Simrad NSS12 Installation Manual page 49

If the value is set too high the overshoot will increase and the steering will be
unstable.
Counter rudder
Counter rudder is the amount of rudder used to try to prevent the boat from yawing
around the set course. Higher counter rudder settings result in more rudder being
applied.
The best way of checking the value of the Counter rudder setting is when making
turns.
The fi gures illustrate the eff ects of various Counter Rudder settings;
A: Counter rudder too low; overshoot response
B: Counter rudder too high; sluggish and creeping response
C: Correct setting or counter rudder; ideal response
A B C
Auto trim
This parameter defi nes how fast the autopilot shall correspond after having registered
a heading error.
The standard value is 40 seconds which should work well on most boats. Rule of
thumb: Set to same value (seconds) as the boat's length in feet. On boats operating
on VRF the value should be set to 20 seconds.
Rate limit
Sets the maximum allowed rate of turn.
The value should be kept at 6.0°/second unless there is a need for more rapid
response in turns.
Minimum rudder
This parameter fi lters small rudder commands to prevent high rudder activity.
Some boats may have a tendency to not respond to small rudder commands around
the "course keeping" position because of a small rudder, a rudder deadband, whirls/
disturbance of the water-stream passing the rudder or it is a single nozzle water jet
boat.
By increasing the Minimum rudder parameter you may improve the course keeping
performance on some boats. This will however increase the rudder activity.
Minimum wind angle to port and starboard
These parameters should be set identical to the minimum apparent wind angle that
will keep the sails well shaped and give an acceptable thrust. The parameters will vary
from boat to boat.
The settings are used for the tack-prevent function. They also applies when the autopi-
Operating the autopilot
lot is operating in WindNAV mode. Refer to the section.
You can select diff erent minimum wind angles for port and starboard. The diff erence
between port and starboard will be taken into account when calculating the Distance
To Turn (DTT).
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Autopilot | NSS Installation Manual