Surviving clay tablets and containers record the use of waterborne vessels as early as 4000 bce. Boats are still vital aids to movement, even those little changed in form during that 6,000-year history. The very fact that boats may be quite easily identified in illustrations of great antiquity shows how slow and continuous had been this evolution until just 150 years ago. And though that was the time when steam propulsion became predominant, it never was anywhere universal in local transport. Because some solutions to the problem of providing water transport were eminently successful and efficient several millennia ago, there are a number of boats still in use whose origins are lost in prehistory.
Oars and sails
‘A ship in a field’ is a somewhat – ‘Now I will set forth / the names of ships’ – unexpected idea, but it is strongly reminiscent constitute a list signal, indicating that a list is of the stone ships in Scandinavian burial sites. About to begin, and an organizing principle, ‘A ship in the field’ in the mythical realm telling. On board ships -AC, 3-phase power is preferred over DC as it gives more power for the same size - 3-phase is preferred over single phase as it draws more power and in the event of failure of one phase, other 2 can continue working Power Distribution on Ships: Th ship’s pow distribution system consists of different components for.
Early rowed vessels
The earliest historical evidence of boats is found in Egypt during the 4th millennium bce. A culture nearly completely riparian, Egypt was narrowly aligned along the Nile, totally supported by it, and served by transport on its uninterruptedly navigable surface below the First Cataract (at modern-day Aswān). There are representations of Egyptian boats used to carry obelisks on the Nile from Upper Egypt that were as long as 300 feet (100 metres), longer than any warship constructed in the era of wooden ships.
The Egyptian boats commonly featured sails as well as oars. Because they were confined to the Nile and depended on winds in a narrow channel, recourse to rowing was essential. This became true of most navigation when the Egyptians began to venture out onto the shallow waters of the Mediterranean and Red seas. Most early Nile boats had a single square sail as well as one level, or row, of oarsmen. Quickly, several levels came into use, as it was difficult to maneuver very elongated boats in the open sea. Download java pokemon games randomizer. The later Roman two-level bireme and three-level trireme were most common, but sometimes more than a dozen banks of oars were used to propel the largest boats.
Navigation on the sea began among Egyptians as early as the 3rd millennium bce. Voyages to Crete were among the earliest, followed by voyages guided by landmark navigation to Phoenicia and, later, using the early canal that tied the Nile to the Red Sea, by trading journeys sailing down the eastern coast of Africa. According to the 5th-century-bce Greek historian Herodotus, the king of Egypt about 600 bce dispatched a fleet from a Red Sea port that returned to Egypt via the Mediterranean after a journey of more than two years. Cretan and Phoenician voyagers gave greater attention to the specialization of ships for trade.
The basic functions of the warship and cargo ship determined their design. Because fighting ships required speed, adequate space for substantial numbers of fighting men, and the ability to maneuver at any time in any direction, long, narrow rowed ships became the standard for naval warfare. In contrast, because trading ships sought to carry as much tonnage of goods as possible with as small a crew as practicable, the trading vessel became as round a ship as might navigate with facility. The trading vessel required increased freeboard (height between the waterline and upper deck level), as the swell in the larger seas could fairly easily swamp the low-sided galleys propelled by oarsmen. As rowed galleys became higher-sided and featured additional banks of oarsmen, it was discovered that the height of ships caused new problems. Long oars were awkward and quickly lost the force of their sweep. Thus, once kings and traders began to perceive the need for specialized ships, ship design became an important undertaking.
As was true of early wheeled vehicles, ship design also showed strong geographic orientation. Julius Caesar, for one, quickly perceived the distinctive, and in some ways superior, qualities of the ships of northern Europe. In the conquest of Britain and in their encounter with the Batavian area in Holland, Romans became aware of the northern European boat. It was generally of clinker construction (that is, with a hull built of overlapping timbers) and identical at either end. In the Mediterranean, ship design favoured carvel-built (that is, built of planks joined along their lengths to form a smooth surface) vessels that differed at the bow and stern (the forward and rear ends, respectively). In the early centuries, both Mediterranean and northern boats were commonly rowed, but the cyclonic storms found year-round in the Baltic and North Sea latitudes encouraged the use of sails. Because the sailing techniques of these early centuries depended heavily on sailing with a following wind (i.e., from behind), the frequent shifts in wind direction in the north permitted, after only relatively short waits, navigation in most compass directions. In the persistent summer high-pressure systems of the Mediterranean the long waits for a change of wind direction discouraged sailing. It was also more economical to carry goods by ship in the north. With a less absolute dependence on rowing, the double-ended clinker boat could be built with a greater freeboard than was possible in the rowed galleys of the Mediterranean. When European sailors began to look with increasing curiosity at the seemingly boundless Atlantic Ocean, greater freeboard made oceanic navigation more practicable.
The great majority of ships that are neither military vessels nor yachts can be divided into several broad categories: cargo carriers, passenger carriers, industrial ships, service vessels, and noncommercial miscellaneous. Each category can be subdivided, with the first category containing by far the greatest number of subdivisions.
The service ships are mostly tugs or towing vessels whose principal function is to provide propulsive power to other vessels. Most of them serve in harbours and inland waters, and, because the only significant weight they need carry is a propulsion plant and a limited amount of fuel, they are small in size. The towing of massive drilling rigs for the petroleum industry and an occasional oceansalvage operation (e.g., towing a disabled ship) demand craft larger and more seaworthy than the more common inshore service vessels, but oceangoing tugs and towboats are small in number and in size compared with the overwhelmingly more numerous cargo ships.
The word miscellaneous has only small scope here. It is intended to encompass classifications such as icebreakers and research vessels, many of which are owned by government. Neither type need be of large size, since no cargo is to be carried. However, icebreakers are usually wide in order to make a wide swath through ice, and they have high propulsive power in order to overcome the resistance of the ice layer. Icebreakers also are characterized by strongly sloping bow profiles, especially near the waterline, so that they can wedge their way up onto thick ice and crack it from the static weight placed upon it. To protect the hull against damage, the waterline of the ship must be reinforced by layers of plating and supported by heavy stiffeners.
Damage to propellers is also an icebreaking hazard. Propellers are usually given protection by a hull geometry that tends to divert ice from them, and they are often built with individually replaceable blades to minimize the cost of repairing damage. Electric transmission of power between engines and propellers is also common practice, since it allows precise control and an easy diversion of power to another propeller from one that may be jammed by chunks of broken ice.
Research vessels are often distinguished externally by cranes and winches for handling nets and small underwater vehicles. Often they are fitted with bow and stern side thrusters in order to enable them to remain in a fixed position relative to the Earth in spite of unfavourable winds and currents. Internally, research vessels are usually characterized by laboratory and living spaces for the research personnel.
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Industrial ships are those whose function is to carry out an industrial process at sea. A fishing-fleet mother ship that processes fish into fillets, canned fish, or fish meal is an example. Some floating oil drilling or production rigs are built in ship form. In addition, some hazardous industrial wastes are incinerated far at sea on ships fitted with the necessary incinerators and supporting equipment. In many cases, industrial ships can be recognized by the structures necessary for their function. For example, incinerator ships are readily identified by their incinerators and discharge stacks.
Most passenger ships fall into two subclasses, cruise ships and ferries.
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Cruise ships are descended from the transatlantic ocean liners, which, since the mid-20th century, have found their services preempted by jet aircraft. Indeed, even into the 1990s some cruise ships were liners built in the 1950s and ’60s that had been adapted to tropical cruising through largely superficial alterations—e.g., the addition of swimming pools and other amenities to suit warm-latitude cruising areas. However, most cruise ships now in service were built after 1970 specifically for the cruise trade. Since most of them are designed for large numbers of passengers (perhaps several thousand), they are characterized by high superstructures of many decks, and, since their principal routes lie in warm seas, they are typically painted white all over. These two characteristics give them a “wedding cake” appearance that is easily recognizable from great distances. Closer examination usually reveals a large number of motor launches carried aboard for the ferrying ashore of passengers. Many cruise ships have stern ramps, much like those found on cargo-carrying roll-on/roll-off ships, in order to facilitate the transfer of passengers to the launches and to serve as docking facilities for small sporting boats.
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The above features present the principal challenge to the cruise-ship designer: providing the maximum in safety, comfort, and entertainment for the passengers. Thus, isolation of machinery noise and vibration is of high importance. Minimizing the rolling and pitching motions of the hull is even more important—no extreme of luxury can offset a simple case of seasickness. Since cruising is a low-speed activity, propulsive power is usually much lower than that found in the old ocean liners. On the other hand, electrical power is usually of much greater magnitude, mainly because of demands by air-conditioning plants in tropical waters. The typical large cruise ship built since 1990 is powered by a “central station” electric plant—i.e., an array of four or more identical medium-speed diesel engines driving 60-hertz alternating-current electrical generators. This electrical plant supplies all shipboard power needs, including propulsion. Since all power flows from a single source, propulsion power can be readily diverted to meet increased air-conditioning loads while the ship is in port.