Hello
The lift equation for airplane's wing is:
L=(1/2)*ro*S*CL*V^2
In the case of a rotating wing the mean lift of an untwisted rotor is in actual fact 1/3 the maximum lift at the tip because the lift profile is a parabolic curve.
Thus the lift of a fixed wing becomes modified to lift of a rotating single wing.
L=(1/3)*(1/2)*ro*S*CL*V^2
L=(1/6)*ro*S*CL*V^2
This was quoted from a book on helicopter design by John A. Drake. I have three questions:
1-When I look at helicopter rotor it look almost exactly like the airplane wing. My question is Is this formula applicable to airplane propeller? If not what is the right fomula?
2- I hear that propellers are optimised for hovering and for propulsion. Can the usual airplane propeller be used to lift a payload vertically? What is a "shrouded prop"?
3- Electric motors have "No-load speed min -1". I assume that if I use a smal propeller I would get less rpm than the "No-load speed", and if I use still larger propeller the rpm will reduce even futher. Is this a correct assumption. Is there a formula for taking into account the weight and drag forces of the propeller itself.
Thanks
Tom
The lift equation for airplane's wing is:
L=(1/2)*ro*S*CL*V^2
In the case of a rotating wing the mean lift of an untwisted rotor is in actual fact 1/3 the maximum lift at the tip because the lift profile is a parabolic curve.
Thus the lift of a fixed wing becomes modified to lift of a rotating single wing.
L=(1/3)*(1/2)*ro*S*CL*V^2
L=(1/6)*ro*S*CL*V^2
This was quoted from a book on helicopter design by John A. Drake. I have three questions:
1-When I look at helicopter rotor it look almost exactly like the airplane wing. My question is Is this formula applicable to airplane propeller? If not what is the right fomula?
2- I hear that propellers are optimised for hovering and for propulsion. Can the usual airplane propeller be used to lift a payload vertically? What is a "shrouded prop"?
3- Electric motors have "No-load speed min -1". I assume that if I use a smal propeller I would get less rpm than the "No-load speed", and if I use still larger propeller the rpm will reduce even futher. Is this a correct assumption. Is there a formula for taking into account the weight and drag forces of the propeller itself.
Thanks
Tom
