Editing Naval architecture (section)

=== Flotation and stability ===
{{main|ship motions|ship stability|initial stability|secondary stability|limit of positive stability}}

[[Image:Translations.PNG|thumb|upright=1.35|Translations]]
[[Image:Rotations.png|thumb|upright=1.35|Axes of a ship and rotations around them]]

While atop a liquid surface a floating body has 6 degrees of freedom in its movements, these are categorized in either translation or rotation.

* Translation
** Sway: transverse
** Surge: fore and aft
** Heave: vertical
* Rotation
** Yaw: about a vertical axis
** Pitch or trim: about a transverse axis
** Roll or heel: about a fore and aft axis

Longitudinal stability for longitudinal inclinations, the stability depends upon the distance between the center of gravity and the longitudinal meta-center. In other words, the basis in which the ship maintains its center of gravity is its distance set equally apart from both the aft and forward section of the ship.

While a body floats on a liquid surface it still encounters the force of gravity pushing down on it. In order to stay afloat and avoid sinking there is an opposed force acting against the body known as the hydrostatic pressures. The forces acting on the body must be of the same magnitude and same line of motion in order to maintain the body at equilibrium. This description of equilibrium is only present when a freely floating body is in still water, when other conditions are present the magnitude of which these forces shifts drastically creating the swaying motion of the body.<ref name=":0">{{Cite book|title=Introduction to Naval Architecture|last=Tupper|first=Eric|publisher=Butterworth-Heinemann|year=1996|location=Oxford, England}}</ref>

The buoyancy force is equal to the weight of the body, in other words, the mass of the body is equal to the mass of the water displaced by the body. This adds an upward force to the body by the amount of surface area times the area displaced in order to create an equilibrium between the surface of the body and the surface of the water.

The stability of a ship under most conditions is able to overcome any form or restriction or resistance encountered in rough seas; however, ships have undesirable roll characteristics when the balance of oscillations in roll is two times that of oscillations in heave, thus causing the ship to capsize.<ref>{{Cite journal|last=Neves|first=M. A. S.|date=2016|title=Dynamic stability of ships in regular and irregular seas - An Overview|journal=Ocean Engineering|volume=120|pages=362–370|doi=10.1016/j.oceaneng.2016.02.010|bibcode=2016OcEng.120..362N }}</ref>