Folding wing designs?

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rtfm

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Hi guys,
I was wondering if any of you might have some design details, sketches, explanations etc for how to construct a folding wing.

I used to share a hangar with a guy who had a Thorpe T-18, and his wings folded, but the effort to do so was off-putting, and he grumbled and complained every time he had to do so. I'm looking for a simple hinge arrangement, so that the outer third of each wing (ie at the flap/aileron junction) can be unbolted, and flipped up and over to rest on the inner section on the wing. But it has to be easy and quick to fold for a single guy on his own out at the airfield.

In my neck of the woods, there is NO hangar space available. NONE. But when I've asked, I've always been told that if I had a plane with folding wings, which didn't take too much space, they could always find me some corner somewhere. So, while I'm terribly sceptical about folding wings in general, if I could find a really quick and easy implementation, I think it may be worth a try.

I'll be using two pul-pull cables to operate each aileron, so I'm guessing the cables can be left intact when folding? Orion was talking about a while back about using electro-mechanical linkages for the ailerons. That would be even better, because the only contact with the folding wing panels would be some electrical wiring. But I don't know how to do this, so it is still cables at this stage.

Any ideas? Pictures? Drawings?

Regards,
Duncan
 

addaon

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Duncan, what's your wing span? Is your plane still as small as I remember? I figure if you have a ~25' span with a low wing and low gear (as I remember), you should have no problem sharing a hangar with the high wing folks; you'll fit right in underneath, no folding needed.
 

rtfm

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Hi,
Yep. Plane is still a tiny beast. Span is 18.5 ft You may be right, but I'm still interested in the design details.

Duncan
 

HumanPoweredDesigner

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Are you using a fabric wing or structural skin? For my hpa, the wings will come completely off, with beefed up ribs at the junction. I'm going to use tape over the crack but you could use a cuff. I think you need an access port to get in there and unbolt stuff. For the aileron link, you need one of those double thread direction things that you twist and can tighten the aileron cables, or complete separate the inboard and outboard pieces. Put some threaded nipples in there for each end to screw into so they don't slide back into the wing out of reach. I've never done anything like this, but that is my idea.

The other thing that jumped out at me is if you fold at the 1/3 point, only one wing can lay on top of the center. The other wing would have to point straight up and hopefully not fall over.

As for one person ease, you may need some kind of folding stand to hold up the wing while you work on it, with straps too. Then you need some blow up cushions and straps so you can put the wing sections on top of each other on the middle, and then taxi the folded plane over to the hanger.

As for inside the wing, each spar cap and maybe even some overlapping web would need bolts. Don't trust me for structures, but I'd have a metal strip at the junction where bolts can go into, with the metal strip distributing the loads.
 

pwood66889

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Just read on another list that there is a wing fold STC for an Ercoupe. This bird has a 30-foot span, and the folding outer panels are aluminum framed and cloth covered.
Percy in SE Bama
 

WonderousMountain

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Currently working on a morphing tilting electric vehicle.

Not my project. One of the keys to it's possible success is running the drivetrain to a pivot point, then from another sprocket on the same jack-shaft.

In-visioning a mechanism (possibly a pull pin) that released the aileron cables and wing section at the same time, and then used that same piece to lock it in resting position. Solve that and you're troubles are over. Also it shold be simple enough for any machine shop to replace.

Oh, and make it out of carbon fiber, so people won't complain it's too heavy:nervous:

PM me if you have any more trouble with this.

Blessings,

Wonderous Mountain
 

rtfm

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Hi,
Thanks for this. I was thinking of something very much simpler - basically just a hinge at the top of the main and rear spar, and two bolts at the bottom to secure everything. Pull the bolts out the bottom and hinge the wing up. I'd need some sort of cuff on the top, but that's about it.
RZB F1 28 Dec 2010 front view.jpg
I'll try mocking it up to see how it goes. Just like the pictures in the Patent you pointed me to, Craig. But without the fancy stuff.

Cheers,
Duncan
 

Dana

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Well, you need three points of attachment. It can be a universal joint and two disconnect points (if the wing must rotate and fold back along the fuselage) or two hinge points and one disconnect (if the wing just folds up).

On my Kolb, there is a universal joint (a simple block joining two forks, one of which rotates) at the top of the wing spar, an attachment point at the rear, and the wing strut is the third point. Ailerons are full span, and you disconnect (clevis pin and safety pin) the pushrod from the aileron before folding.

On the Sadler Vapire I looked at, there was a similar universal at the top of the spar, and a tab and fork connection at the bottom of the spar. The rear connection was a round plug in deal with a bolt. Ailerons were Teleflex cables, so no disconnection required, and the flaps were driven down by a fixed tab on the inner portion of the wing, with springs pulling them up.

If it's poorly designed, a wing fold can be more trouble than it's worth. If it's well designed (like the Kolb) it can be an easy part of the preflight routine. It takes me 10 minutes to unfold the wings and tail, connect all controls, etc.

-Dana

Hard work has a future payoff. Laziness pays off now.
 

GESchwarz

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Copy the pros. The US Navy has been doing it for decades. There are no control connections to made and broken. You have hinges and locking pins. No messing with controls. They don't have a problem with their folding wings because they have got it figured out and idiot proofed. The internet is full of detail photos of how they do it.
 

Hot Wings

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Autoreply posted a link to this pic of a Fournier motor-glider on another thread dealing with folding wings. It's got all of the basics, but does need a cuff installed after folding.

Fournier RF5 folding wing.jpg

The Cougar, a Tailwind copy, the Dyke Delta, the new Onex, the Mitchell wing, and the Fred experimentals all have folding wings, along with a lot of ultralight planes. Finding pictures or diagrams of these planes folding wings, and many other examples, for inspiration shouldn't be too hard.
 

skeeter_ca

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I've looked alot and finding folding wing options on planes is not hard. What is hard is finding detailed design info on these systems. Lots of pictures from too far away and non-detailed descriptions of folding wing systems, especially when it comes to control system connections. The Onex is touted by thier manufacturer as being very easy and quick. Seems to be the exact thing your looking for. Maybe order a set of plans or construction manuel when it is available to get a design peak.

Sonex Aircraft Hornets' Nest Research and Development
 

Mac790

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Well, since Duncan is building a composite airplane it might be a better idea to take a look at composite planes solution rather than aluminum ones. Personally I really like Stemme method, you can check it out in this movie, there is a close view at the end of movie. 4.40-5.20

Another close view in the attachment from other sailplane.

Seb
 

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GESchwarz

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I just experienced the chance of a lifetime. I visited the Chino restoration facility yesterday and was able to examine the Grumman Hellcat wing center section, off the plane, fully restored with all access panels removed! Unlike the Avenger which has an inverted V spar, the sloped Hellcat spar is stabilized with rather stout ribs and intercostal angles spanning the web.
 

GESchwarz

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If you're inquiring about the Hellcat, they are doing a total restoration; in some places a complete teardown. It looks factory-new with fresh green chromate primer and bare rivets. You ought to check it out.
 

MicRuler

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Here is a video scaled down version of the WWII Sea Fury's wing folding mechanism YouTube - Sea Fury folding wing 4, here is it in action YouTube - Sea Fury folding wing 7 I know its RC but its all hydraulics with no servos. The guy built it from the original schematics. In the future I like to incorporate a similar system to the current version(non removable or foldable wing) of the Sal 2/3 P-51 that I'll be building ages from now.
 

Midniteoyl

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I really like that... Even if it was electrical vs hydraulic. Simplist would be manual with a rack and pinion for locking operated by a drill driver through a small hole in the bottom of the wing.
 

Topaz

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If you're inquiring about the Hellcat, they are doing a total restoration; in some places a complete teardown. It looks factory-new with fresh green chromate primer and bare rivets. You ought to check it out.
I was, and cool. The airplane wasn't in bad shape before, but it's great that they're going through it: Chino nearly always does flying restorations, so I'll expect to see the Hellcat airborne at a future Chino air show! :gig:
 
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