Note:
The throws are measured at the
widest part
of the
elevators and ailerons.
At this stage the model should be in ready-to-fly condition
with all of the systems in place including the engine, landing
gear, covering and paint, 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
fuselage. The C.G. is located 2-1/4" [57mm] back from the
leading edge of the wing at the fuselage.
❏
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 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. 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 (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 P-51 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 P-51 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
AILERONS:
5/16" [8mm] up
1/4" [6mm] up
5/16" [8mm] down
1/4" [6mm] down
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