The Rot Doctor


Subject: Relative benefits of polyester resin versus epoxy.
Date: Sun, 11 Jan 2004

I am doing my homework to repair the rot in a 1930's vintage car. The body frame was made from ash, and some struts have rotted extensively. The best approach would be to remove the body skin and replace the ash with new wood. This would be prohibitively expensive. In the auto body repair business, polyester resins are very popular, and are frequently used with fiberglass cloth or mat for repairs. In the wood boat business, it appears that epoxy is the material of choice. Which is better, and why?

Thanks for the help.

Epoxies have definite performance advantages over polyester. They are stronger and bond much better to all surfaces including wood. To achieve a given strength, you can use less material with epoxy thus allowing a lighter weight for a given strength.

Epoxies are also more tolerant of flex. Polyesters are much more brittle when cured. Our epoxies are quite flexible when cured while maintaining the normal strength advantage of epoxies over polyesters.

Our epoxies also have a much longer pot life than both polyesters and most normal epoxies. We feel that this makes them much easier to work with.

The ONLY advantage that polyesters have is price. Polyesters are commonly used to build fiberglass boats because they are the cheapest product that will get the job done. To build an entire boat, the price difference is significant. When doing repairs, the cost factor is not as great, while getting a strong repair is a much more important consideration.

You are welcome, please let me know if you have any more questions.