Prop Bolts

[dick hanson]

For another method of wing retaining try this: 1/4"x20 with surgical rubber compression piece
I use these on "kit" type models (my 42% Radiocraft qualifies) and simply tighten till the rubber bulges - The tension prevents rotation in use and the rubber insures that the bolt is not overloaded. The constant tension keeps the wings in position even thru rapid flicks of all types
On H9 ARF's they really simplify wing attachment
The only failure on wing bolts on those ARF's I have had (a 33%Cap)- was the time I used a steel bolt and the vibration unscrewed it --My fault-- The plane flat spun in from 200 ft with one wing panel extended 6" . with only damage to the landing gear - the field was wet, tall field grass.

[KrisW]

I really can't see the sanity in depending on a piece of nylon to keep an aircraft wing in place. I've seen a number of broken nylon fasteners on planes. . usually AFTER the wing departed company and the fuselage became a projectile. It's amazing the amount of damage a 3-4 lbs fuselage can do at 60 mph.

People laugh at these incidents. . right up until someone gets hit with an errant plane/parts of a plane.

Make all the little doo-dads and fixes you want to. STEEL bolts do not fail from in-flight stresses. Nylon can, and does, fail. It's a grand total of a 1/2 ounce difference, which is why yahoos went to nylon in the first place. . it's lighter.

Lets see, , , possible injury or loss of aircraft. . or an additional 1/2 ounce.

I'll take the steel, thanks anyway.

[dick hanson]

You may make fun of the setup all you want - It is a viable method from a engineering standpoint. The strain on the bolts is not severe . Controlling the effects of vibration is the primary problem

[KrisW]

	Quote: Originally Posted by dick hanson
	You may make fun of the setup all you want - It is a viable method from a engineering standpoint. The strain on the bolts is not severe . Controlling the effects of vibration is the primary problem

No. . the strain is not "severe" at all. . .yet they FAIL, meaning that 1/4-20 nylon bolts are not structurally capable of how they are being used.

You cannot refute the facts with desire for a certain end product. Nylon bolts fail at unheard of low stresses. I can snap one with my bare hands. A 2-56 metal screw is far stronger than a 1/4-20 nylon bolt, in both shear and tensile strength, and it weighs less than 1/4 its weaker, more brittle, failure prone nylon competitor that has a diameter almost 10 times as much.

If nylon is so great. . let's use it for prop bolts. . . . . . . .

[Temptation]

Kris, it's o.k. to use what you like. I just don't understand why, if someone does not do something the way you do, you think they are wrong, and will not give up until you either belittle them, or change their mind. There is more than one way to skin a cat, as the saying goes. Nylon bolts work just fine for wing retention. I have been using them for 22 years in everything from trainers to my 40%ers. In fact I have never seen a nylon wing bolt fail. When used correctly they make a great retention system. I will not bash you for using 2-56 steel bolts on your 40% plane. The reason: because I am sure it works just fine for you. Have a nice day.

Mike Darr

[KrisW]

	Quote: Originally Posted by Temptation
	Kris, it's o.k. to use what you like. I just don't understand why, if someone does not do something the way you do, you think they are wrong, and will not give up until you either belittle them, or change their mind. There is more than one way to skin a cat, as the saying goes. Nylon bolts work just fine for wing retention. I have been using them for 22 years in everything from trainers to my 40%ers. In fact I have never seen a nylon wing bolt fail. When used correctly they make a great retention system. I will not bash you for using 2-56 steel bolts on your 40% plane. The reason: because I am sure it works just fine for you. Have a nice day. Mike Darr

I'm not insisting people use what I use, Mike. . I'm insisting they think about the ramifications if that silly nylon bolt fails. They do fail in flight.. planes come apart while using them. YOU have broken them, just tightening them in place.

Does that make any sense??

I have never seen anyone break a steel bolt while tightening it. That, in and of itself, should tell the entire story.

[dick hanson]

Sorry you misunderstood the application-

So far , others who have adopted it, prefer it

[KrisW]

	Quote: Originally Posted by dick hanson
	Sorry you misunderstood the application- So far , others who have adopted it, prefer it

"Preference" does not automatically render a failure prone item "Safe". There is a good reason the FAA does not allow items in aircraft that cannot PROVE their ability to withstand stresses far in excess of the demands of their application. Remember the DC-10's that fell out of the sky because of engines separating from their pods?? Those items were designed with 3-4 times the strength necessary to hold those engines in place, but they failed because of what? "Improper torque of bolts" if I remember correctly.

"I prefer nylon bolts" is hardly the epitaph I'd want in the aftermath of a wing separating from a 4 Star .60.

[dick hanson]

Respectfully, the applications have nothing in common.
Metal is better in tensile than nylon- that is obvious .
The application - simply holding a wing in position does not require a lot of tensile strength
Bolt ON wings ( bolt on top/bottom of fuselage) have more strain on them than those wings which slide on tubes and are secured to the fuselage.
The real problem which typically exists on models (with IC engines ) is the range of vibration that occurs.
Steel bolts into steel sockets can easily be spun free from vibration.
Most good ARF guys use nylon into steel --steel into hardwood etc., to allow the threads to slightly "lock" together
On a lot of machinery, lock washers/star washers etc., are used to prevent vibration from backing the bolts out.
If you look at the rubber on bolt setup I showed - --it is simply an extension of this basic idea .
The bolt is preloaded and the load stays even over a number of turns of the bolt .

On many of the H9 ARFs the wings have steel Tnuts in the wing root - A nylon bolt is provided because it will "stick" better in the steel under vibration . Swapping to a steel bolt can be dangerous because any loosing of tension means the bolt can spin under the right harmonic - seen it dun it.
Use what you like but look at the complete list of possible failures first .

[Diablo]

	Quote: Originally Posted by KrisW
	Remember the DC-10's that fell out of the sky because of engines separating from their pods?? Those items were designed with 3-4 times the strength necessary to hold those engines in place, but they failed because of what? "Improper torque of bolts" if I remember correctly. "I prefer nylon bolts" is hardly the epitaph I'd want in the aftermath of a wing separating from a 4 Star .60.

Actually no. The DC-10s had a failure of the engine pylon itself because the mechanics improperly used a hoist when servicing the engine. Basically, they rammed the engine back into the pylon, and deformed the pylon which initiated a crack.

[KrisW]

	Quote: Originally Posted by dick hanson
	Respectfully, the applications have nothing in common. Metal is better in tensile than nylon- that is obvious . The application - simply holding a wing in position does not require a lot of tensile strength Bolt ON wings ( bolt on top/bottom of fuselage) have more strain on them than those wings which slide on tubes and are secured to the fuselage. The real problem which typically exists on models (with IC engines ) is the range of vibration that occurs. Steel bolts into steel sockets can easily be spun free from vibration. Most good ARF guys use nylon into steel --steel into hardwood etc., to allow the threads to slightly "lock" together On a lot of machinery, lock washers/star washers etc., are used to prevent vibration from backing the bolts out. If you look at the rubber on bolt setup I showed - --it is simply an extension of this basic idea . The bolt is preloaded and the load stays even over a number of turns of the bolt . On many of the H9 ARFs the wings have steel Tnuts in the wing root - A nylon bolt is provided because it will "stick" better in the steel under vibration . Swapping to a steel bolt can be dangerous because any loosing of tension means the bolt can spin under the right harmonic - seen it dun it. Use what you like but look at the complete list of possible failures first .

I'll just repeat this, so you get it. . . .

"I preferred NYLON bolts" is NOT a suitable epitaph for someone on the receiving end of a model aircraft that had a Nylon bolt fail. . .

Nylon bolts are not acceptable if safety is a major concern.

[KrisW]

	Quote: Originally Posted by Diablo
	Actually no. The DC-10s had a failure of the engine pylon itself because the mechanics improperly used a hoist when servicing the engine. Basically, they rammed the engine back into the pylon, and deformed the pylon which initiated a crack.

So the reports that over-torqued bolts were causing causing cracks in the mounting pylons are not true, and there was no massive inspection campaign of all DC-10's to assure no stress cracks were forming around the bolt holes?

Interesting. . .

[wizard]

Kris it was stress cracks due to improper maintenance procedures used to replace engines after inspection. The lift used was not meant to perform the required task and was placing an excess of force on the mounting pylons. Documented fact.

[wizard]

As for Nylon bolts for wing retention. On larger models with wing tube and anti rotation pins the only stress on the bolts is linear in nature. If the bolts were not monkey fisted into place the chances of failure are minimal. On smaller models where the nylon bolts are used through the wing as in trainers with the wing bolts through the top of the wing on high wing, or the bottom of the wing on low wing. The main purpose is for the bolt to shear in the event of impact lessening the damage to the aircraft. Less repair time for those learning the finer aspects of flight means less chance of loss of interest.

Just my 2 cents

[KrisW]

	Quote: Originally Posted by wizard
	Kris it was stress cracks due to improper maintenance procedures used to replace engines after inspection. The lift used was not meant to perform the required task and was placing an excess of force on the mounting pylons. Documented fact.

Okay, thanks Wiz.