Mitchell Wing B10 Hang Cage design

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by rivilee, Mar 30, 2019.

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  1. Mar 30, 2019 #1

    rivilee

    rivilee

    rivilee

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    I am going to gingerly dip my toe in and see if the whole thing gets bitten off or just a little nibble.

    My brother and I (mostly him) built and flew (mostly me) a B10 back during the ultralight craze. It was a "wow" experience except for the hang cage. Not that the cage was a bad design but it didn't have the finished quality like the wing did. Also, even back then when I was closer to 100 pounds than 200 it was still a hassle getting in and out of. Now, even more so.

    So, I've got the wing and the demolished parts of a hang cage and the plans that I bought a couple of years ago. The wing had very little damage but the covering is all off and I'm rebuilding it.

    The cage was bolted together aluminum tubing and didn't like anything approaching hard landings. I'm not going that route. Probably foam/fiberglass.

    I've got years of fiberglass experience, built my own shop and all necessary tools. Not an A&P but worked for Lancair in Santa Paula and have messed around with airplane building off and on.
    Heres the thing: I know how to think like an engineer, but I'm not one so I would love to have some input. Through the years I've read everything I could find about the Mitchell stuff and I don't intend to change anything about the aerodynamics of the wing.

    The attach points to the wing are fixed. Thrust line is known and pretty much fixed but it depends on the hang cage. Control linkage doesn't really need to change. Rudder cables can be lengthened/shortened without issue, and the mixer box for the for the push pull stabilators are all in the wing
    I'm planning on higher landing gear and slightly bigger tires. Shouldn't be any aerodynamic issues because that's been done before with bicycle tires, etc.

    However, I would like to get more headroom, even if it's just an inch. Some people have stretched the cage up to a foot but I'm not tall so that's not something I plan on doing. Don't know if anyone has "dropped" the cage. Pitch is pretty sensitive with the mixer box and they made it less sensitive in the A-10 (aluminum wing) by basically making the stick longer. So my initial thought is that dropping it shouldn't change much. The C/G is narrow but the pilot is on the C/G so it should mostly be pendulum(?)

    I will need to be careful about the windshield. In the past it affected pitch sensitivity as you approached VNE. They figured it out but I don't know what they did.

    Basically I would like it to look a little like the original cage with the pod attached. However, I would like to design a structure that carries the load from the wing attach points to behind the pilots seat. Kind of a reverse "C" kind of structure.

    Anyway, I wanted to get this posted for motivation to get going on it. I'll sketch out some ideas later. I plan on finishing the wing this summer and get the cage going as I'm finishing the wing.

    Any ideas are appreciated.
     
  2. Mar 31, 2019 #2

    Hot Wings

    Hot Wings

    Hot Wings

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    Move the mixer to the rear spar and run it to a center stick under the pilot. That means moving the push/pull rods aft as well - but it gets rid of that bend in the left one and you can modify the ratios to suit your preference.

    Dropping the stock cage by adding longer attach links is easy but it really needs a new 'from scratch' cage. This guy doesn't have the diagonal tube on the side to block his entry: B-10 Back View.jpg
     
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  3. Apr 4, 2019 #3

    rivilee

    rivilee

    rivilee

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    Thanks for the input. I had heard the idea about moving the mixer (maybe from you?) on another forum and it's a good idea. Would be nice to have the stick on the floor- it gets old holding the stick from the top. Peter Rosti wrote an idea to modify the mixer box to correct adverse yaw which also looks interesting.
    I've never seen that picture but it looks like it works! Simple but crush pretty badly in a crash. Looks like both sides are open. Anyway, that's the direction I want to go where the load is carried to behind the pilot but where the nose gear would crumple first.
    Hopefully I can figure out how to upload - here's the original cage
    Webp.net-compress-image.jpg
    I'll use a copy and redraw it with the rough idea of what I envision. It'll take me a few days....
     
    Last edited: Apr 5, 2019
  4. Apr 4, 2019 #4

    Hot Wings

    Hot Wings

    Hot Wings

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    No, not me. This is the first time I've publicly mentioned my thoughts on this. One idea below - with some unrelated garbage thrown in.....

    As for the crush factor on the other cage design, I agree it may not be quite as good as the original, but with just a bit more development, it could actually be better by soaking up more energy in a progressive way.

    Control system - working - test.JPG Control system - working - test2.JPG
     
    Last edited: Apr 4, 2019
  5. Apr 4, 2019 #5

    Hot Wings

    Hot Wings

    Hot Wings

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    and just another visual aid. The little red tube is the stock CG. The 'flats' in the spar stubs are the chord line. Wheels (wheelbarrow, not the original spec) are in original location and give the original ground angle.
    (Can't seem to add photos using edit?)
    Fuselage assembly - #1a.JPG Fuselage assembly - #1.JPG
     
  6. Apr 4, 2019 #6

    proppastie

    proppastie

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    here is the pod assembly of the Carbon Dragon....wood...but perhaps glass covered foam could substitute. (engineering required)

    Full plans are from the Irish site on my signature block
     

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  7. Apr 5, 2019 #7

    rivilee

    rivilee

    rivilee

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    Oh my goodness. Y'all aren't laughing at me! Thank you. I'm floored. Without looking at your ideas yet I'll post the hand drawings I made. Sorry, I haven't learned CAD programs even though I've had plenty of opportunity. The first is the original side drawing without extraneous features.
    img6.jpg
    The second is the rough idea I've had in my head for a while. It roughly incorporates the shape of the A10 (aluminum wing version) pod but makes it the actual structure. It would be a laid up foam/fiberglass structure using thin strips of foam laid up the same way you build a woodstrip canoe. And if it worked really well it would be simple to make molds if others wanted it.
    B10 custom hang cage raw04042019.jpg
    Or maybe do something like the Ranger ultralight where the "keel" is the narrow Ranger idea with the crumple zone built in. I would still want a pod on the front. Actually that may be a pretty cool idea. Have the front part a "keel" and then spread it out at the seat.


    I would like to figure a way to not have any tubes coming up to the front attach points. The biggest "I don't know the engineering to make it work" is having the "C" structure where the front attach point load is carried horizontally back to the "backbone" right behind the pilot. Maybe a robust aluminum cage at the top? Maybe carry part of the hang cage structure up into the wing?
    I know the front spar carries the load. The rear spar carries some load of course but not much. On the B10 I have the rear spar gave way (It was a hard nosewheel landing and the front crumpled). The D spar wasn't damaged at all.

    Aerodynamically air flows fairly unobstructed between the pilots head and the bottom of the wing. My idea would restrict that flow at least somewhat.

    Anyway, I'm gonna look through your ideas. Wow.
     
  8. Apr 5, 2019 #8

    Hot Wings

    Hot Wings

    Hot Wings

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    I personally like the idea of using composites and imitating the Ranger idea.
    << >>
    The rear spar caries more load than it appears at first glance. The CG is actually pretty far back from the front spar wing fittings. There is a reason this section is so robust. The red star is the CG.
    CG B-10.jpg
     
  9. Apr 5, 2019 #9

    rivilee

    rivilee

    rivilee

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    Oh yeah, I wasn't thinking about the cap strips and how much load they can carry. You're right. Mitchell knew what he was doing. And on a flying wing the aerodynamic center is slightly behind the CG. No idea exactly where especially with the stabilators providing downward lift.
    I like the idea of the Ranger too. A motorcycle flying wing... Might help keep the weight down also.
     

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