21
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 motor, landing
gear, battery pack, 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 2-3/4" [70mm] 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 1/2" [13mm] forward or 3/8" [9.5mm] 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 all parts of the model installed (ready to fl y) and the
battery pack installed, place the model upside-down on a Great
Planes C.G. Machine, or lift it 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 to balance. If the nose
drops, the model is “nose heavy” and the battery pack and/
or receiver must be shifted aft to balance. If possible, move
the battery pack and receiver to minimize or eliminate any
additional ballast required. An additional aft battery tray is
included to help balance the model when nose heavy by
moving the battery pack further aft. Epoxy the tray in place
as shown if necessary.
❏
4. IMPORTANT: If you found it necessary to move the
battery pack or receiver for the Extra to balance, recheck the
C.G. after this has been done.
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 page 24 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 battery the night before you go fl ying, and
at other times as recommended by the radio manufacturer.
