End-grain balsa is actually a better core material in many ways... PROVIDED IT STAYS DRY. It has higher sheer resistance and greater compressive strength than all of the foam based core materials. It is easier to work with, as the resins adhere to it very easily, which is not the case with some of the core foam materials. Also, it means that the repair will have the similar flex, stiffness and strength characteristics as the rest of the deck.
Balsa also has much better heat deformation characteristics... it doesn't really deform under any temperatures a boat would normally see. That isn't true of the foam core materials.
The foams are great materials, but unlike balsa, don't prevent the water from migrating. If you have a leak in a foam-cored laminate, it can often cause problems a long distance from the actual leak, which isn't the case with balsa. The ductile foams can absorb impact forces and as such are better than balsa for coring a hull, since they may absorb enough of the impact to prevent a total rupture of the laminate. The rigid foams are the least useful of the foam-core materials IMHO.
BTW, marine plywood is probably the worst of all the materials that were used for coring laminates. It is heavy, and it has the worst characteristics of both foams and end-grain balsa. It allows water to easily migrate long distances like foam, and it rots like balsa.
Reading these two paragraphs in your posting makes me wonder why you
didn't take the opportunity to replace the wet balsa with foam core -- you would not have to worry about wet core in the repaired areas again.
I just had a professional repair a wet section of my deck and he did exactly that.
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.
—Cpt. Mal Reynolds, Serenity (edited)
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