Can you fiberglass over short strand filler?

[Ian G.]

Hi folks,
I'm still working on the rear underside of my '59 body repairing spider cracks. I've experimented with sanding them and laying mat vs. grinding a "V" and filling with short strand filler. I'm paranoid judges are going to give me a deduct for obvious filler repairs on the underside. Would I get deducts for obvious fiberglass repairs done with filler, given the underside is unpainted? My filler is Evercoat Short strand/SMC filler, and I've tried 3 different cream hardener colors (red, blue, white) to see if it will look more tan.

So if you think I will get a deduct fr filler repairs, the question is: can I sand down filler repairs and lay a layer of fiberglass mat over it to get it to look closer to pristine? or thats just too much work and I'm over thinking it? I'm trying to figure out the most efficient way to do this as it is taking me tons of effort and rework using fiberglass mat only as the cracks go deep and I'm not the most skilled at this. See below some of the repairs I'm talking about. The first two pics done with filler. The second two without filler. Thanks in advance for any advice!

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[Ian G.]

Re: Can you fiberglass over short strand filler?

I should add I'm using Vinyl Ester fiberglass resin and the filler is Evercoat 100632 EVERGLASS Short Strand Fiber Reinforced Filler which seems to be polyester based. Looking around on the interwebs it seems they are compatible. I'm calling Evercoat to double check. I'm very interested in insight from members about the need to obscure the fillers for judging though.

[Mark S.]

Re: Can you fiberglass over short strand filler?

Since no one answered this yet, I will give you my perspective: V out the stress cracks and use small pieces of fiberglass matt and resin to build up the Vs. You may want to build up beyond the surface a little bit and them sand down smooth. I f that bothers you, you can purchase coloring additives that are usually sold by marine dealers to give a closer match to the surrounding fiberglass. For me, I would fix the stress cracks and clean the areas on the underneath with Scotchbite pads and a strong cleaner. From my experience the judges should give you a little lea way because the bottoms of these Corvettes were not perfect. The other option is to find some rather large chassis judges that have trouble getting under C1s. I have done chassis in the past and ruined some nice shirts. Best of luck. Remember, this is supposed to be fun, and judges are there to help you.

[Ian G.]

Re: Can you fiberglass over short strand filler?

Hi mark, I appreciate you answering. I tried that way at first and just wasn't happy with the results. I do have tan resin dye that colored it fiberglass patches fine. Since this is on the underside, I kept getting bubbles and droops and found myself having to redo it over and over. I ended up getting demotivated and ignoring the car for a long while and finally revisited and just ground it down and then patched over it with a few long lengths of mat, and sanded the curve in (visible 4th picture). So then I decided to try the V method with the short strand filler, which was FAST and EASY, but as you can see it's grey. Maybe there's a short strange filler out there which is tan?

I may go ahead and try your way again and try taping the mat down to keep it from drooping and getting bubbles, but I'm not optimistic of my skills in this area. I've been working on this car now 17 years and got it to the stage of a rolling chassis, but the fiberglass work is not my favorite part of the hobby. I am a perfectionist and hate the idea of using the filler, but if I can't get your method to work I think I will hope for a judge who doesn't crawl under the car that far

[Mark S.]

Re: Can you fiberglass over short strand filler?

I have used racer's tape to hold the resin patch in on the underside with some success. Don't be too hard on yourself. It took me 35 years to restore my 56 the way I wanted it to be.

[Ian G.]

Re: Can you fiberglass over short strand filler?

Ok I do have gaffers tape (same as racers tape per interwebs). I'll give that a shot. I guess I have another 17 years to muddle along then I'm also waiting for a callback from Evercoat tech support :O

[Dave P.]

Re: Can you fiberglass over short strand filler?

I saw this thread yesterday but wasn't sure if the project is "overhead", or on a rotisserie. It's overhead. I was thinking that a layer of light matt laminated over the filled cracks might give the desired appearance? Not sure about color. But laminating overhead is tough. There is a technique called "vacuum bagging". I'm familiar with it in boat building, particularly with epoxy and carbon fibers. But vinyl-ester and polyester can be successfully vacuum bagged.

I used "can you vacuum bag fiberglass" as my search words. This return has the basics for the materials needed. There's probably youtubes too.

You need a vacuum source. I used my refrigeration vacuum pump and an "old" propane bottle (the kind you can't refill any more) with some McGyver'd fittings. I put a ball valve on the hose to the bag. Connected the pump directly to the tank and pulled it down. When you open the valve, the bag flattens immediately. And if resin does get in the hose (it shouldn't) it goes in the tank and not in the pump.

A result of the technique is a tight lamination with a smooth surface.

Vacuum bagging may be more than you want to get into, but something to take a look at just to increase your knowledge base.

[Ian G.]

Re: Can you fiberglass over short strand filler?

Hi Dave, Thanks for telling me about this. I indeed did find some youtube videos. This level of professionalism is probably beyond me though. I think it would get very hard to replicate the complex shapes on the underside of the car. Though I think this method would get it about as close to factory as possible with a mold preformed for the job, without perhaps patching in a replacement piece.

[Gary B.]

Re: Can you fiberglass over short strand filler?

Ian,

When repairing round holes, or for flat areas I use Teflon rod to keep the hole perfectly round or Teflon sheet on either of both sides of flat repairs. Or thin Teflon sheet that can be bent into curves. The cured fiberglass repair releases easily from the Teflon.

Gary

[Ian G.]

Re: Can you fiberglass over short strand filler?

Hi Gary, do you have any pics of what you mean, especially about use of the teflon rod? Do you put the teflon sheet on either side of the repair to protect it? I've been using kitchen plastic wrap to cover the repairs to keep them from dripping, and to then use my fiberglass roller. It doesn't release well, but I end up needing to sand it flat anyway...

[Gary B.]

Re: Can you fiberglass over short strand filler?

Ian,

One regret I have in restoring certain parts on my car is not completely documenting all phases of a project. Having said that, here’s an example of a repair I did for the rear valance of my ‘66. I have a great before photo, and a nice in-process photo, but alas no post-repair photo. I was so pleased with the result I excitedly reinstalled the valance before taking a final backyard photo. In any case you’ll get the idea of the use of Teflon rod and Teflon sheets.

One think to note is that there will typically be an air bubble or two in the repair after removing the Teflon sheets, but those I fill in with more resin mixed with finely chopped up fiberglass mat, applying it with a putty knife. Chopping up the mat and mixing it with resin is the same thing I did for the main repair. The two flat surfaces and hole came out so nice as is that I had to do very little sanding of the repaired area before some rattle cat touch up on the exterior side.

Gary

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[Gary B.]

Re: Can you fiberglass over short strand filler?

Ian,

I found one more in-process photo, after removal of the clamps and Teflon pieces, but before filling any small surface air bubbles, sanding or painting.

Gary

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[Ian G.]

Re: Can you fiberglass over short strand filler?

Thanks Gary. It's a similar ideas to the vacuum bagging to get a good flat compressed repair. That could help on some of the underside repairs for sure if I tape it down. I'll keep that in mind when I decide whether to repair some of my damaged bonding strips vs replace with repros I have. Do you recall what thickness teflon sheet you used?