Rivnuts

[SilverBeast]

Has anyone used rivnuts in fibreglass?

I'm refitting the door cards after cleaning the vinyl, with new spring clips and the plastic socket.
I'll be using therivnuts in the metal plate that the inside door release mounts to (so I don't have to hold a nut/flattish spring plate thingy for self tapping screws) behind this while putting it back together. I'm also considering using them for the two screws that hold the padded flat metal plate that is the door pull handle. This will help retain the skin on my hands instead of coating the inside of the door as I try and contort it into the door recesses!

I have both steel and aluminium rivnuts available. Not having used them before I'm concerned it may just crack/splinter the fibreglass. Can they just be used straight into the fibreglass, or would I need to fit some sort of washer/plate behind them?

If I am successful I may also use these to mount the wing mirrors and wheel arch closing panels as well.

[Clifton]

 I think rivnuts might be to much for fiberglass but I've never used aluminum, only steel ones. I have used jack nuts on fiberglass and plastic. They don't sit as flat though. This is the style I used
https://www.hansonrivet.com/threaded-inserts-2/jack-nut-threaded-inserts/

[BDA]

Sure! I don't think I tried any larger than #10 and I think I used aluminum ones though steel ones would probably provide better grip on the fiberglass. I did not use then in any really stressed applications. In my case, I was mounting hose clamps on the back of the car (inside the license plate area). I constructed a fiberglass box that I installed the rivnuts in and then glassed the box to the inside of the rear of the car. This way I wouldn't have to drill through the body. It seems I did a similar trick somewhere else but I don't remember now.

I may be too cautious but I don't think I would advise using them for mirrors but the fender closing panels is a great use for them.

A washer on either side of the fiberglass might be a good idea if the grip length of your rivnuts is long enough but I didn't use anything like that. BTW - I am pretty careful when I screw and unscrew in my rivnuts because I REALLY don't want them to pull out.

If you have a piece of fiberglass sheet, you might experiment with it.

[4129R]

I have only used rivnuts to hold the top 4 holes of the dashboard.

I have found the fibreglass has been badly cut during manufacture, so I have made steel L brackets pop riveted to the fibreglass.

When using pop rivets, I use washers to spread the load on the fibreglass.

Rivnuts are just big threaded pop rivets, so I have used the correct sized washers behind the rivnuts so they crush the washer, not the fibreglass.

As a word of warning, unless the rivnuts are very tight in the holes, they will just rotate when you screw into them, so use spreader washers, and make them tight when inserting them into the holes. 

[SilverBeast]

Thanks for all the feedback/tips

[jbcollier]

I used rivets in fibreglass.  Lots of cracking sounds so I wouldn't do it again.  Next time I'll use well nuts or nut plates:

[Gary t]

Nut plates are the best, you can get them for machine screws or self tapping screws. They are the best blind screw anchor.

[Pfreen]

I have used aluminum rivnuts many times in fiberglass.  You must not over squeeze them but they work great for what I used them for.  I have not used them in the door though. 

[kram350kram]

I've used steel rivet nuts in fiberglass many times with no issues. I add a drop of red Loctite for added insurance and or a steel washer under when the glass is very thin. All have held under repeated use.

[GavinT]

Yeah, I rather doubt rivnuts will hold properly in fibreglass - the crimp area perimeter is just too small and the very nature of pulling them up just shatters the fibreglass resin.

For these light duty applications I'd just put a rivnut into an ally strip and use builders construction glue to afix that to the location from behind. That "liquid nails" construction glue is tenacious stuff and well up to the job.

I use a hole saw (sans the centre drill) in a pedestal drill to make the ally 'washers' for jobs like this.

[dakazman]

   I have used many types of rivnuts mentioned above . The washer method last the longest. The nut plate is a favorite of mine , working with thin sheet metal.  Rubber nuts , cosmetics use only.
   The use of these inserts, epoxied or glassed in work very well for repetitive use.  The holes in the face allow for the epoxy or resin to be injected in or squeezed out . Then peal off the face tape for a clean look.
Dakazman