Stability in a swept wing with no washout from the elevons alone.

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Michealvalentinsmith, Dec 3, 2009.

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  1. Feb 24, 2011 #301

    Topaz

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    Generally a compliment: Fabulous = "great", "wonderful", "outstanding", etc.
     
  2. Feb 24, 2011 #302

    henryk

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  3. Mar 2, 2011 #303

    henryk

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  4. Apr 30, 2011 #304

    Rol

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    To see the first flight of the Klingberg Wing go to YouTube - Klingberg Wing First Flight.wmv
    I'll be posting more video of it soon.
    Boy, the folks talking about the stability of flying wings must not be engineers and they really don't know much about my Wing. I don't suffer fools gladly which is why I moved out of the public eye, but I'm bored tonight, so I'll have some "fun". Here are the facts - the Klingberg Wing employed a bell-shaped lift distribution based on the work of the Horten brothers. The bell shaped lift distribution provides reasonable static stability for pitch, roll, and yaw. What a lot of people don't understand and hence “forget” to talk about is dynamic stability. This is a very complex subject compared to static stability as it is controlled by damping rates which required some high powered calculus to calculate. Dynamic stability of flying wings is very challenging and requires the balancing of many design factors. The Klingberg Wing gained most of its dynamic stability via airfoil selection, wing twist, and by keeping the vast majority of the gross weight as close to the centerline as possible. Now, remember that any flying wing that uses a bell-shaped lift distribution will have significantly lower performance than a conventional configuration (with tail) due to the fact that the effective span is much less (lift distribution is non-optimal). This is because the last 20 to 30 percent of each wing is performing the function of a horizontal tail. The often stated fact that a flying wing will have superior performance due to lower drag is generally false. Only if it is very carefully designed to have minimum drag, will it have the same or superior performance to a "normal" configuration. There are some exceptions to this fact that are only recently afforded by computer control systems because the designer can go with a statically unstable configuration and let the computers keep everything lined up in flight. Going down this path allows a lift distribution much closer to the optimal elliptical form. I designed the Klingberg Wing as a pure wing mostly for factors other than performance. It made transportation much easier, the weight lower, and most importantly, much easier to launch. Try running down a hill with a 100 lb hang glider (my Wing was 85 lbs) with a tail dragging on the ground and you’ll understand my point. Now, to the meat of the matter about adverse yaw during a turn on a pure (no winglets or other vertical surfaces) flying wing. Now, read closely. What everyone seems to not understand is that adverse yaw means NOTHING to a pure wing. This is true for yaw angles up to 20 degrees or so (quite extreme). For a pure wing, there is no performance change no matter where the "nose" is pointed. What matters is flight path. The problem is one of pilot perception. When I taught people how to fly my models, once they learned to ignore where the nose was pointed, there were no more problems. The same was true for the full size wing. It is just a “problem” of pilots being conditioned to expect to have the nose pointed in the flight path direction. This is very important for conventional configurations (due to drag), but is virtually meaningless for pure wings. So, this whole argument about adverse yaw with pure wings is entirely pointless. It simply doesn’t matter to the aircraft. For some flying wings, adding winglets can allow a slight increase in performance and for those designs, adverse yaw IS an issue because of the related drag. Moving on; due to so many “armchair engineers” worried about this yaw “problem” I added the Autoyaw system I invented to the various models of the Klingberg Wing (afterall, I wanted to sell more of them). For those who used the Autoyaw system, the “problem” was solved. Plus, it was much easier to tow the glider and it made the launch of the Klingberg Rocket Wing much more pleasing. Bottom line, if you have a pure flying wing, stop worrying about the adverse yaw “problem” and leave the design work to the engineers. Just go flying, pay attention to the flight path, ignore where the nose is pointed, and have a fun flight!
     
    Last edited by a moderator: Apr 30, 2011
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  5. Apr 30, 2011 #305

    Norman

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    Such is the nature of an open forum, Mr Klingberg, everybody gets to talk. Thanks for the video

     
  6. May 4, 2011 #306

    henryk

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    YouTube - Klingberg Wing Flight Tests

    -I see=this type of the wing is NOT a tumble-resist!
    \small dumping surface of the tips\...

    L/D=20 -not good for this AR...
    \to compare with L/D=29 with AR=10 at BKB1-A, TUMBLE-RESIST\
     
  7. May 4, 2011 #307

    Norman

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    Hi, Henry--

    Although large wing tips can help stop a tumble the root cause is inertial as explained in NASA-TM-111858. Basically it's caused by the center of gravity of the half span being too far outboard and a short static margin. So properly balanced tapered 'wings are less likely to get into a tumble in the first place
     
  8. May 5, 2011 #308

    Norman

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    Sometimes these NASA videos are blocked from playing in an embedded window so if you want to see these tumble tests in the vertical wind tunnel you'll probably have to go to Youtube
    [video]http://youtu.be/vEl529ImNzs[/video]
    [video]http://youtu.be/bsPMDV29u-E[/video]
     
  9. May 5, 2011 #309

    henryk

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    Bibliografia - Brochocki Kasprzyk Bodke

    23. "Tailles Aircraft", by K, Nickel, M. Wohlfahrt, 1990 pp. 213 24.

    -iff I remember,citation from the "23",pp.213=

    BKB1-A is the only one tumble-resistent flying wing...?


    BTW=constructiv paper=

    AERO ELASTICS OF
    LIGHT TAILLESS AIRCRAFT
    By I. H. Culver
    November 22, 1986

    from=

    No. 203 MAY 2003
    T.W.I.T.T. NEWSLETTER
     
    Last edited: May 5, 2011
  10. Dec 20, 2011 #310

    Keshka

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    Well read the entire thread, got most of it. One thought came to mind. (not the mind of an engineer!) if control surfaces and stability are problem then what if a stabilator wing tip were used instead of sprogs, ailerons or spoilers. See my drawing:
    WING.jpg
     
  11. Dec 21, 2011 #311

    Keshka

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    Got to thinking about it.....plan A would not provide any pitching moment. Perhaps plan B. Now this would be a pain to build!
    wing 2.jpg
     
  12. Dec 28, 2011 #312

    Aircar

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    Congratulations!-you have reinvented the NASA "C" wing --see Moller Skycar for the only known embodiment (but unflown,still) --several transport aircraft studies and papers by Ilan Kroo et al detail the type and the spiroid 'winglet' is closely related but none of them contribute much to stability or control . Wing tip boom mounted control surfaces are known and can give high wing L/ds if the elevators lift --the McGinnis Synergy is another with a family connection to the closed loop type wing .

    Flutter is a concern with any aerodynamic surface with an aft mass and flexibility or moving surfaces but the possibility for good flutter damping also exists and even the concept of a complete flying configuration in it's own right mounted at the tips exists and could be interesting and flutter resistant (the Grumman Panther had a miniature aircraft (canard) as a tail (T type) in seeking non servoed control and trimming a sweeping wing --other experiments with actual aircraft attached but freely pivotted to the wings of a much larger aircraft (eg B29/ 2xF84) have also been conducted -- zero bending moment connections allow for roll and pitch inputs and something like a tip tank could function to connect a set of small airfoils at the tip .
     
  13. Jan 3, 2012 #313

    Keshka

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    My fault aircar, I was not clear enough in my drawing or description, try this, the green and pink areas would be the control surfaces:
    Picture0012.jpg
     
  14. Jan 3, 2012 #314

    Aircar

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    That's what I understood --there is very little pitch control margin (horizontal volume co efficient equivalent ) although probably good roll authority (except that the pressure fields on the wing and the top branch of the C tip tend to mutually cancel (interfere) to some extent (it is the same interaction as for the Synergy so john Mc G might want to comment if he is watching this thread... imagine commanding a 'wing down' on the tip nearest to us (the bottom right corner) this requires negative AoA on the Horizontal part of the "C" --thus low pressure on the bottom of it which will tend to raise the main wing ("Fighting" the roll input) --also the roll damping due to rotation will be great unless you put "ailerons" on both surfaces (this logic applies to pitch control as well ) --you really need to take the horizontal arm of the C well aft of the main wing for effective leverage and to avoid mutual interference I would think --there are reflected pressure effects for the fin on the wing also .
     
  15. Jan 4, 2012 #315

    Norman

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    I think this might be a good place to insert his latest video:[video=youtube;EmZjF3X-QZ8]http://www.youtube.com/watch?v=EmZjF3X-QZ8[/video]
     
    Last edited by a moderator: Mar 20, 2019
  16. Jan 22, 2012 #316

    Rol Klingberg

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    So, what's wrong with adverse yaw in pure flying wings? There are no vertical surfaces to cause extra drag; the wing doesn't know any difference. One wing is further forward (more efficient) and one further aft (less efficient). The effects cancel and there is no net change in performance. So, tell me, what makes adverse yaw in a pure wing something bad?

    The Klingberg Wing had linear twist. There is no such thing as a "Horten twist" - it is an urban myth (see the book Nurflugel; http://www.amazon.com/Nurflugel-Ges...=sr_1_1?s=books&ie=UTF8&qid=1327210491&sr=1-1). The Horten designs used a bell shaped lift distribution to achieve yaw stability. This distribution can be created by airfoil changes, taper, and/or twist. The Klingberg Wing employed a bell shaped lift distribution nearly identical to the Horten III.

    More than 5000 models kits were sold of the Wing. Some folks loved them, others couldn't get them to work. Without exception, the ones that didn't fly well had the wrong twist in the wing due to not using the proper jig or other poor building methods.
     
  17. Jan 22, 2012 #317

    Norman

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    I guess that depends on the mission. Horten also mentioned that small side slip angles weren't a problem and I've had MitchellWing pilots tell me that their had seen the plane stay straight and level without a power increase while skidding 20 degrees (estimated from a yaw string). The problems I foresee are with regard to things you may want to do other than fly. The prospect of landing sideways doesn't sound appealing to me. At the least you're going to have to replace tires more often and in a hang glider it seems like just one more way to get injured. The only common use for flying wings right now, other than toys, is unmanned video reconnaissance. Low directional stability would show up in the video as a wobbly picture. And of course there's the problem that killed Northrop's bomber. Unsteady bombing platforms couldn't put bombs on target until JDAM.
     
  18. Nov 18, 2012 #318

    menamiketrx

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    I have been using paper airplane design and construction since 1973 to experiment with hang glider style designs, and developed a folding method does that quite well in duplicating the wing twist employed in modern hang gliding design. If interested in learning how to fold the craft which I have named as the OmniWing, you can either go to my web site at www.omniwing.com, or do a search on YouTube for the OmniWing. Several designs and modifications as well as videos showing the wings in flight. My 30 years of working with this platform has been a great and inexpensive tool in providing a working model in which I can experiment with twist, washout, airfoil, sweep, dihedral and more. Would apprecitate any input from the community.
    Mike Kelsey
    Where I fly www.ouachitahanggliding.com
    Local Clubs www.buffalomountainflyers.org and www.centralarkansasmountainpilots.org
     
  19. Nov 19, 2012 #319

    flyoz

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    Wow
    I wish i had seen this before !
    Built the first one and it flew straight out
    Thanks for sharing
    Flyoz
     
  20. Jan 7, 2014 #320

    markwirtz177

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    This is my first post on this site, but I'm so glad I stumbled across this. I have been very interested in finally designing my life long vision. I will start it off as a rag and tube/ ultralight hang glider design, then hopefully get it to the carbon fiber state in the future. It is similar to the HortonX concept. It uses two rotax motors with internal fan props, motorcycle like contols, the ability to launch from foot and ability to power up towards the sun!
     

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