36
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).
❏
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 5-13/16" [148mm] 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 11/16" [17.5mm] forward or 11/16" [17.5mm] 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 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.
❏
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.
❏
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 center template page 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.
CAUTION:
Unless the instructions that came with your
radio system state differently, the
initial
charge on
new
transmitter and receiver batteries should be done for 15
hours
using the slow-charger that came with the radio
system
. This will “condition” the batteries so that the next
charge may be done using the fast-charger of your choice.
If the initial charge is done with a fast-charger the batteries
may not reach their full capacity and you may be fl ying with
batteries that are only partially charged.
