A dry dock is a narrow basin or vessel that can be flooded to allow a load to be floated in, then drained to allow that load to come to rest on a dry platform. Dry docks are used for the construction, maintenance, and repair of ships, boats, and other watercraft.
A junk is a type of Chinese sailing ship characterized by a central rudder, an overhanging flat transom, watertight bulkheads, and a flat-bottomed design. They are also characteristically built using iron nails and clamps. The term applies to many types of small coastal or river ships, usually serving as cargo ships, pleasure boats, or houseboats, but also going up in size up to large ocean-going vessels. There can be significant regional variations in the type of rig and the layout of the vessel.
The metacentric height (GM) is a measurement of the initial static stability of a floating body. It is calculated as the distance between the centre of gravity of a ship and its metacentre. A larger metacentric height implies greater initial stability against overturning. The metacentric height also influences the natural period of rolling of a hull, with very large metacentric heights being associated with shorter periods of roll which are uncomfortable for passengers. Hence, a sufficiently, but not excessively, high metacentric height is considered ideal for passenger ships.
A bulkhead is an upright wall within the hull of a ship, within the fuselage of an airplane, or a car. Other kinds of partition elements within a ship are decks and deckheads.
Capsizing or keeling over occurs when a boat or ship is rolled on its side or further by wave action, instability or wind force beyond the angle of positive static stability or it is upside down in the water. The act of recovering a vessel from a capsize is called righting. Capsize may result from broaching, knockdown, loss of stability due to cargo shifting or flooding, or in high speed boats, from turning too fast.
A cofferdam is an enclosure built within a body of water to allow the enclosed area to be pumped out or drained. This pumping creates a dry working environment so that the work can be carried out safely. Cofferdams are commonly used for construction or repair of permanent dams, oil platforms, bridge piers, etc., built within water. They also form an integral part of naval architecture.
On April 14, 1912, the Titanic collided with an iceberg, damaging the hull's plates below the waterline on the starboard side, causing the front compartments to flood. The ship then sank two hours and forty minutes later, with approximately 1,496 fatalities as a result of drowning or hypothermia. Since then, many conspiracy theories have been suggested regarding the disaster. These theories have been refuted by subject-matter experts.
A double hull is a ship hull design and construction method where the bottom and sides of the ship have two complete layers of watertight hull surface: one outer layer forming the normal hull of the ship, and a second inner hull which is some distance inboard, typically by a few feet, which forms a redundant barrier to seawater in case the outer hull is damaged and leaks.
A ballast tank is a compartment within a boat, ship or other floating structure that holds water, which is used as ballast to provide hydrostatic stability for a vessel, to reduce or control buoyancy, as in a submarine, to correct trim or list, to provide a more even load distribution along the hull to reduce structural hogging or sagging stresses, or to increase draft, as in a semi-submersible vessel or platform, or a SWATH, to improve seakeeping. Using water in a tank provides easier weight adjustment than the stone or iron ballast used in older vessels, and makes it easy for the crew to reduce a vessel's draft when it enters shallower water, by temporarily pumping out ballast. Airships use ballast tanks mainly to control buoyancy and correct trim.
Belt armor is a layer of heavy metal armor plated onto or within the outer hulls of warships, typically on battleships, battlecruisers and cruisers, and aircraft carriers.
A submarine hull has two major components, the light hull and the pressure hull. The light hull of a submarine is the outer non-watertight hull which provides a hydrodynamically efficient shape. The pressure hull is the inner hull of a submarine that maintains structural integrity with the difference between outside and inside pressure at depth.
The naval history of China dates back thousands of years, with archives existing since the late Spring and Autumn period regarding the Chinese navy and the various ship types employed in wars. The Ming dynasty of China was the leading global maritime power between 1400 and 1433, when Chinese shipbuilders built massive ocean-going junks and the Chinese imperial court launched seven maritime voyages. In modern times, the current People's Republic of China and the Republic of China governments continue to maintain standing navies through the People's Liberation Army Navy and the Republic of China Navy, respectively.
The Song dynasty witnessed many substantial scientific and technological advances in Chinese history. Some of these advances and innovations were the products of talented statesmen and scholar-officials drafted by the government through imperial examinations. Shen Kuo (1031–1095), author of the Dream Pool Essays, is a prime example, an inventor and pioneering figure who introduced many new advances in Chinese astronomy and mathematics, establishing the concept of true north in the first known experiments with the magnetic compass. However, commoner craftsmen such as Bi Sheng (972–1051), the inventor of movable type printing, were also heavily involved in technical innovations.
Ship stability is an area of naval architecture and ship design that deals with how a ship behaves at sea, both in still water and in waves, whether intact or damaged. Stability calculations focus on centers of gravity, centers of buoyancy, the metacenters of vessels, and on how these interact.
The anti-torpedo bulge is a form of defence against naval torpedoes occasionally employed in warship construction in the period between the First and Second World Wars. It involved fitting partially water-filled compartmentalized sponsons on either side of a ship's hull, intended to detonate torpedoes, absorb their explosions, and contain flooding to damaged areas within the bulges.
Zhu Yu was a Chinese maritime historian during the Song dynasty. He retired in Huang Gang (黄岗) of the Hubei province, bought a country house and named it "Pingzhou". He called himself "Expert Vegetable Grower of Pingzhou (萍洲老圃)". Between 1111 and 1117 AD, Zhu Yu wrote the book Pingzhou Ketan, published in 1119 AD. It covered a wide variety of maritime subjects and issues in China at the time. His extensive knowledge of maritime engagements, technologies, and practices were because his father, Zhu Fu, was the Port Superintendent of Merchant Shipping for Guangzhou from 1094 until 1099 AD, whereupon he was elevated to the status of governor there and served in that office until 1102 AD.
FV Alaska Ranger was a fishing factory ship owned and operated by the Fishing Company of Alaska of Seattle, Washington. The ship was constructed in 1973 for use as an oil field service vessel. The ship sank 23 March 2008, after reporting progressive flooding only hours earlier. Of the 47 on board, 42 were rescued. Of the five fatalities, four were recovered dead, and one was never found. The Coast Guard was initially misinformed about the number of persons on board the vessel, and secured the search with one crew member still unaccounted for. After realizing there was still one person missing, the Coast Guard reinstated the search, but did not find the crew member.
Shipwrecking is an event that causes a shipwreck, such as a ship striking something that causes the ship to sink; the stranding of a ship on rocks, land or shoal; poor maintenance, resulting in a lack of seaworthiness; or the destruction of a ship either intentionally or by violent weather.
A compartment is a portion of the space within a ship defined vertically between decks and horizontally between bulkheads. It is analogous to a room within a building, and may provide watertight subdivision of the ship's hull important in retaining buoyancy if the hull is damaged. Subdivision of a ship's hull into watertight compartments is called compartmentation.
A variable-buoyancy pressure vessel system is a type of rigid buoyancy control device for diving systems that retains a constant volume and varies its density by changing the weight (mass) of the contents, either by moving the ambient fluid into and out of a rigid pressure vessel, or by moving a stored liquid between internal and external variable-volume containers. A pressure vessel is used to withstand the hydrostatic pressure of the underwater environment. A variable-buoyancy pressure vessel can have an internal pressure greater or less than ambient pressure, and the pressure difference can vary from positive to negative within the operational depth range, or remain either positive or negative throughout the pressure range, depending on design choices.
