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Propellor design

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jeff naul

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Do you guys think these newer Sensenitch/ whirlwind GAP propellors are as good as say the Catto/prince designs.
Also, if I didnt care about climb would reducing diameter and increasing pitch yield any speed gains? I always read that more diameter is better but its also harder to turn that more diameter. Im running out of areas of airframe cleanup and starting to look at the prop as the last move. Contemplating having my sensenitch GAP cut down in diameter.
Plane is ZodiacHDS/ subaru E81 100 h.p.. 70" Sensenitch 2 blade. Also have 68" warpdrive 3 blade. Sensenitch is 3mph faster but louder and vibrates more. Thx Jeff
 

TFF

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Only anecdotal, on the Biplane Forum a number of people have done back to back prop comparisons. Pure performance has not been beaten from the traditional Sensenich prop. Very nuanced group so they are picking certain traits.

Trying to be apples to apples as much as possible. The Sensenitch ground adjustable was tested on a Pitts by a member for Sensenitch. He is very happy with it. It seems very close to the bar.

The light weight props are showing favor for smoothness and less stress on the crank. They lose a little speed and climb. Crankshaft comfort over 2-4 mph. They actually loose snap roll performance with lighter weight props but happy with saving the crank.

The guy with the Sensenitch ground adjustable is still testing but it is looking like it’s close to equal. Which he is calling a win.
 

crusty old aviator

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Whenever you change your prop, on a homebuilt, you are required to again fly the Phases 1 & 2 test programs to prove the new combination is safe before taking passengers and venturing far from home.
 

Toobuilder

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Re entering Phase 1 (or not) is dictated by the individual airplane's Op's lims letter. Switching from one fixed prop to another fixed prop often does not require entry back to phase 1
 

Dana

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Whenever you change your prop, on a homebuilt, you are required to again fly the Phases 1 & 2 test programs to prove the new combination is safe before taking passengers and venturing far from home.
Phase 1 for 5 hours. Phase 2 is ordinary flying.
 

BJC

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A ground adjustable is a compromise; it has ideal twist at only one set of conditions. At any other set of conditions, a fixed pitch with ideal twist, pitch and diameter will be better. The question is, how much the owner is willing to spend to optomize a fixed pitch to achieve, for most sport airplanes, a small performance advantage.


BJC
 
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TFF

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You can also be in phase with all the props at once. Testing is testing. Calling it finished requires fulfilling the operating instructions. The Sensenitch prop I mention is being tested on two Pitts. A S1C and S1S. A loss of 24 lbs of weight is impressive. I think the plus is within a couple of inches of pitch, the blade should be pretty much in the same twist range. Being able to add or take away an inch or two to fine tune the needs would be great. It would be nice if it could be quick change where you could have the prop biased for climb for local area flying and then being able to add some reasonable number to go somewhere. Adjustable locks. Lock one way or the other.
 

kent Ashton

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Also, if I didnt care about climb would reducing diameter and increasing pitch yield any speed gains? I always read that more diameter is better but its also harder to turn that more diameter.
I broke 1.75" off a 64"D three blade Performance prop (sawed off the other two blades to match) and it made very little difference in RPM or performance. Later I thinned and narrowed the tips and glassed it. Thin tips made a big difference. Gave me about 100 more RPM and of course, more RPM = more HP. That would not work on a prop that was already turning at max engine RPM but my prop did not give me enough RPM before the mods so it helped. Writeup here:
 

crusty old aviator

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The late Bernard Warnke carved lovely wood props with relatively thin blades that would flex a bit depending on RPM. He called them “almost constant speed” props. I‘ve never heard of one failing on its own. He had quite a following in his day.
 

jeff naul

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Very interesting read. Ive heard turning the prop 180 to try and reduce vibration. Is that worth a try when using an PSRU?
 

TFF

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The Performance prop is the Warnke. They are the prettiest props out there for sure.
 
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