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naval architecture


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The science of designing ships, submarines, floating docks, yachts, oil rigs for the offshore oil and gas industry, and any craft for use on water. Those qualified to work in this area are known as naval architects.

Until the late 16th century, when plans for constructing new ships began to be drawn on paper, the shipwright's trade was a closely guarded mystique. The necessary expertise was handed down by word of mouth from father to son, as ships were built solely ‘by eye’ using traditional ‘rule-of-thumb’ methods. As a result, improvements in ship construction were introduced only slowly against deep-rooted suspicion and dogmatism.

The work of early naval architects was unscientific and generally followed specifications of shape and scantlings which had been in use for generations. A more scientific approach was attempted by the Swedish naval architect Frederik af Chapman (1721–1808) and others. Chapman wrote a well-regarded treatise on the subject. But it was not until the British engineer William Froude (1810–79) began to study hydrodynamics and ship behaviour in the late 1860s, by undertaking more sophisticated tank testing, that any advance of importance occurred.

Modern naval architecture by Fred M. Walker

Nowadays, naval architects must handle a wide variety of tasks including economic viability studies, conceptual design, strength and stability calculations, as well as supplying the final working drawings for a ship. They may be asked to superintend ships under construction, to make the calculations for launching, and oversee the tests and trials required by a new vessel. The naval architect is also responsible for ensuring that the new ship meets Classification Society regulations as well as the Statutes of International Law as defined by the International Maritime Organization and other authorities. With the increase in complex technology there is now a much greater overlap with marine engineering, to the extent that most universities now offer combined degrees in Naval Architecture and Marine Engineering.

To design a ship, a series of calculations must take place, each defining one aspect of the ship, and in turn absorbing the results of previous calculations. The process has to be repeated several times—a process known as iteration—until the optimum ship design has been achieved. This is known as the design spiral (see illustration), and owing to the intense ‘number crunching’ required, is aided greatly by computers.

Basic Design.

This incorporates the main dimensions of a ship, with estimates of displacement tonnage and cargo-carrying capacity. In this part of the investigation, matters like depth of water in anticipated ports, air draft (maximum height allowable under bridges on the ship's anticipated route) and the owners' requirements for earning ability have to be incorporated into the calculations, and then a preliminary arrangement plan is drawn. The larger a ship, the more efficient is its capacity. For example, by doubling the dimensions of a ship, the cargo capacity increases eightfold, while the fuel consumption is unlikely to be more than double.

Amongst the plans of a ship, which may amount to hundreds, one should find: General arrangement (the internal layout) Lines plan (showing the complex contouring of the hull) Midship section (showing the structural strength at midsection) Structural profile (showing bulkheads and strength members) Rigging plan (giving external fittings and profile) Machinery arrangement Propellers (including bow and stern thrusters, propulsion pods) Stabilizers Electrical layout Cargo capacity or passenger plan Paint linesAs a matter of principle, all plans are drawn with the ship ‘steaming’ to the right-hand side of the paper, so that a rigging plan shows its starboard side. This international convention is vital, as information on the ship may be sent anywhere in the world, and all shipyards and ship repair establishments accept these conventions.

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Subjects: Maritime History.


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