Great Planes Cirrus SR22 .46-55 ARF - GPMA1363 - Manual (Page 27)

27
Balance the Model (C.G.)
More than any other factor, the C.G. (center of gravity/
balance point) can have the greatest effect on how a model
fl ies and could determine whether or not your fi rst fl ight will
be successful. If you value your model and wish to enjoy it
for many fl ights, DO NOT OVERLOOK THIS IMPORTANT
PROCEDURE. A model that is not properly balanced may
be unstable and possibly unfl yable.
At this stage the model should be in ready-to-fl y condition
with all of the components in place including the complete
radio system, engine or motor, muffl er, propeller, spinner
and pilot. The fuel tank should be empty or on the electric
powered version, the motor battery should be installed.
❏
1. If using a Great Planes C.G. Machine, set the rulers to
2-1/4" [57mm]. If not using a C.G. Machine, use a fi ne-point
felt tip pen to mark lines on the top of the wing on both sides of
the fuselage 2-1/4" [57mm] back from the leading edge. Apply
narrow (1/16" [2mm]) strips of tape over the lines so you will
be able to feel them when lifting the model with your fi ngers.
This is where your model should balance for the fi rst
fl ights. Later, you may experiment by shifting the C.G. 1/8"
[3mm] forward or 1/8" [3mm] back to change the fl ying
characteristics. Moving the C.G. forward will improve the
smoothness and stability, but the model will then be less
aerobatic (which may be fi ne for less-experienced pilots).
Moving the C.G. aft makes the model more maneuverable
and aerobatic for experienced pilots. 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 fuselage, 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.
❏
3. If the tail drops, the model is “tail heavy.” If the nose
drops, the model is “nose heavy.” Use Great Planes “stick-on”
lead (GPMQ4485) to balance the plane. To fi nd out how
much weight is required, place incrementally increasing
amounts of weight on the bottom of the fuselage over the
location where it would be mounted inside until the model
balances. A good place to add stick-on nose weight is to the
fi rewall. Do not attach weight to the cowl—this will cause
stress on the cowl and could cause the cowl to crack at the
screw holes. Once you have determined if additional weight
needs to be installed, it can be permanently attached.
Do not rely upon the adhesive on the back of the lead weight
to permanently hold it in place. Over time, fuel, vibration and
exhaust residue may soften the adhesive and cause the
weight to fall off. Instead, permanently attach the weight with
glue or screws.
Note: On the electric powered version move the motor
battery forward or aft before adding additional weight to
the nose or tail.
❏
4. IMPORTANT: If you found it necessary to add any
weight, recheck the C.G. after the weight has been installed.
PREFLIGHT
Identify Your Model
No matter if you fl y at an AMA sanctioned R/C club site or if
you fl y somewhere on your own, you should always have your
name, address, telephone number and AMA number on or
inside your model. It is required at all AMA R/C club fl ying sites
and AMA sanctioned fl ying events. Fill out the identifi cation tag
on page 30 and place it on or inside your model.
Charge the Batteries
Follow the battery charging instructions that came with your
radio control system to charge the batteries. You should
always charge your transmitter and receiver batteries
the night before you go fl ying, and at other times as
recommended by the radio manufacturer.