Seiwa SW AP03 - Manual (Page 28)

The Rudder Factor is set according to the responsiveness of the steering. Yachts and
power boats from 6 to 15 m in length, generally have responsive steering and a rudder
factor setting of 3 or 4 is suitable. For high speed planing hulls, a setting of 2 to 3 should
give better control. Vessels above 15 m length normally have less responsive steering and
a good rudder factor setting is in the range 5 to 7.
A rudder factor of 4 applies 0.5 degree of helm for each degree off course.
Autotrim is normally turned on.
The Rate Factor compensates for turning inertia in the vessel and its choice is affected by
both the displacement of the vessel and its directional stability. If 10 degrees of helm is
applied and the turn is established within 1 to 3 seconds, then a Rate Factor of 2 is
suitable. If it takes 5 to 10 seconds to reach the full turn rate, then a setting of 4 or 5 is
suitable. Setting the Rate Factor too high can produce excessive rudder activity and slow
down the completion of a course change. Setting it too low produces over-shooting during
course change.
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