Sefuller, remember that the remaining layer of 'glass (under the core) is
not strong enough to support the needed loads if all you do is replace the foam with something equally non-structural, like blocks of foam (or something worse). Most people removing core from the top make this error. The only correct way to proceed from where you are is to grind back the top surface of whatever 'glass is left and bond your new layers to the existing.
Also I would not use epoxy for this-- it's too brittle, as you suggest. Using polyester or vinylester would be my first choice for this.
Forgive me if I sound like I'm talking downwards at you-- I don't mean to be. I've just seen this done wrong too many times!
For other people, I did discuss in my blog how to remedy soft or wet core without cutting away the vital upper layer of deck. My 'patented mooyock method' is really the
ONLY way to go when you are fixing this problem near deck-mounted mast steps and other bits of important hardware. Too many people cut out and install a block; but they're not thinking of laminate strength or block-to-core adhesion. And the very
worst thing is using some sort of filler, like a block of Starboard, that won't bond to anything at all, as though all that's needed is to take up space. Remember that, in the factory, the lower layer of 'glass, beneath the core, is laid-up when the deck is still in the mold, bottom-side-up, and they're relying on the upper layer (which goes in first, against the mold) of biaxial or triaxial for the real strength. On most production boats the lower layer is only about 2-3 payers of mat, sometimes even just cloth-- hardly enough to support your weight when it's in prime condition,
certainly not enough to be relied-upon to hold up a bunch of blocks and individual patches of core that aren't otherwise bonded to anything. So it all comes down to reapplying a really good, structural upper deck layer... because in effect you are rebuilding, not repairing, the boat.
