Originally Posted by miatapaul
Yes, some people will drill holes and inject epoxy into the holes to stiffen up the deck. It is a bit of a hack, but works for some. The biggest issue (as most of these boats it is either a quick fix or it faces a battle with a chain saw) is that if it does not work you now have two pieces of fiberglass with a mixture of rotted wood, and hardened epoxy that is basically impossible to separate and clean up. I have seen some that have used a grease gun to force out the water and force in the epoxy after they screw zirk fittings into the holes.
I've also heard of that injecting epoxy into rotten wood method but I really don't like that approach!
I would drill holes strictly to map out the extent of the water saturation and help dry it out.
I'm thinking of using Last-a-foam, it would allow me to start and stop work at almost any stage in the project without leaving a breach in the deck that would absorb even more water.
The little bit of the core I saw on our Grampian 28 seems to be about 1/4 inch thick, but I don't know if it is that thickness everywhere.