All four views in the drawing are looking outwards at the port leeboard pivot area - above the front of the mid seat/tank.

The assembly process is shown in four steps:

Step 1: The 9 ply sheer doubler is slid into place in cut-outs in the top edge of the mid seat bulkheads. The top edge of the doubler is 15mm below the top edge of the side shell - this is level with the top of the mid seat bulkheads.

The seat stringer is added to the doubler. It is made from the same 15x15 softwood as the other seat stringers, but the top surface is heavily chamfered to match the angle of the side panels of the seat/tank tops. The top edge of the stringer is 66mm below the top edge of the doubler (ie, 81mm below the top edge of the side shell).

Once this work is done, the bulkheads are bonded in place inside the boat with epoxy fillets.

Step 2: The seat/tank tops are fitted and their joint to the side shell has epoxy fillets added.

The gunwhale is fitted by clamping it in place with an epoxy/microfibre 'glue' and screwing through from the inside.

The inwhale [US: sheer clamp] is fitted to the inside of the top edge of the side shell with an epoxy/microfibre 'glue' and screwed through into the gunwhale. The inwhale needs a rebate cut in it where it overlaps the top of the sheer doubler and it needs slots cut in its underside where it fits over the tops of both mid seat bulkheads.

Step 3: The doublers for the leeboard pivots are added to the inside of the sheer. I made these of two widths of the 35x15 mahogany stock I used for the gunwhale (the dotted line in the Step 3 view shows the join between the two widths). The rear doubler is 125mm long and completely fills the gap between the top of the seat/tank top and underside of the inwhale. The front doubler is 75mm long and 70mm deep.

Both doublers are fitted with an epoxy/microfibre 'glue' - if pinning these in place while the 'glue' sets, make sure the pins don't go where the leeboard pivot holes will be drilled. The backs of the doublers will need to be chamfered to fit over the epoxy fillets that hold the bulkheads to the side shell.

Only visible on the cross-section is the external leeboard pivot doubler. This is a 200mm length of the same 35x15 stock as the gunwhale, which is centred where the pivot holes will go, and fits directly under the gunwhale.

Step 4: Drill the three 12mm diameter leeboard pivot holes in the positions shown in the drawing. I found that only the centre hole was required - I put the other two in as insurance in case I had got the sail/leeboard balance wrong. You could drill just the centre hole and then drill either or both of the others if you find you need them.