That's interesting and made me re-avaluate Bill's post about the micro fractures in the foam. May be he was referring to the top layer of foam remaining stuck to the outer shell and separating from the rest of the foam below it... Does not sound good and may be I need to indeed plan for a heavier layup or additinal stringers in the blades where there will be more foam area...

: 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....