GBR82 Designed and built by Nicholas Cook.
Scroll down and enjoy the process.
Step 3 − Keep planking until each side meets in middle of transom, then trap plank ends under a wood clamp. The ends of each strip are shaped to fit together in a herring-bone pattern.
Step 6 − The hole for the rudder tube is cut using a hole-saw and the rudder post positioned.
Step 2 − Pin keel batten to tops of formers from bow to rudder post and plane to the correct angle for each former. Then start to plank up the hull from the shearline. The strips have the concave curved edge uppermost and a bead of epoxy is run along this using a 10ml syringe.
Step 28 − Now the hull has enough inherent stiffness to be put on its launching trolly.
Step 29 − The deck is planked over the curved deck beams using a polyethylene sheet to prevent adhesion to the hull.
Step 30 − The top surface of the deck is faired and cut around the shearline using a router. The top surface of the deck is sheathed like the hull, then lifted off, turned upside down and sheathed inside with biaxial glass cloth.
Step 31 − Now comes a very busy time. Before the deck is finally fixed down, as much as possible of the controls need to be planned and installed. The rudder tube, bottom support flange and top support beam are installed. The permanent buoyancy is installed. The steering pedals and mast foot are installed. The stay tensioning system is installed. The main control panel is installed. The mast is stepped, the boat is sat in, ropes pulled, cleats adjusted, etcetera, until everything is just right. Once the deck is on, it is permanently on and many components are difficult or impossible to adjust later.
Step 32 − Finally the deck is fixed down. A router is run around the shearline to cut a 12mm by 12mm recess into which a hardwood quarter-round moulding is glued to give a neat gunwale. Access hatches are cut in the bow and over the rudder tube in the stern, and also the cockpit hole, all using a router and suitable jigs.
Step 33 − By using a small-diameter cutter for the rear hatch, the material cut out can be given a laminated edge and used as the hatch cover.
Step 34 − The cockpit edge is similarly laminated.
Step 35 − Now the boat is complete, except that there are hollows at the stern that do not meet class rules. This error stems from misunderstanding the definition of the term “hollows” which should have been confirmed and eliminated at the design stage. This mistake means some extra work.
Step 36 − To minimise the amount of filling required, the angle of the stern overhang was increased by cutting a new flat panel. The stretched strings are indicators for the length and depth of filling required.
Step 37 − Strips of high density polyurethane modelling foam were epoxied to the hull and faired with a slightly curved long-board to give an indisputably legal shape.
Step 38 − The re-faired shape was sheathed with fine woven glass cloth to give the same finish as the keel.
Step 39 − A final long-boarding to a fair surface, removing much of the protective layers of epoxy, again takes time and patience. This is followed by application of a two-part varnish.
Partly because I have a friend who is an experienced pattern maker and partly because I wanted to get a good tight fit of the ballast leads in the keel, I opted to make a pair of aluminium moulds to cast split leads.
Because I contructed the keel from an inside blank, the inside is smooth and parallel. I gave the keel template to the pattern maker to make a pair of wooden patterns for casting into alumimium moulds. The patternmaker has to judge the contraction of the lead when it cools in the aluminium mould and the contraction of the aluminium when the mould is cast from the wooden pattern.
Two photos of the moulds are attached. The split is made diagonally through the centre of gravity and the widest part of the keel, so that both halves are each shorter and less wide than the space in the keel. This makes each half lead easy to lower in place and the two halves come snugly together only at the last moment. One photo shows how the two fit together, with the rear half inverted. The rear half must be cast upside down because of the rake angle of the keel. Each half is drilled and tapped M8 at its centre of gravity to take a stainless steel bolt. The lead does not stick to the aluminium or the stainless bolt, so casting leaves a threaded hole through the lead.
Casting the aluminium moulds cost £50 each. Each lead piece weighs 20kg and cost £1,10 per kilo to cast. Scrap lead costs £0,75 per kilo in the UK. The bottom pair of leads only needed running around the bottom edge with a 10mm radius router cutter to make them sit down on the base of the keel.
Step 40 − Now launch and sail your 2.4mR.