Bill Freeman wrote:

Paul,

Here is a discussion of flat plate drag, and they reference
Hoerner on flat plate drag coefficient.   Scroll down until you
see the flat plate stuff, the reference is a "72", which is a link to
the Hoerner reference.

  http://www.hq.nasa.gov/office/pao/History/SP-468/ch1.htm

Bill

I'll scan the Hoerner page for you when I get back from going shopping with Robin.

BTW if the Wright Brothers did indeed invent C sub d which I doubt their
reference object (area) could have been poorly measured in their wind tunnel.
Later reference ojects/areas may have  measured differently in later wind 
tunnels but things have settled down in the last 70 years.
It is like the standard for the foot and all other measuring devices.
The tolerances have been narrowed down due to certain accepted unique standards.

 
Paul Lamar
 
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