Hey gang. I've been through the Kiteschool plyboard stuff and the Instructables build and now have a few sheets of plywood waiting in the garage for me. I'm wondering though, is there a minimum / maximum size I should be aiming for? It's a shame to waste the plywood by cutting out just under 5 feet leaving 3 feet crossgrain. Can a guy get on with a 48" board (121cm) or should I stick to the 140's which seem to be the concensus?

The dimensions are largely determined by your weight and the wind you'll be kiting in. 144 cm x 39 cm is a good, all-around size for most average weight people. If you're a beginner, I'd go longer and wider than that. If you want a lighter wind board, longer and wider still. If you're a light-weight and want a high wind board, you could go down a bit. But the real short boards, 115 cm and 120 cm, from what I can tell, aren't as popular anymore. You have to be pretty lit to use a board that small (or be pretty light).

I built a ply board, 9-ply 1/2" birch about 134x42 or so, with extra wide tips, and I put only 2 big 2.5" Rainbow fins on the heelside of each end. I also got out a belt sander and dug into the bottom to make a slight concave about 2 plys thick at the deepest. I tried this board once, hated it because it splashed water in my face, and it sat for months. Then I tried it again on a whim, and now it is my most used board, it is killer for upwind. I weigh 190 lbs and am able to stay upwind with a 12m Cabrinha Nitro in 11-13 mph wind, where people with normal boards are using 15m's. I think the wider tips help maintain your planing, as well as the large fins keeping you on track while you keep the board flatter and don't cut in, instead just steer more instead of cut, and it works awesome. Good luck with your project board...

If the kiteboard in my mind is the same as the kite board in your mind can you tell me roughly what the width at the board ends would be compared to the widest point in the middle. Meaning, if it's a 42cm wide board, ignoring any notion of rounded pretty corners, how wide is the board at the ends? Is there some sort of ratio?

I did a measure of my board...It is about 17 inches wide at the midpoint, and 11.5 at the ends...The center section is more straight than the ends, however the entire sides still have a curve throughout the length. I didn't use any kind of ratio, I just took my 132 LF Drop and stencilled on the plywood, and made it wider by a few inches, then I traced thinner tips and then cut and finished the wood. I also extended the ends by about .5 inch or so...I wanted it to fit inside my back seat laid flat... Otherwise the board works great for what I made it for...light conditions...