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WOODEN HULL 
 
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 Originally issued by: 
 
 MERCHANT MARINE TECHNICAL DIVISION 
 
 OFFICE OF MERCHANT MARINE SAFETY 
 
 U.S. COAST GUARD 
 
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 ^ . CONTENTS 
 
 ^-O^EST PRODUCTS 
 
 I. INTRODUCTION ^^\ 
 
 II. GUIDE TO INSPECTION 2 
 
 A. General --------------______-___ 2 
 
 B. Hull Deficiencies ----------__--__•__ 2 
 
 C. Structural Problems ---------_-_-__-_» 2 
 
 D. Condition of Vessel for Inspection — _-..___ 2 
 
 E. Visual Inspection ----------_-_-_«___ 3 
 
 F. Inspection for Decay and Marine Borers --------- 3 
 
 G. Inspection of Fastenings -----------__-__ 5 
 
 H. Inspection of Caulking ----------..-_««._ 5 
 
 I. Inspection of Fittings -----------_____« 6 
 
 J. Hull Damage --_ «_ 5 
 
 K. Deficiencies --------------________ y 
 
 :il. REPAIRS 8 
 
 A. General ----- — ^ 8 
 
 B. Planking Repair and Notes on Joints 8 
 
 C. Framing Repair -------- ---_--«____ 13 
 
 D. Use of Fiberglass Reinforced Plastic Hi 
 
 IV. MATERIALS ._ li; 
 
 A. Wood --_ « i\x 
 
 B. Mechanical Fastenings ----------_--__-_ 17 
 
 C. Glues and Gluing 23 
 
 D. Wood Preservatives --------------_-_-._ 2\\. 
 
 V. DETERIORATION 28 
 
 A. Decay 28 
 
 B. Marine Borers --------------__-__-_ 29 
 
 VI. SKETCHES OF WOODEN CONSTRUCTION,. ETC, 31 
 
 A. Sketches ----------------_--_----. 31 
 
 B. Glossary _ . 37 
 
 /II. REFERENCES 1^3 
 
ACKNOWLEDGMENT Y\/ (g I 
 
 The information contained herein relating to good practice in Tt (CO 
 the inspection and repair of wooden vessels was originally 
 prepared by the Merchant Marine Technical Division, Office of 
 Merchant Marine Safety, U.S. Coast Guard, for Coast Guard Marine 
 Inspectors, commercial marine surveyors, vessel owners and 
 shipyards. 
 
 The information and suggestions were compiled from sources 
 believed to be reliable, but correctness or completeness cannot be 
 guaranteed. 
 
 I. INTRODUCTION 
 
 This publication has been prepared as a result of requests 
 from the field for information concerning the inspection and 
 repair of wooden hulls. These notes are intended as an aid to 
 responsible persons in promoting uniformity in inspection 
 procedures and in developing standards for their localities which 
 reflect the overall concept of "good practice" with specific 
 modifications dictated by local conditions. This information is 
 furnished for guidance purposes. Where specifics are given, it 
 should be understood that mandatory application is not necessarily 
 intended. Nothing herein shall be taken as amending the applicable 
 regulations, or as prescribing or limiting the authority and 
 responsibility of the Officer in Charge, Marine Inspection, in the 
 exercise of his good judgement. 
 
 It is expected these notes will require modification in the 
 light of their use in the field. Comments and suggestions are 
 welcome and revisions will be issued as necessary. 
 
n. GUIDE TO INSPECTION 
 
 A. General 
 
 Intelligent inspection and repair of wooden construction 
 requires knowledge and judgment. Inspection is made to 
 determine that the vessel is safe and has a reasonable chance 
 of remaining so until the next scheduled inspection. A good 
 basic knowledge of wood construction and the deficiencies to 
 which it is susceptible is essential. 
 
 B. Hull Deficiencies 
 
 H nl 1 dp f -i f.i pnr.i f>.s in wooden vessels group themselves into 
 three categories: 
 
 1. Time 
 
 a. Decay 
 
 b. Marine borers 
 
 0. Electrolytic and Galvanic Action 
 
 2 . Stress 
 
 a. Cracks 
 
 b. Broken members 
 
 c. Failure of fastenings 
 
 d. Failure of caulking 
 
 3. Damage 
 
 a. Hull damage due to collision, grounding or to 
 normal wear and tear 
 
 C. Structural Problems 
 
 In wooden vessels structural problems develop in nearly new 
 vessels as well as in older ones. Deterioration, especially 
 that caused by decay and marine borers, can occur with surpris- 
 ing rapidity. Boats which have been free of such infestations 
 can become infected with slight changes in service area or 
 (^)eration. That the vessel was sound at its last inspection has 
 less bearing on the present condition of a wooden vessel than on 
 one of steel. 
 
 D. Condition of Vessel for Inspection 
 
 If practicable, inspect the vessel out of the water with the 
 interior of the hull opened up as much as possible. The bilges 
 and forepeak should be dry and reasonably clean and excess 
 tackle, tools and gear which might interfere with proper in- 
 spection should be cleared away. This is not always possible. 
 However hard to inspect (and thus hard to maintain) areas should 
 not be missed. 
 
Where the interior of the hxill has closely fitted ceiling or paneling, 
 STifficient access should be provided to allow examination of the interior 
 at selected locations. Apparent soundness of the ceiling should not be takan 
 as indicative of soundness beneath it. 
 
 E. Visual Inspection 
 
 An overall 1 exajnination of the hvill of a wooden vessel vhich has been 
 in service can give the inspector an idea of the portions where deficiencies 
 can be expected. Distorted planking, pulled butts, local damage and un- 
 explained wetness or weeping are tell tale indications. 
 
 Particular attention should be paid to stem, transom, region under the 
 covering boards, the wind and water area and around hull fittings. It is im- 
 possible to list each area of trouble in each type of boat. In general, 
 areas which are hard to maintain, have poor ventilation or are subject to 
 heavy stresses have the most deficiencies. 
 
 F. Inspection for Decay and Marine Borers 
 
 Serious deterioration of a wooden hull goes on within the wood itself 
 with little or no outward sign until it is well advanced. In order to spot 
 decayed (dry-rotted) wood, which has not progressed to the point where the 
 wood appears eroded and spongy, sounding with a hammer can be o^" \ise. Un- 
 sound wood will give a dead or dxill sound. Heavy timbers whose interiors 
 are rotted may give a distinctive drum like tone. Where the sound is not 
 that of good solid wood, the member is suspect. A probe or drill can then 
 be xised to determine the extent of decay. 
 
 It sho\ild be realized that decay progresses rapidly and that it is more 
 economical to eliminate small decayed areas early than to become involved in 
 costly major replacements caused by neglected decay. 
 
 It is imperative that indiscriminate probing and boring be avoided. 
 Holes made by a probe or drill in the hull exterior are potential entry 
 ways for marine borers. In the hull interior they allow easier moisture 
 penetration and thus aid in starting decay. 
 
 Probing and boring should be done carefully and only where there is 
 an indication from non destructive testing that the hull is unsound, not 
 as a matter of routine. 
 
 Holes made by boring should be plugged with dowels or plugs which are 
 glued in place, not merely driven into the wood. Plugs and dowels should 
 preferably be treated with wood preservative to prevent future trouble. 
 Areas which have been probed shotild be filled with a suitable compound. 
 When covering boards or other obscuring construction is involved, it is 
 often difficult to locate deteriorated members by pi^bing. In such cases, 
 when bolted or screwed fastenings are involved, check for tightness of 
 randomly selected fastenings. If the member is solid, the fastening thus 
 
set up will take hold at the beginning of the turn. If serious decay is 
 present the fastening will turn freely and fail to take a bite, indicating 
 soft and spongy wood. 
 
 Decay (dry-rot) is most often found in the following locations: 
 
 1. In the wind and water ai-ea. 
 
 2. Around overboard discharges and other fittings. 
 
 3. In the stem area. 
 U. At the transom. 
 Internally 
 
 1. AH areas that are poorly ventilated (especially the f orepeak) . 
 
 2. In the bilge especially at the turn and along the keel. 
 
 3. The lower courses of bulkhead planking. 
 
 U. Areas under refrigerators or other machinery which may drip 
 fresh water. 
 
 ^. In the area of butt blocks and longitudinal members where dirt 
 and debris may have retained fresh water. 
 
 6. At the heads of frames caused by fresh water leakage through 
 defective covering boards. 
 
 7. Where the futtocks of sawn frames join and at the faying surface 
 where the frame abuts the hull planking. 
 
 8. At the terminal ends of frames, floors, engine foundations, etc. 
 whei^ end grain is present. 
 
 Under freezing temperature conditions wood structural members with a 
 high moisture content, particularly in the bilge areas, may appear quite 
 sound when, in fact, they may be in advanced stages of decay. Periodic 
 examination of these areas should be conducted before freezing sets in or 
 after allowing sufficient time for thawing. 
 
 The other principal form of deterioration which goes on within the 
 wood is marine borer attack. Marine borers can attack any wood which is 
 beneath the water. No species of wood is immune to attack and no method 
 of protection of the wood is completely effective. 
 
Borers can enter the wood through hairline breaks in sheathing (either 
 copper or fiberglass) or through scrapes, nicks or tool narks in protective 
 bottom paints. If borer infestation is suspected a spot check of the wood 
 beneath the sheathing should be made. 
 
 A probe is the most effective tool to tise in the detection of borers. 
 Avoid over zealous probing since each probe hole is a potential site of borer 
 entry. After probing is complete the resulting holes should be filled with 
 a patching conpound. 
 
 Marine Borers die when removed from the water for any period of time. A 
 vessel which has been out of the water for a few days and is essentially 
 dry will probably have no live borers. 
 
 Where borer attack is just starting it is possible to bum the holes clean 
 with a torch and then fill them with a suitable con^iound. If the attack is 
 extensive, however, the only method acceptable is to replace the aiffected wood. 
 
 The first principle in reducing the chance of borer attack is to keep the 
 worm away from the wood. This is accomplished by sheathing or by toxic paints. 
 If the protective coating is broken borers can enter. To prevent this sheath- 
 ing, where fitted, should be unbroken and in good condition and the bottom paint 
 should be free from scratches, nicks and scrapes before the vessel is again in 
 the water. 
 
 Worm shoes, rubbing strakes and similar members whose protective coatings 
 have been broken should be inspected carefully. If they have heavy borer 
 infestation they should be replaced. Care should be taken to see that the 
 infestation has not progressed from them to the main part of the hull structure. 
 Though wonn shoes are usually separated from the hull by cx^osote impregasted 
 felt or by copper sheathing, this separation is usually not 100/C effective. 
 
 G. Inspection of Fastenings 
 
 A boat is no better than its fastenings. Most hxQl fastenings are con- 
 cealed from view, being countersunk and covered; their inspection is difficult. 
 
 Planking fastenings which are loose, broken or wasted often result in 
 sprung butts or in planks which are loose or chatter when sounded with a haamer. 
 
 When fastenings are loose it does little permanent good to harden \:^ 
 those which exist. Additional fastenings, properly placed, are the preferred 
 repairs where there is siafficient room to obtain good holding power without 
 seriously weakening the planking. If there is not room, holes in the sub- 
 structure from the old fastenings should be properly plugged and new fastenings 
 of equivalent strength should be driven. Loose planking can also irestilt from 
 deteriorated frames and other sub-structure in which case refastening is useless 
 unless the structure is first made sound. 
 
 Particular attention should be given exposed hull fittings and through 
 
bolts. These should be sounded with a hammer and, if suspect, some shoxild be 
 pulled for inspection. It is advisable to pry up on exposed bolt heads with 
 a probe or screwdriver. Often the bolt will be completely wasted away in the 
 middle, at the faying surface of the joint, and will come out when pried up. 
 This is caused by moisture accumulation which, besides wasting the fastenings, 
 forms an excellent place for decay to start. 
 
 H. Inspection of Caulldng 
 
 Caulking is subject to deterioration. It is advisable to search the 
 seams in any doubtful areas and re-caulk. Caulking should be uniform and 
 well "horsed" home. This can be checked with an awl or -a knife. Care 
 shordd be taken that the caulking has not been driven clear through the S6am. 
 Over caulking is as bad as under caulking. 
 
 Extensive trouble with caulking is indicative of structural problems. 
 
 If a hull "works" excessively, the caulking will be squeezed out. In 
 such cases, the hull structure will have to be made sound before caulking 
 will hold. 
 
 In old hulls, where the seams have become enlarged from repeated re- 
 caulking, copper or lead strips may have been nailed over the seams to act 
 as caulking retainers. These are a temporary remedy and are an indication of 
 poor general condition of the vessel. It is advisable that such strips be 
 removed and the seams inspected for excessive width, poor caulking and decay. 
 In some cases, wide seams or broken plank edges can be repaired by the use 
 of thin graving pieces partially filling the wide seams. This procedure 
 requires excellent workmanship and should be pursued with caution. 
 
 I. Inspection of Fittings 
 
 The rudder and the propeller struts and fastenings should be examined 
 carefully. The steering arrangement should be inspected from the steering 
 wheel to the heel pintle. Wear in the carrier bearing and excessive 
 clearances elsewhere should be corrected. The tiller lines should be in 
 good condition with shackles moused and bolts cottered. 
 
 The shaft log glands should be in good condition and the deadwood 
 should be sound. This is often neglected and is a potential cause of leakage. 
 
 Propeller shaft cracks are sometimes found at the keyway. A careful ex- 
 amination here is essential. Magnetic particle testing is usually not 
 available in a small boatyard so the inspector must depend on visually 
 locating surface cracks. Dye penetrant testing is relatively inexpensive 
 and can be useful when available. 
 
 J. Hull Damage 
 
 Most hull damage can be seen readily. Cracked and broken members are 
 obvious faults. 
 
Likely locations for cracks or breaks are in areas of high stress or 
 where the structure undergoes a sudden change in shape. The turn of the 
 bilge is the prime location for breakes of this type. The harder the bilge 
 the more chance that damage has been done. 
 
 Wood hiolls are more prone to secondary damage remote from the site of 
 collision or grounding than are steel hul 1 s . Damage may consist of sprung 
 butts, pxilled fastenings, sprung or cracked frames and misalignment of the 
 structure. In inspecting any damaged wooden hull the entire vessel should 
 be checked. 
 
 K. Deficiencies 
 
 When deficiencies are encountered an evaluation must be made to de- 
 termine their extent and their effect on seaworthiness. The following 
 factors must be weighed in making this determination: 
 
 1« Is the defect progressive and, if so, how can its progress 
 be arrested? 
 
 2. How long will it be before the area in question is next inspected? 
 
 3, Is the work contemplated necessary to restore seaworthiness or 
 to prevent the vessel from becoming unseaworthy, or is it a 
 maintenance measure to prolong the life of the vessel? 
 
 Many deficiencies, particularly surface defects or scars caused by chafing, 
 freezing and other fonns of exterior deterioration are not as serioxis as 
 they may first appear. Do not be hasty in requiring the correction of minor 
 defects of this natixre in otherwise sound seasoned planking. 
 
 Specific requirements detailing the nature and extent of required re- 
 pairs should be written. However, with wooden vessels the general rule 
 "renew as original" while applicable, is not always practical nor necessarily 
 the best way to effect repairs. Most accepted methods of marine repair may 
 be \]sed as long as the vessel's strength is not reduced thereby. 
 
 Wood is a natural product; its quality cannot be controlled as closely 
 as with a man-made product such as steel. Consequently the inspector should 
 check the material to be used in the work. Special attention must be given 
 the type of wood proposed for each purpose and the defects in each piece. 
 
 Requirements for adequate repairs are: 
 
 (1) Use of good material conparable in properties to that replaced. 
 
 (2) Repairs extensive enough to assure that the hull is essentially 
 as strong as the existing original. 
 
(3) Details and fastenings at least equivalent in strength 
 and in quality to those replaced. 
 
 (U) Good workmanship. 
 
 III. REPAIRS 
 
 A. General 
 
 Wood boat construction varies widely from locality to locality 
 and boat to boat. All types of repairs which an inspector may en- 
 counter cannot be listed. Representative types and standards which 
 are given here are intended as a general guide to good practice and 
 as an aid in evaluating required repairs. They are not rules which 
 the responsible person must follow. Repair standards for wooden 
 hulls should be developed for the locality on the basis of local 
 conditions and practice. 
 
 B. Planking Repair and Notes on Joints 
 
 Fore and Aft Planking . When such planking is replaced, the frames 
 and other structure should be thoroughly inspected and placed in good 
 condition. Holes made by old fastenings should be properly plugged 
 to insure that new fastenings will hold. 
 
 "Flats", "dutchmen" or short lengths of planking are normally not 
 acceptable since they will not hold fastenings and are structurally un- 
 sound. 
 
 In boats with usual frame spacing the replacement plank should 
 extend at least six frame spaces and no portion of a plank shorter than 
 six frame spaces should be all owed to remain. 
 
 Where special conditions govern, this rule may be modified but, 
 as a lower limit, the replacement plank should be at least 5 feet long 
 an4 its butts should be spaced in accordance with the rule for butts in 
 this chapter. 
 
 Fastenings should be at least equal in size and number to those 
 of the rest of the planking. 
 
 When planking is placed on a boat, it should have the concave 
 side of the annual rings facing toward the ft-ame. This prevents 
 "cupping" as the moisture content of the wood changes. 
 
 It is sometimes necessary to shape the inboard side of a replace- 
 ment plank to fit tightly against the frames. The use of shims or pack- 
 ing pieces for this purpose should not ordinarily be allowed. 
 
 Diagonal Planking . The same principles apply to diagonal planking 
 but due to the relatively short lengths of the individual planks a 
 portion of a plank is seldom replaced. 
 
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Beca\ise the proper repair of double diagonal planking is expensive 
 and time consuming, short cuts involving the use of dutchmen and backing 
 blocks are sometimes attempted. These should not be permitted. Most 
 other planking systems follow the same basic principles of repair as 
 outlined here. Good workmanship and care are the major requirements for 
 proper r^air. 
 
 Plywood Construction 
 
 In general, the replacement of a portion of a panel of plywood is 
 not acceptable. However, in the case of a small damaged area between 
 ftames, a flush patch backed by a butt block may be used. 
 
 White lead or other suitable coripound on the edges of the opening is 
 an acceptable aid in sealing the patch. Calking should never be used and 
 shims and fillers as a substitute for good workmanship are not acceptable. 
 Care should be taken in allowing such a repair for small decayed areas 
 since plywood has relatively low decay resistance. Once decay has started it 
 travels rapidly in all directions. 
 
 Small siirface defects may be repaired using commercial fillers (epoxy 
 putty, etc.). In allowing this type of repair the wood must be decay free 
 and all damaged wood removed. Quick repairs of this type are satisfactory 
 where basic strength has not been affected. The danger lies in covering up 
 progressive defects such as decay which grow worse under the repair material. 
 
 Butt Joints in Planking . Planking butts should not terminate on frames 
 in normal construction. They should be located between frames on proper butt 
 blocks, though in light construction with narrow strakes they may sometimes be 
 found as glued scarf joints at the frames and in some construction with massive 
 framing they may be found butted on the frames. As a rule of thumb, butts in 
 adjacent planks should be at least three frame spaces apart. Those butts which 
 fall in the same frame bay should be separated by at least three solid strakes. 
 Th±a is not always possible, especially at the end of the vessel, but serves to 
 illustrate the principle of keeping butts separated as much as possible. Where 
 frame spacing is unusual the following rule may be used as a guide. 
 
 Butts in adjacent strakes should be no closer together than 5 feet. 
 If there is a solid strake between they should be no closer than 
 k feet. Butts should be shifted so that three or more do not 
 fall on a diagonal line. 
 
 To be effective a butt block must have adequate size. If the frame spacing 
 allows, its length should be at least 12 times the planking thickness. Its 
 thickness should be equal to the planking thickness and its width at least 1" 
 greater than the strake width. Prior to installation it is recommended that 
 the faying surface of block and strakes be coated with a wood preservative. 
 The top of the butt block should be chamfered to allow for water run off. 
 Avoid butting the block hard against the frames, if frame spacing permits, for 
 the same reason. 
 
 10 
 
5Cfi^RF WITH NIBS 
 
 HOOHBD SCARF W/TH N/B3 
 
 Hay LOCKED 5CARF W/7H N/33 
 
 KEY LOCKED H00KFD5CARF W/THNIB5 
 
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 COMMON FORm OF SCARFS 
 
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The fastenings of the strake to the butt block should be of equal 
 strength to that of original butts. The fastening size should be equal 
 or larger and no fewer number of fastenings should be allowed. 
 
 Plywood butt blocks may be used but it should be remembered that 
 though plywood has greater uniformity of strength in all directions, 
 it has somewhat less strength than the "along the grain" strength of 
 the basic wood from which it is made. 
 
 For new construction or for repairs "not in kind" the following 
 table lists the suggested number of fastenings for planking: 
 
 Suggested Minimum Nianber of Fastenings for Planking to Butts and Frames 
 
 Width of Plank Niimber of Fastenings in Number of Fastenings in Frame 
 (inches) Butt of Each plank 
 
 i'l Inch 1-li Inch 1^-2 Inch 
 Plank Plank Plank 
 Thickness Thickness Thickness 
 
 3-U 3 2 2 2 
 
 k-6 h 2* 2 2 
 
 6-7 $ 3 2 2 
 
 7-8 $ 3 3 2 
 
 8-10 6 3 3 3 
 
 ♦Planking at the side end of this range may require 3 fastenings. 
 
 Glued Scarf Joints . For a glued scarf joint the plain scarf without nibs 
 is the sir5)lest and strongest. Waterproof glue should be used and the slope 
 of the Joint should be 1/12 or flatter for maximum joint efficiency. 
 
 Scarf Slope TiTpical Joint Efficiency for a well 
 ( depth Aength) made glued joint without nibs 
 1/12 90% 
 
 lAO QS% 
 
 1/8 B0% 
 
 1/5 6$% 
 
 These efficiencies can be attained only with optimum gluing conditions 
 and excellent workmanship. 
 
 Mechanicany Fastened Scarfs . Mechanically fastened scarf joints are 
 most often nibbed, hooked, or keyed to provide extra axial restraint and to 
 aid watertightness. 
 
 12 
 
r 
 
 The stirface of the Joint should be smooth and flat to Insure good 
 fit and waterbie^tness. 
 
 T^e fastenings should be adequate in size and number and should be 
 arranged so as to prevent splitting the vood. 
 
 The slope of the joint, d-2n, should be lA2 or flatter. 
 
 Most mechanically fastened scarf joints are nibbed at the ends for a 
 depth of approximately 2S% of the depth of the member, giving a joint 
 length of at least 6 times the depth. 
 
 A scarf joint which is fastened by mechanical means alone cannot, 
 even under the best of conditions, produce a joint s^roaching a solid 
 member in strength. 
 
 Glued Butt Joints . Glued butt joints never give joint efficiencies 
 of over 20% and sho\ild not be permitted. 
 
 C. Framing Repair 
 
 Sister Frames . Damage to one or more scattered or Isolated frames 
 can be repaired by the use of sister frames though it is preferred that 
 the frame be replaced if practicable. Damage to more than two adjacent 
 frames should not be repaired with sister frames. 
 
 The preferred type of sister frame is one of equal or greater size 
 than the damaged one and as long as possible. This frame should be 
 fastened to the planking and other structure with fastenings at least 
 equal in size and number to those of the damaged member. In placing 
 the frame adequate wood preseinrative on all faying sux'faces is rec- 
 ommended . 
 
 Long sister frames, well tied in to the main structure of tte vessel 
 should not nonnally butt against damaged frames though this is acceptable 
 where it forms the best method of tying in the new frame. If the frames 
 abutt, a good sealer is required to excltide moisture from between the pieces. 
 
 Where structural or machinery interference or other reasons prevent 
 the fitting of a long sister frame, well tied into the otho: structure, 
 a shorter "partial sister" may be fitted as a ten^jorary repair. This 
 should extend as far as is practicable on both sides of the damage and 
 should be securely fastened to the damaged frame by through bolting or 
 equivalent means as well as to the planking and other structure. Pro- 
 visions should be made to exclxide moisture from between the pieces. 
 
 A good wood preservative is recommended for use on all faying surfaces. 
 Assure that precautions are taken that standing water cannot accumulate at 
 the top of the partial frame and caxise decay. A sister frame should not be 
 used as a repair fcr decayed frames. The decayed wood will eventually "seed" 
 
 13 
 
the sound wood with decay spores in spite of any attempts to prevent it by 
 the use of wood preservatives or to isolate the new wood with sealing compounds. 
 When extensive decay is present in a frame the only permanent repair is to 
 replace it and any adjacent wood affected. 
 
 Decayed Frame Heads . Heads of frames under the covering boards often 
 become decayed. With sawn flrames, this can be corrected by replacing the 
 upper futtock. If the futtock is long or the frame is in one piece, it can 
 often be cropped off well below the rot (at least 2 feet is a good rule) 
 and a piece spliced in \ising a glued and screwed scarf joint of proper dimensions. 
 As an alternate measiire a lap joint of sufficient length may replace the scarf. 
 Repairs to more than two adjacent damaged frame heads should not be made by 
 short cropping but should be made by renewing the frames or replacing the damaged 
 sectiOTis by scarfing and then sistering the frame. 
 
 D. Use of Fiberglass Reinforced Plastic . Glassing an unsound structure as 
 a way of restoring strength is a temporary repair. This is especially true 
 of glassing planking or other areas which tend to work or "came and go". 
 The laminate has little flexibility along its length and breadth and tends 
 to develop "tension cracks" "which destroy watertightness and strength. 
 
 Before allowing any wooden structure to be repaired using reinforced 
 resin, an evaluation should be made considering the following items in 
 addition to those noted before. 
 
 (1) In the hull, even a hairline crack can allow undetected 
 entry of marine borers. 
 
 (2) With old structure which has been painted or preserved a 
 good bond is very difficult to attain. 
 
 (3) Any rot present may continue to grow worse under the glass 
 if the proper conditions of moisture and heat develop. 
 
 (U) It is difficult to acquire enough strength from a reinforced 
 
 resin coating to make up that lost from the unsound substructure. 
 
 (5) It is difficult to check the soundness of the substructure 
 once the glass has been applied. 
 
 Poll Sheathing of an existing wooden hull with fiberglass reinforced 
 plastic as a method of restoring strength and watertigjitness to a deteriorated 
 vessel is not normally acceptable. 
 
 IV. MATERIALS 
 A. Wood 
 
 THe best single source of information available in the broad field 
 of wood technology is "The Wood Handbook" (Handbook No. 72) developed 
 
 lU 
 
by the Forest Products Laboratory of the Department of Agriciilture . This book 
 can be obtained from the Superintendent of Documents, Washington 25, D. C, 
 It is highly reconmended as a thoroughly practical work which should be 
 part of the technical library of every inspection office and every wood boat 
 building or repair yard. 
 
 Shipbuilding Wood . Douglas fir, southern yellow pine (long leaf), and 
 white oak furnish over one half of the wood used for boat and shipbuilding. 
 Choice of various species depends upon their properties, availability and cost. 
 
 Where requirements call for strength, moderate to good decay resistance 
 and ability to hold fastenings well (frames, keels, stems, etc.), the follow- 
 ing wood are most commonly used: 
 
 Douglas fir 
 
 Southern yellow pine (long leaf) 
 
 Teak 
 
 Western Larch 
 
 White Oak 
 
 Where light wood which is easy to work and is warp and decay resistant 
 is required (planking, etc.) the following woods are most commonly used: 
 
 Alaska cedar Red wood 
 
 Cypress Tangile (Philippine 
 
 Mahogany hardwood) 
 
 Cedar (Port Orford, Northern 
 
 White, arxi Western Red) 
 
 Where light, easily worked and strong woods of moderate to low decay 
 resistance are required, the following woods have found favor: 
 
 Sitka Spruce 
 Western hemlock 
 White pine 
 Tellow Poplar 
 
 There are matqr other varieties suitable for boat use. These are listed 
 together with their properties in the Wood Handbook and in Volume 1 of 
 Bureau of Ships Publication "Wood - A Manual for its Use As A Shipbuilding 
 Material". 
 
 Benditig Woods . Unseasoned white oak is the choice bending wood. It 
 bends readily and is high in decay resistance. Red oak, hickory, rock 
 elm, white ash, beech, birch, and hard maple, also bend readily but do not 
 have the decay resistance of white oak. White oak and its best substitute, 
 rock elin, are expensive and hard to obtain, but do the best Job. 
 
 1$ 
 
A- Vire nail, (not commonly 
 used in boat construction) 
 
 B- Spiral grooved nail. 
 
 C- DriTt bolt. 
 
 D- Boat nail with grooved shank. 
 
 E- Chisel point boat nail. 
 
 F- Square cut boat nail with 
 rivet burr and cut washer. 
 
 G- Boat spike with chisel point. 
 
 16 
 
Wood Defects . Wood, being a natural material, is not uniform in 
 quality and is subject to defects. Some of these affect only the appearance 
 of the wood. Others affect the strength of the wood and are of inportance. 
 
 The chapter of "The Wood Handbook" on Stress Grades and Worlcing Stresses 
 discussed defects of interest to persons concerned. Among the most isqsortant 
 of these are - 
 
 Knots, Shakes, Checks, Splits and Pitch Pockets. 
 
 Plywood . Plywood is a built up board of laminated veneers in which 
 the grain of each "ply" is perpendicular to the ones adjacent to it. 
 Its chief advantages lie in more nearly equal strength properties along 
 the length and width of the panel, resistance to change in dimensions with 
 moisture content and resistance to splitting. Major disadvantages are low 
 decay resistance and the difficulty of painting it properly. 
 
 Plywood is excellent where strength is needed in more than one direction 
 and where the relatively large size of the panels available can be utilized. 
 It is no stronger than the wood from which it is made and is not a cure-all 
 for wood structural problems. 
 
 Plywood is made from several types of wood and in many diffei^nt types 
 and grades. In general, "Marine-Exrberior" type of fir plywood or its equivalent, 
 technical or Type 1 hardwoods are the only plywoods acceptable for use as hull 
 planking. These plywoods are identical with ordinary "Erterior" type in that 
 they are bonded with waterproof glue by a process using heat and pressure. 
 Their advantage lies in the fact that the interior plies contain few gaps and 
 thojs its strength, ability to hold fastenings and resistance to decay are 
 much higher than "Extertor". "Marine" plywood is more expensive than "Erterior" 
 but provides additional safety and durability. 
 
 Fir plywood is graded according to the appearance of the exterior veneers. 
 These grades run from grade "N" intended for natural finish and grade "A", 
 s\iitable for painting, down through grade "D", the poorest quality. Each 
 side is graded. For example, a panel may be graded "Marine Exterior A-B" 
 where "Marine Erterior" refers to the type of bonding used and the allowable 
 defects in the inner plies, while "A-B" refers to the appearance of the two 
 sides of the panel. 
 
 Marine plywood is usually available only in c^ppearance grades B-B and 
 better. The strength of the wood is indirectly reflected in the grading since 
 the poorer grades have openings, splits, pitch pockqts and other defects 
 which adversely affect strength and decay resistance. 
 
 All plywood is marked with its classification. This classification naj 
 appear on the panel back, on its edge or both. 
 
 B. Mechanical Fastenings 
 
 Mechanical fastenings should be of material suitable for the service 
 intended. Ferrous fastenings should be hot-dipped galvanized. Amxmg the 
 
 17 
 
usual noa«ferrous tyx^es brass is not acceptable where it will be exposed to 
 salt water attack. 
 
 Caution should be used in selecting fastening material because of the 
 problem of galvanic action which can arise if dissimilar metals are used 
 close to one another. A bronze washer used with a steel bolt will result 
 in the eating away of the steel. 
 
 GALVANIC SEHEES IN SEA WATER 
 
 PROTECTED EMD (CATHODIC OR ICST NOBLE) 
 
 Monel 
 
 Copper 
 
 Red Brass 
 
 AluBiinuin Brass 
 
 Yell ow Brass - Silicon Bronze 
 
 Nickel - Inconel 
 
 Naval Brass 
 
 tbmtz Metal - Manganese Bronze 
 
 Lead - Tin 
 
 Stainless Steel (Reference should be made to the specifications for 
 stainless steels being considered since they vary 
 widely in their properties) 
 
 50-5G Lead-Tin Solder 
 
 13/^ Cr Stainless Steel 
 
 Cast Iron 
 
 MLld Steel - Wrought Iron 
 
 Aluminum - Cadmium 
 
 Galvanized Steel 
 
 Zinc 
 
 Magnesium 
 
 CORRODED HO (ANODIC OR LEAST NOBLE) 
 
 The number, size and spacing of fastenings should be equivalent to or 
 better than those replaced. For new construction and for repairs "not in 
 kind" a general guide for good practice is the "National Design Specifications 
 for Stress Grade Lumber and its Fastenings", a publication of the National 
 Lumber Manufacturers Association. In applying the standards found therein, 
 consideration should be given to the severe conditions of marine service. 
 
 A general guide for use of the various types of fastenings follows; 
 
 Bolts . Bolt holes should be of such diameter as to provide an easy fit 
 without excessive clearance. Tight fit requiring forcible driving of the 
 bolt is not recommended. 
 
 Washers, A washer not less than a standard cut washer or, in lieu thereof, 
 a metal plate or strap should be inserted between the bolt head and the woai 
 and between the wood and the nut. 
 
 IB 
 
/v\ 
 
 B. 
 
 ■<.SUANI^'^ 
 
 K 
 
 P. 
 
 D 
 
 CORE' 
 
 MOT DIAMETER 
 
 TYPES or WOO0 SCREWS 
 A . FL ATHEAP, 3. MUNO-HEkO , C. OVA Is HEAD 
 
 A SHOWS A 5CREV/ PROPER Ly XNSERTEO AND COUNTERSUNK. 
 B AND C SHOW INCORRECTLS (NSERTEO SCREV/S. 
 O SHOWS PRINCIPAL BARTS OF A WOOD SCREW. 
 
 19 
 
SECnCNS THROUGH SCREW HOLES 
 
 A- Proper lead hole size. 
 B- Lead hole too large. Screw drove easll7 
 bat had poor holding power. 
 
 20 
 
Stopwater . A stiitable vicklng or stopwater shcmld be fitted in way of 
 the faying surface of the Joint at each throu^ bolt subject to moisture. 
 
 Placement of Bolts in Joint . The center to center distance between bolts 
 in a row shoxild be not less than four times the bolt diameter. 
 
 The spacirg between rows of bolts should be $ times the bolt diameter 
 for a bolt whose length from the bottom of the head to the inner side of the 
 nut when tightened is 6 tijnes the bolt diameto' or longer. For short bolts, 
 this distance may be decreased but in no case should be less than 3 times 
 the bolt diameter. 
 
 The "end distance" from the end of a bolted timber to the center of the 
 bolt hole nearest the end should be at least 7 tljtnes the bolt diameter for 
 softwoods and at least 5 times the bolt diameter for hardwoods. 
 
 The "edge distance" from the edge of the member to the center of the 
 nearest bolt hole should be at least 1^ times the bolt diameter . For bolts 
 whose length is over six times their diameter use one half the distance between 
 bolt rows and in no case below 1^ times the bolt diameter. 
 
 For perpendicTilar to the grain loadings (joints at right angles), the 
 edge distance toward which the load acts, should be at least U times the 
 bolt diameter. 
 
 Bolting Groups . In general, all groups of bolts should be symmetrical 
 in the members. The individual fastenings should be offset slightly as 
 necessary to avoid placing more than one on the same grain. 
 
 Screwed Fastenings . 
 
 Lead HolesT Lead holes for wood screws should be about 90/^ of the root 
 diameter of the screw for hardwoods and about 70^ of the root diameter for 
 softwoods. For large screws and for hardwoods, a shank hole of a diameter 
 equal to the shank of the screw and of a depth equal to the shank may be 
 used to facilitate driving. Lag screws should always have a shank hole. 
 
 The lead hole for the threaded portion of a lag screw should have a 
 diameter of 6$-6$% of the shank diameter in oak and 60-75% in douglas fir 
 and southern pine with a length equal to the length of the threaded portion. 
 Denser woods require larger lead holes and the less dense require smaller 
 holes. For long screws or for screws of large diameter, lead holes slightly 
 larger than those recommended here should be used. The threaded portion of 
 the screw should be inserted by turning and not by driving with a hammer. 
 
 Lubricants . Suitable lubricants should be tised on screws, expecially 
 in dense wood, to make insertion easier and prevent damage to the scz^ew. 
 
 Depth . Penetrati on of the threaded portion for at least a distance of 
 7 screw diameters for hardwoods and 10-12 tines in softwoods is required for 
 maximum holding power. 
 
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Loading . If possible, screws should be placed so that they are loaded 
 across the screw and not in withdrawal. 
 
 The spacing, end distance and edge distances for wood screws should be 
 such as to prevent splitting the wood. Lag screws should follow the rtdes 
 for bolts. 
 
 Nails and Spikes . Cut nails have relatively poor holding power In 
 joints which are subject to moisture changes. Their use in marine applications 
 should be avoided. Barbed nails are better suited for marine service. 
 
 Lead Holes , Lead holes for nailed joints may be 3/k of the diameter 
 of the nail without caxising loss of strength. 
 
 I^ypes of Load . If possible, nalla should be loaded across the nail and 
 not in the direction of withdrawal. This is especially important in end grain. 
 
 Spacing of Nails . The end and edge distances and spacing of the nails 
 should be such as to prevent splitting of the wood. 
 
 Boat Spikes and Drift Bolts 
 
 Lead Holes . Lead holes for boat spikes should be the size of the short 
 dimension of the spike and should extend approximately 7S% of the spike depth. 
 The lead holes for drift bolts should be slightly less than the bolt diameter 
 and of a depth equal to the bolt length. 
 
 Type of Load . Where possible, spikes and drift bolts should not be loaded 
 in withdrawal. This is especially important in end grain. 
 
 Insertion . A clinch ring or washer may be used under the head to prevent 
 crushing of the wood. Spikes should be driven with the edge of the chisel 
 point across the grain to avoid splitting the wood. 
 
 Spacing of Spikes and Drift Bolts . The end distance, edge distance ani 
 spacing of the spikes should be such as to avoid splitting the wood. 
 
 C. Glues and Gluing 
 
 Modem glues of the resorcinol and phenol -res orclnol resin types are 
 the most satisfactory for severe service use such as for marine repair. Other 
 glues have lower resistance to moisture and should be avoided where this is 
 an important factor. 
 
 Not all wood are easily glued. Wet wood (aboro about 15^ moisture content) 
 is difficult to glue as is very dry wood. Normal seasoned wood of most species 
 can be glued. Strong glued joints are possible only using the side grain of 
 wood. These joints can be very nearly as strong as the wood itself. It is 
 impossible to join end grain with glue and get joints which are even 20^ as 
 strong as the wood. A scarf or some other form of joint which gives a surface 
 approaching side grain condition must be used where end connection is desired. 
 
 23 
 
The glue manTifactttrer's instructions must be followed. Chiring ten^jerature 
 and surface condition are iji5)ortant. The temperature must be about 70 °F or 
 higher for a full cure of resorcinol resin glue and the surface should be 
 smooth. In the past, surfaces have been intentionally roughened in the mistaken 
 belief that slightly rough surfaces glue better. This is not true . Wato: - 
 proof glues are poor fillers. Thus the surfaces should be as smooth as possible. 
 
 D. Wood Preservatives 
 
 The use of wood preservatives is not required. However, their use in 
 wood under severe service conditions will pay for itself many times in de- 
 creased decay and borer attack and thus decreased repair and replacement costs. 
 Their proper use should be encotiraged since it increases the chance of the 
 vessel remaining sound until her next inspection and thus contributes to main- 
 taining a reasonable standard of safety. 
 
 Wood preservatives used for protection against decay fungi and marine 
 borers either kill the organism or prevent it from growing. For marine use 
 the preservative must offer no toxic hazard to the crew, must be free from 
 objectionable odors and must be able to remain in the wood and do its work 
 in the presence of moisture. No known wood preservative is ideal for marine 
 use but certain ones have proved effective for specific applications. 
 
 There are two general classes of wood preservatives, oil soluble and 
 water soluble. Both have been used in the marine industry. 
 
 Oil Soluble Preservatives 
 
 Coal Tar Creosote . One of the most used of the oil soluble preserva- 
 tives is coal tar creosote. This preservative is highly toxic to wood attacking 
 organisms, is relatively insoluble in water and is easy to apply. It has some 
 disadvantages, however, which limit its use in the marine field. It has a 
 distinctive unpleasant odor, is somewhat of a fire hazard when freshly applied 
 and causes skin irritation in sane individuals. Its main disadvantage is that 
 it is almost impossible to make paint or other coatings adhere to it. 
 
 Copper Naphthanate Solutions . Copper napthanate solutions form one of 
 the most used groups of marine wood preservatives. A three percent solution, 
 equivalent to one half of one percent copper by weight, provides good pro- 
 tection against decay when properly applied. The protection afforded against 
 marine borers is slight. Wood treated with copper naphthanate is a distinctive 
 green color. Much of the "treated wood" which can be purchased is preserved 
 with copper naphthanate. The paint ab ility, . glue bonding ability, and structural 
 stability of the wood is only slightly affected by the copper salts. These 
 properties will vary, however, depending iqjon the oil used as a solvent. 
 
 Pentachlorophenol Solutions . "Penta" solutions have proven satisfactory 
 for marine use . Field tests have sha«m that a ^% solution offers adequate 
 protection against decay when proper application techniques are used. Little 
 if any protection against marine borers is provided. 
 
 Pentachlorophenol does not give wood any distinctive color. In itself, 
 it affects the characters tics of wood very little. The final effect of the 
 
 2h 
 
preservation treatment on physical characteristics depends \xpon the petroleum 
 solvent used. 
 
 Water Repellent Preservatives . Copper naphthanate and "pent a" are often 
 ccnbined with water repellents, ^ese repellents aid in stabilizing the 
 moisture content of the treated wood. This is a material aid in reducing the 
 chance that decay growth conditions will occur. In order to be effective 
 these solutions should contain no less than S% pentachlorophenol or 2% copper 
 in the form of copper naphthanate. 
 
 Solvents . Almost any petroleum product from mineral spirit to used 
 engine oil can be used as a vehicle for the preservative depending upon local 
 conditions. In general, the heavier high viscosity residium types offer the 
 best retention. The choice of solvent is usually a ccn?)roniise of effectiveness, 
 paintability and initial cost. 
 
 Water Preservatives . Waterbome preservatives include zinc chloride, 
 tanalith, copper arsenite, chromated zinc arsenate and many others. Their 
 major applications are those in which the leeching out of the preservative 
 by moisture is not a problem. In general, these preservatives have not proven 
 satisfactory for severe marine service. Some preserved wood obtained for re- 
 pair use may have been pressure treated with one of these preservatives. It 
 can give satisfactory service if care is taken to use it in a location where 
 it is protected from the action of rain and sea water. 
 
 Methods of Treatment 
 
 Pressure Treatment . In the canmercial treating of wood a method utilizing 
 high pressure is often used. This method reqiiires expensive equipment and is 
 seldom seen in a boat yard. Nonpressure treatments available to the boat yard 
 are brushing, cold soaking and various types of "hot and cold" bath processes. 
 
 Brush Treatment . The siii5)lest way of applying a preservative solution 
 is to brush it on. Every crack and check must be flooded with preservative if 
 the treatment is to be effective. Small pieces such as butt blocks can be 
 dipped into the preservative. Solutions of pentachlorophenol or copper naphthanate, 
 available coramercially, have proved effective when used in this way. 
 
 "Penta" stock solutions are available in what is known as 1:5 and 1:10 
 strengths, (i.e. the solution must be diluted one part of solution to five or 
 ten parts of solvent to achieve a "normal" wood preserving solution.) These 
 stock solutions are used without dilution for preserving cracks, holes resulting 
 from old fastenings, for coating Joints and hard to get spots, etc. Care must 
 be exercised since wood preservatives are toxic. When using the brush-on method 
 the entire sturface must be thoroughly coated. 
 
 Soaking . Cold soaking in copper naphthanate or "penta" solutions for 
 periods of up to U8 hours provides much better retention of the preservative 
 than does a brushing. An even better method consists of heating the wood in a 
 hot preseiTvative bath and then transferring it to a cold bath of preservative. 
 The heating causes the air entrapped in the wood to expand. The sudden cooling 
 sets xxp a vacuum >diicb aids preservative penetration. 
 
 25 
 
•Rie effectiveness of a preserving treatment depends on the amount of 
 preservative which is retained in the wood. Tliis is often difficult to 
 determine. Requirements in Federal Specification TT-W-571 for recommended 
 net retentions of oil borne preservatives are shown in the following table. 
 This amount will provide good protection and even lesser amounts will still 
 offer a considerable measure of protection. 
 
 Recommended Net Retentions of Preservative 
 
 Service 
 
 Product 
 Pentachloro- 
 phenol ^% ' 
 Petroletaa Oil 
 
 Copper Naphthanate 
 (0.75^ cer metal) 
 in petroleum 
 oil 
 
 Coal Tar Creosote 
 
 Lumber and 
 Structural 
 Timber 
 
 In Contact 
 with Ground 
 or wata" 
 
 Not in Con- 
 tact with 
 Ground or 
 Water 
 
 m - 20 Ib/cu ft 10 Ib/cu ft 
 
 6 Ib/cu ft 
 
 6 Ib/cu ft 
 
 10 Ib/cu ft 
 
 6 Ib/cu ft 
 
 Treating Isolated Decay 
 
 A method which can arrest the progress of incipient decay, 
 at least tea^jorarily, is as follows: 
 
 The affected area is scraped clear of all decayed material 
 and for some distance into apparently clear sound wood. A 
 strong preservative solution, for exasrtple 1:10 pentachloro- 
 phenol stock solution, is applied freely. This is allowed 
 to soak in and dry. Repeated applications are made until 
 the wood refused to take any more preservative. Often a 
 small "cofferdam" can be made to retain a pool of preservative 
 over the area. To be effective the preservative must sink 
 in and sterilize the wood for a considerable distance since 
 decay sends out spores ahead of the damaged area. 
 
 After the treatment is completed the cavity made by the scraping may be 
 left unfilled but it should be properly painted. Pilling it will sisaply hide 
 any additional rot still working. 
 
 This method is a temporary repair only. It usually will slow decay attacl 
 but will seldom eliminate all traces of decay. 
 
 26 
 
"Salting" and Other Bilge Water Treatment 
 
 Decay will grow in a boat only where fresh water is present. This 
 may be in the form of condensation or may come from rain, fresh water 
 drains, or other soxirces. Salt water will not support fungus growth. 
 The fungus usually does not die but its attack slows or stops. 
 
 In some areas of the country, it has been the practice 
 to "salt" the bilges with rock salt. There are two dis- 
 advantages to this practice. 
 
 1. The salt dissolves readily and must be replaced often. 
 A large part of it goes over the side when the bilges 
 are pumped. 
 
 2. Strong salt solutions are hard on fastenings and metal 
 parts. ITie wood stays sotind but the life of the metal 
 parts is reduced. 
 
 For these reasons, "salting" is of doubtful value. 
 
 Extensive tests have been run-^ on various chemicals to replace rock 
 salt. The ones that offer the best promise are pentachlorophenol or 
 orthophenylphenol. These chemicals, normally thought of as insoluble 
 in water can be applied in the following manner: 
 
 Nylon "bean bags" containing crystalline "penta" are made and 
 distributed through the bilge. A number of very small ones 
 is sxqserior to a few larger ones. Care must be taken in 
 handling the "penta" since, like all good fungicides, it is toxic. 
 
 The "penta" goes into solution in the bilge water. This is 
 very slight (about 20 parts per million) so that in spite of 
 frequent pumping, very little penta is used up. The slight 
 amount of penta dissolved makes the water fungistatic, that is 
 to say, it will not s\ipport fungus growth. As long as the bean 
 bags remain a considerable amount of decay protection is af- 
 forded. The solution is harmless to fastenings and metal parts 
 and, with normal precaution, is not hazardous to handle. Since 
 very little penta is used the cost of the treatment is surprisingly 
 low. 
 
 In his conclusion. Dr. Scheffer states "Judging from these restilts, bilge 
 water saturated with orthophenylphenol or with pentachlorophenol might be ex- 
 pected to preserve any wood that is wetted by it frequently and exclusively". 
 
 Caulking . The art of caulking is an ancient one which requires ex- 
 perience and a certain "touch". A good caulker makes his work look easy 
 but it is a skill which takes much experience to develop. 
 
 ^ Scheffer, T. G., Treatment of Bilge Water to Control Decay in the Bilge 
 Area of Wooden Boats^ Journal of the Forest Products Research Society, 
 Madison, Wisconsin: September, 1959. 
 
 27 
 
Boats are caialked with caulking cotton, oakum is used for large vessels. 
 Caulking cotton comes in bundles which can be shredded out to proper size for 
 the seam. Plumber's caulking stuff which is short stranded should never be 
 used. The caulking stuff is driven into the seam with a caulking iron forming 
 loops with each drive of the iron. These loops should touch each other when 
 in place. After the caulking is in place it is redriven or horsed home with 
 the iron leaving room for filling the seam. Various irons of different shapes 
 are used depending upon the location and condition of the seam. 
 
 Caulking should never be driven through the seam but should be in a "rope" 
 about half way through. Caulking may be driven dry but it will not last as 
 long as that which has been lubricated with linseed oil or other suitable 
 lubricant. After caulking the seam may be filled with seam compound, white 
 lead putty or other material as the circumstances require. Old caulking should 
 be "reefed out" prior to putting in new. If the seams are narrow they are 
 often opened up with a "dump iron" or a reaming iron to facilitate caulking. 
 
 In older vessels the seams may have been widened by repeated caiilking over 
 the years. This condition, coupled with unsound frames and structure, may 
 make it in^sossible to keep caulking in the seams. Some owners may have fastened 
 strips of lead or copper over the seams in an effort to correct the trouble. 
 This "stop gap" method does little to maintain watertightness and may cover 
 up deterioration. The preferred method of repair is to strengthen the structure 
 and the fastenings prior to recaulking. If this does not stop the trouble 
 portions of the boat may require replanking. 
 
 V. DETERIORATION 
 A. Decay 
 Wood has proved itself to be good for long service under proper condi- 
 tions. One of the greatest enemies of wood is decay or "rot". Much of 
 this rot in boats is preventable if care is used in construction, main- 
 tenance and repair. 
 
 Decay in wood is caused by various fungi which are living organisms 
 whose growth depends upon suitable tenperature (^O'' to 90°F), suitable 
 food (wood) and moisture. Wood that is dry will not rot nor will water- 
 logged wood. In order to provide a condition suitable for fungus growth 
 wood must be moist (from 20 to 30^ moisture content). This condition is 
 promoted by poor ventilation. A well designed vessel should have adequate ventila- 
 tion of its enclosed spaces. Bilges, cabins etc., of vessels in service should 
 be opened periodically to allow a change of air. Good ventilation of interior 
 structure in wooden hulls is one of the most effective measures in the pre- 
 vention of decay. 
 
 Not all wood offers the same natural resistance to decay. Most wood species 
 have moderate to low natural decay resistance. In general, heartwood is much 
 more decay resistant than sapwood of the same species. 
 
 The fresh surface of decay is usually fluffy or cottony as contrasted to 
 the powdery growth of mold. The various rot fungi act in slightly different 
 ways but is left unchecked all can destrpy the wood in short order. 
 
 26 
 
It is relatively easy to recognize advanced decay. The wood is dis- 
 colored, softened and brittle and may show cracks and collapsed areas. Early 
 decay is more difficult to recognize. It may appear as a discoloration 
 in streaks along the grain of the wood. No known test available to the in- 
 spector can be substituted for experience in spotting early decay. The mere 
 presence of a stain does not indicate decay. Wood is prone to pick vip stain 
 and coloration from blood, fish, bird droppings and various other sources. 
 Probing with an ice pick is sometimes a help in finding "soft spots" in areas 
 in which visual inspection and sounding with a hammer have aroused suspicion 
 as to the soundness of the wood. Turning up a splinter with a knife blade 
 may also help. Sound wood tends to produce long clean splinters while wood 
 with early decay, having lost much of its strength, will break off abruptly. 
 
 While the final test for rot is to collect sait^jles ftrom the interior 
 
 of the wood by probing, as noted above, or by boring with a drill these 
 
 procedures should be used with caution. Excessive drilling and probing 
 can weaken otherwise sound structxire . 
 
 Fungi are living plants that can and do travel from an infected area 
 to a sound one. It is useless to place sound wood against rotten and expect 
 the sound wood to sxirvive. 
 
 Once decay is well started in a piece it is difficoalt and most often 
 ijrcpossible to stop its progress. In early decay the use of wood preservatives 
 can be of aid in controlling the attack. Used properly in new construction 
 or in repair they can prevent it. 
 
 B. Marine Borers 
 
 riarine borers are present to a varying degree in almost all the salt 
 and brackish waters of the world. They attack practically every species of 
 wood used in boat construction. There is no sure method of protection from 
 their attack. The two principal methods are to physically keep the worm 
 awav from the wood (sheathing) and to make the wood unattractive to the worm 
 (toxic substances and coatings). The main types of marine borers are listed 
 in the following paragraphs. 
 
 Shipworms . These pests are actually mollxosks and not worms. There are 
 several species of Teredo and Bankia in this groxrp. Thou^ they vary in 
 detail, their attack upon wood follows the same pattern. 
 
 Ihey start their lives as tiny free swimmers, l^on finding a suitable 
 hone, even a tiny crack in a sheathed bottom, they attach themselves and 
 quickly change form. As a pair of cutting shells develop on their heads 
 they bury themselves in the wood and feed iq)on it. Their tails or "syphons" 
 always remain at the entrance to their burrow but, as the worms grow, their 
 heads eat channels in the wood. The entrance holes always remain small and 
 hardly noticeable but the interior of the wood becomes honeycombed. When 
 they are not crowded some species of shipworm can grow to lengths exceeding 
 four feet. 
 
 Martesia . These are wood boring molltisks which resemble small clams 
 like the shipworm, they enter the wood when they are small and do their damage 
 within. They do not grow to the length of shipworms but, nevertheless, they 
 can do considerable damage. Their main area is in the Gulf of Mexico. 
 
 29 
 
Lljtinoria and Sphaeroma . These are small creatures which attack the sur- 
 face of the wood. When large numbers of them are present the surface can be 
 eaten away to such an extent that the remaining sound wood between their 
 burrows can be removed by the action of moving water. This erosion causes 
 the pests to burrow deeper. Their attack, though serious, is much more 
 easily detected than that of shipworms. 
 
 Protecting Wood Hulls from Marine Borers . Coal tar creosote is the 
 meet effective chemical for use against marine borers. However, it adds 
 considerably to hull weight, has an objectionable odor and does not allow 
 the effective application of antifouling paints. Wood which has been treated 
 with certain other wood preservatives has some resistance to borer attack 
 while an unbroken layer of copper bottom paint or of sheathing prevents the 
 entry of the borer. 
 
 Any break in the protective coating is an open invitation to boi^r 
 infestation. It is of first in5)ortance that the bottom coating of a boat 
 be continuous. Tool marks, scrapes, nicks, etc., should be properly preserved 
 and painted prior to refloating the vessel. 
 
 The same principle applies to bottom sheathing whether copper or fiber- 
 glass reinforced resin. A small break can admit enough shipworms to honeycomb 
 the structure of the ship while the sheathing makes their detection difficult. 
 In order to protect the hull coatings, some boats are fitted with worm shoes 
 attached to the bottom of the keel and separated from it by creosote soaked 
 felt or copper sheathing. These shoes are designed to take the scraping of 
 any grounding, to have their protective coating broken rather than that of the 
 hull and thus protect it from worm attack. All such shoes, rubbing strakes, 
 etc., should be viewed with suspicion since it is in^sossible to assure 100^ 
 separation from the hull and since an infected worm shoe is a source of "free 
 swimmers" which can move to any break in the protective coating of the hull. 
 
 Metal shoes and rubbing pieces are sometimes fitted for the same purpose. 
 Of course these never become worm infested but they must be carefully fitted 
 and bedded to prevent borers from working their way underneath the shoe around 
 the edges and thus into the main structure. 
 
 30 
 
VI. SKETCHES OF WDODIH OONSTRDCTIQN USD A SHORT GLOSSART Of 
 
 WOOD AND WOODHI VESSEI5 
 
 A. SKETCHES 
 
 Plate l-fyamlng for Wooden Boats (Sections) 
 Plate 2-Sectlon8 laical of Heavy Constractlon 
 Plate 3 -laical Heavy Stem Conatraction 
 Plate li-T^ical Heavy Stem Construction 
 Plate 5-Stopwaters in a Stem Piece 
 
 31 
 
Ty/='/CAL rPAM/h/G- cs£cr/o/vsj 
 
 amen n.*mam 
 OUTEH hamkms 
 
 CHOCK MIL 
 CASING 
 HALF OVAL 
 aUAPO ItA/L 
 CLAMP 
 
 8 BRNT FRAME, UPSTRAXE 
 
 A BENT RUMS, DOUBLE HiANKED 
 
 -PLYWOOO CASM TOR 
 - CANVAS 
 
 swe fi/umam 
 
 -srmmeeif clcat^^^ rT 
 
 — CMtarr 
 
 -STimitn,,.^^'-''''^ yj^ 
 
 r SP^AY MIL 
 
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 -CMHte 
 
 ^ 'C ^^*irr£w 
 
 
 ^torrom nA$m 
 
 
 aoTTom PLAmam 
 
 
 PLAre 
 
 HEAOeR 
 
 cABiM sioe 
 
 oecK coveiUNG compound 
 
 OeCK, PLYWOOO 
 
 roe RAIL 
 
 PUa RAIL 
 SNEER PLANK 
 ■SNEER CLAHtP 
 
 SOE FRAME 
 
 SIOE PLANKING 
 
 aUSSET 
 CNINE 
 OUTER CNINE 
 
 'FLAT SEAM 
 -BOTTOM PtANKMt 
 -tOTTOm FRAME 
 -FILLER RLOCK 
 -PLYWOOO FLOOR WER 
 ' ARROM 
 -KEEL 
 
 ^ aiMH IRIMB, DOUBLE fLAJOm), FUVOQD 
 
 D aiHH nUMB, DOUBLE FLANKED 
 
 32 
 
i 
 
 i 
 
 to 
 
 
 k 
 
 33 
 
TYPICAL HBAVy ST^M CONSTRUCT/ O/V 
 
 3'^ 
 
i 
 
 35 
 
STORWATER 
 
 RLAMKIMS 
 
 SECTION A- A 
 
 LOCATIONS OF STOPMTERS IN A STEI>I PIECE 
 
 56 
 
VI. B. C lo t sary 
 
 Ashcroft - Construction - Double diagonal planking system with the 
 planks of both skins raking in the same direction. 
 
 Backbone - The ''spine" of the hull from which the frames radiate. 
 
 Back rabbet - Innermost angle or line of rabbet in which the garboard 
 strake is set in the keel; any rabbet cut to receive planking at 
 other than a right angle. 
 
 Ballast - Added weight either within or external to the hull added to 
 
 improve the stability of a vessel or bring it down to its designed 
 lines. 
 
 Bastard sawn - Hardwood lumber in which the annual rings make angles 
 of 30* to 60" with the surface of the piece. 
 
 Batten - Ji thin flexible piece of wood. 
 
 Beam - A structural member supporting a load applied transversely to it. 
 
 Beam - The width of a vessel. 2. The supporting structure for a deck. 
 
 Bearding line - The line formed by the intersection of the inside of 
 the planking with the side or face of the keel. 
 
 Bending, steam - The process of forming curved wood members by steaming 
 or boiling the wood and bending it to a form. 
 
 Bilge plank - A strengthening plank laid inside or outside of a vessel 
 at the bilge's turn. 
 
 Binding strake - An extra thick strake of side or deck planking. 
 
 Buttock - That a part of a vessel's stern above her waterllne which 
 overhangs or lies abreast of the stern post; the counter. 
 
 Cant frames - Frames whose plane of support is not perpendicular to 
 the fore and aft line. 
 
 Capping - Fore and aft finished piece along the topsides of an open 
 boat, often improperly termed gunwale; called a covering board, 
 margin plank or plank sheer in a decked vessel. 
 
 Carl in - The fore and aft members of the deck framing system. 
 
 Carvel planked - Smooth skinned planking whose strakes run fore and aft. 
 
 Caulking (calking, (n)) - Cotton or other fiber driven Into planking 
 seams to make them watertight. 
 
 37 
 
Celling - An inner skin of the hull often used to add strength in boats 
 having sawn frames. In some cases the ceiling is not structural 
 But merely serves to line the hull for decorative purposes or for 
 ease in cleaning. 
 
 Check - A lengthwise separation of the wood that usually extends across 
 the rings of annual growth and commonly results from stresses 
 set up in wood during seasoning. 
 
 Chine - The line of intersection of the bottom with the side of the vessel. 
 
 Clamp - The fore and aft member at the sheer line of the vessel to 
 which the deck beams usually fasten. 
 
 Clench planking - Lapstrake, in which the adjacent planks overlap like 
 clapboards of a house. 
 
 Clinker built - See clench planking. 
 
 Coat, mast - A protective piece, usually canvas, covering the mast 
 wedges where the mast enters the deck. 
 
 Cold bent (frames) - Frames which are bent on forms and after shaping 
 are fitted to the vessel. 
 
 Cove line - A hollowed out decorative line found along the sheer of a boat. 
 
 Covering board - A plank used as a "washboard" or "plank sheer" along 
 the outer edge of the deck. - see "capping". 
 
 Dead rise • The amount the bottom rises from keel to chine • most 
 
 properly applied to "Vee" bottom construction but also used in 
 reference to the rising bottom of round bottom boats. 
 
 Deadwood - The vertical structure built up from the keel to support 
 the cant frames at the stern or stem. 
 
 Decay - The decomposition of wood substance by fungi. 
 
 1. (Advanced or typical) - The older stage of decay in which the de- 
 struction is readily recognized because the wood has become punky, 
 soft and spongy, stringy, ringshaked, pitted or crumbly. Decided 
 discoloration or bleaching of the rotted wood is often apparent. 
 
 2. (Incipient) - The early stage of decay that has not proceeded 
 far enough to soften or otherwise perceptibly impair the hardness 
 of the wood. It is usually accompanied by a slight discoloration 
 or bleaching of the wood. 
 
 Diagonal planking - Planking laid on an angle to the keel. 
 
 38 
 
Dry rot - A term loosely applied to any dry* cnimbly rot but •specially 
 to that which, when in an advanced stage, permits the wood to be 
 crushed easily to a dry powder. The term in actually a misnoner 
 for any decay, since all fungi require considerable moisture for 
 growth. 
 
 Dutcfaaan - Wooden block or wedge used to fill the void in a badly made 
 butt or Joint; a graving piece or repairing patch in a deck; 
 filler; shim; short plank. 
 
 Edged-grained lumber - Lumber that has been sa%red so that the wide sur- 
 faces extend approximately at right angles to the annual growth 
 rings. Lumber is considered edged grained when the rings form an 
 angle of 43° to 90° vith the wide surface of the piece. 
 
 Edging - Amount required to be cut away from the edge of a plank in 
 fitting strakes. 
 
 Facing • Building one piece of timber on another for strength or finish 
 purposes « 
 
 Flat-grained lumber - Lumber that has been sawed in a plan approximately 
 perpendicular to a radius of the log. Ltmiber is considered flat 
 grained when the annual gro«rth rings make an angle of less thar 
 AS* with the surface of the piece. 
 
 Floor - A transverse member being across the keel or a deep member of 
 transverse framing. 
 
 Futtock - Curved parts or sections of transverse frames extending from 
 the floor timbers to the top timbers. 
 
 Garboard - The strake nearest the keel. 
 
 Green - Freshly sawed lumber, or l«imber that has received no Intentional 
 drying; unseasoned. The term does not apply to lumber that may 
 have become completely wet through waterlogging. 
 
 Grub beam - A built up beam of short heavy timbers used to shape a 
 round stem. 
 
 Heartwood - The wood extending from the pith to the sapwood, the cells 
 
 of which no longer participate in the life processes of the tree. 
 Heartwood may be infiltrated with gums, resins, and other materials 
 that usually make it darker and more decay resistant than sapwood. 
 
 Bom timber - One or more timbers forming the main support for an over- 
 hanging stern and extending aft from the upper end of the stern 
 post. Also used for timber connecting the shaft log and body pose 
 with the rudder post. 
 
 39 
 
Horse (n) The form upon which a small boat Is built. 
 
 Horse (v) To drive home, as to horse caulking. 
 
 Hot frame - A frame which, after being softened by heat, is pulled 
 into shape as it is installed. 
 
 Joint - The junction of two pieces of wood or veneer. 
 
 Butt joint - An end joint formed by abutting the squared ends 
 of two pieces. Because of the inadequacy in strength of 
 butt joints when glued, they are not generally used. 
 
 Edge joint - The place where two pieces of wood are joined to- 
 gether edge to edge, commonly by gluing. The joints may 
 be made by gluing two squared edges as in a plain edge joint 
 or by using machined joints of various kinds, such as 
 tongued-and-grooved joints. 
 
 Scarf joint - An end joint formed by joining with glue and mechanical 
 fastenings the ends ot two pieces that have been tapered or 
 beveled to form sloping plane surface, to the same length in 
 both pieces. In some cases, a step or hook may be machined 
 into the scarf to facilitate alignment of the two ends, in 
 which case, the plane is discontinuous and the joint is known 
 as a stepped or hooked scarf joint. 
 
 End joint - The place where two pieces of wood are joined together 
 end to end, commonly by scarfing and gluing. 
 
 Lap joint - A joint made by placing one piece partly over another 
 and bonding the overlapped portions. 
 
 Starved Joint - A glued joint that is poorly bonded because in- 
 sufficient quantity of glue remained in the joint. Starved 
 joints are caused by the use of excessive pressure or in- 
 sufficient viscosity of the glue, or a combination of these, 
 which result in the glue being forced out from between the 
 surfaces to be joined. 
 
 King plank - The centerline plank of a deck. 
 
 Knot - That portion of a branch or limb which has been surrounded 
 by subsequent growth of the wood of the trunk or other portion of 
 the tree. As a knot appears on the sawed surface, it is merely a 
 section of the entire knot, its shape depending upon the direction 
 of th« cut. 
 
 Limber - A hole allowing the free passage of water from one area to another. 
 
 40 
 
Molding - Measurement of a plank or timber froit inboard Co outboard, 
 I.e., parallel to the plane in which the member lies; opposed to 
 siding measured at right angles to such plane. Thus, the molding 
 of a frame is measured in the thwartship direction while that of a 
 stern piece is its cross sectional dimension fore and aft. 
 
 Nib - The squared off end of a tapered piece such as a scarf. 
 
 Partner - Stiffening or supporting pieces fitted in way of the passage 
 of a mast through a deck. 
 
 Paying - Calking. 
 
 Pitch pocket - An opening extending parallel to the annual growth rings 
 containing, or that has contained, pitch, either solid or liquid. 
 
 Plank sheer - see capping. 
 
 Preservative - Any substance that for a reasonable length of time is 
 
 effective in preventing the development and action of wood-rotting 
 fungi, borers of various kinds and harmful insects that deteriorate 
 wood. 
 
 Prick post - An outer post supporting an outboard rudder. 
 
 Quartersawed lumber - Another term for edge-grained lumber. 
 
 Rabbet - A longitudinal channel or groove in a member which receives 
 another piece to make a joint. 
 
 Ripped frame - A bent frame partially split longitudinally to make 
 bending easier. 
 
 Rot - see decay. 
 
 Shake - A separation along the grain, the greater part of which occurs 
 between the rings of annual growth. 
 
 Shelf - Line of timbers bridging and thus stiffening frames but chiefly 
 for supporting the end of the deck beams. 
 
 Siding - see molding. 
 
 Spiling - The edge curve in a strake of planking. 
 
 Split - A lengthwise separation of the wood due to the tearing apart 
 of the wood cells. 
 
 Stain - A discoloration In wood that nay be caused by such diverse 
 agencies as micro-organisms, metal » or chemicals. The term 
 alto applies to materials used to Impart color in wood. 
 
 41 
 
Stealer - In the shell planking toward the ends of a vessel a 
 
 strake introduced as a single continuation of two tapering strakes. 
 
 Stopwater - A softwood piece driven across a scarf, as in the keel, to 
 prevent seepage of water into the hull. Any contrivance to 
 accon^lish this purpose. 
 
 Strake - One of the rows or strips of planking constituting the sur- 
 face of the hull. 
 
 Wane - Bark or lack of wood from any cause on edge or corner of a piece. 
 
 Warp- - Any variation from a true or plane surface. Warp includes bow, 
 crook, cup and twist or any combination thereof. 
 
 Weathering - The mechanical or chemical disintegration and discoloration 
 of the surface of wood is caused by exposure to light, action of 
 dust and sand carried by winds and alternate shrinking and swelling 
 of the surface fibers with the variation in moisture content brought 
 by changes in the weather. Weathering does not include decay. 
 
 Welt - A strip of wood fastened over a flush joint or seam for strengthen- 
 ing purposes. A seam batten* 
 
 A2 
 
VII. REFERENCES 
 
 The following recommended references should be of help to 
 persons concerned with wooden boats. 
 
 Many of these publications contain additional lists of 
 references which cover practically every facet of wood and wooden 
 construction that might be of interest. 
 
 1. Rules for the Construction and Classification of Wooden Ships / 
 American Bureau of Shipping, 45 Broad St., N.Y., N.Y. 
 
 2. Naval Architecture of Small Craft by D. Phillips Birt, 
 Philosophical Library, Inc. 15 E. 40th Street, N.Y., N.Y. 
 (Descriptive information on European small craft.) 
 
 3. Boatbuilding by Howard I. Chapell, W.W. Norton Co., N.Y, N.Y. 
 (Comprehensive, well indexed and readable handbook of wood 
 construction, though somewhat dated.) 
 
 4. Fir Plywood Technical Data Handbook , Douglas Fir Plywood 
 Association, Tacoma, Wa. (Good reference book on fir plywood.) 
 
 5. Rules for the Construction and Classification of Wood Yachts , 
 Lloyd's Register of Shipping, 71 Fenchurch Street, London, England 
 
 6. National Design Specifications for Stress Grade Lumber and its 
 Fastenings , National Lumber Manufacturers Association, 1319 18th 
 Street N.W. , Washington, D.C. (Design information used for 
 selecting fastenings and wood scantlings.) 
 
 7. Wood: A Manual for its Use in Wooden Vessels , Navy Department, 
 Bureau of Ships, U.S. Government Printing Office, Washington, D.C. 
 (Discussion of wood in small craft and ship construction.) 
 
 8. Wood: A Manual for its Use as a Shipbuilding Material , 
 NAVSHIPS 250-336, U.S. Government Printing Office, Washington, 
 D.C. 
 
 Vol. I - Basic Wood Technology Applicable to 
 
 Shipbuilding 
 Vol. II - Techniques and Practices Applicable 
 
 to Preservation and Storage. 
 Vol. Ill - Technical Data Applicable to Boat and Ship 
 
 Design 
 Vol. IV - Techniques Applicable to Boat and 
 
 Ship Construction 
 (Wood construction as it applies to the Navy. Good general 
 reference. ) 
 
 43 
 
9. Inspector's Handbook for Plastic Boats and Small Craft y 
 NAVSHIPS 250-529-1 
 
 10 . Inspector's Handbook for Wooden Boats and Small Craft y 
 NAVSHIPS 250-529-2, (Number 9 and 10 are pocket-sized outlines for 
 the Navy Inspector. Useful for evaluating new boats.) 
 
 11. Fabrication and Design of Glued Laminated Wood Structural 
 Members, U.S. Department of Agriculture, Technical Bulletin No. 
 1069, U.S. Government Printing Office, Washington, D.C. 
 (Production and use of plywood and wood laminate is covered 
 thoroughly. ) 
 
 12. Wood Handbook (Handbook No. 72) , U.S. Department of 
 Agriculture, U.S. Government Printing Office, Washington, D.C. 
 (Definitive treatment on wood, glues, fastenings, preservatives, 
 etc. All phases of the production and use of wood.) 
 
 13. Wood, Colors and Kinds (Handbook No. 101) , U.S. Department of 
 Agriculture, U.S. Government Printing- Office, Washington, D.C. 
 (American Wood - description of common species and color plates 
 showing samples.) 
 
 44 
 
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