I've recently stumbled acroos these folks:

http://www.precisionboard.com/Mar/

who offer a High Density Polyurethane board, in various desities and
thicknesses. To quote fom the site... "Precision Marine Board is
ideally suited for components such as decks, stringers, transoms, fish
boxes, livewells, and all other areas that require a high strength,
light weight and high durability material."

I then consulted Hankinson (Fiberglass Boat Building for Amateurs) who
says that Urethane foams are too firable to be used as a structural
core material, recommending instead linear or cross-linked PVC (Airex)
or extruded polypropylene (Nida Core).

My immediate need is bulkheads, though I'll eventually get to decks.

So... what gives? Is the Precision Board - as a 'poly' urethane -
different from the urethane foams of yesterday? Is it, in fact
suitable for ..."decks, stringers and transoms..."?

Any insight would be appreciated.

Mike Worrall
Los Angeles