Unsatisfied with commercial kitesurfing boards, I decided to make my own. I found the commercial boards to have too much rocker, too many fins, stupid graphics, and, worst of all, too high a price tag. With $50 worth of marine grade plywood you can build a board that will drop the jaws of all the board-shorts-on-the-outside-of-their-wetsuit types as you scream upwind.
Step 1: Design your board
I learned to kitesurf on a rectangular board, 16 x 60 inches. Nearly anything of this same approximate surface area will work. My current favorite board (which has lasted more than two years now) is a perfect oval 62 x 16 inches. The holes for the footstraps are set 1 inch forward of the centerline. My feet naturally sit about 22 inches apart, so I set the 7.5 inch wide footstraps 22 inches apart. I also put in a hole for a leash.
In this files section are two CAD files (DXF and Corel Draw) of my favorite board.
I printed my design out on a large format printer. You can also just draw your design my hand on a large sheet of paper.
Step 2: Cut board
Transfer your shape to marine plywood. I think 3/8 inch thick Baltic Birch is the best choice. Unfortunately, I've only been able to find it in 5 x 5 ft sections, so you can't make a board that's insanely long.
Rough cut the shape with a table saw or jig saw, and then smooth the edges with a belt sander. Round any sharp edges so the board doesn't cut you, but also so it's not prone to knicks and dents that will allow water through the epoxy.
Make sure you align the grain of the wood on the face of the plywood along the direction of the board.
Drill holes and install 1/4-20 tee-nuts for mounting footstraps and a leash attachment point.
Step 5: Lay Up Fiberglass