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Screws vibrating out

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Old 05-07-2018, 07:49 PM
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jester_s1
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Default Screws vibrating out

I have reatored an old Wildhare Sukhoi and flown it a few times. The canopy is held on by 4 screws that go through the fuselage into a blind nut in the canopy. I can't really tighten those screws as it would crush the balsa structure. Two vibrated loose and fell out last time I flew it. So does anyone have a solution? I can't Loctite them because I have to remove the canopy for assembly. Maybe Vibratite? Maybe a neoprene washer? Something else?
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Old 05-07-2018, 08:15 PM
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GREG DOE
 
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Put clear tape over them.
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Old 05-08-2018, 03:38 AM
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Can you remove the blind nuts add some plywood reinforcement and reinstall the blind nuts? That would allow you to use washers and lock washers.
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Old 05-08-2018, 04:13 AM
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Top_Gunn
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Put a thin sliver of wood inside each blind nut, next to the screw. Something sort of soft, like maybe spruce. You could try balsa, maybe ...
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Old 05-08-2018, 06:45 AM
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The solution to your problem.

RTL Fasteners - Hobbies, Radio Control, ( R/C or RC ), locknuts, metric screws, servo screws, socke: Rubber Backed Bonded Washers
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Old 05-08-2018, 07:13 AM
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A. J. Clark
 
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I have used Orings with success. Compress then some and they act like lock washers.
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Old 05-08-2018, 08:02 AM
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Steve Collins
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Nylon bolts are less prone to vibrating out.
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Old 05-08-2018, 08:52 AM
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I didn't even think of using nylon bolts. There is very little stress on these, so they would be plenty strong. I'll try that before going to the neoprene washers.
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Old 05-08-2018, 09:38 AM
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Dude, get you a bunch of them, they have all sorts of uses. Screwing down cowls they don't hurt the fiberglass, vibration resistance they won't back out, all manner of uses. I get a box from McMaster Carr for doing all the stab bolts and such on my gassers.
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Old 05-08-2018, 03:29 PM
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DGrant
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Bonded washers are very good for these types of applications. A bonded washer is a steel/metal washer, with a rubber washer bonded to it which creates a cushion/bed. There's different types and sizes of course, but you get the idea. Essentially they might be like putting an o-ring behind a washer... but much better.

I use those quite a bit for canopies and cowlings, and anywhere vibration might be present... as well as areas that might be a bit softer.in one way or another.

McMaster Carr has a good supply of them... in different sizes that fit most every size screw on planes from small to giants.
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Old 05-08-2018, 04:14 PM
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Exactly....I had some on my Escapde MX cowl for a long time and not one of them ever came loose.

now my son uses them on his 170cc planes and has the same results!

Jerry
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Old 05-08-2018, 08:32 PM
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Where the screw passes through the fuselage side, open up the hole just a little and glue in a nylon flanged bushing. Install through the outside with thin CA and trim flush to the inside with a razor blade.
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Old 05-09-2018, 07:49 PM
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Another quick and easy solution is to cut a piece of fuel tube about 1/8" long and slide it up to the screw head. Compress it about half way and it will provide enough friction to keep the screw from vibrating out without cracking the canopy.

Scott
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