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. Aug 29, 2012 #1

    Aerowerx

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    What would be the stall characteristics of such a plane?

    With negative stagger on the wings, I would guess the canard would stall first, and then the lower wing?
     
  2. Aug 29, 2012 #2

    Kristoffon

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    The canard must always stall first or the airplane will enter an extremely dangerous pitch-up state which it might not be able to recover from, and crash. That is a fundamental design parameter of any canard-type airplane.

    Then, the other wing(s) should never stall because the canard stalling pitches the nose down and automatically reduces angle of attack.
     
  3. Aug 29, 2012 #3

    Jan Carlsson

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    That goes for most all airplanes, that forward wing stall first.
    A canard Biplane pusher? was that not invented 110 years ago? I am sure I seen it somewhere, not sure I am Right about the name.
     
  4. Aug 29, 2012 #4

    StarJar

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    If your talking about a staggered biplane, the designer always puts the forward wing at a higher angle of incidence, to insure the qualities stated by the posts above.
     
  5. Aug 30, 2012 #5

    Aerowerx

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  6. Aug 30, 2012 #6

    Norman

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    Hopefully the plane will pitch down after the canard stalls. But, if it doesn't, then the next most forward surface should stall.
     
  7. Aug 30, 2012 #7

    Jan Carlsson

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    Sorry could not resist,

    But loking at the sucessfull canards they have the canard and wing inline lengthwise, from the canard the downwash and vortex hit the wing(s) making things interesting,
    the SAAB Viggen use the vortex from the canard at high alphas, but they are delta wings and heavy/fast planes.
     
  8. Aug 30, 2012 #8

    Aircar

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    The BURD Man Powered aircraft was a canard biplane as well but can't think of too many others - I guess you are after saving some wing weight or is it to get more area and LSA stall speed or ultralight or...?

    The specs for the IBIS say it has no twist on the main wing which could result in main wing tip stall from the canard's upwash (outboard of it's tips ) on the rear wing outer end together with downwash on the centre section (which should stall first in any case with an untapered wing ) Compare the Gyroflug Speed canard wing for it's section and angle changes or EZs .

    If Synergy finishes up with a canard (three surface) it will conform basically to your description (negative stagger biplane etc ) -- the rear surface can be continued to join on the centreline and give some structural benefit and straddle the prop as was done on some others designs (the influence of the pusher prop on the biplane would be interesting as well --the inflow mainly . Without knowing the sweep and fore aft positions of the wings it is a bit hard to predict too much -- and 'biplane' is a fairly broad term nowadays as well.
     
  9. Aug 30, 2012 #9

    Norman

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  10. Aug 30, 2012 #10

    Aerowerx

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    Thanks, Norm! Just the type of info I was hoping to get.
     
  11. Aug 30, 2012 #11

    Aerowerx

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    Interesting. A lot like the boxer wing with canard that I was picturing in my mind.



    And have you considered this factor?

    It is conceivable that lady fliers will find Mr. Boland's solution especially elegant, owing to the difficulties engendered by feminine attire. Without the need for rudder control, perhaps we will see a resurgence of skirts in the cockpit, despite Miss Harriet Quimby's comments to the contrary.​
     
  12. Aug 30, 2012 #12

    SVSUSteve

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    Which is why most people (including Raymer and Peter Garrison in some of their publications) suggest that canards should be designed with extreme caution, if at all, by anyone without a full education in aerodynamics.

    I am considering a canard design as a second design after the LSA build is complete. It will not make it past the drawing board without being reviewed by several competent aerodynamicists.
     
  13. Aug 30, 2012 #13

    Jan Carlsson

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    The down side with canards is that the main wings full lift CL can not be used, meaning larger wing or higher stall speed then for a conventiional plane.
    Biplane is good, but ad a foot of span on each side and you have a better monoplane then the biplane was.
     
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  14. Aug 31, 2012 #14

    bmcj

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    Just brainstorming... a canard could conceivably achieve Cl-max from the wing if the wing's Cl-alpha curve has a long flat region of Cl-max. That would allow you to set the canard stall somewhere in the middle of the wing's flat curve area with a little safety margin built in. With a biplane, perhaps setting the wings at different angles of incidence might simulate a flat curve for the overall configuration.

    Now to carry this further, if you have a biplane with a large wing and a small wing, and the large wing is set forward of the small wing, you could set the incidences such that the canard could drive the large wing to max lift for slow speed benefit. When the large wing stalls, the small wing will still be flying and the nose will drop. This could unstall the large wing, or the nose drop might stall the canard due to a relative upward movement of the air. Either way, as long as the canard stalls before the small rearward wing, you should have a stable ship that can obtain Cl-max out of the largest flying surface. Of course, it may have an exaggerated stall-bucking tendency, but I think you could minimize that with careful design and learned pilot technique.

    Bruce :)
     
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  15. Aug 31, 2012 #15

    Aerowerx

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    YES!!:ban: Exactly what I was wondering, but didn't know how to put in words (not being an aero engineer)! And the type of answer I was looking for, too.
     
  16. Aug 31, 2012 #16

    Aerowerx

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    Somewhere around here I have a couple of papers that discuss the 'optimum' placement of the canard. Since my stack of papers is almost two feet tall now, and it is late and I am tired, I don't feel like digging them out right now.

    But IIRC, the 'best' location for the canard is 1/2 MAC above the wing and 1.5 MAC ahead of the wing. Done right and the vortex off the canard actually helps the main wing.

    Not sure how this would apply to a biplane, though.
     
  17. Aug 31, 2012 #17

    Richard Schubert

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    Well Duh, Its called a Piaggio Avanti. ;)
     
  18. Aug 31, 2012 #18

    Aircar

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    Except that the Avanti is not a biplane ( I think the description refers to an unequal biplane or sesquiplane --the Transavia Airtruck was an example of such a thing along with some of the Bellancas (truncated lower wing sort of sesqui--) and some examples of WW 1 era and other regular aft tail biplanes --there was a pusher/canard/unequal biplane called DeBruyne or something close that crashed on it's first flight but that doesn't neccesarily have anything to do with the layout . It is on the web somewhere I would think ...let's see...
     
  19. Aug 31, 2012 #19

    Aircar

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    It was the De bruyere C1 The De Bruyere C1. | Civilian Military Intelligence Group -- there will be other pictures post crash (belly up) -some of the photos hide the canard behind the wing . It was clearly a very advanced design especially for 1917 --Aeroplane Monthly covered it in August 1985 and speculated that the rotating wing tip ailerons might have caused the accident .
     
  20. Aug 31, 2012 #20

    flyoz

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    What about Claude Piel's Onyx ?
    The canard is all flying ( from Flying Flea ) but the stall system is very different to Rutan's Varieze etc
    I have tried to find some info describing how essentially a much larger ratio canard stalls before the main wing on the Onyx without much success
    Especially a fully flying canard - any ideas ?
    Here is a link Galerie Photos Avions Piel - CP150 Onyx, Onyx Biplace et Hydravion.
    Flyoz
     

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