Ship motions

Ship motions

Ship motions are defined by the six degrees of freedom that a ship or boat can experience.


Heave : is the linear vertical (up/down) motion

Sway : is the linear lateral (side-to-side) motion

Surge : is the linear longitudinal (front/back) motion


Roll : is when the vessel rotates about the longitudinal (front/back) axis.

Pitch : is when the vessel rotates about the transverse (side-to-side) axis.

Yaw : is when the vessel rotates about the vertical (up-down) axis.


There are methods for both passive and active motion stabilization used in some designs. They can include static hull features such as skegs and bilge keels, or active mechanical devices like counterweights, anti-roll ballast tanks, and stabilizing fins.

See also


1) Society of Naval Architects and Marine Engineers (SNAME), "Principles of Naval Architecture", 1989, Vol. III, Pg.41, Section 3 - Ship Responses to Regular Waves.

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