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Ley-class Minehunter
The Ley class was a class of inshore minehunter built for the Royal Navy in the mid-1950s. They had pennant numbers in the series M2001. Eleven ships were built in the early 1950s, most of which were subsequently disarmed and used as training vessels, RNXS tenders, URNU vessels etc. Description They were of composite construction, that is, wood and non-ferrous metals, to give a low magnetic signature, important in a vessel that may be dealing with magnetically detonated mines. They displaced 164 tons fully laden, were armed with a Bofors 40 mm gun or an Oerlikon 20 mm gun and were powered by a pair of Paxman diesel engines. The class shared the same basic hull as their inshore minesweeper counterpart the and the inshore survey craft. Role Unlike traditional minesweepers, they were not equipped for sweeping moored or magnetic mines. Their work was to locate individual mines and neutralise them. This was a new role at that point, and the class was configured for workin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Minehunter
A minehunter is a naval vessel that seeks, detects, and destroys individual naval mines. Minesweepers, on the other hand, clear mined areas as a whole, without prior detection of mines. A vessel that combines both of these roles is known as a mine countermeasures vessel (MCMV). Description A minehunter uses an imaging sonar to detect and classify targets and then sends out divers or remotely operated vehicles to inspect and neutralise the threat, often using small charges that are detonated remotely. As minehunters will often be operating in close proximity to mines, they are designed so as to reduce their own acoustic and magnetic signatures, two common forms of trigger for mines. For example, they are often soundproofed by mounting machinery on shock absorbers or by using quiet electrical drive, low magnetic electric motors and usually have a wood, fiberglass or non-ferrous metal hull, or are degaussed to reduce magnetic signature.Design Guide and Requirements for E ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetism
Magnetism is the class of physical attributes that are mediated by a magnetic field, which refers to the capacity to induce attractive and repulsive phenomena in other entities. Electric currents and the magnetic moments of elementary particles give rise to a magnetic field, which acts on other currents and magnetic moments. Magnetism is one aspect of the combined phenomena of electromagnetism. The most familiar effects occur in ferromagnetic materials, which are strongly attracted by magnetic fields and can be magnetized to become permanent magnets, producing magnetic fields themselves. Demagnetizing a magnet is also possible. Only a few substances are ferromagnetic; the most common ones are iron, cobalt, and nickel and their alloys. The rare-earth metals neodymium and samarium are less common examples. The prefix ' refers to iron because permanent magnetism was first observed in lodestone, a form of natural iron ore called magnetite, Fe3O4. All substances exhibit some ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sea Cadets (United Kingdom)
The Sea Cadet Corps is a national youth charity, working with 15,000 young people between 10 and 18 years old across the UK. It has over 400 units across England, Scotland, Wales, Northern Ireland, Malta and Bermuda all run by 9,000 volunteers. Cadets follow a similar ethos, training plan, and rank structure, to the Royal Navy, and are recognised by the UK Ministry of Defence. History In 1854 a Vicar in Whitstable, Kent, returning from the Crimean War noticed many local orphans on the street, he set up an orphanage encouraging sailors to form a group to help them. This led to multiple other orphanages being set up across the country. Back then the organisation was known as the Naval Lads' Brigade with sailors teaching orphans nautical skills to help them find careers in the future. Gaining recognition, in 1899 Queen Victoria presented £10 (around £1,000 today) to the Windsor Unit to purchase uniforms. The Navy League in 1910 sponsored a small number of units as the Nav ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shipping Channel
In physical geography, a channel is a type of landform consisting of the outline of a path of relatively shallow and narrow body of water or of other fluids (e.g., lava), most commonly the confine of a river, river delta or strait. The word is cognate to canal, and sometimes takes this form, e.g. the Hood Canal. Formation Channel initiation refers to the site on a mountain slope where water begins to flow between identifiable banks.Bierman, R. B, David R. Montgomery (2014). Key Concepts in Geomorphology. W. H. Freeman and Company Publishers. United States. This site is referred to as the channel head and it marks an important boundary between hillslope processes and fluvial processes. The channel head is the most upslope part of a channel network and is defined by flowing water between defined identifiable banks. A channel head forms as overland flow and/or subsurface flow accumulate to a point where shear stress can overcome erosion resistance of the ground surface. Channel h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Estuary
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environments and are an example of an ecotone. Estuaries are subject both to marine influences such as tides, waves, and the influx of saline water, and to fluvial influences such as flows of freshwater and sediment. The mixing of seawater and freshwater provides high levels of nutrients both in the water column and in sediment, making estuaries among the most productive natural habitats in the world. Most existing estuaries formed during the Holocene epoch with the flooding of river-eroded or glacially scoured valleys when the sea level began to rise about 10,000–12,000 years ago. Estuaries are typically classified according to their geomorphological features or to water-circulation patterns. They can have many different names, such as bay ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
River
A river is a natural flowing watercourse, usually freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ..., flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of water. Small rivers can be referred to using names such as Stream#Creek, creek, Stream#Brook, brook, rivulet, and rill. There are no official definitions for the generic term river as applied to Geographical feature, geographic features, although in some countries or communities a stream is defined by its size. Many names for small rivers are specific to geographic location; examples are "run" in some parts of the United States, "Burn (landform), burn" in Scotland and northeast England, and "be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Minesweeper
A minesweeper is a small warship designed to remove or detonate naval mines. Using various mechanisms intended to counter the threat posed by naval mines, minesweepers keep waterways clear for safe shipping. History The earliest known usage of the naval mine dates to the Ming dynasty.Needham, Volume 5, Part 7, 203–205. Dedicated minesweepers, however, only appeared many centuries later during the Crimean War, where they were deployed by the British. The Crimean War minesweepers were rowboats trailing grapnels to snag mines. Minesweeping technology picked up in the Russo-Japanese War, using aging torpedo boats as minesweepers. In Britain, naval leaders recognized before the outbreak of World War I that the development of sea mines was a threat to the nation's shipping and began efforts to counter the threat. Sir Arthur Wilson noted the real threat of the time was blockade aided by mines and not invasion. The function of the fishing fleet's trawlers with their trawl gear was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diesel Engine
The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-called compression-ignition engine (CI engine). This contrasts with engines using spark plug-ignition of the air-fuel mixture, such as a petrol engine ( gasoline engine) or a gas engine (using a gaseous fuel like natural gas or liquefied petroleum gas). Diesel engines work by compressing only air, or air plus residual combustion gases from the exhaust (known as exhaust gas recirculation (EGR)). Air is inducted into the chamber during the intake stroke, and compressed during the compression stroke. This increases the air temperature inside the cylinder to such a high degree that atomised diesel fuel injected into the combustion chamber ignites. With the fuel being injected into the air just before combustion, the dispersion of the fuel is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paxman (engines)
Paxman is a major British brand of diesel engines. Ownership has changed on a number of occasions since the company's formation in 1865, and now the brand is part of MAN Diesel & Turbo. At its peak, the Paxman works covered and employed over 2,000 people. Early Paxman diesel engines (with "Comet" indirect injection cylinder heads, designed by Sir Harry Ricardo) carried the name Paxman Ricardo. History Davey Paxman Paxman was founded by James Noah Paxman, Henry and Charles Davey as Davey, Paxman & Davey, Engineers in 1865, later Davey, Paxman & Co. which became a limited company in 1898. In 1920 the company became a member of the Agricultural & General Engineers (AGE) combine. In 1932 AGE collapsed and Paxman emerged as Davey Paxman & Co (Colchester) Ltd. Davey, Paxman and Davey conducted business as general engineers and ironworkers. The company manufactured steam engines, boilers, agricultural machinery, and mill gearing. By the early 1870s the company was supplying mach ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Mine
A naval mine is a self-contained explosive device placed in water to damage or destroy surface ships or submarines. Unlike depth charges, mines are deposited and left to wait until they are triggered by the approach of, or contact with, any vessel or a particular vessel type, akin to anti-infantry vs. anti-vehicle mines. Naval mines can be used offensively, to hamper enemy shipping movements or lock vessels into a harbour; or defensively, to protect friendly vessels and create "safe" zones. Mines allow the minelaying force commander to concentrate warships or defensive assets in mine-free areas giving the adversary three choices: undertake an expensive and time-consuming minesweeping effort, accept the casualties of challenging the minefield, or use the unmined waters where the greatest concentration of enemy firepower will be encountered. Although international law requires signatory nations to declare mined areas, precise locations remain secret; and non-complying individua ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Non-ferrous Metal
In metallurgy, non-ferrous metals are metals or alloys that do not contain iron ( allotropes of iron, ferrite, and so on) in appreciable amounts. Generally more costly than ferrous metals, non-ferrous metals are used because of desirable properties such as low weight (e.g. aluminium), higher conductivity (e.g. copper), non- magnetic properties or resistance to corrosion (e.g. zinc). Some non-ferrous materials are also used in the iron and steel industries. For example, bauxite is used as flux for blast furnaces, while others such as wolframite, pyrolusite, and chromite are used in making ferrous alloys. Important non-ferrous metals include aluminium, copper, lead, tin, titanium, and zinc, and alloys such as brass. Precious metals such as gold, silver, and platinum and exotic or rare metals such as mercury, tungsten, beryllium, bismuth, cerium, cadmium, niobium, indium, gallium, germanium, lithium, selenium, tantalum, tellurium, vanadium, and zirconium are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Length Between Perpendiculars
Length between perpendiculars (often abbreviated as p/p, p.p., pp, LPP, LBP or Length BPP) is the length of a ship along the summer load line from the forward surface of the stem, or main bow perpendicular member, to the after surface of the sternpost A sternpost is the upright structural member or post at the stern of a (generally wooden) ship or a boat, to which are attached the transoms and the rearmost left corner part of the stern. The sternpost may either be completely vertical or m ..., or main stern perpendicular member. When there is no sternpost, the centerline axis of the rudder stock is used as the aft end of the length between perpendiculars. Measuring to the stern post or rudder stock was believed to give a reasonable idea of the ship's carrying capacity, as it excluded the small, often unusable volume contained in her overhanging ends. On some types of vessels this is, for all practical purposes, a waterline measurement. In a ship with raked stems, natural ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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