More on airfoils…

November 14, 2012 | Radio Controlled Airplanes | By: Mark VandeWettering

As I was staring at the cross sectional diagram of the Armin wing I constructed yesterday, I began to think about airfoil shapes in general. I knew from reading done years ago that there were standardized ways of describing airfoil shapes, but didn’t recall any details. I didn’t have a copy of Abbot’s Theory of Wing Sections, and I loaned Mark H. my copy of Simon’s Model Aircraft Aerodynamics, so I had to turn to Google and Wikipedia to sate my desire for knowledge.

A few minutes of searching uncovered this Wikipedia entry on NACA airfoils. It’s pretty helpful, and includes formulas for generating the airfoil profiles of a wide variety of standard wing shapes. I hacked together a quick python program to generate the profile coordinates for 4 digit NACA airfoils, and as soon as I verify the results, I’ll post the code here. It won’t be hard to use this to generate a PostScript/PDF file which you could then directly print to make templates.

A bit more searching revealed this repository of Public Domain Aeronautical Software which included this implementation of a program to compute airfoil profiles for NACA wings. It’s written in “modern FORTRAN”, which isn’t my preferred language of choice, but I think it will be excellent to use it to verify the profiles produced by my Python code.

Just a tease, here’s some GNUplot output for a 6412 airfoil (the wing is fairly cambered with the maximum occuring at 40%).

The NACA 4 Digit 6412 airfoil. Not checked, and not properly to tscale


Comment from Doug Weathers
Time 11/14/2012 at 11:06 pm

I wrote one of these in MATLAB for a school project a few years ago. I used it to compute cross-sectional area of airfoils to calculate masses and moments of inertia for various airfoils.

I have a copy of Abbot – do you want scans of anything in particular?