O-320, one more prop question
Posted: Fri Feb 17, 2012 5:39 pm
Really depends on your definition of "climb" & "cruise" - these are
arbitrary terms to describe different pitches, and the effects will differ
with engine size.
It is not uncommon to see 10 to 15 mph lower cruise with a finer
pitch prop. You reach a point where the engine can exceed redline even in
climb, at which point the prop loses efficiency. If you go too coarse,
the engine is lugging in all regimes, and the engine cannot develop full
power. I suppose the ideal is one that 'only just' lets you reach red line
rpm in level flight .... ????
This is why a variable pitch prop is so valuable - even if it is only
ground-adjustable. This is why the warp Drive props are so popular !
You could survey the flying Rebels on amphibs, and average the pitch
angles they like. You must convert the angle, in degrees, into inches of
pitch, for most prop makers....
It is said that every homebuilder (who uses fixed pitch props) will
own THREE props - his first guess, his second guess, and the one he is
flying with now !! :-)
........bobp
---------------------------orig.--------------------------------------------
At 03:45 PM 12/14/99 GMT, you wrote:
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arbitrary terms to describe different pitches, and the effects will differ
with engine size.
It is not uncommon to see 10 to 15 mph lower cruise with a finer
pitch prop. You reach a point where the engine can exceed redline even in
climb, at which point the prop loses efficiency. If you go too coarse,
the engine is lugging in all regimes, and the engine cannot develop full
power. I suppose the ideal is one that 'only just' lets you reach red line
rpm in level flight .... ????
This is why a variable pitch prop is so valuable - even if it is only
ground-adjustable. This is why the warp Drive props are so popular !
You could survey the flying Rebels on amphibs, and average the pitch
angles they like. You must convert the angle, in degrees, into inches of
pitch, for most prop makers....
It is said that every homebuilder (who uses fixed pitch props) will
own THREE props - his first guess, his second guess, and the one he is
flying with now !! :-)
........bobp
---------------------------orig.--------------------------------------------
At 03:45 PM 12/14/99 GMT, you wrote:
*----------------------------------------------------*OK...One more prop question.
Has anyone compared a climb and cruise prop on the same airplane? I am
trying to find our how much cruise speed you lose with the climb prop and
how much climb you lose with the cruise prop. Right now we are leaning
towards the climb prop for the areas we will be mostly flying in. Thanks
again in advance.
BB&R Amendala
Rebel 669
Olympia, WA
Mounting the stab/elevators
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*----------------------------------------------------*
The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*----------------------------------------------------*
The Murphy Rebel Builders List is for the discussion
between builders and owners of Murphy Rebel aircraft.
Archives located at:
http://www.dcsol.com/murphy-rebel/lists/default.htm
*----------------------------------------------------*
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