Raymarine Autohelm ST7000 Installation Instructions Manual - page 45
To ensure precise course adjustments the sea
state control is automatically reset whenever a 10
deg. course change is selected.
Level 2
-
Automatic Sea State Inhibit
Where increased course keeping accuracy is
required the automatic sea state control can be
inhibited by moving to response level 2.
Autopilot activity and therefore power
consumption will be increased.
Level 3
-
Automatic Sea State Inhibit
- Counter Rudder
Where maximum course keeping accuracy is
required move to response level 3. This
introduces counter rudder (rate) to increase @e
natural damping of the vessel. On power craft
level 3 is useful at slow speed where the natural
damping of the vessel is reduced. Autopilot
activity and therefore power consumption will be
at a maximum.
The minimum response level necessary to
achieve the desired course keeping should be
used to reduce power consumption and autopilot
wear and tear.
5.4 Automatic Trim Control
The ST7000 automatically corrects for trim. No
adjustment of the pilot is necessary.
After each course change the Automatic Trim is
cancelled and the ST7000 will re-establish the
correct trim for the new heading. It should be
noted that if a large course change is keyed in
(greater than 60 deg.) the autopilot will not
assume the final selected course immediately.
The vessel will come to within say 10 deg. of the
desired course and will only settle onto course
when the Automatic Trim has been full
established. This may take up to two minutes.
It is recommended the following procedure is
adopted for large course changes.
•
Note required new heading.
•
Select
Stand by
and steer manually.
•
Bring vessel onto new heading.
•
Select
Auto
and let vessel settle onto course.
•
Bring to final course with 1 deg. course
change increments.
It is sound seamanship to make major course
changes only whilst steering manually. In this way
any obstructions or other vessels may be cleared
properly and due account taken of the changed
wind and sea conditions on the new heading prior
to engaging the autopilot.
Important Note
If the automatic trim control is switched off (see
section 4.3), regular checks on the vessels
heading should be made as changes in standing
helm will change the course steered by the
autopilot.
5.5 Rudder Gain Adjustment
(Displacement Craft)
The rudder gain level recommended in Section
4.1 will provide stable control for initial sea trials.
However, vessels can vary widely in their
response to the helm, and further adjustment to
the rudder gain may improve the autopilots
steering characteristics. Setting up rudder gain
should be carried out with Response level 1.
An excessively high rudder control setting results
in
oversteer
which can be recognised by the
vessel swinging from side to side of the automatic
heading accompanied by excessive rudder
movement. In addition, distinct overshoot will be
observed when the course is changed. This
condition can be corrected by reducing the rudder
setting.
Similarly, an insufficient rudder control setting
results in
understeer
which gives sluggish
steering performance and is particularly apparent
when changing course. This is corrected by
increasing the rudder setting. These tendencies
are most easily recognised in calm sea conditions
where wave action does not mask basic steering
performance. The rudder control setting is not
over critical and should be set to the lowest setting
consistent with accurate course keeping. This will
minimise actuator movements and hence reduce
power consumption and wear and tear generally.
Typically if at cruising speed a course change of
40 deg. results in an overshoot of between 2 and
5 deg., the rudder gain is correctly adjusted.
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