David Carter wrote:

For Marvin Kay and others who will compare performance of 3 blades vs 2
blades

Since it is usually true about airplanes (& lots of things) that when we
change one thing, we also change another, I'd like to tie a previous
"thread" to this 2 vs 3 blade thing::
    -  Since at least some of the Lancairs are getting significant MAP
"boost" from prop cramming more air into engine combustion air intake, and
my local friend even canted or angled his intake to be more in line with
incoming local air flow from prop, . . .
        --  You folks who compare 2 to 3 blades could take a careful reading
of MAP at several airspeeds, cruise and max power, before pulling the
original prop and then repeat those data points with the prop with different
number of blades.
                ---  It will be interesting to see if changing to 2 blades
from 3 will decrease the "boost" from ram air..  If so, then we will have to
take a new look at the old truism that "2 blades are more efficient than 3".
That will always be true for "prop efficiency", but in the larger view of
overall engine power output and resulting aircraft cruise or top speed as a
function of both prop efficiency and "ram air boost", then we could see, for
a given engine rpm and MAP  1) no change in speed, 2) less speed, 3) more
speed.

David Carter

 
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