Dave Frazer

While I have good experience with body work, fiberglass is a little new to me. the repair process is straight forward and would like to learn more about gel coating.
I have stripped the car down to the glass and repaired the cracks.

Can someone explain the basics of gel coating and blocking it?

I will be either rolling or brushing it on, not spraying.

Thanks,
Dave

dmaxx3500

these cars were ''NOT'' gel coated from the factory

Dave Frazer

I understand that. I am working on a Daimler SP250 which is a fiberglass body gelcoated and thought I could tap into someone who understands the process on this forum.
Thanks,
Dave

DUB

Sorry. I only spray on gelcoat. I do brush it on the molds I have in certain areas when making a part. I never tried to roll it on but I am sure that of you test it out adn see how well it applies due to its viscosity...which may require you to add a little bit of acetone to it. It will have a lot to do with how much you apply and then allow it to flash off so you can apply more and hopefully you do not get the 'gatoring' effect where it want to wrinkle up.

And knowing GM never applied it on the body for obvious reasons of slowing down production time and costs associated with that ....does not mean it is still not a very good material to use and an OPTION other than 2K primers of today.. Because with that type of mentality that just becasue GM did not use it....then everybody needs to be using lacquer primer....which we all should know by now is rather out dated.

DUB

porchdog

gel coat saved our *** back in the lacquer days. only way to hold down repairs or they would ghost bad.
rolling is going to be tuff . kick time and such will need to be considered. only time i ever did it i had someone else mixing while i rolled it. a cheap 2qrt pressure pot would be a better way to go .

Dave Frazer

Originally these cars (much like Corvettes I suppose) had no gel coat. Just styrene resin and glass fibers.
Since I have it sanded down to the glass I wanted to seal it. I have read arguments for epoxy and gel coat.

I have also read to skim it with fiber fill and block it fairly flat before the gel coat.
Once the gel coat is on, block it again and then proceed to an epoxy primer. Sounds over kill to me but this is my first full fiberglass resto and am looking for a process that will yield good long term results.

I can spray the gel coat if that method is preferable.

Dave Frazer

I plan to start with the hood and trunk lid to learn the nuances. Do you let it flash off between coats and if so, only mix enough for one coat at a time?

csherman

I would polyester prime it and I think you will be happy.

Dave Frazer

I think the process will be:
1) Strip remaining paint down to fiberglass.
2) Do any needed repairs.
3)Apply gel coat to seal it and block sand the gel coat.
4) Apply polyester primer.

Make sense???

Dave

DUB

YES...ONLY mix enough gelcoat for what you plan on using due to any you have left in the paint mixing bucket will inherently want to cure faster due to the internal heat being built up during the activation process. So the left over gelcoat can rock up on you rather fast.

DUB

BigBlok502

It's been years since I sprayed gel coat on my '71 that is my avatar and here are my tips:

Keep some acetone handy for cleaning the spray gun, and clean it immediately after spraying or you will buy a new spray gun.

Back in the day there would be a wax substance that came to the surface to seal the gel coat while it was activating. Clean this off after the gel coat has cured before sanding, otherwise it will gum up the sandpaper. I used the acetone to clean the wax substance off.

JBL Specialty

I use un waxed gelcoat. After I finish spraying gelcoat I spray on pva to get a slight green color. Let the gelcoat cure overnight and rinse off the pva with water. The gelcoat can then be sanded without clogging the sandpaper.

Dave Frazer

How long do you wait after you spray the gel coat to apply the PVA and where would I purchase the PVA?

Dave

JBL Specialty

You can get pva and un waxed gelcoat form any fiberglass supplier. I get the gelcoat in 5 gal pails for about 150.00 and pva is around 30.00 per gallon. I use white gelcoat and spray pva on as soon as I finish spraying the gelcoat. It should be ready to sand the next day. I don't know where you live but I get mine Eastern Burlap in Norfolk Va. They can ship it to you.

DUB

I let the last coat of gelcoat flash off for about an hour or so or until I see the gelcoat go some what dull.

I use black gelcoat so it is easy for me to see it. And blocking it is really easy due to blocking on black ...tit shows you darn near instantly the change in the finish so you can block it out rather fast.

When I apply the PVA...I do not soak it on due to it being like water. I dust it on and let it flash off and go over the car several times...and when I lightly run my finger across an area that I know the gelcoat would stick to my finger...if my finger glides across the surface. Then I know I have enough PVA on the gelcoat so it is sealing it from the outside air so it can cure.

You can test this by trying it on some of the area where your gelcoat is on some masking paper where you have masked off the car....then try it again when you know you have applied PVA on that area....you will see what I mean when you try this. Because even though the gelcoat has flashed off and looks somewhat dull it has not cured and it can be rather tacky or wet.

DUB

Dave Frazer

Can you apply the PVA with a spray bottle and mist/dust it so it doesn't soak it on?

Dave

JBL Specialty

Sure, but you need to put enough on to form a film to seal off the gelcoat from the air. Apply freely it takes a fair amount.

Dave Frazer

Hood and trunk now stripped down to bare glass. Previous owner left it outside for years.
Lots of sun damage and stress cracks. What a mess. If I grind the cracks, not much will be left.
Do repairs and new layer of glass on entire surface?
Dave

JBL Specialty

You probably should post a few pictures of the parts so we can see what it looks like and does it have gelcoat on it from the factory. You could repair it the way you mentioned but to work good the existing gelcoat would need to be sanded off. I would apply 3/4 ounce mat in one sheet and use unwaxed tooling resin. Be sure you wet out the mat and keep it as smooth as possible. Once it kicks off it can be skimmed with plastic and blocked flat. There are a lot of ways to repair your parts that will work fine.

DUB

I honesty do no think that these panels have factory gelcoat on them....if they did....ti would be a first.

I am aware of the stress cracks you are seeing.....but good photos can be helpful. Some of them being close-ups a while other photos being further away so we can bet an idea where the problems are located.

I do no think I would use 'tooling resin' for repairs It is called tooling resin for reason. I knwo it is much thinner and more watery than the other resins...but that does not make it be the best choice. I would not do it myself... but I know people have found ways to do things that seem to work for them.

When you have ground on some of these cracks...how did the fiberglass react?? Did pieces of it fly off in chunks or pieces like if it where a jig saw puzzle and left exposed fibers???

DUB