# NACA 6 digit maximum thickness position ?

Discussion in 'Hydrodynamics and Aerodynamics' started by quequen, Jan 1, 2013.

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### quequenSenior Member

Is there any equation to determine the max thickness position over chord for a symetric 6 digit NACA profile, starting from the profile name only?
I made a simple parametric, table-driven SolidWorks file to modelate traditional fin keels in 3D, interpolated between two different 6 series profiles, at variable maximum thickness %. It works fine but that equation could make things easier.

2. ### Paul BPrevious Member

If you have the ability to use the @IF function in your table you can possibly do this.

If you are simply looking for something like "The third digit indicates the chordwise location of max thickness" then you are out of luck.

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### johneckSenior Member

Oops, wrong airfoil

Last edited: Jan 2, 2013
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### johnhazelSenior Member

Not true, see Wipikidia for a quick look or : http://www.pdas.com/naca456pdas.html

In the above page is a link to the naca documents that give the formulas for constructing the six series. you could use that to make your own max thickness formula.

5. ### Submarine TomPrevious Member

I believe 6-series NACA foils are thickest at 34.9% chord.

6. ### Paul BPrevious Member

Some are, some aren't.

63 series are at 35%.

64 series at 40%.

64 (2) and (4) series at 35%.

64A series at 40%.

65 series at 40%.

66 series at 45%

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### quequenSenior Member

I was thinking on a simple formula to relate the second digit with its maximum thickness chord position. This are the related empirical numbers I found:
63: 35%
64: 37.5%
65: 40%
66: 45%
67: 48.75%
all percents from nouse

attached .dxf with some 6 series

#### Attached Files:

• ###### NACA6series.dxf
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### tspeerSenior Member

No. The NACA 4- and 5-digit sections used a formula to determine the thickness distributions, but the NACA 6-series sections were designed differently.

The NACA 6-series sections were designed by specifying the pressure distribution and then calculating the shape that gave that pressure distribution. The pressure distribution was constant (flat "rooftop") back to the location indicated by the second digit, and then tapered linearly to the trailing edge. This results in the maximum thickness being somewhat near to the break in the pressure distribution, but there's not an easy formula to determine the precise location.

You can develop empirical approximations, of course, and that may be fine for your purpose.

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