How can a NACA2312 airfoil or similar have a camber location from 30 to 39% without a change in airfoil name?

Was fooling around in javafoil, and noticed I could go from 30% camber to 39% camber, without the NACA number of the airfoil changing!! What the heck?

What name is used to differentiate NACA2312 with 30% camber location and NACA2312 with 39% camber location?


The NACA airfoil numbers are coded as follows:

$$ \mathrm{NACA} \; M P XX $$

  • $M$ is the maximum camber divided by 100. In the example M=2 so the camber is 0.02 or 2% of the chord
  • $P$ is the position of the maximum camber divided by 10. In the example P=4 so the maximum camber is at 0.4 or 40% of the chord.
  • $XX$ is the thickness divided by 100. In the example XX=12 so the thiickness is 0.12 or 12% of the chord.

source: airfoiltools.com

In your case you changed the position of the maximum camber ($P$) from 30% to 39%. Both result in $ P = 30 / 10 = 3 $ and $ P = 39 / 10 = 3 $ (when using integers, no rounding is applied). The airfoil name therefore only tells you the position of maximum camber with a 10% accuracy.

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.