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Balance the model (c.g.), Balance the model laterally, Preflight identify your model – Great Planes P-51 Mustang Sport Fighter .46 EP ARF - GPMA1208 User Manual

Page 22: Charge the batteries

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22

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, muffl er, propeller, spinner and pilot. If
you’ve built the electric version, install the motor battery. If
you’ve built the glow version the fuel tank should be empty.

1. If using a Great Planes C.G. Machine, set the rulers to

3-1/2" [89mm]. If not using a C.G. Machine, use a fi ne-point
felt tip pen to mark lines on the top of wing on both sides of
the fuselage 3-1/2" [89mm] 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. 1/4"
[6mm] forward or 1/4" [6mm] 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, or LiPo
batteries in place, 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 possible,

move the battery pack and/or receiver forward to get the
model to balance. If the nose drops, the model is “nose heavy.”

If possible, move the battery pack and/or receiver aft. If the
receiver and/or battery cannot be moved, or if additional
weight is still required, nose weight may be easily added
by using “spinner weight” (GPMQ4645 for the 1 oz. [28g]
weight, or GPMQ4646 for the 2 oz. [57g] weight). If spinner
weight is not practical or is not enough, or if tail weight is
required, use Great Planes “stick-on” lead (GPMQ4485). 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 the mounting screws to open up the holes in the cowl.
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: If mounting weight where it may be exposed to fuel
or exhaust, do not rely upon the adhesive on the back to
permanently hold it in place. Over time, fuel and exhaust
residue may soften the adhesive and cause the weight to fall
off. Instead, permanently attach the weight with glue or screws.

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.

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 the decal sheet 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.