Great Planes Douglas DC-3 EP ARF - GPMA1155 - Manual (Page 17)

At this stage the model should be in ready-to-fly condition
with all of the systems in place including the motors, landing
gear, complete radio system, and 8-cell battery.
❏
1. Use a felt-tip pen or 1/8"-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 2-7/16" [62mm] back from the
leading edge of the wing.
❏
2. With the wing attached to the fuselage, all parts of the
model installed (ready to fly), 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” 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 Great Planes (GPMQ4485) “stick
on” lead. A good place to add stick-on nose weight is to the
inside of the nose section of the fuselage. Begin by placing
incrementally increasing amounts of weight on the bottom of
the fuse over the nose 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
and glued permanently inside the fuselage.
Note: Do not rely upon the adhesive on the back of the lead
weight to permanently hold it in place. 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.
❏
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 fin. 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.
No matter if you fly at an AMA sanctioned R/C club site or if
you fly 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 flying
sites and AMA sanctioned flying events. Fill out the
identification tag on the back cover and place it in your model.
Follow the battery charging instructions that came with your
radio control system to charge the batteries. You should
always charge your transmitter batteries the night before
you go flying and at other times as recommended by the
radio manufacturer.
Charge the Batteries
Identify Your Model
PREFLIGHT
Balance the Model Laterally
This is where your model should balance for the first
flights. Later, you may wish to experiment by shifting the
C.G. up to 2-5/16" [59mm] forward or 2-3/4" [70mm] back
to change the flying 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 difficult to slow for landing. Moving the C.G. aft
makes the model more maneuverable, but could also
cause it to become too difficult to control. In any case,
start at the recommended balance point and do not at
any time balance the model outside the specified range.
More than any other factor, the C.G. (balance point) can
have the greatest effect on how a model flies and may
determine whether or not your first flight will be
successful. If you value this model and wish to enjoy it for
many flights, DO NOT OVERLOOK THIS IMPORTANT
PROCEDURE. A model that is not properly balanced will
be unstable and possibly unflyable.
Balance the Model (C.G.)
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