NACA sections. What are they?

[18greens]

In a recent flight test article the writer noted the aircraft wing was based on an NACA 12345 section ( I made the numbers up).

What does this refer to , has someone taken every possible aerofoil cross section and numbered them.

Is the number just the next in sequence or does it tell you something about the wing?

[The Greaser]

NACA (Old name for NASA) aerofoils are classifications for different aerofoil cross sections, each one having a unique lift and drag curve. Two of the numbers represent the thickness/chord ratio of the aerofoil (might be the first 2 numbers, can't remember) ie. 12% thickness is represented as 12.
Sorry its vague, its a few years since I studied this.

[john_tullamarine]

The NACA 4- and 5-digit codes provide a geometric indication of the shape of an aerofoil section although the 5-digit methods are a little more complex.

http://www.aa.nps.navy.mil/~jones/online_tools/panel2/naca/ provides an easy to follow description.

There is any number of sites which allow you to draw and play with the section profiles if you wish to do so ..... have fun ...