New polyester vs epoxy question

[kcautodoc]

First I'd like to say thanks for all the help I've received from this website.

That said, I can't find an answer to my latest question. I have a 17 ft 1965 Hydrodyne that I am rebuilding. I replaced the stringers, reinforced the hull and replaced the transom all using epoxy. Now, in the back of the boat I would like to build a half-round bench seat. Here is my question.

Can I build a seat out of fiberglass using polyester resin and use polyester resin to attach it to the epoxy floor of the boat?

I know that epoxy bonds to polyester much better than the opposite. But since this is not a structural part of the boat will it be okay?

Or, if I build the seats out of polyester and let them completely cure can I then use epoxy to attach them to the epoxy floor of the boat?

I have seen so many posts on not using poly over epoxy because the weaker bond. I do understand that. I am just wondering how weak the bond is. I would not consider doing major repairs with polyester (although I'm sure many do it). But for a non structural item that people will be holding down most of the time? The epoxy resin is just so much more expensive than the polyester that I would like to save a few dimes where I can.

Thanks,
Richard

[ondarvr]

Don't try to attach the Polyester seat to the epoxy floor with polyester resin, make the seat with polyester and then use epoxy to glass it in place.

Doing major repairs with polyester is fine, it's just like anything else, it needs to be done correctly. You have more room to not do as good of a job with epoxy and have the repair hold up.

On small boats most laminates can be done in a short period of time, so you get a good chemical bond. On large boats and Yachts most laminates have cured for long periods of time before the next layup is applied, all of these secondary bonds are done on well sanded surfaces and there are few problems with them. This is no different than doing a major repair at a later date.

[mydauphin]

Originally Posted by ondarvr

Don't try to attach the Polyester seat to the epoxy floor with polyester resin, make the seat with polyester and then use epoxy to glass it in place.

Doing major repairs with polyester is fine, it's just like anything else, it needs to be done correctly. You have more room to not do as good of a job with epoxy and have the repair hold up.

On small boats most laminates can be done in a short period of time, so you get a good chemical bond. On large boats and Yachts most laminates have cured for long periods of time before the next layup is applied, all of these secondary bonds are done on well sanded surfaces and there are few problems with them. This is no different than doing a major repair at a later date.

I would add... I make interior parts ( I have also done whole boats) out of Polyester and get shapes right. then I coat all of it with epoxy then glue it with epoxy. So polyester becomes the core of the epoxy. Polyester is a little more brittle, or hard.. the Epoxy more flexible and stronger. It makes a real good combination. LIke Concrete with rebar, they work better together than separetly.