Trimming Your Model

TRIM FEATURE MANOEUVRES OBSERVATIONS CORRECTIONS
CONTROL CENTERING Fly general circles and random manoeuvers. Try for hands off straight and level flight. Readjust linkages so that Tx trims are centered.
CONTROL THROWS Random manoeuvers A. Too sensitive, jerky controls.B. Not sufficient control If A, change linkages to reduce throws.
If B, increase throws.
ENGINE THRUST ANGLE
(see note 1)
From straight flight, chop throttle quickly. A. Aircraft continues level path for short distance.
B. Plane pitches nose up.
C. Plane pitches nose down.
If A, trim is OK.If B, decrease downthrust
If C, increase downthrust.
CENTRE OF GRAVITY
LONGITUDINAL BALANCE
From level flight, roll to 45 degree bank and neutralise controls. A. Continues in bank for moderate distance.
B. Nose pitches up.
C. Nose drops.
If A, trim is good.If B, add nose weight.
If C, remove nose weight.
SPLIT ELEVATORS
(Also Yaw and C of G)
Into wind, pull open loops using only elevator. Repeat tests doing outside loops to inverted entry. A. Wings are level throughout.
B. Plane tends toward outside when right side up, and to inside when inverted.
C. Plane goes in on regular loops, and out on inverted.
D. Plane goes out on both types of loops.
E. Plane goes in on both types of loops.
If A, trim is fine.
If B, add weight to right wing, or add right rudder.If C, add weight to left wing, or add left rudder.
If D, raise right half of elevator (or lower left).
If E, raise left half of elevator (or lower right).
YAW
(see note 2)
Into wind, do open loops, using only elevator.
Repeat tests doing outside loops to inverted entry.
A. Wings are level throughout.
B. Yaws to right in both inside and outside loops.
C. Yaws to left in both inside and outside loops.
D. Yaws right on insides, and left on outside loops.
E. Yaws left on insides, and right on outside loops.
If A, trim is correct.
If B, add left rudder trim.If C, add right rudder trim.If D, add left aileron trim.

If E, add right aileron trim.

LATERAL BALANCE Into wind, do tight inside loops, or make straight up climbs into Hammerheads. Do same from inverted entry. A. wings are level and plane falls to either side randomly in Hammerhead.
B. Falls off to left in both inside and outside loops. Worsens as loops tighten.
C. Falls off to right in both loops. Worsens as loops tighten.
D. Falls off in opposite directions on inside and outside loops.
If A, trim is correct.
If B, add weight to right wing tip.If C, add weight to left wing tip.
If D, change aileron trim.
(see note 3)
AILERON RIGGING With wings level, pull to vertical climb and neutralise controls. A. Climb continues along same path.
B. Nose tends to go to inside loop.
C. Nose tends to go to outside loop.
If A, trim is correct.If B, raise both ailerons very slightly.
If C, lower both ailerons very slightly.
WING INCIDENCE Knife edge flight. A. Model tends to veer in nose up direction.
B. Model veers in nose down direction.
If A, reduce wing incidence.
If B, increase wing incidence.

 

NOTES

1. Engine thrust angle and CG interact. Check both.

2. Yaw and lateral balance produce similar symptoms. Note that fin may be crooked. Right and left references are from the plane’s vantage point.

3. Ailerons cannot always be trimmed without sealing the hinge gap.

 

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