All,
Thanks again for your replies and help.  Since my
question piqued some interest, I have attached my
preliminary concept drawings.  My thought is for a
fuselage similar to a sailplane, with 2 tandem seats.
Very narrow and only as long as it needs to be, but
with a more upright seating position.
I might have to sweep the wings for aerodynamic
center of lift / center of gravity purposes / and main
gear balance purposes.  While
not strictly to scale, I have 'shown' a 60-inch dia
prop in the pusher version.

The high-nacelle "tractor" version is not to scale, but
I am concerned about high speed stability with the
prop thrust line up high.  I want 350 knots cruise
AND reasonable stall speed!!

The 'smaller diameter prop' idea was mainly to allow
shorter main gear, and allow the engine nacelles to
be close together, thus keeping the overall size of the
airplane as small as possible, but small props are
not mandatory.  I am trying to minimize the adverse
yaw effects of single engine loss, and use two
affordable 2-rotors in a marketable version.

I have read a little from Jack Norris  and have seen
pictures of the Whirlwind props.

Thank you all for your help and comments.

Gene Kahn


Hi gene,

The 3 surfaces Piaggio P180 (aerodynamics were developped with NASA)


Is a very efficient airplane (payload, speed, range vs power) with 2 x
850 HP

A reduced scale version (about 1/2) with a little more wing surface...
and 2 x 200 HP turbonormalized wankels
could be quite impressive...

Philippe
(France)

Jean Prudhomme is working on a scale rotary powered  kit.

Paul Lamar


Something similar to the Rutan Pond Racer might be a good
configuration to consider.  Though, I'm not sure why Burt put a
central cockpit pod on the aircraft.  More intersection drag and
frontal area.  It seems he could have instead done what he did with
has later Boomerang design - put the seating in one boom (the
fuselage), and have a small boom with engine and landing gear in the
other.


The Pond Racer:

http://en.wikipedia.org/wiki/Scaled_Composites_Pond_Racer

http://www.youtube.com/watch?v=66q4awWPArM

A 400mph lap time is still pretty fast.  And that was done at 5000MSL.
The Pond Racer surely would have gone much faster at altitude.


The Boomerang:

http://en.wikipedia.org/wiki/Scaled_Composites_Boomerang

http://www.scribd.com/doc/36314339/Rutan-Boomerang-Popular-Mechanics-Nov-96

Lists max cruise as 304mph with 2 turbocharged 200hp Lycomings.  A
smaller cabin, and rotary engines would allow even higher speeds.


Matt-



Philippe, Paul, and Matt,

Thanks for all your comments.  I love the Avanti, and
Jean P's design.  Mine will be different in that I don't
want even a canard blocking any view from the cockpit.
I explored the idea of twin tractor props in front, and
immediately thought of the Pond racer as well as the
CriCri,  It looks like the Pond racer's cockpit is where it is
because the props could be moved close together
to help insure against uncontrollable adverse yaw
during racing.  And speaking of small props, the
CriCri does well on 2X15 HP turning those small
props.  You might argue that a single larger prop
turned by 30 hp would be more efficient, and you
would be correct, but that would also require a
different structure, larger gear, etc, with some
weight penalty.  So one would have to just do
the overall math to find out what the net gain or
loss is with each scenario.

But thinking of the rotary, I have been thinking of
how to protect against the possibility of in-flight
flooding of the combustion chamber [which could
be very difficult to restart...??]  Perhaps there could
be a way to transiently cut off the fuel mixture in the
case of flooding, and then let the rotor cycle many
times to "dry it out".  It could take the form of a simple
cut-off switch just before the fuel injector.  There should
be enough residual heat in the engine to evaporate
the fuel in short order.  Perhaps this is never a
problem once the engine warms up?

Gene Kahn


It is the total area of the prop or props that count.
Never a problem with the engine warm.

Paul Lamar