> What about using the insulation board foam to build a plug. Cutting out
> the cockpit and then glassing it in. This would isolate the foam from
> water damage.

You might want to check through the archives of the kayak BBS, or write an e-mail to George Roberts for the details/plans of the whitewater kayaks he builds. I believe they are just a bit bigger than that. I think this is a pretty small boat. I have forms for a wood strip canoe that is 10.5 feet long and about 26 inches wide. It is designed for a paddler up to 175 pounds in moderate weather. Sure you want to go that small?

As for building with the insulation board: If you draw your plans on a computer and use the machine to produce pictures of the hull at 1 inch increments, you can work from these plans to get the rough shape rather quickly. You just layout your lines on the 1 inch thick building panels with a ballpoint pen and a long strip of flexible wood strip. Cut along the lines with an electric kitchen knife, bandsaw, or a hobby /craft store hot-wire cutter. Stack these with a bit of construction adhesive and wait for the tuff to harden. A belt sander will knock those edges off in a very short time, rounding the hull to shape. In fact, the belt sander may be overkill. A surform tool should work, so should a sheet of coarse sandpaper thumbtacked to the enter of a 2 foot long section of 2 x 4.

The stuff is flexible (very) so building on a sturdy base is important.

For a 12 inch high boat you should be able to get by with 6 panels. If you start by ripping a few down the center to give you 24 inch wide by 8 foot long panels, you will be able to see how those 6 can turn into a 12 inch thick stack, but there will be a lot of waste. For less waste, DON'T rip the panels. Layout the fattest and the thinnest pieces on one panel and cut them out. The waste will be two 'V' shaped pieces that can be joined at the center to produce a diamond shaped piece from which you can cut a third canoe section. You might get by with only 4 panels for a 12 inch thick boat this way.

Buy a panel and test it with the epoxy you plan to use. If the bond is bad, or the resin dissolves the panels, you don't want to get too deep into the project with these materials. People who want to experiment with materials and designs generally have good results with building models and then scaling them up. If you get some 1/4 inch thick foam or plywood you can cobble together a 1:4 scale model that will be 2 feet long and probably 3 inches thick, and about 7 inches wide. A single sheet of lauan plywood goes for under $8 near me, and should be more than enough for making 4 of these models. After you get the design you like on the model, you take it apart and it is solid enough to take very accurate measurements from. Of course you just multiply the measurements by 4 to get what you need for the 8 footer. You can use the models to check your displacement. Since the bot is foam, and th skin is just fiberglass, I would guess that you would need to make the glass layup as thick and heavy as a conventional solid fiberglass canoe. That foam is not structurally strong. Estimate the materials for a solid fiberglass boat in that length and price them before you go too far into this. Best of luck with this. Paul Jacobson