Tandem wing design discussion

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by cluttonfred, Jul 26, 2010.

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  1. Jul 30, 2010 #21

    cluttonfred

    cluttonfred

    cluttonfred

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    Going back to the little Mauboussin Type 40 Hemiptère for a moment...

    The wing arrangement diagram (below) from the 1936 fight article Flight article (complete article in first post in this thread) appears to show both a reflexed, probably autostable, airfoil on the front wing and a symmetrical airfoil on the rear wing. This is a very conservative approach which provides maximum pitch stability at all angles of attack, but both the reflexed and symmetrical airfoils reduce efficiency. Does anyone know of a way to get the same kind of stability but without resorting to these degraded airfoils?

    Thanks and regards,

    Matthew
     

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  2. Jul 30, 2010 #22

    cluttonfred

    cluttonfred

    cluttonfred

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    And on a related note...it occurs to me than on a low-speed, low-wing-loading two-seater to fit European microlight rules (450 kg gross weight, 65 kph landing speed) it might make sense to use rear control surfaces as elevons and eliminate control surfaces from the front wing altogether. That should eliminate both some drag and some weight.
     
  3. Aug 4, 2010 #23

    WonderousMountain

    WonderousMountain

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    Hello again,

    In my search for a lighter simpler cheaper design I managed to go both forward and backwards simultaneously. Altering my latest notes-and infusing my first wish for a multi-plane.

    The result is a sleek, single seat, lightweight, maneuverable (set of notes....). The flying heavier than air contraption would have three sets of (8-10' wide, 16-24" cord) wings of identical Hershey bar construction starting from the nose, highest point on the fuselage (above head) and a point nearing the tail to be disclosed at a later date, and coming together in a tip plate. Engines undecided, but assume underpowered.

    The rearmost wing would have flaps controlled by a stick capable of independent up or down movement. The front wings would have a separate "emergency" control surfaces that could be employed in the event of rear failure. Tail will be an exceedingly large fin, operated by standard foot levers.

    Aside from all the horrid ways such a craft could lose balance/lift and fall out of the sky, are there any common weak points joined/multi-wing builders fail to account for? Mostly concerned with landings.


    Wonderous Mountain
     
  4. Aug 4, 2010 #24

    TFF

    TFF

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  5. Aug 25, 2010 #25

    WonderousMountain

    WonderousMountain

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    Just realized the control scheme will be a nightmare and that's assuming wing interactions can be kept functional for standard and emergancy flight manuvers. Also the structural efficiency doesn't seem better than standard configurations and the tail arrangement is puzzeling at best. If I can even come up with a workable design, modification will be nearly impossible, and costs will most likely exceed my previous estimates to say nothing of build time.

    Sounds like my kinda plan.

    Crosseyed,
    Wonderous Mountain
     
  6. Aug 25, 2010 #26

    Rienk

    Rienk

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    Here's a concept that I wouldn't mind playing with when I get the time...
     

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  7. Dec 24, 2010 #27

    HumanPoweredDesigner

    HumanPoweredDesigner

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    Does anyone know how to calculate the angle of incidence of air hitting the rear wing? By angle of incidence, I mean if the rear wing is directly behind the front wing in level flight and the angle is measured relative to the line connecting the wings. I'm not building a tandem and in no way implying that is how one should be built. I'm just defining the angle I'm after. I need to know how to do such calculations given the coefficient of lift of the front wing, the span of the front wing (even an infinite wing answer will help), cord of the front wing, and separation distance; preferably at low speed, high coefficient of lift, small cord, and a separation distance near 1.5 x the span, for two wings at the same height. I don't plan to build a tandem wing, or any airplane soon. I just need to know how to do this calculation and just thought the people who design tandem wings would probably know how to do that calculation so they can pitch the rear wing most optimally. I don't think momentum theory directly applies here or I'd use that.

    I read this thread, but most of the good sounding links are dead. I found a trigonometric equation in an aerodynamics book that looks similar to what I'm looking for, since it relates down draft speed to location relative to the wing, but I think it is referring to tip vorticies. It does not mention coefficient of lift, and only gives relative downdraft speeds based on two angles in the plane of the wing surface.

    I'll do some more searching and I really appreciate any info about this. Even some good google key words would be very helpful. Thank you.
     
    Last edited: Dec 24, 2010
  8. Dec 24, 2010 #28

    orion

    orion

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    Just calculate the downwash angle - that's all it is.
     
  9. Dec 31, 2010 #29

    yankeeclipper

    yankeeclipper

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    Not to be trivial, but, how would you take off with rear wing elevators/elevons?

    Can someone elaborate a little on "asymmetrical stalling"? Does this refer to the risk of stalling by over elevating, and then adding loss of roll control?
     

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