Upwash

[Richard Miller]

Dave, and Whomsoever,

Suddenly I've got know the angle at which the upwash intersects the leading edge of the wing. As soon as I'm instructed how to, I'll forward an illustration of the end of an eagle's wing, taken from below, that shows the extreme - in the range of 20 degrees - negative angle of incidence of the leading primary.

One of my long-range projects, one I've been working on for years and years, is the tip configuration, which is why this matters to me now.

It occurs to me that the angle might coincide with the steepest point on the face of the typical [water] wave, if there is a typical wave, as I imagine there must be. I also imagine that the laws of hydrodyanmics dictate that angle and that it can be calculated, and probably has been. I need to know it.

Then, would it be scale invariant? Would it vary with speed or with the lift coefficient? These are the kind of things I'd like to know, and any leads or comment are welcome.

-Richard

[Wells]

Richard,

Andy Lennon shows a formula for induced angle of attack, that is:

18.24 * Cl * (1 + T) / AR

Tau is a correction factor for non-elliptic lift distribution and seems to be between 0.05 (for typical taper ratio of 0.5) up to 0.15 for no taper. AR is aspect ratio. How this formula is derived, I'm not sure, but it's in his book,

"Basics of R/C Model Aircraft Design"

ISBN: 0-911295-40-2

[Richard Miller]

Wells,

I've copied out the formula and will work on it presently, but I'm not sure I'll understand what I get because a) I have a devil of a time with math, and 2) I'm not sure what is meant by "induced angle of attack".

As a guess I'd say the angle vis-a-vis the on-coming flow that the airfoil is induced to assume as a result of all the relevant variables. In other words just what we call the angle of attack.
The illustration of which I spoke, and the investigations of Bob Hoey - The Turkey Buzzard - appear to indicate that the angle of the flow at the leading edge is on the order of [at least] 20-degrees negative. i mean that the local flow, there, approaches at that angle.

In any event, thanks for the input. I'll keep at it till I've figured it out.

-Richard