Cruciform tail for 3-axis control?

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by cluttonfred, Sep 24, 2014.

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  1. Sep 28, 2014 #21

    highspeed

    highspeed

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    Recall that the early Rutan Vari-EZ's had differential elevons on the canard for pitch/roll control. Burt Rutan later added ailerons to the wing after early builders reported poor roll authority. A cruciform tail could work, but run the numbers to see what the control authority is.
     
  2. Sep 28, 2014 #22

    cluttonfred

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    Thanks, guys, I am still digging around for a simple mechanical solution. I suspect that for this to work I'll need the surface area of a full fourth surface, which likely means quite tall landing gear.

    In the keep it simple category, I also came up with the idea of using completely conventional elevons (plenty of mixer designs available there) and twin rudders but a biplane horizontal tail to get adequate roll authority. That might also come in handy in to get adequate stability in a short tailplane span and overall length for small trailers and hangars such as clearing the door width and interior length of a 20' ISO shipping container.
     
  3. Sep 28, 2014 #23

    Tiger Tim

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    How about going the other way? Could you get enough pitch and yaw authority with split flaperons to have a tail that only stabilizes? I think any of these things could be felt out well enough on X-plane to decide if it was worth continuing development.

    -Tim
     
  4. Sep 28, 2014 #24

    Sockmonkey

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    Many flying wing designs use them so yes.
     
  5. Sep 28, 2014 #25

    Tiger Tim

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    True, but I was thinking of also having a plug-in tail boom with stabilizing surfaces because plank-type flying wings weird me out. Would wing mounted elevators have enough authority to overcome the tail's influence?

    -Tim
     
  6. Sep 28, 2014 #26

    cluttonfred

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  7. Sep 30, 2014 #27

    Riggerrob

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  8. Oct 1, 2014 #28

    cluttonfred

    cluttonfred

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    I realize that this would be an extreme case with the short span main wing, but isn't that true with any rudder which is not vertically symmetrical?
     
  9. Oct 1, 2014 #29

    Sockmonkey

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    It creates roll force, but on such a short lever arm that it's more than countered by the much longer lever arms of the wing using ailerons and roll-stabilizing features like wing dihedral.
     
  10. Oct 1, 2014 #30

    BJC

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  11. Oct 1, 2014 #31

    cluttonfred

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  12. Oct 1, 2014 #32

    BJC

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    As I recall, it was being set up (Leo died before it was completed) to use ailerons as flaps both positive and negative, and he considered differential elevator operation to assist in roll. Don't know how the final version was configured.

    It used carbon fiber tubes for the fuselage.

    All this quite a long time ago.


    BJC
     

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