Build your own HO229 WW2 German Jet Fighter!!

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

Help Support HomeBuiltAirplanes Forum by donating:

  1. Jul 22, 2019 #61

    Aerowerx

    Aerowerx

    Aerowerx

    Well-Known Member

    Joined:
    Dec 1, 2011
    Messages:
    4,803
    Likes Received:
    1,283
    Location:
    Marion, Ohio
    Are you guys talking about "CL" or "Cl" (local coefficient of lift) or center of lift???

    If center of lift, would it be better to use neutral point instead?
     
    Last edited: Jul 22, 2019
  2. Jul 22, 2019 #62

    Red Jensen

    Red Jensen

    Red Jensen

    Well-Known Member

    Joined:
    Jan 2, 2018
    Messages:
    65
    Likes Received:
    35
    Location:
    Palmdale, CA
    Sorry, Cl. Typing on my phone.
     
  3. Jul 22, 2019 #63

    pictsidhe

    pictsidhe

    pictsidhe

    Well-Known Member

    Joined:
    Jul 15, 2014
    Messages:
    6,441
    Likes Received:
    1,672
    Location:
    North Carolina
    Oh, so I'm not that far behind you!

    FWIW, I have a planform trick to eliminate needing to alter the twist of the inner half span with changing CL. The outer half has me thinking that wing warping is needed. I need to be much better at aeroelasticity to try that, though. Or go hydraulic. The devil, or the deep blue sea?
     
  4. Jul 22, 2019 #64

    Speedboat100

    Speedboat100

    Speedboat100

    Well-Known Member

    Joined:
    Nov 8, 2018
    Messages:
    569
    Likes Received:
    40
    Location:
    Europe
    I did not claim all flying wings need a rudder..but you could end up in an viable aeroplane when you have one...at least able to get a elliptical spanload with actual lift;
     
  5. Jul 22, 2019 #65

    AdrianS

    AdrianS

    AdrianS

    Well-Known Member

    Joined:
    Jul 5, 2014
    Messages:
    323
    Likes Received:
    179
    Location:
    Australia
    What would you call a bird-style configuration?
    They're not a true flying wing, but the "tail" is very closely coupled- about 2 or 3 chord lengths I'd say.
    The tail is usually oriented horizontally, either fanned to provide pitch/lift/drag or folded, but it can rotate to provide a yaw component.
     
  6. Jul 22, 2019 #66

    Speedboat100

    Speedboat100

    Speedboat100

    Well-Known Member

    Joined:
    Nov 8, 2018
    Messages:
    569
    Likes Received:
    40
    Location:
    Europe
    Yes but it also turns sideways like a rudder..if needed.
     
  7. Jul 22, 2019 #67

    AdrianS

    AdrianS

    AdrianS

    Well-Known Member

    Joined:
    Jul 5, 2014
    Messages:
    323
    Likes Received:
    179
    Location:
    Australia
    That's what I meant when I said it rotatea to provide yaw - it rotates about the longitudinal axis so the formerly horizontal surface is now partly vertical, and acts as a rudder.

    Did any of the early pioneers try this?
     
    Red Jensen likes this.
  8. Jul 22, 2019 #68

    Aerowerx

    Aerowerx

    Aerowerx

    Well-Known Member

    Joined:
    Dec 1, 2011
    Messages:
    4,803
    Likes Received:
    1,283
    Location:
    Marion, Ohio
    But the point is that it is used as a control surface, not for stability.
     
  9. Jul 22, 2019 #69

    pictsidhe

    pictsidhe

    pictsidhe

    Well-Known Member

    Joined:
    Jul 15, 2014
    Messages:
    6,441
    Likes Received:
    1,672
    Location:
    North Carolina
    I've seen a bird with no tail. It was a red kite. It flew pretty well, but not as gracefully as its tailed brethren.
     
    Red Jensen likes this.
  10. Jul 22, 2019 #70

    Red Jensen

    Red Jensen

    Red Jensen

    Well-Known Member

    Joined:
    Jan 2, 2018
    Messages:
    65
    Likes Received:
    35
    Location:
    Palmdale, CA
    The whole point is to NOT use and E spanload......you are still assuming that E is the most efficient way to design.
     
    Last edited: Jul 22, 2019
  11. Jul 22, 2019 #71

    Red Jensen

    Red Jensen

    Red Jensen

    Well-Known Member

    Joined:
    Jan 2, 2018
    Messages:
    65
    Likes Received:
    35
    Location:
    Palmdale, CA
    The Wandering Albatross is a bird with a vestigial tail, a fairing for the landing gear as it were. These birds are arguably the most efficient, travelling up to twice around the globe in 9 months while DS'ing waves. Land soaring birds that most people are familiar with do use their broad tails, but that is certainly not the only case.
     
  12. Jul 22, 2019 #72

    Red Jensen

    Red Jensen

    Red Jensen

    Well-Known Member

    Joined:
    Jan 2, 2018
    Messages:
    65
    Likes Received:
    35
    Location:
    Palmdale, CA
    You might like this:

     
  13. Jul 22, 2019 #73

    Speedboat100

    Speedboat100

    Speedboat100

    Well-Known Member

    Joined:
    Nov 8, 2018
    Messages:
    569
    Likes Received:
    40
    Location:
    Europe
    If you watched the video you'd understand that swept wing flying wing creates only E spanload.
     
  14. Jul 22, 2019 #74

    Speedboat100

    Speedboat100

    Speedboat100

    Well-Known Member

    Joined:
    Nov 8, 2018
    Messages:
    569
    Likes Received:
    40
    Location:
    Europe

    This is very interesting.
     
  15. Jul 22, 2019 #75

    Red Jensen

    Red Jensen

    Red Jensen

    Well-Known Member

    Joined:
    Jan 2, 2018
    Messages:
    65
    Likes Received:
    35
    Location:
    Palmdale, CA
    Not true at all.

    I give up, you clearly have everything under control. I'll sit back and listen.
     
  16. Jul 22, 2019 #76

    Aerowerx

    Aerowerx

    Aerowerx

    Well-Known Member

    Joined:
    Dec 1, 2011
    Messages:
    4,803
    Likes Received:
    1,283
    Location:
    Marion, Ohio
    If you read "Tailless Aircraft in Theory and Practice" and Al Bowers (and Red's) paper you would know that this is not true. The shape of the lift distribution depends on the local coefficient of lift and local angle of attack at each span-wise location.

    I suggest getting a copy of XFLR5, learn to use it, and play around with various configurations. Yes, it is a simulation, but from what I have seen it agrees pretty well with the real world if you don't get too far out in left field.

    Edit:
    I watched the video and see several problems with what he did. First, he used an elliptical planform, which forces an elliptical lift distribution. It is not because of the sweep that the lift is elliptical. Besides, he points out that the sweep destroys the elliptical shape anyway.

    He also did not use any twist to tailor the lift distribution.

    His "scimitar" shaped wing is a poor choice for two reasons. First, it puts more loading on the wing tips, which can lead to wing-tip stalls and result in a loss of control. Second, this shape has very poor lateral stability, because the air flow sees no difference in the wing leading edge as the wing yaws.

    He used a NACA 2412 airfoil, which is a poor choice for a tailless aircraft.
     
    Last edited: Jul 22, 2019
  17. Jul 22, 2019 #77

    Speedboat100

    Speedboat100

    Speedboat100

    Well-Known Member

    Joined:
    Nov 8, 2018
    Messages:
    569
    Likes Received:
    40
    Location:
    Europe

    See there are different opinions. Also the Re-number counts here.
     
  18. Jul 22, 2019 #78

    Speedboat100

    Speedboat100

    Speedboat100

    Well-Known Member

    Joined:
    Nov 8, 2018
    Messages:
    569
    Likes Received:
    40
    Location:
    Europe

    Unfortunately I did play with XFLR5. Yes the person seems to have a problem...and a poor foil choice.But he is right about sweep decreasing the lift. Unless a great speed.
     
  19. Jul 22, 2019 #79

    Red Jensen

    Red Jensen

    Red Jensen

    Well-Known Member

    Joined:
    Jan 2, 2018
    Messages:
    65
    Likes Received:
    35
    Location:
    Palmdale, CA
    No....no it doesn't.
     
  20. Jul 22, 2019 #80

    Aerowerx

    Aerowerx

    Aerowerx

    Well-Known Member

    Joined:
    Dec 1, 2011
    Messages:
    4,803
    Likes Received:
    1,283
    Location:
    Marion, Ohio
    Your original statement with the video implied that the sweep caused the elliptical span load. Sweep does not decrease the lift. He did not say that. He said, and showed, that the spanwise lift curve was shifted outwards towards the tips with a null in the center.

    And then he ignored the benefits of twist. With twist you can unload the tips and shift the lift back towards the center.

    His whole premise, however is based on the idea that elliptical is the most efficient, which is not necessarily so.

    Then there is my statement about the Scimitar shape wing, which was my reason for mentioning XFLR5. I tried that shape, and the lateral stability was HORRIBLE! With software like XFLR5 you can quickly separate the "gee that's neat!" and "well maybe" from the "yuch, that won't work".
     

Share This Page

arrow_white