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Fin boxes & foot strap inserts set into Divinycell


Where major bits are affixed to an EPS foam board, be they fin boxes, foot straps, mast bases, etc, such bits need to be anchored in such a way as to remain attached :) and do so without leaking. The hardware, or inserts, that are installed in the boards for this purpose are almost exclusively made from some reinforced plastic or another, inexpensive to manufacture to reasonably close tolerances. Only problem is that the Epoxy used to hold the board together does not bond to plastic well. Which is why manufacturers mold some sort of ridged tooth design into the perimeter of these inserts, in order to achieve a mechanical connection. With EPS foam having the holding power of a marshmellow (and that's an insult to the marshmellow), some sort of intermediate medium needs to be introduced. Enter Divinycell PVC foam, or high density Urethane foam. Surrounded by such structural foam, we can safely ignore the fact that the Epoxy still will not bond to the face of the insert, since it does securely bond to the closed-cell foam immediately adjacent.

Time and time again I find leaking and/or loose inserts to have been installed without the benefit of such cartridge of structural foam. Maybe, an insert destined to support a water bottle can safely be installed directly into the EPS. Maybe. But anything that will see bigger loads will need extra support!


This Maui Project board was blowing bubbles from about half its foot strap inserts
Removing the padz revealed definite movement of the inserts
A close-up shows that the fiberglass skin was detached from the top of the insert
Grinding down to the top of the inserts revealed that they were installed directly into the EPS foam, without a structural foam cartridge.

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