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Inclining Test
An inclining test is a test performed on a ship to determine its stability, lightship weight and the coordinates of its center of gravity. The test is applied to newly constructed ships greater than 24m in length, and to ships altered in ways that could affect stability. Inclining test procedures are specified by the International Maritime Organization and other international associations. The weight of a vessel can be readily determined by reading draughts and comparing with the known hydrostatic properties. The metacentric height (GM), which dominates stability, can be estimated from the design, but an accurate value must be determined by an inclining test. The inclining test is usually done inshore in calm weather, in still water, and free of mooring restraints to achieve accuracy. The GM position is determined by moving weights transversely to produce a known overturning moment in the range of 1-4 degrees if possible. Knowing the restoring properties (buoyancy) of the vessel f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Ship
A ship is a large watercraft that travels the world's oceans and other sufficiently deep waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research, and fishing. Ships are generally distinguished from boats, based on size, shape, load capacity, and purpose. Ships have supported exploration, trade, warfare, migration, colonization, and science. After the 15th century, new crops that had come from and to the Americas via the European seafarers significantly contributed to world population growth. Ship transport is responsible for the largest portion of world commerce. The word ''ship'' has meant, depending on the era and the context, either just a large vessel or specifically a ship-rigged sailing ship with three or more masts, each of which is square-rigged. As of 2016, there were more than 49,000 merchant ships, totaling almost 1.8 billion dead weight tons. Of these 28% were oil tankers, 43% were bulk carriers, and 1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Ship Stability
Ship stability is an area of naval architecture and ship design that deals with how a ship behaves at sea, both in still water and in waves, whether intact or damaged. Stability calculations focus on centers of gravity, centers of buoyancy, the metacenters of vessels, and on how these interact. History Ship stability, as it pertains to naval architecture, has been taken into account for hundreds of years. Historically, ship stability calculations relied on rule of thumb calculations, often tied to a specific system of measurement. Some of these very old equations continue to be used in naval architecture books today. However, the advent of calculus-based methods of determining stability, particularly Pierre Bouguer's introduction of the concept of the metacenter in the 1740s ship model basin, allow much more complex analysis. Master shipbuilders of the past used a system of adaptive and variant design. Ships were often copied from one generation to the next with only minor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Center Of Gravity
In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weighted relative position of the distributed mass sums to zero. This is the point to which a force may be applied to cause a linear acceleration without an angular acceleration. Calculations in mechanics are often simplified when formulated with respect to the center of mass. It is a hypothetical point where the entire mass of an object may be assumed to be concentrated to visualise its motion. In other words, the center of mass is the particle equivalent of a given object for application of Newton's laws of motion. In the case of a single rigid body, the center of mass is fixed in relation to the body, and if the body has uniform density, it will be located at the centroid. The center of mass may be located outside the physical body, as is sometimes the case for hollow or open-shaped objects, such as a horseshoe. In the case of a di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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International Maritime Organization
The International Maritime Organization (IMO, French: ''Organisation maritime internationale'') is a specialised agency of the United Nations responsible for regulating shipping. The IMO was established following agreement at a UN conference held in Geneva in 1948 and the IMO came into existence ten years later, meeting for the first time in 1959. Headquartered in London, United Kingdom, IMO currently has 175 Member States and three Associate Members. The IMO's primary purpose is to develop and maintain a comprehensive regulatory framework for shipping and its remit today includes maritime safety, environmental concerns, legal matters, technical co-operation, maritime security and the efficiency of shipping. IMO is governed by an assembly of members which meets every two years. Its finance and organization is administered by a council of 40 members elected from the assembly. The work of IMO is conducted through five committees and these are supported by technical subcom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Draft (hull)
The draft or draught of a ship's hull is the vertical distance between the waterline and the bottom of the hull ( keel). The draught of the vessel is the maximum depth of any part of the vessel, including appendages such as rudders, propellers and drop keels if deployed. Draft determines the minimum depth of water a ship or boat can safely navigate. The related term air draft is the maximum height of any part of the vessel above the water. The more heavily a vessel is loaded, the deeper it sinks into the water, and the greater its draft. After construction, the shipyard creates a table showing how much water the vessel displaces based on its draft and the density of the water (salt or fresh). The draft can also be used to determine the weight of cargo on board by calculating the total displacement of water, accounting for the content of the ship's bunkers, and using Archimedes' principle. The closely related term "trim" is defined as the difference between the forward and a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Metacentric Height
The metacentric height (GM) is a measurement of the initial static stability of a floating body. It is calculated as the distance between the centre of gravity of a ship and its metacentre. A larger metacentric height implies greater initial stability against overturning. The metacentric height also influences the natural period of rolling of a hull, with very large metacentric heights being associated with shorter periods of roll which are uncomfortable for passengers. Hence, a sufficiently, but not excessively, high metacentric height is considered ideal for passenger ships. Metacentre When a ship heels (rolls sideways), the centre of buoyancy of the ship moves laterally. It might also move up or down with respect to the water line. The point at which a vertical line through the heeled centre of buoyancy crosses the line through the original, vertical centre of buoyancy is the metacentre. The metacentre remains directly above the centre of buoyancy by definition. In the diagr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Sailing Ballast
Ballast is used in ships to provide moment to resist the lateral forces on the hull. Insufficiently ballasted boats tend to tip or heel excessively in high winds. Too much heel may result in the vessel capsizing. If a sailing vessel needs to voyage without cargo, then ballast of little or no value will be loaded to keep the vessel upright. Some or all of this ballast will then be discarded when cargo is loaded. Uses Ballast takes many forms. The simplest form of ballast used in small day sailers is so-called "live ballast", or the weight of the crew. By sitting on the windward side of the hull, the heeling moment must lift the weight of the crew. On more advanced racing boats, a wire harness called a trapeze is used to allow the crew to hang completely over the side of the hull without falling out; this provides much larger amounts of righting moment due to the larger leverage of the crew's weight, but can be dangerous if the wind suddenly dies, as the sudden loss of heeling ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Metacentric Height
The metacentric height (GM) is a measurement of the initial static stability of a floating body. It is calculated as the distance between the centre of gravity of a ship and its metacentre. A larger metacentric height implies greater initial stability against overturning. The metacentric height also influences the natural period of rolling of a hull, with very large metacentric heights being associated with shorter periods of roll which are uncomfortable for passengers. Hence, a sufficiently, but not excessively, high metacentric height is considered ideal for passenger ships. Metacentre When a ship heels (rolls sideways), the centre of buoyancy of the ship moves laterally. It might also move up or down with respect to the water line. The point at which a vertical line through the heeled centre of buoyancy crosses the line through the original, vertical centre of buoyancy is the metacentre. The metacentre remains directly above the centre of buoyancy by definition. In the diagr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Naval Architecture
Naval architecture, or naval engineering, is an engineering discipline incorporating elements of mechanical, electrical, electronic, software and safety engineering as applied to the engineering design process, shipbuilding, maintenance, and operation of marine vessels and structures. Naval architecture involves basic and applied research, design, development, design evaluation (classification) and calculations during all stages of the life of a marine vehicle. Preliminary design of the vessel, its detailed design, construction, trials, operation and maintenance, launching and dry-docking are the main activities involved. Ship design calculations are also required for ships being modified (by means of conversion, rebuilding, modernization, or repair). Naval architecture also involves formulation of safety regulations and damage-control rules and the approval and certification of ship designs to meet statutory and non-statutory requirements. Main subjects The word "vessel" ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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Semi-submersible
Semi-submersible may refer to a self-propelled vessel, such as: *Heavy-lift ship, which partially submerge to allow their cargo (another ship) to float into place for transport *Narco-submarine, some of which remained partially on the surface *Semi-submarine, which cannot fully submerge *Semi-submersible naval vessel, which partially submerges to minimize being observed *Semi-submersible platform A semi-submersible platform is a specialised marine vessel used in offshore roles including as offshore drilling rigs, safety vessels, oil production platforms, and heavy lift cranes. They have good ship stability and seakeeping, better than ..., which is typically transported to a location where it is placed in service * Oil platform, a large structure with facilities for well drilling to explore, extract, store, and process petroleum and natural gas, in deeper water (more than 1,500 metres (4,900 ft)), the semisubmersibles or drillships are maintained at the required drilling lo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |