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 29, 2019 #141

    Speedboat100

    Speedboat100

    Speedboat100

    Well-Known Member

    Joined:
    Nov 8, 2018
    Messages:
    581
    Likes Received:
    42
    Location:
    Europe

    Betz was right about propellers...please read the paper.
     
    Last edited: Jul 29, 2019
  2. Jul 30, 2019 #142

    Victor Bravo

    Victor Bravo

    Victor Bravo

    Well-Known Member

    Joined:
    Jul 30, 2014
    Messages:
    5,901
    Likes Received:
    4,728
    Location:
    KWHP, Los Angeles CA, USA
    Red, I believe you might be in a good position to address some of the questions raised earlier in this thread, pertaining to whether Al's Prandtl twist is only valid for one Cl, or one fight condition? Knowing Al I would bet that he considered this during his research, but I think you're closer to being able to verify that factually than myself and most of the others here. I hope to see you in Tehachapi,

    Bill / VB
     
  3. Jul 30, 2019 #143

    Richard Schubert

    Richard Schubert

    Richard Schubert

    Well-Known Member

    Joined:
    Feb 5, 2009
    Messages:
    150
    Likes Received:
    41
    Location:
    Pittsburgh, PA
    To piggyback on this question a little, maybe the problem should be attacked from the other direction. What kind of configuration and mission profile would result in the least amount of Cl change during flight?
     
  4. Jul 30, 2019 #144

    pictsidhe

    pictsidhe

    pictsidhe

    Well-Known Member

    Joined:
    Jul 15, 2014
    Messages:
    6,476
    Likes Received:
    1,678
    Location:
    North Carolina
    Flying really, really high.
     
  5. Jul 30, 2019 #145

    Richard Schubert

    Richard Schubert

    Richard Schubert

    Well-Known Member

    Joined:
    Feb 5, 2009
    Messages:
    150
    Likes Received:
    41
    Location:
    Pittsburgh, PA
    Or maybe really, really slow, like, you know, in a Cub.
     
  6. Jul 30, 2019 #146

    pictsidhe

    pictsidhe

    pictsidhe

    Well-Known Member

    Joined:
    Jul 15, 2014
    Messages:
    6,476
    Likes Received:
    1,678
    Location:
    North Carolina
    But that's for Cubs!
     
  7. Jul 30, 2019 #147

    Aerowerx

    Aerowerx

    Aerowerx

    Well-Known Member

    Joined:
    Dec 1, 2011
    Messages:
    4,807
    Likes Received:
    1,285
    Location:
    Marion, Ohio
    Do you mean Coefficient of lift (lower case letters) or Coefficient of Lift (upper case letters)????

    Coefficient of lift (lower case) depends only on the AoA at each wing station, and the airfoil used.

    Coefficient of Lift (upper case) depends on the gross weight of the aircraft and the wing area.
     
  8. Jul 30, 2019 #148

    Richard Schubert

    Richard Schubert

    Richard Schubert

    Well-Known Member

    Joined:
    Feb 5, 2009
    Messages:
    150
    Likes Received:
    41
    Location:
    Pittsburgh, PA
    To clarify, in the context of the discussion, if there is a large penalty for the off design condition, what kinds of configurations and missions could this be practically applied to.
     
  9. Jul 31, 2019 #149

    Aerowerx

    Aerowerx

    Aerowerx

    Well-Known Member

    Joined:
    Dec 1, 2011
    Messages:
    4,807
    Likes Received:
    1,285
    Location:
    Marion, Ohio
    Not sure I have a good answer for that, except for a touring/sight seeing/cross country mission you would be spending 90% of your time in cruise.

    Also, in the book "Tailless Aircraft" they give the example of a sailplane. Low speed/high Cl when in thermals, and high speed/low Cl between thermals.

    If any of you are REALLY interested in flying wings, buy, borrow, or steal a copy of Nickel's "Tailless Aircraft in Theory and Practice". It covers many of these topics. Although they treat elliptical as the ideal, IMHO the same arguments could be applied to the Prandtl-D bell shape.
     
  10. Jul 31, 2019 #150

    pictsidhe

    pictsidhe

    pictsidhe

    Well-Known Member

    Joined:
    Jul 15, 2014
    Messages:
    6,476
    Likes Received:
    1,678
    Location:
    North Carolina
    Well, you either work out how to use a point design, or work out how to minimise the penalty.
    For a long distance mile eater, flying really high keeps the Cl high and increases ground speed. The bad is that you need a engine that can put out enough power while breathing a partial vacuum. After that, the Armstrong limit gets in the way. A lot of additional weight is needed to safely get past that one...
     

Share This Page

arrow_white