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Old 28th June 2017, 11:03 AM   #1
Mitch Krause
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Install rivnuts before painting?

Hello,

Hopefully some advice on the best sequence. I want to understand this before I do something less than optimal.

Example, suppose I am making the side windows removable and using rivnut inserts to facilitate that.

Would I install the rivnuts now and verify proper alignment and everything on the window, knowing that the painting place is going to have to tape up a whole bunch of rivnuts and paint around them.

Or, would I drill the proper size holes, fitting things as best I can without actualy putting in the rivnuts, get the car painted and then install the rivnuts before putting the window in?
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Old 28th June 2017, 01:37 PM   #2
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Re: Install rivnuts before painting?

Fit it up completely before paint then install "disposable" screws in the rivnuts before paint. After paint remove the screws and install the "permanent" ones. Easy peasy.
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Old 28th June 2017, 02:21 PM   #3
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Re: Install rivnuts before painting?

Mitch, take advice, never use rivnuts, particularly into glassfibre, big mistake and very damaging.
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Old 28th June 2017, 04:22 PM   #4
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Re: Install rivnuts before painting?

Quote:
Originally Posted by wealdenengineer View Post
Mitch, take advice, never use rivnuts, particularly into glassfibre, big mistake and very damaging.
Whys that Frank? And do you suggest self tappers instead then?
.
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Old 28th June 2017, 05:06 PM   #5
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Re: Install rivnuts before painting?

I have used Rivnuts in fiberglass, however, I have epoxied them in place rather than pulling them tight with an installation tool. Must be really careful to only get the epoxy on the sides of the hole (toothpicks work well) and the rivnut must be free of any oils etc.
You can buy threaded inserts from McMaster Carr that would be a good alternative, but I would epoxy them in place as well.
Following all that up - I guess I would only use this type of fastener for something that would see periodic use (removal and replacement of screws).

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They have all different styles..
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Last edited by Big-Foot; 28th June 2017 at 05:08 PM. Reason: Additional info
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Old 28th June 2017, 05:06 PM   #6
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Re: Install rivnuts before painting?

Mitch,
If you use rivnuts on fiberglass especially around thin areas, expect cracking and spinning rivnuts. Not a good idea. Consider a few other options:

1. Gluing them in with Hysol type epoxy and not pulling the rivnut, just roughen it up for a mechanical bond. Slow process...

2. Tapping directly into the glass. Quickest way and works well with the nylon hardware some use to secure the Perspex/Lexan pieces. The nylon screws will usually strip before the glass and are then sacrificial. If you strip out the tapped hole for some reason, then move to option 1 or 3.

3. Drilling slightly oversize hole, inject a metal-set epoxy, then tap the stronger hole after its cured. Slow process...

With regards to the paint process, if you go with the tap into fiberglass method, I'd just drill the holes first, use Clecos to make sure everything lines up, then tap the holes after paint so you only have to tap them once.
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Old 28th June 2017, 05:59 PM   #7
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Re: Install rivnuts before painting?

Hi Mitch,
I simply put in helicoils with a dab of epoxy, M4 thread I seem to remember. Then used black Torquedrive screws with countersunk heads to hold the windows. It works a treat. Rivnuts seem OTT to me.
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Old 28th June 2017, 09:05 PM   #8
Mitch Krause
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Re: Install rivnuts before painting?

Thanks everyone. I appreciate the advice and am glad I had asked, I was under the impression from reading things that rivnuts were sorta the defacto standard. Sure seems like the is a few better ways to try. I will have to experiment a little bit.
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Old 29th June 2017, 12:24 AM   #9
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Re: Install rivnuts before painting?

Guys, one more thing to think about. Those of you that insist on installing metal screws with rivnuts and so on, take this into account. If your GT-40 ever flips/rolls and lands upside down, you are most likely not going to be able to open the door.

Being upside down in a car can be very disorienting (those of you that have gone through rollover training in the military with heavy weapons/ammo cans flying around, etc, will understand...), and if you're 'heavy set', you could be in a very 'tight' situation, especially once you release the harness. Your best option is to punch/push out your side windows and crawl out. Trying to get into a position physically to push/break out the front windscreen with all the sharp glass is a gamble, and I wouldn't count on it. Using Nylon or Aluminum 'breakaway' screws to secure the side Lexan windows is better, IMO, and will separate easily reducing egress time substantially. It may also minimize a panic situation inside a cramped cockpit, surrounded by (leaking?) fuel tanks, helpless passenger, and so on...
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Old 29th June 2017, 06:38 AM   #10
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Re: Install rivnuts before painting?

I'm happy to be corrected, but is epoxy the correct adhesive to be fixing to fibreglass? I thought you are better with polyester best adhesive to go with the polyester resin used in the grp. Epoxy adhesive for epoxy layup. It may give better adhesion to the metal inserts I suppose. Any comment further?
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Old 29th June 2017, 08:35 AM   #11
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Re: Install rivnuts before painting?

My experience with rivnuts, and the like, in thin fiberglass has been a good experience for items noted above. Using a single rivnut (not a row of them, or multiple rivnuts) is where the trouble starts with spinning rivnuts as one tries to loosen the fastener, and this is due to the attaching part rotating even slightly as one turns (applies torque to) the fastener. With multiple fasteners, the attaching part does not move around as torque is applied to any single fastener.

Also noted above for my acrylic wind screen, I simply tapped the fiberglass itself and used (in the US) #10 screws to hold the piece in place. Fiberglass threads are pretty robust if you have enough material. I always go at least with 2X the fastener size in the minimum depth of the fiberglass threads. For heavier duty applications (like door hinges and latches), I go with 1/4" or larger fasteners, thread and then helicoil the fiberglass. The helicoil method has never failed me, even for these types of heavier duty applications.
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