Polyester resin over epoxy

[CJR]

Can polyester resin be applied over epoxy resin? I read on the Classicmako forum that it could not. Rightly or wrongly, I applied an unthickened coat of West epoxy over my coosa board transom, and I am now concerned about what I did.

[FELLOW-SHIP]

Ha CJR
It sounds like you are asking this question in two different ways first question is polyester over epoxy but then you talk about epoxy over coosa board. For the first part the answer is correct, that you should not put polyester OVER Epoxy although there are some exceptions with West Epoxy you Can put Gel Coat over it if you do some extra steps. As for epoxy over Coosa board why not??
FellowShip [img]/images/graemlins/confused.gif[/img]

[CJR]

Fellowship,

First, thanks for the response. Second , I guess I was unclear in my question so I will rephrase it. Can I apply 2415 stitch mat to my coosa board transom with polyester resin after having first applied a "barrier" coat of unthickened West epoxy to the cooosa board.The idea was to provide a good moisture barrier to the coosa.

[FELLOW-SHIP]

I would not do that. Once you go to epoxy you should NOT go back to polyester resin the problem is adhesion. Polyester does not have the same adhesion properties as does epoxy and could peal off. They do carry a product that will allow you to do what you are talking about but it is usually used when you are wanting to do a large patch in the outer gel coat I don’t think I would trust it for STRUCTURAL arrears like transoms. I used approx 12 gallons of west epoxy on my boat when I re did the whole thing and if I were you I would ONLY use epoxy for redoing a transom anyway. Might cost you a few $$ more but your boat is worth it anyway.
FellowShip [img]/images/graemlins/wink.gif[/img]