.
A third approach makes use of the common adhesive-backed vinyl shelf paper available at hardware stores with a new
blade in a modeling knife, cut the color sweep on the T-34 version, for example, out of a piece of the shelf paper and use
the mask remaining for spraying or handpainting the decoration on the tail.
For models covered with plastic film, the fin flash could be cut from trim sheets. Or follow the manufacturer's directions that
come with the plastic film for applying this type of decoration.
Balancing
The King Kobra design, like the Kougar, requires a farther forward balance point
than commonly used on some other pattern style designs. Do not decide on the
basis of your experience with other models to ignore the following
recommendations and use some other balance point. Far too many modelers
build a kit, install the equipment and go out to test fly without ever checking out
the C.G. Don't do this!.
WHY MODELS MUST BE
INDIVIDUALLY BALANCED
It is impossible to produce a kit that
will automatically have the correct
Center of Gravity (C.G.) position.
Balsa wood varies in weight and it is
easily possible for wood in the tail to
be an ounce or more heavier or
lighter than average. One ounce of
extra weight in the tail has to be
countered by about 3 ounces in the
nose. Don't pile a lot of fillercoat or
finish, use excess glue or make
large fillets on the tail surfaces. The
motor you choose, whether or not a
muffler is fitted, the size and
placement of your radio equipment,
etc. all affect the balance. If you use
an unusually heavy motor or muffler
you may have to carry the battery in
the radio compartment instead of
the nose or even weight the tail.
Don't consider that whatever C.G.
the model builds out to as "good
enough". Check carefully and make
whatever adjustments that are
required. With the C.G. properly
located, a Sig design should fly with
only minor trim changes required.
BALANCING: Put a piece of masking tape on the bottom of the wing in the
center. Mark the distances from the leading edge (the wing-fuselage joint) on it. A
balancer can be made from a triangular architect's scale placed on a block high
enough to get the wheels clear of the bench. Shift the model back and forth on
the edge of the scale until the balance point is found. Balance with an empty fuel
tank but with all the other equipment installed and the model completely finished
and painted.
Our findings with 5 prototype models show that 1/2" behind the 25% point is as
far back as ever will be necessary. Under no circumstances should the C.G. be
moved farther back than the 33-1/3% point.
In addition to the fore and aft balancing
procedure described above, the
performance of manuevers is improved
if the model is also in balance spanwise.
For example, if one wing is heavy it may
affect turning and loop tracking. Inset
weight into the opposite wing tip to
correct this problem.
BALANCE IS PART OF THE TRIMMING PROCESS
The balance point we arrived at for this design is a good place to start when
trimming out the model for top performance. However, it should not be
considered the final and irrevocable location. Individual models built from the
same kit are slightly different from each other. The incidence may be
changed a bit, a small or large engine selected, the total weight varies - even
the skill of the pilot has bearing on just what should be the exact C.G. point.
For example, when slightly nose heavy, the model is more stable and less
likely to stall or snap roll from over-elevating. This also cuts down the
reaction of the model to control movements which is good during test and
practice flights to help prevent overcontrolling. But later, if extra sensitivity
and quick reactions are desired for aerobatic performance, a position farther
back may be desirable. So try different positions, but make the changes
gradually, checking results and the effect of the change control responses
and the performance of the model in the air at a good altitude.
Control Movements
The following control movements from
neutral were used on the prototype King
Kobras for test flights and are suggested
as a starting point. Your own trimming
and personal control reactions
preferences should then be applied to
determining the final measurements to
be used.