Tom -

when using foam that has been machine cut on saw, I will also seal with a thin coat of epoxy. I also layup my first layer of glass while the seal-coat is still tacky. If you hot-wire cut or form foam, the heat from the wire will seal the cut surface and priming with a seal coat of epoxy isn't needed. The heat from the wire when pulled through foam at an appropriate speed willl meelt the fooam and create an almost factory finish.

Three layers of 6 oz. cloth, a foam core, and another three layers just seems like overkill - unless whitewater and shooting rapids is final destination. For most lake, stream and flatwater touring, foam should be able to handle most flexing and minor rocks. I realize this ssite has a propencity toward wood - and to which I too lean - but foam is a well known and accepted core material for composite construction. If care is take to lay up the glass while tacky, and the epoxy is worked into - then out of the wweave with a squeegee to prevent glass float, the build up of two layers of 6 oz. should be more than sufficient. If in doubt - try 3 layers of 4 oz. Keep in mind, the lighter the weight cloth, the less epoxy that is needed to fill the weave.

Gougeon Brothers did some panel testing of their WEST System products. I don't recall if they ever did foam core though. Since balsa is uesed in end-grain as a core material, and it is much more pourous than foam, one could consider that product too. Check at Baltek (sp ??) web site.