Re: Prop Efficiency

From: John Kagan <john_kagan_at_hotmail.com>
Date: Wed, 23 Aug 2006 03:13:55 -0000

--- In Indoor_Construction_at_yahoogroups.com, "markdrela" <drela@...>
wrote:
> ...One advantage of the Larrabee method,
> and other related methods (Xrotor, Liebeck/Adkins, JavaProp, etc),
is
> that they will determine the correct blade area needed to achieve a
> specified cl value, subject to other inputs such as speed, RPM, and
> torque.

Hi Dr. Drela,

Regarding the speed variable (forward speed) for an Indoor prop in
Javaprop, etc., is it reasonable to use a value somewhat higher than
the actual forward speed of the model? And, if so, do you have any
recommendations for what value to use?

I'm envisioning the extreme case of a hovering helicopter. The
vertical speed is 0, but there must be some airflow since the rotor
isn't stalled (right?). It seems that a nose up F1D would be part
way toward that situation, with a prop speed relative to the
surrounding air higher than the speed of the plane.

Forgive me if I have this all wrong…your previous post has even a non-
physics guy like me playing with the analysis programs!
Received on Wed Aug 23 2006 - 00:59:24 CEST