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Initial Stability
Initial stability or primary stability is the resistance of a boat to small changes in the difference between the vertical forces applied on its two sides. The study of initial stability and secondary stability are part of naval architecture as applied to small watercraft (as distinct from the study of ship stability concerning large ships). Determination Initial stability is determined by the angle of tilting on each side of the boat as its center of gravity (CG) moves sideways as a result of the passengers or cargo moving laterally, or as a response to an external force (e.g. wave). The wider the boat and the further its volume is distributed away from its center line (CL), the greater the initial stability. Examples Wide mono-hull small boats such as the jon boat have a great deal of initial stability and allow the occupants to stand upright to engage in fishing activities, and so do narrower small boats such as W-kayaks that feature a twin hull. Very narrow mono-hull ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boat
A boat is a watercraft of a large range of types and sizes, but generally smaller than a ship, which is distinguished by its larger size, shape, cargo or passenger capacity, or its ability to carry boats. Small boats are typically found on inland waterways such as rivers and lakes, or in protected coastal areas. However, some boats, such as the whaleboat, were intended for use in an offshore environment. In modern naval terms, a boat is a vessel small enough to be carried aboard a ship. Boats vary in proportion and construction methods with their intended purpose, available materials, or local traditions. Canoes have been used since prehistoric times and remain in use throughout the world for transportation, fishing, and sport. Fishing boats vary widely in style partly to match local conditions. Pleasure craft used in recreational boating include ski boats, pontoon boats, and sailboats. House boats may be used for vacationing or long-term residence. Lighters are use ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Centre 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 dis ... [...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 inverted, or turtled. For example, if a boat with an LPS of 120 degrees rolls past this point, i.e. its 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 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 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 * Capsize increment * Kayak roll *Metacentric height *Naval architecture * Initial stability ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kayak
A kayak is a small, narrow watercraft which is typically propelled by means of a double-bladed paddle. The word kayak originates from the Greenlandic word '' qajaq'' (). The traditional kayak has a covered deck and one or more cockpits, each seating one paddler. The cockpit is sometimes covered by a spray deck that prevents the entry of water from waves or spray, differentiating the craft from a canoe. The spray deck makes it possible for suitably skilled kayakers to roll the kayak: that is, to capsize and right it without it filling with water or ejecting the paddler. ] Some modern boats vary considerably from a traditional design but still claim the title "kayak", for instance in eliminating the cockpit by seating the paddler on top of the boat ("sit-on-top" kayaks); having inflated air chambers surrounding the boat; replacing the single hull with twin hulls; and replacing paddles with other human-powered propulsion methods, such as foot-powered rotational propellers an ... [...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 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] |
Secondary Stability
Secondary stability, also known as reserve stability, is a boat or ship's ability to right itself at large angles of heel (lateral tilt), as opposed to primary or initial stability, the boat's tendency to stay laterally upright when tilted to low ( The study of initial and secondary stability are part of naval architecture as applied to small watercraft (as distinct from the study of ship stability concerning large ships). A greater lateral width ( beam) and more initial stability decrease the secondary stability- once tilted more than a certain angle the boat is conversely harder to restore to its stable upright position. Other types of ship stability * Primary stability * Tertiary stability (also called inverse stability): Tertiary stability is undesirable as it causes a vessel to remain upside-down. Self-righting watercraft have negative tertiary stability, and no limit of positive stability. For kayak rolling, the stability of an upside-down kayak is also important; low ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beam (nautical)
The beam of a ship is its width at its widest point. The maximum beam (BMAX) is the distance between planes passing through the outer extremities of the ship, beam of the hull (BH) only includes permanently fixed parts of the hull, and beam at waterline (BWL) is the maximum width where the hull intersects the surface of the water. Generally speaking, the wider the beam of a ship (or boat), the more initial stability it has, at the expense of secondary stability in the event of a capsize, where more energy is required to right the vessel from its inverted position. A ship that heels on her ''beam ends'' has her deck beams nearly vertical. Typical values Typical length-to-beam ratios ( aspect ratios) for small sailboats are from 2:1 (dinghies to trailerable sailboats around ) to 5:1 (racing sailboats over ). Large ships have widely varying beam ratios, some as large as 20:1. Rowing shells In watercraft, a racing shell (also referred to as just a ''fine boat'' (UK) or just ' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Racing Shells
In watercraft, a racing shell (also referred to as just a ''fine boat'' (UK) or just ''shell'') is an extremely narrow, and often comparatively long, rowing boat specifically designed for racing or exercise. It is outfitted with long oars, outriggers to hold the oarlocks away from the boat, and sliding seats. The boat's long length and semicircular cross-section reduce drag to a minimum. This makes the boat both fast and unstable. It must be balanced by the rowers to avoid tipping. Being able to balance – or "set" – the boat while putting maximum effort into the oars is therefore an essential skill of sport rowing. History The racing shell evolved from the simple working rowboat. Boats with longer hulls and narrower in beam were developed in the early 19th century specifically for team racing. These dedicated boats were the first boats that could be called racing shells, and they evolved into the highly specialized forms used today. Riggers A narrower boat provides a sharp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kayak
A kayak is a small, narrow watercraft which is typically propelled by means of a double-bladed paddle. The word kayak originates from the Greenlandic word '' qajaq'' (). The traditional kayak has a covered deck and one or more cockpits, each seating one paddler. The cockpit is sometimes covered by a spray deck that prevents the entry of water from waves or spray, differentiating the craft from a canoe. The spray deck makes it possible for suitably skilled kayakers to roll the kayak: that is, to capsize and right it without it filling with water or ejecting the paddler. ] Some modern boats vary considerably from a traditional design but still claim the title "kayak", for instance in eliminating the cockpit by seating the paddler on top of the boat ("sit-on-top" kayaks); having inflated air chambers surrounding the boat; replacing the single hull with twin hulls; and replacing paddles with other human-powered propulsion methods, such as foot-powered rotational propellers an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Secondary Stability
Secondary stability, also known as reserve stability, is a boat or ship's ability to right itself at large angles of heel (lateral tilt), as opposed to primary or initial stability, the boat's tendency to stay laterally upright when tilted to low ( The study of initial and secondary stability are part of naval architecture as applied to small watercraft (as distinct from the study of ship stability concerning large ships). A greater lateral width ( beam) and more initial stability decrease the secondary stability- once tilted more than a certain angle the boat is conversely harder to restore to its stable upright position. Other types of ship stability * Primary stability * Tertiary stability (also called inverse stability): Tertiary stability is undesirable as it causes a vessel to remain upside-down. Self-righting watercraft have negative tertiary stability, and no limit of positive stability. For kayak rolling, the stability of an upside-down kayak is also important; low ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Canoe
A canoe is a lightweight narrow water vessel, typically pointed at both ends and open on top, propelled by one or more seated or kneeling paddlers facing the direction of travel and using a single-bladed paddle. In British English, the term ''canoe'' can also refer to a kayak, while canoes are called Canadian or open canoes to distinguish them from kayaks. Canoes were developed by cultures all over the world, including some designed for use with sails or outriggers. Until the mid-19th century, the canoe was an important means of transport for exploration and trade, and in some places is still used as such, sometimes with the addition of an outboard motor. Where the canoe played a key role in history, such as the Northern United States, Canada, and New Zealand, it remains an important theme in popular culture. Canoes are now widely used for competition and pleasure, such as racing, whitewater, touring and camping, freestyle and general recreation. Canoeing has been ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fishing
Fishing is the activity of trying to catch fish. Fish are often caught as wildlife from the natural environment, but may also be caught from stocked bodies of water such as ponds, canals, park wetlands and reservoirs. Fishing techniques include hand-gathering, spearing, netting, angling, shooting and trapping, as well as more destructive and often illegal techniques such as electrocution, blasting and poisoning. The term fishing broadly includes catching aquatic animals other than fish, such as crustaceans (shrimp/lobsters/ crabs), shellfish, cephalopods (octopus/squid) and echinoderms (starfish/sea urchins). The term is not normally applied to harvesting fish raised in controlled cultivations ( fish farming). Nor is it normally applied to hunting aquatic mammals, where terms like whaling and sealing are used instead. Fishing has been an important part of human culture since hunter-gatherer times, and is one of the few food production activities that ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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