Nurflugelphobia

Discussion in 'Hangar Flying' started by Aerowerx, Jul 20, 2019.

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  1. Jul 21, 2019 #21

    Aerowerx

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  2. Jul 21, 2019 #22

    Aerowerx

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    I wondered when you would jump in here, Norm.

    Good point about moveable tail. Didn't think of that viewpoint, which reinforces the concept of it being a control surface!
     
  3. Jul 21, 2019 #23

    Aerowerx

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    The two terms for stability are Longitudinal and Lateral.

    Which do you mean? Lateral, which is side-to-side?
     
  4. Jul 21, 2019 #24

    Speedboat100

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    But it has very little sweep...so it might be better than swept pure nurflugel:
     
  5. Jul 21, 2019 #25

    Aerowerx

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    Like most things, "it depends". This is not a fair comparison anyway. A transport aircraft needs a fuselage to carry things, and pretty much needs a tail.

    And a certain amount of sweep actually helps on a flying wing, but you can also have too much sweep. The optimum seems to be somewhere around 20-30 degrees.

    Also, keep in mind that a decent flying wing will have a higher static margin than seen in typical tailled aircraft. As much as 20% in some cases. That is where many people get in trouble. They try moving the CG back to get that "magical" 8-10%, then wonder why they end up looking at the grass from underneath. A high static margin on a flying wing will virtually eliminate the stall-spin, or flip-backwards-then-tumble, problem (not my idea---it is in Nickel's book).
     
  6. Jul 21, 2019 #26

    henryk

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    "it is in Nickel's book"=

    =the only BKB1-A is tumbleresist ! (pp. circa 200...)
     
  7. Jul 22, 2019 #27

    mcrae0104

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    Thanks for pointing me straight, Norman. (I wouldn't want to be accused of being a bell-shaped denier.)
     
  8. Jul 22, 2019 #28

    BJC

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    How is that applied to an all-flying vertical surface or to stabilators?


    BJC
     
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  9. Jul 22, 2019 #29

    mcrae0104

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    All-flying control surfaces or otherwise, presumably this would account for the difference between "stick fixed" and "stick free" NPs.
     
  10. Jul 22, 2019 #30

    Aerowerx

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    The area still remains fixed in your examples, even if the surface is moving.

    Actually, a confusion in terminology I think. What Norm meant by "fixed" is a constant area, not "unmovable". A bird's tail does not have a constant area, but changes with flight mode.

    Norm, please correct me if that is not what you meant.
     
  11. Jul 22, 2019 #31

    Norman

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    Actually I did mean "fixed" in the sense of a fixed fin although said fin can be adjustable (such as with a jack screw) as long as it's not free to flop around in the airstream. A stabilator must be aerodynamically balanced on an axis such that a pitch excursion will produce a normal force without much moment around that axis. Theoretically, if balanced properly, a stabilator will not flop around freely in the airstream so it can provide both stability and control.
     
    Last edited: Jul 23, 2019
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  12. Jul 22, 2019 #32

    Norman

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    Yep.
     
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  13. Jul 22, 2019 #33

    Norman

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    Blasphemer!:D
     
    Last edited: Jul 22, 2019
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  14. Jul 22, 2019 #34

    Norman

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    And directional stability.

    The vertical fin of a conventional airplane produces a skid/yaw moment ie plane skids left=tail swings the nose left. Swept wings also produce a skid/yaw moment due to the differential drag of the unequally swept wings when the plane is in a skid or crosswind. The nonlinear twist described in Al Bowers' paper enhances the skid/yaw moment due to sweep by tilting the lift vector near the tips forward.
     
    Last edited: Jul 23, 2019
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  15. Jul 22, 2019 #35

    Aerowerx

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    Don't they also need an antiservo tab, or the pilots will find it rather disconcerting?
     
  16. Jul 22, 2019 #36

    Norman

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    An antiservo tab is an aerodynamic balance. I've seen drawings of stabilators without antiservo tabs but not too many examples of actual hardware without them.
     
  17. Jul 23, 2019 #37

    pictsidhe

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    I'm torn between heretic and infidel.
     
  18. Jul 23, 2019 #38

    Aerowerx

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    I wasn't considering the conceptual lifting body designs, which are not yet viable.

    Am I forgiven, or do I have to walk on my knees to Reimar Horten's grave?:)
     
  19. Jul 23, 2019 #39

    pictsidhe

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    Not yet viable? Stop digging that grave hole! I think not yet extant is more accurate. Wasn't there a funky faceted thing buzzing around some years back? It looked pretty roomy to me.
    I 'fess up to my own design dabbling being predicted to fly too much like a turkey for my liking, that doesn't mean that they all will! I know that there are smarter people than me out there working on this.
     
  20. Jul 23, 2019 #40

    Speedboat100

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    30 deg sweep increases the drag by 20%. Funny that Al says rudder causes 20% drag increase on his videos.
     

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