Seiwa SW AP03 User Manual

Page 9

UNDERSTEER

REFERENCE
COURSE

OVERSTEER

Figure 1.2. Illustration of oversteer if the rudder factor is set too high and understeer if it is

set too low.

Sea State (Manual)

The SEA STATE setting is influenced by the sea conditions and the weight of the vessel.
The NORMAL applies helm in proportion to the course error and the rate of turn. The
ROUGH mode is used when the vessel rolls and yaws in a heavy sea. Rudder activity is
quietened down by not reacting to small heading shifts, but full control is applied as the shift
becomes larger. The rate of turn component in the helm correction is adjustable and is
important for vessels whose helm response is slow and/or continue to turn for some time
after helm is removed. When there is a turn-rate (or counter rudder) component, normal
helm is applied to start the vessel turning. As the turn rate builds up, the helm is backed off.
When the vessel is close to the reference course, reverse helm or counter-rudder is applied
to stop the turn.

The action of the rate or counter-rudder during a turn is illustrated in Fig 1.3. Generally,
when the rate component is increased, vessels hold a course better but react to changes in
the reference course more slowly. Counter-rudder also improves control for most vessels
operating in a following sea.