Building the Wood/Epoxy Optimist

Building the Wood/Epoxy Optimist free pdf ebook was written by on December 11, 2007 consist of 19 page(s). The pdf file is provided by www.optiworld.org and available on pdfpedia since May 09, 2012.

building the wood/epoxy optimist an unofficial guide building the wood/epoxy optimist an unofficial guide the following..with woodworking ability. careful consideration of the class rules for wooden..for the wood/epoxy optimist which may be bought from the ioda...

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Building the Wood/Epoxy Optimist pdf




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Building the Wood/Epoxy Optimist - page 1
Building the Wood/Epoxy Optimist An Unofficial Guide
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Building the Wood/Epoxy Optimist - page 2
Building the Wood/Epoxy Optimist The following Guide describes one method of building a wood/epoxy International Optimist. An Unofficial Guide It is based on work by Tony Thompson of Canada to whom the International Optimist Dinghy Association (IODA) is deeply grateful. Neither IODA nor Tony is responsible for any errors. Builders who find such errors are asked to contact the IODA Secretariat. Note that any changes to this Guide can be found on the internet at www.optiworld/epoxy.html You don't have to use this Guide. Any method of building permitted by the Class Rules is allowed. Wooden boat have the advantages that each boat is unique: each builder adds his taste and craftsmanship to the final boat. Another advantage not overlooked by parents who pay the bills is longevity and strength. The sides and bow tran- soms made of 6 mm plywood are far more robust than any GRP hull. Careful consideration of the Class Rules for wooden hulls by the IODA was aimed at making the boat as similar as possible to the GRP Optimist. The new wood/epoxy specification has exactly the same shape as the GRP version; the side decks are wide and comfortable, there are no tanks and the boat can be built to the minimum weight. Fifty years after it was created by Clark Mills of Clearwater, Florida, the spec- ification for the wood/epoxy Optimist was revised with effect from 1 March 1997. It is intended to bring the Class back to its roots, an affordable boat which can be constructed by anyone with woodworking ability. This Guide must be read together with the Optimist plans and Class Rules for the Wood/Epoxy Optimist which may be bought from the IODA Secretariat for US$40.
Building the Wood/Epoxy Optimist - page 3
The rules allow several options in the construction of the boat, due to the dif- ferent weights of plywood available in different parts of the world. The description which follows is based on the use of relatively lightweight plywood which permits 12mm plywood to be used for the bottom panel. Construction Method The use of a simple mould made from cheap plywood or particle board/chipboard to form the bottom is recommended. The bottom can be screwed, clamped, or weighed down to hold the bottom curve while fitting the sides. A warning: The Optimist is tightly controlled by over 60 measurements and the tolerances of the wooden hull are in general plus or minus 5 mm. The tolerances are not meant to allow a builder to exploit the possible shapes available but to allow a competent builder to construct a legal hull. Although the method that is described here is meant to minimise the use of frames and moulds, it is very important to check measurements and fairness of the hull to ensure that the hull will measure when complete. The drawings enclosed with this article are intended as a supplement to the official plans and rules which are available from the IODA. The panels of the sides and bottom are expanded views of the panels. Think of an orange peel laid out flat so that when it is folded up it takes the shape of the orange again. It should not be used unless 12mm plywood of a maximum weight of 6 kilograms per square metre (kg/m2) and 6mm plywood max 3 kg/m2 is available.
Building the Wood/Epoxy Optimist - page 4
Materials As noted above this guide assumes the use of lightweight plywood. The most widely available type appears to be made using a wood known as Gaboune or Okoume. The 12mm plywood used for the base is 7 ply and appears to weigh between 16 and 18 kilos per standard sheet of 1220 x 2500mm. The 6mm plywood used for the sides and transoms is 5 ply (the minimum per- mitted by the Rules) and appears to weigh between seven and nine kilos per standard sheet of 1220 x 2500mm. It is important to use only marine grade plywood which lasts longer, is easier to paint and will not delaminate like lesser plywoods. Unfortunately it seems that neither apparent conformity with the British Standard (BS) 1088 nor the U.S. standard PS 1-95 guarantee perfect quality and expert advice is recom- mended. For one boat you will require: Plywood 1 Sheet 1220 x 2500mm 12mm plywood (7 ply) for the bottom, mast-thwart and midship frame. 1 Sheet 610 x 2500mm< 12mm plywood for the daggerboard case. There will be enough left over for a plywood daggerboard and rudder. A cutting guide is shown on the next page. 1 sheet 610 x 2500mm 3mm plywood (3 ply) for the hog and stringers. 1 Sheet 1220 x 2500mm 6mm plywood (5 ply) for the sides, transoms, mast- thwart bulkhead and corner pieces. If possible get an "offcut" of 18mm min. size 200 x 880 for the mast thwart (saves gluing 12mm and 6mm together). Note: Some saving may be achieved if more than one boat is built together.
Building the Wood/Epoxy Optimist - page 5
Building the Wood/Epoxy Optimist - page 6
What will they cost? The following prices are taken from the internet (search for "marine + ply- wood") and appear to be average current ex-warehouse retail prices (US$) from major suppliers: 1 Sheet 1220 x 2500mm 12mm plywood $100 1 Sheet 1220 x 2500mm 6mm plywood $60 1 Sheet 1220 x 1250mm 12mm plywood $50 1 Sheet 1220 x 1250mm 3mm plywood (or 4mm) $30 Timber for gunwales etc. $50 3 Litres Epoxy $90 Fittings* $170 TOTAL $550 Note: From 2004 the rudder and daggerboard may be max 15mm thick. If 15mm ply is available and funds allow this should be used. Inner Gunwales 6 pieces 2.4m 16mm x 35mm Clear timber for gunwales. Spruce or a light hardwood like mahogany makes for nice light gunwales which are easy to form to shape. Outer Gunwales 2 pieces 2.40m 20mm x 25mm. Hardwood like mahogany wears better than the softwoods. Framing 1 piece 16mm x150mm x 2.40m approx for both transoms Daggerboard Case Side members 2 pieces 27mm x50mm x 400mm Mast step 1 piece 100mm x 60mm x 180mm Glue Approximately three litres marine epoxy glue for laminating parts and coat- ing hull Hardware #8 x 3/4" screws. Normal steel since they will all be removed after gluing. The glued joint is stronger than the screws, so why carry around the extra weight. Fittings: 3 buoyancy bags, mast-step, rudder fittings, padded toestraps, fixing plates. Materials (continued)
Building the Wood/Epoxy Optimist - page 7
Not bad when you think that the lowest priced GRP Optimist hull will cost at least twice this! * Some of these may be available from local chandlers. If not, maybe your nearest GRP builder can help or try Optiparts in Holland who claim to be the "world's largest supplier of accessories for the Optimist dinghy". Tools Screwdriver Metric Tape Measure Jig Saw - preferably with tilting base Plane for final fitting of panels &amp; planing gunwales Electric sander Drill and #8 bits Clamps: you need about 10-15 each side when gluing the inner gunwales Straight edge and flexible batten for drawing curves
Building the Wood/Epoxy Optimist - page 8
Mould Construction Glue and screw the top panel onto the two profile guides about 150mm either side of the centre line. Fit a couple of transverse supports so that the bottom mould is quite rigid. If you make them so that they slot over the 2 profile To construct this mould using particle board you will need: - two "profile guides" running the full length of the boat. Take one sheet of the particle board and cut it into two 620 x 2440mm pieces. Using the official plans Sheet 03/10 mark the actual profile of the boat’s bottom on one of the sheets. Now scribe a line equal to the thickness of the mould material below this line and cut both sheets the same. - a mould top panel cut roughly to the shape of the bottom using the dimen- sions shown in the Expanded Bottom Panel Drawing in Appendix B1 but cut about 25mm narrower than the bottom of the boat. A mould is highly recommended to ensure that the boat will measure when complete. A simple bottom mould can be made from two sheets of 20mm particle board (chipboard) for about US$20 and it is reusable. This bottom mould will define the curve of the bottom of the boat and hold the bottom shape while laminating the bottom and attaching the sides and transoms. guides you can disassemble the mould for storage. Double check all of the dimensions on the mould since all boats that are made from it will be exactly the same shape as this mould.
Building the Wood/Epoxy Optimist - page 9
One of the advantages of using the 12mm bottom construction is that it is thick enough to screw the sides and transoms into. For this reason the bottom panel is cut to fit inside the sides and the transoms. Be careful when using the offi- cial plans because those plans show the sides outside the bottom. Also, since the official plans show the thickness of the bottom as 6mm, you need to add 6mm to the bottom of the bow and stern transoms. Construction Cut the daggerboard case (Plan sheet 07/10) out of 12mm ply. Use the alternate method of construction where the entire case extends through the bottom. (It's easier to do and it's stronger.) Note that the height of the case at the aft end is 293mm which, with a 12mm bottom and 3mm hog, gives the Measurement Form height of 308mm. Cut the sides as shown on the expanded drawing (Appendix B2). Put all lines on as shown, on the inside of the hull to facilitate assembly. Cut the midship frame (Plan sheet 08/10) out of 12mm plywood. In this case make the bottom 6mm shorter in height because the plans show 6mm bottom thickness and the bottom of your boat is 12mm. There is no bevel required on the midship frame. Mark the centrelines and all lines required. Cut large and plane down later when the framing is glued on. Use the plans to fit the top frames on the tran- soms. Cut the two temporary moulds (see Appendix A) to be located at the 500mm and 1500mm positions during construction. The first step is to cut the transoms out of 6mm plywood (See Plan sheets 05, 09 & 10/10). Use the official plans but remember add 6mm to the bottom to allow for the difference in construction described here. The plans show the amount of chamfer required and in both cases the smallest dimension of the transoms are shown. Cut the bottom as shown on the expanded drawing (Appendix B1), but adding about 5mm at the bow (to be trimmed off later). The dimensions have been adjusted to allow the bottom bevel of the sides to be cut at an equal angle of 8 degrees of bevel. This means the angle will be slightly too shallow near the bow but the epoxy glue will easily fill the joint.
Building the Wood/Epoxy Optimist - page 10
Cut and fit the doubling pieces (hog and stringers). It is recommended that you use the minimum dimensions stated in CR 3.2.4.2 (it is easy to add weight with epoxy, difficult to reduce it.). Glue them to the bottom panel by using a com- bination of clamps, weights and screws through the bottom. Use liberal amounts of epoxy since it is very important that they are securely attached to the bottom: they support the securing pads for the toe straps and mainsheet blocks and the mast step. It is recommended to dry fit (without glue) all the side panels and transoms to ensure that everything fits. Since the sides determine the curvature of the bot- tom screw the sides securely to the bottom panel. Draw the centerline and connect all the lines shown. If you are careful you can cut quite close to the line. Always clean up the saw cut with a sharp plane. The lines will be on the inside of the hull. Take note of the angles of the bottom cut at the bow and remember that the bow and stern transoms are fixed outside the ends of the bottom panel but inside the side panels. Fit the forward temporary mould to the panels. Remember to use wax paper so you can remove it later. Once all the glue is cured remove all the screws. The shell is now complete. Release about half of the screws from the aft end of the boat to the midship frame on both sides. Glue the joint and put the screws back in to hold while curing. Fit and glue the aft transom. Put the aft temporary mould in position but try not to get any glue on it. Use wax paper if necessary. Release the forward screws back to the midship frame on both sides and glue. Screw the panels and midship frame back together and fit the bow transom. Slip the transoms into place and plane the angles so that they fit. Epoxy glue is quite tolerant of gaps so perfection in fit up is not necessary. Check that the midship frame fits properly and then stand back at the transom and look down all the centrelines that you drew on the panels. They need to be perfectly lined up indicating that the boat is straight. Once you are certain the boat can be set straight, it's time to do some gluing.
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