> I am not convinced that two blades are more efficient than three.
Especially on the > Rotax 912S which has a higher reduction ratio. It
may be more efficient to have two > blades at high speeds but my money
is on three blades in the takeoff and climb phase.
I certainly couldn't comment on the theoretical differences between two
blades and three, but I thought those of you who don't see the US newsletter
might be interested in Bob Berube's reported performance figures for the
company demonstrators. Their monowheel has a 914 with an Airmaster prop,
and shows 1250 feet per minute at gross and 1650 solo. Their tri-gear has a
912S with the Whirlwind prop, and it gets 1100 fpm gross, and 1750 solo.
Pretty similar performance, though the Airmaster benefits from more
horsepower on a slicker airframe. I think the primary lesson is that any
constant speed prop will deliver a large performance improvement over fixed
pitch, regardless of the number of blades.
Dave DeFord, #A135
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