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I saw these on a Kitfox used to attach polycarbonate to the door. What are these fasteners called? Thanks!
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This gallery has 1 photos.Rob Caldwell
Lake Norman Airpark (14A), North Carolina
EAA Chapter 309
Model B Quick Build Kit Serial # 11B-24B / 25B
YouTube Channel: http://bearhawklife.video
1st Flight May 18, 2021 -
I would guess just a tapered/countersunk "fender" washer to either spread the load of the screw, and maybe allow a larger hole to allow thermal expansion of the poly. -
Possibly. But I am more interested in the fastener itself as it does not fully penetrate the tube. I'm guessing its a rivnut. If that's the case, I'm not interested because of their inability to stay seated and will spin. But if there is something I am not aware of that performs the same result....Rob Caldwell
Lake Norman Airpark (14A), North Carolina
EAA Chapter 309
Model B Quick Build Kit Serial # 11B-24B / 25B
YouTube Channel: http://bearhawklife.video
1st Flight May 18, 2021Comment
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Could be that he cut threads into the tube, in which case it is just a plain old screw. This is an option for the BH, and Bob's favorite way. The washers are here:
https://m.aircraftspruce.com/catalog...lickkey=167440Comment
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Interesting. I would think that 4130 would be too thin to accept a decent thread. Thanks for the link to the SS Washers.Rob Caldwell
Lake Norman Airpark (14A), North Carolina
EAA Chapter 309
Model B Quick Build Kit Serial # 11B-24B / 25B
YouTube Channel: http://bearhawklife.video
1st Flight May 18, 2021Comment
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It doesn't take much, since those screws don't get really tight. I used all aluminum rivets with wide heads and they have been holding up well.Comment
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That's a way to do it sure. Though with acrylic instead of polycarb I'd be worried about cracking with expansion/contraction, my skylight and door windows are all acrylic. The CSK washer would warrant a much larger clearance hole, at least that's what the design guides say...Comment
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these washers are know as tinnerman washersComment
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Rivnuts are not all created equally. They have a reputation for spinning when set poorly. Some are better designed as they have knurled flange face and barrel, but I have yet to find smaller than a #8 with that design. You could tap the tube if the wall thickness was greater than .035. Or use a sheet metal screw. Or just pop rivet.
Akschu and I have been testing knurled steel rivnuts and I think that's the way to go.
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Looks like flathead phillips screws and tinnerman washers to me. Probably threaded holes like Jared suggested.Comment
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