23
BALANCE THE MODEL
This is probably the single most important step in preparing your
P-51B Mustang for flight. The final placement of the longitudinal
Center of Gravity, or Balance Point, is extremely important and
should be approached with patience and care.
Completely assemble the model, including propeller, spinner, etc.
Do not leave anything off the airplane that will be on it in flight. DO
NOT fill the fuel tank for balancing purposes. Some people prefer
to balance their airplanes by lifting the model up by one finger at
each wingtip to find the spot where the model will sit perfectly level.
This has been done for years and is an acceptable way to balance
a model. However, with an airplane as large as the MUSTANG, it
is virtually impossible to balance it by the wingtips by yourself. We
prefer balance to the Mustang in the upside down position, with
the measurements taken at the wing root right alongside each
fuselage side.
IMPORTANT NOTE: Balanced means the airplane sets perfectly
level when supported at the desired balance point - NOT slightly
nose down or nose up - PERFECTLY LEVEL!
BALANCE POINTS REFERENCE CHART
* Percentage of Mean Aerodynamic Chord
distance aft of wing
% of
leading edge measured
MAC*
along the fuselage side
27%
5.068"
28%
5.182"
29%
5.295"
30%
5.409"
31%
5.523"
32%
5.636"
33%
5.750"
For initial test flying we suggest a starting balance point of 5-3/8"
(5.375") behind the leading edge of the wing, with is approximately
of 30% MAC, measured along the fuselage side.
cut out, fold it carefully into a box shape, gluing together the
corners with the assembly tabs. Go slowly and make the folds
precisely on the lines, you will end up with a good looking result.
Touch up any white lines showing at the corner joints with
matching colored pens. Glue in the finished radio in place behind
the seat back.
Pilot: We used a Hangar 9 1/6-scale U.S. WWII Pilot #HAN8297
(not supplied) in our prototype MUSTANGS. Other brand pilots of
the same scale will also work.
As your experience with the P-51B Mustang increases, you can
adjust the balance point to suit yourself. In general, as the balance
point is moved aft the airplane will become more responsive and
less stable in all axis. Some pilots like their models extremely
reactive, while others like to fly with more smoothness. In the end,
the final balance point and control throws you use will depend
somewhat on how you like to fly.
The best means of shifting the CG fore or aft is by shifting the
location of the battery pack. It is the heaviest movable component
in the airplane. Wherever you put the battery pack, make sure it
cannot move around in flight. Our P-51B MUSTANG prototypes,
using either the Saito 91 and 100 4-strokes, required no additional
nose or tail weight to achieve different balance points. We shifted
the balance point by shifting the battery pack.
If moving your battery pack does not achieve the balance point you
want, and more weight is needed, consider using a larger (and
therefore heavier) battery pack.
Try to avoid adding useless
weight. If your model is nose heavy and battery shifting does not
work, you can try adding lead stick-on weights in the rear of the
fuselage. After you've determined how much tail weight you need,
the weights can be mounted inside the fuselage by simply
removing the elevator servo and gluing the weights securely inside
the fuselage. With the elevator servo back in place, the weights
willbe hidden.
INCIDENCE & THRUST ANGLES
For best results do not change the incidence or thrust angles of this
model - leave it alone! Your P-51B MUSTANG was factory built in
a jig to the following specifications. We are confident that it is built
within tolerance and will fly well.
These specs are given for
reference only, in case the airplane ever needs to be rebuilt. We
do not recommend that you alter the incidence and thrust angles
of your MUSTANG before test flying as built by the factory.
Wing Incidence:
+ .8°
Stab Incidence:
+1.5°
Engine - Down Thrust
- .5° down
Engine - Side Thrust
2° right