thompsondockside.com

I have a 1967 21' Thompson Offshore Camper. My Thompson is Plywood Lapstrake / Rib construction. I filled the inside (Just up to floor board) with water to start swelling before I launched her. The boat leaked a good amount at the keel. More than swelling could probably stop. Not in a place to restore the keel as I should. As a temporary fix, I was going to sand to bare wood along the keel and garboard(??) and was going to caulk, but.... someone said I should swell the boat for 5 days first and then Caulk. This way it would not swell and push the caulk out of the seam. Concerned that since the wood is wet or not completly dry, I wouldn't get good adhesion?? Is it worth swelling on a plywood construction boat first? Or should I just go ahead and caulk while it is dry? Or could you recommend a caulk/adhesive that would adhere to a wet surface? Thanks for the guidance!

Don't beleive the myth that you have to swell a lapstarke boat. You have a plywood hull. Plywood does not swell and shrink much at all.

You most likely have no caulk under the keel between the garboards. So that it most likely the leak location(s).

You can caulk from the outside of the wood as a temporary fix at the keel/garboard junction. The caulk will not stick to paint very well and it surely will not stick to wet wood. The boat needs to be dry.

Don't use 3M5200 or 4200 for this temporary fix. It will be a beast to remove when you do the proper repair. Use something like BoatLife Life Caulk

Andreas

Thanks Andreas! Figured as much. Trying to figure out how to drop the keel cap to fix underneath. Cannot flip a boat that size and really do not have a location to do that. Any suggestions on how to support the hull so I can remove the keel cap? Have read on the site that the Ribs cannot support the whole boat. Do not want to do more harm than good. Appreciate the advice!

Hey Chris, here's my experience with this same issue.

First, Andreas is dead on. Our plywood hulls expand/contract very little, which is a distinct advantage over a traditional planked hull. We can pull our boats out of the shed in spring, drop them in, and go boating, unlike most solid wood planked hulls.

When I bought my boat, the seams along the outer keel (aka the keel cap) were open. There was old caulk in place as well as some poorly applied filler. It leaked badly. The boat would have been gone in the morning if I left it at dock over night. I didn’t have the experience or resources to remove the keel cap and repair it the best way, so I went with a temporary fix. Temporary in that I plan to flip and strip the entire hull at some point.

I put the boat on home made stands, leaving the stem & keel areas fully assessable. Sanded away all the paint on the outer keel and stem and the adjoining areas on the garboard panels. I pulled all the old caulk out and cleaned the joints out completely of any lose material, dirt, etc. I did use 3M4200, caulking the full length of the outer stem and keel, and as well seems along each strake below the water line, plus one. Repainted. I also caulked the seam where the garboard panels meet the transom, a very thin line indeed, but I took my time on it and did a neat job. The other 5% was an issue at the junction of the outer stem and outer keel which required more work, but I'll leave that for later. This solved 95% of my leakage. The fix has been good for three seasons now, no issues, and I’ve had her out in some significant wake and wave.

I did a lot of other work on the bottom and bilge at this same time, repairing popped plugs and bad fixes by the previous owner’s repair man.

I supported my 20' Seacamper by blocking under transom and hanging from the lifting ring. I used a safety jack under center but removed that for keel replacement.



Remake your keel, its just a piece of wood, you can make it just a little wider so you get a better bite on the bottom sheet. Use ne Silcon Bronze hardware or stainless. make sure you bottom sheets are attached well to inner keel, chaulk well and reattach new outer keel.



Good Luck

Oh yeah, brag brag, my boat has been in a wet slip for a month and you can write your name in the dust in the bilge.

Hey Dan, what's under that sheet in the back ground og the last pic?

Peter, that was my Kawasaki Vulcan 800, sold it and got a 2008 1600 Nomad, very nice ride.

Very nice indeed. Got me a 2010 Harley Iron 883,......well, it's my wife's bike but I ride it....