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  1. #176
    eddieC's Avatar
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    RE: do ailerons provide lift?

    As you can see from BMatthews post, you can still get lift at negative A0A. 

    I suspected as much, from playing with undercambered airfoils. 
    Fortunately, mankind has progressed since the Wright Flyer and its ilk. For more conventional, efficient airfoils, I believe my original statements still are true. My bad, thinking we were talking about present day technology. 
    I might not be very good, but I'm fun to watch!

  2. #177
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    RE: do ailerons provide lift?

    ORIGINAL: eddieC
    I suspected as much, from playing with undercambered airfoils.*
    Fortunately, mankind has progressed since the Wright Flyer and its ilk. For more conventional, efficient airfoils, I believe my original statements still are true. My bad, thinking we were talking about present day technology.*

    Positively cambered airfloils can produce lift at negative angles of attack, they don't necessarily have to be undercambered.
    Matt

  • #178
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    RE: do ailerons provide lift?

    There is no lift at zero or negative angles
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  • #179
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    RE: do ailerons provide lift?


    ORIGINAL: rmh

    There is no lift at zero or negative angles

    Didn't you see BMatthews curves?


    Unless you defined angle of attack to be reference to the zero lift line and not the chord line, you still have lift at negative AoA.

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  • #180
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    RE: do ailerons provide lift?

    Yes, I saw that - The definitions of zero lift line and the chord line - are the problem.
    You can NOT have lift if the effective AOA is zero or less
    The concept of a lifting surface is simple
    it is any shape which may develop unequal pressure- Typically higher pressures under the shape - lower pressures above
    How efficiently it does this is quite a different matter . The shape may be perfectly flat -and simply forced to hold an angle of attack
    OR it may be a flat sheet - curved and forced to move at a given angle of attack
    OR it may be a rather involved combination of curves
    IF you change the angle it is moving , such that pressure above and below are equal- THAT is a zero lift path draw that line -
    it is the zero lift line .
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  • #181
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    RE: do ailerons provide lift?

    Let me see if I understand.

    "When an airfoil is set to its zero lift AoA, it creates.....wait for it.....zero lift"


    I found this on the internets:

    As a wing moves through the air, the wing is inclined to the flight direction at some angle. The angle between the chord line and the flight direction is called the angle of attack and has a large effect on the lift generated by a wing.

    And from the same webpage

    Notice on this plot that at zero angle a small amount of lift is generated because of the airfoil shape. If the airfoil had been symmetric, the lift would be zero at zero angle of attack.
    Matt

  • #182
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    RE: do ailerons provide lift?

    oops almost forgot the website was


    www.nasa.gov
    Matt

  • #183
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    RE: do ailerons provide lift?

    Good ol NASA
    This is simply an exercize in logic
    If No lift is produced was by the moving airfoilthere was no effective angle of attack
    stated differently - -there was no effective pressure difference top to bottom
    - the wing must be held at some angle to acheive an effective AOA
    depending on the shape utilized the appearance of the effective AOA can be misleading . as soon as you throw in"chord line ", things get cloudy
    If your idea of the chord line is different than someone elses idea of chord line the AOA will be a different number.
    wings ar all about getting effective pressure difference - in the most efficient manner .
    How can we as poor model builders know when we have selected the optomized shape?
    it's tricky as once yo u change weight - speed and load and speed range- the best shape changes - as does the the necessary shape use to prevent the wing from twisting /bending.
    It's all a SWAG- and trying for some "perfect" shape is simply a make work project.
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  • #184
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    Lnewqban - "God will not look you over for medals, degrees or diplomas, but for scars. He has achieved success who has worked well, laughed often, and loved much." - Elbert Hubbard

  • #185
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    RE: do ailerons provide lift?

    paragraph 2 says it
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