Originally Posted by Dave Jackson
In addition, the conceptual design objectives of electric rotorcraft will be very different from that of current helicopters. The emphasis will be directed at just keeping the craft off the ground for a reasonable period of time.
Dave, i've searched for a way to justify electric or hybrid helicopters and reached a final conclusion: you just can't!
The problem is that they are way too aerodynamically inefficient to be powered by anything other than IC engines. Future fuel cells may well deliver, but we are just not there yet ( believe me if i had the time/cash...). I was amazed when the R22 had a "glide slope" about the same as a parachute canopy, ie pretty lousy. The Demona was chosen for the I.E./Boeing project since it has a glide slope of about 26:1 (from memory), so you can cruise on the cell with batteries only required for takeoff power.
You had a good idea with Independant Root and Tip control. To my mind this is the way forward with helicopter fuel consumption. I genuinely believe that HCs like cetane are still the way to go for helicopters, whatever their original energy source. Concentrate on optimising the rotor AOA, but accept that you have to use an aerofoil that doesn't suffer in reverse flow. This then really justifies your symmetric concepts, especially at higher speeds.
Mart