Working with fiberglass?

J

jlwdvm

Member
I'm wanting to start the body work on my GT40 project before the weather turns colder. It's a fiberglass body with a few seams and a rather thin layer of gel coat. There are a few pin holes in the surface here and there. I'm used to working with metal and want to get this project off on the right foot. I have SPI epoxy and SPI high build 2K on the shelf. Platinum Plus and Platinum Plus glaze are my fillers. What is the best course of action to get this thing rolling?
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Scrub scrub scrub, Hot water and dawn or tide are going to be your best friends at this point Everything that has been pulled from a mold that was intended to be used more than once is covered in wax. Then 180 DA and SPI epoxy.
 
+1 on cleaning it really well before doing anything else. Personally I would sand the gelcoat with 80 grit. I wouldn't worry if I went through. Then let is sit a few days. Get it in the sun if possible. Then buzz it again quickly. Wipe it down really well then epoxy.
I would epoxy for build as well but that's up to you. I would use Evercoat Vette Panel Adhesive to fill any imperfections as opposed to using regular filler.
 
cant comment on the vpa that chris recommended since i have never used it but what i can highly recommend is adtech p14 or p17 filler. works like a regular filler but its a solid structural plastic when cured so its hard and has strength. wont soak up solvents or shrink. its highly heat resistant as well. in the marine world, its really popular. def ditch the regular filler. the glaze you have is fine for filling pinholes, etc. after a wash your going to want to wipe that gel down with acetone or urethane reducer. god only know what type of release they used on their molds. could be wax, frecoat, pva. you just never know.
 
Good info here! If I sand through the gel coat, I should be ok if I am sealing with epoxy before anything else? This thing needs a lot of work!
 
I am going to keep my comments on materials short here...just don't be afraid of using a polyester surfacer such as superbuild or clausens...
 
I guess I will chime in now because I haven't seen anything about panel fit. Making sure all the gaps are right and the panels work smoothly is something I like to do pretty early, and also decide if some method will be used to preserve panel alignment for easy post-paint installation.

In the old days I would go straight to poly primer on a job like this, but in the last decade I've been converted to an epoxy-based repair procedure for everything. If the body is rough, which such fiberglass replicas usually are, poly primer can be a great option, but the initial 2 or 3 stages are best done with epoxy, imo.
 
I figured panel fit was kind of obvious... but ya make sure everything is fit and adjusted the best it can be before you start grinding and cutting.

Also make sure your any and all seals are in place when lining up all of the panels.
 
Did body work on a few Corvettes. VPA (Vette Panel Adhesive) is your friend for body filler and doing any small thickness gap work. For large areas that need to be filled, you need glass and fiberglass resin/hardner. I order VPA from Summit and you do want to check the expiration date and you can get an old batch. Never had a problem with that though with Summit. And stir it for a good 5 min when you first open. VPA is great stuff. After you get the VPA work finished, I SPI epoxy prime 3 or 4 coats and follow the SPI Tech Manual. Agree with Chris and others above, need to Dawn wash, several, several times before starting and rough the gel coat really good with 80grit while watching your body lines. Also NO WD40 in the shop anywhere, anytime, by anybody, as it is the kiss of death for fiberglass for future paint bubbles.
Hope this helps. Super nice project!!!!
 
I spoke with an inside guy at the shop that builds my car. He is responsible for the bodywork they do at the shop for people that don't want to do it. He mentioned that the mold release they use is water soluble. He just power washes the bodies with dish soap and water before he starts body work.
I used my foam cannon with hot water to wash things up. I also scrubbed everything with some slightly used red scotch brite pads and soap. I plan on setting my gaps next...it's gonna take a while! Should I spray a coat of epoxy before spreading filler, or does it not matter since I don't have to worry about rust?
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The water based stuff would be the pva i mentioned earlier. Its usually a transparent green color. After your soap and water wash wipe the gelcoat down with some acetone and clean rags before you start sanding. I would not put this in epoxy before bodywork like i would a metal car. You want polyester to be bonded to polyester. Once you have all your body and glass work done then seal it all in epoxy.
 
There were a few spots...mainly on corners, that had a red substance on it that mostly came off with the power washer, but I also scrubbed those areas with acetone.
 
PVA is handy when working with polyester laminating resin. Apply it to a final coat of a lay-up and it allows the resin to harden through, IE, the surface won't be sticky for sanding. Wash off with water and grind or sand. Avoid using finishing polyester resin like many of the big box stores sell. They contain wax that is supposed to float to the surface so the resin will cure. Get some laminating resin from a boat or fiberglass supply.
 
One thing with fiberglass is that it continually shrinks to the hottest temp it gets exposed to. so a little sitting in the sun before and or after epoxy can help get it closer to it's final cure. If it sits till next year or later in epoxy primer, that's not a bad thing either. Just be sure to resand & get a fresh coat of epoxy on for best adhesion if it sits a while before continuing with any bodywork.
Epoxy primer builds strength in thickness, unlike 2kprimers, and some use just it for all block sanding for higher quality , though 2k primers for final sandings are fine.
Never tried the newer high tech fillers, but have been happy with the vpa stuff, sands like a thick high quality gelcoat. Any good glazing fillers are fine over epoxy for minor final filling, but I would do the heavier filling & adjusting first as recommended.
 
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remember when you were a kid they had those little kits in the toy store that had a little straw and some type of compound you would ball up, put on the end of the straw and blow up a bubble? thats pva lol.
 
Jim C said:
remember when you were a kid they had those little kits in the toy store that had a little straw and some type of compound you would ball up, put on the end of the straw and blow up a bubble? thats pva lol.
Click to expand...
Yes I am old enough to remember that.
 
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