I have done many repairs of this type. Pumping epoxy in is not the best repair. It is a good stop gap measure until a complete and proper repair can be made. There are several issues that need to be dealt with such as: Killing all of the rot spores present (if balsa or plywood)to prevent the rot from spreading, complete drying before injection, not causing more delamination by using too much pressure in an attempt to completely fill any voids., increased weight, and decreased strength.Call me stupid if I have missed something. How bad is this rotted/wet core? Could you possibly use the West System and saturated the area with epoxy pumped in under pressure. At my marina in Queensland there is a CT 41 that has had this procedure done and and it turned out very good and solid.
Heck Trevor just cut the top off, take it home and make a new one with the fittings you need where you need them, then tab and glass it back on and non-skid the whole thing.
Custom boat with a solid deck to walk on, lighter than the original.
This is very good advice.Well - you sound like you and your posse are ready to take on a big project so I'll wish you well. A couple of suggestions...
Don't pull the entire underside ot the deck off at one time. The boat will flex and you'll be epoxying a few bends and twists into the hull that shouldn't be there. Do it a small section at a time.
This is more work, but probably a better choice in the long run.Think about using an alternate method. Cut 2 1/2 inch longitudinal channels out of the existing underside. Lay in a 3/4" stringer (wood/foam/carbon fibre/whatever) and then cover the stringer with several layers of roving. Once you have a complete structure of stringers, finish it off with some trnasverese ribbing done the same way. Then core between the stringers - use Airex. Cover everything with a bit of roving.
Make the sections where the hardware comes through the deck solid glass that is tapered to meet the cored areas so you don't get a hard transition line if you can avoid it. Solid glass is a much better solution than pads of plywood, since the plywood can rot.Remember NOT to use balsa in areas where hardware will pierce the deck. It is not strong enough from a compression standpoint. Use plywood. Make epoxy plugs on each hole.