: I was looking at spraying styrofoam with rhino liner...

Have you tried using the rhino liner on a block of your foam? I'm not sure what solvents are used in the rhino liner. They could cause problems. Some foams are more likely to be dissolved by certain solvents than other foams. That's why you can use epoxy resin over styrofoam, but not apply polyester resin dierctly to styrofoam. If your tests show an initial tendency for the rhino liner to eat away your foam. try painting the foam with a latex paint first, then applying the rhino liner.

Cutting forms from particle board, OSB, or the cheapest grade of plywood is going to be about the same cost as making them from foam panels. Ripping strips from pine, spruce or fir (SPF) or other whitewood construction lumber is going to be your least expensive way to cover the forms. With an 8' 2x4 just under $3 you're talking about 9 to 10 wide strips for about 30 cents a strip. The initial strips will be 1.5 inches wide, which may be good for some areas of the boat, but resawing them to widths of just under 3/4" or"just under 1/2" will give you an easier job of stripping. Those 8' by 3/4" by 1/4" strips are going to cost about 15 cents each, or about 2 cents a running foot. If you need 1200 feet of strips, that's about $24. Find the wood at a better price, or cut your strips thinner (3/16ths) and your cost will drop even more.

After a very rough fairing, and without bothering to fill the gaps between the strips, the prototype can be "waterproofed" by coating the outside with glued-on paper and a couple coats of paint. You can use heavy wallpaper, or thin newsprint. Or wrap it with Saran Wrap, or use a piece of heatshrink plastic, tyvek, blue poly tarp, or 4 mil polyethylene. The last three can be stapled on. It will be a delicate covering, but will serve for a day or two of testing. Pinhole leaks can be accepted for this. Forget the deck for now. Install thwarts to maintain the hull shape and go paddle it.

Quick and (somewhat) dirty prototypes don't have to be expensive. If you like the design, reuse the forms and build with clear cedar strips. The prototype can be used for book cases. Just put in shelves where the forms were (or leave the original forms in) and cut the thing in the middle to get two pointy topped units. Very decorative !

Hope this helps.

PGJ