in tons of 2240 Ibs., or in the same units as the displacement. It is the difference between the displacement of the ship when light and when fully loaded to the maximum draft allowed by law. In other words, the total dead weight carrying capacity of any ship may be denned as the weight, in long tons, of cargo, fuel, water, stores, officers, crew, passengers and their effects that can be safely carried by that ship. There are therefore at least four different tonnages that may be applied to any ship, each expressing in its own way the size and therefore the usefulness of that ship. For ordinary cargo carrying ships the full load displacement tonnage is about 1^ times the dead weight carrying capacity, about 2K times the gross tonnage and about 3% times the net tonnage. The dead weight carrying capacity is about IK times the gross tonnage, and the net tonnage is roughly % of the gross tonnage. The terms gross and net tonnage and dead weight carrying capacity are not ordinarily used in connection with war ships, which are measured in terms of displace- ment. The term displacement is seldom used to indicate the size of a merchant ship since it varies, for such ships, through a wide range. Yachts are usually measured in the same manner as merchant ships. For purposes of insurance there have been established for many years in the principal maritime countries of the world certain classification societies, all of which publish ordinarily each year a Register of Shipping, which is a large book containing the names of all merchant vessels of the world together with their size, tonnage, ownership, name of builder, date built, and other data. The prin- cipal of these societies is Lloyds, the well-known British society. Another British society is known as the British GENERAL DESCRIPTION OF SHIPS 63 Corporation. In France is the Bureau Veritas, and in the United States the American Bureau of Shipping. These Societies issue various rules under which they will insure ships, and they therefore have a very pronounced influence on the trend of ship design and construction. Vessels are rated by these various societies in accordance with their design, construction, and the care with which they have been kept up, each ship being periodically inspected by the surveyors of the Society and the rating modified, if necessary, as a result of the inspection. Merchant vessels are also classified and their tonnage recorded by the government of the nation of which they fly the flag. The methods of determining the tonnages for this purpose are practically the same as those adopted by the various classification societies. 6. MATERIALS USED IN SHIP CONSTRUCTION The principal material, which is in almost universal use for constructing the hulls of ships, is steel. This is found in the form of forgings, castings, plates, shapes, and rivets. Also in warships certain special treatment steel and face hardened steel for armor is used. Other materials used, though nowhere near to the same extent as steel, include iron, copper, zinc, lead, tin, bronze, brass, and other compositions, wood of all kinds, canvas, cork, asbestos, linoleum, hemp and wire rope, cotton, oakum, rubber, tar, paper, glass, leather, various tilings and deck coverings, cements, enamels and paints. Forgings. Forgings are used for special purposes where great strength is required. Owing to the irregular shapes required for the special large solid parts used in hull con- struction, the forging of which is more or less complicated, and because of the fact that steel castings possessing suffi- cient strength for most purposes can now be obtained, there are very few large forgings used in the hulls of ships. Forgings are used principally for machinery parts, such as crank shafts, propeller shafts, connecting rods, and for 64 PRACTICAL SHIP PRODUCTION rudder stocks. Occasionally the stem and stern posts are forgings. Small forgings are used for certain hull fittings and working parts. Castings. Steel castings are commonly used for the stern frame, stem, stern tubes, rudder frame, propeller struts, machinery bed plates, anchors, hawse pipes, chain pipes, pipe flanges, gun mounts, and various small hull fittings. Various grades of steel are used for different ones of these castings. Plates. Plates are simply rolled sheets of steel of uni- form thickness. They range in thickness from about J" to a trifle over 1". Plates less than J-" thick are generally spoken of as sheets. Very thick plates are used in war ships for protective decks and for armor of sides, turrets, bar- bettes, conning towers, etc., but these are not classed as ordinary ship plates, being made of specially treated steel by special processes. Plates are used for the shell, inner bottom, bulkheads, decks, trunks, coamings and other such parts, and for various floors, brackets, girders, and other structural members. The weight of a cubic foot of steel is approximately 490 pounds, so that a plate 1" thick will weigh about 40.8 pounds per square foot. Plates are commonly specified by weight per square foot, and thus a " twenty pound plate" means one slightly less than Y^" in thickness. (In the case of wrought iron, which weighs 480 pounds per cubic foot, the weight of a plate, per inch of thickness, is almost exactly 40 pounds per square foot.) Shapes. Shapes are rolled steel bars of various special constant cross sections. The shapes most commonly used in ship construction are illustrated in Fig. 20. They are used for various parts of the ship's framing and for connect- ing different plates and other shapes. The angle bar (/ bar}, which is shown in perspective in the upper sketch of Fig. 20, is used for joining two other members that meet at, or nearly at, right angles. The names of the various portions of the angle bar are indicated GENERAL DESCRIPTION OF SHIPS 65 in the figure. When the angle made by the two legs or flanges is not 90 the angle bar (or angle, as it is often called) is said to be beveled. If the angle is greater than 90 it is an open bevel, and, if less, a closed bevel. The same terms apply to the other shapes when so treated. Heel- -Toe ANGLE BAR Bosom Web Upper Flange CHANNEL Web jf Flange BULB ANGLE ^Flange Web'" T-EAR T-BULB Bulb Flange Flange "^ Z-BAR I-BEAM \ Flange FIG. 20. Shipbuilding shapes. Channels, bulb angles and Z-bars are developments of the simple angle bar, as shown. They are used in cases where, in addition to connecting other members, they must also furnish more stiffness or girder strength than would be given by simple angles. This stiffness is supplied by the 66 PRACTICAL SHIP PRODUCTION extra " flange" strength. In some cases sufficient stiffness is furnished by angles with unequal legs in which case the shorter leg acts as one flange and the longer leg serves as both the web and the other flange. The I-beam has the ideal cross section for girder strength but is not much used in ship construction on account of the difficulty of connecting it to other members. The T-bar and T-bulb resemble somewhat the I-beam, and can be more conveniently attached to other members. Shipbuilding shapes are designated by the dimensions of their legs or webs and flanges and their weight per linear foot for example, a "3" X 3" X 6 Ib. angle," a "10" X 3%" X 3%" X 21.8 Ib. channel," etc. These figures are called scantlings. These dimensions and other characteristics of the cross sections are given in hand books published by the various steel companies. They differ slightly for shipbuilding shapes (which are rolled specially) from those for ordinary structural steel as used for bridges, buildings, etc. In addition to the shapes shown in Fig. 20 there are a few others used occasionally in shipbuilding, such as round, square, and flat bars, half rounds (solid and hollow), etc. Rivets. Rivets are small malleable metal members or fastenings, used to connect or tie together the various plates, shapes, forgings and castings of the ship's structure. A rivet consists of a cylindrical shank or body, of circular cross section, terminated at one end in an enlarged portion or head. The other end is formed, when the rivet is driven, into a point. Fig. 21 shows a rivet before being driven, and also the various forms of rivet heads and points ordinarily used in shipbuilding. Rivets are usually made of mild steel, although in some merchant work wrought iron rivets are used. Where high tensile steel plates and shapes are used the rivets connecting them are also made of high tensile steel. For connecting GENERAL DESCRIPTION OF SHIPS 67 the plates and shapes of bronze vessels, bronze rivets are used. A rivet is designated by the diameter of the cylindrical portion, or shank, before being driven. The ordinary sizes are M", %", H", ", H", %", 1", W and 1^". Larger sizes are rarely needed, and, if so, are ordered specially. HEADS ^ i i Countersunk, Countersunk, Button, Raised Flat Con PAN-HEAD RIVET BEFORE BEING DRIVEN Button, Pan, Pan, Straight Neck Coned Neck Straight Neck RIVET POINTS Snap Liverpool Countersunk., Countersunk., Full Eaised Bearing stress here tress due to couple here Pan Head Faying surface Pull in pla^^^^Q^^^^^^^^^^^^^ k>vVV TivXxOvS^vE ^ ^ Shearing stress heW^ Hammered Point DRIVEN RIVET CONNECTING TWO PLATES FIG. 21. Rivets. The countersunk head rivet shown in Fig. 21 is used in places where a flat or flush surface is required, as in the riveting of the shell plating to a bar keel, or in a steel deck to be covered with wood, and in cases where the head must be calked. It reduces the strength of the plate, how- ever, since a larger portion of metal is cut from it. Pan- head rivets are used wherever it is possible. Button-head 68 PRACTICAL SHIP PRODUCTION rivets are used for appearance. The raised countersunk head gives slightly better holding qualities than the flat head. A coned neck is for the purpose of causing the rivet to fill completely the space in a punched hole, which is slightly tapered. Countersunk points, like countersunk heads, are used where a flush surface is required, or where calking the points is necessary. The best example of this is in the under water shell plating where projections would increase the resistance. Button points are used for purposes of appearance. Hammered points are used wherever possible, being, as a rule, cheapest, and nearly as efficient as any other points. The Liverpool point combines some of the advantages both of the countersunk and of the ham- mered point. The full or raised countersunk point is somewhat stronger than if perfectly flush. All counter- sunk points are, in practice, somewhat rounded out, or raised. The lowest sketch of Fig. 21 shows a rivet, after being driven, connecting two plates that are subjected to a pull, as shown by the arrows. This pull is taken by the rivet in the following ways: (a) There is a tendency for the body or shank of the rivet to be crushed by the bearing pressure on its upper right, and lower left sides. (These bearing pressures are also taken by the plates.) (&) There is a tendency for the rivet to be sheared along the plane that divides the two plates (the faying surface) . (c) Owing to the fact that the pulls in the two plates do not act in exactly the same straight line there is set up a couple, tending to cause the head of the rivet to move to the left, and the point to move to the right, thus bringing bearing pressures, acting in a vertical direction, onto the right side of the point and the left side of the head, which tend to tear the head and point from the body of the rivet. (These pressures also tend to squeeze in the plates under the edges of the head and point.) In all steel for ship construction the principal important GENERAL DESCRIPTION OF SHIPS 69 qualities required are strength, toughness and elasticity. A ship differs from a permanently fixed structure, like a building, in that there must be a certain amount of elastic flexibility to it. This is due to the forces set up by the motion and vibration of the ship when under way, and the action of the waves when in a heavy sea. It is very im- portant that a strict uniformity of the material be main- tained, and all ship steel should be carefully manufactured, inspected, and tested in accordance with properly drawn specifications. In naval vessels, for which the very highest quality of material is essential, the steel used is purchased under very strict specifications which are published by the Navy Department. Commercial ship steel is of not quite so high a quality but is considered satisfactory for merchant ships. Specifications are published by the various registra- tion societies covering steel for merchant ships. The shipbuilder should be thoroughly familiar with the various physical and chemical requirements of steel that is suitable for hull construction. Most of this steel is known as mild steel, and is made by the open-hearth process. It usually has a tensile strength of about 60,000 pounds per square inch and a shearing strength of about 50,000 pounds per square inch. For special strength combined with lightness (as in destroyers, scouts, etc.) a high tensile^ steel is used which has a tensile strength varying between 75,000 and 95,000 pounds per square inch. High tensile steel is about K stronger than mild steel. Iron. Cast iron is used for certain minor parts where strength is not an essential, although practically never used in the hull proper. Propeller blades of merchant vessels are sometimes made of cast iron. Wrought iron is used for anchor chains, anchors, steering- gear chains, straps for blocks, etc., miscellaneous black- smith work, piping, etc. It should have a tensile strength of about 45,000 pounds per square inch and the other physical and chemical qualities necessary for the use to which put. 70 PRACTICAL SHIP PRODUCTION Iron does not corrode as rapidly as steel but has much less strength. Non-ferrous Metals. Zinc is used principally to pre- sent rusting or corrosion of iron or steel parts due to the action of salt water in contact with them. For this purpose the parts may be completely galvanized or small plates of rolled zinc may be attached to various points of the underwater hull where galvanic action is especially apt to occur, such as in the vicinity of propellers, rudder, and openings in the shell plating. Copper is used for certain piping systems that must stand high pressures, for various kettles and steam tables, in sheets for sheathing wood planking under water and combined with zinc and tin in various bronzes and brasses used for castings. Manganese bronze is used principally for propeller blades and hubs. It has a very high tensile strength, about 65,000 pounds per square inch, and contains approximately 58 percent of copper, 40 percent zinc and 1 percent manga- nese with a small amount of tin, aluminum, iron and lead. Phosphor bronze is used for stem, stern, and rudder frames, shaft struts, etc., of bronze or sheathed vessels. It contains about 90 percent of copper, 9J^ percent of tin and ^ percent phosphorus, and has a tensile strength of 30,000 to 35,000 pounds per square inch. Naval brass contains about 60 percent copper, 37 percent zinc, 1 percent tin, with a small amount of iron, aluminum, and lead. There is less tin as a rule in brass than in bronze. Brass is used for small castings, where great strength is not so important, being much weaker than bronze. These include rail fittings, scuppers, stowage brackets, short rail and ladder stanchions, hatch and hatch cover frames, skylight, door and scuttle fittings, pipe flanges, valves, hand wheels, air port fittings, etc. The percentages of the materials used in the different copper-zinc-tin alloys vary considerably, slight changes in the quantities of each producing entirely different qualities, to suit different requirements. GENERAL DESCRIPTION OF SHIPS 71 Lead is used for lining steel and copper pipe, sheathing in cold storage spaces, plumbing work, storage battery tanks, etc. Wood. Nearly all kinds of wood find a certain use in ship construction. Oak and yellow pine are largely used for the hulls of wooden ships, barges, lighters, tugs, etc. In steel ships wood is used for deck planking, partition bulkheads, sheathing in coal bunkers, holds, etc., for masts, spars, derricks, gun- and small machinery foundations, ladders, gangways, hatch covers, gratings, boats, booms, furniture, shelving, lockers, chests, fittings, and for a variety of other minor purposes. For auxiliary purposes, during the building of the hull prior to launching, wood is used to a considerable extent (piles, cross logs, building blocks, launching ways, staging, scaffolding, shoring, wedges, etc.). Yellow pine is most used for decks, although teak is somewhat used for this purpose. Booms and spars are commonly made of pitch pine, Oregon pine, or spruce, Sheathing may be of white or yellow pine depending upon its location and the amount of wear and tear to which subjected. A considerable variety of woods are in use for furniture, stateroom bulkheads, lockers, etc., etc. Lignum vitse is used for stern tube bushings. Blocking, shoring and wedges are commonly of yellow pine or oak. Piles are usually pine or fir stems. Only the best quality of timber should be used for ship work and it should be carefully inspected. The most common defects to be looked out for in lumber are knots, shakes, heart centres, worm and bee holes, crooked grain, sap wood, splits, wane, extreme curvature, etc. Shakes are fissures or cracks in the wood. The heart is the portion of the wood at the centre of the trunk of the tree, and the sap wood is that nearest the bark. Wane is an inequality in a board or plank caused by its being sawed from a portion of the log too close to the outside. Flitches are slabs or pieces of timber sawed from the outer part of the log. Knees are pieces of timber cut from the 72 PRACTICAL SHIP PRODUCTION part of the tree where the roots join the trunk, so that they have a natural curvature, or bend. Miscellaneous Materials. Canvas is used for awnings, sails, tarpaulins, hatch hoods, wind-sails and sometimes as a covering over wood decks, and for gaskets and stop-waters. Cork is used for sheathing compartments against heat, for life preservers, etc. Asbestos is used for lagging or covering certain pipes or bulkheads subjected to high temperatures. Linoleum is used as a deck covering. Rope is used for tackles, purchases, shrouds, stays, lifts and other rigging parts. Cotton and oakum are used for making tight the seams between deck planks and outer planking of sheathed or wooden vessels. Rubber is used extensively for gaskets of water-tight doors, hatches, manholes, ports, etc. Tar and leather are used for various purposes in connection with the rigging. Heavy paper or cardboard is used for making templates and in some cases for gaskets and sto^-waters. Tarred paper is used in insulating bulkheads. Ceramic tiling and various special compositions are used as deck coverings in bath rooms, wash rooms, galleys, etc. Paints and Cements. One of the principal drawbacks to the use of steel for ships is the gradual wasting away of the material caused by rust or corrosion. In order to prevent or minimize this action a great variety of paints and other protective coatings are in more or less general use. The steel bottoms of ships must also be coated so as to reduce, as much as possible, fouling, or the attachment to the plating of various marine growths, such as weeds, grass, shells, barnacles, etc. Ship's Bottom Paints. The underwater plating of steel ships is painted with anti-corrosive and anti-fouling paints. The anti-corrosive paint is applied usually as the first two coats, to the underwater plating of the hull and is for the purpose of preventing corrosion or rusting. The anti- fouling paint is applied over the anti-corrosive (usually as one coat) and is for the purpose of preventing fouling, or the attachment of various marine growths. In order to do this two objects are sought: (1) to make the paint poison- GENERAL DESCRIPTION OF SHIPS 73 ous so as to kill or drive off the seaweed, barnacles, etc., and (2) to give it a certain soapiness so that by gradually washing away it will continue to give off the poison. A great many different special ship's bottom paints are on the market some good and some poor. None is entirely successful in attaining the objects sought. Anti-corrosive paints were formerly almost always oil paints, plain red lead being largely used, but certain quick drying paints are now used considerably, these being composed of alcohol, shellac, zinc oxide and other similar materials. Such paints do not, however, adhere well to bare steel, and a new ship should be first painted with red lead, which fills up the pores of the metal and when scraped off gives a good surface for the adherence of the first coat of anti-corrosive. Anti- fouling paints are given their poison quality by the use of copper, arsenic, etc. A typical paint of this sort contains alcohol, shellac, pine tar, turpentine, white zinc oxide, Indian red, and red oxide of mercury. Oil Paints. For ordinary steel material exposed to the weather or to moisture the most commonly used protective paint is red lead or oxide of lead mixed with raw linseed oil and a small quantity of petroleum spirits and drier. Other paints may contain lead carbonate, iron oxide, metallic zinc, zinc oxide, etc. Red lead is best, however, and is used to a very great extent. It is used as a first coat for practically all steel material, being applied to the dry, clean, bare metal. Other oil paints with suitably colored pigments are used for finishing coats, over the red lead. The vehicle is almost always linseed oil. Bituminous Compositions. These are black tar-like compositions which are practically impervious to water, and, when properly applied, adhere well to steel. They are usually in the form of a solution, an enamel, and a cement. They are sold under various trade names and the manu- facturers keep their composition more or less secret. How- ever, it is fairly well known that they contain various kinds of asphalt, rosin, Portland cement, slaked lime, petroleum, and similar ingredients. The solution is a liquid which is 74 PRACTICAL SHIP PRODUCTION applied cold with a brush and is used as a priming coat for either the enamel or cement. The enamel is applied hot over the solution after the latter is nearly dry or set, being poured where possible and otherwise spread over the surfaces. It forms a tacky, sticky mass, which hardens as it cools, but always remains fairly elastic and ductile. The cement is also applied hot, but is more difficult to apply than the enamel and can usually be applied only to horizontal surfaces. Experience with such compositions has not always been satisfactory. It has been noted that they were too thin a coating to give proper protection against coal and other hard lumps rubbing against them, that they are either too brittle and flake and chip off, or that they are too soft and flow at only moderately high temperatures, and that they blister. Practically all of these objections can, however, be, and are removed by proper care in preparing the materials, and intelligent skill in their application, with the result that a highly efficient protective coating can be thus obtained. Bituminous solution and enamel or cement are therefore used considerably for the following spaces in ships: ballast and trimming tanks, double bottom tanks, chain lockers, reserve feed tanks, fresh water tanks, tank top, coal bunkers, engine and boiler foundations, etc., below floor plates, shaft alleys, and various spaces that are not readily acces- sible for cleaning and painting. In applying these compositions great care must be used to see that the metal is dry, bare and absolutely free from rust, dirt, grease, etc., and that wide variations in the temperature of the metal are avoided. Cold weather and conditions liable to cause sweating should be avoided. Artificial ventilation must be provided for the workman, who, even then can work in the fumes for only short periods at a stretch. The success or failure of such coatings de- pends upon whether or not they are applied properly in the beginning. GENERAL DESCRIPTION OF SHIPS 75 Portland Cement. Portland cement of good quality, mixed with sand (usually about 2 or 2K parts of sand to 1 part of cement) is used in ships to protect the steel material where it is subject to rubbing of various hard articles, where it is not readily accessible for painting, where also necessary for drainage purposes, and under tiling. Where the thickness must be considerable, as in the pockets between frames near the ends of the ship, it may be lightened by having coke mixed with it. It is not, ordinarily, used in double bottoms. If the cement does not adhere firmly to the metal underneath not only will corrosion not be prevented, but it may go undetected, which is serious. For this reason many persons are opposed to the use of cement. It is also liable to be cracked or crumbled by the action of the vessel in a seaway. On the other hand, if properly applied it should form a good bond with the steel, and has several advantages over coatings that would otherwise be used. The tendency, however, seems to be to use more bituminous compositions and less Portland cement. Smoke stack paints are designed to withstand the heat to which they are normally subjected. They contain litharge, whiting, lampblack, silica, white lead, white zinc, mineral oil, etc. Shellacs, varnishes and various other special paints are used for a number of miscellaneous purposes on board ship. The relative advantages of various paints, compositions, cements, varnishes, etc., are always open to argument, since none are perfect, all are more or less advertised, and results of experience, depending, as they do, upon both material and skill of application, are not always reliable guides. A knowledge of the values of these different coatings as preventers of corrosion is, however, important to the shipbuilder, and even more so to the ship operator, since if corrosion is not properly prevented the ship will in a few years be wasted away to nothing. Good paints and other coatings, well applied, are economies in the long run. 76 PRACTICAL SHIP PRODUCTION Weights of Various Materials. It is necessary fre- quently to calculate or to estimate the weights of various members, parts or fittings of ships, and for that purpose the unit weights of some of the materials most commonly used should be known. These are given below: Weight in Ibs. Material per cu. ft. Ship steel 490 Wrought iron 480 Cast iron , 450 Copper 550 Brass (about) 525 Bronze 535-550 Lead 710 Live oak 67 White oak (about) 45 White pine; spruce (about) 30 Teak 45-60 Portland cement and sand (about) 130 Cork (about) 14 Yellow pine (about) 45 CHAPTER III STRUCTURAL MEMBERS OF SHIPS 1. TRANSVERSE AND LONGITUDINAL FRAMING In the great majority of ships the framing is of the transverse type the frames forming the "ribs" which extend out on each side perpendicular to the keel or "back bone." This principle of construction is simply an exten- sion of that shown in Fig. 13 (B). The keel running longi- tudinally along the centre line of the bottom gives fore and aft strength. Considering the ship as a girder the keel forms a portion of the lower "flange," the main deck similarly forming a portion of the upper "flange." Shell plating In wooden ships the keel is a heavy solid timber of rectangular cross section, and with the introduction of the use of iron for shipbuilding purposes it was naturally replaced by a heavy wrought iron bar of somewhat similar cross section. Such keels are still used to some extent in steel ships and are called bar keels. In the left-hand sketch of Fig. 22 is shown such a keel. The lower plates of the shell plating are flanged or bent down as shown so as to fit snugly against the sides of the keel to which they are 77 78 PRACTICAL SHIP PRODUCTION fastened by means of long through rivets extending through the three thicknesses of plate, keel, and plate. Such a keel, owing to its large cross section, furnishes considerable strength, and, owing to its depth, great vertical stiffness, but it has the disadvantage of increasing the draft of the ship, and it has therefore been replaced in almost all ships by the flat plate keel. The right-hand sketch in Fig. 22 shows a flat-plate keel which is a long course of plating, dished on each side, and connected by lap joints to the lower plates of the shell plating. The keel therefore forms a portion of the shell plating. In this type of construction the flat plate keel is supplemented by a continuous vertical plate, as shown in the figure, called the centre vertical keel or centre keelson. This is secured to the flat plate keel by an angle bar on each side and is stiffened at its upper edege by another angle bar on each side, as shown. All of these members are con- tinuous so that they serve to form a deep powerful centre- line girder. The lower flange of this girder is further strengthened by the shell plating attached to each side of the keel. The transverse frames furnish the direct support for the shell plating against the pressure of the water and also serve to transmit the vertical forces caused by the wieghts carried by the decks down to the bottom of the ship. On account of the shape of the ship they have considerable curvature and constitute one of the features of steel con- struction in which ships differ from structures of other types. The transverse frames are located at stations similar to the cross sections 2, 3, 4, 5, etc., in Fig. 16, but are spaced at much shorter intervals. The interval between two successive frames, called the frame spacing, varies between about IS" in small vessels and about four feet in large ones. The frame spacing is normally constant throughout the length of the ship, being reduced only where special local stiffness is required (as under engines, boilers and other heavy weights). At certain of the frame stations the STRUCTURAL MEMBERS OF SHIPS 79 ordinary frames are replaced by transverse bulkheads, which in addition to serving as partitions, may be con- sidered, in this connection, as solid frames. The beams of the decks, which run athwartships between the upper portions of the frames, act with them in furnishing trans- verse stiffness and complete the "ring" of each frame. The simplest type of frame is a single angle bar, bent to the shape of the section at which it is located. One flange of the angle bar is then flat and lies in a transverse plane throughout its own length, the heel and toe of this flange being curved to the shape of the transverse section of the ship at that frame station. The line of the heel of the bar lies in the molded surface of the ship, and, when viewed from directly forward or aft, has the exact shape of the frame. Due to the form of the ship each frame curve varies slightly from the neighboring ones except in the parallel middle body. The other, or longitudinal flange is formed to and lies in the molded surface of the ship, so that the inner surface of the shell plating may rest snugly against it. In the parallel middle body the longitudinal flange is everywhere at right angles to the transverse flange, but at all other parts of the molded surface the angles between the flanges are greater than 90, on account of the transverse curvature of the molded surface. This is due to the fact that the frames are arranged so that the bosoms of those in the forward portion of the ship will "look"' aft, and of those in the after portion, forward, thus giving all frames an open bevel. Figure 23 shows a portion of the framing and shell plating of a ship fitted with simple angle frames. The planes ABC, DEF, and GHK are planes of such transverse frames, being drawn square to the keel line of the ship. The distance AD or DG is the frame spacing. The transverse flanges of the frames lie in these transverse planes, as shown, and the longitudinal flanges lie in the molded surface or against the inner surface of the shell plating. The con- struction is shown in section in the lower portion of the PRACTICAL SHIP PRODUCTION figure, the necessary bevel of the frame angle, in order for it to fit against the shell plating, being as indicated. The shell plating is fastened to the longitudinal flange by a single row of rivets, which are fairly widely spaced, since their spacing has no effect upon the water tight ness of the shell. Shell Plating Molded Edge or Heel of Frame Angle Frames Longitudinal- Flange Angle of open Bevel !K Transverse Flange PERSPECTIVE VIEW Molded Edge / | / of Frame Shell Plating Longitudinal ' Flange of Frame ' SECTION NORMAL TO SHELL PLATING ^Transverse Plane FIG. 23. Simple transverse framing. The construction just described might be suitable for a very small vessel, but for larger ones it does not give suffi- cient stiffness, and therefore it is customary to reinforce the frame angle bar by another angle called a reverse frame, or to substitute for the simple angle frame a channel, bulb angle, or Z-bar as shown in Fig. 24. The reverse frame is riveted to the transverse flange of the frame and the two combined act as a girder in supporting the shell plating, the two transverse flanges forming the -web, and the reverse STRUCTURAL MEMBERS OF SHIPS 81 frame furnishing additional flange strength. The use of channels, bulb angles or Z-bars accomplishes a similar result without so much riveting. For even greater strength a plate may be introduced between the frame and reverse frame, thus giving a deeper Shell Plating FRAME AND REVERSE FRAME (SECTION A B, FIG. 23) Shell Plating Shell Plating Rev. Frame FLOOR PLATE (SECTION CD, FIG. 25) Shell Plating BULB ANGLE FRAME Z-BAR FRAME Fia. 24. Transverse framing. web and increasing the strength of the whole as a girder. This construction is also illustrated in Fig. 24. Such plates are usually fitted between the frames and reverse frames over the bottom shell plating in order to reinforce and stiffen the bottom of the ship, and are then called floor plates. Floor plates have the same depth as the centre vertical 82 PRACTICAL SHIP PRODUCTION keel at the centre line of the ship and are reduced in depth about uniformly from the centre until at or near the turn of the bilge the depth becomes the same as that of the trans- verse flange of the frame bar, and they are terminated. A similar construction is found in web frames (also called deep frames or belt frames) in which the full depth of the Bracket for attachment . of deck beam - Floor Plate cut off at corners to clear top and bottom angles of Centre Vertical Keel. J4 B See Eig.24J utboard end of Floor Plate Frame Angle - Floor Plate "Clip to connect Floor Plate to Centre Vertical Keel FIG. 25. Frame, reverse frame, and floor plate. web plate is maintained throughout the entire girth of the frame. These are special frames fitted to give great transverse strength, and occur at intervals of a number of frame spaces apart. They may be considered as partial bulkheads. Ih Fig. 25 is shown a transverse frame, reverse frame and floor plate, the section at AB being the same as that STRUCTURAL MEMBERS OF SHIPS 83 of the frame and reverse frame shown in Fig. 24, and at CD as that of the floor plate in Fig. 24. (The bevel of the frame and reverse frame angles is not, however, indicated in Fig. 25.) Referring to Fig. 25 the following points will be noted. The outboard or tapered end of the floor plate is bent, in its own plane, to the curvature of the frame and reverse frame angle bars between which it is fitted. It is reduced in weight by means of several large circular lightening holes cut or punched in it. At its end is fitted a tapered filling-in piece or liner which fills the space between the frame and reverse frame at their junction. Small circular limber holes are cut in the lower portions of the floor plates in order to permit water to pass through for drainage. The floor plates are fastened to the centre vertical keel by means of short pieces of angle bar, called clips or lugs. Brackets, or triangular-shaped plates are fitted to give a suitable connection of the beams to the frames. The inboard corners of the floor plates are cut off sufficiently to permit the upper and lower angles of the centre vertical keel to run through continuously. In order to prevent racking, or fore and aft movement of the frames, reverse frames, and floor plates, and to tie them together and add to the support that they furnish to the shell plating (as well as to add to the longitudinal strength of the ship) certain fore and aft members called keelsons and stringers are fitted in addition to the keel and centre vertical keel. These consist of angle bars, single or double, running along the inner edges of the reverse bars and con- nected to the shell plating by flat plates placed normally to the curvature of the molded surface. The number and disposition of these members depends upon the size and type of the ship. Keelsons run approximately or exactly parallel to the centre vertical keel. Those nearest the keel are called side keelsons, and those near the bilges, bilge keelsons, the general construction of both being about the same. The surfaces of these members intersect the surfaces of the floor plates approximately at right angles, and therefore the 84 PRACTICAL SHIP PRODUCTION plate portions of them must be made in sections to fit between adjacent floor plates. Such plates are called intercostal plates, the term intercostal being applied in general to any member which is formed of separate parts fitted between successive continuous members that it intersects. In Fig. 26 is shown a side elevation and cross section of a side keelson and also a separate view of one of its intercostal plates. The intercostal plates fit snugly against the floor plates but are not connected directly to Continuous Keelson Angles- INTERCOSTAL PLATE FIG. 26. Intercostal side keelson. them. The keelson angles are tied to the shell plating by means of the intercostal plates which are clipped to the shell. Along the line of the keelson angles, which run continuously along the inner edges of the floor plates, are fitted short lugs, riveted to the floor plates on the side opposite the reverse frames, to give a rigid attachment for the keelson angles. The frames and reverse frames are continuous and pass through notches cut in the intercostal plates. Stringers have a construction very similar to that of keelsons, but being located above the outboard ends of the floor plates (see Fig. 28) the stringer plates do not have to be entirely intercostal and are simply notched out for the frames and reverse frames. The construction of a STRUCTURAL MEMBERS OF SHIPS 85 stringer is shown in Fig. 27, which gives good continuity of longitudinal strength. Stringers located near the bilge are called bilge stringers, and those higher up, side or hold stringers. In Fig. 28 is shown a cross section of a ship framed on the principles just described, that is, with transverse frames, reverse frames and floor plates, and centre vertical keel. This figure is merely for the purpose of indicating the general construction and the relative dimensions are not strictly accurate. Only one keelson is shown, but in a larger ship several might be fitted between the centre Reverse Frames- Shell Plating Frames- pyyt oiip myi u If \ Continuous \ Angle PLAN Stringer Plate FIG. 27. Side stringer. vertical keel and each bilge. It will be noted that the outboard deck plating which is attached directly to the shell also assists in furnishing longitudinal strength. These plates are usually made heavy for this purpose and on account of their function are called deck stringer plates. Girders are also fitted under the decks, as shown in the figure, which, together with the deck stringers and upper portion of the shell plating give longitudinal strength to the upper ''flange" of the ship, considered as a girder. Ships, except very small ones, are usually fitted with double bottoms so that the construction of the lower por- tion is somewhat different from that shown in Fig. 28. The double bottom is formed by fitting plating over the tops of the floor plates and curving it down at the sides to join the shell^plating. In this case the depth of the floor plates 86 PRACTICAL SHIP PRODUCTION is maintained nearly constant from bilge to bilge and the inner bottom is usually flat and horizontal. The continu- ous keelson angles shown in Fig. 26 are omitted and the keelson plates extended only to the tops of the floor plates. Deck stringer plate 'Lightening: ho Centre Vertical Keel Shell plating Frame "Clip or lug Flat Plate Keel Floor Plate FIG. 28. Cross section of a ship showing longitudinal framing. They are given sufficient strength to make up for this re- duction by the inner bottom plating to which their upper edges are now attached. Instead of being called keelsons they are then spoken of as longitudinals. Floors 2d Longitudinal starb'd \ | DeckBeam- 3iip , . , /\.^ 4 II .^- Girder Plate ' irder Intercostal Clip/ X fVT (notched at / \y\ Deck Beams) Flanged Bracket / / ^Mt-y Continuous Girder Clip/ Angles Stanchion M Continuous Plate SINGLE ANGLE GIRDER "Stanchion DEEP PLATE ANGLE FIG. 57. Deck girders. Decks are ordinarily made water-tight in order to increase the danger of loss of buoyancy caused by damage to the shell plating. Therefore as a general rule all openings cut in decks should have means for their being tightly closed. Some of the methods used for this purpose are shown in Fig. 58. The simplest is a flat plate secured by means of stud bolts as shown in the upper sketch. A gasket of canvas soaked in red lead or some other suitable material is interposed between the cover and the deck plating. If the joint must be oil- tight canvas soaked in a mixture of pine tar and shellac or card board and varnish is used for the gasket. Another method, used for covers to manholes (small oval holes just big enough to admit a man) is shown in the middle sketch. Here a heavy strong back .and a large bolt through the centre of the manhole plate are STRUCTURAL MEMBERS OF SHIPS 121 used. Where perfect water-tightness combined with quick removal is required, some method similar to that shown in the lowest sketch must be used. Here a rubber gasket held by strips is secured around the outer edge of the cover plate, so that when the plate is drawn down, by bolts fitted as shown, the gasket is compressed against the upper Bolted Plate BOLTED PLATE Strongback STRONGBACK AND BOLT Manhole Plate (oval) Do* Hatch Cover Bolt WATERTIGHT HATCH COVER Coaming Ang Deck Plating FIG. 58. Covers for openings in watertight decks. edge of the coaming. This general method is used con- siderably for manhole covers, hatch covers, water-tight doors, etc. The circumferences of such openings or of their covers may be reinforced by stiffening rings. 6. BULKHEADS Bulkheads are vertical diaphragms or partitions of vari- ous construction. According to the directions in which they extend they are called transverse or longitudinal. 122 PRACTICAL SHIP PRODUCTION Longitudinal bulkheads are not much used in merchant ships, which usually require broad hold spaces, but are im- portant features in warships w r here they serve to increase the fore and aft strength, and underwater protection. Transverse bulkheads are important in all types of ships since, as well as furnishing transverse strength by their stiff diaphragm action and the support that they give to stringers, decks, etc., they subdivide the length of the ship into a number of holds or compartments and thus limit the space that may be flooded if the shell plating is punc- tured. In fact it may be said that the chief function of all such bulkheads, except those not forming an integral portion of the hull structure, is to furnish a means of water- tight subdivision. Bulkheads, like decks, consist of plating and reinforcing bars. In the case of bulkheads the reinforcing bars are called bulkhead stiff eners. In some cases the stiff eners are formed by flanging the edges of the bulkhead plates, but the principle is the same. In some cases the stiff eners are fitted in horizontal lines only, sometimes in vertical lines only, and in some cases both horizontal and vertical stiff eners are used on the same bulkhead. A bulkhead designed to assist in watertight subdivi- sion must be made of heavy enough plating and must be sufficiently stiffened to resist bending or bulging in case of flooding of either of the compartments of which it forms a boundary. If the sightest deflection takes place some of the rivets or seams are almost sure to start leaking. There- fore the stiffeners must be strong, closely spaced, and properly supported at their ends. In very large, deep bulk- heads the construction must be much more rugged than in small ones, depending, as it does, upon the head of water to which they may be subjected. In Fig. 59 is shown a simple construction of a bulkhead. The plating is arranged in horizontal strakes and the stiff- eners, in this case bulb-angles, run vertically. The plating is secured to the deck, shell, and tank top plating by means of double angles called boundary or bounding bars. The STRUCTURAL MEMBERS OF SHIPS 123 lower strakes of plating (which would have to withstand greater pressures) are made heavier, and the lower ends of the stiffeners are given a rigid support by means of plate brackets riveted to their fore and aft flanges and to clips which are in turn riveted to the tank top. The above described construction is modified and ex- tended in a great many different ways to suit different sizes and types of ships. In some cases single boundary bars are Deck Plating Bounding Bars /Stiffener Bulkhead Plating .Brackets-^ /Bounding J Bars MX/Bracket Tank Top leBo torn Stiffeners SECTION ON AB Shell Plating SECTION ON C D FIG. 59. Bulkhead. sufficient. The plating is sometimes arranged in vertical strakes. The seams are frequently joggled. The stiffeners may be simple angle bars, channels, Z-bars, T-bars, I-beams, or may be built up of plates and shapes in the form of heavy girders in which case their heads and heels are reinforced and connected to the decks and inner bottom by large built up brackets with heavy face bars. Ordinarily the plating of the decks is continuous and the bulkhead plating 124 ' PRACTICAL SHIP PRODUCTION is cut at the decks, although this may not always be the case, especially for longitudinal bulkheads. Transverse bulkheads designed as watertight dia- phragms must be carefully fitted where necessarily pierced by longitudinal members, such as stringers, girders, piping, etc., so as to maintain water tightness. To this end staples and collars made similarly to those shown in Fig. 54 are fitted around the longitudinal members at the bulkheads. The same applies to transverse members piercing longi- tudinal watertight bulkheads. Watertight bulkheads are tested by filling the compart- ments of which they form boundaries with water, and ascertaining if any leaks occur. Horizontal bulkhead stiff en ers are usually arranged so as to connect with side and hold stringers, where such members occur. Certain non-watertight or partition bulkheads are found in all ships, being installed for purposes of subdivision of space into staterooms, galleys, pantries, wash rooms, store- rooms, etc., etc. These may be of wood, light sheet metal or wire mesh, and furnish little if any strength or water- tightness. Longitudinal coal bunker bulkheads in mer- chant vessels are fairly strong and heavy but are not usually made watertight. Doors in water-tight bulkheads must be watertight and are usually constructed on the principle shown in the lowest sketch of Fig. 58, the details, of course, being somewhat different. 6. MISCELLANEOUS The main structural members of ships have been de- scribed in the preceding sections of this chapter, but there are, in addition, certain auxiliary structures and fittings which are either built into or securely attached to the hull, and with which the shipbuilder is therefore concerned. Of these there are a great number and their design and con- struction vary considerably. Among the principal ones may be mentioned engine and boiler foundations, and STRUCTURAL MEMBERS OF SHIPS 125 foundations for shaft bearings, thrust blocks, auxiliary machinery, winches, guns, davits, masts, derricks, etc., hawse pipes, chain pipes, mooring pipes, chocks, bitts, rails and bulwarks, bilge and docking keels, fenders, etc. Engine foundations must be heavy and strongly built and well supported by the adjacent structure of the ship. Often times the frame spacing is reduced and the floors made deeper under the engines in order to give additional vertical strength. The foundations for the engines are built up on top of the inner bottom usually of plates and angles well ndation Plate Bracket \/ Girder / Plate Longitudinals^/ /Shell Plating FIG. 60. Portion of engine foundation. bracketed and reinforced in all directions. A typical construction is shown in Fig. 60. The girder plates of the foundation should be nearly in line with longitudinals so as to preserve continuity of strength and the athwart- ship members are ordinarily directly over the floors. A typical method of supporting the boilers is shown in Fig. 61. The saddles are plates cut to a curved shape to fit against the boiler shell and are reinforced by double angles around their edges as shown, and the successive saddles are connected at their outer sides by longitudinal plates. Special foundations of a great many different types are installed in other parts of the ship, the principles of con- 126 PRACTICAL SHIP PRODUCTION STRUCTURAL MEMBERS OF SHIPS 127 struction being in general the same as for engine and boiler foundations. Hawse pipes are large castings, usually steel, securely built into the bows of the ship, through which the anchor chains may pass (see sketch of hawsepipe in Fig. 62). Chain pipes serve a similar purpose but lead entirely inside of the ship and nearly vertically down to the chain locker, as they do not have to have the peculiar terminations of Bolster Stiffener FIG. 62. Hawse pipe. hawse pipes. At the ends of either a hawse pipe or chain pipe, where the direction of the chain is sharply changed, the edges must be well rounded off by heavy bolsters, as shown in Fig. 62. For leading and securing hawsers to the ship from a dock or tug chocks, bitts, cleats, and similar fittings are securely attached to the decks, especially to the weather deck. Figure 63 shows bitts and a chock and a method of at- 128 PRACTICAL SHIP PRODUCTION taching such heavy fittings, which must transmit heavy stresses to the hull. In Fig. 64 are shown a section of a rail and bulwarks, two types of fenders, a docking keel and two types of bilge keels. The rail and bulwarks form a fence or enclosure around the edge of an open deck. The plating is light and should not be considered as furnishing much strength in addition to ELEVATION BITTS CHOCK PUN T? TT LO Sjv oV v METHOD OF ATTACHMENT OF BITTS TO DECK Plate FIG. 63. Bitts and chock. that of the sheer strake. In many cases open rails are fitted consisting of stanchions and horizontal rods with a wood railing on top. Fenders are fitted to prevent damage to the sides of tugs, barges, and similar vessels which fre- quently bump against other vessels or against docks. They usually run along the sides parallel to the upper deck and a few feet above the water line. Docking keels are STRUCTURAL MEMBERS OF SHIPS 129 fitted on battleships and other large heavy vessels to take a portion of the weight when in dry-dock. They run parallel to the centre keel and are usually located roughly at % of the half-beam of the ship out from the centre line. Bilge keels are fitted along the bilges and are designed to prevent or decrease rolling. They are sometimes called rolling chocks. Wood Rail Brace Bulwark Plating Shell Plating Fender-^ Deck-Stringer Plate BULKWARKS AND RAIL *_ Shell Plating \t~Fender PLATE FENDER She! Plating Shell Plating Docking Keel Plate Teck Filler Shell. Plating T-Bar Bilge .Keel Built-up Bilge Keel 1 BILGE KEELS DOCKING KEEL FIG. 64. Rail bulwarks, fenders, docking keel, bilge keels. Cofferdams are compartments formed by placing two bulk- heads close together, the space between, or cofferdam, being for the purpose of preventing leaks between the two spaces on either side of the cofferdam as, for example, between the end of an oil tank and an adjacent compartment. Drainage wells are small pockets placed in the lowermost compartments of the ship (often called, in this connection, the bilges) in order to permit water, etc., to collect therein, and thus to be readily pumped out. i CHAPTER IV DESIGN OF SHIPS 1. CONDITIONS TO BE FULFILLED The design of a ship is the first step in the process of ship production. It should be considered broadly as a question of cause and effect. A ship is needed to fulfil a given purpose. To fulfil this purpose she must meet certain requirements. In meeting these requirements certain obstacles must be overcome. The design of a ship then resolves itself into a problem of fulfilling the requirements sought, while at the same time overcoming the obstacles that are bound to be encountered. The designer is the planner who gives the orders, which must be executed by the shipbuilder. Each must be familiar, to a certain extent, with the problems with which the other is con- fronted in order that they may work together harmoniously in the process of ship production. Their work is also closely related to the questions of material, tools and labor avail- able. The designer's work is largely theoretical in nature; the shipbuilder's, practical. If the ship that is desired is to fulfil certain special and unusual requirements, the designer's task becomes more difficult, while, if, on the other hand, the requirements of the ship are practically the same as those of other ships that have already been designed, the designer's work is correspondingly reduced. Many shipyards have de- veloped certain more or less standard designs for ships, which they have built over and over again to the same plans. For such ships the designer's task disappears, the problem of producing them being entirely one for the shipbuilder. At the present time the great need in ship production is quantity. Any ship that is capable of carrying cargo or 130 DESIGN OF SHIPS 131 men across the ocean is very valuable, and since there 'are already available many plans for ships that will fulfil these requirements, the need is now more for shipbuilders than for ship designers. The space devoted to a discussion of the design of ships will therefore be limited, in order that more consideration may be given to the problems met with in the building of ships. It is, however, desirable that the shipbuilder be conversant, in a general way, with the work of the designer. The problem which is given to the designer for solution is to produce the plans and specifications for a ship that will have a certain speed, carrying capacity, steaming radius, seaworthiness, etc. These characteristics vary greatly with the type of ship. For example: in fighting ships certain armament and armor must be carried; in passenger ships a certain number of passengers must be fully provided for; in cargo ships a certain amount of cubic space and weight carrying capacity must be provided. The problem is often complicated by the question of cost. A limit in cost naturally causes a limit in size, and certain characteristics can be obtained only by an increase in size. The design of a ship is therefore, in many cases, in the nature of a compromise. Certain qualities must be sacrificed in order to obtain certain others. The ideal case is that in which the designer is simply given the conditions to fulfil, without any limitation as to the size of the ship. Under such conditions he can produce the best results. Except in very unusual cases, the design of a ship is based upon other ships already built and known to be satisfactory. The process of design consists in adapting data already at hand to suit the needs of the particular ship being designed. For this reason it is very important for the designer to possess as many different plans and as much data of all kinds regarding various ships already built as possible. This statement is based upon the well-known fact that experience is a better guide than theory. Nevertheless, it must not be forgotten that without theory and in- ventiveness, very little progress could ever be made. 132 PRACTICAL SHIP PRODUCTION 2. CHOICE OF PRINCIPAL ELEMENTS Having, been given the various requirements that are to be fulfilled in the proposed ship, the designer, taking advantage of his knowledge and experience, and of the data that he has available, determines roughly upon the size, or displacement, of the ship. Then, having due regard for the conditions to be met, he selects roughly the principal dimensions and coefficients such as length, beam, draft, block coefficient of fineness, coefficient of fineness of midship section, and load water line coefficient. This is largely a tentative process, since these elements are more or less inter-related, and is usually determined fairly well by the designer's knowledge of previous ships. If the ship is very similar to another already designed, a number of these elements may be practically fixed in advance. For example the block coefficient of certain types of ships is fairly well known, as are the ordinary ratios of length to beam and beam to draft. Since the displace- ment is directly dependent upon the product of length times beam times draft times the block coefficient, if the displacement has been decided upon, the other values can be fairly readily determined. The earliest rough design may be divided into two parts : (1) The determination of the principal elements of form and weight, and (2) The drawing of the lines and the location of the various weights so as to conform to the elements selected. The principal elements of form are the length, beam, draft and freeboard and the various coefficients. The principal elements of weight may be roughly expressed as the weight of the hull, fittings, crew, outfit, etc., the weight of the propelling apparatus (engines, boilers, aux- iliaries, etc.), and the weights that are consumable or removable. The classifications of these weights are very elastic and depend upon the type of ship. For instance, in war ships the removable weights form a relatively small percentage of the displacement, because of the large amount DESIGN OF SHIPS 133 of weight required to be permanently carried, for military reasons, made up of armor, turrets, barbettes, guns, torpedoes and the mechanism required for the operation of the ship and her weapons of offense, while in most merchant ships a great proportion of the displacement is given over to cargo carrying capacity. 3. CONSTRUCTION OF LINES AND DISTRIBUTION OF WEIGHTS Having decided tentatively upon the principal elements of form the designer proceeds with the drawing of the lines. After the lines are completed the various " weight groups " are located so as to give a satisfactory arrangement, practically, and at the same time to fulfil the fundamental laws governing the operation of all ships. These " weight groups " consist of the weight of the hull and fittings, weight of engines, boilers and auxiliaries, weight of fuel and water, weight of officers, crew, and their effects, and a number of other weight groups depending both upon the type of ship, and the method of grouping. Some of the fundamental laws which must be fulfilled are briefly outlined below: (1) The sum of all the weight groups for the condition of loading assumed in the design must be equal to the weight of water displaced by the ship at the design draft. (2) The position of the centre of gravity of the combined total of all the weight groups must be in a vertical line with the centre of buoyancy, or centre of figure of the under water volume of the ship. (3) The vertical position of the centre of gravity of the combined total of all the weight groups must be far enough below the metacentre to give a suitable metacentric height, and sufficient righting arm for all angles of inclination to which the vessel may ever be expected to heel. Preliminary rough calculations of the positions of the centres of gravity and buoyancy, and of the metacentre, must of course be made for this purpose. A certain amount of adjustment is usually necessary in this process, since 134 PRACTICAL SHIP PRODUCTION so many different conditions must be met that the problem cannot be approached in a strictly mathematical manner. Various locations must be assumed for the centres of gravity of the main weight groups, such as engines, boilers, fuel, cargo, etc., and the amounts of these weights must be estimated on the basis of the speed, endurance, cargo carrying capacity, etc., that it is desired to give to the ship. The methods of making the calculations are described in Section 5, below. 4. PRINCIPAL PLANS When the weights have finally been located so as to give, roughly, the desired solution of the problem, the next step in the design is the preparation of the principal plans which show in detail the locations and weights of the various members, parts, fittings and subdivisions of the ship, and from which exact calculations of all the weights of the ship may be made. The principal ones of these plans are, usually, the following : Midship section plan. Shell expansion. Stem, sternpost, propeller struts, rudder, etc. Engines, boilers and auxiliaries, etc. Inboard profile. Outboard profile. Deck, hold and inner bottom plans. Cross sections. Bulkhead, deck, and inner bottom plating plans. Various piping plans. The midship section is a plan showing a transverse section of the ship at the dead flat (similar to Fig. 28) and giving the principal dimensions (or scantlings) of the various shapes entering into the construction of the frames, beams, longi- tudinal, stringers, etc., and of deck and shell plating, etc. The shell expansion is a plan showing, in detail, the sizes of all the plates forming the shell. It is drawn by laying off along the ship's length as a base, ordinates representing DESIGN OF SHIPS 135 the actual girths of all the frames together with their intersections with the edges of the various shell plates (or the landing edges, as they are called). It will be noted that this is an expansion in the transverse direction only, and does not give the true form of the shell plates. A true expansion of the ship's outer form cannot be drawn, since it is an undevelopable surface. In order to obtain the true shapes of the various shell plates a wooden model is made and the plating laid off thereon. Plans of the stem, sternpost, propeller struts, rudder, etc., are simply working drawings of these various parts. Plans of the engines, boilers and auxiliaries, etc., represent a large amount of investigation and calculation on account of their intricate nature, and in most establishments are prepared by a set of designers and draftsmen distinct and separate from the hull designers, and forming the marine engineering department. The inboard profile is a plan showing a longitudinal vertical section of the ship* taken through the centre line (see Fig. 18). The outboard profile is a side elevation of the ship showing the masts, rigging, boats, davits, and other outer fittings. Deck, hold and inner bottom plans are views of the various decks, the hold, and inner bottom as seen from above, and show the subdivision of these various spaces. Cross sections are plans showing transverse sections of the ship at various points along her length. They indicate special features of framing, subdivision, etc., in these localities. Bulkhead, deck and inner bottom plating plans show the details of plating, riveting, stiffening, etc., of the various bulkheads and decks, and of the inner bottom. Piping plans show the various systems of drainage, fire protection, flushing, plumbing, fresh water supply, ventila- tion, etc. In addition to the above, in the case of war ships, there are drawn plans of the armor, guns, gun foundations, turrets, barbettes, torpedo tubes, etc. 136 PRACTICAL SHIP PRODUCTION Also there must be plans drawn for special local weights such as boats, davits, windlasses, steering gear, anchors, winches, dynamos, etc., etc., unless, as is often the case, plans for these already exist. In preparing the principal plans the designer is guided, in the case of merchant vessels, by the published rules of the classification society under which the ship is to be built. These rules provide for certain scantlings to be used for each size of ship, so that the designer, having decided upon the length, beam, depth, and principal coefficients of his ship, can, by referring to the classification society's rules and tables, determine at once the proper sizes for all the principal structural members. The warship designer is not limited by Lloyd's or any other such rules, and has more freedom in the choice of the scantlings. He is guided principally by his available information regarding other ships of similar type and size already 'built, and if any radical departure from these is made very careful investigations and extensive calculations are necessary. 6. FINAL CALCULATIONS Having completed the principal plans the next step of the designer is the detailed weight calculation. The principle involved in this process is simple, it being merely the deter- mination of the weight of each part and the exact location of its centre of gravity, and the combining of these in groups, so as eventually to determine the total weight of the entire ship, and the position of its centre of gravity. The work required is, however, very tedious, and involves an enormous amount of calculation, on account of the great number of different parts to be considered and the irregular shapes of many of them. No attempt will be made here to describe in detail the methods by which these calculations are made. In conjunction with the calculations for weights, calcu- lations must also be made for buoyancy, stability and trim. These also are simple in principle but tedious and involved DESIGN OF SHIPS 137 in practical application. They are based upon the general laws discussed in Chapter I. The calculation of the displacement consists in finding the total volume of the under water portion of the ship in cubic feet. This, divided by 35, is the displacement of the ship in tons since a ton of sea water occupies 35 cubic feet. The calculation of the position of the centre of buoyancy consists in finding the location of the centre of figure of the under water portion of the ship. BM = FIG. 65. Value of BM The calculation of the metacentric height is briefly as follows: The value of BM, the distance of the metacentre above the centre of buoyancy, calculated after the position of the centre of buoyancy B has been calculated, gives the location of the metacentre. This, together with the loca- tion of the centre of gravity G, calculated as described above, gives a means of finding GM, the metacentric height. The method of calculating BM is based upon the following general principle: Let Fig. 65 represent the cross section of a ship inclined 138 PRACTICAL SHIP PRODUCTION to a small angle A0. Let B be the original centre of buoy- ancy and B f the centre of buoyancy as inclined. Let y be the half -beam of the ship at this section and let longi- tudinal distances be represented by the variable, x. Let the volume of displacement = V. Since A0 is small BB r = BM -A0. Also the moment of the new volume of displacement about the plane passed longitudinally through OB is T$B' V. But since this new volume of displacement has been formed by subtracting the wedge, of which WOW is a section, from the original displacement, and adding thereto the equal wedge, of which LOL' is a section, this moment is also equal to twice the moment of either wedge. The moment of either wedge is /area AWOW XgOXdx where gO is the distance of the centre of gravity of the triangle from 0. But, again, since A0 is small, Area &WOW = Y 2 yM-y = ^- and 00 = %y :.BB'V = i- X or BM = (where Yzfy*dx is the moment of inertia of the load water plane about its longitudinal axis, which is called "I".) The calculation of BM therefore involves the calculation of the volume of displacement and the transverse moment of inertia of the load water plane. The method of calculating the longitudinal BM is along similar lines. Other stability calculations must also be made since the metacentric height is merely an index of the initial stability of the vessel. These calculations are long and involved, although, like the other ship calculations, they are based upon a simple principle. This principle is briefly expressed DESIGN OF SHIPS 139 by an equation known as Atwood's Formula which is that the moment of statical stability of a ship when inclined to any angle 6 is W ( V X y hh - - BG sin e\ foot tons where W = the displacement of the ship in tons V = the displacement of the ship in cu. ft. v = the volume of the immersed or emerged wedge in cubic feet hh' = the horizontal distance between the centres of gravity of the two wedges, in feet, and BG = the distance between the centre of gravity of the ship and her original centre of buoyancy, in feet. Moment of Statical Stability = W FIG. 66. Atwood's formula. These values are shown in Fig. 66, and, referring to that figure, the proof of Atwood's formula is as follows: The couple tending to right the ship has a moment W X GZ which is called the moment of statical stability. But GZ = BR - BP = BR - BG sin 6 But BR represents the horizontal shift of the centre of 140 PRACTICAL SHIP PRODUCTION figure of the volume of displacement from its old to its new position, and by taking moments : BR X V = v Xhh' :.WXGZ =W p- > y i/z L . BG sin 01 By suitable geometrical and arithmetical calculations it is therefore possible to find the moment tending to right the ship when heeled to any angle and when floating at any displacement. By dividing each moment by the value of the displacement the corresponding righting arm may be obtained. If several different displacements be considered and righting arms calculated for different inclinations, it is possible to plot a series of curves with righting arms as ordinates and displacements as abscissas. Such curves are called cross curves of stability. There are a number of different methods in use for making the calculations by which data for plotting these cross curves is obtained. Space does not permit going into detail regarding these methods here. All are based upon the assuming of certain poles about which the ship is considered as inclined, and corrections must be made to obtain the true righting arms because the actual locations of the centre of gravity of the ship are different from those assumed. By making these corrections it is possible to obtain, from the cross curves, certain curves showing, for various actual displacements and corresponding positions of the centre of gravity, the righting arms for all angles of in- clination. Such curves are called curves of statical stability, and are similar to the curve shown in Fig. 7. The statical stability at any angle of inclination of the ship is measured by the moment in foot-tons tending to right the ship when she is inclined to that angle. The dynamical stability is measured by the amount of work that must be done in bringing the ship from the upright position to the position considered. The curve of dynamical stability is therefore the integral of the curve of statical DESIGN OF SHIPS 141 stability, or each ordinate of the curve of dynamical stability may be calculated by obtaining the area of the curve of statical stability up to the abscissa corresponding to the angle of inclination considered. In addition to the calculations already mentioned there are also usually made calculations for: tons per inch immersion, moment to change trim I", areas of water lines, longitudinal C.G. of water lines, area of midship section, correction to displacement for 1 ft. trim by stern, area of wetted surface. The tons per inch immersion for any given draft of a ship is the number of tons increase or decrease in dis- placement that will be caused by the draft being increased or decreased, respectively, by 1 inch. Practically speaking if the ship sinks 1 inch deeper into the water along all of her water line the increase in displacement will be the volume of a slice 1 inch thick and having the area of the water line. (If the sides of the ship were vertical at all points this would be absolutely true) . Hence the tons per inch immersion is found by dividing the area of the water line (in square feet) by 12 X 35. (Thickness of slice is H2 fot an d there are 35 cubic feet of salt water to the ton. For fresh water the figure to be used is 36 instead of 35.) The moment to change trim I inch is the longitudinal moment, in foot-tons, necessary to cause the ship to change her trim by 1 inch from the water line at which she is con- sidered to be floating. It is equal to }{ 2 of the displace- ment in tons, multiplied by the longitudinal metacentric height in feet, divided by the length on the water line con- sidered, in feet. The reason for this is that when the ship changes trim 1 inch she is inclined longitudinally to an angle with her original position of which the tangent is K 2 ft divided by the length of the water line in feet, this inclina- tion also having for its tangent the distance that the ship's centre of gravity may be considered as moving longitudi- nally divided by the longitudinal metacentric height. (The center of gravity is here considered as moving from G to G' because of the moving of a weight of w tons, longitudi- 142 PRACTICAL SHIP PRODUCTION nally, through a distance of d feet. The moment causing the change of trim is then w X d foot-tons.) Hence, if be the angle of longitudinal inclination = -rTf = r- (where L is the length in feet). But W X GG' = w X d (where W = displacement in tons). (Since the ratio of the shifts of the centres of gravity of the ship and the weight moved is the inverse of the ratio of their respective weights) . Hence the moment to change trim 1 inch or The calculations of the areas of water line, position of longitudinal centre of gravity of water line, area of midship section, and correction to displacement for 1 foot trim by the stern for any given water line, are made by the methods described below, being simply geometrical calculations. By making calculations of each for several different water lines curves can be plotted giving values for all inter- mediate points. The correction to displacement for 1 foot trim by the stern is the amount that must be added, in order to obtain the true displacement, to the displacement corresponding to a water line drawn parallel to the load water line and at a level corresponding to the mean draft at which the ship is floating. When the ship changes trim the shape of the water line changes on account of the difference between the form of the molded surface at the forward and after ends. Since displacements are ordinarily calculated only for water lines corresponding to various drafts on an even keel it is necessary to have a means of correcting these to find the displacements when floating out of the designed trim. The correction is j tons (additive) DESIGN OF SHIPS 143 where T is the tons per inch immersion, L is the length of the water line in feet, and d is the distance that the centre of gravity of the load water plane is aft of amidships, in feet. (Should the centre of gravity of the water plane be forward of amidships the correction will, of course, be subtractive instead of additive.) The area of wetted surface is calculated for use in figuring the frictional resistance of the ship. It cannot be calculated exactly on account of the ship's surface being undevelop- able, but for practical purposes, different approximate methods can be used which give sufficient accuracy. One of these, known as Kirk's Analysis consists in cal- culating the wetted surface by the expression (2LD + ex LB) where L is the length of the ship, in feet, D is the draft of the ship, in feet, B is the beam of the ship, in feet, oc is the block coefficient of fineness, and the resulting value is the total area of the wetted surface in square feet. Other approximate formulas for the wetted surface, in square feet are: Admiral Taylor's: 15.5VWX where W= displacement, in tons, and j L = length, in feet. Mr. Denny's: 1.7LD + J where L = length, D = draft (feet) and V = volume of displacement (cubic feet) . A more accurate calculation can be made by finding the area of a curve of modified girths, each girth being taken 144 PRACTICAL SHIP PRODUCTION along a frame station and increased by multiplying it by the average secant of the angle between the molded surface and a fore and aft line taken at the station considered. The methods of making the various calculations outlined in the preceding paragraphs are based upon various means (A) ^ y z )h + c Trapezoidal Rule : Area ABCD = $(y 2/3 Simpson's First Rule : D Area ABCD = -= (yi + 4y 2 + j/ 3 ) + 2/3 Trapezoidal Rule : Area ABCD = h\ y ~ + y 2 +y 3 + ~ Simpson's Second Rule : Area ABCD = p(?/i + 3y* + 37/ 3 + 11 Five -Eight " Rule : Area ABMN (in diagram (A)) -2/3) In General : O FIG. 67. Methods of integration. of integration, it being necessary in the case of a ship to obtain certain areas, volumes, moments, and moments of inertia of curvilinear areas and volumes, not susceptible of exact mathematical calculation. DESIGN OF SHIPS 145 These are most commonly obtained by the Trapezoidal Rule, Simpson's Rules, and graphically by means of the planimeter and integrator. The trapezoidal rule is used when it is assumed that the ordinates are so closely spaced that the curve between any two adjacent ordinates may be considered, for all practical purposes, as a straight line. For a convex curve this gives too small an area (see Fig. 67). Simpson's Rules are shown in Fig. 67. These may be extended to a large number of intervals, it being noted that the first rule applies when the number of intervals is even; and the second when it is a multiple of three. The five-eight rule may be used to find the area between two successive ordinates in cases where the number of intervals is neither even nor a multiple of three. Both Simpson's and the trapezoidal rules furnish an arithmetical means of finding the value of J*ydx (see Fig. 67). If the value sought were fy^dx the same method might be followed only that in this case the square of each ordinate would be considered and so in the case of any function of the ordinates. The detailed methods of making the calculations outlined above form the subject of Theoretical Naval Architecture which is too large a subject to be treated here. The reader is referred, for complete information regarding these matters, to such books as Attwood's "Text Book of Theoretical Naval Architecture." Robinson's " Naval Construction." Biles' "The Design and Construction of Ships." Peabody's "Naval Architecture." White's "Manual of Naval Architecture." Reed's "Stability of Ships." After the displacement, weight and stability calculations have been made, it may be found that certain shifts of weights, or even changes in the lines will be required in order to give satisfactory conditions of draft, trim, buoy- ancy, and stability. When these changes have been made 10 146 PRACTICAL SHIP PRODUCTION the calculations must be made over again in whole or in part. When the locations arid amounts of weights have been so adjusted, with respect to the lines, as to give satisfactory conditions, the principal plans are completed and the cal- culations for strength outlined on pages 25 to 27 are made. Such changes in weights, as may be found necessary as a result of these calculations may possibly result in the ne- cessity for further changes in the preceding calculations although this is not usually the case. 6. DETAIL PLANS AND SPECIFICATIONS The remainder of the design of the ship consists in the preparation of detail plans for the various minor parts, fittings, installations, etc., not shown in the principal plans, but necessary for the work of the shipbuilders. The num- ber and extent of these plans vary with the size and type of ship and the requirements of the prospective owner. In addition to the plans specifications are prepared which supplement the plans, and embody instructions to the builders as to the quality and sizes of the various materials to be used in the construction of the ship, and numerous other requirements to be complied with that are not fully shown in the plans. Based upon the plans and specifications there are also usually prepared, under the direction of the designer, lists of materials that will be required for the building of the ship. CHAPTER V SHIPYARDS 1. SITE FOR A SHIPYARD The site for a shipyard must be, of course, on the edge of some body of water of sufficient depth, and extent, to per- mit of safe launching of the ships after they have been built. It must also be so chosen as to permit of expeditious deliv- ery of the large and heavy materials required for building the ships, and should, if possible, be located not too far from suitable housing facilities for the workmen who are to be employed. Not only must there be sufficient water for launching the ships but also there must be a channel leading to the sea through which the ships may pass after they are entirely completed and outfitted. The area of ground necessary for a shipyard depends not only upon the number and size of the ships to be built but also upon their character, and how much of the work of fitting out and equipping the hulls is to be done entirely by the shipbuilder and at the shipyard. Some shipbuilders do practically all of the work, including the manufacture of engines, boilers, large castings, forgings, etc., in their own yards. Others confine their work almost entirely to the hull proper and purchase a large amount of material, ready for installation, from other concerns. In the case of " fabricated ships" even the parts of the hull are made at a distance and shipped to the yard for erection and assembly. No fixed rule can therefore be given regarding the acreage required for a shipyard, but this can be roughly determined, having due regard for the conditions to be met, by compari- son with other established yards. 2. THE BUILDING SLIP AND LAUNCHING WAYS The first essential in a shipyard is the place in which actually to build the ships. The hull of a modern ship, 147 148 PRACTICAL SHIP PRODUCTION when ready for launching, weighs a good many hundreds, or perhaps thousands, of tons and this large and relatively concentrated weight must be properly supported. It is therefore customary, in most cases, to strengthen the ground on which a ship is to be built by means of piling. In some cases as where the site of the shipyard is over a stratum of rock, or where the ground is very hard- piling is not necessary, but where the ships to be built are large, and except in rare instances, piling is commonly used. Sometimes the piling may be of reinforced concrete, but more often it is of wood. In addition to the driving of piles it is very often nec- essary to do considerable excavating and dredging in order to provide proper facilities for the building and launching of ships. Fig. 68 shows, in cross section, the site of a shipyard before and after the dredging, excavating and pile driving have been done. The space over which a ship is built is called the building slip. This ground except where rocky, or very hard, is reinforced by the piles, which are driven deep into the ground until they strike gravel or other firm subsoil. The keel line of the ship, while being built, is usually nearly normal to the line of the water's edge, although, in some cases, where the breadth of the water into which the ship is to be launched is limited, it is necessary to have the building slip inclined to the line of the water's edge (or even broadside launching may be necessary. See page 157) . The piles are driven in rows at right angles to the keel line. The spacing of these rows varies with the weight of the ship and hardness of the ground. In most cases it is about four feet although in some cases it may be as great as six feet. For battleships and large, heavy vessels it may be as close as two feet. There are three lines along the building slip that must be strongly reinforced by piling : the line of the keel, which takes a large part of the weight of the ship during the proc- ess of construction, and the two lines, parallel to the keel line on which, later, are laid the launching ways, heavy SHIPYARDS 149 is O *-( ^ tons per square foot. SHIPYARDS 153 Pressures of 2^ tons per square foot should never be ex- ceeded. The materials commonly used are yellow pine, elm, or oak. A cross section of a ship on the launching ways is shown in Fig. 71. The launching ways must be extended for some distance beyond the water's edge, together with the necessary sup- porting piles, so that there will be several feet of water (from 4 or 5 feet for smaller vessels to 10 or 12 for larger ones) over the end of the ways when the ship is launched Cross W HlJiW^^ Pi ' toB S^YyV/i^'^/t YVyMS' T V^ FIG. 71. Ship on launching ways. (see Figs. 68, 72 and 73). The rise and fall of the tide must, of course, be considered in this connection. In designing the building slip, with regard for both the keel blocks and launching ways due consideration must be given to the contour of the ground, and of the bottom of the water, and to the shape, weight and size of the ship to be built and launched. Certain calculations should be made regarding the probable behavior of the ship when launched in order to make certain that the launching ways, especially 154 PRACTICAL SHIP PRODUCTION SHIPYARDS 155 at their lower end, have been properly designed. These investigations must be made, even before the commence- ment of the actual building of the ship, since the driving of the piling, the necessary dredging work involved, etc., usually must all be accomplished before the laying of the keel. ' In Fig. 72, top view, is shown a sectional profile of the ground and water with piling, launching ways and ship on the ways, ready to be launched. The launching con- sists in permitting the ship, with supporting cribwork, to slide down the launching ways into the water. As soon as the stern enters the water there is added, to the upward force given by the support of the launching ways, the upward force of buoyancy due to the amount of the hull that is submerged. As the downward motion of the ship continues, the amount of this force of buoyancy increases, but after the stern passes the end of the launching ways it loses the upward support of these ways, and if the force of buoyancy is not great enough the ship may "tip." Such "tipping" is shown in the middle diagram of Fig. 72, and should always be avoided, since the ship would very probably be seriously damaged by the great con- centrated force thus brought to bear on the portion of the hull directly over the end of the launching ways if the ways themselves were not crushed in, thus also endangering the hull. On the other hand if a certain amount of the support of the ship is not soon transferred from the launching ways to the buoyancy of the water beyond the end of the ways, the ship may "pivot" about her bow or a point near the bow. Such " pivoting" is shown in the bottom view of Fig. 72. In the case of a very long, light vessel, like a destroyer, premature pivoting might cause excessive longi- tudinal stresses in the hull and result in serious damage. (Pivoting at the proper stage of the launching is not only not dangerous, but is desirable.) Both tipping and pivoting must therefore be carefully considered and the launching ways must be extended far 156 PRACTICAL SHIP PRODUCTION enough into the water to prevent tipping and not so deeply as to cause premature pivoting. The ways should be so designed, however, that the ship will pivot after a good proportion of her length is in the water. It is necessary to provide sufficient depth of water to prevent the bow from striking bottom during launching. As will be seen in Figs. 68 and 72, the depth of water just beyond the end of the launching ways should increase quite rapidly. Summary of Requirements of Building Slip, Launching Ways, Etc. The most important points to be looked out for in laying out the piling, etc., for a building slip may be summarized as follows: 1. The piles must be so arranged as to give sufficient support for the launching weight of the hull. 2. There must be sufficient breadth of water in the line of the launching ways, produced, to prevent the ship from striking the opposite bank when launched. 3. There must be sufficient depth of water along this line so that the hull will not strike bottom when launched especially just beyond the end of the launching ways. 4. The distance apart of the launching ways must be such that the weight of the ship will be well transmitted through heavy vertical longitudinal members of the hull, and properly distributed athwartships. 5. The launching ways must not be too far apart, because, owing to the fineness of the ends, a sufficient amount of the length might then not be supported, and too much transverse stress thus be caused. 6. The launching ways must not be too near together which would cause undue transverse stresses and decreased stability. 7. The launching ways must extend far enough into the water to prevent tipping. 8. The launching ways must not extend too deeply into the water or otherwise pivoting may occur too soon, SHIPYARDS 157 9. The height of the keel blocks must be sufficient to permit ready access to the ship's bottom for men working on her construction. 10. The height of the launching ways must be such as to permit an unobstructed slide of the ship down them when launched. (For additional information on this subject see Chap. VII, Sect. 7.) In the great majority of shipyards the building slips and launching ways are arranged in the manner just described, but in some yards, notably those on the Great Lakes, ships are launched broadside on, being built with their keels parallel to instead of perpendicular to the water front. In such cases instead of two there are laid a number of launching ways usually at 10 or 15 foot intervals along the length of the ship and they are given a much greater declivity than ways for end launchings. One of the advantages of this method is that, due to her striking the water broadside on, the ship is checked quickly, and does not require a broad expanse of water. One of the disadvantages is that a much greater extent of water front is required, which on the seaboard, where water front is usually costly, may be a serious drawback. In the shipyard shown in Fig. 73 about four times as much water front would be required if the 28 ships were all to be built at the same time for broadside launchings instead of as shown. 3. YARD LAY-OUTSHOPS, BUILDINGS, ETC. In laying out a shipyard it is important to remember the various processes in the building of a ship, from the time that the raw material is received in the yard until the time when it is secured in place in the vessel. Provision must be made for stowing the material until it is needed, and for " fabricating " it, or fashioning it to the shapes and sizes necessary for its assembly in the ship. The layout of storehouses, stowage spaces, shops, etc., should therefore be so arranged as to require 158 PRACTICAL SHIP PRODUCTION the minimum amount of transporting and handling of both raw and fabricated material. This is not a simple matter, since so many different elements enter into the problem, but certain salient points may always be looked out for. In general, the route to be followed by the structural steel from the stowage racks should be in a nearly straight line by way of the laying out shed, punching and shearing shed, and fabricating shop to the building slip, with as short distances between each as possible. A similar principle applies to the engine parts which should go from foundry or forge, via machine shop and erecting room to the ship. Means for transportation between these various points and for handling and placing heavy weights on the ship must also be provided and the more complete the equipment of a yard in this respect, the more efficient will be its operation. For transporting large quantities of raw materials, or heavy forgings, castings and machinery parts about the yard ordinary railroad standard gauge tracks are usually laid, with suitable spurs, switches and connections, if possible, to the local railroad tracks. The yard should be equipped with a certain number of railway locomotives and freight cars of its own. For smaller weights narrow gauge tracks are provided on which small flat cars may be pushed by hand. Motor trucks are also often employed. In the different shops various overhead and jib cranes are used for local handling. A well-equipped yard should also have a number of locomotive cranes capable of lifting, transporting, and handling weights up to from ten to twenty tons. These should run on the standard gauge railway tracks. Large traveling cranes are also very desirable for ship- yards of any importance. These run on specially con- structed tracks of very wide gauge and are capable of negotiating very large weights of fifty tons or more. These are especially useful in installing engines, boilers, armor, and other heavy weights in large vessels alongside of SHIPYARDS 159 the fitting out piers, at which the ships are moored after launching and prior to final completion, and with at least one of which every important yard should be supplied. One large floating derrick or crane capable of handling very heavy weights (100 to 150 tons) is also very desirable, although these are, of course, very costly and not possessed by many shipyards. For handling and erecting material in place in the ship on the building slip it is necessary that certain other cranes or derricks be provided. Various types are in use but all should be so arranged that a weight may be lowered over any point of the ship's hull for each building slip or berth. One method is to have a number of fixed masts or derricks each equipped with one or more booms operated by hoisting engines. These derricks must be more or less numerous since each can handle material over only a limited circle (see Fig. 73). A better, but more expensive, arrangement, is to have high trestles running parallel to the centre line of the building slip for traveling cranes which may be either of the canti- lever, overhead, or gantry type. A birdseye view of the shipyard of the Submarine Boat Corporation is shown in Fig. 73, in which will be seen the building slips, launching ways, fitting out piers, derricks, a large cantilever crane, shops, buildings, railway tracks, etc. This yard, being designed to build " fabricated" ships, does not have the variety of shops found in some yards. The buildings, etc., necessary for a shipyard usually include the following: 1. Buildings for offices, drafting rooms, etc. 2. Store houses and plate, angle, and other racks. 3. Power house (unless power is furnished by outside plant). 4. Mold loft. 5. Bending slabs. 6. Laying out, punching, and shearing sheds. 7. Fabricating and erecting shops. 8. Smith shop. 160 PRACTICAL SHIP PRODUCTION SHIPYARDS 161 9. Pattern shop. 10. Foundry. 11. Machine shop. 12. Plumbers' and pipefitters' shop. 13. Joiner shop. 14. Shipwrights' and sparmakers' shop. 15. Coppersmiths' shop. 16. Sheet metal shop. 17. Boiler shop. 18. Sail loft. 19. Rigging loft. 20. Electrical shop. 21. Pickling, galvanizing and plating shops. 22. Paint and varnish shop. 23. Boat shop. 24. Upholstery shop. Among these the following may be noted especially: Storehouses are necessary in considerable variety and should be located conveniently to the shops requiring the largest quantities of the materials stored in each. Plate racks should be provided so that plates may be stowed on edge by various sizes so as to be readily accessible. This is usually accomplished by means of posts or metal bars set in concrete foundations, against which the plates may lean. For angles and other shapes a good arrangement is to have vertical metal posts with horizontal arms extending out on each side at various heights, the upper ones usually being shorter and each successive arm being slightly longer than the one above. The mold loft is a building or shed of great horizontal extent which permits of its having a large continuous floor of sufficient size to have drawn on it the lines of the ship to full scale. The plans of a ship to be built are furnished to the mold loft by the drafting room, and from these plans the workers in the mold loft, called loftsmen, lay down and fair up, to full scale, the lines of the ship, and make templates for laying out the material for the hull. Templates are thin wood or paper patterns which show the size, shape, locations and sizes of rivet holes, and other particulars of the parts to which they apply. 11 162 PRACTICAL SHIP PRODUCTION The bending slabs are heavy rectangular cast iron blocks or slabs, square, or nearly square, and usually five or six feet on a side and from 2 or 3 inches to 5 or 6 inches thick placed together, side to side, and end to end, so as to form a large horizontal flat surface on top of which the frames, reverse frames, and other similar parts of a ship can be bent to their proper shapes. The slabs are usually laid on top of heavy timbers which thus raise them a foot or more above the ground or floor of the shed in which they are located. They have small holes (usually about 1J^" square) running vertically through them, so that their upper surface presents a lattice-like appearance as shown in Fig. 78. These holes are used for the insertion of dogs, pins, etc., by means of which the frame bars are clamped down and held to the proper shape while being bent and beveled. Close to the slabs are located long furnaces, of the re- verberatory type, usually oil-burning, for heating the frames. The laying-out shed should be located near the mold loft. Templates from the latter are used for laying out the various plates and shapes for fabrication in this shed which often forms a part of the punching and shearing, or as it is sometimes called, the plate and angle shop. In this latter shop are located the various machine tools used for punching, shearing and planing, etc., the various steel parts of the hull that have been marked in the laying out shed for that purpose. The fabricating and erecting shop may also form a part of the plate and angle shed or it may be in another building close by. Here various small portions of the ship's struc- ture, such as floor plates, hatch coamings and covers, water-tight doors, skylights, trunks, etc., are assembled and riveted up so that they may be taken to the ship ready for installation. The smith shop usually has both small forges and anvlis for hand forgings, and steam hammers and large furnaces for heavy work, and drop forgings. The extent of the SHIPYARDS 163 forging work varies in different yards, some having many of the larger forgings made by outside concerns. In the joiner shop a great part of the wood work of the ship is done. Furniture, ladders, wooden doors, sky- lights, chests, lockers, gangways, gratings, and a large number of other miscellaneous wooden articles are made here. In the shipwright shop material for wood decks, founda- tions, masts, spars and various materials for scaffolding, stagings, blocking, shores, cribbing, wedges, etc., is prepared. The nature of the work done in the other shops mentioned is indicated by their names. In many of these shops the work done is similar to that done in the same shops in other manufacturing plants, there being in a modern ship much of the same equipment that is found in buildings on shore. 4. SHIPYARD MACHINE TOOLS, ETC. The principal processes in the fabrication of the steel material that forms the hull proper are as follows: 1. Plate bending and straightening. 2. Shearing. 3. Planing. 4. Punching, drilling, and reaming. 5. Countersinking. 6. Flanging. 7. Sawing. 8. Forging and welding. 9. Punching large holes, notches, etc. 10. Cutting with the oxy-acetylene torch. 11. Joggling. 12. Hydraulic riveting. 13. Frame bending, etc. 14. Furnacing plates. 15. Beam bending. Plate Bending. Certain plates of a ship such as those at the turn of the bilge have a cylindrical curvature. In order to give such curvature to the flat plate as received in stock from the rolling mill, it is passed through a large 164 PRACTICAL SHIP PRODUCTION machine called the plate bending rolls, the essential parts of which are three long heavy rolls as shown in section in Fig. 74. The axis of the larger upper roll can be adjusted vertically so as to give, within reasonable limits, any de- sired degree of curvature to the plate. The length of the rolls should be sufficient to take the longest plates that it is expected will ever have to be handled. Thirty-six Plate PLATE BENDING ROLLS Punch Plate Die PUNCH COUNTERSINK Plate ANGLE SHEAR PLATE JOGGLING MACHINE FIG. 74. Operation of shipyard machine tools. feet may be considered as a fairly great length, while 26 feet or even less may be sufficient for some yards. The length is, of course, limited by the difficulty of securing rolls of sufficient strength, and the need for great length depends upon the capacity of the rolling mills furnishing the plates. Plate straightening rolls consist simply of a number of parallel cylindrical rolls through which a plate may be SHIPYARDS 165 passed to remove any unevennesses and make it perfectly smooth and flat. Shearing. This is the process of trimming off the edges of plates, ends of bars, etc. It is accomplished by means of a machine called a shears which consists essentially of a large shear or knife that oscillates, as a rule, vertically. Its operation is illustrated in Fig. 74. Each stroke cuts only a limited portion of the plate which must be moved along as the various strokes are taken. For shearing angle bars transversely a special type of machine must be employed (see Fig. 74), and also for channels, Z-bars, etc., although the principle is the same. Shears, especially if slightly dulled, or not properly aligned, have a tendency to tear as well as to shear the material, and as a result the sheared edge usually has a slight burr. Planing consists in smoothening up the edges of plates, shapes, etc., so as to remove the burr, and give a plane, flush edge for purposes of appearance, calking, etc. This is accomplished by means of a machine called a plate planer in which the plate or shape is clamped and trimmed off by means of a traveling cutting tool. The planer should have about the same length as the bending rolls. Punching is the process of putting holes for rivets, bolts, etc., in various plates and shapes. This is accomplished by machine tools similar in their operation to shears (see Fig. 74). The plate or other piece to be punched is placed upon a die of slightly larger diameter than the punch which, as it moves down with great force, punches out a piece of metal and thus forms a hole. As in the case of shearing a slight burr is formed on the under side of the plate or shape punched and also, on account of the ductility of the material, the hole is slightly conical, instead of being a true cylinder, the larger diameter being at the lower end of the hole. It is to fit such holes that the coned neck rivets shown in Fig. 21 are designed. In the lowest sketch in this figure is shown the faying surface between two plates riveted together. In order for the rivet properly to fill the rivet hole the plates, if punched, should be 166 PRACTICAL SHIP PRODUCTION punched from the faying surface, so that the coned neck of the rivet will fit the cone of the hole caused by the punch. It is usually considered better practice to have the rivet holes true cylinders (in which case straight neck rivets are used), and with this object in view they are often drilled. This is, of course, more expensive and takes much more time than punching and the same result may be accomplished by reaming out a hole to the proper size after it has been first punched to a slightly smaller size. A reamer is a fluted, revolving spindle tapered at the end, which is inserted into a hole and gradually forced further into it, the revolving flutes cutting away some of the metal as the tool advances. Reaming has the added advantage of removing the small portion of material just around the hole that has been slightly weakened by the action of the punch. Countersinking is the process of giving to one end of a rivet hole a conical form, a portion of the metal being re- moved, as shown in Fig. 74, by a revolving tool with two or more cutting edges. This is done where countersunk rivets are to be driven for water tightness, or to be given a flush surface. The countersinking tool is mounted in a movable arm so that it can be quickly adjusted to any desired location over the plate which is supported on a fixed table by means of ball rollers, so that it also can be quickly adjusted. Flanging is the process of bending a portion of a plate so as to give it a flange or portion turned to one side. This is often done to brackets, etc., to give them extra stiffness, and to keel plates, garboard plates, etc. (see Fig. 75). It is accomplished by means of a powerful flanging machine consisting essentially of a large roller mounted on heavy swinging supports. Sawing is necessary for cutting off certain heavy shapes, such as rounds, half rounds and other special or heavy shapes that cannot be readily sheared. It is usually accomplished SHIPYARDS 167 by means of a special circular saw designed for cutting metals. Forging and welding is necessary in fabricating special parts of irregular forms, such as staples, tapered liners, collars, coaming and other boundary bars, etc., which must be heated and worked by hand (see Fig. 75). Punching of manholes, etc., may be done by a special powerful hydraulic manhole press which cuts out a large hole in a plate in one operation. A similar operation with a Flange FLANGED PLATE STAPLING Joggle- JOGGLED PLATE* Liner - TAPERED LINER FIG. 75. Fabricated parts. specially shaped punch is employed for notches in plates for angle bars, etc., penetrating them at right angles. Cutting with the oxy-acetylene blow pipe or torch is usually employed instead of hydraulic manhole punching, notch punching, etc. Irregular holes or holes of practically any desired shape can be quickly cut by this method (see Chap. VII, Sect. 5). Joggling consists in offsetting the edge of a plate or a portion of the length of a shape to avoid the use of liners. In Fig. 75 is shown a joggled plate, and, in Fig. 74, the operation of one type of machine that does the joggling. 168 PRACTICAL SHIP PRODUCTION Punching and shearing machines are often provided with dies for joggling. Hydraulic riveting is accomplished by means of a heavily built (and, usually, portable) machine consisting essentially of two massive jaws, hinged so as to be closed together by hydraulic power thus forming and clenching a rivet in one movement. Frame Bending and Beveling. This work is done on the bending slabs, previously mentioned. A portion of a bend- ing slab is shown in Fig. 78. From the mould loft is made a template to which a piece of soft iron, known as a set iron is bent. This is secured to the bending slab by means of large dogs, as shown. The angle bar to be bent is first heated to a red heat and then bent around the set iron. It is held in place, as bent, by other dogs, not shown in the sketch. A tool called a "moon bar" or "squeezer" is used to force the bar around where the curvature is greatest. While the frame bar is still hot it is beveled by having the angle between its two flanges opened or closed to the proper amount at each point of its length. This is done by means of a special tool (a beveling lever) with a wrench-like jaw that can be fitted over the vertical flange, or by a few light blows of the sledge hammer (see Fig. 79). The other flange, during this operation is secured fast to the bending slab by dogs. Furnacing of Plates. Certain plates of the shell plating are undevelopable, as for example the boss and oxter plates. Special molds have to be made for these, built up of light wood to the actual form of the ship, from which heavy metal beds are made, of plates and angles, in which the plates after having been heated red hot are laid and ham- mered into shape. Such furnaced plates are made slightly thicker than would otherwise be necessary in order to com- pensate for possible loss in thickness and strength caused by the furnacing and shaping. In the preceding paragraphs have been described the more important processes in ship construction that require the use of machine tools, and the tools most commonly SHIPYARDS 169 used have been mentioned. Some of these tools are abso- lutely essential to shipbuilding work, while others may be dispensed with and their functions performed, though in a less efficient manner, by the others. The exact equipment necessary for any given shipyard is difficult to determine and varies with the size of the yard, the capital available, the type of ships to be built, etc. The following may be considered as a proper equipment for a first-class yard of moderate size: Bending rolls (1 large; 1 or 2 small). Plate mangles or straighteners (2). Plate planers (2 or 3). Punches (6 or 8). Shears (6 or 8). Angle and other special shears (3 or 4). Flanging machine. Joggling rolls. Hydraulic press. Radial drilling and countersinking spindles (6 or 8). Steam hammers (several). Hydraulic riveting machines (2 or 3). Bending slabs. Plate furnaces (2 or 3). Angle furnaces (2 or 3) . Beam press. Scarphing machine. The above applies only to the larger machine tools used primarily for hull construction and takes no account of a great variety of miscellaneous small portable tools and machines, or of tools in the woodworking-, plumbers-, machine-, smith-, and other auxiliary shops. 5. PERSONNEL OF A SHIPYARD The organization of a shipyard is commonly based upon a division of the work into two main parts : that pertaining to the hull, and that pertaining to the machinery. The plans for the hull and its fittings and equipment, when required to be made in the yard, are prepared by a staff of designers and draftsmen entirely separate and distinct 170 PRACTICAL SHIP PRODUCTION from those preparing the plans for the engines, boilers, auxiliaries, etc. Similarly the work of manufacturing, erecting, testing and installing the machinery is largely done by a different force of mechanics from those who build the hull and make and install its fittings. Considering the shipbuilding or hull end, there will be found in a well-equipped shipyard, workers in the following occupations and trades : designers and draftsmen, loftsmen, layers-out, workers in the plate and angle and fabricating shops, frame benders, anglesmiths, furnacemen, shipfitters, erectors, laborers, bolters-up, etc., drillers, reamers, riveters, holders-on, heaters, passers, chippers and calkers, testers, shipwrights or ship carpenters, joiners, plumbers, pipe- fitters, shipsmiths, drop forgers, heavy forgers, sailmakers, riggers, sheet-metal workers, machinists, wood calkers, coppersmiths, galvanizers, pattern makers, molders, melt- ers, chippers and other foundry workers, painters, and var- nishers, masons, electricians, boat builders, not to mention all of the miscellaneous auxiliary trades, such as janitors, watchmen, laborers, helpers, drivers, teamsters, chauffeurs, crane men, firemen, locomotive engineers, etc. Workmen of each of the skilled trades all have helpers to assist them and in each of these trades there are one or more foremen or " bosses, " and various sub-foremen or supervisors, ranging from the bosses down through assist- ant-bosses, quartermen, leadingmen, etc., to " snappers" each of whom is in charge of a certain group or unit of mechanics. Designers and Draftsmen. These are the men who make the necessary calculations, draw the plans, and pre- pare the specifications from which the ship is to be built. They should have both practical and theoretical knowl- edge of naval architecture especially the latter, since upon a correct knowledge of the theoretical principles governing the design of a ship depends the success of the ship. No matter how well she may be built, a poorly designed ship may be of little practical value and may even- be a source of great danger. SHIPYARDS 171 Loftsmen. The loftsmen are the men who take the plans of the ship as furnished by the draftsmen, and by laying them down to full scale on the mold loft floor, make tem- plates from which the material that is to form the hull can be marked out and fabricated. Their work requires much of the same knowledge that is essential for draftsmen, and in addition a considerable amount of practical expe- rience with shop and yard practices. Layers -out. From the templates furnished by the loftsmen various plates and shapes must be laid out for shearing, planing, punching, bending, flanging, beveling, rolling, etc. This work is done by layers-out who are usually possessed of the same qualifications as shipfitters. Their work, however, is confined to the laying-out shop, whereas shipfitters usually do their work largely on the ship. (See under Shipfitters, below.) Workers in the Plate and Angle Shops. After the material has been laid out it is sent to the various machine tools where the necessary punching, shearing, planing, countersinking, etc., is done. A considerable variety of workers operate these tools, although usually the work is such that men capable of operating one tool can also oper- ate several others. Among the trades engaged in this work the following are found: manglers or plate straighteners, drillers, jogglers, punch and shear operators, plate rollers, countersinkers, acetylene cutters although not always called by these names. The operations at most of these machine tools consist in guiding the plates or shapes, sup- ported by various types of cranes and hoists, into position, and then pulling the necessary lever or making the neces- sary electric contact to cause the machine to perform its function in each case. The quality of work and the speed with which it is done is largely dependent upon the skill of the workman. This skill can be gained only by experience. Frame Benders, Anglesmiths, Furnacemen, Etc. These and similar names apply to the workmen who do the working of plates and shapes to special forms that must be done with the material red hot. All of this work 172 PRACTICAL SHIP PRODUCTION partakes of the nature of blacksmith work. The greater part consists in bending and beveling frame and reverse frame bars, making staples, collars, coaming angles, shaping special plates of the shell, etc. It is evident that such work can be done properly only by men of good phy- sique, and skill, that is obtained only as the result of long experience. Shipfitters. The shipfitting trade is the one metal worker's trade most closely associated with shipbuilding. The shipfitter, with modern steel vessels, corresponds to the shipwright with the old wooden ships. In general, the duties of a shipfitter are to lay out or fit the various members of the ship's hull. It will be noted that a large amount of the material that enters into the hull of a steel ship is laid out and fabricated from templates furnished by the mold loft. The laying out of all steel material not so handled is, in general, the province of the shipfitter. It is, of course, possible by following carefully prepared plans, and requiring the most careful and accurate workmanship, to get out, in advance, in the shops, all the parts of a ship. In some shipyards this method is very closely approached, but in practice it is found to be very difficult to fabricate all parts in ad- vance so that they will fit together properly when as- sembled. Therefore it is usual to fabricate a certain amount of material from templates and plans, but to leave a certain remainder to be made specially from templates prepared by shipfitters to fit other parts after these other parts are in place in the ship. For example, after the frames have been erected certain plates of the shell are usually laid out from templates actually " lifted" or made in place on the portion of the frames that is to be occupied by those particular plates. The edges of the plates and the exact positions and sizes of the rivet holes in each case can thus be transferred directly to the template from the work on which the plate for which the template is made is to fit. Such a template consists of thin strips of soft wood, nailed or tacked together to form a skeleton SHIPYARDS 173 " pattern" of the plate, on which is marked all information necessary for fabricating the plate. Occasionally, in the case of lighter members, it is found convenient and advisable to place the steel material itself in position in the ship, mark it off, and send it then to the shop for fabrication. In other cases the steel material may be laid off directly by the shipfitter from a plan- without the use of a template. Some of the men skilled in ship fitting work are usually assigned to duty as " layers- out," marking off the plates and shapes for fabrication from mold loft templates. The shipfitter' s trade is one calling for both skill and intelligence, combined with a certain amount of practical mathematical knowledge and an ability to "read" plans. Shipfitters are more or less concerned with the production of practically all the main structural members of the hull. Some of the simpler parts which are usually laid out by the shipfitters (or fitters-up as they are sometimes called) are described below, in order to show, concretely, what their duties are, even although some of these parts have been previously referred to. These are illustrated in Fig. 76. A bosom piece is a short section of angle bar used to con- nect the ends of two other angle bars that butt together. The heel of the bosom piece is planed off to fit into the bosom of the other two bars and the toes of the bosom piece are planed off so as not to project beyond the toes of the bars, as shown. A clip is simply a short piece of angle bar used to connect two other parts at right angles, or nearly so, as shown in the figure. A bracket is a flat plate, usually of triangular shape used to tie together and stiffen two plates or other flat members meeting at an angle. In Fig. 76 is shown a bracket flanged on its edge, for additional stiffness, and having a lightening hole in it, to save weight, connecting two plates that are at right angles to each other. A butt-strap (see Fig. 76) is a piece of plate used to con- 174 PRACTICAL SHIP PRODUCTION nect two plates that butt against each other. The butt- strap makes a lap-joint with each plate. Sometimes a butt-strap is fitted on each side of the two plates, in which case the straps are called double butt-straps. According to the number of rows of rivets butt-straps are called Toe planed off Bosom Piece t ^xButt of Angles Heel planed off BOSOM PIECE CLIP CONNECTING TWO PLATES ] 1 1 '; t v j , ^ late V- ButtStra P \ late , /\ fr~\ /~s /~^ &xsm mAmavz i/ YSf/YSSSSSSL FLANGED BRACKET (riveting omitted ) BUTT STRAP TAPERED LINER (riveting omitted) FIG. 76. Shipfitting work. Liner single-riveted, double-riveted, treble riveted, etc. The one shown in Fig. 76 is a single, double-riveted butt-strap. Liners are strips of plating fitted between frames, beams, etc., and the plating laid on them to bring the plating flush with other plating over which it laps. Liners may be SHIPYARDS 175 either straight or tapered. In Fig. 76 is shown a tapered liner. The sketches just described will serve to indicate the character of the work done by shipfitters, these being, however, some of the simpler parts laid out by this trade. Erectors, Laborers, Bolters-up, Riggers, Etc. After the various members of the ship's hull have been fabricated they are transported to the building slip, hoisted into place by cranes or erected by hand and bolted in place, the bolts being inserted through rivet holes to secure the parts for riveting. Only a portion of the rivet holes need to be so filled, the rest being left empty. The workmen who do this work are variously called riggers, laborers, helpers, bolters-up, regulators, erectors, etc. In order to make the various parts fit it is sometimes necessary to draw them together so that the rivet holes overlap exactly, or are fair. This is done by means of a small tapered pin, called a drift pin which is driven into the rivet holes until they are in line (see Fig. 81). Excessive use of the drift pin is an evidence of poor workmanship and should not be tolerated. The bolts are saved after they have served their purpose and used over and over again, and, as the lengths vary, it is customary to have on hand a large number of washers, made by punching holes in small rectangular pieces of plate, for use with these bolts to save labor in screwing up the nuts. Drillers and Reamers. After the hull members have been bolted up in place it is usually necessary to drill certain rivet holes that it is not practicable to have punched before erection, and to ream out the holes that have been punched, in order to give smooth, fair holes suitable for the riveting. This work is done by the drillers and reamers. Drillers also are employed to tap certain holes designed for bolts or tap-rivets. Riveters, Holders -on, Heaters, Passers. The drillers and reamers are followed by the riveters, who drive the rivets that form the fastenings of the various members. Riveting may be done either by hand or by pneumatic 176 PRACTICAL SHIP PRODUCTION hammers, the use of the latter now being the most common practice. A riveter works in a gang, which consists, besides himself, of a holder-on, heater-boy, and one or more rivet-passers. The heater boy places the cold rivets in a small portable forge in which they are heated to a cherry red. They are removed from the forge as needed, and taken by the passer (or passers) to the holder-on who inserts each rivet in the proper hole, after removing a bolt, if necessary, from the opposite end to that at which the riveter stands. The holder-on then shoves the rivet into the hole until the head takes up well against the plate or shape and holds it there with a heavy holding-on hammer or dolly- bar. The riveter then drives the point of the rivet against the other side of the members to be connected, flattening it out and clinching it so as completely to fill the rivet hole. This work must be done while the rivet is hot. Riveting requires considerable skill and great strength and endur- ance. Calkers, Chippers, and Testers. All plated surfaces that form boundaries of compartments into, or from which water, oil, etc., must not leak, require calking. This consists in tightly closing the joints between the connecting parts through which leakage might occur. As in the case of riveting, calking may be done either by hand or pneu- matic tools the tools in the case of calking, however, being chisels instead of hammers. These tools are used to force the steel material of one part against the surface of the adjoining part. This work is done by the calkers who also are employed at times to do chipping which consists in the use of chisels, to trim edges, cut holes, etc., the same pneu- matic hammer being used as for calking, but with a differ- ent tool. These workmen are therefore often called chippers and calkers. After the calking is completed the tightness of the joints is tested by filling the compart- ment with water or compressed air, and any leaks thus discovered are made good. This testing is also usually done by the chippers and calkers, who are therefore some- times called testers. SHIPYARDS 177 The draftsmen, loftsmen, layers out, fabricating shop workers, shipfitters, erectors, drillers, riveters and calkers comprise those workers who are intimately connected with the building of the hull proper of a steel ship. The follow- ing trades, however, also have considerable to do with shipbuilding : Shipwrights (or Ship Carpenters). Who prepare keel blocks, wedges, shores, staging, launching ways, scaffold- ing, ribbands, etc. the auxiliary wood work in connection with building the ship and make and install wood decks, masts, spars, foundations, etc. Joiners who make and install the lighter wooden parts of the ship, such as wooden doors, partitions, windows, stairways, lockers, cold storage compartments, shelving, bulletin boards, furniture, etc. Plumbers and pipe fitters who do work on the various plumbing and piping systems of the ship. Shipsmiths and heavy, and drop -forgers who fashion the various fittings and other parts required to be heated and hammered in the smith shop. Sailmakers who manufacture the sails, awnings, etc. Riggers who make and fit the necessary rigging for the masts, spars, etc. (Not the same as the riggers who assist in erecting the parts of the hull). Sheet metal workers who roanufacture ventilation ducts, metal lockers, wire mesh partitions, sheet metal, sheathing, etc. Hull machinists who do the necessary fitting and in- stalling of steering gears, hull valves and zincs, operating gears, etc., etc. as distinguished from the machinists who are employed on the main engines and auxiliaries. Wood calkers who calk the seams of wood decks and planking. Coppersmiths who make copper pipes, kettles and other fittings. Galvanizers who galvanize or coat with zinc the outside surfaces of various steel and iron parts exposed to the weather. 12 178 PRACTICAL SHIP PRODUCTION Pattern makers who make wooden patterns from which castings can be made. Holders, melters and other workers in the foundry, where the castings are made. Painters and varnishers who have considerable work to do both on the ships and in their shop. The painters usually are the workmen who apply bituminous com- positions. Masons who install tiling in bath rooms, lavatories, galleys, laundries, etc., and apply portland cement in various out of the way pockets and other inaccessible parts of the hull. Electricians who install wiring and electrical equipment. Boatbuilders who make the boats that go with the ships. 6. MANAGEMENT Given a shipyard, with building slips prepared, shops, tools and other yard equipment complete, plans and specifications at hand, in order to produce ships efficiently there must be a, management, organized for guiding, direct- ing, and controlling the workmen, ordering the necessary materials, co-ordinating the work, etc., etc. The great factor in the expeditious and economical production of ships (as in all manufacturing enterprises) is management. The function of the management is to do the thinking necessary in order that the construction of the ships may proceed smoothly and expeditiously. The building of a ship may be divided into a great many elemen- tary tasks. In the final analysis each of these tasks repre- sents manual work that must be done by some particular workman or group of workmen. If it be assumed that these workmen have the skill, experience and physical condition requisite for the performance of their individual tasks, then the problem of the management becomes one of seeing that each and every one of these workmen is given working conditions that will permit of his work being done quickly and efficiently. SHIPYARDS 179 In order that such conditions may exist the following points must be looked out for: (a) Plans. The necessary plans and instructions must be at hand in order that the workman will have no doubt as to just what he is expected to do, and how it should be done. (b) Material. Material required for each task must be ready at the time that it is needed, and it must be of suitable quality and furnished in sufficient quantity. (c) Tools. The workman must be furnished with all necessary tools, and these must be kept at all times in satisfactory operating condition. (d) Working Conditions. In order for the workman to do his work properly he must have good light, ventilation, protection from the weather, etc. If he is using tools operated by compressed air suitable connections to the air supply must be provided. If he is working at night special electric lights must be rigged. The various problems to be solved in seeing that these four points are looked out for are much more difficult than would be thought at first sight, and the manner in which these problems are met will have a very important bearing on the efficiency of the shipyard as a whole. CHAPTER VI PRELIMINARY STEPS IN SHIP CONSTRUCTION From the time that it is decided to build a ship, even from plans already completed, up to the time when the keel is laid, and the work of actually building the hull is com- menced, there is always a considerable interval. In many cases a large proportion of the work is done before a single piece is erected on the building slip, the keel-laying being postponed as long as possible, in order that sufficient fabricated material may be on hand to permit the work of erection, when once started, to proceed rapidly. In every case a certain amount of preliminary work must be done before the building of the hull can be commenced. Few yards carry a stock of materials so large that at least some new stock does not have to be ordered when it is proposed to build a new ship. Unless the new ship is a duplicate of another previously built by the yard, and for which the molds and templates have been saved, a large amount of mold-loft work must first be done. In every case the material must be fabricated or made ready for erection. The preliminary steps in ship construction are therefore : 1. Ordering the material. 2. Making the molds, templates, patterns, etc. 3. Fabrication of the material. 1. ORDERING THE MATERIAL Assuming that the shipbuilder has been furnished with complete plans and specifications of the ship (or ships) that he is to build, the first step in the production of the ship is the ordering of the material. This usually includes a great many miscellaneous fittings and auxiliaries which 180 PRELIMINARY STEPS IN SHIP CONSTRUCTION 181 are usually delivered complete and ready for installation, and the type and quality of which are covered by the speci- ficationssometimes exactly and sometimes somewhat loosely but the principal material to be ordered is the steel for the hull. In ordering castings and forgings to be made by other concerns, complete working plans must be furnished with the order, showing exactly what is desired. The plates and shapes present the greatest difficulty since the sizes of each must be so specified as to allow for shaping and cutting to the proper finished size (which usually cannot be foretold with complete accuracy) while at the same time not allowing so much excess as to cause a serious waste of material. The shell plates, keel, stringers, keelsons, etc., are usually ordered from a wooden model, made to scale, on which these various parts are laid off accurately in ink. This is necessary since a ship's form is an undevelopable surface so that the plates cannot readily be shown in their true form in the plans. A certain margin of material must be ordered to allow for stretching, shrinkage and change of form due to working the plates to the proper form and size. This depends upon the experience of the person making up the order and the general quality of work- manship of the yard. Frames, reverse frames and other similar parts that have to be bent are girthed from the plans a certain number being thus actually measured and the girths of the inter- mediate ones being obtained by plotting curves through the points thus obtained. In bending, frames usually stretch slightly at the heel so that little if any allowance in excess of the girthed length has to be made. For deep members to be bent the girth should be taken along the neutral line. The material is usually ordered direct from the various structural plans, material schedules being prepared by the draftsmen, but if time permits, or if the templates are already at hand as in the case of a number of ships being 182 PRACTICAL SHIP PRODUCTION built from the same plans, a certain saving can be made by making up the material schedule from the full size templates, since the percentage of error is then less. The amount of scrap from hull material or the difference between the weight as ordered and as worked into the ship is usually about 10 percent of the total. Great care must, of course, be exercised in ordering ma- terial to see that all parts are considered and nothing over- looked in making up the order. It is also important to consider the times of delivery, and to see that orders are so placed that the various deliveries will be made before they are actually needed. Materials for keel, keelsons, bottom plating, and inner bottom framing will, of course, be needed before frames, deck beams, etc. Little is gained by having anchors arrive before stem and stern castings. 2. MOLDS, TEMPLATES, PATTERNS, ETC. As soon as the plans of the ship are completed the work of making molds, patterns, etc., may start, even in advance of the receipt of any structural material. Plans for castings are sent to the pattern shop for use in making the necessary patterns, or to the outside concerns from whom the castings may be ordered. In the mold loft the lines of the ship are drawn on the floor to full size either with chalk or with lead pencil. For this purpose long flexible strips of wood, called battens, are used which are held in place by large flat headed nails with very sharp points. The ordinates for the various curves are furnished in the form of tables of offsets, each ordinate, or offset, being given in feet, inches and eighths of inches. For example, the offset 19-7-6 means 19 ft. 7%'' \ Owing to the difficulty of obtaining exact accuracy in the plans it is usually found necessary to make numerous changes in fairing up the lines on the floor of the loft. After this has been done a revised table of mold-loft offsets is made for record and possible future use. In the lines as laid down in the mold loft appears every frame, these being, PRELIMINARY STEPS IN SHIP CONSTRUCTION 183 of course, much more closely spaced than the frame stations used in drawing the lines in the drafting room. The work of laying down and fairing up the lines on the mold loft floor is the same as that of the draftsman who made the plan of the lines, except that it is done on a large scale. It is, in brief, nothing more nor less than putting into practice the principles of descriptive geometry. The various details of this work form a study in themselves, and for a complete treatment of these matters the reader is referred to text books on the subject such as, for in- stance, Watson's " Naval Architecture." Loftsmen ac- quire their skill only as the result not only of study but also of actual experience in the loft. After the lines have been faired the scrieve board is made. This consists of a special section of wood flooring (often made in sections, and portable) of sufficient size to take the full size body plan of the ship. On this flooring is drawn the complete body plan showing every frame, together with inner bottom, decks, stringers, keel, keelsons, longitudinals, margin plates, plate laps, lines of ribbands and such other information as is necessary for the fabrica- tion of the various members. All of these lines are cut into the surface of the scrieve board by means of a sharp, V-shaped tool, called a scrieve-knife. This is done to prevent their being obliterated by the rough usage to which this board is subjected during the processes of making molds, templates, etc. The scrieve board is used for making the various molds of frames, beams, floor plates, etc., etc. These are usually made of strips of thin soft wood tacked together, and shaped to the form of the particular members that they represent. The terms mold and template are often used synonymously but the first applies strictly to shape, whereas a template in addition to having the form of the part also has marked upon it certain information, such as locations of rivet holes, edges to be sheared or planed, lightening holes, coun- tersinking, etc. Some templates are made of paper instead of wood, or even in some cases of light metal. Templates 184 PRACTICAL SHIP PRODUCTION that are to be used repeatedly are made more substantially than those that are to be used only once. Molds for furnaced plates that have curvature in three dimensions are built up specially of more substantial wooden pieces. oooooooo oo oooooo OO O O O.'-O O O O FRAME MOLD TEMPLATE FOR SHELL PLATE FIG. 77. Template and mold. Figure 77 shows a template for a shell plate and (to a smaller scale) a mold for a frame both made of strips of batten wood tacked together. The laying off and fairing of the lines on the mold loft floor and the construction of the molds and templates for PRELIMINARY STEPS IN SHIP CONSTRUCTION 185 the hull material that is to be fabricated in advance con- stitute the principal work of the loftsmen. In addition to this various battens are marked off giving certain dimensions and other information for use by the workmen in the fabricating shops. Bevel boards are also made by the loftsmen. These are small strips of batten wood on which are drawn lines which indicate the angle of bevel for each frame at certain fixed points along its girth. The obtaining of these bevels is accomplished by measuring on the scrieve board the distance between ad- jacent frame curves, taken normal to their curvature, and combining it with the fixed distance fore and aft between frames (or the frame spacing) so as to determine the angle of the small right angled triangle thus formed between each pair of adjacent frames. In order to give all frames an open bevel the bosoms of the forward frames "look" aft and of the aft frames look forward. 3. FABRICATION OF HULL MATERIAL Fabrication is the term applied to the various processes by which the raw material as received from the steel mills is laid off and fashioned so that it is formed into the various structural members of the hull, which, when erected, will fit together properly with their neighboring parts. Such parts of the hull as are ordered specially, or made in the yard, as forgings or castings require no special description, as the methods of making ship forgings and castings are no different from those of making such pieces for other purposes. Such finishing of these parts as is required is done after receipt of the rough castings either by machine or by chipping with hand or pneumatic chipping tools. The fabrication of the following parts is more or less pe- culiar to shipbuilding and will be described below: shell plating, plating of decks, bulkheads, inner bottom, etc., frames and reverse frames, floors, keels and keelsons, etc., deck beams, bulkhead stiffeners, brackets, bounding bars, coamings, etc. 186 PRACTICAL SHIP PRODUCTION Shell Plating. The flat plates of the shell present little or no difficulty. After being rolled perfectly flat, or mangled, if necessary, these plates are laid off from templates similar to that shown in Fig. 77. The centres of the rivet holes are centre punched on the side of the plate from which to be punched and a small white circle is marked with paint or chalk, to make the position of each more conspicuous. In some cases especial pains are taken to have these small circles exactly concentric with the centre punch marks but this is not absolutely necessary, provided the centre punch mark is correctly located in each case. If holes are bored in the template, as shown in Fig. 77, a special tool is used which consists of a short hollow cylinder of just the proper outside diameter to fit the holes in the template, carrying a spiral spring and the punch inside, properly centred. By dipping this tool in white paint both the centre punch mark and the white circle are applied to the plate in one operation. Sometimes simply the centre of each rivet hole is indicated on the template and a small centre punch is driven right through the soft wood of the template against the plate over which it is clamped. The diameters of the holes to be punched are indicated by figures painted on the plate, and also such holes as are to be countersunk are suitably marked. The symbol "CKOS" denotes " countersink on the other side." Edges to be sheared are marked on the plate by chalk or soapstone lines and are also reinforced by centre punch marks at intervals. The symbol " *&- ," is often employed to indicate lines to be sheared. In addition to the above, information is also centre punched or painted on the plate regarding any other operations to be performed such as cutting or punching of large holes, or notches, planing, chamfering, joggling, etc., and the strake, side of the ship, and serial number of the plate. If the rivet holes are to be punched small for subsequent reaming care must be taken that the correct sizes of the punches to be used are indicated. After the plate has been laid off it is sent to the plate and PRELIMINARY STEPS IN SHIP CONSTRUCTION 187 angle shed where the necessary shearing, punching, planing, etc., is done as described in the preceding chapter. When this has been done the faying surfaces, or portions of the plate that will rest against the frames, adjacent plates or other members are carefully cleaned and given a coat of red lead. In order to remove mill scale, rust, etc., plates and shapes should be pickled, this being done, of course, before the faying surfaces are red leaded. Pick- ling consists in placing the plate or shape in a mixture of acid and water (usually about 1 part of hydrochloric acid to 19 parts of water) which eats off the rust and mill scale. The plate or shape is then removed, well washed and brushed, then placed in an alkaline solution, then removed, finally washed with water, and dried. The rolled plates are given their proper curvature in the bending rolls as described in Chapter V. The shearing, punching, planing, countersinking, etc., is ordinarily done before the plate is rolled, but the template must be properly made, to allow for the change in distance between rivet holes, caused by the bending of the plate. Plates are also sometimes given a " twist" when necessary, by being inserted diagonally in the bending rolls. Furnaced plates present the greatest difficulties. A bed or frame work must be built up of heavy angles and plates to the proper shape so that the plate after being heated can be hammered, in this bed, to the correct shape. The rivet holes are laid off and punched or drilled after the f urnacing is completed. The edges are finished by chipping. Flanged plates may or may not have the punching and countersinking done before they are flanged. They are usually sheared and planed, however, before flanged. Plating of Decks, Bulkheads, Inner Bottom, Etc. The plates for decks and bulkheads are practically flat, as are the most of those for the inner bottom. The raw material is marked off from templates in much the same manner as the flat plates of the shell. The fabrication work consists of shearing, planing, punching, countersinking, joggling, cutting, or punching of manholes, notches or 188 PRACTICAL SHIP PRODUCTION irregular-shaped edges, and, in the case of margin plates for the inner bottom, of flanging. The templates are usually made by laying down the part in question to full size on the mold loft floor, andjnaking the templates from these lines. The manner in which these parts are fabricated varies, of course, in different yards, and with the structural design of the ship. Bulkheads are usually built up complete so that they may be erected, at the same time as the frames, with their bounding bars and stiffeners. Deck plating is often fabricated from templates " lifted" or made from the ship, while she is being built, after the deck beams are in place. Complete detail plans of each bulkhead, of each deck, and of the inner bottom are used in conjunction with the mold loft lines in making the templates. Frames and Reverse Frames. The exact shape and size of the heel of each frame is shown in the scrieve board, which is really a full-sized body plan of the ship. A mold is made of the transverse flange of each frame, similar to that shown in Fig. 77. In addition a flexible batten is laid on the scrieve board and on it are marked off the land- ing edges of the shell plating, edges of deck plating, stringers, etc. At the same time a bevel board is made, this being a small strip of template wood on which are marked pencil lines running across it at various angles, each being properly marked. The angles that these lines make with the side of the bevel board are the angles to which the frame should be beveled at the corresponding points of its length. The mold, batten, and bevel board furnish the necessary data from which the frame can be fabricated. The actual methods of fabrication vary considerably depending upon whether the frame is a simple angle bar or a channel, Z-bar, or bulb angle, whether it is to be fitted in connection with a reverse frame or not, whether it has excessive curvature or not, and upon the general structural design. It is difficult to punch rivet holes in a frame after it has been bent, but on the other hand if the holes are punched first PRELIMINARY STEPS IN SHIP CONSTRUCTION 189 those in the transverse flange are liable to be partially closed during the bending and those in the shell flange stretched. However, the difficulty of punching holes in the transverse flange is not so great as in the case of the shell flange, and therefore, as a general rule, the holes in the transverse flange are left to be punched after the PLAN Pins Moon Bar Bending : Slab SECTION ON B-B FIQ, 78. Portion of bending'^slab, showing frame bending/ frame has been bent, while those in the shell flange are punched beforehand, a suitable allowance being made in laying them out (based upon experience) for the stretching of this flange during bending. Where the curvature is excessive no holes are punched before bending, those in the 190 PRACTICAL SHIP PRODUCTION shell flange being punched later in a horizontal punch, or drilled. The method of bending frames, reverse frames, bulkhead boundary bars and other curved shapes is shown in Fig. 78. The shape of the heel of the bar is chalked on the bending slab and another line is laid off parallel to this and inside of it a distance equal to the width of the transverse flange. A soft iron bar, called a set iron is then bent to this shape and clamped in place by means of pins, wedges and dogs that fit into the holes of the slabs, as shown in the figure. The frame bar having been heated red hot /Beveling 1 Lever /Bending Slab Bevel Tester Bevel Board FIG. 79. Frame beveling. in the reverberatory furnace is dragged out onto the slabs and one end is placed against the corresponding end of the set iron with the toe of the transverse flange against it, as shown in the lower right-hand sketch of Fig. 78. This end is then secured by dogs in the same manner as the set iron and the frame bar is bent around by means of moon bars, or other suitable tools, so that the toe of the transverse flange finally fits against the set iron at all points. As fast as each few inches of the bar have been properly bent they are promptly dogged down against the slabs. (These dogs are not shown in Fig. 78 but one is shown in Fig. 79.) PRELIMINARY STEPS IN SHIP CONSTRUCTION 191 After the frame has been completely bent to shape, the proper bevels are given to it at all points of its length by means of the bevel board from which the successive bevels are lifted by means of a bevel tester or adjustable square, as shown in Fig. 79. The opening of the flange is accom- plished by means of beveling bars, or levers of which one is shown in the sketch. Floors. Templates for the floor plates are made from the scrieve board. In the case of ships fitted with double bottoms (which is generally the case for all but very small ships) the floors together with their upper and lower angles, connecting clips, etc., are made up complete so that they may be erected and bolted to the vertical keel as soon as the latter is in place. Horizontal reference marks are made on the templates of floor, vertical keel angle, margin plate angle, and angles for longitudinals so that the rivet holes will come correct. These same templates are used for trans- ferring the corresponding rivet holes to the templates for the members to which these angles are to be secured. Simi- lar vertical guide lines are marked on the templates of floor and frame and reverse frame angles. The fabrication of the floor plates consists in shearing, punching and cutting of lightening holes, drain holes, air- holes, limber holes, etc. Keel Plates, Longitudinals, Etc. The plates for the keel and centre vertical keel are laid off from templates made from the mold loft lines, and plans showing the details of riveting, butts, etc. These templates must be made in conjunction with those for the floor connecting angles and frames and the templates for top and bottom angles for the vertical keel must be made to agree with those for the vertical keel. The plates for the vertical keel are prac- tically all flat and rectangular, so that the fabrication consists in shearing, punching and cutting of lightening or other holes. The flat keel plates are slightly dished as a rule, this being done after they have been punched. Those at the ends, which connect with the stem and stern frame, are considerably dished and usually have to be 192 PRACTICAL SHIP PRODUCTION furnaced. In this case the holes may be drilled after the plates have been shaped. As the keel is the first part of any ship to be erected it must always be made from mold loft templates since at that stage there are no other parts in place from which to "lift" it. Longitudinals, where continuous, as in warships, are fabricated in much the same way as centre vertical keel plates from mold loft templates. In merchant ships, where they are ordinarily intercostal the longitudinals are made up of a great many short rectangular plates. Some- times these are flanged at each end for connection to the floor, in order to avoid the use of clips. Longitudinal members outside of the inner bottom, such as bilge and hold stringers can best be fabricated from templates lifted after the frames are in place, though these are sometimes made in advance. The fabrication work consists of shearing, punching, and cutting of holes. Deck beams are fabricated in advance, at the same time as the frames. For this purpose a beam mold is made, this being usually of wood about 1" thick, with one edge trimmed to the proper camber, and of length sufficient for the longest beams. The beams are bent cold as a rule in the beam bending machine which supports a portion of the beam at two points on one edge while the other edge is subjected to pressure midway between these two points of support. Templates made for the brackets which connect the beam ends to the frame bars must be made in conjunction with the templates for the frames. Bulkhead stiff eners are ordinarily laid off along with the bulkhead plating and bounding bars, so that all bulkheads may be assembled and riveted up as units which can be erected complete. Brackets. In full-lined, parallel sided ships a large num- ber of the brackets are identical and can be laid off from the same template. Sometimes brackets are not fabricated in advance but are lifted from the ship. Bounding -bars are handled in much the same way as PRELIMINARY STEPS IN SHIP CONSTRUCTION 193 frames, being laid off and bent and beveled on the bending slabs in a similar manner. The exact methods of fabricating the various parts of the hull vary so much in accordance with yard practice and the structural design of the particular ship under con- struction, that little is to be gained by a detailed description of the work in any one case. It is well to note, however, certain general points that apply to all ship construction. The templates for any two or more members that are to be fastened together must be made in conjunction with each other so that rivet holes in the different parts will be fair when they are erected in their proper positions in the ship. If templates are to be made in advance in the mold loft the chances for error will be reduced by having plans pre- pared accurately and in great detail to show all measure- ments, locations and sizes of rivet holes, butt straps, liners, etc. If these plans are made with sufficient care and in enough detail practically every part of the ship can be completely fabricated before a bit is erected. (This accounts for the rapidity with which it is possible to build ships after the keels have been laid.) Whether all the members are to be templated in advance of the commencement of building on the ways or not, the flat and vertical keel plates, inner bottom framing, margin plate and usually some of the bottom shell plating must be got out in advance. These parts must be carefully prepared so as to fit fairly, each with its neighbor, when erected. Where rivet holes are to be punched only and not reamed it is usually necessary to punch some from one side and some from the other of certain plates. Hence in marking them off care must be taken to mark all rivet holes on the correct side or the faying side of these plates so that they may be punched from that side. Plates and shapes should be pickled to remove all rust and mill scale. After fabrication they should be red leaded 13 194 PRACTICAL SHIP PRODUCTION well over all faying surfaces, and identification marks carefully painted on them. For the best class of work rivet holes should be punched small and reamed after the work is in place. This not only makes possible more efficient riveting and increases the strength by cutting away the material around the hole that is weakened by punching but it gives more leeway for reaming unfair holes and thus minimizes the amount of drifting that must be resorted to. All fabrication work should be carefully done, and tem- plates followed exactly. Otherwise the parts will not fit properly in place when erected and filling in pieces, extra liners, and excessive reaming, will be necessary and imperfect calking, and consequent loss in strength and water-tightness will be caused. CHAPTER VII THE BUILDING OF SHIPS 1. ERECTION The first step in the actual building of a ship is the laying of the keel, and this being one of the principal events in the process of ship production, is often the occasion of an accompanying ceremony. The time required to build a ship is frequently measured from the date that the keel is laid to the date when the hull is launched. This how- ever does not give a true idea of the time required to pro- duce the ship, unless the length of time spent in fabrication work previous to the laying of the keel, and the length of time necessary to complete the vessel after she is launched are also known. The amount of preliminary work actually necessary for the laying of the keel is slight, since all that is done in the actual operation is to set in position two or three of the flat keel plates or a few sections of the bar keel (if that is the type keel used). After this has been done however the work of erection cannot proceed rapidly unless a large amount of fabricated material is on hand, and therefore it is ordinarily the practice to delay the laying of the keel until the getting out of the fabricated material has been under way for several weeks, or perhaps months. The keel blocks have been described in Chapter V. In order to prepare them for the keel-laying the upper surface of the highest of each group of blocks must be carefully trimmed off so that all are in a straight line having the proper slope (which, as previously stated, commonly ranges between % 6 " and iJKe" per foot) and have their surfaces square to the central longitudinal plane of the ship. The appearance of a set such blocks, ready for 195 196 PRACTICAL SHIP PRODUCTION the laying of the keel is shown in the foreground of the picture, Fig. 69. A straight line is drawn across the top of each upper block to indicate the exact centre line of the ship. After the first few keel plates have been carefully lowered into position on top of the blocks (by means of derricks or cranes), so that their centre line coincides exactly with the line drawn on the blocks, and they have been correctly located in a fore and aft direction, the connecting butt straps are bolted in place and the other plates of the flat keel are lowered into place one at a time, carefully set, FIG. 80. Flat and centre vertical keel plates in place on blocks. and similarly secured to their neighbors by their butt straps. On top of the flat keel plates are then placed the plates of the vertical keel, with its two lower connecting angles, which are bolted in place. In Fig. 80 is shown a picture of some of the flat and vertical keel plates with their connect- ing angles in place on the keel blocks. It will be noted that only a few bolts are necessary to hold them in place, these being inserted through rivet holes. The rivet holes for the connecting angles by means of which the floor plates will be attached to the centre vertical keel, and also those THE BUILDING OF SHIPS 197 for the top angles of the vertical keel are plainly seen in the picture. The flat plate keel butts in this case are lapped instead of butted. In order to bring the rivet holes in connecting members into alignment a drift pin is driven into some convenient rivet hole so that its wedge-like action will cause the two members to slide along the faying surface, as shown in Fig. 81, until the rivet holes come fair. If all of the holes are not correctly punched in bringing one hole fair one or more FIG. 81. Drifting. other holes may be made unfair. If the unfairness is too great the replacement of one of the members may be nec- essary with consequent waste of material and loss of time and labor. It is usually customary in the case of merchant ships, which have comparatively flat bottoms, to erect the bottom plating soon after the flat and vertical keel plates are in place. In order to support these bottom strakes during this process heavy wooden athwartship timbers are used placed at intervals along the ship's length normal to the keel line, as shown in Figs. 82 and 83. The bottom plating out to and including the first curved bilge strake is usually so handled as shown in the pictures. On top of the bottom shell plating is next placed the double bottom framing, which consists of frames, reverse 198 PRACTICAL SHIP PRODUCTION frames, and floor plates with their connecting clips. In the case of the ship shown in Fig. 82 bracket floors are used, one of which is shown being lowered into place by the crane. FIG. 82. Erecting double bottom framing. This picture gives a view looking aft along the centre line of the ship over the top of the centre vertical keel, which, not yet having been completely secured, presents a FIG. 83. Portion of double bottom framing completely erected. "wobbly" appearance. A portion of the port top vertical keel angle is shown in place. A view showing the erection somewhat further advanced is given in the picture in Fig. 83. Here a complete portion THE BUILDING OF SHIPS 199 200 PRACTICAL SHIP PRODUCTION of the double bottom framing is erected and the clips for the margin plate and the supports for the tank top plating can be seen. In the lower right-hand portion of the picture will be seen some of the connecting clips by means of which floors are to be attached to the centre vertical keel. The angle at which the top line of the keel blocks is set with the horizontal is also clearly visible. The next step is the erection and bolting up of tank top plating, margin plates and the brackets for the attachment of frames. Figure 84 is a picture showing the bottom por- tion of a ship under construction, of which all the inner bot- tom framing has been completed, and a portion of the tank top plating, margin brackets, shaft alley framing and plat- ing, and after portion of engine room have been erected. Several frames on the starboard side, one on the port side, one deck beam and two plates of a bulkhead just a little aft of these have also been erected. When the construction has advanced this far a certain amount of the riveting in the double bottom should also have been accom- plished, since it is much easier for the riveters to do their work in these spaces before the tank top plating is in place. As the hull is gradually built up shores are placed under the bottom to support the increasing weight of the material in place. Some of these will be noted in Fig. 84, and also the lower portions of the scaffolding on each side of the ship, which will soon have to be built up higher for use of the workmen in erecting the frames, beams, bulkheads, etc. The erection of the side frames is next proceeded with, together with deck beams, bulkheads, stanchions, girders, stringers, engine and boiler foundations, shaft alleys, etc. Fig. 85 shows a ship under construction with a number of side frames and lower deck beams, stanchions, etc., in place. The coaming for the after cargo hatch in the lower deck can be seen, and also the shaft tunnel, shoring under bottom, derricks and scaffolding used in erecting and bolting up the various members, deck beam brackets, etc. In order to hold the side frames in their correct positions, THE BUILDING OF SHIPS 201 202 PRACTICAL SHIP PRODUCTION after they have been carefully set at the proper rake with the vertical (to allow for the slope of the keel blocks) by means of a plumb-bob and ''declivity board," and square to the keel line, longitudinal wooden pieces called ribbands are temporarily installed along the shell flanges. These are heavy timbers, which are fitted along the frames in Lightening Hole Margin Plate Bracket FIG. 86. Cross section of building slip. way of outer strakes, being clamped to each frame by means of a bolt and small plate washer. As they have only a slight "give" they serve to fair the frames and as they run along the spaces to be subsequently occupied by outer strakes they do not interfere with the bolting up of the plates of the inner strakes. After the inner strakes, and deck stringer plates, hold stringers, etc., have been bolted THE BUILDING OF SHIPS 203 up, the ribbands are removed and the outer strakes put in place and bolted up. At the ends of the ship, where the curvature is sharp, special timbers have to be used, carefully cut to shape from the mold-loft lines, to per- form the same functions in these places that the ribbands perform in the middle body. These timbers are called harpins. The building slips shown in Figs. 84 and 85 are heavy plat- forms built over the tops of the piling (see also Fig. 69). More often it is the practice to lay the keel blocks on cross logs at the ground level (see Fig. 86). FIG. 87. Wooden ship under construction. After the side frames have been erected the side shell plating is put in place and bolted up, and the erection of deck beams, deck stringer plates, deck plating, coamings, bulkheads, stanchions, and in fact all of the various interior members is proceeded with, certain riveting and calking of the portions of the hull that are now completely erected being taken up concurrently. The remainder of the erection work is of a miscellaneous character and goes on while the riveting and calking of the lower portion is being done right up to and even after 204 PRACTICAL SHIP PRODUCTION the launching. As the hull rises the scaffolding on each side is extended up (see Figs. 85 and 86) and stage planks are placed on it for use of the bolters up, riveters and calkers. The order in which the parts are erected in a wooden ship is practically the same as for a steel ship. Figure 87 shows such a ship under construction. (Note the double frames.) 2. BOLTING UP, DRILLING AND REAMING As soon as any part of a ship has been placed in its proper position it is bolted up, or secured temporarily, by bolts placed at intervals through the rivet holes, to the ad- jacent parts to which it is finally to be riveted. At this stage of the construction unsatisfactory workmanship in the fab- rication, if such exists, will be made evident. There are two conditions that must be strictly fulfilled, if the con- struction is to be satisfactory, in the case of each and every structural member of the hull: 1. Each must be in the correct position as called for by the plans, and 2. Each must have all of its rivet holes come fair with those of the adjacent members. When all the parts have been properly shaped and the rivet holes have all been correctly laid out and punched both of these conditions can be fully met. In practice, however, unless extreme care is used and all the workmen are highly skilled, this will seldom be the case. In bringing one part into its proper position it will often be found that the rivet holes for connecting it to its neighbor will be drawn out of alignment, or conversely in attempting to bring into alignment the rivet holes of a part already in its correct place, that part may be forced out of its proper position. During the bolting up all such defects should be noted so that they may be remedied before the riveting is started. All parts should be true and fair and free from dents, hol- lows, unevennesses or other imperfections that would THE BUILDING OF SHIPS 205 prevent satisfactory riveting and calking (which will be described below). Members that are not to be riveted until a fairly late stage of the construction, or for which the adjoining parts are to be temporarily omitted for purposes of access, etc., must be especially well bolted up and secured by temporary wooden tie pieces, shores, etc., in order to prevent their shifting out of place. All sharp and jagged edges, burrs, etc., should be removed. In certain places, where oil-, or water-tightness is re- quired, oil stops or stopwaters must be fitted between the adjoining steel members. These consist of canvas, hair felt, lamp wick, etc., treated with various paints, etc., and will be described more in detail later. These must be fitted, however, during the process of bolting up. Reaming. After the members have been properly aligned, fitted and bolted up the rivet holes must be reamed. This is necessary to remove the slight unfairnesses that are almost inevitable on account of the inaccuracies of laying out and punching the rivet holes, and is also often done to enlarge the holes, which are punched small for this purpose, so as to make a neat fit for the rivets and to remove the por- tion of metal just outside of the hole, which is weakened by the action of the punch. In addition, in certain cases, reaming is necessary to remove the taper that the holes have as a result of punching (see middle sketch of Fig. 89) . In Fig. 88 is shown a sketch of a reaming tool or reamer which fits in a machine run by compressed air. The end is tapered so that the reamer can be inserted into rivet holes that are unfair. (See third hole from left in bottom sketch of Fig. 88). In reaming holes it is important that the finished hole should be normal to the plate and also that it is not of too great a diameter. In Fig. 88 are shown various types of rivet holes. The one to the left is perfectly fair and will require little or no reaming. The next is only slightly unfair and can be reamed with only a small increase in diameter. The next can be reamed but the diameter of the resulting hole will 206 PRACTICAL SHIP PRODUCTION be considerably greater than would have been necessary had the parts been properly fitted. The right-hand hole, which is half blind, is so unfair that it should not be reamed since the resulting hole would be altogether too large. Where holes come unfair there is a temptation to avoid increasing the diameter by running the reamer through at an angle. If the angle is very slight, this, though poor workmanship, is sometimes permissible, but if too great will cause a weakening of the joint preventing the rivet Shank' utes REAMER ( Taper about %'per foot) Perfectly Fair Nearly Fair Can be Reamed Too Unfair for Reaming RIVET HOLES FIG. 88. Reaming. from filling the hole completely. Examples of the results of improper fitting and reaming, and of failure to ream at all in the case of " three-ply " riveting are shown in Fig. 89. When the driven rivet is not of the designed diameter, or does not fill the hole completely it loses in efficiency, and the strength of the whole joint is consequently reduced. If many unfair holes occur this will be a serious matter and may endanger the ship. THE BUILDING OF SHIPS 207 It is also important to see that the burrs on the edges of rivet holes or shavings, etc., do not prevent the faying surfaces from being drawn tightly together when riveted. Drilling. It is not practicable to have all rivet and other holes punched in advance, and it is therefore necessary to have certain drilling (and countersinking) done after the material is in place in the ship. Such holes are those in castings, forgings and furnaced parts that cannot be conveniently punched, holes the exact locations of which Holes reamed at an angle Punched holes, in three-ply riveting, not reamed. Unfair hole in centre ply. Hole reamed at an angle. FIG. 89. Effect of unfair rivet holes and improper reaming. are not known in advance (such as those for voice tubes, pip- ing systems, electric conduits, etc.) and certain rivet holes for work that requires extreme accuracy, as in the case of oil- tight work, work on submarines, etc. Drilling may be done by means of electric or pneumatic tools, or by the ordinary hand ratchet drill. The former are much more rapid processes than the latter, but all are very slow compared to the punching and reaming 208 PRACTICAL SHIP PRODUCTION method. On the other hand, absolute accuracy and practically perfect riveting can thus be attained and the material is not weakened thereby, as when punched. The method of using the pneumatic drilling machine is shown in the sketch in Fig. 90. The upper end of the apparatus is pressed down by some sort of a rig similar to that shown in cases where some rigid bearing for the upper end of the machine is not at hand. When a portion of the ship may be used as a bearing the drill is gradually advancd by screwing up the top spindle by means of the upper handle shown in the sketch. When a wooden stick Pressure Tie Rod Handle _J2 Combined Handle and Compressed Air Pipe and Valve Nut' FIG. 90. Method of using pneumatic drilling machine. is used, as shown, this is accomplished without the use of this handle by simply keeping pressure on the end of the stick. The two handles on each side of the machine are grasped by the operator in guiding and running it, one of them serving also as a means for starting and stop- ping the machine. This machine can also be used for reaming and countersinking by replacing the drill by a reamer or countersink. With the ordinary hand ratchet drill a portable arm or support, called an "old man" is used. The speed with which drilling can be accomplished de- pends upon the diameter of the holes, the thickness and nature of the material to be drilled, the accessibility, THE BUILDING OF SHIPS 209 condition of tools, air pressure, etc. Similarly with ream- ing and countersinking, though the latter of course should require much less time, per hole, than drilling. It is not at all difficult, under good conditions, for a workman to ream and countersink 800 or 900 holes in a day. Drillers are also required to drill and tap holes for bolts and screws (see Section 3, below). Great care should be exercised and efficient supervision maintained to see that holes are drilled and reamed properly, otherwise defective riveting is bound to result. It is important that all holes should be perfectly cylindrical, normal to the faying surfaces, of the proper diameter, and that burrs, borings, pieces of metal, or other foreign materials do not get between the faying surfaces. 3. RIVETING As has already been noted riveting is of the greatest importance in shipbuilding. All the structural members of a steel ship (except in the case of welded ships which are described below) are tied together by riveting so as to act as a complete unit. If the rivets are not absolutely tight, of the designed size and strength, and located as provided for in the design, the strength of the ship is bound to be impaired. While a factor of safety is, of course, used in designing such a ship, nevertheless a certain amount of careless workmanship may have serious results. It will be readily seen that some of the rivets in Fig. 89 can come nowhere near performing the functions for which they were designed. For example, the upper right-hand rivet, being reduced in sectional area at the faying surface, has its shearing strength reduced, while in the case of bearing pressure it can develop practically no strength. It is, of course, evident that in many cases defective riveting is not directly the fault of the riveting gang, but rather of the layers-out, or the punch operators, or the drillers or reamers. Nevertheless a certain responsi- bility must rest with the riveters, for rivets should never be driven in holes that have not first been properly prepared. 14 210 PRACTICAL SHIP PRODUCTION The operation of driving a rivet is shown in the sketch in Fig. 91. Having removed the bolt, if any, from the rivet hole the holder-on inserts the hot rivet in the hole and drives it well home so that the head rests tightly against the inner plate, around the inner end of the hole, with the holding-on hammer, a large, heavy headed hammer, which he then presses hard against the rivet head. The riveter, on the other side of the plates then proceeds to. stave in or drive Holding-on Hammer \ ot Rivet Riveting Hammer FIG. 91. Driving a rivet. the rivet, either by means of a hand or a pneumatic riveting hammer, so as completely to fill the hole. In order to be sure that the rivet has sufficient volume for this purpose it is selected a trifle long, and after it has been well clinched, the excess metal is cut off with a chipping tool by the riv- eter and the point smoothed up and finished after it has cooled slightly. In order to permit of this cooling it is THE BUILDING OF SHIPS 211 usual to drive one more rivet and then go back to finish off the rivet driven just previously. Various methods of holding-on are in use. Sometimes instead of a hand holding-on hammer a pneumatic one may be used, this consisting of a cylinder and piston secured at the end of a stiff brace or rod. In cramped and other in- accessible places a curved or offset holding-on tool is used, commonly known as a "dolly bar" (see Fig. 91). Countersunk head, angle too small . Hammered point, too low. Button point, not symmetrical, plate scored. Excessive burr on plates not removed . Plates not drawn together. Drillings between plates. Hole too large, not completely filled by rivet. FIG. 92. Improperly driven rivets. When properly driven the head and point of a rivet should be symmetrical about the axis of the rivet, the plates around them should not be marred or scored and the two plates should be drawn tightly together. The shrinkage of the rivet in cooling, especially if a long one, has a tend- ency to accomplish this result. The same applies, of course, to two shapes, or a plate and a shape, riveted together. In order to test the quality of riveting the heads and points should be inspected visually, and tapped with a hammer it being possible to tell by the sound and "feel" whether the rivet is tight or loose. With a thin 212 PRACTICAL SHIP PRODUCTION flat knife or " feeler " it is possible to determine whether or not the faying surfaces have been properly drawn together. In Fig. 92 are shown a few examples of rivets that have not been properly driven. These together with those shown in Fig. 89 represent a few of the kinds of unsatis- factory workmanship in riveted joints that may be met with in practice all of which should be avoided, since they re- duce the structural strength and water-tightness of the ship. It will be noted that defects in riveted work may be due to carelessness or lack of skill of any or all of the follow- ing workmen : loftsmen, layers-out, workers in the fabricat- ing shops, bolters-up, drillers, reamers or riveting gangs. Effective Not Effective UNSAFE LOADING SAFE LOADING FIG. 93. Safe and unsafe loading of ropes. Nevertheless the final blame attaches to any riveter who drives a rivet in a hole that has not been properly prepared to take it, or who does not do his own work properly. Defective riveting is not only a source of actual danger to a ship, but is the direct cause of added cost in her upkeep, since if the riveting is not properly done leaks, straining of the hull, and excessive corrosion will be continually occur- ring as the ship is subjected to the various strains incident to her service. Therefore too much emphasis cannot be laid on the importance of requiring good riveting. The action of rivets in maintaining strength and water- tightness may be illustrated by comparison with the case of a suspended weight. Suppose that a piece of rope is THE BUILDING OF SHIPS 213 just strong enough to support a weight of one ton. If this weight be suspended by the rope, as shown in the left sketch of Fig. 93, the strength of the rope will be effective, and a condition of safe loading will exist. Three pieces of this same rope will support a weight of three tons, provided that the strength of each piece is effect- ive. In the right sketch of Fig. 93 one piece of rope is longer than the other two, and consequently its strength is not effective. The other two pieces can support only two tons, the condition of loading is unsafe, and the two outer ropes will break if the three-ton weight is given no support other than that of the ropes. SAFE FIG. 94. Safe and unsafe loading of riveted joints. In the case of riveted joints a similar principle applies. In the upper sketch of Fig. 94 is shown a safely loaded riveted joint in which is a perfectly driven rivet, large enough to withstand a pull of ten tons. In the lower sketch is shown a joint with three of the same sized rivets, but one of them is defective so that it furnishes no assistance to the other two. The efficiency of this joint is only two-thirds of what it should be, and the joint would fail under a 30- ton pull. When ships are designed a factor of safety is of course assumed, but this factor of safety is itself based on an assumption, since there is no way of determining accurately 214 PRACTICAL SHIP PRODUCTION the stresses to which a ship may be subjected when at sea in a gale or hurricane. Consequently a sufficient number of defective rivets might cause a ship to be lost at sea. Such cases have actually occurred. The speed of production of steel ships is necessarily dependent upon the speed with which the riveting is ac- complished. Practically all the structural joints of such ships, as usually built, are riveted, and a moderate sized ship will contain over a million rivets. If one gang of riv- eters drives 400 rivets per day, on an average, it will thus be seen that, to accomplish the riveting of such a ship in three months, over 27 gangs of riveters, working every day of the week would be required. A yard building ten such ships at a time, at this rate, would require nearly 300 gangs of riveters an unusually large number. The speed with which rivets can be driven depends upon the size of the rivets, the quality of the reaming and coun- tersinking, the manner in which the bol'ting-up has been done, whether the holes are "scattered" or not, the accessi- bility of the work, the air pressure, the condition of the tools, the prevailing weather conditions, etc. Under fair average conditions it may be said that it might easily be possible for a skilled riveting gang to average 50 rivets per hour or 400 in an eight-hour day. As a matter of fact single riveting gangs have actually driven several thousand rivets in a day, per gang, but this must be considered as unusual. A close supervision over all riveting should be main- tained during the construction of the ship. All rivets should be carefully tested and those found defective marked. Some may be made good by rehammering, but others will have to be cut out and new rivets driven in their places. The methods of cutting out rivets are illustrated in Fig. 95. Button or hammered points are cut away by the chippers and the rivets then knocked out by means of a backing-out punch and hammer. In the case of a counter- sunk point a hole of nearly the size of the rivet is drilled so that the remaining ring of metal may be easily torn by THE BUILDING OF SHIPS 215 the backing out punch, as shown. Sometimes a chipping tool is used, and sometimes the oxy-acetylene blow pipe or cutter, for cutting out such rivets, but both methods must be used with great care, or otherwise the metal around the rivet holes is liable to be damaged. The diameter of a rivet hole should be about He" greater than the diameter of the cold rivet. This allows for the insertion of the hot rivet which is slightly enlarged by the heating. The rivets most used in merchant ship 'building are %" , %" ', %", and I". In naval work the smaller sizes (M"> %"> an d /4") are sometimes used, especially for vessels of light scantlings, like destroyers. Rivets as large as \%" or 1J4" are required only for very large king-out Punch FIG. 95. Cutting out rivets. ships or in special cases. The diameters of rivets to be used should be selected to suit the thicknesses of the plates or shapes that they are to connect. The practice varies slightly in merchant and naval work but the following is a rough guide for either class : 10 Ib. plate 15 Ib. plate 20 Ib. plate 25 Ib. plate 30 Ib. plate 40 Ib. plate in.. rivets in. rivets in. rivets in. rivets in. rivets in. rivets Where the two thicknesses to be connected vary slightly the size of rivet should correspond to the greater thickness if strength is more important, and to the lesser thickness if 216 PRACTICAL SHIP PRODUCTION water tightness is more important. If the two thicknesses vary greatly the diameter of the rivet should correspond to the average of the two. The increase in diameter of a punched hole due to subsequent reaming should be about y&". Hand riveting when done by skilled riveters is superior to machine riveting but is more expensive. There are two riveters in a hand gang, each with a hammer, striking alternate blows on the point of the rivet. One works right handed and the other left handed. Long through rivets such as those through stem, stern post and bar keel are usually driven by hand. Such rivets are heated only at their points, the main portion of the shank being a driving fit in the hole, since it is practically impossible to drive them tight otherwise, and also since the contraction on cooling of a long rivet might cause it to break. The point must be slightly tapered before it is inserted in the hole on account of its enlargement due to heating. The head may be heated by a torch and well staved up while hot. Some shipyards that build very large vessels employ portable hydraulic riveting machines. These, on account of the high steady pressure that can thus be applied to the rivets, produce a very high quality of work, and insure the com- plete filling of the holes by the rivets, a thing that is very difficult to accomplish by hand in the. case of large rivets. Tap rivets are used in places where it is not practicable to drive ordinary or through rivets. A tap rivet is really nothing but a threaded bolt having a head shaped like a rivet head. In Fig. 96 are shown two forms of tap rivets. One has a square head which is cut off after it has been well screwed up. The other has a "wring-off" head which is twisted off, by the Stillson wrench with which it is screwed up, as soon as it has drawn the plating up tight and cannot turn further. Tap rivets generally have to be used to a certain extent for connecting the shell plating to stem, stern frame, and shaft brackets, and in other similar cases where a thin part THE BUILDING OF SHIPS 217 is connected to a relatively thick one, that does not permit of through riveting. They should not be used in thin plat- ing since the threaded portion is not enough in such cases to give good holding power. The depth of the threaded portion of the hole should be at least equal to the diameter. In places where vibration will occur (as in the case of the propeller boss) a depth of 1% diameters should be required. The holes must of course be drilled, and both the drilling and tapping must be done very carefully in order that the head may fit the countersunk hole exactly and concen- Square head, to be chipped of Round "wring- off' head / FIG. 96. Tap rivets. trically in order to draw the two parts tightly together. Sometimes after a tap rivet has been screwed up and trimmed off the head is heated by a torch and driven up by a riveting hammer so as to fill the hole tightly. Tack rivets are rivets located in the middle portions of doubling plates so as to keep the faying surfaces together at all points. For oil-tight work an especially high class of riveting is necessary. The rivets are more closely spaced (3 to 3K diameters between centres, as compared to water-tight spacing which is usually from 3>i to 5 diameters), and should be either drilled or punched small and reamed absolutely fair. In connecting high tensile steel plates or shapes high tensile rivets should be used. The holes should be drilled. 218 PRACTICAL SHIP PRODUCTION Before rivets are driven the following points should be looked out for : 1. The holes should be properly located, fair, of the proper size, and reamed if necessary. 2. The plates or shapes to be riveted should be smooth, fair, free from bumps, knuckles, burrs, etc., and securely drawn together with a sufficient number of bolts, well set up. (About every fourth hole for oil -tight work.) 3. There should be no chips, shavings or other foreign matter between the faying surfaces, and these surfaces should be properly coated usually with red lead, if for a water-tight or non water- tight joint, or with a mixture of pine tar and shellac or other suitable coating, if for an oil -tight joint. 4. If for oil-tight work, three-ply work, or work where strength is very important, the holes should be drilled or punched small and reamed fair and normal to the faying surface. 5. All butts and edges should fit tightly together. 6. The joints should be metal-to-metal and filling-in pieces should not be used. (In certain cases, where oil- stops or stop- waters are required, these should be in place.) During the riveting the following should be looked out for: 1. The rivets to be used should be long enough to allow for the metal required for forming the points. 2. The rivets should be of the proper diameters com- pletely to fill the holes. 3. Care must be used to see that the rivets are not sub- jected to too great a heat and thus " burned. " 4. The rivets must be sufficiently heated (until just before they give off sparks) before being passed to the holder-on. 5. The heads should be well jammed up against the sur- face by the holder-on before the riveter strikes the points. 6. The hole must be completely filled by driving the hot rivet well home. 7. The excess metal from the point should be cut off while it is a dull red. - - - - - '-- - - - THE BUILDING OF SHIPS 219 8. The point should be properly formed and concentric with the shank of the rivet. 9. In removing bolts care should be taken that the faying surfaces do not spring apart. 10. The plates or shapes around the rivet holes must not be dented or cut during the riveting or chipping off of the excess metal from the points. 11. If a rivet is not driven tightly this should not be concealed by a partial calking of the head or point. All riveting should be carefully and conscientiously done. In general the effort should be to secure riveted joints that are in strict accordance with the plans, or that will develop the strength and water- tightness that they are intended to develop. All the rivets should be of the proper size, shape, location and tightness, holding the faying surfaces closely together like the rivets shown in Figs. 21 and 96, and not like those in Figs. 89 and 92. 4. CHIPPING, CALKING, ETC. Chipping consists in cutting or trimming various structural parts by means of a chipping tool or chisel. Like riveting it may be done by hand, or by means of a pneumatic chipping hammer, the action of which is similar to that of the pneumatic riveting hammer. Chipping is often necessary to remove burrs or other unevennesses or to smooth up work in order to obtain a satisfactory fit. Certain large holes are also often cut out by the chippers, especially where neat work is required, and the oxy- acetylene blow-pipe (which is much quicker, but which leaves a rough edge) cannot be used. Chippers are also employed in cutting out defective rivets or other 'structural parts that have to be removed, although much work of this nature is now done by the oxy-acetylene cutters. Calking is the process of making joints tight to prevent the leakage of water, oil, air, etc., and, in the case of steel parts, consists in forcing the edges or butts of adjoining members tightly together. It is usually done by the same 220 PRACTICAL SHIP PRODUCTION workmen who do chipping and most frequently is done with pneumatic tools in a manner similar to chipping. Work- men of this trade are often called chippers and calkers. The process of calking is illustrated in Fig. 97. It consists essentially of two operations: first the metal is split, or grooved, by means of a splitting tool or splitter, and then the portion of the metal between the split and the faying surface or butt is forced tightly against the other Splitting Edge Calking Calking a Lap Joint (Edge Calking) Calking a Butt Joint (Butt Calking) FIG. 97. Calking. part, as shown in the sketches, by means of the calking tool, or finishing tool. There are two kinds of calking: edge calk- ing, and butt calking, the nature of each of which will be evident from Fig. 97. In edge calking a slight shoulder is formed, as shown, where the edge of the outer plate overlaps the inner. Countersunk points of rivets should usually be calked, the process being similar to butt calking, but done with a special small ended tool. Calking is, of course, not done until after the riveting has been completed the order of the various processes THE BUILDING OF SHIPS 221 being: (1) bolting up, (2) drilling or reaming (and, if necessary, countersinking), (3) riveting, (4) calking. The edges and butts to be calked should be planed. The row of rivets nearest to the calking edge or butt serves to hold the plates (or parts being riveted) together so that the calking will be effective, the elasticity of the steel resulting in keeping the outer plate pressed tightly against the inner at the calking edge after the calking has been completed. For this reason it will be noted that the line of the rivets, must not be too far from the calking edge, or the calking may open on account of the spring of the plate. On the other hand the rivets must not be too close to the edge of the plate or the strength of the joint will be impaired. Furthermore a certain allowance must be made for cor- rosion and for repeated calking, as certain seams may have to be re-calked from time to time in the course of repairs and upkeep. Each re-calking reduces the distance between the edge of the plate and the outer row of rivets, which distance may finally become so small as to require renewal of the plate (or shape). For these reasons the distance from the edge of the plate to the line of centres of the nearest row of rivets is usually made equal to 1J or 1% times the diameter of the rivets. This gives an amount of plate, between rivet and edge, of at least the diameter of the rivet. Any line of calking must be continuous that is it must either join another line of calking or form a closed loop. If the calking stops, or is defective at any point, a leak will occur at that point, and the good of the remain- der of the calking will be offset by this one point of weakness. The calking of a bulkhead, or other plated surface, forming the boundary of a compartment that is to be filled with water in order to test the calking, should be done on the side away from this compartment in order that such leaks as occur may be located during the testing, and repaired. Edges and butts that are to be calked should have a tight metal-to-metal fit even before being calked. In some cases, especially around stapling and collars this is 222 PRACTICAL SHIP PRODUCTION very difficult to attain, and in order to secure a proper calking edge the use of metal filling-in pieces or wedges (sometimes called l ' dutchmeri") may be permitted. This is, however, a bad practice and should be avoided by in- sisting upon careful workmanship of the anglesmiths and shipfitters. Butt calking is more difficult to perform than edge calking since in the latter the inner plate serves as a guide for the calking tool, whereas in the latter there is no guide. In some places calkers have to work "left-handed. " Light plating (less than about JK 6 mcn thick) cannot be calked since there is not sufficient stiffness to the material to hold the calked edges together. Here stopwaters must be used. Stopwaters (or oil-stops) must also be used where an un- calked member passes through a water-, or oil-tight surface, to prevent leakage past the surface through the parts of the uncalked member. Stopwaters are pieces of canvas, bur- lap, felt, etc., soaked in linseed oil and red lead, or coated with some tarry substance or with a mixture of red and white lead. These are placed between the faying surfaces which are drawn tightly against them by the rivets. Oil- stops are made of lamp wick, canvas, felt, etc., soaked in a mixture of shellac and white or red lead, or of pine tar and shellac, or other suitable substance. Oil-stops are used to prevent the leakage of oil and must therefore be treated with some substance that wilt not be dissolved by oil. Both oil-stops and stopwaters should be used only where abso- lutely necessary and they should be freshly coated when the bolting up and riveting is done. Sometimes leaky joints are made tight by welding, which is described in Section 6, below. In some cases where joints cannot be made tight by calk- ing it is the practice to make use of the red lead putty gun. When this has to be done it is always a sign of poor work- manship and its use should be avoided as much as possible. This contrivance is shown in Fig. 98, and consists of a simple hollow cylinder threaded on the inside, which is THE BUILDING OF SHIPS 223 filled with red lead putty and connected to the part to be gunned as shown in the sketch. As the plug is screwed down the putty is forced into the joint under great pressure and fills all the crevices. When this operation is completed the gun is unscrewed and the hole temporarily made for its attachment is closed by means of a threaded plug, calked in. Other means of stopping leaks, such as the use of shellac, cement, etc., should not be permitted. Head of plug- Threaded plug- * O^ Portable lever \ or handle ^ Holes for handle ^Hollow cylinder This space filled with red lead putty Space between improperly fitted plates to be gunned. 'This hole plugged after gunning is completed. FIG. 98. Red lead putty gun. Calking is tested by filling the compartment adjacent, with water (to a head corresponding to that pressure to which the bulkheads or other boundaries may be subjected), or with air under a corresponding pressure if with water, leaks can be seen directly; if with air, soapy water rubbed along the calking edges will cause bubbles to appear at leaky points. The necessary head for a water-pressure test may be secured by the use of a stand-pipe. 224 PRACTICAL SHIP PRODUCTION A surface which is properly calked should be equally tight when subjected to pressure from either side, but to be properly calked all of the calking should be done on one side, or on both sides. Calking of oil-tight work is especially important, and should be painstakingly and conscientiously done. 6. PROTECTION AGAINST CORROSION In order to be able to have a ship carry as great a weight of cargo, fuel, machinery, etc., as possible, the weight of the hull must be kept low. For this reason the thicknesses and sizes of the various structural members should be no greater than is necessary to secure the requisite strength. In almost all ships, however, the thicknesses of the struc- tural plates and shapes are made somewhat greater than necessary for strength alone, in order to provide against the effects of corrosion. Corrosion is the process of gradually wasting, or being eaten away, of steel or iron. It may occur uniformly, or may be more rapid in certain spots, in which latter case it is sometimes called pitting. Steel usually corrodes some- what faster than iron. Corrosion may be caused either by (1) rusting or (2) galvanic action, although it is usually due to a combination of both. (Occasionally corrosion is caused by the action of acids, as in coal bunkers, or where ashes come in contact with steel.) Rusting is the oxidation of the iron and steel when in contact with carbon dioxide, or CO 2 . Although commonly supposed to be caused by moisture, this ig not strictly true, since moisture alone is not sufficient. Iron or steel placed in pure water or pure air will not rust, but practically speak- ing water and air both always contain a certain percentage of C0 2 , so that some corrosion will always occur unless the surface of the iron or steel is properly protected, by some suitable coating, from the action of CO 2 . Corrosion is much more rapid when heat is present. Galvanic action is the flow of an electric current between THE BUILDING OF SHIP 225 two dissimilar metals immersed in an acid and in metallic contact. One of the dissimilar metals will always be elec- tropositive to the other so that current will flow through the acid from the former to the latter, and this flow of current is accompanied by a gradual wasting away of the metal that is electropositive to the other. Sea water, which contains various salts, acts like the acid of an electric cell, and if two different metals, for example copper and steel, are in metallic contact in it, one of them (in this case the steel) will gradually be eaten away. If zinc, which is electropositive to steel be placed near the copper the current will flow from the zinc and it, instead of the steel, will be eaten away. A common method of preventing corrosion of the bottom of a steel ship due to galvanic action is there- fore to place slabs or rings of rolled zinc, called zinc pro- tectors, or "zincs" on the hull at points near propellers, stern tube bushings, gudgeons, valves and other under-water fittings that are made of bronze, brass or similar composi- tions. Zincs are secured by screws or stud bolts and nuts. Also, where possible, brass or bronze should be insulated or covered with some non-conducting material. (Holes over the heads of brass bolts in composite or sheathed ships are filled in with Portland cement.) It should be noted that galvanic action, in general, occurs only below the water line, whereas rusting may take place anywhere. As a matter of fact rusting is most rapid along the water-line portion of the shell plating, which is al- ternately immersed and dried, or is " between wind and water," and also under boilers, where the temperature is high. Galvanic action may be caused by impurities in steel or by variations in its molecular composition. For example rust which is electronegative to steel will cause the steel to corrode away and the points of rivets which are affected by the hammering given them when driven will corrode away more slowly than the adjacent shell plating. The various coatings that may be applied to steel to 15 226 PRACTICAL SHIP PRODUCTION protect it from the action of CO 2 , and consequent rusting, are as follows: (1) Galvanizing. (2) Various kinds of paints or varnishes. (3) Portland cement. (4) Various bitumastic and other special compositions. Galvanizing consists in coating the outer surface of steel or iron plates, shapes, castings, or forgings with a thin layer of zinc. This may be done by dipping the parts in a bath of molten zinc or by the electrolytic or deposition process. The former is more generally used. The thin plates of destroyers, where saving of weight and consequent small margin against corrosion are important, are usually gal- vanized, as are most small iron and steel deck fittings such as rails, stanchions, ventilators, cleats, bitts and other such parts that are exposed to the weather, on all ships. Paints and varnishes have been discussed in Section 5 of Chapter II. It is very important, in applying any kind of a paint or other coating to iron or steel, that the surface be absolutely clean, dry and free from rust, oil, or any other foreign matter. The object to be achieved is to secure an absolutely perfect adherence of the paint to the pure iron or steel material, and this cannot be accomplished if mois- ture, grease, rust, etc., are present. If surfaces are properly prepared before paints are applied the results will be much more satisfactory. Owing to the difficulty of so preparing these surfaces, entirely satisfactory painting is seldom secured in practice, but it is very important that it should be, and it should always be aimed at. Rust under paint is often worse than if the surface were left bare, for it thus can go on unobserved. Portland cement is used to form passage ways for the pumping and drainage of water, oil, etc., and in such places as wash rooms, water closets, etc., being then often used in conjunction with tiling. Bituminous compositions are used very considerably for the various ballast and trimming tanks, coal bunkers, bilges, etc. THE BUILDING OF SHIPS 227 The efficacy of both cement and bitumastics (as of paints) is in great measure dependent upon the care with which the surfaces have been prepared. During the building of a ship it is especially important that all faying surfaces are properly cleaned and painted before the parts are finally bolted up for riveting. Also the removal of mill scale by pickling or other suitable means and the proper application of a priming coat of red lead on all exposed parts are important. (In connection with the subject of means taken to pre- vent corrosion see also Chapter II, Section 5.) 6. WELDING Although welding up until very recently has been used almost solely for repair work (and for such joining of parts as is incident to the making of forgings) it has during the year 1918 become developed to such an extent that it has actually been used for joining the various parts of a ship together, or, in fact, replacing riveting. A few facts con- cerning welding should therefore be noted. Welding, proper, consists in joining, under pressure, two pieces of metal that have been heated to a plastic con- dition, and as such is exemplified in ordinary blacksmith or forge work. Soldering consists in joining metal parts by means of an independent alloy which is fused, or melted and applied to them. A solder may thus be called a metallic cement. Autogenous soldering is the process of joining two metal parts by the fusing of a portion of some of their own material, and the term " welding" is now applied to autogenous soldering as well as to ordinary smith welding. The heating of the parts to be welded in the case of or- dinary pressure welding may be accomplished either in a forge or furnace (in which case the pressure is usually ap- plied by means of hammering) or by the resistance of an alternating electric current (the parts being then joined by being clamped or similarly pressed together). An example of this form of welding is what is known as spot 228 PRACTICAL SHIP PRODUCTION welding which gives a finished product somewhat re- sembling one that has been flush riveted. The principal forms of fusion welding are by means of the oxy-acetylene or oxy-hydrogen torch, "Thermit" welding and electric welding. Oxy-acetylene and Oxy-hydrogen Welding. In this process a blow-pipe or torch, is used to heat the surfaces to be welded to the fusing temperature. Oxygen and some combustible gas (acetylene, hydrogen, coal gas, etc.) are supplied to the blow-pipe from large flasks or cylinders by means of separate lengths of rubber hose fitted with suitable valves for adjusting the pressures. The oxygen and acetylene (or other gas) are combined in a mixing chamber, which is part of the torch, and the mixture is forced out of a small tuyere or nozzle at the end of the torch, and when ignited gives a flame of intense heat. Metal is gradually added to the junction of the parts to be connected and the weld thus built up. This process of welding is applicable, in general, only to relatively small parts and for the welding of large parts that have been broken, such as stem and stern castings, electric welding is more satisfactory. A modification of the oxy-acetylene blow-pipe, in the tip of which are several orifices or tuyeres, is used for cutting. The central orifice provides passage for a jet of pure oxygen called the cutting oxygen, and the outer orifices carry jets of the mixture of oxygen and combustible gas, called the preheating gas. Thermit welding consists in placing a mixture of aluminum and oxide of iron (Fe2Os) in a crucible over the parts to be welded, which are surrounded by a built up mold of re- fractory material after having been securely fixed in posi- tion. When the mixture is ignited a very high temperature is obtained and the melted iron, being allowed to run into the mold, heats the parts to a fusing temperature and amalgamates with them. This process has some applica- tion to the repair of large parts like stem and stern frames, THE BUILDING OF SHIPS 229 but has not always been entirely satisfactory, electric weld- ing being usually preferred to it. Electric Welding (Fusion). It is this form of welding that has recently come into such general use for ship re- pairing and shipbuilding purposes (as well as many others). The parts to be welded are brought to the highest known temperature by means of an electric current which forms an arc between two electrodes located, one or both, at or near the weld. The work itself usually forms one elec- trode though this is not always the case. Direct current is used, generally at about 100 volts, and with current varying between 50 and 500 amperes. Sometimes a carbon elec- trode is used in which case it is the negative one, so as not to carry carbon into the weld. More often the electrode is a slender rod or pencil of a composition similar to the parts to be welded and is carried in an insulated holder which the operator holds in his hand. It then forms the positive electrode and is itself deposited in the weld by the passage of current across the arc, and thus forms and builds up the weld. Metal electrodes may be bare or coated in various ways. In the Quasi-Arc process, used for ship welding, the coating is a special composition which melts as the pencil is used up and forms a flux which covers both the end of the pencil and the molten metal deposited in the weld, thus protecting them against oxidation. In July of 1918 the Technical Committee of Lloyd's Register decided that the application of arc welding to use in connecting the main structural members of ships ap- peared to be justified, although qualifying this decision by a statement to the effect that "the application should proceed cautiously in view of the unknown factors involved, the most important of which are the need of experience with the details of the welded joints and the necessity for training skilled workmen and supervisors." Various forms of welds are shown in Fig. 99. The width of the laps varies between 2 inches for 16-lb. plates and 3 inches for 40-lb. plates. The thickness of throat of a full weld varies 230 PRACTICAL SHIP PRODUCTION between K inch for 40-lb. plates and 0.28 inchfor 16-lb. plates. For lighter plates the outer surface of the weld is practically flat and makes an angle of 45 with the plates. The full weld is of course the strongest, and next in strength is the light closing weld. Tack welding is used where strength Weld I Thickness of Throat FULL WELD Full Weld (Large) u Weld 'LIGHT CLOSING WELD Weld, fel INTERMITTENT OR TACK. WELD FIG. 99. Electric quasi-arc welding. is not so important, only about 33 per cent, of the length of the edge being welded in this case. For satisfactory work the electrodes must be of uniform quality and the relation of their composition to that of the steel plates and shapes must be such as not unduly to re- duce the elasticity of the whole structure. The size of the electrode and the amperage must be ad- THE BUILDING OF SHIPS 231 justed to vary directly with the thickness of the plate or shape to be welded. Skilled workmanship is very important and care must be exercised to prevent, in so far as possible, oxidation of the deposited metal. This is accomplished by means of the flux formed by the coating of the electrode. The faying surfaces must be accurately fitted, and all butt connections must be strapped. Both edges of plates of butts of shell plating, deck and inner bottom plating, and plating of longitudinals, girders and hatch coamings should be connected by full welds. A full weld is applied to the outside edge and a light closing weld to the inside edge in the case of edges of shell, deck and inner bottom plating and butts and edges of bulk- head plating. Frames, beams, stiff eners, etc., have at the heel a light closing weld, and, at the toe, tack welding. All water- tight angle bars have continuous welding at each toe with tack welding at the heel. The great advantages of welded over riveted connections, such as saving in weight, doing away with the need for calking, saving in labor and time, etc., are too evident to require comment, and it only remains to be seen whether this method of building ships will prove as great a step in advance as it now gives promise of doing. 7. LAUNCHING When the under-water shell plating has been riveted and calked and the progress of construction of the ship other- wise is considered sufficiently advanced she is launched. The amount of work done previous to launching like the amount done before the laying of the keel may vary between wide limits. Where a yard is endeavoring to build a number of ships in a short time, so that the keel for one will be laid immediately after another has been launched, it is an advantage to launch as soon as possible. On the other hand, if extreme expedition is not so important, 232 PRACTICAL SHIP PRODUCTION it is usually advantageous to delay the launching until the hull is very nearly, if not entirely completed. When the hull is on the building slip it is practically rigid (and in some yards is entirely roofed over) so that it can be more efficiently worked upon. After the launching the ship may roll or list at times, thus interfering somewhat with work, and furthermore there may be no convenient dock or pier at which to moor her if launched too soon. In any case before a ship is launched sufficient work must have been done to give her the requisite buoyancy, strength and stability for flotation, and such parts as will be inaccessible for work on them with the vessel in the water must have been completed, unless as may be sometimes the case for special reasons she is to be placed in dry- dock prior to final completion. These parts include rudder, struts, propeller shafts and propellers, bilge and docking keels and various other miscellaneous underwater fittings. During the building of a ship a careful record should be kept of the locations and weights of all parts worked into the hull. With this data calculations are made, shortly before the launching, to determine what will be the exact launching weight of the ship (or her displacement when she takes the water) and what will be the exact location of the centre of gravity of the ship, as launched. Certain calculations are then ordinarily made (unless the ship is a duplicate of another already satisfactorily launched under the same conditions) to see that the ways are properly designed to prevent any accident during launching. The principal points to be looked out for in designing and preparing the ways are as follows: 1. Bearing pressure on ways. 2. Prevention of tipping. 3. Prevention of premature pivoting. 4. Strength of ways under point about which pivoting will occur. 5. General details of ways, cribbing, shoring, etc., to give sufficient strength at all points. Some of these points have been discussed in Section 2, of Chapter V, but the following should also be noted here : THE BUILDING OF SHIPS 233 Considering the ship at any instant during the launching, after she has moved a certain distance down the ways, the forces acting on her will be, as illustrated in Fig. 100: 1. The weight of the hull, W, acting vertically downward through the centre of gravity; 2. The force of buoyancy, B, acting vertically upward through the centre of buoyancy, or centre of figure of the immersed portion of the ship; and, Centre of Gravity of Hull Water Line End of Ways (fulcrum for. Tipping) Fore Poppets (fulcrum for Pivoting) FIG. 100. Forces acting on ships during launching. 3. The upward vertical support or reaction of the launch- ing ways which may be considered as resolved into two parallel compartments, Q and R, one acting through the end of the ways, and the other through the fore poppets which are located at or near the fore foot, and are the points furthest forward at which the hull receives any support from the ways. Referring again to the figure it will be seen that at the instant represented any one of three things may happen : (1) If the moment of the force of buoyancy, B about the 234 PRACTICAL SHIP PRODUCTION end of the ways is equal to the moment of the weight, W about the end of the ways (or if B X a = W X 6), the ship will tip, and at that instant all of the support of the ways will be concentrated at their end, or R will vanish, and Q will be equal to (W B). (2) If the moment of the force of buoyancy, B about the fore poppets is equal to the moment of the weight, W about the fore poppets (or if B X c = W X d), the ship will pivot, and at that instant all of the support of the ways will be concentrated at the fore poppets, or Q will vanish, and R will equal to (W-B). (3) If neither of the two preceding happens the ship will continue to move down the ways until one or the other of them does happen. By calculating the values referred to in (1) and (2) for several different assumed positions of the ship, at intervals during her movement down the ways, curves may be plotted, having for abscissas the amounts of travel of the ship from her initial position, and for ordinates the corresponding values of B, (B X a), (W X b), (B X c) and (W X d). From these curves the point at which tipping will occur (if at all), the point at which pivoting will occur, and the reaction of the ways, in either case, may be found graphically. This information is necessary to check the length of the ways, and their declivity and strength, the necessary strength for the fore poppets, and the point under which the ways should be reinforced to take the pressure of the fore poppets when the stern lifts. In finding the various values of B, and the locations of the line through which it acts, it is convenient to draw a set of curves called Bonjearis Curves, which consist of a curve drawn for each frame station of the lines,' the abscissa of which at any height above the base line equals, to scale, the area of that frame station up to that height. These curves, used in conjunction with Simpson's or some similar rule, furnish a convenient means for determining successive values of B and a. (In making these calculations the THE BUILDING OF SHIPS 235 height of the tide at the hour set for launching must be taken into account.) The fore poppets are portions of the crib work over the forward end of the launching ways, one under each bow of the ship. Ordinarily they consist merely of heavy timbers built up in a manner similar to the rest of the crib- bing, but in very large ships they may be made in the form of actual trunnion bearings, constructed of steel and con- crete, with trunnions attached to the hull. The general arrangement of the standing and sliding ways and the cribbing is shown in Fig. 71. Shortly before the date set for launching the standing or ground ways are laid in position and properly blocked up, secured and shored to prevent spreading. Their upper surfaces are then coated with some suitable launching grease (usually containing tallow, etc.), and the sliding ways, their lower surfaces having been similarly greased, are placed in posi- tion and the cribbing which is to transmit the weight of the hull to the sliding ways is installed, loosely, wedges between it and the sliding ways being not set up. The above procedure should take place as short a time before the launching as possible in order to prevent the grease from melting or being squeezed out from between the timbers. During this time the hull is supported by the keel blocks and by shores and blocks kept clear of the launching ways. On the day of the launching a carefully prepared schedule of operations is carried out and all arrangements must be made in advance so that there will be no hitch, and so that the launching will take place with the desired height of tide. A large gang of men must be detailed for the wedging up and other tasks incident to the launching and all must know exactly what to do and at whose order it is to be done. Absolute unity of action is necessary in order to prevent mishaps. The wedging up is done at the word of the official in charge and should be so timed as to have the vessel borne by the ways for as short an in- terval as possible before the launching. This interval must 236 PRACTICAL SHIP PRODUCTION necessarily be the time necessary for splitting out or other- wise removing the keel blocks, and removing shores, blocking and other material that would obstruct the launching. When the word to wedge-up is given all the workmen as- signed to that duty quickly drive home the wedges so that the weight of the hull is transferred, as much as possible, from the keel blocks and shores to the cribbing and launch- ing ways. The removal of the keel blocks and shores, etc. (which follows the wedging up as rapidly as possible) completes this transfer, so that the entire weight is finally taken by the launching ways as shown in Fig. 71. (To facilitate quick removal of the keel blocks they are some- times made in the form of metal boxes containing sand, and so constructed that the sand may be allowed to run out and the load thus be removed.) The launching is accomplished by various forms of re- leasing devices or triggers, some quite elaborate (such as hydraulic cylinders and pistons) and others very simple (such as two pieces of timber retaining the sliding ways which are sawed off simultaneously.) Before the launching the ship must be properly shored internally' to take any stresses that are anticipated and her stability must be investigated, suitable ballast being added if there is any doubt. As the ship slides down the ways considerable momentum may be acquired and it is sometimes necessary to provide means for checking her sternway after she strikes the water. Means for doing this vary with the conditions, a common one being to have heavy cables stopped to the ship at intervals, the stops to be broken by the momentum which is thus gradually destroyed. Tugs then transfer the ship other fitting out pier. The launching of the ship, which is an important event in her production is almost always made the occasion for a suitable ceremony and celebration. As the ship starts to move the lady chosen as her sponsor breaks a bottle of champagne over the bow and christens the ship. For this THE BUILDING OF SHIPS 237 purpose a large platform is temporarily built up just forward of the bow, supported by heavy scaffolding, and surrounded by a stout railing. On this platform are stationed the sponsor and the launching party. After the ship is in the water a luncheon and celebration is usually given. 8. FITTING OUT The work done on a ship after she has been launched and before she is finally completed and delivered to the owner consists, in general, in the completion of the struc- tural work of the hull that was not accomplished prior to launching, and the installation of various piping, ventila- tion, and electrical systems, joiner work, deck fittings, auxiliary machinery, engines and boilers (if not installed before the launching), smoke stacks, ventilators, spars, rigging, bridges, deck houses, etc., and a great variety of other miscellaneous parts and trimmings. In addition to this, numerous tests must be made to see that , everything is in satisfactory working order, the various articles of equipment must be supplied, and the hull cleaned and freed of rubbish and other foreign matter, and all necessary painting done. The greater portion of this work covers the operations of such trades as those of the plumbers, pipe fitters, joiners, shipwrights, riggers, electricians, machinists, painters, etc., and a full discussion of the various details involved would occupy too much space to be undertaken here. It is really fitting out, rather than building, a ship; and a large part of it is very similar to work done by the same trades on shore. Certain important points that apply to shipbuilding in particular should, however, be noted. As is natural, during the latter stages in the construction of a ship, when the time for her delivery to the owners is drawing near, it is important to check up and see if all of the requirements of ships (see Chapter I) have been complied with. The buoyancy is, of course, demonstrated, in general, 238 PRACTICAL SHIP PRODUCTION by the fact that the vessel floats after launching and that she has been built in accordance with the plans. Any leaks that develop in the shell plating after launching will, of course, be remedied in so far as possible when noted, and if necessary the vessel will be dry-docked and the leaks calked. There is also to be considered, in connection with the subject of buoyancy, however, the question of integrity of water-tight subdivision. A portion of this has probably been demonstrated before the launching by tests of bulk- heads and compartments which have been subjected to a sufficient head of water. During the last stages of con- struction it is very important to see that this integrity is not destroyed by the cutting of holes in bulkheads and decks. It is practically impossible to avoid having some holes in water-tight bulkheads and decks, both for doors, manholes, etc., and for piping and wiring. The former must be of the water-tight type, and wherever a water-tight plated surface is pierced by a pipe or conduit the construction must be so arranged as to prevent the passage of water around that pipe or conduit. This is accomplished by the use of flanges or stuffing boxes, which must be carefully made and installed and properly packed with suitable gaskets or packing, as the case may be. Means for the attachment of brackets, castings, hangers, etc., to water-tight members must be such as not to destroy or impair their water- tightness. Constant and conscientious supervision is necessary to attain these results. Stability depends largely upon the correct execution of design, and one very important check on this is the deter- mination of the actual transverse metacentric height of the ship by means of an inclining experiment, which should, if possible, be conducted as the ship is nearing completion. This consists in heeling the ship over to various small inclinations by means of moving heavy weights across the decks and recording the amount of weight moved, the thwart ship distance through which it is moved, and the THE BUILDING OF SHIPS 239 angle of heel, in each case. The displacement is also care- fully noted. The operation is illustrated in Fig. 101, the angle of heel, 0, being measured by means of a plumb bob and graduated scale, as shown. The inclination, 6 is in this case pro- duced by the movement of the weight, w a distance, /, transversely. Let W be the total displacement of the ship, and let G r and B f (which must be in the same vertical line) FIG. 101. Inclining experiment. be the new centres of gravity and buoyancy. Then, by taking moments, W XGG' = wX I and GG' wXl GM = a tan B ~ W tan but tan = T (which has been recorded) w XlXh aXW A number of different "check" readings are taken and if 240 PRACTICAL SHIP PRODUCTION these all agree the calculated value of the metacentric height, GM, may be assumed to be fairly accurate. During the experiment the ship must be entirely free from the action of any external force or forces, and there must be no " loose' ' weights on board such as water in tanks not completely filled. The longitudinal metacentric height may be found simi- larly and this is usually done in the case of the submerged inclining experiment of a submarine. (In this connection it should be noted that the metacentre of a submerged body coincides with the centre of buoyancy.) The propulsion of the ship is checked, usually, by dock trialSj and a trial trip, before being accepted by the owners. Similarly the steering gear should be very thoroughly tried out before delivery of the vessel. These are, of course, actual operating tests. Strength must, of course, depend largely upon good workmanship and a strict compliance with the plans and specifications. During the latter stages of construction it is important to see that the strength is not impaired by holes or notches, etc. cut in various structural members, during the installation of piping systems and other fittings, etc. This also requires careful and conscientious supervi- sion. Holes drilled through beams should be near the centre or in the upper half of the web and should be in only one horizontal row. The diameter of such holes should not be over about 20 % of the depth of the beam and holes should not be too close together. Whenever alterations are made in the design of a ship during the building great care should be used to see that the strength is not there- by impaired. As has been said before, however, honest, skillful, conscientious workmanship, at all times, is of fun- damental importance in securing the necessary strength in a ship. Endurance is demonstrated by the fuel consumption on the trial trip and a checking up or calibration of the bunkers. This consists in taking accurate measurements of coal bunkers or fuel oil tanks and calculating their capacities. THE BUILDING OF SHIPS 241 For oil tanks it is done by filling them with water from ac- curately graduated measuring tanks. The data thus ob- tained is furnished to the owners with the ship. The utility of the ship depends upon a compliance with the plans and specifications. During the latter stages of construction care should be exercised to see that the mul- titudinous details, all of which make for utility, are looked out for. This applies also to living spaces and accommo- dations and similar considerations affecting the health and comfort of the crew and officers. Throughout the various processes of ship production the objects to be attained should always be kept in mind, for it is only by knowing what is wanted that it can ever be completely obtained. Each and every man connected with the production of ships should realize his responsibili- ties, and endeavor conscientiously to see that his part of the job is properly done. 16 INDEX. Aft, 34 After peak tank, 45 After perpendicular, 36 Afterbody, 35 Air holes, 90 American Bureau of Shipping, 63 Amidships, 34 Anchor windlass, 47 Anchors, 47 Angle bar, 64 in frames, 79 of maximum stability, 9 of vanishing stability, 9 Anglesmiths, 171 Arc welding, 229 Area of wetted surface, 143 Armored cruisers, 55 Arrangement of a ship, 41 Asbestos used on ships, 72 Athwartships, 2, 34 Atwood's formula, 139 Autogenous soldering, 227 Auxiliary vessels, 57 Average secant, 144 B Balanced rudders, 21, 95 Ballast, 47 Bar keels, 77 Base line, 31, 35 Battens, 182 Battle cruisers, 55 Battleships, 54 Beam knee, 114 Beam mold, 192 of ship, 2 Beams, deck, 114 Beams, fabrication, 192 Belt frames, 82 Bending frames, 168 moment, curve of, 27 slabs, 162 Bevel boards, 185, 188 of a frame, 79, 83 Beveling bars, 191 frames, 168 Bibliography of naval architecture, 145 Bilge, 39 diagonal, 32 keels, 128, 129 keelsons, 83 stringers, 85 Bilges, 12 Bitts, 127 Bituminous compositions, 73, 226 Block coefficient of fineness, 40, 41 Blow pipe, oxy-acetylene, 167 used in welding, 228 Boat deck, 48 Boatbuilders, 178 Body plan, 32 post, 94 Boiler room, 46 Boilers, supporting, 125 Bolsters, 127 Bolters-up, 175 Bolting up ship frames, 206 Bon jean's curves, 234 Bosom piece, 173 Boss, 39 Bossed frames, 101 plates, 107 Bottom, 37 double, 47, 85 inner, 47, 106 Bounding bars, 122 243 244 INDEX Bounding, fabrication, 192 of deck plating, 116 Bow, 12, 39 and buttock lines, 32 Bracket floors, 89 Brackets, 83, 114, 173 fabrication, 192 shaft, 103 Brass in ship construction, 70 Breadth, molded, 36 Breast hooks, 27, 90 Bridge, 48 British Corporation, 63 Broadside launching, 157 Bronze in ship construction, 70 Building ships, 195-241 bolting up, 204 calking, 219 chipping, 219 drilling, 207 erection, 195 fitting out, 237 launching, 231 protection against corrosion, 224 reaming, 205 riveting, 209 testing, 237 welding, 227 slip, 147, 148 Buildings in shipyards, 159 Bulb angles, 65 Bulkhead liners, 112 plating, fabrication, 187 stiffeners, 44, 122 fabrication, 192 Bulkheads, 44, 121 water-tight, 124 Bulwarks, 39, 128 Buoyancy, 3, 233, 237 calculation of, 137 centre of, 4 curve of, 26 Bureau Veritas, 63 Butt-strap, 173 Buttock lines, 32 Button-head rivet, 67 points, 68 Butts, 107 calking, 220 Calculations in ship design, methods, 136, 146 of strength, 25 Calibration of bunkers, 240 Calkers, 176, 177 Calking, 219 testing, 223 Camber, 37 Cant frames, 90 Canvas, used in ships, 72, 120 Cargo booms, 48, 49 hatches, 45 vessels, 58 Carlings, 114 Carrying capacity, 62 Castings, steel, 64 Cellular double bottom, 86 Cements, 72-74 Centre keelson, 78 lines, 2 of buoyancy, 4 shafts, 101 vertical keel, 78 Chain cables, 47 locker, 47 pipes, 47, 127 Chamfering, 110 Channels, steel, 65 Chart house, 48 Chippers, 176 Chipping, 219 Chocks, 127 Classification societies, 62 Cleats, 127 Clinker strakes, 112 system of plating, 107 Clips, 83, 173 Coal bunkers, 46 Coamings, 45, 114 Coefficients of form, 39 Cofferdams, 129 Collision bulkhead, 45 Comparison, Froude's law of, 19 Composite ships, 51 Concrete ships, 52, 53 Coned neck rivet, 68 Construction of ships, preliminary steps, 180-194 INDEX 245 Construction of ships, transverse and longitudinal framing, 78 See also .Building ships. Copper in ship construction, 70 Coppersmiths, 177 Cork, 72 Correction to displacement, 142 Corresponding speeds of ships, 18 Corrosion, protection against, 224 Cotton, 72 Counter, 39, 98, 99 Countersinking rivet holes, 166 Countersunk head rivet, 67 points, 68 Cranes in shipyards, 158 Crew's quarters, 48 Cribbing of ways, 235 Cross curves of stability, 140 sections, 32 Crown, 37 Cruiser sterns, 94 Cruisers, 55 Curve of bending moment, 27 of buoyancy, 26 of dynamical stability, 140 of load, 27 of shearing force, 27 of statical stability, 140 of weight, 26 Dead flat, 31 rise, 37 weight, carrying capacity, 62 wood, 39 Deck beams, 23, 114 fabrication, 192 girders, 119 Deck plating, 114, 115 fabrication, 187 wood over, 117 Decks, 44, 114 water tight, 120 Deep frames, 82 Definitions of terms, 2 terms referring to form, 34, 37 Denny's formula for wetted surface, 143 Depth, molded, 36- - Depth of ship, defined, 2 Derrick posts, 48 Design of ships, 130-146 Designers in shipyards, 170 Designing the ways, 232 Destroyers, 56 Diagonals, 32 Dimensions, molded, 36 of ships, defined, 1 Directions on a ship, 34 Dished plates, 107 Displacement, 16, 61 calculation of, 137 correction to, 142 Dock trials, 240 Docking keel, 128 Dolly-bar, 211 Double bottom, 47, 85 Draft of a ship, 2, 36 Draftsmen in shipyards, 170 Drag, 36 Drainage wells, 90, 129 Drift pin, 175 Drillers, 175 Drilling machine, pneumatic, 207 rivet holes, 166 ship frames, 207 Drop-forgers, 177 strakes, 111 Dry-docking, 52 Dutchmen, 222 E Edge calking, 220 Edges of plating, 107 Electric welding, 229 Electricians, 178 Electrodes. 229 Enamel, 74 Endurance of ships, 28 testing, 240 Engine foundations, 125 room, 46 Entrance, 37 Equilibrium defined, 7 Erection of ship frames, 195 Erectors, 175 Expansion trunks, 49 Extreme drafti 36 246 INDEX Fabricating and erecting shops, 162 Fairing the lines, 34 Faying surface, 68, 165, 187 Fenders, 128 Fitters-up, 173 Fitting out a ship, 237 Flanges, 238 transverse and longitudinal, in a frame, 79 Flanging plates, 166, 187 Flare, 37 Flat plate keel, 78 Flitches, 71 Floating bodies, law of, 4, 5 Floor plates, 81 fabrication, 191 Floors, bracket, 89 solid, 89 Flush system plating, 108 Fore, 34 Fore-body, 35 Fore foot, 39 poppets, 233-235 Forgers, 177 Forging steel, 167 Forgings, steel, 63 Form of ships, 31 coefficients of, 39 definition of terms, 37 Formula, Atwood's, 139 Formulae for calculations of weight, etc., 136-146 for wetted surface, 143 Forward, 34 peak tank, 45 perpendicular, 36 Fouling, means of preventing, 72 Foundations, engine, 125 Frame benders, 171 bending and beveling, 168 spacing, 78 Frames, bossed, 101 erecting, 195 fabrication, 188 spectacle, 103 Framing of ships, 23, 41, 42, 77 Isherwood system, 58, 90 longitudinal system, 90 Framing of ships, transverse system, 77,90 Freeboard, 2, 37 Froude, William, 18 Froude's law of comparison, 19 Full load displacement tonnage, 62 Furnaced plates, 106, 168, 187 Furnacemen, 171 Furnaces in shipyards, 162 Fusion, 229 G Galley, 48 Galvanic action on steel, 224 Galvanizers, 177 Galvanizing, 226 Garboard strake, 107 Gasket, 120 Girder strength, 24 Girders, 23 deck, 120 Girthing frames, 181 Greasing ways, 235 Gross tonnage, 61 Gudgeons, 21, 94, 97 Gunboats, 56 Half-breadth plan, 32 Half-breadths, 31 Hammered points of rivets, 68 Hand riveting, 216 Harpins, 203 Hawse pipes, 47, 127 Heart of timber, 71 Heaters, 175, 176 Height, metacentric, 7, 8, 137, 240 Heights, 31 Helm, 20 Hogging, 25 Holders-on, 175, 176 Holding-on, 211 Holds, 45 Hull, 22, 42 machinists, 177 material, fabrication of, 185 Hydraulic riveting, 168, 216 INDEX 247 I-beam, 66 Inboard, 34 profile plan, 135 Inclining experiment, 238 Initial stability, 7 Inner bottom, 47, 106 plating, 113 fabrication, 187 Intercostal plates, 84 Interior arrangement of ships, 42 Iron for ship construction, 69 ships, 51 Isherwood system of framing, 58, 90 Joggling, 109, 167 Joiner shop, 163 Joiners, 177 K Keel line, 35 plates, fabrication, 191 Keels, 23, 42, 77 bilge, 128, 129 docking, 128 laying, 195 Keelsons, 23, 83 Kirk's analysis, 143 Knees, 71 beam, 114 Knuckle, 39 Laborers, 175 Landing edges, 107, 135 Lap-joint, 174 Launching ships, 231 broadside, 157 greasing ways, 235 . plotting curves for positions of ship, 234 wedging up, 235, 236 forces acting on ship during, 233 Launching ways, 147, 152 designing, 232 Law of comparison, Froude's, 18 of floating bodies, 4, 5 Layers-out, 171 Laying of the keel, 195 -out shed, 162 Layout of shipyard, 157 Lead for ship construction, 71 Length between perpendiculars, 36 over all, 36 Lightening holes, 83, 173 Limber holes, 83, 90 Liners, bulkhead, 112 in a frame, 83 in shell plating, 107, 174 passenger, 57 Lines, fairing, 34 of ships, 31, 32 reference, 35 Linoleum, 72 on decks, 116, 120 Liverpool rivet point, 68 Lloyd's Register, 62, 229 Load, curve of, 27 draft, 36 water line, 32, 35 coefficient, 40 Local strength, 27 Loft, mold, 161 Loftsmen, 171 Longitudinal bulkheads, 45, 122 metacentric height, 240 prismatic coefficient, 40 strength, 24, 25 system of framing, 77, 90 Longitudinals, 23, 86 fabrication, 192 Lugs, 83 M Machine riveting, 207, 216 tools in shipyards, 163 Machinists, hull, 177 Main deck, 44 Management of a shipyard, 178 Manganese bronze in ship construc- tion, 70 Manholes, punching, 167 Margin planks, 117 plate, 87, 113 Masons, 178 248 INDEX Masts, 48 Materials for ship construction, C!> weights, 76 ordering, 180 Mean draft, 36 Melters, 178 Merchant ships, 57 rudders, 98 Metacentre, 7 Metacentric height, 7, 8 calculations, 137 longitudinal, 240 Method of comparison, to determine power required, 14 Midship section, 31, 36 coefficient, 40 plan, 134 Mild steel, 69 Mining vessels, 56 Modified girths, 143 Mold loft, 161 offsets, 182 Molded dimensions, 36 Molders, 178 Molds, making, 182 Moment to change trim, 141 Moon bars, 168, 190 N Naval architecture, bibliography, 145 brass, in ship construction, 70 Net tonnage, 61 Neutral equilibrium, 7 Oakum, 72 Offsets, 182 Oil stops, 205, 222 Oil-tight riveting, 217 Ordering material for ships, 180 Outboard, 34 profile plan, 135 Oxter plates, 107 Oxy-acetylene blow pipe, 167 welding, 228 Oxy-hydrogen welding, 228 Painters, 178 Paints, anti-corrosive, 226 for smoke stacks, 75 for steel strips, 72 Pan-head rivets, 67 Panting, 27 stringers, 27, 90 Passenger vessels, 57 Passers, 175 Passing strakes, 111 Pattern makers, 178 Peak tanks, 45 Personnel of a shipyard, 169 Phosphor bronze, in ship construc- tion, 70 Pickling plates, 187 Piling in shipyards, 148 Pillars, between decks, 118 Pintles, 21, 94, 96 Pipe fitters, 177 Pipe stanchion, 118 Pipes, chain, 127 hawse, 47, 127 Pitting of steel, 224 Pivoting of ship in launching, 155, 234 Plate and angle shop, 162 bending, 163 margin, 113 planer, 165 racks in shipyards, 161 rider, 113 Plates, fabrication of, 186-192 floor, 81, 191 furnaced, 168 intercostal, 84 ram, 90 steel, 64 Planes, reference, 35 Planing plates, 165 Planking, deck, 114, 115 Plans, for ship design, 32, 134 Plating, deck, 114, 115 fabrication, 186 of bulkheads, 122 shell, 42, 106 Plumbers, 177 Pneumatic drilling machine,, 2Q7 INDEX 249 Port side, 20, 35 Portland cement used in steel ships, 75, 226 Power required for propulsion of ship, 14 Prismatic coefficient, 40 Profile plan, 32, 135 Propeller post, 39, 94 screw, 14 struts, 100 Propulsion of ships, 11 means of, 13 testing, 240 Protected cruisers, 55 Punching and shearing shop, 162 holes, 165, 186 manholes, 167 Putty gun, red lead, 222 Q Quarter, 39 Quasi-arc process of welding, 229 Rabbetting, 92 R Radio room, 48 Rail, 39, 128 Ram plates, 27, 90 Range of stability, 9 Rating of ships, 63 Ratio of beam to draft, 40, 41 of length to beam, 40, 41 Reamers, 175 Reaming rivet holes, 166 ship frames, 205 Red lead putty gun, 222 Reference lines, and planes, 35 Register of shipping, Lloyd's, 62, 229 Reinforced concrete ships, 53 Requirements of ships, 2-30 buoyancy, 3 endurance, 28 propulsion, 11 stability, 5 steering, 20 strength, 22 testing for, 237 utility, 29 Residual resistance, 19 Resistance of a ship, 15 Reverse frames, 80 fabrication, 188 Ribbands, 202 Rider plate, 113 Riggers, 175, 177 Righting arm, 7, 8 Rise of bottom or floor, 37 Rivet holes, punching, 165, 186 size, 215 Rivet-passers, 176 Riveters, 175 Riveting, 209 hand, 216 hydraulic, 168, 216 machine, 206, 207 special instructions, 218 speed, 214 Rivets, 66 diameters, 215 tack, 217 tap, 216 Rolling chocks, 129 of plates, 187 Rolls, plate bending, 164 Rope, 72 Round up, 37 Rubber, 72 Rudder post, 21, 39, 94 Rudders, 20, 95 balanced, 21 Run, 37 Rusting of steel, 224 S Saddles, 125 Sagging, 25 Sawing steel, 166 Scantlings, 66 Scarph, 91 Scouts, 56 Screw propellers, 14 vessels, 100 Scrieve board, 183 Seam straps, 108 Seams, 107 Second deck, 44 Set iron, 168 250 INDEX Shaft bracket, 103 tubes, 100 tunnels, 46 Shafts, wing, 101, 102 Shakes, in wood, 71 Shapes, steel, 64 Shearing force, curve of, 27 plates, etc., 165 Sheathed ships, 52 Sheer, 37 plan, 32 strake, 107 Sheet metal workers, 177 Sheets, steel, 64 Shell expansion plan, 134 Shell plating, 42, 106 fabrication of, 186 inner bottom, 113 seam systems, 107 thickness at ends, 112 Shellac for ships, 75 Shelter deck, 44 Shift of butts, 111 Shipfitters, 172 Ships, building, 195-241 buoyancy, 3 description, general, 31 design, 130-146 dimensions denned, 1 endurance, 28 interior arrangement, 42 law of floating bodies, 4, 5 plans, 32 propulsion, 11 requirements, 2 resistance of, 15 similar, denned, 18 speed of, 60 stability, 5 steering, 20 strength, 22 structural members, 77 tonnage of, 61 types of, 50 Shipsmiths, 177 Shipwright shop, 163 Shipwrights, 50, 177 Shipyards, 147-179 building slip, 147, 148 buildings necessary, 159 Shipyards equipment, 169 launching ways, 147, 152 layout, 157 machine tools, 163 management, 178 on Great Lakes, 157 personnel, 169 piling, 148 site, 147 steel fabricating processes, 163 transporting materials, 158 traveling cranes, 158 Shops, in shipyards, 162 Sight edges, 107 Sides, 39 Similar ships denned, 18 Simpson's rules, 144, 145, 234 Single plate rudder, 96 Slabs, bending, 162 Smith shop, 162 Smoke stack paints, 75 Snugs, 96 Soldering, 227 Solid floors, 89 Solution, to cover steel in ships, 73 Spardeck, 44 Spectacle frames, 103 Speed of production of steel ships, 214 of ships, 60 Speeds, corresponding, 18 Spot welding, 227 Squeezer, 168 Stability, 5 angle of maximum, 9 of vanishing, 9 calculations, 138 cross curves of, 140 dynamical, 140 inclining experiment, 238 initial, 7 range of, 9 statical, 140 Stable equilibrium, 7 Stanchions, between decks, 118 Staples, 117 Starboard, 20, 35 Statical stability, 140 Stealers, 111 INDEX 251 Steel for ships, 63 processes of fabrication, 163 protection against corrosion, 224 quality, 69 Steel frames, 23 Steel ships, 52 anti-fouling process, 72 paints for, 72 speed of production, 214 Steering, 20 engine room, 47 Stem, 37, 42, 91 Stern defined, 12 post, or frame, 37, 42, 91, 93 tube, 100, 104 Stiff eners, bulkhead, 44, 122 Stopwaters, 205, 222 Storerooms, 48 Strains in ships, 25 Strakes, 106 clinker, 112 drop, 111 passing, 111 Stream lines, 12 Strength of ships, 22 curves for calculations of, 26 girder, 24 local, 27 longitudinal, 24, 25 Stringers, 23, 83, 84 panting, 90 Structural members of ships, 77 Struts, 103 propeller, 100 Stuffing box, rudder head, 99 Submarine Boat Corporation, 159 Submarines, 56 Sunken and raised system of plating, 107, 109 Superdreadnoughts, 54 Surface, molded, 36 Tankers, 58 Tanks, double bottom, 47 peak, 45 Tap rivets, 216 Taylor's formula for wetted surface, 143 Templates, 161, 183, 193 Testers, 176 Testing ships, 237 Thermit welding, 228 Tiller, 20 Tipping of ship during launching, 155, 234 Tonnage of ships, 61 Tons per inch immersion, 141 Torpedo craft, 56 Tramp steamers, 58 Transportation of materials in ship- yards, 158 Transverse bulkheads, 44, 122, 124 metacentre, 7 system of framing, 77, 90 Trapezoidal rule, 144, 145 Traveling cranes in shipyards, 158 Trim, 36 Trimming ship, 45 Trunk, 46 Tubes, stern, 100 Tugs, 59 Tumble home, 37 Tween decks, 44 Types of ships, 50 U Unstable equilibrium, 7 Upper deck, 44 Uptake, 46 Utility, 29 T-bar, 66 T-bulb, 66 Tack rivets, 217 welding, 230 Tank top, 47 Varnishers, 178 Varnishes, anti-corrosive, 75, 226 Ventilating ducts, 49 Vertical prismatic coefficient, 40 252 INDEX W Wane, 71 Warships, 53, 54 construction, 88 rudders, 97 stem, 91, 93 stern post, 94 Water line, 2 lines, 32 Water-tight bulkheads, 124 decks, 120 -tightness, testing, 238 Ways, launching, 147, 152 designing, 232 greasing, 235 Weather deck, 44 Web frames, 82 Wedging up ship on ways, 235, 236 Weight, calculating for launching ship, 234 calculation in ship design, 136 curve of, 26 groups, in ship design, 133 of materials for ship construc- tion, 76 Welding steel, 167, 227 Welding, arc, 229 electric, 229 oxy-acetylene and oxy-hydro- gen, 228 tack, 230 thermit, 228 Welds, forms of, 229 Wetted surface, area of, 143 Winches, 49 Wing propellers, 101 shafts, 101, 102 Wood calkers, 177 for deck plating, 117 in ship construction, 71 Wooden ships, 50 Workmen in a shipyard, 169 Wring-off head on rivets, 216 Yoke, 100 Z-bars, 65 Zinc in ship construction, 70 protectors, 225 BOOK IS DUE ON THE LAST DATE STAMPED BELOW AN INITIAL FINE OF 25 CENTS WILL. BE ASSESSED FOR FAILURE TO RETURN THIS BOOK ON THE DATE DUE. THE PENALTY WILL INCREASE TO SO CENTS ON THE FOURTH DAY AND TO $1.OO ON THE SEVENTH DAY OVERDUE. AUG 24 1942 DEC 23 1942 JUM 15 1943 A nn ^i tsf- * r\ M j\ WH JS I9'(h LD 21-100m-7,'40 (6936s) YC 66317 :J93750 UNIVERSITY OF CALIFORNIA LIBRARY