Well! Well! If this is true looks like we will still get off the ground in
500 feet with
our 2.85:1 psru optimized for 2100 prop RPM and 190 HP cruise.
OK Tracy the ball is in your court. Sorry about all this:-)

Thanks Vance.

Paul Lamar

Mike Wills wrote:

  Well, I was gonna keep my mouth shut, but... Still a little premature
there Paul. Before you put the ball in Tracy's court (he already has enough
to do) lets see somebody actually build the prop, put it on a 2.85 geared
engine and prove it. After all, thats what Tracy (and I) said in the first
place. There is an established performance history for props on the types
of airframes we are building turning Lycoming type RPMs. There is no
established performance history for small diameter, low RPM props on the
types of airframes we are talking about. I get engineers all the time
showing me numbers as proof of their theories and ideas but its not proof
until its built and it works as advertised. I understand all the theory
behind your position but its just theory until somebody proves it. And
please dont cite small turboprop commuters or 1930s era radial powered
aircraft as representative examples. ( BTW, I too am anxious to hear about
the 30s era 150 - 180HP aircraft that exceeds RV performance). Those arent
the kind of airplanes folks here are building and there is no lycoming type
equivalent performance baseline to compare to. Show me an RV, Glassair,
Lancair, etc., something with a well established performance baseline, that
matches or exceeds that baseline with a small low rpm prop.

  And while I'm here, I have another comment. You cant simply shrug off
takeoff and climb performance just because those are features you dont feel
you need. In the RV community takeoff and climb performance are well
established (and bragged about). Build an RV that uses 1000 - 1500 feet of
runway to get off the ground and it doesnt matter how well it cruises, the
airplane is gonna be labeled as a dog. And that label is gonna be
attributed to your choice of engine. I thought one of the goals of this
newsletter was to promote the rotary as equivalent (or even superior to)
the typical aircraft engine? Your not going to do that with inferior
takeoff and climb performance even if its not needed.

Mike Wills

I am counting on you Jerry :-) I don't feel that 1000 feet is still
inevitable. According to Vance the HP increase makes up for the
higher pitch when the blade is stalled.

As it stands now Mike they are calling them dogs because in general
they are not as fast as Lyc RV's. That could change this year if
certain people see the wisdom of entering the Sun 100. The 2.85:1 psru
could change that in general.

Paul Lamar

The horsepower increase by over revving does not automatically show up
at the lower speed. If you size the prop for the higher power at top speed
the power ratio between top and static stays about the same. It only pays off with
the larger diameter - as the table shows a 72 inch slower (steeper) prop
is poorer at static than a conventional speed (normal pitch) 72 inch
prop. The increase in disk area appears to outweigh the stalling loses
with the larger diameter. I have provided you with a landing gear re design 
suggestion for a larger prop on your Cruiser - see attached GIF - Vance

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