The Rot Doctor


Subject: C.W. Lapworth (wooden boat)
Date: Tue, 21 Jul 1998

I just perused your E-Zine, pretty cool. I live on a nice fiberglass sailboat and enjoy weekends sailing San Francisco Bay. A neighbor of mine owned a 1957 Lapworth 36 hull #10, a very classic sailboat. Due to personal reasons he gave the boat to me. I love it. Anyway to get to it. The boat was made right before everything went plastic. It is basically a CAL 36 made of wood. It is edge nailed and glued and does not depend on ribbing or stringers for hull strength. The problem is that it is bonded, that is every bronze and metal thing on the boat is connected electrically then the boat was over zinc'd. What has happened is not so much rot as "burnning". Some of the floor joists where the keel bolts come through are as you describe "punky" but not organically rotten from mold or mildew, it's like the minerals have been electrically removed from the wood. Now these floor joists or ribs have the keel bolts going through them. Their purpose is to transfer the load to the hull. They are about 4 inches wide and 10 inches deep at the keel and about 3 feet long. This "wooden" electrolysis is right at the keel and goes up no more than 2 inches and across no more than 10 inches. So you can see this is in a limited area.
My question to you good "Doktor" is what and how if you could use your products.

Thanks in advance. . . .


Hmmm.... interesting problem. Wonder why all the bonding/zincing on a wooden boat...? A wooden Cal 36 is interesting...first I've heard of one.

Anyway, assuming that you can get the wood reasonably dry your problem is fairly easily solved. You simply saturate the punky areas with Clear Penetrating Epoxy Sealer (CPES). The wood will absorb it, the carrier solvents will evaporate away and the wood will be hard again. It will penetrate right up against the bolts, and anywhere else it finds a vacancy. Mixed it's like diesel fuel and creeps into small spaces, like the area between wood fibers.

I would suggest getting a long 1/4" drill bit and drilling vertical access holes into which you inject the CPES. You can also watch the product of the drilling and get some idea of what the wood is looking like. Apply all the CPES the wood will accept. Give it a week to cure out, and then do it again. Following this drip our Layup & Laminating Resin into the holes to fill.

The critical part of this is making sure the wood is reasonably dry. Epoxies will displace water to some extent, but the dryer the better. It would be worth hauling the boat to dry out if required, considering the crucial nature of the repairs. You could also pull all the keel bolts and saturate that way, which is probably what the shipwrights would recommend, but I don't think it is absolutely necessary.

(Note: saturating the area with the keelbolts in place will effectivly glue the bolts to the wood, making future removal harder)

We have saturated a lot of wood with CPES, and it does get hard and tough. We have also saturated around fastenings, and seen no sign of their failure.

Come back if you have more questions. I'm interested in your project. We lived aboard a 42' Alden at Redwood City Marina, which is just South of Pete's. Long ago....