No Gel Coat?

[Gary S.]

I read with interest the thread on paint problems that one of our members had and the responses to it. I also looked through the archives but I really need some clarification here. Some of you stated (Dale?) that St. Louis never used gel coat. I THOUGHT that all fiberglass had to have gel coat to seal the fiberglass strands in. I also THOUGHT that the Eckler's fiberglass repair book called for spraying gel coat on for that reason.

So if Corvettes never had and don't use gel coat and it is a PITA to use, we should be using Featherfill or something like it? I am asking because my neighbor and I are going to strip his 73 and repaint it now that he has a "reproduction" 454 back in his car. His previous paint job started bubbling up and blistering in sparsely scattered sections. This sounds suspiciously like the previous thread. My neighbor assumed it was because of a lack of gel coat. I told him I thought there might be some contamination on the body. Now I am confused (easily accomplished) about what to put down on top of the bare glass. He plans on spraying lacquer in the original color and doesn't want to have to do it again for quite a while. Gary 21316

[Patrick T.]

Re: No Gel Coat?

Gary, I had my '57 down to the bare glass, and had done of lot of body work. Even though it had dried out for almost a year, the painter would not guarantee the paint job without 2 coats of gelcoat. He said the reason for this is to seal in any loose glass strands and act as a permanent barrier of any noxious substances in the bodywork, which tend to go up through the new paint.

My '67 has a nice paint job,(the previous owner had it done) but it doesn't have a gelcoat and you can see the glass stand imperfections in some areas. Patrick

[Ed Jennings]

Re: No Gel Coat?

Gary, the term "gelcoat" is probably misapplied here, but I have seen photos of the workers making panels spraying resin onto the surface of the molds prior to the glass fibers being added. So I believe you are correct in that there is a layer on the top that covers the glass fibers. This may not be properly refered to as "gelcoat", but there is a strata there without glass in it. As I mentioned in one of the posts you were referencing, the glass fibers cannot be painted, no matter how smooth they may feel. There may be sealing primers available now that will outperform things like featherfill. I haven't done any bodywork or painting in 20+ years, so I'm not familiar with newer products. In any event, if the paint is blistering, there is probably some sort of contamination that you sure don't want to cover up again. Lacquer is pretty easy to spot in, especially if it's a solid color, but I can think of better ways to spend spare time and money.

[George R.]

Re: No Gel Coat?

Gary:

I had my 67 stripped gel coated with marine gel coat, polurethane primered, epoxy primered and block sanded in the lines. County Corvette I believe uses the same method. The gel coat keeps the moisture out of the glass. Imagine a fiber glass boat w/out a gel coat finish.

This is just the way I've always restored the corvettes and as far as the St. Louis Plant applications I can't give you an answer but have a memory of conflicting stories. There are a few members who know what the St. Louis Plant did.

Good luck,grr#33570

[Dale Pearman]

Re: No Gel Coat?

There are many good sealers (epoxy catalized) on the market that outperform gelcoat AND are much easier to use. Have a chat with your PPG automotive body and paint supplier and do the same with the Dupont folks. They will know a LOT more than most of us since it is their living.

Beware of firms such as Eckler's since their #1 goal is some of your $ in their till instead of a top notch paint job on your Corvette.

Gelcoat, a necessary polyester product when hand-laying fiberglass is similar to polyester resin and works just fine on Corvettes IF you want to WORK your a** off!. The original double press molded panel products for Corvettes did NOT have gel coat on the surface but they were rich with a mold release agent similar to polyester resin.

Dale.

[John H.]

Re: No Gel Coat?

Featherfill has been replaced by SlickSand, which, I'm told, does an excellent job of sealing the surface and building up over glass strands. I can remember watching A.O. Smith people at Ionia making Shark hoods, hood surrounds, and doors when I was trouble-shooting door inner-to-door outer dimensional problems - they sprayed a light coat of mold release agent on the upper and lower surface of the mold (which some folks may have misinterpreted as being gelcoat), placed the fiberglass pre-form on the lower mold, then poured the polyester resin mix all over the pre-form (from big coffee cans, although it WAS allegedly a measured amount of resin), then closed the mold; the upper mold, which formed the outer surface, came down on a huge hydraulic ram in a press until the mold closed, and the mold was opened and the part was removed about five minutes later. The part was then racked and moved to a secondary operation where it was trimmed, bonding surfaces were scuff-ground, and the show surface was cleaned with some chemical and lightly scuff-sanded. Then the rack went into a rail car and was on its way to St. Louis. At the time, this process was as good as it got. Later on, SMC (sheet molding compound) was used instead, which eliminated the pre-form and the resin-pouring operation, although it requires much higher press tonnage. Gelcoat is commonly used in hand-layup fabrication (like boat hulls and kit car bodies), but it was never used for Corvette parts which were press-molded in matched steel molds. Viper body panels are made today the same way the Shark panels were made, but now that process has a fancy name too - RTM, or resin-transfer molding (except the Viper hood, which is SMC - and is the biggest fiberglass panel in the history of the industry, with a 3-piece outer surface mold, which requires LOTS of hand-work and block-sanding to remove the mold seams from the show surface). Fiberglass panels are neither lighter nor less costly than steel - but the tooling to produce them is MUCH less expensive. Tooling investment is lower, but piece cost is much higher due to all the labor required to finish them. Been there, done that as the OEM - for 37 years (ending the day after tomorrow!)

[Juliet P.]

Wow! Great process...

...description John. Thanks. That's what makes this board great! I love the comparison between the Viper process and the C3 process. Something about Corvette '70s construction technology on modern day Vipers just sits right with this Shark owner! ~Juliet

[Russ Moen]

Re: No Gel Coat?

For whats it worth, i used gel-coat on my 66 four seasons ago and it still looks great. True it was alot of work (its hard to sand) but it goes on fairly thick so i had no need for filler. I blocked the gel-coat then primed, blocked some more, then painted. What sold me was a friend who has a 67 was haveing trouble with his hood "checking". He painted it several times, but the problem reoccured until he used gel-coat.It worked for me, but it sounds like other products work equally as well, take your pick.

[Ed Jennings]

Re: No Gel Coat?

So you're agreeing there is a layer of "something" on top of the glass fibers?

[Bill W.]

Re: No Gel Coat?

Ed the St louis plant did not use gel coat. they did not have a perfectly smooth body.they did show a small amount of glass texture after the paint was fully dried .they did have lots of waves in the body. they did show seams, the paint was thin ,dull, and full of orange peel.they looked bad !But thats the way they were! if you want to make your car better go ahead. but if you have a nice original body why screw it up by removing all the originality.you dont have to use gel coats and heavy primers to have a good paint job.

[George Skalkeas]

Re: No Gel Coat?

This gel coat discussion will soon rank right up there with the silicone brake fluid and slip-fit rear wheel bearings issues! If you watch the Eckler's fiberglass repair tape ole' Al Sowash is spraying away with the Eckler's brand gel coat. If you watch the the tape How to Paint Your Corvette, there's Al again but not even a mention of gel coat. Never tried the Slicksand but Dupont's Uro line of catalyzed primers seal the raw, fuzzy glass pretty well. In addition, Dupont recommends covering that good primer with a sealer prior to top coats - to ensure no contamination from below. (I don't work for Dupont; I'm in the middle of the process and just hope they are right)!

[Ed Jennings]

Re: No Gel Coat?

Agreed. IF you were to but look at the hood on my 67 you would see exactly what you describe! Glass fibers showing through everywhere. Funny, but that's the only place on the car this happens. The hood is an original APPEARING press molded part. May be a replacement that was manufactured differently, but when the car was strippped it looked just like the rest of the body. ????

[George R.]

Re: No Gel Coat?Thanks John for the history lesson *NM*

[Bill W.]

Re: No Gel Coat?

duponts uro primers and sealers work very well.

[George Daina]

They are right....

and os is FiberGlass Evercoat and any other manufacturer of catalyst primers. I sued Slick Sand by FiberGlass Evercoat, had seams showing and glass strands everywhere. Thought about gel coat, but the thought of all that work...NAW..no way, too lazy, so I ofter for Slick Sand. Best decision I ever made.

BTW, as The Dale said above, NO GEL COAT, but the stuff you see covering the glass is mold release/resin. One drawback with Gel Coat, it is weak, and with time will crack. Ever notice some of the spider web cracks on Corvettes? The mold release is cracking and guess what, now that you've sprayed a coat of Gel Coat, youve made the surface thicker AND weaker AND prone to more spider cracks. If your car is a trailer queen and won't see much of a road, you've nothing to worry about, but the ones driven, over time, will crack.