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96 ST4000+ Wheel & Tiller Autopilots: Owner’s Handbook
6 Setting-up the ST4000+
Checking the rudder gain
The rudder gain level set at the factory will provide stable control for
initial sea trials. However, boats can vary widely in their response to
helm, and by adjusting the rudder gain you can improve the
autopilot’s steering characteristics.
Complete the following test to determine whether the rudder gain is
set too high or too low:
1. Sail your boat at cruising speed in clear water:
• you will find it easiest to recognize the steering response in
calm sea conditions where wave action does not mask basic
steering performance
2. Switch the autopilot to Auto, then make a 40°course change by
pressing the
-10 or +10 key four times:
• if the rudder gain is adjusted correctly, the 40° course change
should result in a crisp turn followed by an overshoot of no
more than 5°
• if the rudder gain setting is too high, the 40° course change
will result in a distinct overshoot of more than 5° (
A)
Correct this oversteer by reducing the rudder gain setting.
• if the rudder gain is too low, the boat’s performance will be
sluggish – it will take a long time to make the 40° turn and
there will be no overshoot (
B)
Correct this understeer by increasing the rudder gain setting.
New
heading
New
heading
A
New
heading
B
Correct
rudder gain
Rudder gain
too high
Rudder gain
too low
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