.
Power-On Flight
ALL ADJUSTMENTS TO THE "WOUND UP" PART OF THE FLIGHT ARE MADE BY POINTING THE PROPELLER AND
NOSEBLOCK IN THE DIRECTION YOU WANT THE PLANE TO GO. This kind of adjustment affects only the powered flight,
and will not upset the glide pattern you have developed.
Now - wind the propeller 150 turns and launch your Classic into the wind
with the same motion you used in glide testing. The model should cruise
steadily forward, turning in the desired direction, and gaining or loosing
altitude gently.
If your ship tries to climb, but loses speed and stalls, point the propeller
downward by slipping a scrap of 1/32" balsa or a paper book match
between the top of the noseblock and the front of the fuselage. The wedge
is called a "shim" and the adjustment is called "downthrust". Downthrust is
illustrated in the drawing.
It's not likely that your plane will dive on first power flights, but if it should, put the shim at the bottom of the noseblock, tipping
the propeller upward (upthrust).
Downthrust is the "magic adjustment" that can make experts out of beginners. Learning to use it is the most important part of
your test program.
Increase or decrease the amount of downthrust (by changing the thickness of the shim behind the noseblock) until power flights
are smooth and free of stalling with 150 winds in the motor. Don't wind the motor any tighter until the lower-powered flights are
under control.
Power-On Turns
Because of the effects of the rotating propeller, models usually turn
better in one direction than the other. Your plans will say which way to
circle.
Don't circle any tighter than necessary. Circles smaller than about 50 ft.
diameter are tricky. If you have plenty of flying space, turns can be as
large as you like.
The drawing shows how side thrust is used to control power-on turning.
Making small changes, 1/32 at a time, adjust downthrust and sidethrust
together to produce smooth flights on 150 winds.
You may notice that turning to the right tends to hold the nose down-
right thrust acting a little like downthrust. If your plane begins to circle so
sharply that it loses altitude in a steep bank, reduce the amount of
sidethrust until the turn opens up to a safer size.
Longer, Higher Flights
When your Classic is flying smoothly with 150 turns in the motor, wind to 175 and try it. Make any necessary noseblock
adjustments, and then wind to 200, and so on. The safe number of turns that your motor will stand is shown below.
Rubber Motor Winding Chart
Length of Loop 1/4"
10
11
12
13
14
15
16
Safe Number of Turns
Hand Wound
180 200 220 235 250 270 290
Stretch Wound 440 485 525 570 615 660 700
A plane's weight determines how much power it needs. If your ship is huskier than average, it may not climb, even when fully
wound. In that case, add one strand (not a complete loop) of 1/8" Sig rubber to the motor. Tie an eye (like a slip knot) in each
end. This will provide the extra horse power needed for higher climb.
Page 6 of 9
Sig Cabinaire SIGFF20 Instruction Manual
