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Thread: Folding wing designs?

  1. #1
    Registered User rtfm's Avatar
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    Folding wing designs?

    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
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  2. #2
    Moderator addaon's Avatar
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    Re: Folding wing designs?

    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.

  3. #3
    Registered User rtfm's Avatar
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    Re: Folding wing designs?

    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
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  4. #4
    Registered User craig saxon's Avatar
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    Re: Folding wing designs?

    You can glean a lot from a patent search....

    AIRCRAFT FOLDING WING CONSTRUCTION - Google Patent Search

    Craig

  5. #5
    Registered User HumanPoweredDesigner's Avatar
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    Re: Folding wing designs?

    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.

  6. #6
    Registered User pwood66889's Avatar
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    Re: Folding wing designs?

    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

  7. #7
    Registered User WonderousMountain's Avatar
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    Re: Folding wing designs?

    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

    PM me if you have any more trouble with this.

    Blessings,

    Wonderous Mountain

  8. #8
    Registered User rtfm's Avatar
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    Re: Folding wing designs?

    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.
    Folding wing designs?-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
    ====================
    Brisbane, Australia
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  9. #9
    Moderator Dana's Avatar
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    Re: Folding wing designs?

    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

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  10. #10
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    Re: Folding wing designs?

    RTMF......what type of aircraft did you have?

  11. #11
    Registered User GESchwarz's Avatar
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    Re: Folding wing designs?

    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.
    If you see something, say something.

  12. #12
    Registered User Hot Wings's Avatar
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    Re: Folding wing designs?

    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.

    Folding wing designs?-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.
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    Registered User skeeter_ca's Avatar
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    Re: Folding wing designs?

    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.

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  14. #14
    Registered User Mac790's Avatar
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    Re: Folding wing designs?

    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
    Attached Thumbnails Attached Thumbnails Folding wing designs?-1.jpg  
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  15. #15
    Registered User GESchwarz's Avatar
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    Re: Folding wing designs?

    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.
    If you see something, say something.

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