Mart,
At the bottom of this page are the forms that you are asking for.
Helicopter - Outside - Coaxial - Cornu, Paul, 1907 - First flight
The interesting part for me was Leishman's estimate of Ct/Sigma of 0.684
Yes it is interesting. I will look into it, also.
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Leishman's latest book
The Helicopter: Thinking Forward, Looking Back was ordered last month.
Last night, I came across a review of this book. You will find this review interesting.
http://www.rusi.org/downloads/assets...e_0207_RDS.pdf
Dave