Screwing into fiberglass

[autopro]

If you are really worried about the screw stripping out then you can use any of these for the front bumper grills:

The first picture is what I use on my fiberglass motorcycle racing fairings.  They are pretty thin compared to the bumper and I have never had one come out.  They are made of rubber and have a nut inside of them.  When you tighten the screw they expand and hold firmly.  When you remove the screw they retract and you can then remove them from the part if you want.

The second one will work well also, but I would use a metal screw instead of the plastic ones they come with.

The third one is more for use in sheet metal and would require a square hole.

[autopro]

You won't be able to use that clip in the front bumper grills, but it will work on the rear were you have tabs sticking out.

I've looked at the front bumper grill installation and all I can think is that they just screwed directly into the bumper themselves.  Diagrams show no clips for the front grills.

[LamboJayso]

I get how those fasteners work autopro, but how do you slip those over the small holes you screw the grills in to?

[autopro]

I use different styles of fasteners, here is an example of what I like to use.

[BigPines]

Glassed-in metal is safer but if as you say the item being attached is light weight, I don't think there is anything wrong with using a screw directly into fiberglass. If the resin and glass material is thick enough, it should hold great. So if it looks good and seems stable, I say do it.

[LamboJayso]

When I attach certain parts like grills to the front bumper, I like to back it with metal. Is this really necessary though when attaching lightweight things like grills? I normally use self tapping metal screws but I've heard wood screws work great with fiberglass and it doesn't eat away at the fiberglass over time. How do you other builders do it?