The Rot Doctor


Subject: Wooden lightning restoration Episode II
Date: Thu, 27 May 1999

Dear Doctor,

I have taken all the trim off of the lightning, and I have it in slings which facilitates close inspection.

The first surprise is that the outer keel is rotten, which is OK because it has to be removed to have access to the screws that connect the keel to the centerboard trunk logs. The inner keel seems solid, so far.

The second surprise is that I can see light through some of the joints in the planking. There does not seem to be any caulking in the joints. I am planning on turning the boat over, sanding the hull and then soaking it with the penetrating epoxy resin. If I do this will the planking expand to close the joints:

a.) when the wood is soaked with epoxy?


2.) when the boat is placed in the water?


III.) I have to caulk the seams to complete the restoration.

See below.

D.) I have a serious problem on my hands.

No, at least not by our standards. Keep in mind that we maintain and live on an 1889 tugboat. Seriously, you've got a very nice boat that with some careful attention will give you years of sailing pleasure.

Please write back with the right answer and any useful advice. In the meantime, I'll be removing the centerboard and sanding.


Wood expands and contracts as the moisture content of the environment that it is in changes. There is no practical way to keep the wood from moving. So the wood will move some, even if soaked with CPES. If the boat is trailered, and only in the water for day sailing, the CPES will greatly restrict the water's ability to soak into the wood during the time that the boat is in the water, thereby reducing the swelling and contracting of the wood. If none of the joints have any caulk, then the planks are probably intended to swell and seal. If you soak the hull with CPES, and then only day sail, then the planks will probably not swell fast enough the seal the hull properly.

"Yeah, that's great," you say, "but what do I do with my boat?"

Turn it over, fix your rot, and sand the hull. Keep the sun from shining on it directly if at all possible. Clean the open seams down to bare wood. Make sure the wood is reasonably dry and soak with the CPES. After the CPES has cured, caulk the open seams with 3M 4200 seam compound. Finish the exterior of the hull with the quality paint of your choice, and go sailing. If the wood swells much, the 4200 seam compound may bulge out a little. If you don't like the look, you can shave the bulge down and re-paint that area. Most of the Lightnings we've been around are plywood. Is your's planked, or ply?

Please get back to me if I've been unclear on anything, or when you have further questions.