Vinylester over epoxy... NO !!!

The truth hurts! A few guys responded to my previous post about esters over epoxy, thanks... you were right. I contacted Durotech about using their fairing primer over epoxy, since I had some in the shop. They said no problem as long as the surface is free of blush. So we sanded, washed , etc. They (Durotec) said that it would be better if we used their vinylester primer before the fairing primer went down then top again with primer. This way the material would be sandwiched , then topcoat with the finish. I've got news for you... the duotech is peeling off like crazy!!! Good thing we just did the upper half of the transom . I think we'll stick with epoxy and if anybody knows of an epoxy fairing compound that can be sprayed I would really appreciate it.
Thanks, Chris

 

Don't do it unless you really have to. But, if, for instance, you are repairing a Carroll-built boat, then what has worked for me in the past is to first post-cure the epoxy laminate thoroughly, sand it, apply a thin coat of high quality vinylester resin, then spray the polyester gelcoat, and then the regular wetsand, polish, and making it look like nothing ever happened.

Yoke.

 

I'd agree with the Duratec guys actually. There's no voodoo chemistry going on here, you're just trying to achieve a good mechanical bond of the fairing primer to the underlying material... whatever that happens to be.

I use the Duratec vinylester hi build primer frequently as my final fairing step (over epoxy). To minimize blush problems throughout the process I use a peelply during laminating, and the non-blushing West 207 hardener for fairing. Make sure the epoxy is well cured, washed, and coarsely sanded. You should have no problems.

I favour the Duratec product over the alternatives of polyurethane hi-build primers as there are no isocyanates involved plus its formulated for marine use. You end up sanding most of it off anyways (expensive dust!)

Phil

 

......speaking of Duratech--

..I find Duratech primer ,both the regular and vinyl-esther quite useful for a variety of applications,,but a # of times Ive seen polyeurethane topcoats have shown bonding issues,,,,so have learnt to go with a polyeurethane finishing primer on top of the duratech to enhance the bond.