Fiberglassing

monkeymikey2000 · Post by **monkeymikey2000** » Tue Mar 27, 2007 7:36 am

I've been doing some fiberglassing on my boat and learned after the fact that when applying more than 1 coat of resin and cloth you must use unwaxed resin for the initial layups then waxed resin for the last layup so the surface will dry. I did 3 layups with all waxed resin and each layup had fully cured before the next, I also did not sand in between, maybe another mistake? Does anyone think I will have problems with what I've done in strength or long lasting? Thanks.
Mike

bcooke · Post by **bcooke** » Tue Mar 27, 2007 10:23 am

I would say it certainly depends on what you were glassing. Is this a major structural repair or some cosmetic filling?

It sounds like you are using a polyester resin which uses a wax to seal the surface from air allowing it to cure properly. I think you would be well ahead of the game to use an epoxy resin rather than the polyester. It has been discussed here on the forum a few times in the past but basically polyester resin does not bond well to existing material or fully cured resin. Other people here on the forum can explain the differences more eloquently than I so I will leave it to them.

Epoxy might cost a little bit more but it is far superior (IMHO) for repairs. I don't even bother with the other stuff any more.

-Britton

Hirilondë · Post by **Hirilondë** » Tue Mar 27, 2007 6:27 pm

To answer your question at all accurately, like Britton has mentioned more info is needed.

What type of resin?
What is the application/project?
What material if any are you bonding to?

Virtually all resins are best built up before full cure and can even be done fully wet to achieve a chemical bond instead of a mechanical one. All layered build ups when done after cure should be scuffed up (sanded or at least Scotch Brite) and cleaned between layers. These are just some generalities though.

monkeymikey2000 · Post by **monkeymikey2000** » Wed Mar 28, 2007 12:02 am

Yeah, I used polyester resin as I didn't know which was better. The guy at the plastic place said just use polyester. The project is an outboard well that I built on my boat as I took the inboard out. I built it with strong wood and stainless screws, aside from some tabbing most of the fiberglassing is not for strength just waterproofing. anyway it's too late now! I'll send some pictures of it when done so you can give me your thoughts. Thanks.
Mike

stone · Post by **stone** » Fri Mar 30, 2007 4:57 pm

I always buy polyester unwaxed. You can always add wax to the mix for sanding/finishing coat if needed. I would think it would be pretty obvious if something was wrong.