Comment by jameshart
2 years ago
NACA airfoils aren’t so much a numbered set of standard, tested designs as a useful set of mathematical curve formulae for making airfoil-like shapes, and describing them using parameters.
NACA published empirically determined wind tunnel performance numbers for selected parameters, which was useful research but not a declaration of ‘these are the good values, you should only use these’.
It’s a bit like saying all satellites follow TLE orbits derived by NASA/NORAD in the 1950s - they do, but only because that’s just a standard way of writing down the orbital elements that describe a particular ellipse, not a catalog of ‘known good’ orbits.
my recollection was that the P51 wing used a NACA airfoil and it had low drag properties not commonplace at the time