Attaching hardware to fiberglass

[kingair]

I have several hatches that I want to add gas shocks to help with staying open. I am unable to reach the other sie, so I was thinking about using blind rivets. has anyone used these fastners? I need help with detrmining the correct length of rivet. I would imagine the material is about 1/8 inch.

[Wolakrab]

I have never seen rivets hold anything for long on a boat. Especially on something that's subject to regular use, like a gas support for a lid.

I would try to use regular self-tapping SS screws bedded in 5200 first, and see how that holds. If it doesn't, I would go to an anchoring system like a toggle bolt if you can't get in behind where you are mounting the shocks.

[ScarabChris]

There is another thing you can do if you are handy with working with glass.

Grind the gel coat away to bare glass where you want the strut mounted. Get yourself a small piece of marine ply and put bolts in it with the heads resessed. Put the bolts in so they line up with the mounting pattern of the strut. Then glass the wood block in with the studs sticking out. Now you not only have a solid mounting surface but you now have studs set in the proper position to mount the strut with a couple of nyloc nuts.

You could also omit the studs and glass in the block so you have some meat to screw regular screws into. But the stud thing will last longer.

[kingair]

Great ideas, thanks

[Chisox]

King,

The majority of gas shocks are installed (their mounting brackets) with #8 Panhead SS screws. Some call them self-tapping, but that is only true when there is coring behind the laminate.

Drill a 7/64" hole, and use 1/2"L #8 Panheads. There is no need to use longer, as the additional body of the screw has nothing to bite into. By using 1/2", you are only turning the screw the minimal amount it needs to seat. Longer screws equal a hole being wallered out (we use that word, but is it really a word?). Shoot some 5200 into each screw hole as well as behind the strut bracket. NOW HERE IS THE IMPORTANT PART! Install the screws with a screwdriver, not a cordless. Trust me, they'll maintain their bite a lot longer...

[Chisox]

There is another thing you can do if you are handy with working with glass.

Grind the gel coat away to bare glass where you want the strut mounted. Get yourself a small piece of marine ply and put bolts in it with the heads resessed. Put the bolts in so they line up with the mounting pattern of the strut. Then glass the wood block in with the studs sticking out. Now you not only have a solid mounting surface but you now have studs set in the proper position to mount the strut with a couple of nyloc nuts.

You could also omit the studs and glass in the block so you have some meat to screw regular screws into. But the stud thing will last longer.

Chris,

With struts installed like that, the boat could be run into the Hoover dam at 70MPH, the whole thing separate, but the shock mounts would still be attached to the fishboxes...

[Fishinspot]

Good ideas. I need to do the same fix.

[ScarabChris]

Chris,

With struts installed like that, the boat could be run into the Hoover dam at 70MPH, the whole thing separate, but the shock mounts would still be attached to the fishboxes...

Thats what I was thinking. When I smash my boat into a wall I want that damn strut to still be mounted to whatever hunk of fiberglass is left.

[kerno]

One of the problems with both blind rivets and self tapping screws is that both of them shatter the laminate as they are installed. I have attached many things to fiberglass by drilling and tapping the hole. Tapping cuts the fibers and does not destroy the properties of the laminate. If you install the screw with some epoxy, it is a stronger attachment than a self tapping screw. Blind rivets work best if they have a washer on the back side. The washer absorbs the force of their expansion and distributes the load over a larger area.

But for something like a gas strut, a tapped hole is not going to last. Glass a block in place as suggested. That way, if you do meet a large concrete structure at 70 mph, you'll have time to say "Dam" before it fails.

[WalkaboutNC]

I've had success attaching to "blind" fiberglass - where I didn't want to drill all the way through - with a variation on Chris's idea. 3/4 marine ply - painted with Brightside polyurethane - rough up the glass area and then bond on the plywood with 5200. (I didn't paint the wood where the 5200 was). I don't think you could get it off without ripping apart wood or glass - or both. You could do this with Chris's stud suggestion and be fine.

Reel Tight Lines!