Editing Ship (section)

===Hull===
{{main|Hull (watercraft)}}
[[File:CargoVslBadWeather.JPG|thumb|right|A ship's hull endures harsh conditions at sea, as illustrated by this [[reefer ship]] in bad weather.]]
For a ship to float, its weight must be less than that of the water displaced by the ship's hull.<ref>{{cite web|title=Boats – Why do they float?|url=https://betterplaneteducation.org.uk/factsheets/boats-how-boats-float|publisher=Better Planet Education (formerly YPTE) |access-date=16 September 2024 |url-status=live |archive-url=https://web.archive.org/web/20121231065913/http://www.ypte.org.uk/environmental/boats-why-do-they-float-/107 |archive-date= Dec 31, 2012 }}</ref> There are many types of hulls, from logs lashed together to form a raft to the advanced hulls of [[America's Cup]] sailboats. A vessel may have a single hull (called a monohull design), two in the case of [[catamaran]]s, or three in the case of [[trimaran]]s. Vessels with more than three hulls are rare, but some experiments have been conducted with designs such as pentamarans. Multiple hulls are generally parallel to each other and connected by rigid arms.

Hulls have several elements. The [[bow (ship)|bow]] is the foremost part of the hull. Many ships feature a [[bulbous bow]]. The [[keel]] is at the very bottom of the hull, extending the entire length of the ship. The rear part of the hull is known as the [[stern]], and many hulls have a flat back known as a [[transom (nautical)|transom]]. Common hull appendages include [[propeller]]s for propulsion, [[rudder]]s for steering, and [[Stabilizer (ship)|stabilizers]] to quell a ship's rolling motion. Other hull features can be related to the vessel's work, such as fishing gear and [[sonar|sonar domes]].

Hulls are subject to various hydrostatic and hydrodynamic constraints. The key hydrostatic constraint is that it must be able to support the entire weight of the boat, and maintain stability even with often unevenly distributed weight. Hydrodynamic constraints include the ability to withstand shock waves, weather collisions and groundings.

Older ships and pleasure craft often have or had wooden hulls. Steel is used for most commercial vessels. Aluminium is frequently used for fast vessels, and [[composite material]]s are often found in sailboats and pleasure craft. Some ships have been made with [[Concrete ship|concrete hulls]].