GREAT PLANES Super Sportster 90 Instruction Book page 44

crease the airplane speed at which flutter occurs.
Still have flutter? Then you must be ready for
the cure-all control surface static balance It's
not pretty, but it works every time What you
must do is move the center of mass of the control
surface Just in front of the hinge line If you do,
flutter will not occur at any airspeed There are
several ways to statically balance control sur-
faces Figure 1 shows functionally how to accom-
plish it, but there are many ways to implement it.
One of the problems of static balancing is that
you'll probably have the mechanism out in the
breeze where it will snag on things, although I
have seen some really neat static balancing Jobs
which were hidden inside the wing (Figure 2)
Figure 3 shows a straightforward way to bal-
SUPER SPORTSTER 90-120
METHOD FOR STATIC BALANCING ELEVATORS
PROVIDE CLEARANCE FOR
FULL "DOWN" ELEVATOR
2-56 Locking Nul
/-Ounce Fishing Weight
3/32"
(DRAWING IS ACTUAL SIZE)
Wheel Collar
ance a control surface using common materials.
It is recommended for ease of installation, struc-
tural integrity, and the ability to change weights.
What you must do is get the balance weight
large enough to cause the control surface to bare-
ly move up when it is released in the neutral
position (Don't forget to disconnect the servo
linkage first before you do this') Of course, it is
assumed that your control surface hinges are nice
and free so that the surface will flop down when
released if no balance weights are used Don't
overdo the static balancing of elevators, because
it can create another problem An overly bal-
anced elevator will tend to move Up in positive-G
maneuvers (like loops) This causes higher Gs,
which causes the elevator to move Up more,
which . . and so on.
(From Model Aviation , May, 1988 Reprinted by
permission)
1/16" Pushrod Wire
Threaded one end
44
Dubro No. 121
E-Z Connectors
IPeen-onI