The all-foam airframe of the Parallax produces a lightweight and easily
repairable structure. This unit is ready for a coat of paint and finish
The fuselage and pod are constructed of 1/2-inch-thick blue foam, which
negates the need for internal formers. Several Parallax components were
built assembly-line style.
The Parallax is slightly more than a modern adaptation
of the Bv 141. I make no claims that any aspect of the
airplane’s performance is enhanced by its asymmetry. My
position is that little is compromised despite its asymmetry.
This airplane is the foam-and-LiPo embodiment of the
notion that airplanes don’t necessarily have to look right to
The checkmark-shaped wing is an unnecessary deviation
that I felt would add character to the design without
presenting much more complexity. My prototype Parallax
and one of the subsequent test models use a canard for
pitch control. After testing the canard versions and those
with a standard horizontal stabilizer/elevator, I prefer and
recommend the standard route (not something I often
My method for scratch-building is a process I call “stressed
foam.” With this process, there are no wing ribs or fuselage
formers. The external foam structure is all there is. This
makes prototyping new designs simple and quick.
The plans have detailed assembly steps for the airframe.
I will review the basic makeup of the Parallax. The fuselage
and cockpit pod are built with 1/2-inch-thick blue foam
sheet from a home improvement store. I use Depron
foam with a carbon-fiber spar for the wings. Although the
materials and assembly techniques may be new to many
modelers, I think most will find the building process easy.
The Outer Limits
As I write this, I have built five Parallax
models, including the prototype.
from the same
plans, all of them
make them unique.
Why would I want
five of the same airplane? If you decide
to build a Parallax, I encourage you to
add your own touches. Because this is
an unconventional model, I thought it
would be best to guide you on which
modifications are acceptable.
Similar to the Bv 141, the Parallax’s
motor is mounted to the left of the
aircraft’s centerline. The position
shown on the plans has proven to
be the most benign. If you move the
fuselage any closer to the centerline,
it will likely be difficult to balance the
airplane laterally (right to left).
If you move the fuselage farther
from the centerline, the effect of the
offset thrustline will soon overshadow
the propeller effects that the offset is
intended to negate. You’ll be stuck with
an airplane that prefers to turn right. I
suggest you stick to the location shown
on the plans.
One of my Parallax models is a
mirror image of the configuration
shown on the plans. The fuselage is on
the right side and the cockpit pod is
on the left. In this case, I use a reverse-rotation propeller to balance all of the
forces, which works well.
A fundamental design aspect of the
Parallax (as with any airworthy aircraft)
is that there is equal lifting area on
either side of the aircraft’s centerline.
Any part of the wing that is obscured
by the fuselage or cockpit pod does not
provide lift and is irrelevant for this
analysis. For the airplane to properly
fly, it must be laterally balanced along
48 Model Aviation M AY 2014