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  #1  
Old 10-21-2020, 08:22 AM
BH1166 BH1166 is offline
 
Join Date: Nov 2017
Location: Eatonton Georgia
Posts: 344
Default Need more giddy up.....

I own a 28 year old 6A with a O320 with a 28 year old Bernie Warnke almost constant speed wood prop. Prop is 72 x 72, urethane edge, and is in like new condition. Prop is great at cruise, 7 gallon an hour at 2350 rpm / 150 TAS. Static 2400 rpm, WOT 2480 rpm. On a budget, aka I’m a tight wad. Would like to improve takeoff ( takes a long time/ distance to get to rotate speed) maybe better climb as well.

Question, could someone in the wood prop business, cut this prop down to ??? in to increase rpm and enhance TO roll / climb with minimal impact my cruise?
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  #2  
Old 10-21-2020, 10:07 AM
iwannarv iwannarv is offline
 
Join Date: Aug 2005
Location: Olathe, KS
Posts: 431
Default

While not the 'cheap route', have you considered a ground adjustable composite prop such as the WhirlWind?
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  #3  
Old 10-21-2020, 10:31 AM
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Brdog42 Brdog42 is offline
 
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Location: Cone of Confusion
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Default

Butch,

Give Frank a call.

http://www.performancepropellersusa.com/
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  #4  
Old 10-21-2020, 01:16 PM
tgibbs tgibbs is offline
 
Join Date: Jun 2012
Location: Winchester, CA
Posts: 87
Default

Wouldn't the pitch have to change to see significant gains in takeoff distance? I see spinning faster with a shorter prop but I can't imagine the difference is that much.
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  #5  
Old 10-21-2020, 03:46 PM
Bicyclops Bicyclops is offline
 
Join Date: Oct 2012
Location: LA, California
Posts: 357
Default

You already see a higher static RPM than many with fixed pitch which makes it a bit of a climb prop already. If you have it re-pitched for higher static RPM, it will hurt your top speed unless you are willing to perhaps exceed redline. Cutting the diameter will have similar results, higher static RPM and probably lower top/cruise speed.

If your wot 2480 RPM is in cruise, perhaps a little less pitch would help speed by getting you some more power from higher RPM. Perhaps the wood prop is thicker than optimum and a composite prop would be more efficient for both climb and cruise. Craig Catto?

Ed Holyoke
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  #6  
Old 10-21-2020, 07:05 PM
BH1166 BH1166 is offline
 
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Location: Eatonton Georgia
Posts: 344
Default Thanks

You don’t know what ya don’t know. Thank you for the input. I have reached out to Frank Johnson at performance propeller.
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  #7  
Old 10-21-2020, 07:23 PM
RVDan RVDan is offline
 
Join Date: Jun 2012
Location: Frederick, MD
Posts: 867
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If you want real improvement, and the engine is properly configured, go to CS. It deals very well with the takeoff condition and the cruise condition. Probably similar cruise, but takeoff would be greatly improved.
With fixed pitch you either get takeoff/climb performance or cruise, or somewhere in between but not all like CS.
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  #8  
Old 10-22-2020, 06:23 AM
PropMan PropMan is offline
 
Join Date: Dec 2008
Location: Donie,Texas
Posts: 202
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Butch,

You have what we call a Warnke Toothpick. Sounds like it's going into flutter at higher rpm, thats why you can't achieve more than 2480 wot. Typically, if you make 2400 static you should see at least 2700-2800 wot. I'm happy to help.

Give me a call, 713-417-2519
Frank
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  #9  
Old 10-23-2020, 11:06 AM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
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There's a comment from Van himself on the Front Page today, Friday October 23. (Now it's on post #12 below).

It's pretty interesting....

Dave

Last edited by David Paule : 10-26-2020 at 09:47 AM.
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  #10  
Old 10-23-2020, 12:26 PM
Dart11 Dart11 is offline
 
Join Date: Feb 2006
Posts: 19
Default Warnke prop

I bought one of the very first Warnke almost constant speed props about 40 years ago for use on my Bushby Midget Mustang. Its performance was a mix of good and bad.

It was a very thin propeller with very little area both in the sense of disk loading and also in the sense of strength. This is why it was made from a very large number of laminations (30+). The workmanship was beautiful.

It has been a long time, but my memory is that it turned about 2500 rpm static and about 2700 WOT in level flight (170 knots or so) with an O-235. It was very smooth, with very little inertia. It also exhibited what I thought was blade stall during the early seconds of takeoff. Somewhere around 20 knots the blades would finally get a grip and the acceleration was pretty good. Up to that point there was a sound like cavitation and acceleration was weak.

The thin blades were also very flexible. It was easy to twist the blades a few degrees and I am sure this was the key to the constant rpm.

I considered the prop to be experimental aviation at its finest, offering some real opportunities for some airplanes. I was never tempted to replace it (where it has replaced a cut down and brutally twisted Sensenich club) but neither was I a big fan.
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