The Rot Doctor


Subject: (CPES and seam repair)
Date: Sat, 12 Aug 2000


The plot thickens!! It would appear that the person who refastened this boat left all of the old iron fasteners in place, picked out the wooden bungs, put new S/S screws alongside and filled both holes with 5200. In addition he apparently removed the cotton from most of the seams, again using liberal amounts of 5200 in the seams. In particular at the butt ends of the seams. The enclosed photo pretty much says it all.
My question is. Where I am finding wet wood , like along the butt seams ,and pulling out the 5200 in preparation for CPES , when some of the seam caulking (be it 5200, cotton, or both) comes out as shown in the photo, can I replace just the area that has pulled out or am I obligated to remove everything from the whole length of the seam and start from scratch?? I am of the belief that "it if ain't broke, don't fix it" and of course the easy repair would be to re cotton and caulk only where I have to. Does this sound like a reasonable approach to you?? David N.


Your approach makes absolute sense. Not even a professional caulker would suggest pulling caulking from good seams. Dry the wood, hit it with some CPES, and re-caulk.

We have done some testing with 5200, 4200, 101, Boatlife's polysulfide and the like and found that they all adhere extremely well to CPES-treated wood. Even if the CPES is still a bit tacky they stick like hell.

I myself still believe in a bit of caulking cotton -- when it's in there it's in there and one doesn't have to depend entirely on the adhesion of some mysterious chemistry to keep the water out.

5200 is good stuff, but not that flexible. I'd place it in the adhesive category rather than the caulking category. For people wanting to use new compounds to pay out their seams I'd suggest 4200...doesn't adhere quite as well but remains a lot more flexible. The key, as always, in getting these things to stick is clean, dry wood.

Thanks again for the good picture. They help so much.