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Block (sailing)
In sailing, a block is a single or multiple pulley. One or a number of '' sheaves'' are enclosed in an assembly between ''cheeks'' or ''chocks''. In use, a block is fixed to the end of a line, to a spar, or to a surface. A line (rope) is ''reeved'' through the sheaves, and maybe through one or more matching blocks at some far end, to make up a tackle. The ''purchase'' of a tackle refers to its mechanical advantage. In general the more sheaves in the blocks that make up a tackle, the higher its mechanical advantage. The matter is slightly complicated by the fact that every tackle has a ''working end'' where the final run of rope leaves the last sheave. More mechanical advantage can be obtained if this end is attached to the moving load rather than the fixed end of the tackle. There are various types of blocks that are used in sailing. Some blocks are used to increase mechanical advantage and others are used simply to change the direction of a line. A ''ratchet block'' turn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shipbuilding Cyclopedia 386
Shipbuilding is the construction of ships and other floating vessels. In modern times, it normally takes place in a specialized facility known as a shipyard. Shipbuilders, also called shipwrights, follow a specialized occupation that traces its roots to before recorded history. Until recently, with the development of complex non-maritime technologies, a ship has often represented the most advanced structure that the society building it could produce. Some key industrial advances were developed to support shipbuilding, for instance the sawing of timbers by mechanical saws propelled by windmills in Dutch shipyards during the first half of the 17th century. The design process saw the early adoption of the logarithm (invented in 1615) to generate the curves used to produce the shape of a hull, especially when scaling up these curves accurately in the mould loft. Shipbuilding and ship repairs, both commercial and military, are referred to as naval engineering. The construction of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sailing
Sailing employs the wind—acting on sails, wingsails or kites—to propel a craft on the surface of the ''water'' (sailing ship, sailboat, raft, Windsurfing, windsurfer, or Kitesurfing, kitesurfer), on ''ice'' (iceboat) or on ''land'' (Land sailing, land yacht) over a chosen Course (navigation), course, which is often part of a larger plan of navigation. From prehistory until the second half of the 19th century, sailing craft were the primary means of maritime trade and transportation; exploration across the seas and oceans was reliant on sail for anything other than the shortest distances. Naval power in this period used sail to varying degrees depending on the current technology, culminating in the gun-armed sailing warships of the Age of Sail. Sail was slowly replaced by steam as the method of propulsion for ships over the latter part of the 19th century – seeing a gradual improvement in the technology of steam through a number of developmental steps. Steam allowed schedul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pulley
Sheave without a rope A pulley is a wheel on an axle or shaft enabling a taut cable or belt passing over the wheel to move and change direction, or transfer power between itself and a shaft. A pulley may have a groove or grooves between flanges around its circumference to locate the cable or belt. The drive element of a pulley system can be a rope, cable, belt, or chain. History The earliest evidence of pulleys dates back to Ancient Egypt in the Twelfth Dynasty (1991–1802 BC) and Mesopotamia in the early 2nd millennium BC. In Roman Egypt, Hero of Alexandria (c. 10–70 AD) identified the pulley as one of six simple machines used to lift weights. Pulleys are assembled to form a block and tackle in order to provide mechanical advantage to apply large forces. Pulleys are also assembled as part of belt and chain drives in order to transmit power from one rotating shaft to another. Plutarch's ''Parallel Lives'' recounts a scene where Archimedes proved the effectiveness ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spar (sailing)
A spar is a pole of wood, metal or lightweight materials such as carbon fibre used in the rigging of a sailing vessel to carry or support its sail. These include yards, booms, and masts, which serve both to deploy sail and resist compressive and bending forces, as well as the bowsprit and spinnaker pole. In larger vessels during the age of sail, spare spars could be roped together to provide a temporary surface known as a "spar deck". These served as jury-rigged repairs for permanent decks, or as an additional platform under which to shelter goods or crew. The term was also informally applied to areas of the forecastle The forecastle ( ; contracted as fo'c'sle or fo'c's'le) is the upper deck (ship), deck of a sailing ship forward of the foremast, or, historically, the forward part of a ship with the sailors' living quarters. Related to the latter meaning is t ... or quarterdeck where spare spars were stored by laying them flat against the existing decking. In the moder ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Block And Tackle
A block and tackle or only tackle is a system of two or more pulleys with a rope or cable threaded between them, used to provide tension and lift heavy loads. The pulleys are assembled to form blocks and then blocks are paired so that one is fixed and one moves with the load. The rope is threaded through the pulleys to provide mechanical advantage that amplifies the force applied to the rope. Hero of Alexandria described cranes formed from assemblies of pulleys in the first century. Illustrated versions of Hero's ''Mechanica'' (a book on raising heavy weights) show early block and tackle systems. Overview A block is a set of pulleys or sheaves mounted on a single frame. An assembly of blocks with a rope threaded through the pulleys is called tackle. The process of threading ropes or cables through blocks is called "reeving", and a threaded block and tackle is said to have been "rove". A block and tackle system amplifies the tension force in the rope to lift heavy loads ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mechanical Advantage
Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. The device trades off input forces against movement to obtain a desired amplification in the output force. The model for this is the ''law of the lever.'' Machine components designed to manage forces and movement in this way are called mechanisms. An ideal mechanism transmits power without adding to or subtracting from it. This means the ideal machine does not include a power source, is frictionless, and is constructed from rigid bodies that do not deflect or wear. The performance of a real system relative to this ideal is expressed in terms of efficiency factors that take into account departures from the ideal. Levers The lever is a movable bar that pivots on a fulcrum attached to or positioned on or across a fixed point. The lever operates by applying forces at different distances from the fulcrum, or pivot. The location of the fulcrum deter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mary Rose
The ''Mary Rose'' was a carrack in the English Tudor navy of Henry VIII of England, King Henry VIII. She was launched in 1511 and served for 34 years in several wars against France, Scotland, and Brittany. After being substantially rebuilt in 1536, she saw her last action on 1545. She led the attack on the galleys of a French invasion fleet, but sank off Spithead in the Solent, the strait north of the Isle of Wight. The wreck of the ''Mary Rose'' was located in 1971 and was raised on 11 October 1982 by the Mary Rose Trust in one of the most complex and expensive maritime salvage projects in history. The surviving section of the ship and thousands of recovered artefacts are of great value as a Tudor period time capsule. The excavation and raising of the ''Mary Rose'' was a milestone in the field of maritime archaeology, comparable in complexity and cost to the raising of the 17th-century Swedish warship ''Vasa (ship), Vasa'' in 1961. The ''Mary Rose'' site is designated under ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stainless Steel
Stainless steel, also known as inox, corrosion-resistant steel (CRES), or rustless steel, is an iron-based alloy that contains chromium, making it resistant to rust and corrosion. Stainless steel's resistance to corrosion comes from its chromium content of 11% or more, which forms a Passivation (chemistry), passive film that protects the material and can self-healing material, self-heal when exposed to oxygen. It can be further alloyed with elements like molybdenum, carbon, nickel and nitrogen to enhance specific properties for various applications. The alloy's properties, such as luster and resistance to corrosion, are useful in many applications. Stainless steel can be rolled into Sheet metal, sheets, plates, bars, wire, and tubing. These can be used in cookware, cutlery, surgical instruments, major appliances, vehicles, construction material in large buildings, industrial equipment (e.g., in paper mills, chemical plants, water treatment), and storage tanks and tankers for ch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reinforced Plastic
Fibre-reinforced plastic (FRP; also called fibre-reinforced polymer, or in American English ''fiber'') is a composite material made of a polymer matrix reinforced with fibres. The fibres are usually glass (in fibreglass), carbon (in carbon-fibre-reinforced polymer), aramid, or basalt. Rarely, other fibres such as paper, wood, boron, or asbestos have been used. The polymer is usually an epoxy, vinyl ester, or polyester thermosetting plastic, though phenol formaldehyde resins are still in use. FRPs are commonly used in the aerospace, automotive, marine, and construction industries. They are commonly found in ballistic armour and cylinders for self-contained breathing apparatuses. History Bakelite was the first fibre-reinforced plastic. Leo Baekeland had originally set out to find a replacement for shellac (made from the excretion of lac bugs). Chemists had begun to recognize that many natural resins and fibres were polymers, and Baekeland investigated the reactions of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polyoxymethylene
Polyoxymethylene (POM), also known as acetal, polyacetal, and polyformaldehyde, is an engineering thermoplastic used in precision parts requiring high stiffness, low friction, and excellent dimensional stability. Short-chained POM (chain length between 8 and 100 repeating units) is also better known as paraformaldehyde (PFA). As with many other synthetic polymers, polyoxymethylenes are produced by different chemical firms with slightly different formulas and sold as Delrin, Kocetal, Ultraform, Celcon, Ramtal, Duracon, Kepital, Polypenco, Tenac and Hostaform. POM is characterized by its high strength, hardness and rigidity to −40 °C. POM is intrinsically opaque white because of its high crystalline composition but can be produced in a variety of colors. POM has a density of 1.410–1.420g/cm3. Typical applications for injection-molded POM include high-performance engineering components such as small gear wheels, eyeglass frames, ball bearings, ski bindings, fasteners ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Portrait Of Marc Isambard Brunel
The '' Portrait of Marc Isambard Brunel'' is a portrait painting by the English artist James Northcote depicting the French-born British engineer Marc Isambard Brunel. Brunel was a pioneering engineer of the Regency era known particularly for his creation of a Portsmouth Block Mills, block-making machine during the Napoleonic Wars and his later construction of the Thames Tunnel, a project which also involved his son Isambard Kingdom Brunel. Northcote was a member of the Royal Academy and established portraitist. It was exhibited at the academy's Summer Exhibition in 1814. He was paid twenty guineas for the portrait, which was commissioned by Thomas Mudge, Brunel's business partner and the brother-in-law of his wife. The work shows Brunel in a velvet coat with a model of one of his block-making machines in the background. Today it is part of the collection of the National Portrait Gallery, London, National Portrait Gallery in London having been donated by the sitter's grandson Henr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
