4.2 RUDDER CONTROL ADJUSTMENT
The gain control switch on the course computer
should have been set according to the
recommendation given in section
This
control sets the range of adjustment available on
the control unit rudder control switch and
normally will not need further adjustment.
Excessive rudder application results in
‘oversteer’ which can be recognised by the vessel
swinging slowly from side to side of the automatic
heading. In addition, distinct overshoot will be
observed when the course is changed. This
condition can be corrected by reducing the
rudder control setting.
Similarly, insufficient rudder application results
in sluggish steering performance which is
particularly apparent when changing course. This
is corrected by increasing the rudder control
setting.
Oversteer and understeer tendencies are most
easily recognised in calm sea conditions where
action does not mask basic steering
performance.
The rudder control adjustment should be
tested by steering the vessel onto a southerly
course (N. hemisphere). With the pilot engaged
and the rudder control on the
control unit
at
minimum there should be no course wandering.
Increasing the rudder control to maximum
should not induce course wandering.
Repeat the check on a northerly heading (N.
hemisphere). At minimum rudder control setting
there should be no major course wandering.
As maximum rudder control is reached the
may wander and the pilot become
Reducing the rudder control to near
should return the pilot the normal
accuracy.
If the pilot is
unstable
on northerly heading
at
minimum
rudder control setting
reduce
the gain control switch at the
course
computer
by
one
division and repeat the
test.
l
If the pilot is
stable
on northerly headings at
maximum
rudder control setting. increase
the
control switch at the
course
computer
by
one
division and repeat the
test.
NOTE: IN SOUTHERN HEMISPHERE READ
NORTH FOR SOUTH IN THE ABOVE TESTS.
Planing Craft
Planing craft operate over a wide speed range.
Rudder effectiveness increases significantly at
high hull speeds and it is always necessary to
reduce the rudder control setting as speed
increases to avoid oversteer. The rudder control
setting would normally be reduced to minimum at
maximum planing speed and increased towards
maximum at minimum displacement speeds.
Oversteer can be extremely violent at planing
speeds and it is thus essential to reduce the
rudder setting before opening the throttle.
Displacement Power Vessels
The rudder control setting is much less critical on
this type of vessel, and it is normally unnecessary
to change the setting at different engine speeds.
As a general guide, initial testing should be
carried out at mid-setting and reduced as much
as possible consistent with good heading control
to minimise wear and tear on the steering system.
Sailing Craft
Mono-hull sailing craft average hull speeds do
not vary greatly and thus the rudder control
setting will normally remain fixed most of the time.
Initial testing should be carried out at
setting.
Sailing craft are particularly stable when sailing
close hauled and under these conditions, it is
usually possible to reduce the rudder control
setting to minimise rudder movement and hence
power consumption. Conversely, when sailing
down wind, stability is least and improved course
holding will result by increasing the rudder
setting. When running down wind in high wind
velocities and in breaking sea conditions,
instantaneous hull speeds when descending
breaking seas can be extremely high. Under these
conditions course heading can sometimes be
improved by
reducing
the rudder control setting.
The optimum range of adjustment is easily found
by experiment.
Semi-Planning Power Vessels
Some types of semi planning power craft may
display significant changes in-steering
characteristics with speed change. It may be
necessary to
increase
the rudder control when
reducing hull speed.
The adjustment technique for the rudder
control varies significantly between planing and
displacement craft as described on the next
