Balance The Model (C.g.); Balance The Model Laterally; Preflight; Identify Your Model - GREAT PLANES U-Can-Do SF Instruction Manual

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3. Measure and set the low rate elevator throws and the
high and low rate throws for the rest of the control surfaces
the same way.

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 or brushless
motor, landing gear, and the radio system (and battery pack
if applicable).
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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
fuselage. The C.G. is located 5-1/2" [140 mm] back from the
leading edge of the wing.
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 1" [25 mm] forward or 3/4" [19 mm] 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.
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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 on a Great Planes CG Machine upside down, or
lift it at the balance point you marked.
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3. If the tail drops, the model is "tail heavy" and the battery
pack and/or receiver must be shifted forward or weight must
be added to the nose to balance. If the nose drops, the model
is "nose heavy" and the battery pack and/or receiver must be
shifted aft or weight must be added to the tail to balance. If
possible, relocate the battery pack and receiver to minimize or
eliminate any additional ballast required. If additional weight is
required, nose weight may be easily added by using a "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, 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
fuselage 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.
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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

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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.
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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 page 32 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.
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