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Propeller Carving questions

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Posted

I have an old ground adjustable Warp Drive prop that I have never been real excited about - if nothing else, it has a really big clunky hub that has to be wasting a lot of energy just beating up the air...

20150529_180949.thumb.jpg.eca1b6017c35e7

So, I've been thinking that carving my own might be a fun project. And, the logical first step (at least in my mind) would be figuring out what pitch my current prop is set at. So, measuring tape and bubble protractor in hand, I spent some time at the hangar and came up with the plot of pitch as a function of radius at several points, and this is what I get:PropPitch2.thumb.jpg.9c8103c28f7830e7db7

[The "classic prop" line is from a spread sheet that I found online (http://www.nmine.com/propeller.htm)]

The decrease in pitch from my measurements as it gets towards the tip seems odd to me (assuming my calculations are correct). I would guess that it might be that the blade twist was optimized for some pitch other than where I have mine set - I will play with the numbers a bit. But I would think that the pitch distribution can't be helping my performance.

For those that actually know something - does the pitch distribution for the "classic prop" seem reasonable? Does it look like I did something wrong? Comments?

 

My raw numbers / calculations:

% find the average pitch of a propeller from angles and radial location
% assumes angle of back of blade is the chord angle

% enter data here:
% Angle of hub. degrees (negative means that top of surface is aft of
% bottom)
ah = -8.75;
% Location of angle measurements (inches from center)
dim = [12 18 24 30 36];

% angle of blade at each measurement (degrees) blade 1 and 2 - all
% measurments with blade to port side of the aircraft (leading edge up and level)
ab1m = [20.5 16 10 5 3];
ab2m = [20 16 10 5.5 3];

% end data entry

% correct angles for angle of hub
ab1a = ab1m - ah;
ab2a = ab2m - ah;

% circumfance at each measurement
cir = 2*pi*dim;

% calculate pitch for each point.
p1 = cir.*tand(ab1a);
p2 = cir.*tand(ab2a);

 

 

 

 

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Posted

I have an old ground adjustable Warp Drive prop that I have never been real excited about - if nothing else, it has a really big clunky hub that has to be wasting a lot of energy just beating up the air...

20150529_180949.thumb.jpg.eca1b6017c35e7

So, I've been thinking that carving my own might be a fun project. And, the logical first step (at least in my mind) would be figuring out what pitch my current prop is set at. So, measuring tape and bubble protractor in hand, I spent some time at the hangar and came up with the plot of pitch as a function of radius at several points, and this is what I get:PropPitch2.thumb.jpg.9c8103c28f7830e7db7

[The "classic prop" line is from a spread sheet that I found online (http://www.nmine.com/propeller.htm)]

The decrease in pitch from my measurements as it gets towards the tip seems odd to me (assuming my calculations are correct). I would guess that it might be that the blade twist was optimized for some pitch other than where I have mine set - I will play with the numbers a bit. But I would think that the pitch distribution can't be helping my performance.

For those that actually know something - does the pitch distribution for the "classic prop" seem reasonable? Does it look like I did something wrong? Comments?

 

My raw numbers / calculations:

% find the average pitch of a propeller from angles and radial location
% assumes angle of back of blade is the chord angle

% enter data here:
% Angle of hub. degrees (negative means that top of surface is aft of
% bottom)
ah = -8.75;
% Location of angle measurements (inches from center)
dim = [12 18 24 30 36];

% angle of blade at each measurement (degrees) blade 1 and 2 - all
% measurments with blade to port side of the aircraft (leading edge up and level)
ab1m = [20.5 16 10 5 3];
ab2m = [20 16 10 5.5 3];

% end data entry

% correct angles for angle of hub
ab1a = ab1m - ah;
ab2a = ab2m - ah;

% circumfance at each measurement
cir = 2*pi*dim;

% calculate pitch for each point.
p1 = cir.*tand(ab1a);
p2 = cir.*tand(ab2a);

Thats funny I was at work today thinking how much fun it would be to try to carve my own prop also. What size is the warp and what engine is it on?

 

 

 

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Posted

I've carved quite a few props. Each time I build one it gets better performance than the last. I can tell you that the Warp, IVO and other ground adjustable props really aren't true pitch. They give you an acceptable change with a change in blade setting but don't really give you what you would get out of a properly build to pitch propeller. Just my two cents.

 

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Posted

Was that WD prop repainted?   Don't think I have ever seen a red one with white tips.   EDMO

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Posted

Was that WD prop repainted?   Don't think I have ever seen a red one with white tips.   EDMO

That's the way it was when I bought the airplane. I have no Idea if it may have been painted at some time.

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Posted

Some early IVO props came in different colors, maybe Warp did the same.  Jim Chuk

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