Page 281 - Introduction to Naval Architecture
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266 MANOEUVRING
Figure 10.7 Semi-balanced rudder
Figure 10.8 Flap rudder
In semi-balanced and unbalanced rudders the fixed structure ahead
of the rudder can be shaped to help augment the lateral force at the
rudder.
Active rudders
These are usually spade type rudders but incorporating a faired
housing with a small electric motor driving a small propeller. This
provides a 'rudder' force even when the ship is at rest when the
hydrodynamic forces on the rudder would be zero. It is used in ships
requiring good manoeuvrability at very low speeds.
