Fiberglass epoxy

[Svtfreak]

Ok, so I know all about different body filters and quality and such. What about fiberglass epoxy? Just the resin and hardener. Is any brand better than another for any reasons? I'll be using glass mat and flock coming up to make the firewall/body interface match better and fill things like the FFR taillight holes and even attempt making a few covers and parts and such.

Ok my 23 t bucket years ago I just used bondo and hardware store barands and it worked wonderfully but I wanted to get some more experienced advice before starting this one.

[chuckster]

West system epoxies, developed for the marine industry. They are the leaders in R&D and they have a product for every situation.

[carbon fiber]

I'd use vinyl-ester resin, it's what the body is made with. I get my stuff from U.S. Composites, They're as good as west IMHO and cheaper.

[DaveS53]

I've bought products from fiberglass supply. I used isothalic tooling resin for high temperature resistance when I bonded core foam to the top of my car, to create an insulated fiberglass headliner. Also used it to build the fiberglass layer inside the car that serves as the headliner.

Vinyl ester resin is available for $57 a gallon. I would not use a true epoxy - they cure too slowly and may not be compatible with subsequent applications of polyester primer.

http://fiberglasssupply.com/Product_Catalog/Polyester_Resins/polyester_resins.html

Also note that many resins are laminating resins that will remain gummy on the surface and not sand well, unless used with a mold, where gel coat is first applied into the mold. When making my headliner, I avoided that problem by applying a coat of evercoat polyester primer, over the resin, before it was fully cured. The resin will only be gummy if it cures with air exposure. Carefully laying saran wrap over some small repairs may be possible and will eliminate the gummy surface condition. Another option is to use a finishing resin, but that type of resin must be cleaned and sanded if multiple layers are applied. Most of the changes I made to my body were done with only one application of multiple layers of glass mat. I bought some 1.5 ounce mat that is twice the thickness of the stuff you will get at your local auto supply shop or Walmart.

I cut multiple pieces of mat to the size needed and often wetted them with resin on a mixing board, then picked the lamination up and moved it onto the body. I made a large mixing board from cardboard, covered with packaging tape.

FWIW, I've also used the general purpose bondo brand resin and had absolutely no problem with it. I used it to make alterations to my hood sides, near the radiator. That work was done 2 years ago and it's holding up just fine on my black painted car. I also used it to patch and strengthen large areas of my inner doors skins.

There is no good reason to use marine products for fiberglass body repair or making new parts.

[boBQuincy]

West system epoxies, developed for the marine industry. They are the leaders in R&D and they have a product for every situation.

+1 for West System, I have used it for over 20 years and not found anything better.

[Derald Rice]

Another endorsement for the West System Epoxy. Great adhesion to our fiberglass and available at a lot of local shops.

[Jeff Kleiner]

What Carbon Fiber said.

Jeff

[carbon fiber]

Do yourself a favor also and stay away from bondo body filler. Get Evercoat Rage Gold, It's worth every penny. It's doesn't shrink like bondo and sands light years easier. Don't use the bondo brand resin either, it's the cheapest poly (not vinyl ester) resin you can get, and is super thick and doesn't penetrate the fg matt easily.

[DaveS53]

Evercoat sells a wide variety of similar high end fillers. I've used a couple and they worked fine, but I really liked U-Pol gold and their gold glazing putty that I got from auto body tool mart.

[Svtfreak]

Thanks y'all. I think I'll go with the us composite system vinyl Esther.

As far as last two replies, my filler of choice is the newer 3M variant. I used rage gold on the mark 4 for awhile and the girl at the paint supply shop recommended the 3m so I gave it a shot. It works very well and is slightly cheaper. No pin holes, decent working time, and hasn't popped out anywhere yet so I think I'll stick with it for filler.

[BASmith]

Svtfreak,
If you haven't talked to Tim W. about glassing yet, do so. He is very experienced in this also.
Bruce

[mikeinatlanta]

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.

[Svtfreak]

Mr Bruce, thanks. I'll give him a call.


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.

I did go with the USComposites vinylesther. I also did get the wax as most of the repairs I make I intend to do with one application. I dunno not add wax if I have to later it until last layer, but I haven't run across anything yet that I think that will be required. Their temp rating of 240 degrees should be perfect.

[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.

[TxMike64]

I'm not a chemist or physicist...

Sounds like another pro for the steel body.

[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.

[carbon fiber]

I'm not a chemist or physicist...

Sounds like another pro for the steel body.
There's nothing wrong with composite bodies when made/repaired properly. Composites don't RUST. They are harder to dent. There are lighter. They can be easily repaired by inexperienced persons, that doesn't happen with steel. The most expensive cars in the world have composite bodies. You don't have to be a chemist or physicist to appreciate composites.73848

[Presto51]

I'm not a chemist or physicist...

Sounds like another pro for the steel body.

Hold up there young Skywalker with the pro steel body route.

If the steel body is not manufactured correctly, you would be amazed of the world of hurt that you would find yourself to be in.

Steel has a mind of it's own and if you are not a whisperer, it can get very ornery, very quickly.

IMHO

[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/chopped-strand-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.

[carbon fiber]

I'm not going to argue, I've had this conversation over and over. I've been using vinyl ester to vinyl ester for years with no problems, can't say the same about epoxy to vinyl ester. I understand mechanical grip, but vinyl ester to vinyl ester hasn't ever failed me like epoxy to vinyl ester has. I work with composites every day, I know what works. Way more than one repair under my belt. As far as epoxy and chopped stranded matt, it says right in the article it doesn't break down the binders and they end up suspended in the epoxy. (Like miniature voids, not great for strength) If you're working with epoxy (on an epoxy part) just use woven material, problem solved. I think the bad advice is to tell people to use cheap poly resin or cheap body filler that have high shrinkage, aren't as strong, and are harder to use/sand. Also note, comparing body filler/paint to a structural repair is irrelevant. Bubble gum would stick too, but it won't contribute to overall structural strength.

[DaveS53]

Expensive body filler is easier to sand and that's all. That's enough reason to use it if you're sanding large areas. I use Evercoat or U-pol, but there are many good products to choose from. I also use fiberglass reinforced filler for a really deep fill. Nothing wrong with bondo brand - it sands quite easily. The reinforced filler should always be top coated with a finishing filler.

Paint is decorative, but it has to adhere to the substrate. Same goes for body filler and polyester primer. They will all adhere just fine to any polyester or vinyl ester resin.

From what I've read of physical properties, it's hard to beat vinyl ester resin. Isophthalic (polyester) resin may have a little better heat resistance, but it's not as strong. Whether you need the extra strength depends on what you're doing with it. Making small parts or small repairs is not at critical as making large parts from scratch.

I wouldn't use epoxy either. It cures slowly and and doesn't sand well. There is no reason it should not bond well - that's one of the better features of epoxy - high bond strength.

If you want a really high strength product made of carbon fiber, epoxy resin is the best choice. That's what they use to make bicycle frames that cost over $3,000. They have to be strong and very light - some weigh only 2 pounds, without the fork.

Here's a really large build-up with fiberglass reinforced filler to start, followed by finishing filler and then polyester primer, followed by epoxy primer, just before paint. The work was done in April of 2014. The car was finished about 14 months ago - no problems so far.

[carbon fiber]

If you want a really high strength product made of carbon fiber, epoxy resin is the best choice. I agree.73861

[wrp]

Thanks Carbon Fiber

[Svtfreak]

Well, my repairs aren’t structural. The largest that I know of now is the tail light hike fillings. I’ve cut the old ones out and going to sand the gel coat deeper. Gonna cut the mat I have (not woven, the other kind) to fill a few layers. The back layer will be a little bigger and I’ve back cut the holes. Then a few layers to fill and the top layer will be larger, and I’ll bevel the front and leave a ledge for it to lay in. I’ll mix up my resin, soak all layers good, build my plug getting air out except the top layer, put it in the hole, layer some tape on the back to support it. Once it cures (about 20 minutes), I’ll nix up a little more with wax, layer my top layer on, and fill any noticeable voids with resin mixed with some 1/4” chopped strand I have. Hat should give me a good base to sand smooth then use body filler to get perfect.

[Svtfreak]

Oh! I will be glassing in a brace along the package tray area. I’ll mix up resin and “glue” the formed (probably wood shaped to fit) brace in. Once there, I’ll glass over it with 3-4 layers, working it in three sections. The final layer will get wax. If it’s strong enough, I’ll stop there. If not, I’ll continue.

Taking cues from the old t bucket build I did. That’s the only place I’ve found so far that needs help. A lot of help. But any other places that flex will get glassed in bracing.