epoxy over poly : can it be done?

[CornelP]

Hi guys, small question about polyester and epoxy resin.
I have a new hull, made in poly resin with stranded glass mat that I want to reinforce with some CFK. Can i use epoxy resin on it or should I stick with polyester?
The main reason to ask is that my poly resin turns out pink... it has a red hardener... does not look very good on CFK.

[BakedMopar]

IME yes. Epoxy sticks better to poly than poly over epoxy. I was also told that certain poly's don't bond to other poly's also. I have never used polyester resin so I can't vouch for that finding.

[Anbjorn]

Use coarse sand paper and wash of with acetone before laying the epoxi and you will have a strong bond.
Last time I did it was 15 minutes ago :-)
Anbjørn

[befu]

the polyester resin has a layer that does not cure fully, that is why it feels sticky or gums up sand paper.

You can either sand it off, or coat it with PVA mold release. The mold release will dry, seal it from the air and it will fully cure. Then wash the PVA off and use epoxy. Sanding the surface will help also as it gives the epoxy a rough surface to bond to.

Carbon fiber should always be used with a good laminating epoxy resin. It has a binder in it that works with epoxy for best results.

Brian

[CornelP]

Thank you guys, will keep you posted with the results. Never tried the PVA treatment but will do...