Just Curious: Canard Biplane Pusher Stall Behaviour

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by Aerowerx, Aug 29, 2012.

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  1. Sep 1, 2012 #21

    Aircar

    Aircar

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    The all flying canard is indeed a different case --see the flying flea thread for more detail (and it is a bit of a misnomer to say that the canard stalls even with a 'normal' canard --it certainly must suffer SEPARATION and a reduction of lift --and further complexities to do with relative lift slope curves and downwash on the rear wing etc --also discussed elsewhere ;BUT IF the whole canard were to stall the nose would indeed drop,and CONTINUE dropping --as the aircraft rotates the angle of attack will increase and further decrease the lift of the canard (the only thing holding the nose up --hence you get a self energizing bunt such as the Curtiss Ascender encountered. It is the FLAP on the canard that 'stalls' and the increase in angle of attack acting on the CANARD then raises the nose --it must have enough margin for this to be true (and an airfoil that allows it ) The slotted flap is easiest to arrange for such non linear behaviour but the plain flap can also work on aft loaded airfoils (TE Stall progression) --without any flap on the canard the airfoil itself has to be carefully chosen -you do not want a leading edge type stall -eg 23 series airfoils --one canard two seat ultralight even had a leading slat fitted (American Eagle comes to mind -Chuck Yeager used to endorse it on ads in kitplane -also covered in another thread on HBA )
     
  2. Sep 1, 2012 #22

    SVSUSteve

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    You mean besides it being kind of ugly?
     
  3. Sep 5, 2012 #23

    1Bad88

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    Making me rethink my decision here...
     
  4. Sep 6, 2012 #24

    flyoz

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    What about the Colab wing concept applied to the Onyx ( flying flea )
    It seems that placing the canard quite a bit higher has some interesting possibilities
    It can actually reduce the drag if its done right
    The downwash can help reduce the separation on the main wing
    The downwash from the canard ( in climb etc only ) means the main wing operates at a lower angle of attack
    From flight reports the Onyx CP150 would not stall and the main wing retained aileron effectiveness - it simply "mushed" down
    Flyoz
     

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  5. Sep 6, 2012 #25

    Aircar

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    The thing is that with an all flying canard the angle of attack of the canard is divorced from the rest of the aircraft --it can unstall just as easily regardless of the rest of the aircraft's motion . The thumbnail sketches are not valid explanations unfortunately and mistake laminar flow for no gross separation and confuse the working volume of fluid in the lower one (control volume ) --the stagnation point for the lower airfoil and the gap at the TEs are incorrectly shown and the AoAs shown are unstable . See Nenadovich biplane for more correct interaction information and the Flying Flea sites.
     

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