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

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?

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