Build this RC Giant Scale Aerobatics machine
with magazine and Web-site how-to series
16 M ODEL AVIATION
Mike Hurley
We Are ABOuT to embark on an exciting adventure! This is
Model Aviation’s first Giant Scale construction article, and it will
be presented in a “build-along” monthly series. Join us as we
discuss frankly products and services, opinions and options, tips
and techniques, and discuss the rationale behind many of our
component choices. This series will have widespread value for
anyone building any model aircraft. Consider this a set of “howto”
articles using a particular Giant Scale aircraft as the
demonstration platform.
Back to Basics: Scale Aerobatics (SA) has been growing steadily
in popularity in the last several years. Almost every Radio Control
(RC) manufacturer now offers one or more SA models. In
addition, the Almost Ready to Fly (ARF) market has grown by
leaps and bounds, and many of the ARFs available are
International Miniature Aerobatic Club (IMAC)-style SA
airplanes. In this series we focus on a segment of the hobby that is
gaining popularity (SA) while revisiting a skill set that is losing
ground because of today’s top-quality ARFs, but is central to our
hobby: building your own model.
This six-part series will focus on the construction of an
original-design 35% Extra 300LX. A model this size is certainly
not for everyone and in the long run can get quite expensive to
complete. Even if you’re not interested in building this airplane,
don’t let that stop you from getting some useful information from
these articles! These airplanes are state of the art for performance
RC, so the info we present should interest most modelers.
We’ll cover topics from foam sheeting techniques to computerradio
basics. And if you decide that this is the aircraft you’ve been
waiting for, you can purchase the plans and build along with us.
We’ll highlight techniques and tips in the articles and offer a stepby-
step instruction manual with detailed photos via the AMA
Internet site as a PDF download; go to www.modelaircraft.org,
then go to the Model Aviation page for directions.
The Aircraft: The Extra Corporation’s naming convention can be
somewhat confusing, and some RC manufacturers even get it
wrong! To set the record straight, this aircraft is the Extra 300LX.
The “300” designates the design lineage and the engine’s
horsepower. The “L” means it’s a low-wing, two-person aircraft.
The “X” designates the experimental oversized rudder and
elevators.
Extra never produced an aircraft that had the moniker of 330.
Two air-show performers put “Extra 330” decals on an airplane,
and the name just stuck. You can order a 330-horsepower
Lycoming for your Extra 300. The 330-horsepower IO-580 is a
fairly common engine in most newer aerobats these days. I
recently saw an Edge 540 with one at an IAC (International
The completed Extra excels at aerobatic and 3-D Freestyle
maneuvers including the Elevator. It’s an impressive model!
January 2003 17
The 35% Extra 300LX, fitted with a Desert Aircraft DA-100 engine, weighs in at just 27
pounds. These large airplanes are easy to see and to fly.
With some practice, your confidence will grow and you should easily be able to perform
stable inverted passes. Just remember to always fly safely!
Aerobatics Club) meeting, but I didn’t hear
anybody calling it an Edge 580! Phil
Knight has modified the stabilizers and
elevators on his aircraft. The tail
modifications are not FAA (Federal
Aviation Administration)-approved, and
therefore cannot be type-rated in the US.
The modifications can be ordered from the
factory, but the airplane will be designated
as experimental. In this case the airplane
will be called an Extra 300LX or 300SX
(not 330 and not 300XS, as most model
manufacturers mistakenly have it). But be
assured, officially, that there is no such
thing as a 330!
The airplane we’ll build is the third
version of a design I created four years ago
and built with the help of Norm Cassella:
renowned IMAC nationals Unlimited
champion and early Tournament of
Champions competitor. Norm also
designed and built one of the first
competition-level biplanes: the Pulsar.
I originally chose to design an Extra
because it’s one of the most neutral-flying
Scale precision airplanes available. By
neutral I mean that it reacts with pure
motion to the control inputs; rudder
imparts only yaw with no tendency to pitch
or roll, aileron roll is on axis, and throttle
does not affect altitude or heading. I don’t
know of any Scale models that are perfect,
but the Extra in general is as close as it
gets.
At the time of my initial research, no
manufacturers offered an Extra in the size
and with the 3-D capabilities I wanted.
Today, however, there are several good
choices for an Extra in sizes that are close
to this one. Two of the best designs
available are the 33% RadioCraft Extra and
the 31% and 33% Aeroworks Extras. All
excel in 3-D and in precision. Contact
information is at the end of this article.
Designed for Precision and 3-D: I chose
the two-seat L version over the single-seat
S model since it has tested to perform
slightly better in knife-edge flight because
of its more forward profile canopy.
Unfortunately that large canopy gives a
weight penalty, but the trade-off is worth
it.
Besides being a neutral and forgiving
aircraft for precision competition flying,
the Extra (when duly modified) is very
good at Freestyle 3-D flying, such as
torque rolling and harrier flight. This
airplane has been specifically designed to
take advantage of characteristics that make
it suitable for 3-D Freestyle and to keep it
as neutral as possible for competition. The
stabilizer has been lowered approximately
8% to reduce pitch coupling. The elevator
and rudder utilize the “X” experimental
design criteria (which were influenced in
the full-scale world by successes in the RC
arena) for more positive tumbling and 3-D
Freestyle maneuvers.
Some of the other design nuances are
for strength, longevity, and aesthetics
while trying to keep the airplane as light as
Flight photos by Michael Ramsey Construction photos by Mike Hurley Graphic Design by Carla Kunz
