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Raft
A raft is any flat structure for support or transportation over water. It is usually of basic design, characterized by the absence of a hull. Rafts are usually kept afloat by using any combination of buoyant materials such as wood, sealed barrels, or inflated air chambers (such as pontoons), and are typically not propelled by an engine. Rafts are an ancient mode of transport; naturally-occurring rafts such as entwined vegetation and pieces of wood have been used to traverse water since the dawn of humanity. Human-made rafts Traditional or primitive rafts were constructed of wood or reeds. Modern rafts may also use pontoons, drums, or extruded polystyrene Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a ... blocks. Inflatable rafts up to the 20th century used flotation chambers ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rafting
Rafting and whitewater rafting are recreational outdoor activities which use an inflatable raft to navigate a river or other body of water. This is often done on whitewater or different degrees of rough water. Dealing with risk is often a part of the experience. This activity as an adventure sport has become popular since the 1950s, if not earlier, evolving from individuals paddling to rafts with double-bladed paddles or oars to multi-person rafts propelled by single-bladed paddles and steered by a person at the stern, or by the use of oars. Rafting on certain sections of rivers is considered an extreme sport and can be fatal, while other sections are not so extreme or difficult. Rafting is also a competitive sport practiced around the world which culminates in a world rafting championship event between the participating nations. The International Rafting Federation, often referred to as the IRF, is the worldwide body which oversees all aspects of the sport. Equipme ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Timber Rafting
Timber rafting is a method of transporting felled tree trunks by tying them together to make rafts, which are then drifted or pulled downriver, or across a lake or other body of water. It is arguably, after log driving, the second cheapest means of transporting felled timber. Both methods may be referred to as timber floating. Historical rafting Unlike log driving, which was a dangerous task of floating separate logs, floaters or raftsmen could enjoy relative comfort of navigation, with cabins built on rafts, steering by means of oars and possibility to make stops. On the other hand, rafting requires wider waterflows. Timber rafts were also used as a means of transportation of people and goods, both raw materials (ore, fur, game) and man-made. Theophrastus (''Hist. Plant.'' 5.8.2) records how the Romans imported Corsican timber by way of a huge raft propelled by as many as fifty masts and sails. This practice used to be common in many parts of the world, especially North A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Raft Guara
A raft is any flat structure for support or transportation over water. It is usually of basic design, characterized by the absence of a hull. Rafts are usually kept afloat by using any combination of buoyant materials such as wood, sealed barrels, or inflated air chambers (such as pontoons), and are typically not propelled by an engine. Rafts are an ancient mode of transport; naturally-occurring rafts such as entwined vegetation and pieces of wood have been used to traverse water since the dawn of humanity. Human-made rafts Traditional or primitive rafts were constructed of wood or reeds. Modern rafts may also use pontoons, drums, or extruded polystyrene blocks. Inflatable rafts up to the 20th century used flotation chambers made of goat- or buffalo-skins, but most now use durable, multi-layered rubberized fabrics. Depending on its use and size, it may have a superstructure, masts, or rudders. Timber rafting is used by the logging industry for the transportation of logs, b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Whitewater
Whitewater forms in a rapid context, in particular, when a river's gradient changes enough to generate so much turbulence that air is trapped within the water. This forms an unstable current that froths, making the water appear opaque and white. The term "whitewater" also has a broader meaning, applying to any river or creek that has a significant number of rapids. The term is also used as an adjective describing boating on such rivers, such as whitewater canoeing or whitewater kayaking. Fast rivers Four factors, separately or in combination, can create rapids: gradient, constriction, obstruction, and flow rate. Gradient, constriction, and obstruction are streambed topography factors and are relatively consistent. Flow rate is dependent upon both seasonal variation in precipitation and snowmelt and upon release rates of upstream dams. Streambed topography Streambed topography is the primary factor in creating rapids, and is generally consistent over time. Increased f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oceanic Dispersal
Oceanic dispersal is a type of biological dispersal that occurs when terrestrial organisms transfer from one land mass to another by way of a sea crossing. Island hopping is the crossing of an ocean by a series of shorter journeys between islands, as opposed to a single journey directly to the destination. Often this occurs via large rafts of floating vegetation such as are sometimes seen floating down major rivers in the tropics and washing out to sea, occasionally with animals trapped on them. Dispersal via such a raft is sometimes referred to as a rafting event. Colonization of land masses by plants can also occur via long-distance oceanic dispersal of floating seeds. History Rafting has played an important role in the colonization of isolated land masses by mammals. Prominent examples include Madagascar, which has been isolated for ~120 million years ( Ma), and South America, which was isolated for much of the Cenozoic. Both land masses, for example, appear to have received ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Storm
A storm is any disturbed state of the natural environment or the atmosphere An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ... of an Astronomy, astronomical body. It may be marked by significant disruptions to normal conditions such as strong wind, tornadoes, hail, thunder and lightning (a thunderstorm), heavy Precipitation (meteorology), precipitation (snowstorm, rainstorm), heavy freezing rain (ice storm), strong winds (tropical cyclone, windstorm), wind transporting some Chemical substance, substance through the Earth's atmosphere, atmosphere such as in a dust storm, among other forms of severe weather. Storms have the potential to harm lives and property via storm surge, heavy rain or snow causing flooding or road impassibility, lightning, wildfires, and vertical and horizont ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hull (watercraft)
A hull is the watertight body of a ship, boat, or flying boat. The hull may open at the top (such as a dinghy), or it may be fully or partially covered with a deck. Atop the deck may be a deckhouse and other superstructures, such as a funnel, derrick, or mast. The line where the hull meets the water surface is called the waterline. General features There is a wide variety of hull types that are chosen for suitability for different usages, the hull shape being dependent upon the needs of the design. Shapes range from a nearly perfect box in the case of scow barges to a needle-sharp surface of revolution in the case of a racing multihull sailboat. The shape is chosen to strike a balance between cost, hydrostatic considerations (accommodation, load carrying, and stability), hydrodynamics (speed, power requirements, and motion and behavior in a seaway) and special considerations for the ship's role, such as the rounded bow of an icebreaker or the flat bottom of a landing craft. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Balsa
''Ochroma pyramidale'', commonly known as the balsa tree, is a large, fast-growing tree native to the Americas. It is the sole member of the genus ''Ochroma''. The tree is famous for its wide usage in woodworking, with the name ''balsa'' being the Spanish word for "raft." A deciduous angiosperm, ''Ochroma pyramidale'' can grow up to 30 m tall, and is classified as a hardwood despite the wood itself being very soft; it is the softest commercial hardwood and is widely used because of its light weight. Biology Balsa on Bota Hill, Limbe Botanical Garden, Cameroon">Limbe_Botanical_Garden.html" ;"title="Bota Hill, Limbe Botanical Garden">Bota Hill, Limbe Botanical Garden, Cameroon A member of the mallow family, ''Ochroma pyramidale'' is native from southern Mexico to southern Brazil, but can now be found in many other countries (Papua New Guinea, Indonesia, Thailand, Solomon Islands). It is a pioneer plant, which establishes itself in clearings in forests, either man-made ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Float (nautical)
Floats (also called pontoons) are airtight hollow structures, similar to pressure vessels, designed to provide buoyancy in water. Their principal applications are in watercraft hulls, aircraft floats, floating pier, pontoon rhinos, pontoon causeways, and marine engineering applications such as salvage. During World War II the United States Navy Civil Engineer Corps developed a modular steel box (pontoon) for the Seabees to use. It was an industrial sized Lego system of pre-drilled pre-cut angle iron and steel plate that could be assembled anywhere for which they became famous. They used them to facilitate amphibious landings. With the pontoons Seabees assembled docks, causeways, and rhinos to whatever size needed. They allowed landings on Sicily where no one thought possible. They ferried Patton across the Rhine and put the Marines ashore on Okinawa. They would be used during the Korean War in the landing at Inchon in 1950 and again in Lebanon during the 1958 Leban ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polystyrene
Polystyrene (PS) is a synthetic polymer made from monomers of the aromatic hydrocarbon styrene. Polystyrene can be solid or foamed. General-purpose polystyrene is clear, hard, and brittle. It is an inexpensive resin per unit weight. It is a poor barrier to oxygen and water vapour and has a relatively low melting point. Polystyrene is one of the most widely used plastics, the scale of its production being several million tonnes per year. Polystyrene can be naturally transparent, but can be colored with colorants. Uses include protective packaging (such as packing peanuts and in the jewel cases used for storage of optical discs such as CDs and occasionally DVDs), containers, lids, bottles, trays, tumblers, disposable cutlery, in the making of models, and as an alternative material for phonograph records. As a thermoplastic polymer, polystyrene is in a solid (glassy) state at room temperature but flows if heated above about 100 °C, its glass transition temperature. I ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inflatable Raft
An inflatable is an object that can be inflated with a gas, usually with air, but hydrogen, helium and nitrogen are also used. One of several advantages of an inflatable is that it can be stored in a small space when not inflated, since inflatables depend on the presence of a gas to maintain their size and shape. Function fulfillment per mass used compared with non-inflatable strategies is a key advantage. Stadium cushions, impact guards, vehicle wheel inner tubes, emergency air bags, and inflatable space habitats employ the inflatable principle. Inflation occurs through several strategies: pumps, ram-air, blowing, and suction. Although the term ''inflatable'' can refer to any type of inflatable object, the term is often used in boating to specifically refer to inflatable boats. Types High-pressure vs. low-pressure A distinction is made between high-pressure and low-pressure inflatables. In a high-pressure inflatable, structural limbs like pillars and arches are built out ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wood
Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin that resists compression. Wood is sometimes defined as only the secondary xylem in the stems of trees, or it is defined more broadly to include the same type of tissue elsewhere such as in the roots of trees or shrubs. In a living tree it performs a support function, enabling woody plants to grow large or to stand up by themselves. It also conveys water and nutrients between the leaves, other growing tissues, and the roots. Wood may also refer to other plant materials with comparable properties, and to material engineered from wood, or woodchips or fiber. Wood has been used for thousands of years for fuel, as a construction material, for making tools and weapons, furniture and paper. More recently it emerged as a feedstock for the productio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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