.
Power-Off Tests
A rubber-powered model is adjusted in
two steps. First, the tail surfaces are
adjusted to produce a good glide. Then
the propeller assembly is adjusted to
give a smooth, powered flight. Wait for a
calm day.
Begin by gliding the model from your hand into a patch of tall grass. Grasp the ship by the fuselage near the balance point, and
aim the nose at a spot on the ground about twenty feet in front of you. Launch the ship forward about the way you would a
paper dart airplane, nose down.
Your goal is a steady glide to the ground, moving at a CONSTANT SPEED, and travelling straight ahead or turning gently. You
will find the trick is to launch the model at its natural speed and glide angle. If the glide is poor, it can mean that the ship needs
adjustment or that you need more launching practice. So try several launches before deciding on adjustment changes. When
your ship acts the same way on each launch, you can be pretty sure that you are seeing its true characteristics, and not just a
poor launch.
Stalling
If your plane noses up, LOSES SPEED, and then falls clumsily or dives,
that is a STALL. To cure a stall, adjust the angle of the stabilizer by
changing the thickness of the incidence block under it. Lower the front
edge or raise the rear edge. See drawing. But make SMALL changes -
1/32" at a time. If a change of more than 1/16" is needed, go back and
perform the Preflight checks again. It's likely your Classic is incorrectly
balanced (tail-heavy) or the surfaces are warped.
Diving
A model that darts quickly into the ground without swooping or stalling,
is diving. The dive can be cured by adjusting the stabilizer in the
direction shown in figure 5 (in 1/32" steps). Here again, don't change
the height of the incidence block more than 1/16" without first re-
checking the Pre-flight steps. Warps or nose-heaviness may be causing
the dive.
Turning
A plane that glides in a straight line takes a lot of flying space and a lot of
chasing, so it's best to adjust the glide for a slight turn. The plans for your
model will tell which direction.
The size and direction of the glide circle can be controlled by adjusting the
fin. The drawing shows adjustment for a right turn. Moving the fin opposite,
of course, gives left turn.
Small changes in fin setting can be made by bending the surface. But if more than 1/32" or so of change is required, cut the fin
loose and re-cement it at the desired angle. When the glide is smooth and steady, you are ready to go on to powered tests.
Page 5 of 9
Sig Cabinaire SIGFF20 Instruction Manual
