I have a beautiful fiberglass ketch whose cabin house is soft and cracked and so are the surrounding decks. What can be done to rebuild the house?
Mark Matthews responds:
It's hard to be specific about large repairs without seeing them, but here are a few general guidelines regarding those kinds of fiberglass repairs. First, remove the damaged area by setting the blade of a circular saw deep enough so that it just cuts the damaged deck, but not so deep that it cuts through the coring or the bottom skin. If you've got a solid fiberglass cabin house, then you'll probably have to resort to using a grinder. In either case, it's important to try and remove the damaged area and keep it intact for reuse later.
After you've removed the top skin, grind the underside of it lightly. If the damage is severe enough, or has been allowed to linger long enough, it's likely that the old core will need replacing, so you'll have to epoxy in some new coring material like Airex or Nomex foam, or even a marine grade plywood if you're not too choosy about weight. Do that by saturating two layers of mat and applying one to the bottom of the new core material and the other to the bottom skin. Then bond the new core in place, saturate it with resin, and then cover it with the original skin that you saved aside. To ensure that you get a good bond, you'll need to apply weight on top of it as the resin kicks off and then cures, and you can do that by using wax paper to separate the weight (a discarded battery, or dumb bells, etc.).
Now, that's just the basic structural fix. You still don't have a presentable repair, so to end up with an aesthetically acceptable fix, I'd recommend that you consult Don Casey's book This Old Boat, which you can find in the SailNet Store. This book is invaluable for sailboat owners who are inclined to do a good bit of the maintenance and repairs on their own boats. And I think you'll find that the book will pay for itself in saved headaches and heartaches. You might also want to check out some other articles on SailNet that cover this same topic, in particular Tom Wood's piece on Repairing Fiberglass Decks. Good luck to you.