SOMETHIN’ EXTRA
®
ARF ASSEMBLY MANUAL
INTRODUCTION:
Congratulations on your purchase of the fantastic new SIG
SOMETHIN' EXTRA
®
ARF kit. SIG's kit version of this unique
design has proven to be one of the most popular sport aerobatic
R/C models ever produced. Reasons for this popularity with
modelers are many but certainly one of the most important has
been the consistently outstanding flying characteristics of the
design. This new ARF version of the SOMETHIN' EXTRA
®
retains
all of these attributes and offers modelers an even quicker way to
get into the air with a very high-performance airplane!
Like the kit version, the ARF SOMETHIN' EXTRA
®
is built light and
strong for best performance. Using fixture construction, this ARF
has been built to virtual perfection, assuring you of a truly straight
airplane. This means that it will fly straight, the way it was meant
to. The covering has been professionally applied and the trim
scheme is completely unique to the airplane. This trim scheme
offers superb visibility in any attitude. In terms of flying
capabilities, there just aren't many designs that have the huge
flight envelope of the SOMETHIN' EXTRA
®
. Depending upon your
flying skills, the SOMETHIN' EXTRA
®
is capable of just about any
maneuver you can think of and probably a few that never crossed
your mind.
The design of this airplane has been well thought-out and also well
proven. For example, the tail braces are there for a reason. This
airplane is capable of extremely quick rolls and snap maneuvers
and the tail brace system keeps those forces off of the tail group -
they are needed! The two-piece wing allows easy disassembly
and transportation in the smallest of vehicles. The method
employed to retain the wing panels to the fuselage is simple,
strong and very easy to work with.
Finally, we urge you to read this manual completely. Familiarize
yourself with the parts and their assembly sequences. The
successful assembly and flying of this airplane is your
responsibility. If you deviate from these instructions, you may
wind-up with problems later on. We would also like to point out that
this airplane is not suitable for beginners. The performance of this
airplane is beyond the capabilities of beginning pilots. You should
have good experience with low-wing, aileron equipped R/C
models before flying this airplane.
RADIO EQUIPMENT:
The SOMETHIN' EXTRA
®
ARF can be flown with typical 4-
channel radios and five standard servos. You will need an aileron
"Y" harness to connect the ailerons to the receiver's single aileron
channel. You will also likely need a couple of 6" servo extension
cables for the wing mounted aileron servos.
However, the real potential of the SOMETHIN' EXTRA
®
ARF can
be realized by using one of today's inexpensive computer radio
systems, such as the Hitec Flash 5X or the Airtronics
®
RD-6000.
These radio systems allow you to "fine-tune" your control surfaces
to exactly your style of flying. In addition, you'll be able to set-up
the ailerons to act as flaperons, which can lend a whole new
dimension to your flight routines! Using such radios, you will not
need a Y-harness for the aileron connections.
ENGINES, PROPELLERS, AND MUFFLERS:
As stated earlier, over-powering the SOMETHIN' EXTRA
®
ARF is
totally unnecessary and counter-productive to achieving the C.G.
without the need for lead weights. This design is not about speed.
Aerodynamically, the SOMETHIN' EXTRA
®
is not a particularly fast
airplane. It's been designed to fly at moderate speeds at the high
end, with incredible low speed capability. To take full advantage of
the design, you should use powerful, bearing equipped 2-stroke
engines in the .40 - .46 range. We have tested this airplane using
the Irvine .40, .46, and the .53 engines. Any one of these
powerplants flies the SOMETHIN' EXTRA
®
beautifully. What is
especially nice about Irvine engines is their great power, truly
linear throttle response, and their extremely efficient mufflers. We
suggest you to give serious thought to the engine you intend to use
for this airplane. A marginal engine will always yield marginal
results.
When using 2-stroke engines, avoid heavily pitched props. Ideally
you want your engine pulling as well vertically as it does in
horizontal flight. To do this, it needs to operate at or about its best
rpm level to take advantage of its power curve.
For 4-stroke engines, we suggest displacement sizes up to .65.
Using engines larger than this will likely give you weight and
balance problems, along with the realities of propeller clearance.
Another important thing to remember is that typical 4-stroke
engines have their throttle arms usually located differently than
throttle arms on 2-stroke engines. If you want to power this model
with a 4-stroke engine, you will likely have to install a new,
relocated throttle cable tube. While this is not difficult, it is
something to consider when choosing an engine.
No matter what engine you choose always use an effective
muffler! A loud engine could cost you (and possibly your club) the
use of your flying site if it offends nearby non-modeling neighbors.
Use the muffler that came with your engine or an after-market
muffler made especially to quiet two-stroke engines.
COVERING MATERIAL:
Your SOMETHIN' EXTRA
®
ARF has been professionally covered
using AeroKote
™
. This material is known for its ease of
application, light weight and consistency of color. If you live in a
dry climate, you may notice that some wrinkles may develop after
removing the covered parts from their plastic bags. This is
perfectly normal in low humidity climates. Your model was built and
covered in a part of the world, which has relatively high humidity
and therefore, the wood was likely carrying a fair amount of
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