Need help with fiberglass ground effects...

[wolfsautobody]

I am installing a fiberglass ground effects kit on a coworkers 2001 Honda and have ran into some problems. First off... the kit he order was a piece of crap and now I am having problems installing it. I am working on the rear bumper right now. The body lines didn't line up good so we decided to mold it in to the quarters. After making a few cuts and trims here and there it looks pretty good, BUT after I primed it I have been having problems with it. I sanded the whole bumper down with 80 grit before I primed but there are some places where the primer is just peeling off. And after I primed I also noticed some places where the fiberglass had air bubbles and it is bubbling the primer. I took a razor and cut the places out that bubbled up. It seems like the more I sand it the more bubbles pop up. I added some short hair fiberglass to the places that I cut out and re-primed the bumper and noticed more places bubbling so I cut those out and am going to try and repair them tomorrow. My question... would finishing putty work in these places or does it need to be fiberglass? And what would cause the primer to not stick to the primer that came on the pieces? There was a couple places that I tried to sand the primer off with my air grinder and ended up going through the fiberglass. I used Evercoat lacquer primer on the pieces, maybe this had an effect on the primer that came on them.

[Hannibal]

are you wiping the bumper down? You may feel that you have got all the dust out, but the static electricity when wiping down that bumper has got to be strong. YOu would need to wipe off with an antistatic rag or something (unscented woolite antistatic sheet).

These were my first thoughts, from working on gel coats and boat finishes.

[Len]

Are the defects in the primer or are they in the fiberglass?

[wolfsautobody]

It appears that they are in the fiberglass. What ever type of primer they sprayed on was kinda thick and it didn't show the air pockets until I started to sand the primer off a little. But it is a white primer so I didn't notice until after I sprayed a gray primer on it. But when I took a razor to it to cut the bubble out then there was a hole behind the bubble.

[Len]

Having air pockets in the fiberglass usually means you have a cheaply made part. This can be quite difficult to repair because those bubbles can cause problems later. I would probably fill the exposed holes with polyester putty then spray a polyester spray filler or (better yet) a gel coat over the entire surface and hope that it keeps the air pockets from breaking through the surface later. The biggest problem I find is that solvent can get into these voids and weaken the surrounding material and allow the surface to bubble caused by the air expanding and contracting as time passes.