Primer on Fiberglass Fix?

[mfleming]

Recently I sanded and primed my cowling with a 2K epoxy primer. Apparently I was over aggressive when sanding. The fiberglass cloth weave is showing on a fair amount of the cowl.

My paint shop told me "rough sand the fiberglass and apply a 2K primer and they will make it pretty". So, really the primer is acting as a sealer until it gets to the paint shop. Protection from oil and dirt....

My concern is, do I need to do something to preserve the integrity of the primer as a sealer or is it protected from contamination as is?

[Carl Froehlich]

You were not ready for prime. Much more body work needs to happen. I suggest you work it out with your paint shop on who will do what. If they are doing the body work they will again sand. I suspect you can just light sand and shoot another coat or two of primer if you have bare spots.

Not familiar with 2K primer. Is it UV resistant?

Carl

[mfleming]

Originally Posted by Carl Froehlich

You were not ready for prime. Much more body work needs to happen. I suggest you work it out with your paint shop on who will do what. If they are doing the body work they will again sand. I suspect you can just light sand and shoot another coat or two of primer if you have bare spots.

Not familiar with 2K primer. Is it UV resistant?

Carl

You're very correct about not being ready for primer as far as final paint goes. This primer is really just protection from oil and dirt until the AC reaches the paint shop.

[PaulvS]

The surface in the photos appears porous so contamination will likely get in.
It doesn't look like the primer has sealed because the surface was too rough for primer.
Probably a brushed on coat of epoxy resin would've been a better sealer if the shop is going to do the bodywork filling and block sanding.
As to the fix now, like Carl says it would be best to talk to the paint shop but I think it will need filling before sealing.

[Bandera]

No worries with the primer but now there is work to be done. What you can see now is where every pinhole and void is located. Fill them, sand it smooth and prime again. If there are no pinholes this time, sand it smooth and paint. If there are pinholes, fill again and prime. Sand it smooth and paint.

A complete set of fiberglass parts takes me 2.5 days start to finish.

[wirejock]

I am a hack, but I get really lucky.
Dan Horton method with minor deviations. I spread micro, sand flat then a coat of neat epoxy. Sand that flat then two brushed coats of 2K epoxy primer. Wet sand that flat and there's almost nothing left to seal. The parts look like heck but they are smooth as a baby's bottom. At that point I shoot primer. If there are any imperfections, they get a tiny smush of glazing before the final paint.

Honestly, I think it's fine if you patch the area with some 2K primer. That's what the paint shop recommended. They will sand it anyway.
Again, I know nothing!

[PhatRV]

Originally Posted by mfleming

Recently I sanded and primed my cowling with a 2K epoxy primer. Apparently I was over aggressive when sanding. The fiberglass cloth weave is showing on a fair amount of the cowl.

My paint shop told me "rough sand the fiberglass and apply a 2K primer and they will make it pretty". So, really the primer is acting as a sealer until it gets to the paint shop. Protection from oil and dirt....

My concern is, do I need to do something to preserve the integrity of the primer as a sealer or is it protected from contamination as is?

I have a lot of pinholes when I primed the fiberglass parts. I was successful at using the high build primer which is layed up thicker than the regular epoxy primer. Then you sand down most of it away. The high build primer covers up all of the tiny pinholes and sanding imperfections. Then you can spray epoxy primer on top of the surface to seal it or just spray paint on top.