Airfoil program

Stuka Stunt Main Forum · 10 of 10 known posts recovered

SteveB · Aug 02, 2000 11:47 AM

To all who might be interested. I've just started learning AutoLISP programming for AutoCAD (starting yesterday). Well, the first LISP program I wrote was to automatically draw an airfoil.

All that you do is pick a starting point, tell it what the chord is, where the highpoint is located, total thickness of airfoil, T.E. thickness, and it does the rest. I even have it set up for semi-symmetrical airfoils, such as the type used by Al Rabe. It can handle virtually any size chord thickness (within reason). An interesting side note for it is, the front of the airfoil (leading edge to highpoint) is a true ellipse.

For a limited time, I will send it to interested parties for testing. Just load the file in AutoCAD (which you must have in order to use this) as you would any other LISP file and type in "airfoil". The program will prompt you for the require information and draw all that is needed.

Once I get a better handle on LISP programming, I intend to do a much more complex file, where it'll draw the airfoil, wingplan, rib locations, loft all need airfoils, mark the moments (nose-to-L.E. and T.E.-to-hingeline (or Hingeline-to-hingeline for flapped models) and even do basic outlines for tail surfaces and fuselage. I know, it's rather ambitious, but I think I can do it, and I'm sure it can help speed the design process for many.

Let me know what y'all think about it. Email or just respond to this message.

Tight lines to all,

Steve Berry
AMA 628018
-------------------------------------
Texas - The "Heart" of Modern Stunt!!

captcurt · Aug 02, 2000 01:39 PM

#1 source

>Steve wrote, in part:
>
>All that you do is pick
>a starting point, tell it
>what the chord is, where
>the highpoint is located, total
>thickness of airfoil, T.E. thickness,
>and it does the rest.
>

This sounds interesting Steve but does the program actually plot airfoil offsets from a given airfoil series or is it simply joining your elliptical LE, max thk, and TE points with a smooth curve?

AS I'm sure you know, NASA (NACA)airfoil series are well defined with thickness offsets described at various points (percent) of the chord behind the LE. WHile these may appear to be simple curves, they are, in many cases, not.

Curt

SteveB · Aug 02, 2000 03:59 PM

#2 source

It simply joins the points. I don't have access to any of the NASA airfoil numbers, and it would be a headache to try and put all of them in the program. But, I have used my method for generating airfoils for several years with good success. They may not be exact, but then these are just "toy airplanes" we're dealing with, not high-speed, high-altitude bombers.

Tight lines to all,

Steve Berry
AMA 628018
-------------------------------------
Texas - The "Heart" of Modern Stunt!!

Julianw · Aug 03, 2000 09:21 AM

#3 source

If you are interested in this sort of modelling (i.e. CADD) you may want to take a look at Autodesk Mechanical Desktop - It allows you to model parts (such as ribs) parametrically so tht you can input whatever dimensions you want and have the drawing re-drawn accordingly. It also allows you to model assemblies (such as a wing) from the part drawings. it is much more powerful than using autolisp routines; however, it requires a large time investment to learn its use and, unless you can get it through your work its cost is FAR beyond what most individuals would want or be able to pay.

JW.

Forumhost · Aug 03, 2000 09:37 AM

#4 source

LAST EDITED ON Aug-03-00 AT 01:11 PM (EST)

And Janet Reno said Microsoft was charging too much for its Windows operating system! Shame, Janet, Shame!

Leonard Neumann
Forum Host

Randy · Oct 06, 2000 07:47 PM

#7 source

Well, 2 things. First, I don't much care what Janet Reno says about Microsoft. I use Linux and it was "FREE".

Second, the window manager I use is written in Lisp. Shame the airfoil program needs AutoCAD.

I been using Larry's StuntRib program (written in DOS, but I have an emulator that works pretty well).

Randy

SteveB · Aug 04, 2000 04:49 PM

#5 source

Some tweaking has been done, and it will now draw the flaps (side-view), tapered from whatever thickness the T.E. is to 1/8" final thickness. It will also mark the nose and tail moments. This weekend I plan on adding to it so that it'll draw the side-view for the stab/elev. and a box for the fuselage (likely 4" tall x however long it needs to be). Again, everything is pretty much a user-prompt for needed info. I'll keep everyone updated as to my progress.

Tight lines to all,

Steve Berry
AMA 628018
-------------------------------------
Texas - The "Heart" of Modern Stunt!!

SteveD · Oct 06, 2000 06:59 PM

#6 source

Will it work with a shareware program like intili CAD2000? if all else failes---accelerate!

geoffgg · Oct 07, 2000 11:34 PM

#8 source

There is a 457pp manual for IntelliCAD downloadable (10MB PDF file) from somewhere on the site that gives instructions on how to make LISP stuff work with IntelliCAD. I've not yet tried it so I do not know how it works but the manual gives an explanation.

Cheers, Geoff

Howard Rush · Oct 09, 2000 01:52 AM

#9 source

Airfoils:
http://amber.aae.uiuc.edu/~m-selig/ads.html

The NACA 4-digit foils come from a polynomial, sorta, so you can draw continuous curves using it. You can also fiddle with the coefficients that generate it to match arbitrary symmetrical airfoils pretty accurately.