Folding Wings, Aircraft Trailers, and Portable Hangars for Inexpensive Storage

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Hot Wings, Jul 21, 2013.

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  1. Jul 21, 2013 #1

    Hot Wings

    Hot Wings

    Hot Wings

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    A suggestion was made on another thread that maybe it was time to start a thread devoted to folding wings, aircraft trailers, and other methods of making aircraft storage inexpensive and convenient. Here it is!

    This was prompted by the desire some of us have to develop a truly user friendly method of taking a small plane like an ultralight (US definition) LSA or LSA motorglider home after each days flying.

    To start:

    What dimensions would be considered the maximum for legal highway transport - and in what countries?

    How long should it take from parking at the field until the plane is ready for preflight inspection?

    If the wings need to be handled individually what would be the maximum weight, chord and span that the average pilot can handle alone?

    How many of us would consider a covered trailer to be a significant advantage?
     
  2. Jul 21, 2013 #2

    autoreply

    autoreply

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    First of all, we should distinguish between a plane that can be broken apart, maybe a few times in the lifetime of a plane for maintenance, after landing on a field with damage, or going to the paint shop and daily assembly, which is completely different.

    Maximum dimensions for parts that can be disassembled IMHO must always fit in a 40' high cube container. That often means removable landing gear and a wing/fuselage combo that can be taken apart. This shouldn't be more than a few hours of work. Not having to rely on external tools/cranes is a massive advantage if you get stuck somewhere (collapsed LG, engine-out landing in a field)

    For daily assembly/dis-assembly the requirements are vastly more restricting. A 10-minute assembly is far too long, let alone half an hour. 2 minutes IMHO is about the max. Some things that from my point of view are essential to any plane that in the real world can be assembled/disassembled daily:
    1. All bigger parts stay permanently attached to the airplane on at least one side.
    2. Absolutely not a single tool is needed to "fold" the plane, except from a single bolt (M6/ 1/4")
    3. In 25-kts winds, a single person must be able to assemble/disassemble the plane himself.
    4. All controls MUST be automatic and impossible to rig incorrectly.
    5. Locking occurs via a single device, visible on the outside, preferably from the cockpit.
    6. It must be fundamentally impossible to get a visual lock while the wing/tail is incorrectly locked.
    7. Folding mechanisms musn't be structures that cope with flight loads.
    8. Folding mechanisms must be weak enough to break long before flight load carrying structures are overloaded. A safety cable is recommended..
    9. Crash strips on extremities are necessary to spot potential damage. Think of a single layer of glass/wood on a tip or spar stub.
    10. The folded plane must have considerable weight on any wheel. Any tendency to tip over will sooner or later result in a blown-over plane or damage in a hangar.
    11. Hard points (M6/ 1/4" thread) are essential for emergencies. Don't forget to carry a bit of rope and some threaded hooks along too.
    12. Having a maximum height (or a max height, excluding the tail) that doesn't exceed the wing's clearance of a C172 is highly desirable. Think weather deviation, CB's, nice hangar with a C172 in it...
    13. Rolling in and out of the trailer should be feasible for a single person. Figure 100 lbs push (less slope if heavier).
    14. No significant (>50 lbs) weights should be lifted outside of the envelope between knees and top of the head.
    15. Total time from unlocking the trailer to having an airworthy plane (save the pre-flight) shouldn't exceed 150 or so seconds for a pilot that has practiced it a few times.

    Some food for thought:
    Assembling a plane, perfectly fine for the once a year occurrence, utterly unacceptable for daily use.


    One of those very rare planes that meets most of the above requirements, except the locking mechanism visibility from the cockpit:


    Inspirational, not necessarily wise. I can however start with a closed trailer and assemble, tape, pre-flight and install myself in exactly this type of sailplane in well under 5 minutes, with about 2 minutes help from a friend...
     
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  3. Jul 21, 2013 #3

    cluttonfred

    cluttonfred

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    How about this...

    6391981139_1c2ac537b7_z.jpg

    which folds like this...

    [video=youtube_share;T6Q1yReILJc]http://youtu.be/T6Q1yReILJc[/video]

    and will fit inside any of these....

    black7X14(side).jpg 10W.jpg 59556lk_20.jpeg

    For anyone who doesn't know, I am editor of the non-profit fan site for Eric Clutton's FRED. ;-)

    Cheers,

    Matthew
     
  4. Jul 21, 2013 #4

    X3 skier

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  5. Jul 22, 2013 #5

    BBerson

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    My ultralight has removable wings, 14'x4', and weighs about 35pounds each. Each wing can be lifted and carried by me and will plug- in easily (by one person), much like a RC model. The details of attachment are not to be released until tested.
    I expect the wing installation to be less than 10 minutes. But I hardly care about time spent at the airport fussing around preflighting. I enjoy this time. It is the strain of heavy lifting that bothers me while assembling the 300 pound Grob wings.

    I will build an enclosed trailer eventually.

    It two days, I have an appointment with airport managers to discuss building a new ultralight runway.
     
  6. Jul 22, 2013 #6

    autoreply

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    Not even close. There is a locking mechanism that it totally invisible, whether you're walking around the plane, or sitting in the cockpit. Sooner or later, somebody is going to screw that up. The last plane I flew in with such a mechanism (RF5B), it's "sister" crashed. Both pilots are 6 feet under now...

    Push-push aileron control? All fine. But after 100 hours you'll have more and more slop into the control system, resulting in wear in the automatic connections too.

    Folding via the primary load carrying structure in flight. Leave it outside with a bit of the right wind and it'll tear out those holes easily. If not, a local kid will do it. You won't notice it till the wing let's go.
    Or just imagine what happens when I put the slightest load on the leading edge. Indeed, now your spar is bent and probably buckled. Outcome is the same, you're very much dead.

    After a decade (and probably being involved in putting planes together over 1000 times), I can guarantee you that the first lethality isn't far away...
    Sooner or later, those wings will be damaged. You'll hit a hangar door, they'll get blown away in the wind etc.
    You do now. But it'll still hold you back for a quick/short flight. Not now maybe, but eventually. Much more so for future customers.
     
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  7. Jul 22, 2013 #7

    Tiger Tim

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    If your plane is of a normal size, why not just share a real hangar? A rectangular hangar big enough for a 172 will easily fit three non-folding homebuilts, or the end hangar in a row of T-hangars can fit two airplanes.

    -Tim
     
  8. Jul 22, 2013 #8

    autoreply

    autoreply

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    Aside from finding somebody to share that hangar with, not every place is blessed with affordable hangars. Here for example, the cheapest hangar you can find NOW for say a C172 is about 1500 US$/month. I have a strong impression it's the same on the west- and east coast of the US. In between it's probably a non-issue, but for many - if not a majority - of the pilots it's what makes flying prohibitively expensive.
     
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  9. Jul 22, 2013 #9

    Vigilant1

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    In the US, most states have a trailer width limit of 8' (unless a special permit is sought/granted). This link shows the dimensions by state. So, giving maneuver room inside the trailer, etc that puts the max width of an aircraft inside an enclosed trailer to be something like 7' to 7'6" max. Keeping the overall height of the folded aircraft to less than 7' will allow it to fit in the door of a standard shipping container (which makes a very sturdy mini-hangar). Shipping container dimensions.

    For daily use, I'd have no problem spending 10-15 minutes putting it together. But it's absolutely critical that it be a one-person job. Also, I'd prefer that it not require me to crawl under the plane--that's inconvenient at all times, and a downright PITA in a few inches of snow.

    I'm with Autoreply--one end of all the big parts must stay affixed to the fuselage. With that done, fairly big parts can be managed.

    Not clear on this question. I'd say a covered trailer is a huge advantage over an open one (I can leave the plane on the trailer for storage, keeping it out of the weather). But if the question is "will your local airport allow you to keep a trailer on their premises?" -- I haven't asked that. Given the lack of hangar and their high cost, being able to keep the aircraft in a 40' shipping container or on a trailer right at the airport would be a very big advantage.

    Adding to AR's very useful list:
    -- Keeping the overall height of the folded aircraft to something less than 7' allows it to be rolled into most US garages, older small hangars with lower doors (built for TD aircraft). I think the Onex missed the boat by folding the wing panels up rather than pivoting them alongside the fuselage. If you are trailering the aircraft because you don't have a hangar at the airport, where will you work on it? Probably at home, and that may mean putting into a garage periodically. So, low height is good.

    Some wing fold mechanisms I like:
    - Thorpe/Sunderland S-18/Mustang II: 8 "Mustang 2" Trailer-able Aircraft Wing Folding. - YouTube
    Very quick. Ailerons are actuated by "push paddles" on mating bellcranks, there's nothing to hook up. The Sonex Onex adopted the same system.
    - Thatcher CX4:
    [​IMG] Very simple and lightweight. The wing folding bracket is attached externally to the wing (so that takes a minute or so), but then it's an easy procedure to fold the wings.
     
  10. Jul 22, 2013 #10

    TFF

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    If your airport is municipally owned, they probably will not allow a trailer parked for more than a few days. They are cleaning house at my airport. A semi private one should not be too much of a problem. A lot of the problem is where to put them. Hangar and ramp space at a small grass strip; you might have to clear the land, and the airport might not own the fringe areas.
     
  11. Jul 22, 2013 #11

    Hot Wings

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    To answer some of my own questions and add to the wish list:

    I'd consider a covered trailer mandatory. Not everyone has enclosed storage space but they can find a side yard or back yard location to legally store a trailer. In my city they have to be off the street after 5 days.

    The trailer also needs tie down points. In my part of the world a typical glider trailer will end up next to a fence just as fast as a cardboard box if not behind a good wind break or tied down.

    To me the Onex folding method is only useful for mass storage at the airport. I'd need a total package of no more then 7 1/2 feet wide (230 cm) x 6 3/4 feet tall (205 cm) x 18 feet (550 cm) long so that it could be easily backed into the average single stall garage door. Anything smaller is a bonus. This probably means either a very high aspect ratio wing or at least a 3 piece wing with a wide center section.

    A agree with Autoreply's logic bout not using any of the primary load carrying members as part of the folding mechanism. The leverage one has while holding the wing tip can apply a much larger load than the fitting will ever see in flight, and from a direction for which it was not designed.

    Since we are building a trailer I see little wrong with making it a bit more complex to help with the handling of the assembly. This might make the use of wing panels that separate from the fuselage more practical? In any case the part being manipulated should be under control at all times to prevent wind damage. In other words there shouldn't be any point during the assembly where a part that is not fully assembled should be let go of unless it is captive in 3 dimensions and can resist a moderate wind gust.

    If the plane is going to be designed from the beginning to be stored in a trailer and assembled for each flight it might be good to remember that the plane doesn't have to be pulled down the highway on it's longitudinal axis. There is nothing wrong with travel with the wing span aligned with the road if the fuselage folds or breaks in 2 parts.
     
  12. Jul 22, 2013 #12

    Vigilant1

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    Maybe low aspect ratio? Anyway, I don't think the constraints are tough to meet for a two place plane. A standard US garage is 20 feet long, and a Sonex with a wing pivoting/folding back right where the main spar joins the fuselage would meet the width requirement and be less than 20 feet long in total. And, if longer wings are desired, the wing joint could be 18" out from the fuselage or the folding mechanism designed so that the wing is held at a location more forward on the fuselage.
     
  13. Jul 22, 2013 #13

    Norman

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    I seem to recall doing exactly that just recently. We got an entire airplane on an 8 by 12 foot flat bed trailer. We disassembled it for the 900 mile trip but for across town it'll be folded. With the nose cone removed it's barely legal. With a few modifications to the trailer it should be easy for one person to load and unload. Here's an article showing somebody else's custom trailer:
     

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  14. Jul 22, 2013 #14

    Aviator168

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    It is almost perfect. It is just too heavy for a single place.
     
  15. Jul 22, 2013 #15

    Vipor_GG

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    In the US the maximum legal width is 102" and maximum height is 13'6". These are the federal limits, there could be lower dimensions on some streets and under some overpasses. You can get enclosed trailers with up to 100" inside width, but a trailer this wide would require something other than factory mirrors even on a full size pickup or SUV. Even 96" wide trailers are a bit wide for the mirrors on some vehicles. To be able to safely see along the sides of the trailer it should be no wider than the distance center to center of your side mirrors. There are also length restrictions, but you shouldn't run into any issues with them with something as small as a LSA or ultralight aircraft.
     
    Last edited: Jul 22, 2013
  16. Jul 22, 2013 #16

    Vipor_GG

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    I thought the Onex had a locked/unlocked indicator on top of the wing visible from the ground or cockpit?
     
  17. Jul 22, 2013 #17

    cheapracer

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    There are plenty of mirror extensions avilable.
     
  18. Jul 22, 2013 #18

    Norman

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    There certainly are mirror extensions but I wouldn't want to pull a trailer that required them. I know of two people in Colorado who have had there heads knocked off by truck mirrors and I was a passenger in a truck that hit a road sign with an extension mirror.
     
  19. Jul 22, 2013 #19

    mcrae0104

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  20. Jul 22, 2013 #20

    cheapracer

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    And? There's millions of trucks in the world and nothings going to change that.

    But on topic, ie; car mirror extensions, hundreds of thousands of people have been driving around the world for a long time with caravans quite successfully.

    Also today one can economically fit video camera's as an aid.
     

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