The Rot Doctor


Subject: Rotted deck core (Balsa/Fiberglass)
Date: Thu, 13 Nov 2003

Doc- many thanks for the good and remarkably fast reply. You have a great site, and I'm VERY impressed with the customer service.

I had another question about repair of badly rotted and soaking wet deck core, which I believe is balsa, but so far it's impossible to tell. From reading your Q&A section, etc, I believe I understand the basic process and materials. I have a situation that's a little different and I'd like some advice about how to deal with it.

The rotted area begins around a 3" wide hole where a hawse pipe passed through the foredeck. The core is close to 1" thick, between the layers of fiberglass. My guess is that the rot extends some distance from the hole. I'm also guessing that I'll need to cut away the top layer of fiberglass and replace the core, but at what point would I know it was better to do that than to dig out wood, drill holes beyond that area, CPES™ it to death, then fill with epoxy where the wood used to be? Once it's dealt with, a shore power cable plug connection will be placed in the hole.

I'll be ordering some of your product as soon as I can figure out a schedule for this work, and I am most glad I was put on to you. Thanks.

Regards -


It's always a pity to have to cut away deck-surfacing, and I would try and avoid that if possible.

If the core is almost an inch thick, then it is probably balsa. Pull the hawse pipe and take a look. If it is balsa, I would start scraping out bad balsa with a hooked wire, or whatever. See how far back you can get, and then see if you begin to hit good balsa. If not, then instead of tearing off the deck drill some 3/8" (or larger) access holes to try and define the limit of the bad balsa.

Treat everything with CPES™ to stop the rotting process.

I would then pack-fill the area around the hawse pipe with either our Fill-It™ Epoxy Filler, or a custom filler mix made from mixing sawdust or talc with our Layup & Laminating Resin™. Push this mix as far as possible into the open area around the hawse pipe. Then, depending on what you are seeing through the drilled access holes, pump in either pure L&L Resin™ (if there is still balsa in there) or a soft mix of the L&L Resin™ and sawdust (or talc) to fill. This will all cure hard in about 24 hours, and then you can use the Fill-It™ Epoxy Filler to top off the access holes and spread smooth.

This process should work, and should save you having to tear away decking. We see little reason to replace with new balsa in on these kinds of limited-area repairs. The balsa will always remain vulnerable to rot, while the epoxy fill will be there when the rest of the boat is gone.

More questions? Then come on back!