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, 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
3-15/16” [100mm] back from the leading edge of the
wing at the fuselage side.
❏
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. [28g] weight, or
GPMQ4646 for the 2 oz. [56g] 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.
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 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 weight to the other wing tip.
An
airplane that has been laterally balanced will track
better in loops and other maneuvers.
This is where your model should balance for the
first flights. Later, you may wish to experiment by
shifting the C.G. up to 1/4” [6mm] 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.
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