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Displacement Speed
Hull 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. Ship drag for a displacement hull increases smoothly with speed as hull speed is approached and exceeded, often with no noticeable inflection at hull speed. The concept of hull speed is not used in modern naval architecture, where considerations of speed/length ratio or Froude number are considered more helpful. Background As a ship moves in the water, it creates standing waves that oppose its movement. This ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bow Wave
A bow wave is the wave that forms at the bow of a ship when it moves through the water. As the bow wave spreads out, it defines the outer limits of a ship's wake. A large bow wave slows the ship down, is a risk to smaller boats, and in a harbor can damage shore facilities and moored ships. Therefore, ship hulls are generally designed to produce as small a bow wave as possible. Description The size of the bow wave is a function of the speed of the ship, its draft, surface waves, water depth, and the shape of the bow. A ship with a large draft and a blunt bow will produce a large wave, and ships that plane over the water surface will create smaller bow waves. Bow wave patterns are studied in the field of computational fluid dynamics. The bow wave carries energy away from the ship at the expense of its kinetic energy—it slows the ship. A major goal of naval architecture is therefore to reduce the size of the bow wave and improve the ship's fuel economy. Modern ships are commonl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planing (sailing)
Planing ( ) is the mode of operation for a waterborne craft in which its weight is predominantly supported by hydrodynamic lift, rather than hydrostatic lift (buoyancy). Many forms of marine transport make use of planing, including fast ferries, racing boats, floatplanes, flying boats, seaplanes, and water skis. Most surfboards are planing or semi-planing hulls. Beyond planing, fast vessel designs have seen a transition to hydrofoil designs. History The earliest documented planing sailboat was a proa built in 1898 by Commodore Ralph Munroe. It was capable of speeds of more than twice the hull speed. Planing a sailing dinghy was first popularised by Uffa Fox in Britain. In 1928 Fox introduced planing to the racing world in his International 14 dinghy, ''Avenger''. That year he gained 52 first places, 2 seconds, and 3 third places out of 57 race starts. This performance was noticed by other designers who further developed them. Over the years many dinghies have acquired the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Marine Propulsion
Marine propulsion is the mechanism or system used to generate thrust to move a watercraft through water. While paddles and sails are still used on some smaller boats, most modern ships are propelled by mechanical systems consisting of an electric motor or internal combustion engine driving a propeller, or less frequently, in pump-jets, an impeller. Marine engineering is the discipline concerned with the engineering design process of marine propulsion systems. Human-powered paddles and oars, and later, sails were the first forms of marine propulsion. Rowed galleys, some equipped with sail, played an important early role in early human seafaring and warfares. The first advanced mechanical means of marine propulsion was the marine steam engine, introduced in the early 19th century. During the 20th century it was replaced by two-stroke or four-stroke diesel engines, outboard motors, and gas turbine engines on faster ships. Marine nuclear reactors, which appeared in the 1950s, pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stevens Institute Of Technology
Stevens Institute of Technology is a private research university in Hoboken, New Jersey. Founded in 1870, it is one of the oldest technological universities in the United States and was the first college in America solely dedicated to mechanical engineering. The 55-acre campus encompasses Castle Point, the highest point in Hoboken, a campus green and 43 academic, student and administrative buildings. Established through an 1868 bequest from Edwin Augustus Stevens, enrollment at Stevens includes more than 8,000 undergraduate and graduate students representing 47 states and 60 countries throughout Asia, Europe and Latin America. Stevens comprises three schools and one college that deliver technology-based STEM (science, technology, engineering and mathematics) degrees and degrees in business, arts, humanities and social sciences: The Charles V. Schaefer, Jr., School of Engineering and Science, School of Business, School of Systems and Enterprises, and College of Arts and Letters. F ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ultra Light Displacement Boat
An ultra light displacement boat (or ULDB) is a modern form of watercraft with limited displacement relative to the hull size (waterline length). ULDBs are competitive, even after 35 years with open ocean racing participation and podium finishes even today. The relative low cost to obtain, tough construction and readily easy modifications make an Olson or a Hobie an extremely competitive and fun boat. The boats do lack comfort, and are not designed for cruising; however, with multiple transpac races, and multiple Bermuda 1-2 entries, they are proving to be a stalwart competitor despite their older design. See also *Bill Lee (yacht designer) *George Olson (yacht designer) *Olson 30 *Hobie 33 *International Offshore Rule *Ron Moore (boat builder) *Sportsboat The term sportsboat first appeared in the late 1980s and early 1990s to describe trailer sailers that were optimised for high performance at the expense of accommodation and ballast. The very definition of the term "sportsb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
High-speed Craft
A high-speed craft (HSC) is a high-speed water vessel for civilian use, also called a fastcraft or fast ferry. The first high-speed craft were often hydrofoils or hovercraft, but in the 1990s catamaran and monohull designs become more popular and large hydrofoils and hovercraft are no longer built. Most high-speed craft serve as passenger ferries, but the largest catamarans and monohulls also carry cars, buses, large trucks and freight. In the 1990s there were a variety of builders, but due to HSC high fuel consumption, many shipbuilders have withdrawn from this market so the construction of the largest fast ferries, up to 127 metres, has been consolidated to two Australian companies, Austal of Perth and Incat of Hobart. There is still a wide variety of builders for smaller fast catamaran ferries between 24 and 60 metres. Hulled designs are often powered by pump-jets coupled to medium-speed diesel engines. Hovercraft are usually powered by gas turbines or diesel engines dri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Catamaran
A Formula 16 beachable catamaran Powered catamaran passenger ferry at Salem, Massachusetts, United States A catamaran () (informally, a "cat") is a multi-hulled watercraft featuring two parallel hulls of equal size. It is a geometry-stabilized craft, deriving its stability from its wide beam, rather than from a ballasted keel as with a monohull boat. Catamarans typically have less hull volume, smaller displacement, and shallower draft (draught) than monohulls of comparable length. The two hulls combined also often have a smaller hydrodynamic resistance than comparable monohulls, requiring less propulsive power from either sails or motors. The catamaran's wider stance on the water can reduce both heeling and wave-induced motion, as compared with a monohull, and can give reduced wakes. Catamarans were invented by the Austronesian peoples which enabled their expansion to the islands of the Indian and Pacific Oceans. Catamarans range in size from small sailing or rowing ve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rowing (sport)
Rowing, sometimes called crew in the United States, is the sport of racing boats using oars. It differs from paddling sports in that rowing oars are attached to the boat using oarlocks, while paddles are not connected to the boat. Rowing is divided into two disciplines: sculling and sweep rowing. In sculling, each rower holds two oars—one in each hand, while in sweep rowing each rower holds one oar with both hands. There are several boat classes in which athletes may compete, ranging from single sculls, occupied by one person, to shells with eight rowers and a coxswain, called eights. There are a wide variety of course types and formats of racing, but most elite and championship level racing is conducted on calm water courses long with several lanes marked using buoys. Modern rowing as a competitive sport can be traced to the early 17th century when professional watermen held races (regattas) on the River Thames in London, England. Often prizes were offered by the London G ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Canoe
A canoe is a lightweight narrow water vessel, typically pointed at both ends and open on top, propelled by one or more seated or kneeling paddlers facing the direction of travel and using a single-bladed paddle. In British English, the term ''canoe'' can also refer to a kayak, while canoes are called Canadian or open canoes to distinguish them from kayaks. Canoes were developed by cultures all over the world, including some designed for use with sails or outriggers. Until the mid-19th century, the canoe was an important means of transport for exploration and trade, and in some places is still used as such, sometimes with the addition of an outboard motor. Where the canoe played a key role in history, such as the Northern United States, Canada, and New Zealand, it remains an important theme in popular culture. Canoes are now widely used for competition and pleasure, such as racing, whitewater, touring and camping, freestyle and general recreation. Canoeing has been part ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wave-piercing
A wave-piercing boat hull has a very fine bow, with reduced buoyancy in the forward portions. When a wave is encountered, the lack of buoyancy means the hull pierces through the water rather than riding over the top, resulting in a smoother ride than traditional designs, and in diminished mechanical stress on the vessel. It also reduces a boat's wave-making resistance. Design theory calls for very long thin hulls, so in practice most are multi-hulls such as catamarans and trimarans. The main current usage areas are passenger ferries and naval ship A naval ship is a military ship (or sometimes boat, depending on classification) used by a navy A navy, naval force, or maritime force is the branch of a nation's armed forces principally designated for naval warfare, naval and amph ...s. See also * * * , later renamed MY ''Ady Gil'' * * * , a pioneer of the design * * Norwegian Cruise Line -Class Cruise Ships * hull form * * * : an racing multihull * : ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beam (nautical)
The beam of a ship is its width at its widest point. The maximum beam (BMAX) is the distance between planes passing through the outer extremities of the ship, beam of the hull (BH) only includes permanently fixed parts of the hull, and beam at waterline (BWL) is the maximum width where the hull intersects the surface of the water. Generally speaking, the wider the beam of a ship (or boat), the more initial stability it has, at the expense of secondary stability in the event of a capsize, where more energy is required to right the vessel from its inverted position. A ship that heels on her ''beam ends'' has her deck beams nearly vertical. Typical values Typical length-to-beam ratios ( aspect ratios) for small sailboats are from 2:1 (dinghies to trailerable sailboats around ) to 5:1 (racing sailboats over ). Large ships have widely varying beam ratios, some as large as 20:1. Rowing shells designed for flatwater racing may have length to beam ratios as high as 30:1, while a cor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dispersion (water Waves)
In fluid dynamics, dispersion of water waves generally refers to frequency dispersion, which means that waves of different wavelengths travel at different phase speeds. Water waves, in this context, are waves propagating on the water surface, with gravity and surface tension as the restoring forces. As a result, water with a free surface is generally considered to be a dispersive medium. For a certain water depth, surface gravity waves – i.e. waves occurring at the air–water interface and gravity as the only force restoring it to flatness – propagate faster with increasing wavelength. On the other hand, for a given (fixed) wavelength, gravity waves in deeper water have a larger phase speed than in shallower water. In contrast with the behavior of gravity waves, capillary waves (i.e. only forced by surface tension) propagate faster for shorter wavelengths. Besides frequency dispersion, water waves also exhibit amplitude dispersion. This is a nonlinear effect, by which wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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