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Poida said..
can someone tell me if the eps foam sucks in or soaks up water once the outer shell is cracked? once the boards get a few years old the water entry seems to be an issue to me? if the water leak isn't stopped then the board starts getting heavier, or is this with the other types of foam.
Yup, EPS is made by expansed beads of Polystyrene, and the air needs to circulate in it to dry them during manufacturing. It is inherent to the EPS construction.
XPS foam (eXtruded) is closed cell and do not have this issue, but since the resin cannot penetrate it, it is harder to work with: the shaper needs to do some tricks to avoid delamination: puncture the foam, rough it, cut small ridges,...
PU (PolyUrethane) foam is also nearly waterproof, but much heavier.
This is why the PVC sandwich method is good: the shell is very hard to break. And if you get a crack, most probably it will be limited to the outer glass, the PVC acting then as a waterproof shield.
Another way is to use waterproof closed-cell foam on the rails, and light EPS on the rest of the board.