George,

Interesting design!  One nice thing about rudders below
the lifting surfaces is that they counteract 'adverse roll'
as well as adverse yaw.  Looks like you have laminar
flow in mind over your fuselage like the Avanti.
Thanks for the advice on using X-plane.  Why did you
decide to go with a smaller prop?  Ground clearance?
What might the advantages of two 2-rotor engines in
tandem instead of a 3 or 4 rotor build?  I am fascinated.
Thanks for your comments.  Gene Kahn



Gene, The smaller prop is the result of increasing cruise RPM for more
HP using Tracy's PSRU which has a 2.85 to 1 gear ratio. I had 12" of
ground clearance with the larger prop which was more than the
recommended minimum of 9" Also the cowl flaps are now lower down and I
wanted them closer to the 3/4 diameter point of the prop.  The reason
for the tandem two rotors is to use the maximum amount of proven stock
rotors, seals, rotor housing, and e-shafts. Designing a new front
housing with a bell housing flange matched to the rear flange of the
second engine seemed easier than dealing with a custom e-shaft,
counterweights, thrust bearing set, and the cooling issues of four
rotors in series.  Early on I looked at useing two engines side by side
with both tilted 45 degrees towards plugs up. The Psru was a stone of
about an extimated 143 pounds.


The fusalogue was the result of spending time with Jean
Prudhomme who is scaleing dow an Avanti  and some input from Alex
Portalatin an aeronautical engineer in Tampa.  Canard aircraft are
thought to require long take off and landing distances and a slow
rotarion to climb at takeoff.  The canard needs a lot of forward speed
to generate enough lift to increase the angle of attack on the main
wing.. Lift is proportional to the speed squared but with minimum alpha
of about two degrees more than the main wing the canard is slow to get
working.  By making it a control canard which is full flying like a
stabulator it can be operated at maximum lift coefficient for takeoff.
The small flap on the trailing edge of the canard is to trim for
different load configurations and fuel burn.The horizontal tail is  an
up  camber eppler airfoil with a  four degree higher stall angle than
the main wing which is an NLF airfoil. The horizontal tail carries much
of the weight of the engine which is sitting on it's spars. The
ruddervators are down cambered but with a near neutral angle of attack
and they are also eppler. This arrangement has a HUGE restoring moment
with a pitch upset. This is harder to explain but easy to see in
X-plane.  If you get the X-plane  program I can post the flight model
which is a small file.

One other thing which gave this plane an Avanti look was flying
the fusalogue at different pitch angles (done by changing AOA of all
wings the same amount) for fastest speed. The frontal area is nearly
identicle but speed went up by 40MPH when optomized and ground clearance
under the prop gained another 8". An added benefit was better visibility
from the rear seat with the tail higher. I had the canard mounted higher
than the wing, but with the realigned fusalogue there were vortex
problems impacting the main wing possibly because the flight model has
blunt tips on the canard. Lowering the canard  solved the vortex
problems but required slightly more wing area.The last step once
you get it sorted out is to read the angle of attack of the main wing at
cruise speed. Then the  thrust angle of the engine is the displayed
angle relative to the wing chord.

george grimes