Roll stabilisation

A variety of roll stabilisation systems are available to reduce ship motions and forces which can cause cargo damage, undermine passenger comfort and crew efficiency, and increase resistance. Among the main options are bilge keels, passive tanks, activated fins and rudder stabilisation, and combinations of these systems.

Bilge keels are a simple measure used against rolling. They act in two ways. First, a hydrodynamic force opposed to the roll motion develops on them. Secondly, bilge keels cause vortexes that increase the viscous damping of the roll motion. The most common way of stabilising vessels that normally operate at cruising speeds of 12 knots or more has been the use of active-fin stabilisers. For vessels which operate at speeds too low for active-fin stabilizers, anti-roll tanks or flume stabilisation systems are often used.

Cruise ships can benefit from combined stabilising systems with fin stabilisers deployed primarily at speed while tank stabilisers assume responsibility for roll reduction under other operating conditions.  Movable-weight systems are the alternative means of reducing roll amplitudes. See also Rudder roll stabilisation.

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