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Wing Hold Down Bolts Question

Old 07-01-2013, 01:01 PM
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Tony Gag Jr.
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Default Wing Hold Down Bolts Question

I recently finished a Yellow Aircraft Zero and I have a question about the wing hold down bolts. Yellow uses Nylon 5/16-18 wing hold down bolts. For some stupid reason I installed metal 1/4-20 blind nuts in the wing saddle. Are the 1/4-20 wing bolts good enough or should I knock them out, install dowels in the holes, then drill and tap the wood for the 5/16-18 wing bolts?

Thank you,
Tony Gagliardi Jr.
Old 07-01-2013, 01:04 PM
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F4u5
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Default RE: Wing Hold Down Bolts Question

1/4-20 are perfectly good, Just close-up the wing bolt holes a bit so you don't get too much play. I glue in some dave brown arrow shaft.

Jeff
Old 07-01-2013, 01:05 PM
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Tony Gag Jr.
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Default RE: Wing Hold Down Bolts Question

Thanks Jeff. Do you mean install the arrow shaft in the hole that is in the wing?
Old 07-01-2013, 02:23 PM
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All Day Dan
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Default RE: Wing Hold Down Bolts Question

Tony, here's what I do on my 50cc, 20 pound planes. Those are 1/4X20 nylon bolts. Dan.
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Old 07-01-2013, 02:36 PM
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F4u5
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Default RE: Wing Hold Down Bolts Question


ORIGINAL: Tony Gag Jr.

Thanks Jeff. Do you mean install the arrow shaft in the hole that is in the wing?
Yessir, just to take out the slop.

Jeff
Old 07-01-2013, 09:23 PM
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ram3500-RCU
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Default RE: Wing Hold Down Bolts Question

I agree with F4u5.

I NEVER use nylon wing bolts on giant scale war birds. Wing loading is always higher than less scale sport models, you have expensive equipment like retracts in the wings, with extra functions like flaps and gear doors, with the extra weight they produce, not to mention all the work on a scale paint job. Sheer strength on a nylon bolt is a fraction of what a steel bolt will give you. Any side movement like the shock of a less than perfect touchdown on one wheel in even a slight cross wind could break a bolt and ruin a lot of equipment and work. Just not worth the risk. Warbirds are usually brought in as wheel landings, making wing to fuselage connections more critical, IMO.

The other day I saw a guy bring his 33% Yak in just a little too tail high on the mains. Tore the gear right off, sending the pants into the underside of the wings, and then one of the stabs. I could not believe what I saw given the relatively light touchdown he had made. Turns out he had nylon bolts in his gear. Steel bolts would have saved his plane for sure.

I know we are talking about wings not gear, but the principle is the same, IMO.
Old 07-01-2013, 10:59 PM
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JPate147
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Default RE: Wing Hold Down Bolts Question

Like Jeff said - just use a 1/4 by 20 steel hex head bolt and slide it inside the D. Brown arrow shaft. A small local hardware store will sell these bolts as fully threaded up to 5 inches long. You can cut off what you don't need. The arrow shaft prevents any overtighening of the bolts - it will not compress. I use this method on all my planes, including the Yellow Zero. Some are 50 pounds plus and I have never had a failure.
Old 07-02-2013, 12:03 AM
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deatonbt
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Default RE: Wing Hold Down Bolts Question

.
Old 07-02-2013, 12:05 AM
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Default RE: Wing Hold Down Bolts Question

I can't say which is better when considering sheer strength, but I have had a problem using metal 1/4-20 bolts with metal blind nuts on a gas plane. The steel bolts would back out. I am thinking because of the vibration and the two smooth surfaces. I never tightened the bolts down very much to prevent the wood from being crunched. I never tried to solve the problem other than to switch to nylon bolts for the extra friction. Steel bolts with threaded hardwood may work.

Brian
Old 07-02-2013, 03:47 AM
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Default RE: Wing Hold Down Bolts Question

Unless you are planning on (non scale) extreme negative "G" maneuvers, 1/4" X 20 nylon bolts should work just fine if the wing sets into a recessed (trailing edge) saddle that will keep the wing from twisting.
Old 07-02-2013, 02:10 PM
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Tony Gag Jr.
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Default RE: Wing Hold Down Bolts Question

Thanks for the input. I don't see where Jeff said to use steel bolts?
Old 07-02-2013, 02:54 PM
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Capt G
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Default RE: Wing Hold Down Bolts Question

I have always used 1/4 x 20 aluminum bolts to hold the wing on. Nylon are prone to breaking
Old 07-03-2013, 02:36 AM
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Default RE: Wing Hold Down Bolts Question

I like the fact that nylon bolts break. That's why they are used. If a situation develops that causes a nylon bolt to break, that means structure either didn't break, or the damage was minimized. Steel bolt don't break, they rip out structure. On a low-wing design, the stress is not on the bolt, so steel is not needed. Usually, all that is needed to demonstrate the difference is one bad landing.
Old 07-05-2013, 03:13 PM
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Default RE: Wing Hold Down Bolts Question


ORIGINAL: Lifer

I like the fact that nylon bolts break. That's why they are used. If a situation develops that causes a nylon bolt to break, that means structure either didn't break, or the damage was minimized. Steel bolt don't break, they rip out structure. On a low-wing design, the stress is not on the bolt, so steel is not needed. Usually, all that is needed to demonstrate the difference is one bad landing.

I agree, it is not a stupid reason some pilots use nylon bolts instead of metal to hold down wings. Hope one day you don`t happen to tip stall and a wing tip hit the ground, either caused by a cross wind or other. I rather snap 2 bolts and have minimum damage than bolts stay put and have even more damage to wing and fuse.
Old 07-23-2020, 02:51 AM
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orthobird
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what are the recommendations now?
Steel / alloy versus Nylon?
Wood threaded hardened by CA vs T-nuts?
Old 07-23-2020, 03:36 AM
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Tony Gag Jr.
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Nylon bolts are perfectly fine, either with a blind nut or wood hardened with CA. Metal bolts are okay too, just donít use them with a metal blind nut, the bolt could loosen during flight.
Old 07-23-2020, 05:56 AM
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edp
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These are what I use in all my birds, pattern and scale.
Old 07-27-2020, 09:26 AM
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I cartwheeled an Ace 4-60 bipe on landing once. It sheared all the nylon wing bolts off both wings (1/4-20 bottom and 10-32 on top). I spent 5 minutes digging out the wing bolts and went back to it.

However; that was a 60 size sport plane. You have a plane twice as heavy if not more. I would go with 1/4-20 steel bolts for the win. My experience with these bigger planes is that when they crash, they hit pretty hard and do a lot of damage. I don't think a nylon bolt shearing off is going to help much overall.


carl
Old 07-27-2020, 11:50 AM
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Same thing, nylon on the pattern birds and aluminum on the warbirds.

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