Naval armourNaval armor refers to the various protections schemes employed by warships. The first ironclad warship was created in 1859, and the pace of armour advancement accelerated quickly thereafter. The emergence of battleships around the turn of the 20th century saw ships become increasingly large and well armoured. Vast quantities of heavily armoured ships were used during the World Wars, and were crucial in the outcome. The emergence of guided missiles in the last part of the 20th century has greatly reduced the utility of armor, and most modern warships are now only lightly armored.
Outboard motorAn outboard motor is a propulsion system for boats, consisting of a self-contained unit that includes engine, gearbox and propeller or jet drive, designed to be affixed to the outside of the transom. They are the most common motorised method of propelling small watercraft. As well as providing propulsion, outboards provide steering control, as they are designed to pivot over their mountings and thus control the direction of thrust. The skeg also acts as a rudder when the engine is not running.
Double hullA 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. The space between the two hulls is sometimes used for storage of ballast water.
Hull speedHull speed or displacement speed is the speed at which the wavelength of a vessel's bow wave is equal to the waterline length of the vessel. As boat speed increases from rest, the wavelength of the bow wave increases, and usually its crest-to-trough dimension (height) increases as well. When hull speed is exceeded, a vessel in displacement mode will appear to be climbing up the back of its bow wave. From a technical perspective, at hull speed the bow and stern waves interfere constructively, creating relatively large waves, and thus a relatively large value of wave drag.
Ducted propellerA ducted propeller, also known as a Kort nozzle, is a marine propeller fitted with a non-rotating nozzle. It is used to improve the efficiency of the propeller and is especially used on heavily loaded propellers or propellers with limited diameter. It was developed first by Luigi Stipa (1931) and later by Ludwig Kort (1934). The Kort nozzle is a shrouded propeller assembly for marine propulsion. The cross-section of the shroud has the form of a foil, and the shroud can offer hydrodynamic advantages over bare propellers, under certain conditions.
T2 tankerThe T2 tanker, or T2, was a class of oil tanker constructed and produced in large numbers in the United States during World War II. Only the T3 tankers were larger "navy oilers" of the period. Some 533 T2s were built between 1940 and the end of 1945. They were used to transport fuel oil, diesel fuel, gasoline and sometimes black oil-crude oil. Post war many T2s remained in use; like other hastily built World War II ships pressed into peacetime service, there were safety concerns.
HandysizeHandysize is a naval architecture term for smaller bulk carriers or oil tanker with deadweight of up to 50,000 tonnes, although there is no official definition in terms of exact tonnages. Handysize is also sometimes used to refer to the span of up to 60,000 tons, with the vessels above 35,000 tonnes referred to as Handymax or Supramax. Their small size allows Handysize vessels to enter smaller ports to pick up cargoes, and because in most cases they are 'geared' - i.e.
Dry dockA dry dock (sometimes drydock or 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. The Greek author Athenaeus of Naucratis (V 204c-d) reports something that may have been a dry dock in Ptolemaic Egypt in the reign of Ptolemy IV Philopator (221-204 BC) on the occasion of the launch of the enormous Tessarakonteres rowing ship.
Djong (ship)The djong, jong, or jung is a type of sailing ship originating from Java, Indonesia that was widely used by Javanese, Sundanese, and later, by Malay sailors. The word was and is spelled jong in its languages of origin, the "djong" spelling being the colonial Dutch romanization. In English, the djong lends its name to other ships of similar configuration, called junks, and to their characteristic style of rigging, the junk rig. Djongs are used mainly as seagoing passenger and cargo vessels.
Underwater archaeologyUnderwater archaeology is archaeology practiced underwater. As with all other branches of archaeology, it evolved from its roots in pre-history and in the classical era to include sites from the historical and industrial eras. Its acceptance has been a relatively late development due to the difficulties of accessing and working underwater sites, and because the application of archaeology to underwater sites initially emerged from the skills and tools developed by shipwreck salvagers.
