I've been using CPES for years now. One of the requirements stated by the manufacturer is that ALL crumbly wood must be removed for CPES to be effective. Second, CPES is NOT, repeat NOT, an adhesive epoxy. This sounds a bit weird because epoxy by its nature is an adhesive. But CPES will not do the same job as a thicker epoxy or one mixed with glass fibers or whatever.
I learned this myself when I decided to overhaul our teak shower grate on which the original adhesive in all the joints had long since failed. Stepping on it produced a chorus of squeaks and squeals as the grate flexxed. Let this go on long enough and I knew eventually something would break. On the advice of someone who turned out was wrong, I disassembled the grate and then reassembled it using CPES on all the joints. Several coats of it. When it had cured, I could take the joints apart again by hand. So I did it all again using "regular" epoxy, and today some ten years later the grate gives not a peep when someone steps on it.
CPES was created for one purpose and one purpose only. To seal the upper cells of raw wood against moisture intrusion. This is why it is so thin. It penetrates farther into the wood (the manufacturer claims) than any other type of epoxy. The principle behind it is very simple. It penetrates the wood cells, fills them, and then cures. The end result is a thin, moisture-impenetrable "shell" around the wood.
That's all it does.
So the requirements for using it are bare wood--- CPES is useless over wood with any sort of a finish on it including oil--- solid wood (by which I mean not crumbly), and absolutely, 100 percent dry wood. I have used it as a component of repairing rotting wood in our aft hatches and one of our window frames. As a COMPONENT of repairing them. Applying it was not the sum total of the repair.
First step is to dry the wood totally. And I mean totally. In the case of our wooden aft hatches it took a month of them sitting in our heated bathroom at home for the wood to thoroughly dry out. Second step was to remove all traces of finish-- paint and primer in this case--- from the underside of the hatches. Third step is to remove all the crumbly wood. All of it, every bit. In our case what was rotting was the plywood top of the hatch. The frames themselves were fine as was the teak planking on top of them. But removing the crumbly sections of plywood resulted in depressions that penetrated several plys into the wood. Fourth step was to saturate the plywood with CPES. Several times. Fifth step was to fill the depressions with a filler. I use "Fill It" which is a carve-able, shape-able, sand-able filler made by the same folks who make CPES but there are other products that would work as well. Sixth step was to sand the filler flush. Seventh step was to paint the plywood and filled areas with CPES again. Last step was to paint and prime the undersides of the hatches.
CPES will penetrate into wet wood and, being an epoxy, it will cure. But it will not provide the solidity one is after, nor will it properly provide a moisture barrier if the wood it is applied to is wet or even damp.
So far as I know--- and I'm just repeating what I have heard from shipwrights with a lot of experience repairing boats on the GB owners forum--- there is only one way to properly fix a deck with a rotting core and that is to cut out the rotting wood and replace it with new wood. Coating the new wood with CPES is a great idea and these guys all advocate that. But based on my experience with it and from everything I've read both from the manufacturer and from shipwrights and repair people who use it all the time, trying to use CPES to solidify damp, crumbly wood will not work if the goal is to retain any strength in the wood.
-- Edited by Marin on Thursday 23rd of February 2012 02:11:41 PM
