> If you want to come up with some kind of prop aspect ratio, you must
> come up with an artificial area based on Q times element area to divide
> into span-squared; with a rectangular plan form prop, that area
> distribution would look like a very narrow hub expanding exponentially
> to a very wide tip. You're wasting your time chasing this elusive
> "induced drag" based on aspect ratio. You can solve for this ID by
> looking at the inclination of the 2D lift when induced AOA is solved.
> When you solve for IAOA, you don't have to come up with an AR-modified
> lift slope. You only do that when you don't know the IAOA! Don't forget
> to apply some form of lift roll-off as you near the tip. I have found
> the Shrenck method works well.
> Since you seem to question my approach, don't forget that my prop
> design equations give prop performance to much better than 1%! My
> estimates of a prop's performance on a plane it was designed for get
> within 1 mph at a given rpm and dalt. Ask Tom Aberle! I'm just trying to
> get you back on track and save you some time with what I have found
> through my chase of prop info; if you are not interested in what I've
> learned, let me know and I'll cease and desist!
>
> Paul Lipps.
>
> I am not questioning your approach Paul. I think highly of the
> results. What ever method you use for designing the prop
> obviously must work. My main concern is finding a simple
> mathematical spread sheet that will accurately predict
> the twist, pitch and plan form so we can use it to recommend
> a particular prop design given the wide disparity
> in rotary engine powered aircraft types. This has been an
> on going proplem for us for the past seven years.
>
> Perhaps you have one that you can share.
>
> Paul Lamar ...No rotor no motor.
I do, but it's proprietary! But I'm still trying to give you some
insights into what works, and works well! Paul Lipps
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