Dennis.Kirby(at)kirtland.
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 Posted: Wed Nov 22, 2006 6:44 am Post subject: New Prop |
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Classification: UNCLASSIFIED
Kolb Friends -
I switched props on my Mark-III, and am happy to report a noticeable
performance improvement. I'm running a 912ul.
Went from a Powerfin 3-blade 70-inch diameter to a 72-inch diameter
(still a Powerfin 3-blade). The extra 2 inches diam appears to have
increased my indicated airspeeds by 3 mph, for the all the same power
settings between 4200 and 5200 rpm. I'm happy with it! And there is
still 2 inches of clearance between the prop tip and the tailboom.
Noise level, however, is somewhat increased. (Time to start looking for
a ANR headset!)
Since I do all my cruising below 5000 rpm, I figured I'd take advantage
of the "larger prop turning slower is more efficient than a smaller prop
spinning fast" principle. Here are the numbers I'm seeing, for this
bone-stock Mark-III:
RPM IAS
4400 58
4600 62
4800 68
5000 72
Since these indicated airspeeds were taken at 8000 feet msl, converting
for altitude puts my true airspeeds at about ten MPH faster, across the
board.
Dennis Kirby
912ul, Powerfin-72, 60 hrs TT
Cedar Crest, NM
Classification: UNCLASSIFIED
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