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Angle Of Loll
Angle of loll is the state of a ship that is unstable when upright (i.e. has a negative metacentric height) and therefore takes on an angle of heel to either port or starboard. When a vessel has negative metacentric height (GM) ''i.e.'', is in unstable equilibrium, any external force applied to the vessel will cause it to start heeling. As it heels, the moment of inertia of the vessel's waterplane (a plane intersecting the hull at the water's surface) increases, which increases the vessel's BM (distance from the centre of ''B''uoyancy to the ''M''etacenter). Since there is relatively little change in KB (distance from the ''K''eel to the centre of ''B''uoyancy) of the vessel, the KM (distance from ''K''eel to the ''M''etacentre) of the vessel increases. At some angle of heel (say 10°), KM will increase sufficiently equal to KG (distance from the keel to the centre of gravity), thus making GM of vessel equal to zero. When this occurs, the vessel goes to neutral equilibrium, and t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 center of mass#center of gravity, centers of gravity, buoyancy, 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Capsizing
Capsizing or keeling over occurs when a boat or ship is rolled on its side or further by wave action, instability or wind force beyond the angle of positive static stability or it is upside down in the water. The act of recovering a vessel from a capsize is called righting. Capsize may result from broaching, , loss of stability due to cargo shifting or flooding, or in high speed boats, from turning too fast. If a capsized vessel has enough flotation to prevent sinking, it may recover on its own in changing conditions or through mechanical work if it is not stable inverted. Vessels of this design are called self-righting. Small vessels In dinghy sailing, a practical distinction can be made between being knocked down (to 90 degrees; on its beam-ends, figuratively) which is called a capsize, and being inverted, which is called being turtled. Small dinghies frequently capsize in the normal course of use and can usually be recovered by the crew. Some types of dinghy are occasi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weight Distribution
Weight distribution is the apportioning of weight within a vehicle, especially cars, airplanes An airplane or aeroplane (informally plane) is a fixed-wing aircraft that is propelled forward by thrust from a jet engine, propeller, or rocket engine. Airplanes come in a variety of sizes, shapes, and wing configurations. The broad spectr ..., and trains. Typically, it is written in the form ''x''/''y'', where ''x'' is the percentage of weight in the front, and ''y'' is the percentage in the back. In a vehicle which relies on gravity in some way, weight distribution directly affects a variety of vehicle characteristics, including car handling, handling, acceleration, traction (engineering), traction, and component life. For this reason weight distribution varies with the vehicle's intended usage. For example, a Drag racing, drag car maximizes traction at the rear axle while countering the reactionary pitch-up torque. It generates this counter-torque by placing a small amount ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Turtling (sailing)
In dinghy sailing, a boat is said to be turtling or to turn turtle when the boat is fully inverted with the mast pointing down to the lake bottom, riverbed, or seabed. The name stems from the appearance of the upside-down boat, similar to the carapace (top shell) of a sea turtle. at Internet ArchiveHowever, "to turn turtle" means putting a turtle on its back by grabbing it by the flipper, and conversely is used to refer to a vessel that has turned upside down, or which has cast off its crew. A related nautical turtle metaphor is the term Turtleback Deck or "''deck, turtle'' nautical: A term applied to a weather deck that is rounded over from the shell of the ship so that it has a shape similar to the back of a turtle. Used on ships of the whaleback type and on the forward weather deck of torpedo boats." The term can be applied to any vessel; turning turtle is less frequent but more dangerous on ships than on smaller boats.In larger vessels a capsize almost inevitably leads to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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" in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Limit Of Positive Stability
In sailing, the limit of positive stability (LPS) or angle of vanishing stability (AVS) is the angle from the vertical at which a boat will no longer stay upright but will capsize, becoming :wikt:inverted, inverted, or Turtling (sailing), turtled. For example, if a boat with an LPS of 120 Degree (angle), degrees rolls past this point, i.e. its Mast (sailing), mast is already at an angle of 30 degrees below the water, it will continue to roll and be completely upside down in the water. Except for Dinghy sailing, dinghy sailboats and multihulls, most larger sailboats (monohull keelboats) have lead or other heavy materials in their keel at the bottom of their hulls to keep them from capsizing or turtling. The LPS was a part of the Offshore Racing Rules and is used to measure how Ship stability, stable or seaworthy a sailboat is. The modern offshore racing rules published by the International Sailing Federation may also use the measurement. See also *Angle of loll *Capsizing * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluid Statics
Fluid statics or hydrostatics is the branch of fluid mechanics that studies the condition of the equilibrium of a floating body and submerged body "fluids at hydrostatic equilibrium and the pressure in a fluid, or exerted by a fluid, on an immersed body". It encompasses the study of the conditions under which fluids are at rest in stable equilibrium as opposed to fluid dynamics, the study of fluids in motion. Hydrostatics is a subcategory of fluid statics, which is the study of all fluids, both compressible or incompressible, at rest. Hydrostatics is fundamental to hydraulics, the engineering of equipment for storing, transporting and using fluids. It is also relevant to geophysics and astrophysics (for example, in understanding plate tectonics and the anomalies of the Earth's gravitational field), to meteorology, to medicine (in the context of blood pressure), and many other fields. Hydrostatics offers physical explanations for many phenomena of everyday life, such as why ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Angle Of List
The angle of list is the degree to which a vessel heels (leans or tilts) to either port or starboard at equilibrium—with no external forces acting upon it. If a listing ship goes beyond the point where a righting moment will keep it afloat, it will capsize and potentially sink. Listing is caused by the off-centerline distribution of weight aboard due to uneven loading or to flooding. By contrast, roll is the dynamic movement from side to side caused by waves. See also *Angle of loll *Heeling (sailing) *Capsizing *Metacentric height *Ship stability *Ship motions Ship motions are defined by the six degrees of freedom that a ship, boat or any other craft can experience. Reference axes The '' vertical/Z axis'', or ''yaw axis'', is an imaginary line running vertically through the ship and through its ... References {{Ship measurements Engineering concepts Naval architecture Ship measurements ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 diagra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Free Surface
In physics, a free surface is the surface of a fluid that is subject to zero parallel shear stress, such as the interface between two homogeneous fluids. An example of two such homogeneous fluids would be a body of water (liquid) and the air in the Earth's atmosphere (gas mixture). Unlike liquids, gases cannot form a free surface on their own. Fluidized/liquified solids, including slurries, granular materials, and powders may form a free surface. A liquid in a gravitational field will form a free surface if unconfined from above. Under mechanical equilibrium this free surface must be perpendicular to the forces acting on the liquid; if not there would be a force along the surface, and the liquid would flow in that direction. Thus, on the surface of the Earth, all free surfaces of liquids are horizontal unless disturbed (except near solids dipping into them, where surface tension distorts the surface in a region called the meniscus). In a free liquid that is not affected by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List (watercraft)
The angle of list is the degree to which a vessel heels (leans or tilts) to either port or starboard at equilibrium—with no external forces acting upon it. If a listing ship goes beyond the point where a righting moment will keep it afloat, it will capsize and potentially sink. Listing is caused by the off-centerline distribution of weight aboard due to uneven loading or to flooding. By contrast, roll is the dynamic movement from side to side caused by waves. See also *Angle of loll *Heeling (sailing) *Capsizing *Metacentric height *Ship stability *Ship motions Ship motions are defined by the six degrees of freedom that a ship, boat or any other craft can experience. Reference axes The '' vertical/Z axis'', or ''yaw axis'', is an imaginary line running vertically through the ship and through its ... References {{Ship measurements Engineering concepts Naval architecture Ship measurements ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
