ORIGINAL: dick Hanson
ok- bigger props are theoretically better -but in some cases they simply don't do the job -
Yes, but it depends much on how you want your bird to fly with the power you have available.
Focusing only on thrust may be misleading unless you’re intending to fly like a helicopter hovering all the time…
As you obviously know, the diameter of a helicopter prop is much larger comparing with a conventional plane, but the helicopter’s forward speed is relatively much lower.
If you want your bird to hover but also to perform well as a conventional plane, you need to think about thrust and pitch speed.
Roughly, the power absorbed by the prop is equal to thrust times its pitch speed, which is equivalent to torque at the motor shaft times RPM.
Thus, for a given power, the more thrust you have the less speed you get.