Racing Boat Seat Plans Construction Notes
The "riser" and the "cleat" come from the same piece of wood.
Lay out the curve with batten, or trace a convenient curved object, or just sketch it. Precision is not especially important here, just draw a nice, smooth curve.
Before cutting out the cleat and riser, cut the 18-degree bevel on the opposite edge.
The bevel is cut and the cleat is sawn from the riser.
Some plywood bends more easily than others.
In the pictures of the completed seat shown lower on this page, the bottom is made of 1/4" yellow pine AC grade plywood, which bent quite easily.
I once made a seat bottom from two layers of 3mm okoume marine plywood, which is also very flexible. The resulting seat was very stiff and strong.
But 5mm or 6mm okoume are too stiff to make this bend without tremendously stressing (or breaking) the wood. Same with 5mm luan exterior plywood, shown in the photo.
For this luan seat bottom, I cut kerfs about 1/2-inch apart and to a depth not more than half the thickness of the plywood.
NOTE: If your boat will see some rough use (like racing) you may want to make your kerf-cut seat bottom in two layers, glued together with the kerfed surfaces facing each other.
The seat bottom, riser and cleat almost ready for assembly. The cleat still needs to be cut at a 13-degree angle on its forward face.
The bottom is fastened to the riser using several closely-spaced screws and glue.
Epoxy is always an excellent choice for most boatbuilding tasks. I also recommend Titebond III.
Here I'm using clamps to attach the cleat. Screws can also be used, and at least two screws should be used at the outer corners of the seat bottom.
If you have cut saw kerfs into the underside of your seat bottom, I recommend you strengthen it with a patch. Exact size is not critical.
The patch is also kerf-cut for easy bending.
NOTE: As mentioned above, two full layers of kerf-cut plywood would be recommended for boats that will see rough use.
The back can be made from just about any waterproof plywood at least 1/4" (5-6mm) thick. The seat back gets its strength from its attachement to a bulkhead or a cross-brace fitted to your boat for that purpose.
The back is attached to the cleat with screws and glue.
I also recommend a drain hole, about 1/2-inch in diameter, through the seat bottom at its lowest point just in front of the seat back (not seen in this photo, but shown on the plans).
Steel angles have been added to the riser, and bent somewhat so they lie flat on the boat's bottom, stringers or floorboards.
Another cleat is added near the top of the back. This is where the seat will be fastened to the bulkhead, or other suitable structure, on your boat.
Finish your seat with epoxy resin, varnish or paint.
On a recently built seat, I also added this additional support after the original seat cracked in particularly rough racing conditions.
Your seat will cradle you in a slightly reclining posture. It will also provide good support for your legs so that you do not end up putting too much of your weight on your coccyx (tailbone). Trust me, in a 20-lap race bouncing over the wakes of 8-10 boats, that's an important consideration.
If you must stand on the seat while entering or exiting your cockpit, try to place your foot directly over the riser. At least stay off the edges and corners.
