How can I tighten a loose screw in fiberglass side?

The typical filon wall is made up like this:
1/16" filon
1/8" (or metric equivilent) luan ply
foam
1/8" (or metric equivilent) luan ply
Sheet metal (exterior)
vinyl (interior)

I cut a chunk out of the apron to install a hatch, here's the leftovers:


Note the luan on the back of the filon was originally part of the luan on the expanded bead foam - they've been split in this image.

it is a wonder they hold any screws. If I had the issue, I'd do what Joe417 did - remove the vent & add backer wood to give the screws something to hold onto.

I've used broken off golf tees when the hold was too big for toothpicks to get adhesion.

My only issue with nutserts is that sometimes they can wind up spinning in their socket, making it impossible to insert or extract a screw or bolt. I've mitigated this with metal to metal connections by using a little bit of LocTite Red where the two areas contact, but for the screw to Filon, it may require using a nutsert and some epoxy so it stays in place.

Adhesive caulk will hold it. Not a lot of stress on it in that situation and you can still get the screw out if you need to.

Joe417 wrote:

I've also removed a loose fixture, carved out the foam insulation, and installed the appropriate sized wood framing around the opening to give me something to screw to. That takes more effort but is probably the best method as it will probably last longer.

This is how to fix it- the vent has a large opening, and you really need to remove it for any good fix, so why not fix it right, and for good.

When my outside grab bar came loose I used Marine Tex. I filled the holes then drilled a starter hole then refastened using the original screws. That was 4 years ago, still holding

I've used nutserts, you have to install them carefully as the filon is so thin.

The fiber glass is glued onto 1/8" or 1/4" plywood. If the wood chips out and there's no framing where you need to put the screw, Lowe's sells metal wall anchors that you put in the hole and tighten the screw to crimp the anchor into the wall. You then remove the screw and put the vent back in with the screw that came with the anchor. How well they holds depends on the condition of the rest of the plywood around the hole.

There are different lengths for different thicknesses of wall.

I've also removed a loose fixture, carved out the foam insulation, and installed the appropriate sized wood framing around the opening to give me something to screw to. That takes more effort but is probably the best method as it will probably last longer.

I've tried toothpicks in the hole beside the screw. It held for a little while. The filon is what 1/8" thick? Part of the problem is that the hood exhaust vent is I think two piece, with the outer piece being more of the cover/seal piece. To use the blue inserts or a helicoil, wouldn't I have to take the whole unit off? TIA.

Mmwtdh wrote:

They are called plastic anchors and come in several sizes You can get a set of these at Lowes (and most hardware stores)with new screws.