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Zenith "no hinge ailerons"

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cheapracer

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Some of you know that Zenith for sometime now on the CH601 and CH650, have been using the actual skin of the aileron as the flexible member to act as a hinge.

Now it's been around for a while, couple of thousand planes out there, and seems to offer reliable service (I wasn't looking to re-has the early CH601 wing spar failures), so it seems to work.

I am curious what others think about it, for example I guess I have flexed too many pieces of aluminimun til they went soft and snapped, and in short time to, so i have this mindset that this will do the same, does it concern you, what preventitive measures would you take if you built one similar etc?

Explaination and testing cycle results here ..
http://www.zenithair.net/design-and-application-of-the-zodiacs-hingeless-aileron/

ail 4.jpg ail 1.jpg ail 2.jpg ail 3.jpg
 

Vigilant1

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As you say, it does work according to "book analysis," bench testing, and in the field. So, I don't think there's a safety issue.
I've read that many people are dissatisfied with the heavy feel of these ailerons, and that things get much better when a piano hinge replaces the flexing sheet. I can see how that would be possible.
Also, for anyone selling kits/plans, I don't think this is a beneficial design choice from a marketing perspective. It is something that has to be explained to potential customers, and that is never good.
 

Hot Wings

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what preventitive measures would you take if you built one similar etc?
None other than making sure that the system is flutter free and typical pre-flight inspection. It seems intuitively odd but the numbers and testing always trump 'feel" - if properly done.

I'd like to use this method to replace some piano hinges but I'd have to put a "U" bend in to make it fit and I don't have the time or desire to do the required math and testing.

I'm looking at a composite version.
https://www.compositesworld.com/blog/post/carbon-kevlar-hinge-
But I think there are better materials than Kevlar for this.
 

Vigilant1

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Ordinary fiberglass shall do it ? Corvette have/had an leaf spring of fiberglass ?
I'd need to test that very thoroughly, especially if we want a relatively short flexing zone. The tough, flexible fabrics (UHMWPE, UHMWPP) would seem to have more suitable properties. Also, we'll need to to think about UV tolerance if whatever fabric being used can't be blocked from the sun.
 

BoKu

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This is probably one of those things that works fine right up until it doesn't.

If you look at the (few and getting fewer) sailplanes that use an uninterrupted upper skin between the wing and the aileron or flaperon, you see that they all also use supplemental mechanical hinges that react shear between the control surface and the wing. In the absence of those hinges, you probably flirt pretty closely with flutter regimes. Given the structural complexity of the uninterrupted skin, and the mechanical complexity of having both that and the mechanical hinges, the cost probably does not outweigh the relatively tiny performance benefit. Especially since commercially available mylar seals get you most of the way there.

As it turns out, the window of utility for this innovation would probably have been wider had aggressive airfoils like those on the ASG-29 come along earlier, and had they used it on the lower skin instead of the upper skin. However, I don't think that would have made it worthwhile for anything but advanced competition, and such aircraft would probably be known for accumulating water that enters at the upper hinge gap and pools inside the hinge cove.
 

stanislavz

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I'd need to test that very thoroughly, especially if we want a relatively short flexing zone. The tough, flexible fabrics (UHMWPE, UHMWPP) would seem to have more suitable properties. Also, we'll need to to think about UV tolerance if whatever fabric being used can't be blocked from the sun.
Flexing - flexure bearing. Whey may contain necessary data on longevity. Done from cf and gf routinely.
 

fly2kads

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I can see how that type of hinge would affect control feel. The force required to flex the skin would feel like friction in the control system, would be proportional to the length of the hinge line, and would increase with deflection. You're basically putting a spring into the system. One should be able to calculate the force required.

I see from Zenith's description that the aileron deflection, in their case, is limited to +/15 degrees. That's not a lot of deflection. How does the analysis change if you need, say, 25 degrees up and 15 degrees down?

Bob's comment about flutter deserves some consideration. If the aileron is mass balanced about the hinge line, this type of hinge would allow the whole aileron to float up and down as the wing flexes.

None of this is to say that this type of hinge is bad. Just that there appears to be some things to know and understand in order to apply it to another design.
 

Vigilant1

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I wonder how these hingeless hinges perform when the wings bend (from wing root to wing tip). It would seem that even a very minor curvature of that strip is going to cause it to straighten out (chordwise) and strongly resist bending.
 

Dana

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Polyethylene "living hinges" have been common in the R/C world since the 1970s. Doing it in metal makes me nervous... analysis and testing may say it's OK, but it only takes a small scratch to drastically reduce the fatigue life of aluminum.
 

BoKu

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Polyethylene "living hinges" have been common in the R/C world since the 1970s. Doing it in metal makes me nervous... analysis and testing may say it's OK, but it only takes a small scratch to drastically reduce the fatigue life of aluminum.
It's not so much the materials as it is the size that counts. The square-cube law conspires with Reynolds numbers to severely limit how well such solutions scale between m and 10m span aircraft. There's also the matter of failure criticality--having lives at stake has a way of making durability and reliability much more important.
 

Mad MAC

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One issue with these 2D hinges (be it metal skin or piano hinge) is that they are sensitive to wing deflection. This tends to be what causes the bomber aileron forces (a New Zealand ag aircraft had piano hinge ailerons, ex bomber guys accepted the stick forces, the fighter pilots not so much).
The lack of crack stops and rivet bending is what scares me about the skin hinge approach. Not that it isn't actually that hard to design out those issues. Slot the skin past the rivet line (might actually drop the stick forces as well) and use a double row of fasteners.
 

wsimpso1

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I am not so worried about loss of one aileron as I am worried about failing the hinge partially and then the aileron flopping around all crooked and sucking the bird to the ground. You guys ever seen the air show routine where one aileron is dropped off a little taildragger and the pilot flies all the standard stuff, including rolls, spins, and the like. Or the collision at Duxford between a Skyraider and a Mustang? We lost a Mustang that day, but the Spad loss some big chunks including an aileron or flap (I forget which), did an aileron roll, and still landed just fine.

In reality, this is probably quite safe when stresses are kept down. Stresses and hinge moments can both be kept down by using enough spanwise length in the hinge. The ailerons carry positive lift and so will try to deflect up against the restoring force of the skin/hinge, so it may be possible to make the hinge too long in the chordwise direction.

Personally, Chris Hientz has a bit too much of thinking he is the smartest guy in the room, and just has to show it. No one else is doing this, and that ought to be evidence enough that maybe it is not a great thing to include in another airplane.

Billski
 
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TFF

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Homebuilts don’t fly that much. The owner might think they are, but it’s rare to fly 1000 hrs in a homebuilt. Cessna150s almost always have 5000 hours if not 15,000 hours if it was a school plane. Airliners at 40,000 are mid life.

Hinges like that are not forever like bearings are not forever. A certified plane would probably have a life limit on that style hinge. 1000hr? 2000? There would be some number that it would be replace. Owners hate time change parts. Reminds owners there is a clock ticking along with the value. The question is do you bet no one ever gets to that magic number with normal usage?

Zenith airplanes don’t seem to be designed with an unlimited lifespan in mind. I don’t think they will fall apart right away but there is not a lot extra there. How many hours of constant use could a Zenith take day in and out? Will someone hit that mark ever? I would not build a hinge like that, not without replacement criteria. It helps the roll rate with the gap closed. That is good because you have to limit the range so it never gets deformed. I would not want it on something fast.
 

cheapracer

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WOW!

Blown away, I didn't expect to get many answers on this subject at all, and I wake up this morning to see this amazing lot of informative answers, this place is just the best some days!

I didn't even think of it before, but "Back to the Future" - leather hinges would likely be the best choice for this type. Once upon a time, leather hinges were very common for many applications.


I am not so worried about loss of one aileron as I am worried about failing the hinge partially and then the aileron flopping around all crooked and sucking the bird to the ground.
That was actually my biggest fear with this setup, an aileron NOT falling off completely.


No one else is doing this, and that ought to be evidence enough that maybe it is not a great thing to include in another airplane.
That I choose not to agree with you, I think one of the issues with aviation is the angst towards change.
 

Victor Bravo

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This is only tangential because piano hinges were discussed as an alternative. But my Kolb LSA aircraft used piano hinges and it was very heavy on the ailerons. Distractingly so and completely inappropriate for a 300-400 pound airplane. The problem is that the Kolb wing had a little flex to it (unlike many other more rigid structure wings) and it had long lengths of aileron and torque tube that hinged, and under 1G flight loads the piano hinge halves bound against each other creating significant friction.
 

cheapracer

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This is only tangential because piano hinges were discussed as an alternative. But my Kolb LSA aircraft used piano hinges and it was very heavy on the ailerons. The problem is that the Kolb wing had a little flex to it
Cut the hinge pin into say 4"/100mm segments, whatever lengths to line up with the hinge gaps, they can't go anywhere once secured at either end.
 

stanislavz

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Hi all. From mine point - on rc models, its is common to make a hinge just from duct-tape.

So why not to take 3-5 layers of 0.2 mm foil and do it like this ?

Or - any strong fabric + rubber glue..
 

AdrianS

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Construct foam-core wing.

Machine spanwise clearance slot in underside, removing core down to upper skin, which becomes the hinge.

Cut sides (chordwise).

Seal exposed core.

You could lay more/different fabric along the hinge line in the initial layup, if required.
 
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