Building small wooden boats in Myanmar 12 ft & 18 ft Multi-purpose boats

Transcription

1 12 ft & 18 ft Multi-purpose boats Immediate Rehabilitation of Subsistence Fisheries Livelihoods in Areas Affected by Cyclone Nargis (OSRO/MYA/805/SWE) Funded by the Government of Sweden

2 Cover photograph: Completed boat of the 12ft and 18ft designs at the boatyard in Kungyangon. FAO/D. Davy

3 12 ft and 18 ft multi-purpose boats by: Daniel Davy FAO Consultant and Kilian Svensson FAO Consultant FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS Yangon, 2009

4 The designations employed and the presentation of material in this information product do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations (FAO) concerning the legal or development status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. The mention of specific companies or products of manufacturers, whether or not these have been patented, does not imply that these have been endorsed or recommended by FAO in preference to others of similar nature that are not mentioned. The views expressed in this publication are those of the author(s) and do not necessarily reflects the views of FAO. All rights reserved. Reproduction and dissemination of material in this information product for educational or other non-commercial purposes are authorized without any prior written permission from the copyright holders provided the source is fully acknowledged. Reproduction of material in this information product for resale or other commercial purposes is prohibited without written permission of the copyright holders. Applications for such permission should be addressed to: Chief, Electronic Publishing Policy and Support Branch Communication Division, FAO, Viale delle Terme di Caracalla, Rome, Italy or by to: FAO 2009

5 Preparation of this document This manual has been developed from information collected during a Food and Agriculture Organization (FAO) project on Immediate Rehabilitation of Subsistence Fisheries Livelihoods in Areas Affected by Cyclone Nargis (OSRO/MYA/805/SWE), funded by the Government of Sweden. The manual draws on experience gained during a boatbuilding demonstration project in the village of Kathit Kone, near Kungyangontraining, in Myanmar in 2009, where a number of boats of the 12 ft design and nine of the 18 ft design were built. Daniel Davy, FAO Consultant Naval Architect, was responsible for the final designs, and Kilian Svensson, FAO Consultant Master Boatbuilder, was responsible for organizing and conducting the boatbuilding activities. The preparation of this manual was completed under the technical supervision of Ari Gudmundsson, Fishery Industry Officer (Vessels), Fisheries and Aquaculture Department and with the support of Emergency Operations and Rehabilitation Division, Technical Cooperation Department, FAO, Rome, Italy. iii

6 Abstract This step-by-step manual contains information on the construction of small multi-purpose boats typical of those found in the Ayeyarwaddy Delta in Myanmar. Its purpose is to give organizations access to detailed information on boatbuilding, which will allow the production of small boats appropriate to the Delta. The manual is also intended to assist organizations in their understanding of the boatbuilding process and to provide guidelines on good practice. It should assist in the review of contracts and quality control in boatbuilding. The manual provides information on two boat designs: 12 ft and 18 ft boats. It also gives the scantlings and material requirements as well as the guidelines for selecting and using timber for the boat construction. The largest part of the manual describes how to build the boats step-by-step. Finally, the manual contains boatbuilding guidelines for wooden boats of less than 7 m in length and operating at speeds of less than 12 knots. iv

7 CONTENTS 1. INTRODUCTION DESIGNS SCANTLINGS MATERIAL REQUIREMENTS GUIDELINES FOR SELECTING AND USING TIMBER STEP-BY-STEP CONSTRUCTION METHOD EDGE NAILING OF PLANKS ADDITIONAL INFORMATION BOATBUILDING GUIDELINES v

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9 1. INTRODUCTION This manual contains information on the construction of small multi-purpose boats typical of those found in the Ayeyarwaddy Delta in Myanmar. Its purpose is to give organizations access to detailed information on boatbuilding, which will allow the production of small boats appropriate to the Delta. It is also intended to assist organizations in their understanding of the boatbuilding process and to provide guidelines on good practice. It should assist in the review of contracts and quality control in boatbuilding. 2. DESIGNS Information on two designs 12 ft and 18 ft boats is presented. The boats are simple wooden canoes of flat-bottomed construction, typical of the small multi-purpose boats found in the Ayeyarwaddy Delta. The 12 ft design is intended to be propelled by paddles and the 18 ft design may be propelled by paddles, oars or long tail motor. (Note: No information is given on the installation of motors.) There are many local variations in boat design in the Delta. These mainly concern traditional preferences and features to suit local environmental conditions and fishing methods. When this manual is used by an experienced boatbuilder from the Delta, it will be possible to vary the given designs slightly to achieve the desired result. The main details of the designs are given below. 12 ft Boat Type of boat Propulsion Length Beam Depth Bauk Tu multi-purpose boat from Delta Paddles 12 ft 6 in (3 810 mm) measured along length of top plank 32.5in (830 mm) measured across widest point 11 in (280 mm) measured from top of keel at mid-section 18ft Boat Type of boat Propulsion Length Beam Depth Gault Chun multi-purpose boat from the Delta Oars and paddle 18 ft (5 480 mm) measured along length of top plank 4 ft (1 225 mm) measured across widest point 19 in (480 mm) measured from top of keel at mid-section 1

10 12 ft Bauk Tu 2

11 18 ft Gault Chun 3

12 3. SCANTLINGS 12-ft Bauk Tu Typical Frame Section 18-ft Gault Chun Typical Frame Section 4

13 4. MATERIAL REQUIREMENTS 12ft Bauk Tu Materials list Item Length (min) Width Thickness No. of pieces Timber (mm) (mm) (mm) A Lower side plank B Upper side plank C Transom D Keel E Inner bottom plank F Outer bottom plank G Covering board (side) H Stem I Clamp J Frames K Floors L Floorboards Floorboard transverses M Decks N Transverses O Mast supports Fastenings* Joint Length Thickness No. of pieces (mm) (mm) Nail Planks to frames Nail Keel to frames Nail Bottom plank to side plank Nail Clamp to plank P Nail Frame to frame Nail Rail cap Nail Plank to plank * Note: All fastenings should be hot-dipped galvanized. 5

14 18ft Gault Chun Materials list Length (min) Width Thickness No. of pieces Timber (mm) (mm) (mm) i i i A Lower side plank B Upper side plank C Stringer D Transom min. 1 E Keel F Inner bottom plank G Outer bottom plank H Covering board (side) I Stem J Inwale K Rail cap L Frames M Floors N Floorboards N Floorboards N Floorboard transverses P Decks Q Transverses S Oar supports T Mast supports Fastenings* Joint Length Thickness No. of pieces (mm) (mm) (mm) R Bolt + (nut & washer to suit) Frame to frame Nail Planks to frames Nail Keel to frames Nail Stringer to frame Nail Bottom plank to side plank Nail Inwale to frame Nail Frame to frame Nail Rail cap Nail Plank to plank * Note: All fastenings should be hot-dipped galvanised. 6

15 5. GUIDELINES FOR SELECTING AND USING TIMBER Wood specification * Boat builder s preferred wood ** Alternative 1 Alternative 2 Thin Gan (Hopea Odorata Roxb) Specific gravity 0.68 (medium) Durability very good Shrinkage small Seasoning easy Ka Nyin (Dipterocarpus spp.) Specific gravity 0.75 (medium) Durability moderate Shrinkage considerable Seasoning moderately easy Pyin Ma (Lagerstroemia speciosa) Specific gravity 0.53 (light) Durability good Shrinkage moderate Seasoning slowly Length If possible, it is recommended that boards be a minimum of 20 ft (6.1 m) long. Consideration should be given to the quantity of boats to be built in each size when ordering timber. If a board is not suitable for the larger boat due to damaged or split ends, it may be suitable for the smaller boat. Sapwood Seasoning Storage Sapwood, the outer and often lighter coloured part of the log, should never be used in boatbuilding. It is normally easy to distinguish this part of a board. Seasoning is required for all boards. Boats should not be built with freshly sawn timber because shrinking and warping (bending) will occur. A minimum of four weeks during dry weather and more during the wet season are recommended for seasoning. It is recommended that the seasoning be as long as practical. Freshly sawn boards should be selected and carefully stacked immediately after sawing. The ends should be painted to avoid splitting. The layers of planks should be separated by transverse battens of equal thickness (1 x 2 ), spaced no more the 90 cm (3 ft) apart. The battens at the ends should be as close to the board ends as possible. * All timber should be legally cut and from sustainably managed sources with appropriate government clearances. The situation regarding timber supply is constantly changing and guidance on suitable species may be updated in the future. ** Thin Gan is facing a high risk of extinction in the wild in the medium-term future and is a reserved species in Myanmar for which government permission is needed before cutting. Alternatives should therefore be considered. 7

16 6. STEP-BY-STEP CONSTRUCTION METHOD 1 12 ft & 18 ft The floors The shape of the boat is generated from the floor timbers and the natural curve of the lower side planks (see step 12). 12 ft The dimensions of the necessary floor timbers are shown in step 2 and their positions are given in step 8. The timber required is: 38 mm x 75 mm. 18 ft The dimensions of necessary floor timbers are shown in step 3 and their positions are given in step 9. The timber required is: 38 mm x 100 mm. These shapes can be drawn onto paper for use as full-size templates or drawn directly onto the timber to be cut ft Floor dimensions Dimensions of floor timbers are as follows: Note: The dimensions for floors at other frame positions may be determined once stem and transom are fitted (see step 19). 8

17 3 18 ft Floor dimensions Dimensions of floor timbers are as follows: Note: The dimensions for floors at other frame positions may be determined once stem and transom are fitted (see step 19). 9

18 4 12 ft & 18 ft Mark out floors Draw the shape of the floors on the timber. 12 ft The timber required is: 38 mm x 75 mm. 18 ft The timber required is: 38 mm x 100 mm ft & 18 ft Cut floors Cut the floor timbers to the required sizes. Shape the bottom of the floor with the required curve. 12 ft The bottom curve is: zero. 18 ft The bottom curve is: up to 23 mm (see step 3) ft & 18 ft Prepare lower side planks Cut two planks to the same size and shape to ensure symmetry of the boat; this is done by clamping the planks together while working. 12 ft The timber required is: 180 mm x 16 mm x mm. 18 ft The timber required is: 220 mm x 19 mm x mm. 10

19 7 12 ft & 18 ft Mark lower side planks The positions of the frames and the angles of the ends of the planks are marked on the prepared planks. The required dimensions are given in steps 8 and 9. Note: The forward (stem) end of the planks should be cut to the correct angle, whereas the aft end (transom) is not cut yet. This is left long to be cut later; the additional length should be about 150 mm, to suit local preferences ft Lower side plank dimensions The lower side plank is marked out to the following dimensions: 11

20 9 18ft Lower side plank dimensions The lower side plank is marked out to the following dimensions: ft Install floor at frame 4 18 ft Install floor at frame 5 Align the floor to the line marked on plank. Pre-drill two nail holes (see step D in Section 6.1) and fasten the planks to each end of the floor. Note: The floor is fitted aft of the marked line (see step 11). 12 ft & 18 ft The fastenings required are: 2 mm x 50 mm nails for each frame. 12

21 11 12 ft Install floor at frame 5 18 ft Install floor at frame 6 Repeat step 10. Note: The floor should be fitted in front of the marked line. In general, the floors in the forward part of the boat are fitted in front of the marked line and those in the aft part behind the marked line ft & 18 ft Set up lower side planks Place the assembly of planks and floors the right way up on the build frames. See how the angle of the floors defines the curve in the bottom of the boat as the ends are brought together. Note: This curve may be adjusted a little to suit local preference. If significant change is required, the lower side planks will need shaping at the ends ft & 18 ft Prepare stem 12 ft The timber required is: 100 mm x 75 mm x 600 mm. 18 ft The timber required is: 125 mm x 100 mm x 950 mm. 13

22 14 12 ft & 18 ft Shape stem The stem has the following dimensions: 12 ft The dimensions are: A = 490 mm, B = 25 mm, C = 600 mm. 18 ft The dimensions are: A = 750 mm, B = 90 mm C = 950 mm. Note: The rebate is cut to suit the planking thickness and angle ft & 18 ft Assemble stem & lower side planks The stem is offered up to the lower side planks. A rope may be used to draw the ends of the planks together. Note: The angle of the stem is set by the angle of the cut at the end of the lower side plank (see note 7) ft & 18 ft Fit stem A clamp should be used to ensure a good fit and to hold the planks in place. Pre-drill the nail holes (see step D in section 6.1) and fasten the stem to one plank and then to the other. 12 ft & 18 ft The fastenings required are: 2 x 50 mm nails for each plank. Note: Take care not to split plank ends when fastening. 14

23 17 12 ft & 18 ft Mark & cut transom 12 ft Transom dimensions 12 ft The timber required is: 250 mm x 32 mm x 600 mm. 18 ft The timber required is: 320 mm x 40 mm x 900 mm. 18 ft Transom dimensions ft & 18 ft Fit transom A clamp should be used to hold the planks in place. Predrill the nail holes (see step D in section 6.1) and fasten the transom to one plank and then the other. 12 ft & 18 ft The fastenings required are: 2 mm x 50 mm nails for each plank. Notes: 1) The angle of the transom is set by the angle marked on the lower side planks (see steps 8 & 9). 2) Take care not to split the plank ends. 3) The ends of the planks are left long to be cut later. 15

24 19 12 ft & 18 ft Fit remaining floors The remaining floors can now be cut to size by taking measurements at the boat. The timber required is given in step 1. See step 10, 11 and 20 for installation procedures. Note: The floors in the forward part of the boat are fitted in front of the marked line and those in the aft part, behind the marked line ft & 18 ft Bevel floor ends The ends of the floors should be bevelled to suit the curve in the plank ft Mark plank overlap Carefully mark a line 19 mm below the top edge of the plank. This line is to give the overlap between the lower and upper side planks. 16

25 22 12 ft & 18 ft Prepare frames Cut lengths of timber to make the frames. 12 ft The timber required is: 50 mm x 38 mm x 350 mm. 18 ft The timber required is: 62 mm x 38 mm x 600 mm ft & 18 ft Frame details The frames have a notch cut to suit the upper side plank. The notch is the depth of the thickness of the top plank and extends to the marked line for the plank overlap (see step 21) ft Fit frames Fit the frames aligning the notch with the line marked on the plank. Frames are slightly over length & will be cut later (see step 48). The fastenings required are: 50 mm nails. Pre-drill the nail holes (see step D in section 6.1). Note: A temporary keelson may be fitted at this stage to ensure that the structure remains rigid & straight. 17

26 25 12 ft & 18 ft Frame details Note the following frame details: 1) The frames are not bevelled but fitted aligned with the planking. 2) The frames are halved where they lap the floors. 3) The frames in the forward part of the boat are fitted in front of the floors and those in the aft part behind the floors ft Fit frames The fastenings required for the frame to floor joint are: 1 mm x 75 mm x 8 mm bolt or 2 mm x 50 mm nails. Pre-drill the nail holes (see step D in section 6.1). Note: Where bolts are used, it is recommended that nails are used as temporary fastenings when assembling the frames ft & 18 ft Framing complete Note: Temporary transverses should be fitted at this stage, to ensure structure remains rigid & straight. 18

27 28 18 ft Cut bilge stringer Offer up the timber for the bilge stringer, and mark and cut the correct angle at the stem. The timber required is: 90 mm x 32 mm x mm ft Install bilge stringer Starting at the stem fit the bilge stringer. The fastenings required are: 2 mm x 50 mm nails for each plank. Pre-drill the nail holes (see step D in section 6.1) ft Install bilge stringer Working back from the stem and making use of a clamp where required, continue fastening the stringer to the frames. When complete, the lower plank and stringer should be edge-fastened (see section 6.1). The plank overlap should be marked on the top edge of the stringer (see step 21). See step 21 for marking edge of stringer. 19

28 31 12 ft & 18 ft Mark & cut out stern cover boards The cover boards are designed to suit local preferences. The timber required is the same thickness as the hull planking ft & 18 ft Mark & cut out bow cover boards The cover boards are designed to suit local preferences. The timber required is the same thickness as the hull planking ft & 18 ft Fit bow & stern cover boards Fasten the cover boards to the stem (or transom) and edgefasten to the upper edge of the lower plank (or stringer.) For edge fastening and pre-drilling, see section 6.1. Note: The inside face of the cover boards should be flush with the lower side plank (or stringer.) 20

29 34 12 ft & 18 ft Prepare upper side planks Cut a pair of planks to the same size and shape to ensure symmetry of the boat. This is done by clamping the planks together when working. The lower, outer edge of these planks is planed off by about 1/3 of the thickness (see illustration). 12 ft The timber required is: 160 mm x 16 mm x mm. 18 ft The timber required is: 200 mm x 19 mm x mm. Note: The length of the planks is determined at the boat. Also, the aft end of the plank is left over long and will be cut later (see step 47). The additional length should be about 150 mm, to suit local preferences ft & 18 ft Fit upper side planks The upper side planks are bent into place; several pair of hands will be required for this step. Note: These planks do not touch the stem or transom (see step 37). 21

30 36 12 ft & 18 ft Fit upper side planks Note how the plank fits inside the lower plank (or stringer) into the notches in the frames. A clamp may be required to assist in this process. The fastenings required are: 2 mm x 50 mm nails for each frame. Pre-drill the nail holes (see step D in section 6.1) ft & 18 ft Upper side plank ends The upper side planks fit inside the bow and stern cover boards. Note: The upper side planks are cut in order not to touch the stem or transom. There is a 10 to 15 mm gap ft & 18 ft Turn boat over Turn the boat over on the built frames. 22

31 39 12 ft & 18 ft Prepare bottom Before fitting the keel, there are several steps to complete: 1) Cut frame ends and transom to length (level with bottom). 2) Bevel bottom edge of lower side planks; this should be level with the bottom of the floors. 40 Fit keel 12 ft The timber required is: 75 mm x 25 mm x mm & the fastenings required are: 2 mm x 50 mm nails for each floor. 18 ft The timber required is: 100 mm x 32 mm x mm & the fastenings required are 2 mm x 62 mm nails for each floor. Note: The keel may be tapered to 70 mm wide at the ends; this will assist the planks forming the curved bottom. 41 Bottom planks Offer up planking and cut approximately to length. 12 ft The timber required is: 2 pieces 125 mm x 16 mm x mm & 2 pieces 125 mm x 16 mm x mm. 18 ft The timber required is: 2 pieces 150 mm x 19 mm x mm & 2 pieces 150 mm x 19 mm x mm. 23

32 42 12 ft & 18 ft Fit bottom planks Mark frame positions on planks; once marked, the bottom planks can be fitted. A clamp will be required to keep the plank edges tightly together. The fastenings required are: 2 mm x 50 mm nails for each floor. Pre-drill the nail holes (see step D in section 6.1) ft & 18 ft Edge nail planks Once fitted, the bottom planks can be edge fastened (see section 6.1) ft & 18 ft Cut edge of bottom planks The outboard edge of the bottom planks can be trimmed and then made smoother with a plane. Note: The bottom planks should extend beyond the side planks by about 6 mm to assist in puttying the bottom seam. 24

33 45 12 ft & 18 ft Fasten edges The bottom planks need to be fastened to the side planks along the edges. The holes should be pre-drilled, and care should be taken not to split the planks ft & 18 ft Fasten edges At the ends of the bottom planks, the edges need to be fastened to the adjacent plank. The holes should be pre-drilled, and care should be taken not to split the planks (see step D in section 6.1) ft & 18 ft Ends of planks The aft ends of the side planks can be cut and shaped. The shape is designed to suit local preferences. 25

34 48 Mark the frames Turn the boat over. Cut the frame tops in line with the upper side plank. Note: The frame tops will require further trimming once the inwales are fitted (see step 51). The frames need to be marked to suit the inwale that is to be fitted. 12 ft The timber required is: 50 mm x 19 mm x mm. 18 ft The timber required is: 62 mm x 19 mm x mm. 49 Cut the frames Once marked, the frame tops can be cut to the correct dimensions. 12 ft Once the frame top is removed, the inwale is placed against the inner face of the hull plank. 18 ft The frame top is notched to receive the stringer. 50 Fit the inwales 12 ft The fastenings required are: 2 mm x 38 mm nails for each frame. 18 ft The fastenings required are: 50 mm nails for each frame. Pre-drill the nail holes (see step D in section 6.1). 26

35 51 18 ft Cut the frame tops It is recommended that: 1) the frame tops are cut so that they do not touch the under-side of the gunwale caps, which are fitted later (see step 55); 2) the frame tops and the edges of the planking and the stringer are treated (see step 61) ft Mark the rail cap The rail cap will have to be fitted in 3 or more sections to accommodate the curve of the gunwale. Here, a board is offered up so that it can be marked with the required curve on its underside. The rail cap is cut from ¾ (19 mm) timber ft Cut the rail cap The rail cap is cut to the marked lines. 27

36 54 18 ft Dry fit the rail cap Check the sections of rail cap by offering them up to the boat ft Fit the rail cap Mark and cut scarf joints in the ends of the sections of gunwale cap; fasten the rail cap to the top of the hull plank and the gunwale stringer. The rail cap is fastened to the hull plank and stringer with 38-mm nails spaced at 125 mm to 150 mm. Pre-drill the nail holes (see step D in section 6.1) ft & 18ft Trim stringers and hull for decks Where the forward and aft decks are to be fitted, the edge of the stringers and hull plank need to be trimmed so that they are horizontal. 28

37 57 12 ft & 18 ft Fit the bow and stern decks Short decks or seats are fitted at the ends of the boat. The decks are designed to suit local preferences. 12 ft The timber required is: 16 mm thick. 18 ft The timber required is: 19 mm thick ft & 18 ft Finish details Final shaping and finishing of details should be completed. These details are designed to suit local preferences and may include: the shaping of styling pieces in bow and stern; the final details of the stem and transom ft & 18 ft Finished boat The boat is now ready for puttying and timber treatment. 29

38 60 12 ft & 18 ft Putty seams Putty is made up to a traditional recipe using a natural powder (see right) and oil, either cooking or diesel. The putty is rolled into lengths and worked into the seams. Note: This process will need to be regularly repeated to keep the boat watertight ft & 18 ft Treat timber A timber treatment is made to a traditional recipe using diesel and engine oil. The mixture is applied all over the boat inside and out. Note: 1) This process will need to be regularly repeated to keep the boat in good condition. 2) This treatment is potentially harmful to the environment and humans ft & 18 ft Finished boat The boat is now ready for the final details. 30

39 63 12 ft & 18 ft Final fastenings A few days after the completion of the boat, the planks will have dried a little, and movement and shrinkage will have taken place. At this point, it is necessary to put the final fastenings in. These are required where the top plank overlaps the lower plank (or stringer) ft & 18 ft Final fastenings Two equally spaced fastenings are required between each frame. 12 ft The fastenings required are: 38-mm nails. 18 ft The fastenings required are: 50-mm nails. Pre-drill the nail holes (see step D in section 6.1) ft & 18 ft Final details Final details are designed to suit local preferences. In some areas, it is necessary to fit transverse frames in the bow and stern; these are used for various purposes, including securing the boat. 31

40 66 12 ft & 18 ft Final details Final details are designed to suit local preferences. Other details will include: Floorboards. See Section 4 for material requirements. These should be easily removable and in general not fitted in the middle frame space of the boat because this is used for bailing water. Paddles/oars. These need to be built to suit the user s requirements. Oars will need slots in the side of the boat and support posts ft & 18 ft Mast support A mast support may be added to suit local preferences. This will typically consist of: 1) a transverse of 75 mm x 38 mm, fixed to a frame between the top of the lower side plank and the top of the upper side plank; 2) a block or transverse fixed to the keel below this. Both parts have a hole for the mast of about 40 mm to 50 mm. The mast support should be fitted at frame 7 on the 12 ft design and frame 9 on the 18 ft design. 32

41 68 12 ft & 18 ft Launch After launch, the boats are likely to leak initially. This is normal since it takes a little time for the planking to swell up now that it is in the water. If the problem is serious, more putty may need to be applied in the seams below the water. At this stage, before the boats are in regular use, it is very important to ensure that they don t dry out in the sun, since this will cause shrinkage of the timber. It is best to keep the boats in a shaded area or in the water until they are handed over to the users. Alternatively, they can be filled with leaves or wood shavings, which may be kept wet. 33

42 6.1 EDGE NAILING OF PLANKS A Mark nail positions When edge fastening, planks slots need to be cut for the nails. Mark these out carefully to ensure that the nails are in the correct positions. Two nails are used between each frame, and the slot is cut between two lines; the first is 1 x the plank thickness from the edge and the second is about 2.5 x the plank thickness from the edge. B Cut nail slots Using a sharp V-shape chisel, cut the nail slots in the marked positions. The depth of the slot at the line closer to the plank edge should be just sufficient to accommodate the nail head. C Finished nail slots The finished nail slots should be neat and regularly spaced. 34

43 D Pre-drill holes To ensure that planks do not split, pre-drill the nail holes in the plank edge. The drill should be one size or 1 mm smaller than the nail. Note: In general, it is good to pre-drill nail holes in all locations, but it is particularly important to do so where the nails are close to the edge or end of the timber. E Insert nails Insert the nails into the predrilled holes. F Nailing Use a punch to drive the nails fully into the slots. Care should be taken not to split the planks. Note: In general, it is good to countersink nail holes by at least 3 mm in all locations. When not edge nailing, this can be done with a drill the same size as the nail head. 35

44 6.2 ADDITIONAL INFORMATION G Protection of joints To ensure that water does not settle between components and cause rot, it is desirable to protect the enclosed surfaces. This may be done with the timber treatment (see step 61) or by painting with primer. An alternative is to use a thick and flexible compound called mastic. This can be done cheaply by using the locally available components shown in the photograph. H Protection of joints The paint or mastic should be applied to the surface to be jointed before fastening. Note: Where pre-drilling is required, this should be done before applying the paint or mastic. I Protection of joints A completed joint. Note: The paint or mastic should squeeze out of the joint once assembled. 36

45 7. BOATBUILDING GUIDELINES 7.1 Introduction The guidelines are applicable to boats less than 7 m in length and operating at speeds of less than 12 knots. It is possible that some boat types may be outside the scope of these guidelines or not practically able to meet all sections. However, the intention is to provide useful information to organizations and authorities involved in building small boats. 7.2 Timber Timber should be well seasoned with a moisture content of 15 to 20 percent, of good quality and free from splits, sap wood and significant knots. The timber should be selected from available species known to have a locally proven record in boatbuilding with good resistance to rot. Keel and underwater planking should preferably have some resistance to marine borers. 7.3 Planking Hull planking should be from continuous lengths where possible. The width of planks should be kept as small as practical, preferably less than eight times the plank thickness. Planks should have two fastenings at each frame; wide planks should have three fastenings at each frame. Hull planking should be of a thickness which is suitable for the size of boat and the frame spacing. And in general planking of 15 mm or less should not be used. Planks should be fitted tight together; the gap between planks should be less than 1 mm. The seams between planks may be caulked with an organic material such as oakum and then filled with flexible waterproof filler. Joints in planks may be made by one of the following methods: on a frame; between frames using butt blocks on the inside of the planking; or by a scarf joint spanning two frames. 37

46 7.4 Frames Frames should be sawn from timber where the grain follows the shape of the frame. It is preferable for the bottom frames or floors to be bolted to the keel, and washers should be used under the head of the bolt and the nut. All frame components, especially the end grain, should be primed before assembly. 7.5 Keel and other components The keel should preferably be in one length. If necessary, the keel may be joined with a scarph of length (L) 5 x keel height (M) with end notches of depth (H) 0.2 x keel height. The scarph should be bolted together. The width of the stem should be the same as the keel. The landing of the planking on the stem should preferably have a length of 12 x the diameter of planking fastenings to avoid splitting the end of planks. Inwales and stringers should run continuously from stem to transom, and where possible, be of a single length of timber; where joints are required, the illustration below shows the requirements. On larger boats, it is good practice for the bilge stringer to be bolted in place. 38

47 The transom should be constructed in the same manner as the hull. It is preferable for the transom to be connected to the keel with a knee bolted in place. It is preferable to use a knee at the keel to stem joint. For boats of less than 6 m in length, it is recommended that the knee extends at least 150 mm along each joint and be bolted in place. All components should be primed before assembly. 7.6 Deck Deck planking should be of the same thickness as the hull sides. 7.7 Fastenings Hot-dipped galvanized nails and bolts should be used throughout the boat; alternatively, stainless steel grade AISI 316 fastenings may be used except for planks under the waterline. Electroplated fastenings are not recommended. Bolts should preferably have a hexagonal head and nut fitted with large washers. The minimum bolt size used should be 6 mm. The bolts in the keel assembly should be at least 8 mm in diameter. To avoid splitting timber, the minimum distances to the end and edge of timber parts should be as follows: Bolt diameter Minimum end distance Minimum edge distance Up to 8 mm 60 mm 35 mm 10 mm 70 mm 40 mm Planks should be fastened to the frames with nails of round or square section of the following dimensions. Planking thickness (mm) Minimum nail diameter (mm) Minimum nail length (mm) Nails should have a head of diameter of at least 2 x the nail diameter and should be countersunk 3-5 mm, and the head covered with waterproof, flexible compound. 39