Build your own HO229 WW2 German Jet Fighter!!

Discussion in 'Hangar Flying' started by Aerowerx, Jul 14, 2019.

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  1. Jul 24, 2019 #101

    pictsidhe

    pictsidhe

    pictsidhe

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    Each design has it's pros and cons. The conventional 103 I am working on only has around 1/2 of it's surface area in the wings. That's a lot of parasitic drag that could be lost. But a BWB would not achieve as high a CL as easily, so I wouldn't see a 50% drop in parasitic drag. Conventional planes are better suited to E spanloads, so they have less span for a given induced drag. But they'll be heavier.
    There are no best choices. At the end of the day, there is the sum of the parts. That is why there has been such a variety of aircraft shapes.
     
  2. Jul 24, 2019 #102

    Speedboat100

    Speedboat100

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    But flying wings are under represented grossly.
     
  3. Jul 24, 2019 #103

    Red Jensen

    Red Jensen

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    Juke/TopSpeed100/Speedboat100

    Because most people, yourself included, don't understand the benefits of a non-elliptcal span load as it applies to the flying wing problem.
     
    Last edited: Jul 24, 2019
  4. Jul 24, 2019 #104

    pictsidhe

    pictsidhe

    pictsidhe

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    Maybe their vociferous oponents put non technical people off them?
     
  5. Jul 25, 2019 #105

    BJC

    BJC

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    How do you tie the tail down to prop a flying wing?

    How do you lower an up-wind wing and use opposite rudder to land in a crosswind?

    How do you slip to lose excessive altitude on short final?

    How do you recover from, for example, wake turbulence?

    How do you perform a hammerhead without a rudder?

    How do you recover from a spin?

    How do you deal with the “sink before the increase in lift” during the flare on landing?

    Thanks,


    BJC
     
  6. Jul 25, 2019 #106

    Aerowerx

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    These aren't all design related questions, but I will try to answer them the best I can.
    You don't, since there isn't a tail. Most of the designs are tricycle gear with pusher props. The design that I am working on has electric start so I can put the battery in the nose to adjust the CG. If you had to, I would tie down the landing gear. Also, I am considering a skid extending under the prop to protect it from ground strikes. That would be one place to tie it down.

    Drag Rudders. And since flying wings don't have a draggy fuselage, they don't mind crosswinds anyway

    You don't, since slips require a fuselage to generate all that drag in a slip. Instead you use some type of drag flaps or spoilers like a high performance sailplane.

    Good question

    No problem here. Just don't do aerobatics.

    No problems here either. A properly designed flying wing is spin resistant. There are pilot reports from WW2 Germany that the Horten's test pilots were unable to induce a spin on some of their flying wings.

    Not sure what you mean here. Maybe the same way as in any other aircraft?


    Are these legitimate questions or just a way to show why flying wings won't work?
     
  7. Jul 25, 2019 #107

    Speedboat100

    Speedboat100

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    I think I do. I have a solar powered flying wing design...with twin rudders that also house the tail wheels....and it has only one retractable main gear...not necessarily my invention...but solves a lot of weight and drag issues.

    Solar power with two pusher electric motors in a flying wing is a spot on mean of propulsion..as the flying wings seem to have excess surface area...and you can even add more if you have enough sweep. Not too much sweep as it becomes the new Aquila. https://www.theregister.co.uk/2018/06/27/facebook_kills_aquila/

    Red....when does the flying wing R/C model beat the Spencer Lisenby 545 mph record in DSS ? Go for it !

    Horten HX is available: https://edition.cnn.com/travel/article/horten-flying-wing-prototype/index.html
     

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  8. Jul 25, 2019 #108

    Speedboat100

    Speedboat100

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    All these a bird can do using the tail as a rudder.
     
  9. Jul 25, 2019 #109

    Red Jensen

    Red Jensen

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    Juke,

    I'm still waiting for you to explain to all of us the differences between ESLD and BSLD. Anybody and doodle on paper.
     
  10. Jul 25, 2019 #110

    Aerowerx

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    [​IMG]

    There is only ONE elliptical distribution, but an infinite number of bell-shapes. You have to pick the optimum one. IIRC, sin(x)^2.5 is usually taken as optimum.

    Note that in the curves the bell shape has left lift at the tips, which helps prevent wing tip stall. And also note that the lift is greater at the center, which means that the spar can be lighter because it doesn't have to handle the bending moment from the force at the tips.
     
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  11. Jul 25, 2019 #111

    Aerowerx

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    The topic here is using the tail for stability, not control. It has been stated that bird tails are a control surface.
     
  12. Jul 25, 2019 #112

    Speedboat100

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  13. Jul 25, 2019 #113

    Speedboat100

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    What I am interested is..whether rudders are a better way to achieve normal flight envelope or drag devices in a flying wing ?
     
  14. Jul 25, 2019 #114

    Red Jensen

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    Last edited: Jul 25, 2019
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  15. Jul 25, 2019 #115

    Speedboat100

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    Good question..it just happens to be that flying wing distribution sorta distorts due to negative lift on the wing tips.

    Here you can find out how it looks like: https://www.rcsoaringdigest.com/pdfs/RCSD-2003/RCSD-2003-01.pdf
     
  16. Jul 25, 2019 #116

    pictsidhe

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    If I do build a flying wing, it will likely have tubular drag rudders that telescope out from the wing tips.

    Back to spanloads.
    For straight wings, the span efficiency drops as the exponent increases:

    sin = 1.0 (eliptical)

    BSLDs:
    sin^2 = 0.90
    sin^2.5 = 0.83 (neutral yaw)
    sin^3 = 0.76
    sin^4 = 0.65

    Since the induced drag varies as the inverse square of span, we can normalise the induced drag with the reciprocal of the square root of the span efficiency. sin^3 would need 15% more span than an elliptical wing for the same induced drag. But it will have a 16% longer root chord and also a smaller root bending moment. Both help with structural strength. Sin^3 has a small amount of proverse yaw. Sin^3 was Prandtl's favoured lift distribution.
     
  17. Jul 25, 2019 #117

    pictsidhe

    pictsidhe

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    No, BSLD has positive lift all the way along the span, but because of the twisted downwash distribution, the induced drag becomes induced thrust part way along the span. For sin^3, this is at 71% of span.

    The SB13 had an elliptical distribution. It was museumed due to inadequate short period pitch damping.
     
  18. Jul 25, 2019 #118

    Speedboat100

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    It had rudders/winglets.


     
  19. Jul 25, 2019 #119

    pictsidhe

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    Yes, yaw is harder to control with ESLD. it also had little sweep. But it could be done without vertical surfaces if you really wanted to. BSLD is easier to control the yaw, so vertical surfaces are less attractive. More sweep helps with yaw stability. it will also increase short period pitch damping, the SB13's nemesis.
     
  20. Jul 25, 2019 #120

    Red Jensen

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