Build your own HO229 WW2 German Jet Fighter!!

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

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  1. Jul 18, 2019 #21

    Victor Bravo

    Victor Bravo

    Victor Bravo

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    I agree that he has certainly made it his lifetime obsession. But unlike some people's crazy or fantasy obsessions, Al Bowers is absolutely not putting opinion before science, or his hoped-for outcomes above fact. There are far too many highly educated people who have watched his progress... if a high level guy like Phil Barnes, and a whole room ful of experienced aerospace people as well... thought that Al was not being accurate, they would be in a position to call it into question.

    As far as his lift distribution and wing twise implications, Al's work is also somewhat supported by work from Irv Culver (The "Culver twist" for flying wings),a nd Jack Norris' propeller twist distribution research, all of which is based upon a lot of early mathematical research by people like Prandtl who have no stake in this argument (being dead)

    A pure flying wing is a noble goal, and perhaps the theoretical beauty of that is what motivates Al and many many other nurflugel people. But Al himself answered a direct question I asked... "Yeah, this would work just as well on a Cub".
     
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  2. Jul 18, 2019 #22

    Speedboat100

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    How can he even consider that in a Cup ?
     

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  3. Jul 18, 2019 #23

    Victor Bravo

    Victor Bravo

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    He meant it would work on a Piper Cub
     
  4. Jul 19, 2019 #24

    Kyle Boatright

    Kyle Boatright

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    IMO, this is the challenge for those obsessed with flying wings and other specific planforms. The idea is to build an airplane that performs its "job" best, not to design the best flying wing, or flying doughnut, triplane pusher, or whatever.

    Obsession over a particular planform leads down lots of rabbit holes which probably don't hold a commercially viable rabbit.
     
  5. Jul 19, 2019 #25

    Red Jensen

    Red Jensen

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    The real goal of Al's research is not necessarily an obsession with the flying wing, its an alternate spanload to the ubiquitous "elliptical is the only way" mind set, and to prove Prandtl's 1933 spanload equations. The flying wing was chosen because it is naturally suited to the research. No fuselage, tail etc. to clutter the data.
     
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  6. Jul 19, 2019 #26

    Red Jensen

    Red Jensen

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    I tried to quote SpeedBoat100's post with the pic above but it won't let me. Anyway, that one is not the Mars wing, its P-2, the second of the 12.5' span models. The current Mars aircraft are 24" span and headed smaller.
     
  7. Jul 19, 2019 #27

    Speedboat100

    Speedboat100

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    Yes I agree...and a wingless aircraft with no fuselage needs a lot of rudder area to be able to operate in all conditions.
     
  8. Jul 19, 2019 #28

    Red Jensen

    Red Jensen

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    (Juke?) Actually, no it doesn't. Like the B-2, drag devices can be placed on the wings for direct yaw control.
     
  9. Jul 19, 2019 #29

    Aerowerx

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    Why do you call it an "obsession"?? I object to the use of that term.

    From this online dictionary:
    This implies that it is mentally unhealthy to want to design and build flying wings.

    "Compulsive preoccupation" implies that the person has no control over it, to the exclusion of all else.

    And I don't see how a flying wing is an "unreasonable idea".
     
  10. Jul 19, 2019 #30

    pictsidhe

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    I have done some fairly nasty maths on alternative lift distributions and have a very messy spreadsheet to prove it. The big downside to these distributions is that the optimum twist changes with CL. I came up with a planform trick that works up to about 1/2 span, but outboard of that, the twist needs to change or things go very awry. Either with wing warping or big flaps of some sort. The further that a distibution deviates from elliptical, the more the twist needs to change, or the higher the penalty for not doing so. I do not think that this is insoluble, but it is a tough nut to crack.
    It is a practical problem, not theoretical. It has me stumped. Birds morph their wings, we don't, yet...
     
  11. Jul 19, 2019 #31

    Aerowerx

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    I've just started reading the chapter in "tailless Aircraft" (you do have a copy,don't you?) on optimizing. I suggest reading it if you haven't already. There is a parameter they use that indicates how far a real wing will deviate from the "ideal" elliptical. It also suggests extending the cord in the area of the control surface.

    It even mentions that a control surface essentially changes the twist (they use the term "washout").
     
  12. Jul 19, 2019 #32

    Speedboat100

    Speedboat100

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    Excluding the B-2 of course like previously mentioned. I think we are talking about ultralites and homebuilts here aren't we ?
     
  13. Jul 19, 2019 #33

    Victor Bravo

    Victor Bravo

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    Many of you here on HBA have education levels that dwarf mine to an embarrassing level. PLEASE bring these questions and facts to ESA and confront Al with them. I would like to hear if and what the answers to the questions are.
     
  14. Jul 19, 2019 #34

    Speedboat100

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    I would like to ask Al...first of all..if rudders cause 20% of the drag in an aeroplane ( as he claims )..how come the drag devices ( split ailerons ?) don't cause drag ? I mean..even the normal ailerons cause a terrific drag. Maybe he has solved this.
     
  15. Jul 19, 2019 #35

    Red Jensen

    Red Jensen

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    Juke,

    The rudders alone don't cause all that drag, the entire tail does, horizontal, elevator, fin and rudder. In a P spanloaded aircraft, the upward deflected elevon actually has a forward lift vector (thrust) like a winglet that causes the proverse yaw. For direct yaw control (like a crosswind landing) you would need split elevons which do indeed cause drag, otherwise its not needed. The gliders are all 2 axis control only.
     
  16. Jul 19, 2019 #36

    Red Jensen

    Red Jensen

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    Oh you mean like this?

     
  17. Jul 20, 2019 #37

    Aerowerx

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    Considering the title of this thread, no, not specifically.

    If I had meant this to be a serious discussion, I would have put it in the New Technology & Design forum.

    All of this has been discussed many times before. It seems like it goes quiet for a while, and then all someone has to do is mention the word "tailless", and here we are again!
     
  18. Jul 20, 2019 #38

    pictsidhe

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    Yes, I have a copy. It's a good primer. I went a lot further with the maths than the book does. If you want your tailless aircraft to work over the full CL range, you need to variable twist or things get very, very out of whack away from your design point. For instance, lots of drag at cruise if you wash out the tips enough for a safe stall. Have you got to the bit where Nickel says that elliptical distributions are the best way forward?

    VB, I have no illusions of being able to teach Al anything, but I'd be very interested in hearing how he may have overcome some of the obstacles I have come up against. specifically, getting it to work fairly well over the whole CL range without delving into the wonders of wing warping.
     
    Last edited: Jul 20, 2019
  19. Jul 20, 2019 #39

    Speedboat100

    Speedboat100

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    That is a glider again.

    Here is a flying wing with rudders...a model...and he complains that rudders were too small:
     
    Last edited: Jul 20, 2019
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  20. Jul 20, 2019 #40

    Hot Wings

    Hot Wings

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    So he is going to be there this year? I'd developed the impression that after retiring that he would be abandoning further development of his ideas, leaving that up to his students and the rest of us? If he is going to be there this year, and I actually get to attend, it will remove some of the sting of not being able to attend his forum last year.
     

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