Is there a way to calculate the lift curve slope vs aspect ratio?

Discussion in 'Aircraft Design / Aerodynamics / New Technology' started by rtfm, Sep 26, 2018.

Help Support HomeBuiltAirplanes Forum by donating:

  1. Sep 26, 2018 #1

    rtfm

    rtfm

    rtfm

    Well-Known Member

    Joined:
    Jan 3, 2008
    Messages:
    3,155
    Likes Received:
    558
    Location:
    Brisbane, Australia
    Hi,
    I am trying to find a way to calculate the lift curve slope of a wing depending on its aspect ratio. Is there such a beast? Basically the slope value * some factor based on AR.

    Duncan
     
  2. Sep 26, 2018 #2

    lr27

    lr27

    lr27

    Well-Known Member

    Joined:
    Nov 3, 2007
    Messages:
    3,216
    Likes Received:
    463
    Ok. A tiny bit of algebra on a formula found in Hoerner* for "lift angle" gives:

    dCl/d alpha = 1/ (10 + (20/A))

    This is supposed to be a rough approximation for straight wings of at least moderate aspect ratio, and may still be a little different depending on planform shape. Units are degrees.

    *Fluid Dynamic Lift Don't know if you can still get it.
     
  3. Sep 26, 2018 #3

    lr27

    lr27

    lr27

    Well-Known Member

    Joined:
    Nov 3, 2007
    Messages:
    3,216
    Likes Received:
    463
    Was poking around the web about something else and found a reference to a way of calculating lift curve that's supposed to be in NACA TR-665. You can probably find that on NASA's technical report server or on the Magic NACA Archive. Appears to be more complicated.
     
  4. Sep 26, 2018 #4

    rtfm

    rtfm

    rtfm

    Well-Known Member

    Joined:
    Jan 3, 2008
    Messages:
    3,155
    Likes Received:
    558
    Location:
    Brisbane, Australia
    Thanks mate
     
  5. Sep 26, 2018 #5

    lr27

    lr27

    lr27

    Well-Known Member

    Joined:
    Nov 3, 2007
    Messages:
    3,216
    Likes Received:
    463
    BTW, I bet if it's for a Pou, it's more complicated.
     
  6. Sep 26, 2018 #6

    dwreck

    dwreck

    dwreck

    Active Member

    Joined:
    Jan 24, 2014
    Messages:
    32
    Likes Received:
    1
    Location:
    Abu Dhabi, UAE
    General Aviation Aircraft Design by Snorri Gudmundsson has a short section in Chapter 9 listing various methods for estimating wing lift-curve slope. Inbox me if you want screenshots.
     
  7. Sep 26, 2018 #7

    pictsidhe

    pictsidhe

    pictsidhe

    Well-Known Member

    Joined:
    Jul 15, 2014
    Messages:
    5,869
    Likes Received:
    1,488
    Location:
    North Carolina
    1/(pi*(1+(2/A)*(1/e)))
    where e is span efficiency. Angle in radians
     
  8. Sep 30, 2018 #8

    Pete Plumb

    Pete Plumb

    Pete Plumb

    Well-Known Member

    Joined:
    Oct 23, 2014
    Messages:
    175
    Likes Received:
    249
    Location:
    SHAFTER, CA
    The one I use is a simple old Department of Commerce formula: .0725 x 4 over 3+(6/ARe).
     

Share This Page

arrow_white