Fiberglass epoxy

[wrp]

Some bad advice being passed here. Carbon fiber passed good advice.

A few points:
Epoxy is not compatible with fiberglass mat. It does not properly break down the binders holding it together.
West system is a very well marketed and over priced low temp and relatively low strength epoxy. That said, Expect to pay at least $50 a quart for quality epoxy.
Epoxy does not play well with the vinylester resin used to manufacture a factory five body.
The vinylester resin sold by US Composites if properly mixed and cured will have better properties than most low buck epoxies, but not even close to quality epoxy.
Make sure that you buy wax to add to the resin if buying from US Composites as what they sell does not have it. Alternatively, you can coat your repair with some PVA spray and get a good surface cure. Using wax is easier than PVA spray.

Curious to specifics here. I find many reluctant to make specific recommendations and understandably so since there seems to be many routes to the final product. In your response you say Epoxy is not compatible with fiberglass matte and you say it does not play well with the vinylester resin used to manufacture the Factory Five Body. You make the case for vinylester resin yet your final caveat seems to imply that quality epoxy would somehow be optimum. What is an example of a quality epoxy that would work with our cars? I am overwhelmed by the different concoctions of various vendors and have tried, but do not grasp the chemistry that sets out families of products.

[carbon fiber]

Curious to specifics here. I find many reluctant to make specific recommendations and understandably so since there seems to be many routes to the final product. In your response you say Epoxy is not compatible with fiberglass matte and you say it does not play well with the vinylester resin used to manufacture the Factory Five Body. You make the case for vinylester resin yet your final caveat seems to imply that quality epoxy would somehow be optimum. What is an example of a quality epoxy that would work with our cars? I am overwhelmed by the different concoctions of various vendors and have tried, but do not grasp the chemistry that sets out families of products.

I'm not Mikeinatalnta, but this is the basic idea. The vinyl ester uses mekp for a catalyst. Epoxy doesn't. They are two different chemical make-ups. The epoxy is stronger and has better adhesion properties in general, but the vinyl ester to vinyl ester seems to "melt together" (fresh, similar catalyst breaking down the cured surface for a better bond) as opposed to the epoxy gripping the already cured vinyl ester part. I've had bad results with epoxy to vinyl ester in the past. As a rule, use whatever the original part is made of. I'd still use vinyl ester with a poly part, they've got the same catalyst, and poly is so cheap I wouldn't use it at all. I'm sure Mikeinatlanta can shed even more detailed light on this, he's the most experienced composite guy on the forum.

[wrp]

I'm not Mikeinatalnta, but this is the basic idea. The vinyl ester uses mekp for a catalyst. Epoxy doesn't. They are two different chemical make-ups. The epoxy is stronger and has better adhesion properties in general, but the vinyl ester to vinyl ester seems to "melt together" (fresh, similar catalyst breaking down the cured surface for a better bond) as opposed to the epoxy gripping the already cured vinyl ester part. I've had bad results with epoxy to vinyl ester in the past. As a rule, use whatever the original part is made of. I'd still use vinyl ester with a poly part, they've got the same catalyst, and poly is so cheap I wouldn't use it at all. I'm sure Mikeinatlanta can shed even more detailed light on this, he's the most experienced composite guy on the forum.

So vinylester is the way to go for our cars?

[carbon fiber]

So vinylester is the way to go for our cars?

Yes. Just like in comment #3.

[DaveS53]

So vinylester is the way to go for our cars?

A lot of inaccurate information has been posted. Vinyl ester resin will certainly work, but so will any other polyester resin that uses MEKP as the hardener. It is WRONG to think that new resin somehow melts into the old resin. That does NOT happen. Once the resin is fully cured, nothing melts into it. Repair bonds made later are strictly mechanical. That's why you should create a large area that is sanded deeply, to maximize the contact area.

Also note that when you apply body filler or spray on any of the many Evercoat polyester primers, you are not using vinyl ester. They will all bond well to properly prepared fiberglass.

I've made repairs to my fiberglass body with ordinary bondo brand resin, at the very top of a fender where is shows and have had no problems with read-through, even with a black painted car. The repair required sanding away all of the old fiberglass to create a hole that was over an inch in diameter, to remove a crack from a rock thrown into the underside of the fender. New fiberglass mat was applied to both sides of the repair, in one application.

Here's info on the use of mat with epoxy. Stitched fiberglass mat is made specifically for use with epoxy resin.

http://epoxyworks.com/index.php/chop...mat-and-epoxy/

The third picture doesn't look like much, but it shows the area where I removed about 12 inches of the wheel opening, pie cut about 1 inch from the fender and fiberglassed the parts together, to alter the shape of the opening. Increasing the opening by an inch allowed the large tire to be removed, with removing the coil-over and dropping the who rear end down, like a pro-street car. The mod was done with bondo resin and mat to both sides and it's held up great.