On Sun, 04 Nov 2007 12:10:43 -0500, HK wrote:

The only
materials I think suitable for the fiberglass "hull" are the various
cloths and resins, not foam or foam boards or fillers.

From the very beginning fiberglass boat builders have been using core
material in strategic places to add thickness and stiffness without
adding weight. Unsupported fiberglass by itself is not a particularly
good structural material. Wood was probably the first core material
and is still very popular. The trick is to properly protect it from
moisture and rot. If you take a look at well built offshore boats
like Bertram, Hatteras and Grand Banks you will find a lot of
structural wood. The secret is to use high quality material and
protect it well. Fiberglass combined with any type of core material
is a composite.