Instruction manual

Balance the Model (C.G.)
At this stage the model should be in ready-to-fly condition
with all of the systems in place including the engine,
landing gear, and the radio system.
❍ 1. Use a felt-tip pen or 1/8”-wide tape to accurately mark
the C.G. on the bottom of the wing on both sides of the
fuselage. The C.G. is located 3-1/2“ [89 mm] back from the
leading edge of the wing. This is where your model should
balance for your first flights. Later, you may wish to
experiment by shifting the C.G. up to 1/4” [6 mm] forward
or 1/4” [6 mm] back to change the flying characteristics.
Moving the C.G. forward may improve the smoothness and
stability, but it 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 for you to control. In any
case, start at the location we recommend and do not at any
time balance your model outside the recommended range.
❍ 2. With the wing attached to the fuselage, all parts of the
model installed (ready to fly) and an empty fuel tank, place
the model on a Great Planes CG Machine (GPMR2400),
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 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 to the rear 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. weight, or GPMQ4646 for
the 2 oz. 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 firewall.
Begin by placing incrementally increasing amounts of
weight on the fuselage over the firewall 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.
❍ 4. IMPORTANT: If you found it necessary to add any
weight, recheck the C.G. after the weight has been installed.
Also, if you found it necessary to move any radio components
make sure they are securely reinstalled inside the fuselage.
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
fuselage 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
the necessary amount of stick-on weight to the other wing
tip. An airplane that has been laterally balanced will
track better in loops and other maneuvers.
More than any other factor, the C.G. (center of gravity or,
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.
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