Figure 4.2: Various Rudder-Fin Arrangements
All-movable rudders are desirable for their ability to produce large turning forces for their size. The required rudder moment is strongly in‡uenced by a careful choice of the balance ratio; this is the rudder area forward of the rudder stock divided by the total rudder area. Usually, this balance ratio varies between 0.25 for ships with a small block coe¢cient and 0.27 for ships with a large block coe¢cient.
Structural considerations, costs, the need for additional stabilizing side forces provided by a horn and the considerations may require use of other types of rudders such as the semi-suspended (or horn) rudder. The horn type is also favored for operations in ice.