Repair of cored decks

From CSCWiki

All of the Pearson keelboat which CSC owns have balsa cored decks. After many years of heavy use these become delaminated. It can happen merely because of too much foot traffic or becasue water has gotten in due to a leaky fitting.

The structue is a thin inner layer of fiberglass, a layer of end-grain balsa which might be 1/2 inch or 3/4 inch thick, and an outer skin of fiberglass.

The repair is done by first constucting bracing under the inner skin so that it holds it shape. If the area is actually pushed in, it should be jacked up to match some estimate of the original lines of the boat. Use constuction quality lumber. Cut some cross pieces to match the curve and support them with braces, wedges, etc. It is better to put more in rather than less.

Next cut the other skin off in the damaged area. Save the outer skin for later use.

Scrap and chisel away bad wood until only the inner skin is left. Trace area which needs to be replaced and cut some new balsa or foam to match. Use thickened epoxy and paint the inner skin and the bottom side of the replacement wood. Fit new wood in and cover with a large sheet of plastic. Seal plastic with tape to keep out moisure. Weight down repaired area with lots of bricks so create a good bond between the new wood and old inner skin. Let that cure for three days.

Might want to brush the new wood with CPES afterwards and let that cure three days.

Create a new fiberglass layup using fiberglass cloth and polyester resin over the exposed wood.

Paint with gelcoat afterwards. Gelcoat will chemically bond to polyester, but will only create a mechanical bond with epoxy.