Great Planes Extra 300S 40 Kit - GPMA0235 - Manual (Page 42)

NOTE: The balance and control throws for the Extra 300
have been extensively tested. This chart indicates the
settings at which the Extra 300 flies best. Please set up
your model to the specifications listed above. If, after
you become comfortable with your Extra 300, you would
like to adjust the throws to suit your tastes, that's fine.
Too much throw can force the plane into a stall or snap
roll, so remember, “more is not better.”
NOTE: This section is VERY important and must NOT
be omitted! A model that is not properly balanced will
be unstable and possibly unflyable.
❏
1. Accurately mark the balance point on the top of the
wing on both sides of the fuselage. Use thin strips of tape
or a felt-tip pen to make the marks. The balance point (CG)
is located 4" back from the leading edge and next to the
fuse sides as shown in the sketch and on the fuselage plan.
Hint: Reference the full size fuse plan to help you locate the
proper balance point. This is the balance point at which your
model should balance for your first flights. After initial trim
flights and when you become more acquainted with your
Extra 300, you may wish to experiment by shifting the
balance up to 1/4" forward or back to change the flying
characteristics. Moving the balance forward may improve the
smoothness and stability but the model may then require
more speed for takeoff and may become more difficult to
slow for landing. Moving the balance aft makes the model
more agile with a lighter, snappier “feel” and often improves
knife-edge capabilities. In any case, please 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, hold
the model upsidedown with the stabilizer level.
❏
3. Lift the model at the balance point. If the tail drops
when you lift, the model is “tail heavy” and you must add
weight* to the nose to balance the model. If the nose
drops, it is “nose heavy” and you must add weight* to the
tail to balance the model.
NOTE: Nose weight may be easily installed by using a
“spinner weight” or gluing lead weights to the firewall. Tail
weight may be added by using Great Planes (GPMQ4485)
“stick-on” lead weights. Later if the balance is O.K., you can
open the fuse bottom and glue the weights in permanently.
* If possible, first attempt to balance the model by changing
the position of the receiver battery and receiver. If you are
unable to obtain good balance by doing so, then it will be
necessary to add weight to the nose or tail to achieve the
proper balance point.
Follow the battery charging procedures in your radio
instruction manual. You should always charge your transmitter
and receiver batteries the night before you go flying and at
other times as recommended by the radio manufacturer.
Charge the Batteries
At this time check all connections including servo arm
screws, faslinks, clevises and servo cords. Make sure
you have installed the nylon retainer on the Screw-Lock
Pushrod Connector on the throttle pushrod at the servo
arm and the silicone retainers on all the clevises.
PREFLIGHT
Balance Your Model
The throws are measured at the widest part of the
elevators, rudder and ailerons. Adjust the position of the
pushrods at the control/servo horns to control the
amount of throw. You may also use the ATV's if your
transmitter has them but the mechanical linkages should
still be set so the ATV's are near 100% for the best servo
resolution (smoothest, most proportional movement).
Do not exceed the elevator throws provided.
We recommend the following control surface throws:
High Rate Low Rate
ELEVATOR: 5/16" up 1/4" up
3/8" down 5/16" down
RUDDER: 2-1/8" right 1-1/2" right
2-1/8" left 1-1/2" left
AILERONS: 3/8" up 1/4" up
3/8" down 1/4" down
NOTE: If your radio does not have dual rates, then set
the control surfaces to move between the high rate and
low rate throws.
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