NACA Numbers???

[c hinds]

How are they decoded? The aircraft I am constructing has the NACA
Airfoil number of 65(3)518-A7. Any comments or suggestions are
welcome.
Thanks,
Clark

[Cy Galley]

The NACA 5-digit airfoils are set up in a similar manner
to the 4-digit airfoils. The primary difference is the use
of a different camber line. In a 5-digit airfoil, 1.5 times
the first digit is the design lift coefficient in tenths, the
second and third digits are one-half the distance from the
leading edge to the location of maximum camber in percent of
the chord, and the fourth and fifth digits are the thickness
in percent of the chord. For example, a NACA 23015 airfoil
has a design lift coefficient of 0.3, has the maximum camber
at 0.15c, and is 15% thick. Additionally, the first three
digits indicate the mean line used. In this case, the mean
line designation is 230. The 5-digit airfoils use the same
thickness distribution as the 4-digit airfoils. This example
is displayed below.

NACA 23015

NACA 230 mean line (230)
15 thickness, % (15%)

NACA 2 (design lift coefficient * 10) / 1.5, (0.3)
30 2 * (position, maximum camber), (0.30 / 2 = 0.15c)
15

NACA 23
0 type of camber line used
15

"c hinds" > wrote in message
om...
> How are they decoded? The aircraft I am constructing has the NACA
> Airfoil number of 65(3)518-A7. Any comments or suggestions are
> welcome.
> Thanks,
> Clark

[Dave Hyde]

c hinds wrote

> How are they decoded? The aircraft I am constructing has the NACA
> Airfoil number of 65(3)518-A7

6 is the series number (near-laminar, low drag), the first 5 is the
location of minimum pressure (50% chord), the second 5 is the
design lift coefficient x 10 (0.5) 18 is the thickness (% chord).
The subscript 3 means it's near-laminar (or low-drag) within
+/- 0.3 CL of the design CL, or at lift coefficients from
0.2 to 0.8. The a-number (should be less than 1) is the
chordwise percentage of the airfoil that has a uniform pressure
distribution, in this case (probably) 70%.

Clear as mud.

Dave 'keep it clean' Hyde

[c hinds]

Thank you! Clear and concise.