Why are Helicopters with the Flettner-System so slow?

[Dave_Jackson]

Mart,

These rotor specifications on the Sikorsky S-69 (XH-59A) ABC might help with your calculations.
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Of related interest:

Here is a web page on the little known Praga , an early Czechoslovakian intermeshing helicopter. The pictures are easy to read.
Web page link thanks to quadrirotor.


Dave