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Naval architects design Barge s, Boat s, and Ship s for their clients to be for use in commercial, pleasure, military, or other applications. The '''naval architect''' does this based on customer criteria, external criteria, and with the knowledge and style and experience of the designer. The architect is aided by historical knowledge, its formal education or practical experience, software, the experience of the customer and shipbuilder, and, if desired, by the knowledge of specialists. The basic goal of a naval architect is to ensure that the vessel will survive any reasonable Weather when handled with reasonable prudence, and yet still perform its function efficiently. As with any design any particular vessel will be the result of compromises between a number of conflicting goals or elements. The best designs are those that select best compromises for a particular application or offer satisfactory performance in multiple applications. For details of construction techniques see Shipbuilding and Boat Building . Also see Ship Design . CUSTOMER CRITERIA Customer criteria are usually directly linked to the purpose of the ship. For example Deadweight Tonnage and hold volume are measures of the amount of cargo that can be carried and thus linked to the amount of money that the ship receives per transport, while the speed determines the number of transports that can be made in a given amount of time and so determine the amount of income per timeframe. Commonly used criteria
More specific criteria
EXTERNAL CRITERIA External criteria mostly are criteria concerning safety which are imposed mostly by one or more of 3 parties:
Safety Maritime safety is concerned with five major items.
Strength of ships Strength is an issue because most ships can be twisted or suspended between two wave-tops under some conditions. The hull only has to fracture once to fail in service and endanger people. Hulls are customarily overdesigned by a factor of 5 to 7 for the expected stresses, and some ships are overdesigned to 10 or more for extreme service. see also: Strength Of Ships . Stability
In all designs, calculations are performed with cargo and fuel present and absent. Cargo and fuel can act as a ballast, holding the bottom of the ship down. If absent, or placed above waterline, the ship may become topheavy. Ultimate stability calculations have to plan what will happen if the cargo or fuel shifts - or specify that this must never occur. Dynamic ballasting, deliberately altering the location and amount of ballast (usually water), is important for trimming Submarines for diving, cruising and surfacing and for optimising the attitude of landing ships for cruising and beaching. Seakeeping and Freeboard Seakeeping of ships means the way the ship reacts and copes with the wind and waves of open waters. A vessel's hull shape, center of gravity, mass, superstructure and for sailboats its Sail Plan will determine its response to waves in various sea conditions and to wind. On smaller vessels designed for cruising (as opposed to racing) the ability to smoothly handle rough seas and (particularly in sailing vessels) stormy wind conditions without imposing extreme pilot skills or attention is highly desired. Such considerations are of lower importance for racing vessels. Seakeeping is also important for a range of commercial vessels, such as ferries, cruise vessels and off-shore vessels and equipment such as semi-submersible drilling rigs and oil exploration vessels. Fire protection Fire is a major danger onboard of all ships, whether they are made of wood, plastic, or metal. Wood and plastic are combustible by themselves and these ships will burn until the hull of the vessel is weakened so far that it collapses causing the boat to sink. Metal ships usually have a structure which is non-combustible. Fire on board of such vessels (often interior parts or fuel) will often cause the destruction of pipes, valves or portholes through which the sea enters causing the metal ship to sink as well.
Lifesaving equipment Lifesaving equipment can be roughly divided in three categories and is for commercial vessel's prescribed in the International Life-Saving Appliance Code whereas the Maritime And Coastguard Agency provides regulations for pleasure craft.
Means of navigation To avoid Collision s, vessels mount Navigation Light s that permit other vessels to determine the type and relative angle of a vessel, and thus decide if there is a danger of collision. For example, almost all vessels mount a green light on the right, a red light on the left, and a white light in back. If you can see both the green and red light, danger of a collision exists. Large "steamers" must mount red lights on major masts. Ships at anchor hoist a single bright white light (the anchor light). Modern navigational equipment also include GPS , to locate one's position in the trackless ocean. To navigate tight passages in Fog or darkness, and avoid other vessels, Radar is useful. To avoid Shallow s and Reef s, Sonar is also useful. As a practical matter, Celestial Navigation , in which a vessel measures the angles of sun, moon and stars against a clock, is now rarely practiced. It is, however, widely learned, and treasured. EFFICIENCY Broadly, a Commercial Vessel is efficient if the ship's owner can make a profit against the Mortgage and running costs. A pleasure vessel's efficiency is harder to measure, but some boats, such as Racing Yacht s, are every bit as tightly designed as any commercial vessel. Generally, the speed of a vessel is critical to its efficiency. The basic speed of a vessel is its hull speed. For hull speed of displacement (non-planing) vessels, adding more energy to the propulsion has little effect on the speed. For this type of vessel the maximum efficient speed increases as the square root of the mean waterline length divided by the width of the waterline. There are tricks to exceed hull-speed, such as Hydroplaning and Hydrofoil s. All these tricks depend on either removing hull surface from the water, or increasing the effective waterline-length. The basic trick to making a fast hull is to maximize the buoyancy while minimizing the wetted area. This goal directly interferes with instantaneous stability, which prefers a wide, flat hull. Most hulls are clever compromises between stability, buoyancy, and wetted-area. If ultimate stability isn't important, as on inland lakes, a Catamaran is an extremely clever compromise. A catamaran is a boat built on two widely-spaced narrow hulls. It has good instantaneous stability because the hulls are widely spaced. It has a good hull speed because the hulls are narrow, and very long for their width. It is usually comfortable, because it is wide, and can have a wider cabin or cargo area. The trade-off is loss of ultimate stability; most catamarans will capsize at less than 90 degrees of roll. Once capsized a catamaran will tend to invert, from which it may be very difficult to right the vessel. Some catamarans employ a float near the top of the mast to prevent inversion after a capsize. HABITABILITY Vessels intended for cruising and "live aboard" marina use will compromise other factors, typically speed, in the interest of providing a useful and comfortable living environment. Habitability is of prime importance for cruise vessels and comprises items such as cabin lay-out and size and the availability of restaurants, bars, theaters and sporting facilities. RANGE A vessel not provided with sailing capabilities will be limited in its range by its fuel supply and fuel consumption, with fuel consumption being highly dependent upon engine type, hull shape and operating speed. Another factor which has an impact on the range and fuel consumption of ocean-going vessels may be the operating environment (i.e. sea state(s) and weather may be adverse). STYLE Style (or ''fashion'') will reflect attitudes of the time in which an "modern" vessel is designed or may be a homage to an earlier style of vessel design. In some cases the designs of small craft have echoed themes found in Automotive design which in turn were influenced by Aircraft . BEAUTY ]] A vessel has three lines that define most of its beauty. The coaming line is the line of the top of the hull. The silhouette defines how the superstructure looks. The entry line defines how the bow looks. In general, the lines should remind a viewer of each other. A low silhouette is pleasing, and also reduces danger from wind. Most naval architects specialize in one or a few types of vessels; see category Ship types. SEE ALSO EXTERNAL LINKS
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