The Rot Doctor


Subject: Transom Repair
Date: Mon, 20 Jan 2003

Greetings Doc!
Hope you had a pleasant holiday season. I wrote to you several months ago in reference to replacing the deck in our boat, followed your advice, and it came out perfect, all the way to matching the original color! Well, got another project to tackle now. The transom. I've removed all the rotten wood that I could get to, let it dry, now it's time to replace the wood, treat it, etc. I see the CPES product is the thing to use, but man, expensive! Is there an alternative? A guy at West Marine told me you can accomplish the same thing by mixing the fiberglass resin with paint thinner and get the same results. This is where you come into the picture. Can this be done? If so, what are the mixing ratios? If it cannot be done, as mentioned earlier, are there any other alternatives I can use? I trust your opinion and advice, and I want to do the job right the first time. I'll anxiously await your reply. Thanks!!! Kelly L.

CPES is a custom blended product, made by a chemist, with 14 different solvents in it, designed to do what you and I need it to do to rotted wood. It has been in production since the 1970s. As far as the guy at West Marine is concerned, I guess I have this to say. Is he a chemist? Has he been mixing resins and paint thinners since the 70s? Has he tested the resin/paint thinner mix?

To directly answer your questions, yes one can mix paint thinner with resins to get a thinner product. Will the results be the same? I honestly don't know, as I have not actually done this testing. And I am not likely to for a couple reasons. First, I would have to know as much about chemicals as a chemist in order to feel confident in duplicating CPES. Second, I feel that the cost difference is not worth the risk and trouble. In our two gallon units, CPES costs $74.73/gallon. West Marine is currently getting $65 for a gallon of West Systems epoxy resin. Throw in a quart of hardener for about $25, and enough paint thinner to make 2 gallons total, and the cost is about $100 for two gallons, or $50/gallon. So for $25/gallon more, you are getting the good stuff, made by a professional, that you are absolutely sure will get the job done. Yes, you could buy a cheaper epoxy resin and get the costs down a little more. But even if you save half the cost of the CPES, you are still dealing with a product that you and I aren't sure will work at all, much less as well as CPES. To do a transom, you might use 1/2 gallon of CPES or its equivalent. So for this, you are saving between $12 and $25, which just isn't as much as it used to be.

If the guy at West Marine is willing to risk the success of his job on a home brewed solution, let him. I would rather put my trust in a trained professional, and sleep well at night. For me, the potential reward is not worth the risk.

Hope this answers your questions. If not, let me know.


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