Screwing into fiberglass?

[RayH]

What is a good method of attaching to fiberglass, i.e. emblems, rub-rail, misc hardward? Standard wood screws or sheet metal screws works loose, creating a bigger hole.......

Thanks...

[Reese]

this is straight from So-cal...screws of any type are popular to use with boat builders because they are fast to use and cheap, but like you said over time the will work themselves loose.

Order of the most effective method to mount emblems, rubrails and anything else to glass are:

1. Stainless Steel Nuts and Bolts

2. Aluminum rivets (can be ordered in different colors).

4. Bonding adhesives

3. Screws, wood or metal doesn't matter much.

BTW, this is the reverse order for time and cost...but if you want a bullet proof mount you need to use either 1 or 2.

[H2Onut]

Put some adhesive or selant in hole when they are virgin, I used epoxy resin to dunk the screws in. and syringe to inject in hole

[Techno]

Rivet nuts. They are a rivet that has an internal thread in them. You use a Rivet type tool to collapse them onto a thin material just like a pop rivet. Then use a machine screw type threaded screw to attach whatever.

http://www.mcmaster.com/param/images/nutinserts/rivetnutsb.gif

put the page number into the search box.
page 3040 (http://www.mcmaster.com/)

Few types including studs so there are a few pages.

[RayH]

Hey Techno, just checked out the web-site, I like the rivet nut idea. Have you ever used them? When crimped does it break the fiberglass, i.e. stress?

[Tom D.]

I had the same problem with my Checkmate when I first got it. I had some 1/8" thick 1/2"X1/2" aluminum angle and cut a bunch of about 1/2" pieces. Drilled a hole small enough so that a sheet metal screw would make its theads in it. I put them in a vice first to do this so it would be easier to thread. I'd drill an other hole on the other side big enoufg for a ty-rap to ty wires or hoses ect. Some of them you need 2 people to do this. So I'd put them in a pair of vice grips and have one of my boys hold the angle peice up ther while I screwed the screw in. I did this on my deck rails and the are solid.

Tom

[Techno]

Used them on my boat where I could have through bolted and in the bow where I couldn't. Also used them to mount a stereo rack in my Vette, again where I couldn't get to the back side-glass.

They don't seem to stress the glass but I wouldn't depend on them for incredible holding power. They do grip better than a few threads of a metal screw though. They also protrude above the surface like the finished side of a pop rivet. They seem to have a better hold than a pop rivet since the back side rolls flatter and you tend to use a larger rivet than a pop rivet would be.
The crimp is with a rivet gun that has a threaded arbor on it. Instead you tighten it until it's good then unscrew the tool. If you break the threaded tool you buy a new threaded arbor. Different than a regular pop rivet tool, you tighten as much as you want. Probably could be done with a screw and nut instead of the tool but much slower.

[Ronny Jetmore]

wet out the holes and the screw with epoxy then tighten. make sure all surfaces are clean. if you need to get the screw out at some point, hold a soldering iron against the head, this will soften the epoxy enough to cause it to release. this works, west system recommended this. by the way, use stainess when doing this. thanks

[Liqui-Fly]

Screws always seem to back out on anything I've ever used them on. Things like emblems would probably look and work best riveted. The only other thing is through bolting with nylock nuts.

David

[CrayzKirk]

If you can get to it, a piece of 1/2 plywood with hole drilled for stainless machine screw, washer and nylon lock nuts works well. Coat the plywood with thinned resin to seal it from moisture. Fiberglass isn't very strong at resisting tears and pullouts. You have to increase the surface area under tension. Any sort of backing plate will increase the resistance to pulling out of the glass.

It's what I've done for stripped screws on my old heap. Dipping screws in Epoxy before inserting will also help protect the wood and prevent the nut from backing off. A little heat on the head of the screw will soften the Epoxy and let the screw come out again.

Kirk

[Scream And Fly]

No matter which method you use (I prefer thru-bolting myself), always countersink the hole with a countersink taper bit. This will prevent stress cracks from forming in the gelcoat around the fastener.

Greg

[Forkin' Crazy]

For structure, there is no replacement for though bolt and nut.

My Checkmate came with plastic nuts and sheet metal screws for the grab rail. That worked really well. There is enough screws to distribute the load and plastic is cheap and does not rust.

Rivnuts are good where you cannot get to the backside, but may have to have a counterbored hole to be flush.