West system epoxy resin

O

OJ86

Promoted Users
I have some fiberglass work coming up here soon and I wanna try the West system Epoxy resin. These are just normal Fiberglass race car parts from VFN.

I've used the bondo brand resin and even with feathering out holes and such the correct way, they always seem to shrink in.

I just want to try something better to see if I can avoid this problem.

So looking at the road map on the West system site, I should just order the 105/205 combo?? These are just repairs that will be made with glass cloth/matt and will be bodyworked and painted over.

As usual any advice would be greatly appreciated.
 
west system will work fine. been using it for 20+ years. 105 and the 205 cat is all you need. get the measured pump kit for the cans. makes life alot easier. chopped fiberglass mat is held together with an adhesive. when you use polyester resin there are solvents that dissolve the adhesive and release the fibers. when using epoxy, there are no solvents in it so it is more difficult to get the fibers to release. you need to work the epoxy into the glass more than you would with polyester. this can make it a little harder to work with and for the glass to take odd shapes and sharp corners. not a big deal, just wanted to mention it.
 
i have used it on smc. my waverunner hull is smc and i have had no issues. just be sure you really feather out the repair with a grinder wheel and 36g disc and wipe the area down real good with acetone.
 
As far as poly resins, the better quality ones have an extremely short shelf life. Mixtures some fiberglass production shops use are delivered weekly and may only have a 2 week shelf life. Mixtures some boat stores I've delt with & turn over regularly are usually best for a few months & is fairly decent for some car quality repair. Now the stuff that sits on auto store shelfs for years, probably purple toned, it's not for quality work.
As far as any shrinkage on a car part is concerned, getting some really gradual beveling into the repair areas helps minimized the effect, as compared to let's say filling in a screwhole unbeveled, which could eventually show even with good stuff.
As Jim mentioned with epoxy, you do have to work it more, but any good epoxy is much better for the type of repair a GN header panel would typically need, adhesion & minimal shrinkage will be worth it. I think at one time Fiberglast did have a binder free mat for epoxy, don't think they have anymore. You can also pull & cutoff short strands to work into the mixture to improve fiber to resin ratio if needed.
You can always epoxy over poly resin, but never poly over epoxy.
 
SMC repair using West System and fiberglass mat..

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