Gelcoat Cracking

[rt.collinsjr]

Hey all,

I have gel coat cracks that were not their on delivery. I had the body on a buck outside under a tarp last year and I think this is heat related.

What do you think, prep with sanding and fill with a high strength material like https://www.totalboat.com/products/totalfair-epoxy-fairing-compound ?

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Thank you.
Rich

[cob427sc]

Wow. Never seen that before. Looks like the gel coat lifted away from the fiberglass. Need some of the paint experts here to give you some direction. They may have seen this before.

[cc2Arider]

Most tarps don't breathe well. Was this in an area on the body that the tarps were in contact with? Heating or freeze/thaw cycles might explain it...

Craig C

[J R Jones]

That looks like heat or chemical related but not sun. IMO (not expert) that was too much activator locally, or too thick of material. Either case causes hot cure and dissimilar shrinkage.
Yes sand to the bottom of the fractures and build it back up. Totalfair epoxy looks very good.
jim

[rt.collinsjr]

When I first covered it, the tarp laid over the car and reached the ground - all around. During last summer, on a hot day, I become concerned that the hot air was trapped inside, under the tarp.

I checked and it was very hot, I touched the underside of the body and the glass was tacky - not good.

So I cut away the tarp so it would not reach the ground and it could breath. Noticed these cracks when I brought in the shop to start the body work this winter.

The only reason I covered it the way I did was to keep thee wind from getting under the body and going for a ride.

Rich

[rt.collinsjr]

It was in direct contact....

[BradCraig]

When I first covered it, the tarp laid over the car and reached the ground - all around. During last summer, on a hot day, I become concerned that the hot air was trapped inside, under the tarp.

I checked and it was very hot, I touched the underside of the body and the glass was tacky - not good.

So I cut away the tarp so it would not reach the ground and it could breath. Noticed these cracks when I brought in the shop to start the body work this winter.

The only reason I covered it the way I did was to keep thee wind from getting under the body and going for a ride.

Rich

I'd hit up FF and discuss, I can't imagine any reasonable amount of heat causing it to be tacky to the touch. If there was an issue with the curing or resin product you may want to figure it out prior to paint. I had mine outside under a tarp in NC during the summer without issue.

[Peter Ross]

There's a lot of gel coat porosity in the photo, zoom in. Water got in there, tarp trapped the water. At some point it froze, lifting edges.
Carefully sand the gel coat to glass with 80 grit on orbital sander. Avoid sanding the glass aggressively to avoid opening more pin holes. Treat the bare glass as you will the many areas you will sand through during paint prep.

[AA-ron]

I have a little fiberglass experience and I would definitely hit up FFR on this. Fiberglass is very temperature stable so even the heat under a tarp shouldn't affect it much-- and it should NEVER be sticky, as fiberglass is a "thermoset" composite. Basically, once its cured, it can't return to a liquid state.
Relating to the gel coat, we might be looking at a symptom a fiberglass curing too slow or too fast. I've seen pock marks (or porosity) like that and before and it related to the subsequent fiberglass coats curing incorrectly. My stepdad manufactured sailboat hulls, so I unfortunately spent a bit too much time around polyester resin and fiberglass and the itchy mess that follows.

[Hoooper]

Heat shouldnt cause this, a black painted car sitting in the sun will get the gel coat underneath at least as hot as it would get sitting outside under a tarp