Re: Re: Bernard Hunt EZB Pitch Specifications

From: James Alderson <aldershine_at_hotmail.com>
Date: Sun, 8 Sep 2013 21:45:32 -0700

Thanks Mike! I really value your input. Thanks for the quick response. "Oversimplication" is okay for now. I can get educated as I go along. I already suspected uniform spars and blade flex were crucial factors. I have one 25" pitch block I got from Jake Palmer that I will use for F1L.

Higher Times!

James Alderson

Sent from my iPhone

On Sep 8, 2013, at 8:19 PM, "mkirda_at_sbcglobal.net" <mkirda_at_sbcglobal.net> wrote:

> Here are the numbers.
>
> 22.5 26
> Angle 3.5 Angle
> 1 74.4 77.9 76.4
> 2 60.8 64.3 64.2
> 3 50.0 53.5 54.1
> 4 41.8 45.3 46.0
> 5 35.6 39.1 39.6
> 6 30.8 34.3 34.6
> 7 27.1 30.6 30.6
> 7.5 25.5 29.0 28.9
> 8 24.1 27.6 27.4
> 9 21.7 25.2 24.7
> 10 19.7 23.2 22.5
> 11 18.0 21.5 20.6
> 12 16.6 20.1 19.0
>
> Column one: At each inch station
> Column 2: 22.5"P helical block
> Column 3: Same 22.5" blade rotated +3.5 degrees
> Column 4: 26" helical block
>
> Note nearly +2 degrees AoA at 1". Move in a bit and there is a bit of wash-out in the middle of the blade. At around the tip of an F1L prop (7-7.5") there is no difference. Only when you get further out do you see the wash-in again.
>
> At the risk of oversimplification, I see someone who has a block that is pretty close in pitch to what they needed, made a blade and mounted it to the spar rotated to the pitch they needed. As you can see, rotating the blade a couple of degrees makes very small differences in AoA over the blade overall.
>
> I suspect it will be far more important to have the prop spars with equal torsional rotation when loaded and blades that flex similarly.
>
> Regards.
> Mike Kirda
>
>
Received on Sun Sep 08 2013 - 21:45:37 CEST