ounces with a 1,650 mAh LiPo. Bob and I have concluded
that the weight savings was because of the availability of all
of the new, lightweight electric hardware.
The electric motor, ESC, and battery weigh significantly
less than the .10-size engine, fuel tank, tubing, and the
throttle servo and its linkage. Other weight savings can be
attributed to using the lighter microreceivers, servos, foam
wheels, and lighter hardware. Using Solarfilm instead of
MonoKote also reduced the weight.
The initial effort was a trace of Bob’s design where I
laid out the parts in CAD and replaced the . 10 O.S. Max
engine with an E-flite 450 brushless outrunner. I carried
the fuselage sides past the original firewall and drew the
electric motor mounted to a laminated nose block ending in
a plywood nose plate.
The motor is accessed through a removable top hatch.
The primary advantage to mounting the motor this way is
that it eliminates the need for a separate fiberglass cowl. The
most significant change at this point was to design the central
fuselage into a tabbed and slotted-box design that made it
easier to build the fuselage straight.
Not wanting to have to turn the model on its back or take
it apart to change the batteries, I designed a removable hatch
for the cockpit area, providing access to the flight battery and
servos. The motor and battery hatch are held down with rare-earth magnets.
The only other alteration I made was to change the landing
gear mount from solid hardwood blocks to built-up plywood
assemblies. This was done for those modelers who don’t have a
small saw to do the slotting work. The airframe is self-aligning
sheet wood with everything but the hardwood blocks and
hardware included in the short kit.
The wing construction evolved from a traditional method of
slotted LEs and TEs to a more modern version using all laser-cut parts. Cover your plans with wax paper and pin the lower
spar to the plans. If you can’t get hard balsa, use basswood
because the strength is worth the slight weight gain. Fit R- 1,
R-2s, R-3s and R-3T over the lower spar and into false TE
notches. (Note R-3T is slotted to accept the wingtip former.)
Ensuring the ribs are aligned with the plans and are
perpendicular to the spars, pin them to the building board.
Glue them to the lower spar and notched false TE using thin
CA. Glue the top spar to the ribs and install the notched false
If using the short kit, the bevel for dihedral is already cut
and you need to correctly position it. Install the 1/8-inch LE
and 1/4-inch TE.
Install 1/16-inch plywood R-2As, with the 3/32-inch sheer
webbing centered between the upper and lower spar. The
grain should be vertical or perpendicular to the spar grain.
Install the aileron servo mounting plates. Tubes to route
aileron servo wires are made from scrap paper and glued
between R- 1 and R- 2 prior to joining the wing halves and
planking the center section.
50 Model Aviation OCTOBER2013 www.ModelAviation.com