With the stipulation that all-epoxy would be better: Epoxy will stick fairly well to a polyester surface that has been completely cleaned and sanded. Most polyesters contain a wax additive to promote full curing. This wax raises to the surface and must be cleaned off before applying any other material.

Polyester is not as strong an adheasive as epoxy and it would not be good to try to bond new polyester resin to hardened epoxy.

Polyester is not as good a sealant as epoxy. It will slowly let water seep through. But if you seal the polyester with varnish or a coat of epoxy the problem will be minimized.

Again the result will not be as strong, durable and long lasting as an all epoxy layup. If you can afford the epoxy and are just being cheap, it is probably not worth it. However, if you really are close to your budget, substituting polyester should be OK. With appropriate care the boat will last years.

WEAR A RESPIRATOR whenever you work with these resins, but particularly polyester.

: Hello all: I am about to begin the glassing process. I have been to a local
: supplier to price out the epoxy. I was wondering, First, is it possible to
: glass the outside with epoxy utilizing it's strength and asthetic
: properties while using ployester resin on the inside? THis would prove to
: be a considerable cost saving. My concern is can galssed epoxy be joined
: to a glassed Ployester resin surface? Are they Chemically compatable? are
: the strength properties of Polyester resin compatable with epoxy? I know
: that is is alot to ask but I am guessing that others have had experience.
: I appreciate any input.

: Regards,

: John