I notice on the hot rod shows, they will often use duraglass or kitty hair which is apparently shredded fiberglass in an epoxy base. They spread this over large areas and then put plastic filler over that. I've never heard a good explanation of when to use/not to use. Is it for strenth? moisture protection?
MIke

Both but it doesn't shrink like polyester sometimes does either.

It's stronger and made with a polyester resin. Evercoat's Glass Lite is also a good product that sands much easier. For me the bottom line is I've never seen a failure using Everglass-it's good stuff IMO.

Got it. Thanks for the replies.

You guys are not going to like what I say here, but in the intrest of helping someone out here goes. I would not go to the trouble of throwing kitty hair over the fence. My exprience with It was that its hard to sand and dosent bond very well, really hard to feather because it trys to roll up on the edges from lack of bonding. My point is that if the repair is done right you will use very little filler on the repair and any good polyester will be fine and and last for years.

You should really only need it over a welded seam like on a patch panel. Kitty Hair(long strand fiberglass) is mainly used for filling rot holes.

You guys are not going to like what I say here, but in the intrest of helping someone out here goes. I would not go to the trouble of throwing kitty hair over the fence. My exprience with It was that its hard to sand and dosent bond very well, really hard to feather because it trys to roll up on the edges from lack of bonding. My point is that if the repair is done right you will use very little filler on the repair and any good polyester will be fine and and last for years.

I agree,........and disagree. I don't use it on exterior surfaces, but I do use it to seal the back side of patch panels. ie:1/4's, rockers, etc. It helps keep the repair water tight. About the only time I use it on the exterior is when the surface is fiberglass. Yes, to feather tiger hair or whatever your useing is a giant PITA. That's why I get it as close as I can and do the finish work with regular mud. (plastic filler, NOT earth and water) Also, when I prep for tiger hair, I use a 36 grit grinding disc and really rough up the metal. It sticks just fine to that.

I use a skim coat on my repairs, it's waterproof, Then I finish with bondo. I coat inside areas with por 15.

Lets make something perfectly clear here, it is NOT "waterproof". Now, I have not called the Duraglass makers, but I have called Evercoat who makes a competitive product, "Everglass" and that "waterproof" note on the can is pretty much AFTER it is primed and painted!

It on it's own, is basically ONLY regular filler with some chopped glass stuck in it. It is polyester (fiberglass) resin, talc and chopped glass where regular filler is resin and talc.

Honestly, in my opinion there is no big difference for any "usual" repairs. Regular filler used anywhere near correct will outlast the car and you and I. That is as good as I need. :)

Brian

Sooooooo....after reading & hearing from the experts, it seems if I want extra strength for some reason I would use glass filler. Like a large panel that might flex & cause cracking. Otherwise, good prep and regular filler sounds like the order of the day. Brian gave me a real eye opener about chopped glass being the only difference regular polyester filler and Everglass (and like he said, probably the other competitors as well). Thanks for the education.
Mike

Chopped Glass is not the only difference. I can't speak to the chemical content but from my experience even the duraglass without the heavy glass in it is infinitely stronger and doesn't absorb water.

Do a test - lay out a 1/4" thick section of both on wax paper. let both cure and then try to snap both in half. You will see the difference immeditately. Also water will run off of duraglass after sanded it will soak into regular "mud". I have seen planty of repairs with regular mud deteriorate without proper sealing. I have not seen the same with Duraglass. But make no mistake, I believe that proper sealing is key to any good repair.

Just my .02.

Troy.

I would use duraglass anywhere you have a welded joint, if it has fiberglass in it, it stands to reason it should be a little less resistant to cracking.

Some of the sheet metal is about 1/32 of an inch thick, and all put together with spot welds, temperature change and rough roads, that would contribute to some parts of the body to flex a little.

One of the problem areas is where the quarter panel ties into the roof, filler cracking and even lead getting rust under it.

But I think one of the problems with any filler failure is not replacing body mounts after a certain number of years, and the improper shimming when they are put in could contribute to it.

I also am suspicious of putting a lot of weight in a trunk, after looking at my body mount in front of the back wheel, where it was indented about a 1/32 of an inch into the support, and the mount between that and the cowl was not indented.

If you take a good luck at the structure of a frame from the back of the wheel well to where it straightens out and continues to the end of the frame.

That area is hanging out there with out a lot of strength, so if you do put a lot of weight in your trunk, the support in front of the back wheel is going to have to compensate, and that leads me to believe that some of the separation on my sons 70 chevelle could have been cause by this.

His wheel well was pulling away from the trunk, you could see a good sized gap, but the 725 horse motor might have been the problem.

Just my 2 cents, I'm not sure of any of it, but I tend to wonder about it

On chevelle tech, I have a couple of pictures of my body supports, under pros and cons of of poly bushings, I know this thread is about filler, and maybe I shouldn't have brought all of this into it, but I think its all related.

Rob

Chopped Glass is not the only difference. I can't speak to the chemical content but from my experience even the duraglass without the heavy glass in it is infinitely stronger and doesn't absorb water.

Do a test - lay out a 1/4" thick section of both on wax paper. let both cure and then try to snap both in half. You will see the difference immeditately. Also water will run off of duraglass after sanded it will soak into regular "mud". I have seen planty of repairs with regular mud deteriorate without proper sealing. I have not seen the same with Duraglass. But make no mistake, I believe that proper sealing is key to any good repair.

Just my .02.

Troy.

Troy, I did it. I didn't lay it on the wax paper. But what I did was just check how water reacted when poured on the two different products. At first I tried unsanded Everglass and Rage. I was amazed to see that the Everglass appeared to soak up the water while the water clearly beaded up and ran off the Rage with Zero left, no kidding. But once sanded, that all changed. The water stayed beaded up on the Everglass while imeadiately started soaking into the Rage. The wet area around the water bead got bigger and bigger on the Rage until the water was almost all gone. When sanding it, the paper got gummed up real bad and had to be replaced. The Everglass did have a water mark when the water was poured off. But it sanded very easily to a nice powered finish.

I did a hammer test to the rear of both of them and it seamed the RAGE adheared a little better than the Everglass. But that was pretty unscientific so it means next to nothing as far as I am concerned.

But the water, yep, I admit, it did fare a lot better than the "regular" filler.

Brian

I use "dyna-hair" long strand fiberglass filler for big rust holes and the back side of repair panels or anywhere i have a big volume to fill up. It works great for those applications - i'm brand spankin' new at this stuff so this means pretty much crap :D

I found its kinda tough to apply with a paddle; i put on gloves and use my fingers to really squash it in where i want it and apply alot of extra pressure. I can get as even a surface with my hands as i can with a paddle on bondo plus it seems to adhere really well. I cant see using it for normal stuff, but for gaps, big holes, etc its nice. And it seems more or less water proof to me. My truck has had to sit outside in the rain sometimes before i got primer over everything. The bondo soaks it up like a spunge but the fiberglass didn't absorb any.

Like i said i'm new to this so this is entirely based on my opinion and observations not expertise or expierence.

Brian, what your seeing is the water absorbtion related to the amount of talc in each product. Do another test with just resin with chopped glass mixed in-even less absorbtion. Not saying this should be used in repair, but it does work if epoxy primer is applied first to help with adhesion.

I hate to even mention this but I watched my Son booger up a rusted out piece of worthless junk for the Father inlaw last spring, holes the size of baseballs were filled with fiberglass and kitty hair! He started by sandblasting all the rust away and applied three coats of epoxy primer, all the glass and fillers were applied over the primer. Amazingly to look at it now you'd never know, no shrinkage, no adhesion problems from expansion/contraction, and no rust because he coated the backsides of the repairs with a self healing live rubber rustproofing. How long will it last? I have no idea but it is battling the salty U.P. roads just fine so far. But I know without the epoxy and rustproofing I'm sure it would be failing miserably by now. Definately an extreme example of product abuse. I just shook my head and laughed when he did the job, and laugh again every time I get a chance to reinspect the repairs.

Bob, you know what, I checked the MSDS a few years ago on these products. The Everglass had MORE talc than the Rage!

You know, I never believed in these products as far as filling rust holes. But there is a place where something like that is the "Bestest" way to do it, as your son found out.

When I was a rep I serviced a small town on the coast of Ca called Mendicino. It is the the location of the fictious town "Cabits Cove" from the "Murder she wrote" tv series. Anyway there was a little body shop there that I walked into one time to see him filling some pretty big holes in the roof of a school bus. He told me how he would do this and the bus would last another ten years or so. He had done a number of them like this over the years. They really held up pretty good, and kept the thing in service. I started looking at these fiberglass reinforced products a little differently after that.

Brian