: For years I built windsurfing boards using pink Foamula R for the
: core. I think it was the 150 not 250, slightly less dense. The
: boards came out as light as sandwich skin boards with expanded
: polystyrene foam cores, but if there was an injury, the foam,
: being closed cell, would not absorb water. They held up ok and
: had a slightly less rigid feel, lively but not dead. After a
: couple of hard seasons however there would be some areas that
: would start to delaminate. This didn't seem to happen with the
: extruded foams that are made for this, so I always wondered
: about the chemistry....Was there something in the Foamula foam
: that was responsible, or is that just the nature of the
: structural demands of the system? Was it chemical or just
: microfractures or shearing at the interface between the
: epoxy/glass skin and the one pound per cubic foot foam. A friend
: of mine recently built a beautiful camper insert for his pickup
: truck using this system as well. It's been road tested, and
: we're keeping our fingers crossed that he doesn't see
: delaminations starting....

Biggest problem is the density, or lack of it. Insulation foam needs to be very low density for maximum insulating valves (R) for a structural core it needs to be somewhat higher in density. Normal insulation foam is around 2 lb/ft. while the minimum for structural foams is around double that.

Bill H.