I have done the rust repair on my samurai. Cut out the rust and welded in sheet metal. Due to more warpage than I had anticipated, [ and me heat shrinking the oil canning before welding in new metal ] I am left with voids in the rear fenders 1/4" deep, tapering to zero depth. I have filled these voids almost full with layered fiberglass cloth and resin.
I did this for two reasons........one, I will be bolting on large plastic fender flares, and the bolts will be going through the repairs. I didn't want the bolts going through 1/4" thick plastic body filler.
Secondly, I just didn't want plastic filler 1/4" thick!

Anyway, I still have epoxy primer to apply, fiberglass strand plastic filler, regular plastic filler, Nason high build urethane primer, and Imron paint to go.

This won't be completed this fall.......i work outside under a costco carport, and the fall rains are almost here, putting an end to my body work efforts for the year. I want to get the fillers, high build primer on these fender repairs, and cover it with some temporary *?what?* to waterproof the repairs for the fall and winter weather until I can resume the build in the spring.


Questions please;
After grinding / sanding down the fiberglass cloth high spots, and exposing the bare metal around the perimeter.......should I spray with epoxy primer? Over the fiberglass too or just the bare metal spots?

Should the Evercoat brand short strand body filler go directly over the [ ground-down ] glass cloth and over the bare metal.....skipping the epoxy primer?

What should / could I cover the high build primer with, to avoid moisture absorption over the winter?


Thank you for your thoughts

Just read this interesting test;
http://www.autobodystore.com/filler_&_epoxy.shtml

Just a word of caution on these "tests" - I say this not just because the one you linked but because of others I've seen here and on other forums, especially related to epoxy.

None of them are scientific.

I spent 10 years working in a chemical analytical lab. You would not believe the level of control, process detail and equipment that is required to conduct even simple materials testing.

When one of these internet chemists wants to pony up the $10K to $20K it takes to do a set of comparative tests that actually have science behind them...then we can have a conversation. Until then, stuff like this and other examples I've seen on YouTube, etc - not worth a plugged nickel.

Yeah, I agree with Chris on that "test" thing. I do a lot of testing "for myself" to prove points but it is wayyyy... over simplified compared to the independent laboratory testing we've had done on chemicals in the past. That guy was only testing ONE brand and type of filler there so....
I can help a little with some of this since I built several kit cars that I "test" with epoxy on them through winter's use before I fully painted them.

Your questions were...
After grinding / sanding down the fiberglass cloth high spots, and exposing the bare metal around the perimeter.......should I spray with epoxy primer? Over the fiberglass too or just the bare metal spots?
Yes, you are going to need to get full strength epoxy over all this if you are "sealing" it up for winter. Even at that epoxy will give some waterproofness however it is sensitive to breaking down by UV exposure when left unpainted. I've have driven cars up to about 8 months with little degradation however I did sand the epoxy back and put more on before moving on to base/clear.

Should the Evercoat brand short strand body filler go directly over the [ ground-down ] glass cloth and over the bare metal.....skipping the epoxy primer?
Yeah, that's where I would put it, then epoxy over all that.

What should / could I cover the high build primer with, to avoid moisture absorption over the winter?
High build is going to have to be covered with epoxy as well.

And after even all that.... I would still try to keep those surfaces "high and dry" and garaged if possible.
Oh, and when it come time to attach those fenders you better use some type of sleeve bushing and decent washers when you go through that filler package or you will get spider cracks radiating from every one of them.

You should not have used cloth and resin on metal. It will eventually fail due to expansion and contraction differences between the two materials. Long and short strand provide superior adhesion and strength when used on bare metal. Shortstrand is often used successfully in thicknesses over .125 on sail panels instead of the original factory lead. Nobody in the restoration industry is layering cloth and resin for that area or any other metal repair. No way would I use it on a restoration when a customer is throwing a bagful of money at a job.

That link posted about epoxy and filler carries no weight. Yet it is still on a site that sells autobody supplies.

I'd strip all that mess off, take the repair area and surrounding area down to bare metal, and apply some short strand for starters. You have resin and 'glass slathered all over paint and a poorly prepped surface. Use long strand for the first coat if the small .250 thickness scares you. Finish with a quality filler like Rage Ultra (Rage Gold sucks in comparison) and blow on some epoxy.

I'll let you pick your epoxy and how much you want to spend. There are better, inexpensive epoxies out there beside the common ones that very few use unless they talked to a rep.
Under PPG's commercial line I sometimes use a polyurethane primer that can be used as a stand alone product, needs no topcoat, and is CAT approved. The CRE epoxies are excellent as well. They get no mention on these types of sites.

ScottB wrote:Under PPG's commercial line I sometimes use a polyurethane primer that can be used as a stand alone product, needs no topcoat, and is CAT approved

Scott, which one - do you have a product number? Is it suitable on a restoration, any issues with shrinking?

chris wrote:

ScottB wrote:Under PPG's commercial line I sometimes use a polyurethane primer that can be used as a stand alone product, needs no topcoat, and is CAT approved

Scott, which one - do you have a product number? Is it suitable on a restoration, any issues with shrinking?

Chris, HSP2128BK(Black) Great for floorpans, bellies, etc.. Not death black, so underhood finishes need a different topcoat. I have not used it under an exterior finish coat yet so cannot provide that info.
CRE epoxy is great, inexpensive, can be hammered on, zero shrinkage, awesome build capabilities, sandable which is unlike many epoxies (not as sandable as a nice 2K urethane but certainly not horrible). It can be used under or over filler. Get your filler work nice, bang on three coats of CRE, blocksand, follow with a 2K of your choice as a final and you are shining. Other resto shops here beside myself use it. My jobber who worked at the PPG training center told me about it. These products also have a tintable neutral base and the final hue can be chosen. http://us.ppgrefinish.com/PPG-Refinish/ ... e-Coatings

Price it out. Compared to PPG DPLF it is a joke. I stopped using DPLF long ago. I still use
R-M EP Series and ********** occasionally. It depends on the job.

ScottB wrote:Under PPG's commercial line CRE epoxy is great, inexpensive, can be hammered on, zero shrinkage, awesome build capabilities, sandable which is unlike many epoxies (not as sandable as a nice 2K urethane but certainly not horrible). It can be used under or over filler.

I was really impressed with this primer a couple years ago, but a resto shop that I trust, told me that it is not an automotive product, and his testing showed a lack of proper chip resistance. Have you checked that Scott?

Also if you check the data sheets
Recommended dry film thickness of DPLF is .75 to 1.5 mils to get the performance they claim.
Recommended dry film thickness of CRE series epoxy is 2 to 8 mils to get its claimed performance.

chevman wrote:

ScottB wrote:Under PPG's commercial line CRE epoxy is great, inexpensive, can be hammered on, zero shrinkage, awesome build capabilities, sandable which is unlike many epoxies (not as sandable as a nice 2K urethane but certainly not horrible). It can be used under or over filler.

I was really impressed with this primer a couple years ago, but a resto shop that I trust, told me that it is not an automotive product, and his testing showed a lack of proper chip resistance. Have you checked that Scott?

Also if you check the data sheets
Recommended dry film thickness of DPLF is .75 to 1.5 mils to get the performance they claim.
Recommended dry film thickness of CRE series epoxy is 2 to 8 mils to get its claimed performance.

It dries hard so chip resistance is less than other epoxies. You over-reduce it in auto refinishing applications and not pour it on like in industrial applications. If doing a frame where pitting is deep it can be loaded on. That is one of its characteristics.

I called PPG and spoke with them about it also. Obviously it is not in their Auto Refinish line so it would not be officially recommended to be used. If the reps I spoke with are wrong and the other resto shops using it are having comebacks I'll find out about it.

If I had to worry about film thickness all the time I could never do custom bike jobs where burying graphics and artwork greatly exceeds any recommended clear film build.

If you use R-M EP it gets reduced as a pre-coat, which thin also compared to their other mixing ratios for it. EP can be used many ways.

DPLF is overpriced and there are numerous other quality epoxies out there. R-M is no bargain but I like it more than DPLF.

What testing did this shop of yours do? Controlled lab tests?

ScottB wrote:If I had to worry about film thickness all the time I could never do custom bike jobs where burying graphics and artwork greatly exceeds any recommended clear film build.

DPLF is overpriced and there are numerous other quality epoxies out there. R-M is no bargain but I like it more than DPLF.

What testing did this shop of yours do? Controlled lab tests?

My guess is that is was (in shop) testing. It was more of a question for you.
I agree on the cost of DPLF, I use ********** epoxy.
My point on the film thickness is that it takes at least three times the amount of epoxy to get the same performance as DPLF---and that adds to the cost factor--- when using it for the same purposes that DPLF is used in.