Balance The Model (C; Balance The Model Laterally - GREAT PLANES Perfomance Series Sukhoi SU-31 1.60 ARF Instruction Manual

3D RATES
3D ELEVATOR 3-1/4" [83mm] up
3-1/4" [83mm] down
3D RUDDER 4-1/2" [114mm] right
4-1/2" [114mm] left
3D AILERONS 2-3/8" [60mm] up
2-3/8" [60mm] down
IMPORTANT: The Sukhoi SU-31 1.60 ARF has been
extensively fl own and tested to arrive at the throws at
which it fl ies best. Flying your model at these throws will
provide you with the greatest chance for successful fi rst
fl ights. If, after you have become accustomed to the way
the Sukhoi SU-31 1.60 ARF fl ies, you would like to change
the throws to suit your taste, that is fi ne. However, too much
control throw could make the model diffi cult to control, so
remember, "more is not always better."
Balance the Model (C.G.)
More than any other factor, the C.G. (balance point) can
have the greatest effect on how a model fl ies and may
determine whether or not your fi rst fl ight will be successful.
If you value this model and wish to enjoy it for many fl ights,
DO NOT OVERLOOK THIS IMPORTANT PROCEDURE.
A model that is not properly balanced will be unstable and
possibly unfl yable.
At this stage the model should be in ready-to-fl y condition
with all of the systems in place including the engine, landing
gear, covering and paint and the radio system.
❏
1. Use a felt-tip pen or 1/8" [3mm]-wide tape to accurately
mark the C.G. on the top of the wing on both sides of the fuse.
The C.G. is located 5-11/16" [144mm] back from the LE of the
wing at the fuse.
This is where your model should balance for the fi rst
fl ights. Later, you may wish to experiment by shifting the
C.G. up to 3/4" [19mm] forward or 3/4" [19mm] back to
change the fl ying characteristics. Moving the C.G. forward
may improve the smoothness and stability, but the model
may then require more speed for takeoff and make it more
diffi cult to slow for landing. Moving the C.G. aft makes
the model more maneuverable, but could also cause it to
become too diffi cult to control. In any case, start at the
recommended balance point and do not at any time
balance the model outside the specifi ed range.
❏
2. With the wing attached to the fuse, all parts of the
model installed (ready to fl y) and an empty fuel tank, place
the model upside-down on a Great Planes CG Machine, or
lift it upside-down at the balance point you marked. If you are
using a brushless motor, be sure to balance the airplane with
the battery pack installed.
❏
3. If the tail drops, the model is "tail heavy" and the
receiver battery pack and/or receiver must be shifted forward
or weight must be added to the nose to balance (also see
rudder servo installation section). If the nose drops, the
model is "nose heavy" and the receiver battery pack and/or
receiver must be shifted aft or weight must be added to the
tail to balance (also see rudder servo installation section). If
possible, relocate the battery pack and receiver to minimize or
eliminate any additional ballast required. If additional weight
is required, use Great Planes (GPMQ4485) "stick-on" lead.
A good place to add stick-on nose weight is to the fi rewall
(don't attach weight to the cowl–it is not intended to support
weight). Begin by placing incrementally increasing amounts
of weight on the bottom of the fuse over the fi rewall until the
model balances. Once you have determined the amount of
weight required, it can be permanently attached. If required,
tail weight may be added by cutting open the bottom of the
fuse and gluing it permanently inside.
Note: Do not rely upon the adhesive on the back of the lead
weight to permanently hold it in place. Over time, fuel and
exhaust residue may soften the adhesive and cause the
weight to fall off. Use #2 sheet metal screws, RTV silicone,
or epoxy to permanently hold the weight in place.
❏
4. IMPORTANT: If you found it necessary to add any weight,
recheck the C.G. after the weight has been installed.

Balance the Model Laterally

❏
1. With the wing level, have an assistant help you lift the
model by the engine propeller shaft and the bottom of the
fuse under the TE of the fi n. Do this several times.
❏
2. If one wing always drops when you lift the model, it means
that side is heavy. Balance the airplane by adding weight to the
other wing tip. An airplane that has been laterally balanced
will track better in loops and other maneuvers.
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