Raymarine ST70 Instrument, Installation Manual

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52 ST70+ User Reference Manual
Checking rudder gain
To determine whether the rudder gain is set correctly, carry out the following test:
1. Ensure you have set the autopilot response to level
5 , as described above.
2. Motor your boat at a typical cruising speed in clear water.
It is easier to recognize the steering response in calm sea conditions where wave
action does not mask steering performance.
3. Press
AUTO
to enter Auto mode, then alter course by 40°:
• This course change should result in a crisp turn followed by an overshoot of no
more than 5°, If the rudder gain is adjusted correctly.
• If the course change causes a distinct overshoot (more than 5°) and/or there is
a distinct ‘S’ in the course (as at
A
in Figure 3-3 ), the rudder gain is too high.
• If the boat’s performance is sluggish and it takes a long time to make the 40°
turn, with no overshoot (as at
B
in Figure 3-3 ), the rudder gain is too low.
Figure 3-3: The affect of different rudder gain values
If necessary, use the Setting rudder gain procedure in the ST70+ User Reference
Manual , to improve autopilot performance.
Checking counter rudder
To check the counter rudder setting:
1. Ensure you have set the response to level
5 , as described above.
2. Motor your boat at cruising speed in clear water.
3. Press
AUTO
to switch the autopilot to Auto mode, then make a 90° course change:
• When rudder gain and counter rudder are both set correctly, the boat performs
a smooth continuous turn with minimal overshoot.
• If the counter rudder is too low, the boat will still overshoot.
• If counter rudder is too high, the boat will ‘fight’ the turn and make a series of
short, sharp turns: this results in a very ‘mechanical’ feel as the boat changes
course.
New
heading
Correct
rudder gain
D11622-1
New
heading
B
Rudder gain
too low
New
heading
A
Rudder gain
too high
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