The Rot Doctor


Subject: Cored fiberglass deck repair
Date: Thu, 25 Mar 1999


I have a 1972 fiberglass sailboat that had a significant number of deck leaks. The balsa cored decks have been drying out for a couple of months since I removed all the deck hardware and hatch frames, and when I drill holes in the underside of the deck, the drill bit comes out dry. Some of these areas seem to have no coring material left (just empty space between the fiberglass deck and head liner). Most of these areas are fairly small (6" or so wide), but the length of some extend a ways, probably along the course that the seeping water took. I am considering injecting CPES resin as a fix. My main question has to do with the vertical cabin sides, however.

Remember, CPES is a VERY thin resin, about the consistency of diesel fuel, and will saturate the balsa core and make it highly resistant to further rot. But it will not fill. My suggestion here would be to apply the CPES, give it a week or so to cure out, and then go back with a mixture of our Layup & Laminating Resin (long pot life, slow curing so it will fill completely before setting) and micro-balloons or sawdust or glass fiber or whatever and, using a turkey baster, inject the thick epoxy fluid in behind the CPES. Now you have protection and you have a fill for the void. No more rot problems in that area.

The inner and outer fiberglass skins have separated on the sides of the cabin (I think the core material is plywood here). How can one effect repair on these vertical surfaces? Can resin be injected here and, if so, should you inject from the top down, or begin by injecting from the bottom? I read somewhere that injecting from the top can introduce air pockets. I'm particularly concerned about this, since the chainplates attach to the cabin sides.
Great site, by the way, and thanks in advance.


For the cabin sides, begin by injecting CPES from the top down. Drill into the wood if you are able. The CPES will flood the plywood, soak it, penetrate all vacant or rotted areas, return strength and strongly resist future rot. Again, allow at least a week for the carrier solvents to evaporate away and the epoxy to set, and then go back in with our pure Layup & Laminating Resin for a final fill. This is slow setting enough that air pockets should be no problem. I would perform this resin application in successive steps, maybe three. The L&L Resin has a 24 hr hard cure time so it can be done on successive days. Final full cure will take about a week.

If what I'm suggesting isn't clear, come back and I'll try and do better, or answer further questions.