Fiberglass work...your experience.

[njpatera]

Greetings All...I started playing with the resin and fiberglass and I'm looking to hear from your experience. I'm use to prep sol and thinner to prep and clean metal bodies for paint so stepping into the world of fiberglass, I want to be sure Im schooled as much as possible. I've watched a ton of how to videos( most show the work and not much of the prep ) and everyone knows great work results in failure if the prep is subpar...my local auto body buddies have had minimal work on new glass bodies and I remember reading new glass is quite different from the '50s....after that epic tale, my question is to those of you that have done the glass work, when cleaning before work do you use the suggested soap and water and/or acetone or did you utilize lacquer thinner.? After reading one of the service bulletins it said to treat body work the same as lacquer to metal bodies, but it did not indicate prep work. My thoughts(right or wrong) was prep sol and thinner to the sanded fiberglass would subject it to absorb the chemicals and interfere with resin adhesion...I just can't see soap and water or acetone being the final step before resin/matting application. What say you?

[DTort96646]

When working with the old fiberglass, remember that it was shot into molds from a chopper gun and not hand layup fiberglass. The mix was resin poor in a lot of areas and very porous. When I redid my Darrin, everything was kept dry, no water, no soap or detergent. A vacuum, a scrapper, sandpaper, and compressed air are what I used to shape and clean the original coating and undercoat from the body. I disassembled the body into it's main components, and refiberglassed each piece inside and out before reassembling the total body. I used acetone as the final solvent before applying resin and fiberglass to the panels. I also added a small amount of acetone to the first coating of resin to thin the resin so it would soak into the original fiberglass and seal some of the porosity. I used fiberglass cloth on the underside for strength, and fiberglass mat on the outside to finish over the old fiberglass. The outside surface "gel coat" was sanded away and replaced with fiberglass mat. I used polyester resin with the fiberglass during this procedure. I used epoxy resin when bonding the panels together along with a thin strip of fiberglass cloth soaked in epoxy resin between the panels, and then used stainless screws, washers and nylock nuts replacing the original screws and nuts. I used epoxy primer to coat all the fiberglass after sanding to shape and before using any bodyfiller. All the body panels were fit, filled, and sanded   before the final coats of epoxy primer were spayed on. I did not use any gelcoat or any spray on resin. Only epoxy primer before the final sealer coat and acrylic lacquer was used. Also, and this is very important, I sealed the inside of every panel with epoxy primer and paint, and the underbody is sealed with undercoat. There is no chance for any moisture to migrate from the inside under the paint to cause blisters or peeling. It's a lot of work, but I was only going to do this one time. I painted my Darrin in 2008, finished the restoration( upholstery, top, carpets, assembly etc) in 2010. I have been driving to shows locally and to some Northeast Concours shows since 2011. I drove to the Gettysburg National from Massachusetts and more shows after that. The body and paint still look as fantastic as when I did the final polishing in 2010.

[Terry T]

Congrats for explaining a difficult task and for adding the undercoating which was as original.

Many will remember that I was kicked in the butt for years by many "old timers" in this Club for stating that my original unrestored car had "factory" undercoating.
For decades, the club judging subtracted points for undercoating since it was believed that all undercoating was done by a dealership.

This controversy was talked about 30 years ago in the Darrin newsletters.  Carl Rhodes had disagreed with Andy Schroyer who did not believe in the undercoating.  Carl had warned about bubbling of paint on the top of the fenders due to migration of moisture.  Andy took off the undercoating and sadly experienced the prediction. 

[joefrazer]

That was Ellis Rhodes. He and I were friends and I recall a conversation about undercoating. He said he talked to a couple of the guys who worked in Jackson and were part of the body assembly process. He described the undercoating application process as hit or miss, meaning that while it was applied not every body got the same treatment. So, all these years later we see the results.

[Terry T]

I stand corrected.
I guess I have been watching too much political news.

[njpatera]

DTort....thank you soooo much! That is exactly the guidance I needed! Ironically, I just sold some parts from an old 56 Vicky parts car last night and the guy has been in the marine industry for a long time. I got virtually the same info as you explained. Since he is a motor head too, he got into what products of the marine world and auto world are cohesive and to not use gel coat:-) I got more than what I needed about the different poly resins(laminating and finishing) and the epoxies...he gave me one good bit to remember...

You can put epoxy over polyester, but not polyester over epoxy...reminds me of the lacquer/enamel battles.

[MarkH]

Never worked on a Darrin but have done glass repair on a few boats, and some metal bodywork.

Some may disagree but I've always thought Prep-Sol left a film. If you can smell it, something's gotta still be there. I certainly wouldn't want it wicking into glass fibers and hoping for the best as it "cooks" out later.

As stated above, acetone is the way to go. Cleans nice and vanishes without a trace at any temperature, even if you over do it.

Ditto on the moisture & blistering.

[njpatera]

@MarkH... I agree prep sol leaves residue behind. I always followed with thinner and you would see it:-) It's pretty interesting to learn how greatly different the glass prep is. Just need to remember the respirator and tyvek suit:-)

[DTort96646]

Pre-Sol is used to dissolve and keep the contaminants suspended in the wet solution until wiped away. Pre-Sol has some petroleum base to it. Acetone will dissolve contaminants especially oil and grease and the oils in your skin. Acetone also will dissolve some of the resin and promote good adhesion. Also, the reason for fiberglass mat on the outside surface is to prevent "print through". Print through is when the pattern of the fiberglass cloth shows in the surface as the cured resin changes temperature. The fiberglass and the resin do not absorb heat at the same rate. In the hot sun you will be able to see the fiberglass cloth's weave in the paint. It's minor but it's noticeable. The fiberglass mat is random and you will not see the glass strand's pattern in the paint. Next time you are at a car show and you admire that fiberglass repro 32 fiberglass Ford body ( or any other repro fiberglass body that is hand layup) look real close at the finish and you will see the cloth pattern. Along with the respirator and Tyvec  overalls, latex gloves when mixing and applying the resin and fiberglass. Also a serrated roller to smooth the air and excess resin out of the fiberglass as you apply it. Nothing worse than having an air pocket in that beautiful layer of fiberglass that is on top of the fender of hood.

[njpatera]

Great explanation and pointers! Most appreciated:-) ...and I now I will never look at another 32 the same...haha