Great Planes Tracer 46 Kit - GPMA0400 - Manual (Page 43)

6. Immelmann Turn (U)
7. Split “S”
8. Three (3) Inside Loops (U)
9. One (1) Horizontal Roll (D)
10. Landing (U)
FLIGHT TRIMMING
Note: The following article has been reprinted in part for
future reference and also as a guide for your flight instructor
or experienced flying partner to help you with trimming your
model. If further information is required, please contact your
local hobby dealer, local flying club or call Great Planes at
(217) 398-8970.
A model is not a static object. Unlike a car, which you can
only hunt left or right on the road (technically, a car does
yaw in corners and pitches when the brakes are applied), a
plane moves through that fluid we call air in all directions
simultaneously. The plane may look like it’s going forward,
but it could also be yawing slightly, slipping a little and
simultaneously climbing or diving a bit! The controls
interact. Yaw can be a rudder problem, a lateral balance
problem or an aileron rigging problem. We must make many
flights, with minor changes between each, to isolate and
finally correct the problem.
The chart accompanying this article is intended to serve
as a handy field reference when trimming your model.
Laminate it in plastic and keep it in you flight box. You just
might have need to consult it at the next contest! The chart
is somewhat self-explanatory, but we will briefly run through
the salient points.
First, we are assuming that the model has been C.G.
balanced according to the manufacturer’s directions.
There’s nothing sacred about that spot — frankly, it only
reflects the balance point where a prototype model handled
the way the guy who designed it thought it should. If your
model’s wing has a degree more or less of incidence, then
the whole balance formula is incorrect for you. But, it’s a
good ballpark place to start.
The second assumption is that the model has been
balanced laterally. Wrap a strong string or monofilament
around the prop shaft behind the spinner, then tie the other
end to the tail wheel or to a screw driven into the bottom of
the aft fuse. Make the string into a bridle harness and
suspend the entire model inverted (yes, with the wing on!).
If the right wing always drops, sink some screws or lead
into the left wing tip, etc. You may be surprised to find out
how much lead is needed.
At this point the model is statically trimmed. It’s only a
starting point, so don’t be surprised if you wind up changing
it all. One other critical feature is that the ailerons must
have their hinge gap sealed. If shoving some Scotch tape
or MonoKote into the hinge gap to prevent the air from
slipping from the top of the wing to the bottom and vice-
versa, bothers you, then don’t do it.
To achieve the maximum lateral trim on the model, the
hinge gap on the ailerons should be sealed. The easiest
way to do this is to disconnect the aileron linkages and fold
the ailerons as far over the top of the wing as possible
(assuming they are top or center hinged). Apply a strip of
clear tape along the joint line. When the aileron is returned
to neutral, the tape will be invisible and the gap will be
effectively sealed. Depending on how big the ailerons are
and how large a gaping gap you normally leave when you
install hinges, you could experience a 20 percent increase
in aileron control response just by this simple measure.
Your first flights should be to ascertain control centering
and control feel. Does the elevator always come back to
neutral after a 180° turn or Split-S? Do the ailerons tend to
hunt a little after a rolling maneuver? Put the plane through
APPENDIX
43