I am rebuilding the rudder on my 1980 Gib'Sea 40. I pulled the rudder of last fall and cut out one side with a skil saw. The foam was completed degraded however almost everything else was in good shape even the wooden stringers that create the rudders form. Once everything was cleaned out, I epoxied the interior and poured epoxy into hard to reach crevices and let it harden. Tomorrow, I am filling the cavity with a two part liquid foam. Once the foam has hardened I will reinsert the cut out side panel and reform the exterior with a silica/epoxy mixture. Once faired I plan to cover the entire ruudder with another layer of fiberglass. Its not a difficuly job , just takes a little time.