Although it looks unorthodox, the
Parallax behaves normally in flight.
Irecently set out to expand my understanding of asymmetric aircraft. When I began this quest for knowledge, I had the classic examples of asymmetry
in mind—namely the Blohm und Voss Bv 141 and Rutan
Boomerang. Both of these designs are proven successes, yet
their unconventional configurations make one question
how they can even fly in a straight line.
My breakthrough came when I realized that nearly
all propeller-driven airplanes are asymmetric to some
degree. With one or more propellers generating a
spiraling slipstream, torque effects, gyroscopic forces, and
sometimes uneven thrust (P-Factor), it’s a wonder that
any propeller-driven airplane can fly in a straight line! Yet,
straight and level flight was mastered a long time ago.
The destabilizing effects of a spinning propeller
are often mitigated by introducing subtle asymmetries
to the airplane such as right thrust on the motor,
The Bv 141 and Boomerang must contend with those
same destabilizing forces. What makes them appear so
radically unconventional are the unique ways in which
those forces are addressed. Instead of right thrust, the Bv
141 has the motor offset to the left of the airplane’s lateral
centerline. The effect is the same as right thrust, but the
visual impact is abstract and disarming.
After I realized that asymmetry is the norm rather
than the exception, my question changed from “How do
asymmetric airplanes work?” to “How much asymmetry
can be tolerated?” I started with one confidence-building
asymmetric kitbash of a Flyzone Red Hawk (see “The Joy
of Kitbashing” in the August 2012 MA). Next, I set out to
design an asymmetric model that would appear radically
unconventional, perhaps even unairworthy to some,
yet would have stable and predictable flying traits. The
Parallax is the result of these efforts.
by Terry Dunn
47 Model Aviation MAY 2014