Had to reinforce the Tuttle box in an old Starboard Formula 161 so that it can take the loads of a windfoil.
I was intrigued by the laminates on the bottom, and wonder if anyone knows the exact layup of these boards.
Above the EPS, there appears to be:
1. yellow coloured foam -
is this PVC foam or expanding epoxy resin ?2. thin layer of carbon
3. brown coloured foam - PVC like Divinycell?
4. thicker layer of carbon
5. the white skin, which also appears to consist of three layers -
does anyone know what products are used for this skin ?The layup on this old Formula board also appears superior to my 2017 Starboard Phantom raceboard.

While considering what material to use for reinforcing the Tuttle box, I found this link comparing XPS and PVC foam.
www.trinardo.com/y.a.t-yetanothertrinadofoamcompare3I had some XPS and PVC in the shed so did my own comparison test.
The compression strength of the XPS foam appears to be about 20-30% of the PVC.
Therefore I suggest XPS foam is not suitable for high compression loads like foil box reinforcing.
