Bolt for pop top support strut

[dyelaine]

My new (to me) Catalina 22 is missing a bolt for one of the struts (starboard) that hold up the pop top.

The problem:
It appears that the bolt "screws" into fiberglass (not into a nut or into metal) and that the "threads" of the fiberglass are stripped.

Details:
One end of the strut is attached (with a pin) to a bracket mounted to the pop top (the part of the deck that raises). The other end of the strut uses a bolt that screws into the side of the cabin top. The bolt that goes into the side of the cabin top uses machine thread and has a Phillips head.

When I tried using the port side bolt in the starboard hole, the bolt didn't tighten up. From what I can see, looking in the starboard hole, it looks like there is no nut. It looks like the bolt threads into the fiberglass that constitutes the cabin top (approximately an inch thick). It looks like the "threads" in the fiberglass have been stripped.

Questions:
1. Am I right that the bolt holding the strut end goes into fiberglass, or is there metal in there somewhere?
2. If the bolt threads into fiberglass, what is a good way to make a repair so that the bolt will hold the end of the strut securely?

Thoughts:
1. I'm hesitant to try filling the hole with epoxy (or whatever) because it seems like when I re-drill a hole for the bolt, there will be very little epoxy left. I suppose I can drill a larger hole and fill that with epoxy so that the "threads" are in totally new epoxy, but the large hole will be nearly as wide as the roof is thick -- it seems like drilling a larger hole will weaken the cabin roof.
2. I would like to find some kind of metal insert or sleeve that will hold well in the fiberglass AND provide metal threads for a bolt.
3. If I had such an insert, I could use the current hole for the insert and then use a smaller (thinner) bolt.

 

[Johnb]

Google "bolt insert" and you will find a wealth of possibilities - sizes and materials. The good news is this kind of repair has myriad solutions.

Post some pictures.

 

[heritage]

It's common for builders to embed an aluminum plate in areas where winches and stanchions will be screwed down with bolts. If that is the case with your pop-top strut, I would tap new larger threads into the metal. If there is no metal, use one of these for the job.
E-Z LOK Self Locking Thread Insert: Thin Wall, 3/8"-16 In

 

[dyelaine]

I made the repair with an aluminum shim. I cut the shim from an old license plate (maybe a millimeter or two thick). Because the hole was stripped wider near the opening, I cut the shim in a triangle. I thought I would use a shim on each side of the bolt, but the hole wasn't wide enough for both shims, so I only used one. It's hard to see in the photo, but I tapered the end of the bolt so it would start more easily.

I had two bolts - one with a hex head and one with the normal Phillips head. I put the shim in the hole and bent the tip of the shim to keep it from sliding in. I placed the shim on the side of the hole rather than on the top or bottom so the pressure would be horizontal (toward the thickest side of the fiberglass). I used the hex head bolt (also tapered at the end) to get started because I could put more pressure on it and keep it aligned with the hole. After I got the hex head bolt about halfway in, I unscrewed it and used the Phillips head bolt to finish the job because the Phillips head matches the other strut bolts. When I unscrewed the hex head bolt, I could see that it had cut or pressed nice threads into the aluminum shim as well as into the fiberglass of the boat.

The bolt tightened up very well. (The photo shows it before I tightened the bolt.) I raised and lowered the pop-top several times successfully.

Note: I had planned to use epoxy on the fiberglass side of the shim, but the bolt held so well, I decided not to mess with epoxy.