Great Planes Spitfire 25 GP/EP ARF - GPMA1478 - Manual (Page 26)

Note: The throws are measured at the widest part of the
elevators, rudder and ailerons.
At this stage the model should be in ready-to-fly 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), but with no fuel.
❏
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 2-3/8" [60mm] back from the LE of
the wing where it meets the fuselage.
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2. With the wing attached to the fuse, all parts of the
model installed (ready to fly) and an empty fuel tank, 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 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 firewall (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 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
fuse 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.
This is where your model should balance for the first
flights. Later, you may wish to experiment by shifting the
C.G. up to 1/8" [3mm] forward or 1/8" [3mm] 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.)
IMPORTANT: The Combat Spitfire ARF has been
extensively flown and tested to arrive at the throws at
which it flies best. Flying your model at these throws will
provide you with the greatest chance for successful first
flights. If, after you have become accustomed to the way
the Combat Spitfire ARF flies, you would like to change
the throws to suit your taste, that is fine. However, too
much control throw could make the model difficult to
control, so remember, “more is not always better.”
These are the recommended control surface throws:
High Rate Low Rate
ELEVATOR: 3/8" [9.5mm] up 1/4" [6mm] up
3/8" [9.5mm] down 1/4" [6mm] down
RUDDER: 3/4" [19mm] right 1/2" [13mm] right
3/4" [19mm] left 1/2" [13mm] left
AILERONS: 3/16" [5mm] up 1/8" [3mm] up
3/16" [5mm] down 1/8" [3mm] down
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