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Lift Distibution Prediction

Posted By:
Ben Lescot
Homebuilder or Craftsman
3
Posts
0
#1 Posted: 8/17/2010 08:42:54

Hi all,

 
Does somebody know a software able to calculate a spanwise lift distribution ??? It would be great help for my preliminary design. Idealy, the software would be able to take several nacelles into account. Flying boat.JPG

Thanks,
 
 Ben




Curt Gridley
1
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0
#2 Posted: 8/19/2010 21:59:53

You might look at 3DFoil from Hanley Innovations:  http://www.hanleyinnovations.com/3dfoil.html

Or LinAir Pro from Desktop Aero:  http://www.desktop.aero/linair.php

Here's a link to the manual:  http://www.desktop.aero/manuals/LinAir_4_Manual.pdf.

I think each of these programs probably costs several hundred dollars though.

Regards,

Curt



John Johnson
Homebuilder or Craftsman
14
Posts
2
#3 Posted: 8/20/2010 02:06:20

For your preliminary evaluation just plot the span horizontally and the total chord vertically.   This will give you a curve of the area distribution of the planform which if very close to the lift distribution if there are no holes in the planform  Holes and sharp discontinuities in the outline cause depressions in the lift in the local neighborhood.   Then, when you figure out how the lift is distributed you twist the wing a bit back and forth along the span increasing or decreasing the lift in a given portion of the span until the total lift distribution curve approximates  a half of an ellipse along the span.

Back in the thirties they knew that the eliptical lift distribution was best but the only way they knew to ensure they got it was to make the shape of the wing eliptical.  Note the Spitfire for example.  Nowadays, we take what we have and twist it until it comes out as close to eliptical as we can get.  That probably works better than actually making the wing eliptical since the holes around the flaps and ailerons messed up the nice eliptical distribution anyway.



Keith Norton
Homebuilder or CraftsmanAirVenture Volunteer
14
Posts
1
#4 Posted: 8/24/2010 19:39:39

For a preliminary design you could try the aircraft designer tool in X-Plane. It uses the airfoil data to model how the aircraft will behave in flight. As an added bonus, you can even test fly it in the simulator!



Gerhard Koenig
Homebuilder or Craftsman
1
Post
1
#5 Posted: 9/1/2010 03:38:37

Maybe XFLR5 could be of good help for you.  It is freeware.

http://xflr5.sourceforge.net/xflr5.htm

XFLR5 is an analysis tool for airfoils, wings and planes operating at low Reynolds Numbers. It includes:

  1. XFoil's Direct and Inverse analysis capabilities
  2. Wing design and analysis capabilities based on the Lifiting Line Theory, on Vortex Lattice Method, and on 3D Panel Methods.

 



#6 Posted: 9/7/2010 14:15:37

You may search the internet for John Hazel's Liftroll Excel spreadsheet, which is a great tool!

Thomas