Grayhawk: your comments on Paul Lipps and his propellor drag
might be seen as an uninformed attack. I highly pitched fixed
prop has MUCH less drag that a typical C/S prop that reverts
to flat pitch when the engine quits. My 235 has a 64x78 wood
prop, and like Paul's has a glide ratio of well over 10:1 with the
engine idling or with the mixture cutoff. I haven't measured it
with the prop stopped.

Also like Paul's aircraft, mine takes a while to stop on the runway.
This is a definite disadvantage of a highly pitched fixed prop.
It is also a challenge when descending in formation with draggier
aircraft, including LNC2s with a flatter prop.

Paul seems to be a pretty smart guy that knows a thing or three
about prop drag. I don't think he was quoting from an advertisement,
or resorting to numerical mumbo jumbo. Also, his prop is quite a bit
different. The thin tips probably reduce gliding drag relative to my
more ordinary thick  wood  prop.
He did claim 15:1 with the engine idling and not with the prop stopped.
That seems reasonable to me... and I've got a lot more hours without
an engine than with.

-bob mackey

 

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