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Wing Bolts vibrating loose

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Wing Bolts vibrating loose

Old 05-14-2021, 09:23 AM
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douglas racer
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Default Wing Bolts vibrating loose

I landed my nitro Sig Kougar today and one of the wing bolts had vibrated loose. It seemed snug enough going it. It must have been just the right resonance. Does anyone know something sticky I could put on them to avoid this? Maybe a little foam glue? Thanks
Old 05-14-2021, 10:10 AM
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More details.

Metal bolts, nylon bolts? Screwing into what, wood threads, metal threads etc
Old 05-14-2021, 10:47 AM
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Sorry, nylon bolt into wood. I assume the wood was reinforced with CA but I didn't build it. It seemed snug enough but apparently not.
Old 05-14-2021, 11:42 AM
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Ahh ok. Go to your local Ace Hardware and find some rubber washers and use them on the nylon bolts and as you say CA wick the threads so they are good and hardened
Old 05-14-2021, 12:48 PM
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Originally Posted by douglas racer View Post
Sorry, nylon bolt into wood. I assume the wood was reinforced with CA but I didn't build it. It seemed snug enough but apparently not.
I would add CA and re-tap the threads,,, do it a few times,,

I wonder if someone used metal bolts at one time and vibration enlarged the threads,, very odd that a nylon bolt would work loose out of good threads
Old 05-14-2021, 02:18 PM
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"O" ring works pretty good also.
Old 05-15-2021, 05:13 AM
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Re-balance prop?
Old 05-15-2021, 05:49 AM
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I put epoxy in it a couple times and threaded in the bolt. I think maybe it's more snug now.. I think I'll put this one on slightly tighter than the other one so it takes more of the load. I will try it again on Monday and keep a closer eye on it. Thanks
Old 05-16-2021, 05:13 AM
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Originally Posted by douglas racer View Post
I put epoxy in it a couple times and threaded in the bolt. I think maybe it's more snug now.. I think I'll put this one on slightly tighter than the other one so it takes more of the load. I will try it again on Monday and keep a closer eye on it. Thanks

This has me wondering just how loose the threads are. I have waxed up a nylon bolt and applied some epoxy laminating resin with some milled fiber added in to the hole in order to fix the same issue. In my case the molded threads worked just fine because the epoxy had a fibers added to it. The suggestion of CA was a good one as it would have penitrated the wood some and helped reduce the hole diameter some. Straight hobby type epoxy is really fairly weak stuff. If your threads are more epoxy then wood you could be setting yourself up for a failure.
Old 05-16-2021, 08:12 AM
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The bolts went in tight enough that I was surprised it vibrated out. A coating of epoxy has made them even tighter though. I'll keep a closer eye on them. I'm going to fly it again on Monday. What is milled fiber?
Old 05-16-2021, 08:35 AM
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Originally Posted by douglas racer View Post
The bolts went in tight enough that I was surprised it vibrated out. A coating of epoxy has made them even tighter though. I'll keep a closer eye on them. I'm going to fly it again on Monday. What is milled fiber?
https://www.towerhobbies.com/product...e/DLMBD69.html
Old 05-16-2021, 09:21 AM
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Originally Posted by BarracudaHockey View Post
Thanks.
Old 05-17-2021, 01:39 PM
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Belt dressing.
Old 05-18-2021, 08:55 AM
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Originally Posted by GREG DOE View Post
Belt dressing.
That's an idea. I might try that in the future. A bit of epoxy on the threads did the trick this time though. I've done 8 flights in the last two days and they have held solid.
Old 05-18-2021, 07:17 PM
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I've never heard of a nylon bolt vibrating loose. That's the whole point of using them.
I'd be concerned that it actually pulled out of worn threads. It's practically impossible for it to have vibrated loose if the threads were a little tight and you tightened it enough to have some stretch.
Old 05-19-2021, 09:08 AM
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I've never seen it before either. But with other one holding the wing solid, it was definitely backed out not pulled out. A little bit of epoxy on the threads has it staying in place now. Perhaps the threads aren't as good as new. but I can tell they are still in decent shape by the amount of torque I'm able to tighten them to without them slipping.

Last edited by douglas racer; 05-19-2021 at 09:11 AM.
Old 05-20-2021, 05:52 AM
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How do the threads look on the bolt? If they are worn, that can cause a pull out too.
Old 05-20-2021, 09:43 AM
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I put new bolts in. But I think a little epoxy on the wood is what fixed it. It definitely backed out though. I've been flying it four days in a row now and it's holding good.

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