Re: RE: RE: RE: RE: Effective AOA on prop blades?

From: William Gowen <wdgowen_at_gmail.com>
Date: Wed, 2 Oct 2013 10:00:14 -0400

I can't vouch for how this works on F1D but my toy airplanes seem to like
this scheme.
On Oct 2, 2013 5:36 AM, <RLBailey_at_care4free.net> wrote:

> **
>
>
> This discussion reminds me of an episode about 10 years ago when 2 well
> known F1D fliers proposed an F1D layout which was designed to keep the prop
> shaft aligned with the direction of flight. Some tests appeared to show a
> significant improvement. The only flier to get any real success in UK was
> Ron Green who is sadly no longer with us. Despite much determined effort I
> had no success with these; the rest, as they say,is history!
>
> Far more to this topic than meets the eye!
>
> Bob
>
> On Oct 1 2013, leop_at_lyradev.com wrote:
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> Obviously, the explanation and examples assumed straight ahead, level
> flight. Depending on the diameter of the turning circle, the forward
> airspeed is different on the sides of the plane but that just goes into
> calculating the advance for the various prop radii if one wants to get into
> that much detail. The upward (or downward) tilt of the propeller also
> affects, to a greater degree, the AoA of the blade. For nose up prop
> angles, the "downward" moving blade (the one on the right side for the
> usually indoor direction of prop rotation) sees a larger AoA than the left
> side. This difference creates a thrust difference which help turn the
> plane. This is called the "P-factor." This is accounted for in the
> differing pitch angles for the left and right side of the prop, plus and
> minus 2 degrees in your example. So, the equations work in these cases if
> one realizes that the airspeed and pitch angles change with the circle
> diameter and nose angle respectively. LP ---In
> Indoor_Construction_at_yahoogroups.com, wrote:and doesn't the prop on the
> outside of the circle see a lower AoA (when the nose is flat)? ---In
> Indoor_Construction_at_yahoogroups.com, wrote: But what if the nose is up by
> two degrees ;-) ? ---In Indoor_Construction_at_yahoogroups.com, wrote:
> A short
> time back, I posted about using the Advance Ratio to understand some
> aspects of
> propellers. The advance of a propeller
> is just how far forward the plane moves in one revolution of the prop. One
> definition of the Advance Ratio is just
> this distance divide by the diameter of the prop. This is similar to the
> P/D ratio (pitch
> divided by prop diameter) that we often speak of. The advance of a
> propeller is just:Airspeed
> / (prop angular speed)
> In usual
> units: advance = air speed
> (inches/minute) / prop rpm
> One can calculate
> the angle of the prop blade at each radius using the pitch of the prop:
> tan(angle)
> = pitch / (2pi x radius).
> One can calculate
> a similar angle using the advance, A :
> tan(advance
> angle) = advance / (2pi x radius).
> The advance
> angle is the apparent angle of the air as seen by the prop blade at each
> radius.
> Since
> the pitch angle is the angle of the prop blade, the difference between the
> pitch angle and the
> advance angle is the angle of attack (at each radius):
> AoA =
> arctan (pitch angle) – arctan(advance angle)
> I hope
> this answers your question. Post if this
> is too confusing or if you have other related questions.
> Leo
> ---In Indoor_Construction_at_yahoogroups.com, wrote:Greetings.
> Let's say I know RPM and the angle a blade is formed at.
> I am finding all sorts of references to the effective angle of attack
> changing as airspeed changes. But nothing as far as how you calculate it.
> Can someone point me to the math equations for calculating the effective
> AOA?
> Regards.
> Mike Kirda
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
Received on Wed Oct 02 2013 - 07:00:16 CEST