I heard I should use a fiberglass body filler to really waterproof it after I weld sheet metal. I take it my Rage Extreme doesn't have fiberglass, what is a good/ compatible fiberglass filler that I can put rage over? Is this necisisary?

I think it's a very good idea. Any fg resin that is waterproof will work, as in stuff that's advertised for boat hull repairs, etc. It's important to use it IMO in order to seal the weld from moisture penetrating from the backside. If any pinholes exist in the weld and moisture gets through from the back, it could be absorbed by regular plastic filler which is not waterproof. If filler absorbs moisture it usually bubbles the paint on it. Plastic filler should go on over the resin to smooth the surface for primer. It's also a good idea IMO to POR-15 the welds on the backside after applying the resin on the front. I used this method 5 years ago and it's still holding up well.

Evercoat's Everglass is about the best I have found. Stay away from the All Metal or Alumafill stuff-junk in my opinion

The problem is NONE of these products are waterproof. They may say waterproof on the label, but by calling the tech dept I found that meant AFTER it was primed and painted, DUH. Anything is waterproof after painting and painting. It has just as much talc as a regular filler (checked the MSDS) so it is going to absorb water.

I am not saying it is a waste, because I still feel it is more "water resistant" than regular filler, but it is not waterproof. I have however seen Everglass do some amazing things in "hack" rust repair where it held up much better than I ever would have thought.

But to use a special filler "just in case" there are pin holes in the welding? I would say, spend some more time on the welding and/or protect it from the back makes more sense.

Because, I don't care what you had over that weld on the outside. If you have a pin hole in the metal and it is exposed on the back, it is GOING to fail.

To answer the question though, Everglass is my choice as well for this work.

I have been using my shop light that is a floresent hand held to expose pinhoes from the other side but I am going to try the glass as a extra step, I know if you had a scope and looked at any MIG weld you could find inclousions, ie water entry holes!

Am with everyone on this NO FILLER waterproof be it extreme or all-metal its NOT WATERPROOF.

Do a search on here for duraglass, I posted a pic of the label to clearly show that it contains the SAME amount of talc as regular fillers.

I like Upol's fiberall

FWIW I said "fg resin" not filler. As in the liquid part of fiberglass reinforced plastic. As in what boat hulls are made of. Is resin not waterproof?

Fiberglass resin (polyester resin) absorbs water. Most all fillers "bondo" are the same just with diffrent fillers added. Gel coat on a boat also does, sorry to say but true.

I know what youre taling about using. I used a fiberglass filler on most everything i have welds on. I replaced both rear quarters and used it where i beat in the seams so i could smooth it out. Im told it will minimized the consensation that platic gets from expanding and contracting witht he change in temps. The stuff i got is green in color. Smells kinda good but im kind of a huffer lol. Just kidding

The problem is NONE of these products are waterproof. They may say waterproof on the label, but by calling the tech dept I found that meant AFTER it was primed and painted, DUH. Anything is waterproof after painting and painting. It has just as much talc as a regular filler (checked the MSDS) so it is going to absorb water. I've done temporary repairs on boats and jetskis with everglass, and sometimes they've ended up being permanent repairs(without paint). Maybe the surface does in fact absorb water but I guarantee water will not penetrate everglass. You could make a water container out of this stuff smile.gif Not like regular fillers including the silver ones.

Last weld repair I did, coated the back of the weld joints w/ seam sealer. Brushed it on and smoothed out when wet. Unless the welds are real bogus, you should not need anything or at the least very little.