This drawing shows the five seat/tank tops required to close off the buoyancy tanks. Where these panels meet the bulkheads forming the ends of the tanks, they are cut 10mm long (the dimensions shown include these 10mm lengths). When the seat/tank tops are fitted during final assembly of the hull, they can be marked from the bulkheads and cut to size.

The aft seat/tank top contains a cut-out on its aft edge for the third (inner) layer of the stern transom. If you have altered the width of this layer (eg, if the outboard motor pad is omitted), the size of the cut-out needs to be changed to suit.

The mid seat/tank top is a rectangle with identical cut-outs on all four corners - these allow the outboard edges of the seat/tank top to fit between the two bulkheads of the tank.

Two side parts are required for the mid seat/tank. The underside of these pieces will be chamfered, to approximately fit the centre part and the side shell, during final assembly of the hull.

The bow seat/tank top has a hole to fit over the mast step. It is sensible to cut this hole 5mm smaller all round than the exact dimensions shown and to open the hole out to fit the mast step during final assembly.

Half-breadth measurements at intermediate positions (one for the stern seat/tank top and two for the bow seat/tank top) are provided for the stern and bow seat/tank tops. These allow the curve of the side shell to be drawn on the parts. Mark the three or four points defining the curves on the pieces of ply and bend a batten to fit through all the points - a piece of the 15x15 seat bearer material is ideal for this purpose, but pick a piece that it is fairly straight (not warped) to start with.

All the seat/tank tops may require some corners to be rounded off during final assembly, to allow the panels to fit the vertical fillets that will have been applied between, for example, the side shell and transom.