Guys
If you can get a copy of "Practice's Notebook", long out of print, do. Mine's is 1955 and at home.
The chapter on gyroscopic forces versus number of blades explains why many WWII pilots and before that were deemed guilty of "overspeeding" when blades flew off two-bladers.
The only thing I can find in a hurry is
http://naca.larc.nasa.gov/digidoc/re...NACA-TR-19.PDF
They key phrase is (Bless you Bill) something like this:
"The aggregate gyroscopic moment transmitted to the shaft by a 2-blade propeller is variable and at all instants equals twice the moment of one blade.... for a steady running multi-blade the aggregate... is constant and at every instant equals the geometric sum of the varying moments of the individual blades".
Now, shades of the "Flight of the Phoenix" and all that where the German model aircraft designer gets his slide rule out. Look up Martin Hepperle's excellent site. Select the Clark Y family of airfoils and have fun exploring efficiency. His Java Applet is okay right on up to M0.55 ATR42/72 and Dash-8 sorts but falls over a bit when trying to sort out A400M fact from fiction.
I tried to look up Bill the other day [he is 94] and was told he is golfing this afternoon and won't be back till late because he's booked to play jazz at the "Coach".
Wow.