: This may be considered heresy but has anyone used vinyl ester instead of
: epoxy?

It has been discussed a few times. It is not as widely distributed so probably fewer pople have played with it. Of the three "common" resins used with fiberglass, it is probably the least common. It costs about as much as epoxy, so there is no price advantage, unlike polyester, which can be found for considerably less.

Handling wise it is similar to polyester. Like polyester resin it cures by adding small quantities of an accelerant or catalyst. At room temperature you would use under an ounce of catalyst for a gallon of resin, so careful measuring is important.

I can't find any references to this material soakin into the wood pores and sealing the wood as epoxy resins do, so I am inclinded to think that this has the same characteristics as polyester. That is, it is probably slightly permeable to water vapor, so it does not prevent rot.

I believe the same catalyst can be used for either polyester or vinylester resins. You have some control over the potlife and cure times of these resins by adjusting the amount of the catalyst added. On hot days you can slow down the process by using less, and on cold days you can speed up the reaction by using more -- all within certain limits, of course. The resins are a bit "thicker" than epoxy so they create fewer runs and take a bit longer to wet out the cloth.

Fibreglast (www.fibreglast.com) has this for $52.95 a gallon, and it has a short shelf life. Polyester resin from these people is $37 to $38 a gallon by comparison. Here is their description of the material:

General Purpose Vinyl Ester Resin
Tough and Corrosion Resistant
This vinyl ester resin is formulated for maximum corrosion resistance to most fuels, vapors, and both acidic and basic chemicals. It is also heat resistant and blended for toughness. These qualities make it perfect for repairing tank linings, blistering boat hulls, as well as fabricating tough all-around parts. Catalyze with 1.25% MEKP, Shelf Life Limited to 3 months.

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Hope this helps

PGJ