Originally Posted by corocopter
Heli Halle / Gary,
Thanks for posting those two videos; they demonstrate the affect of the stability created by the spinning prop. The upper single motor craft is much more stable, the lower twin motor craft cancels out the gyroscope stability making the attitude guidance system work much harder to reduce the oscillations in the pitch and roll axis.
Actually, not quite. A counter-rotating setup will be slightly more stable than a single rotor setup, because the two rotor precessing moments will cancel each other out, while their inertia will still oppose the tilting moment. I think that the second, smaller counter-rotating twin had more trouble taking off because the control surfaces will be sitting in a cushion of air when it is on the ground. Indeed they become much more effective once there is some distance from the ground, and I bet that it would be easier to control if it had some form of stub feet. Or, seen the topic, if it was sitting in a lightweight carbon rod cage in the shape of a sphere