How do you repair stripped fiberglass screw holes?

Metric Rivnuts is one way to do it..

 

Can probably use same techniques as boat repair. This is a pretty good link for a lot of info and techniques.

WEST SYSTEM | Projects | Fiberglass Boat Repair & Restoration - Repairing machined holes in fiberglass

 

Use a helicoil. Install it the same way you would in metal with one minor addition: After drilling/tapping the FG, put a dab of epoxy on the outside of the coil and on the tapped hole in the FG. Screw a greased screw into the coil and screw the coil into the FG. Remove the screw after the epoxy has set. The greased screw prevents any epoxy from leaking into and obstructing the helicoil threads.

I've done a ton of them in that way in FG/carbon fibre. You will have a much stronger threaded joint as opposed to the oem method of screwing something directly into the FG/Fibre.

 

Another way would be to make up some smallish squares of galvanized sheet metal, predrill them to be just large enough to start a screw then have the screw tap the sheet metal, then epoxy the piece to the fiberglass so the screw location is identical. You could use some self-tapping screws to make the threaded hole in the sheetmetal, then use the same original screws (or matching new ones) for fitting the panel. If you want the patch to be flush you could lightly grind the surface of the fiberglass to do that. The advantage of this method is that a much larger surface of patch is bonded to the fiberglass, not just the perimeter of a helicoil or some other proprietary threaded bit. Easier to fit, too. So long as you don't overtighten the attaching screw & strip the new metal it should be more than strong enough. Practice on a piece of the same gauge sheet metal on the bench to see how much it can be tightened without either stripping the screw or sheetmetal repair patch. Remember, preparation is everything!

Cheers,
Rich

 

If it's thin panel thickness and you can get to the other side easy, I would go with nutplates riveted and a little epoxy.

If it's thin and you can't get to the backside go with rivnuts. Again, a little epoxy helps keep it permanent.

If it's solid and not like a panel such as the wheel well area helicoils or keenserts, like Mike says above are the way to go. They make oversize inserts if the hole gets augered out too large by the old fastener.

 

I had the same problem - used speed clips. I think that's what they're called - a sprung steel clip that slides over the edge of the panel with a pressed hole to take a self-tapper on the underside. Just align it with the old hole.