A monohull is a type of boat having only one hull, unlike multihulled boats which can have two or more individual hulls connected to one another.
A monohull is a type of boat having only one hull, unlike multihulled boats which can have two or more individual hulls connected to one another.
Among the earliest hulls were simple logs, but these were generally unstable and tended to roll over easily. Hollowing out the logs into a dugout canoe doesn't help much unless the hollow section penetrates below the log's center of buoyancy, then a load carried low in the cavity actually stabilizes the craft. Adding weight or ballast to the bottom of the hull or as low as possible within the hull adds stability.
Naval architects place the center of gravity substantially below the center of buoyancy; in most cases this can only be achieved by adding weight or ballast. The use of stones and other weights as ballast can be traced back to the Romans, Phoenicians and Vikings. Modern ships carry tons of ballast in order to maintain their stability; even heavily laden cargo ships use ballast to optimize the distribution of weight.
This is the most prevalent form of waterborne vessel.
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A hull is the watertight body of a ship, boat, or flying boat. The hull may open at the top, or it may be fully or partially covered with a deck. Atop the deck may be a deckhouse and other superstructures, such as a funnel, derrick, or mast. The line where the hull meets the water surface is called the waterline.
A multihull is a boat or ship with more than one hull, whereas a vessel with a single hull is a monohull. The most common multihulls are catamarans, and trimarans. There are other types, with four or more hulls, but such examples are very rare and tend to be specialised for particular functions.
A yacht is a sailing or power vessel used for pleasure, cruising, or racing. There is no standard definition, though the term generally applies to vessels with a cabin intended for overnight use. To be termed a yacht, as opposed to a boat, such a pleasure vessel is likely to be at least 33 feet (10 m) in length and may have been judged to have good aesthetic qualities.
A sailboat or sailing boat is a boat propelled partly or entirely by sails and is smaller than a sailing ship. Distinctions in what constitutes a sailing boat and ship vary by region and maritime culture.
A catamaran is a multi-hulled watercraft featuring two parallel hulls of equal size. It is a geometry-stabilized craft, deriving its stability from its wide beam, rather than from a ballasted keel as with a monohull boat. Catamarans typically have less hull volume, smaller displacement, and shallower draft (draught) than monohulls of comparable length. The two hulls combined also often have a smaller hydrodynamic resistance than comparable monohulls, requiring less propulsive power from either sails or motors. The catamaran's wider stance on the water can reduce both heeling and wave-induced motion, as compared with a monohull, and can give reduced wakes.
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.
A daggerboard is a retractable centreboard used by various sailing craft. While other types of centreboard may pivot to retract, a daggerboard slides in a casing. The shape of the daggerboard converts the forward motion into a windward lift, countering the leeward push of the sail. The theoretical centre of lateral resistance is on the trailing edge of the daggerboard.
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, knockdown, loss of stability due to cargo shifting or flooding, or in high speed boats, from turning too fast.
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.
A ballast tank is a compartment within a boat, ship or other floating structure that holds water, which is used as ballast to provide hydrostatic stability for a vessel, to reduce or control buoyancy, as in a submarine, to correct trim or list, to provide a more even load distribution along the hull to reduce structural hogging or sagging stresses, or to increase draft, as in a semi-submersible vessel or platform, or a SWATH, to improve seakeeping. Using water in a tank provides easier weight adjustment than the stone or iron ballast used in older vessels, and makes it easy for the crew to reduce a vessel's draft when it enters shallower water, by temporarily pumping out ballast. Airships use ballast tanks mainly to control buoyancy and correct trim.
The 18 ft Skiff is considered the fastest class of sailing skiffs. The class has a long history beginning with races on Sydney Harbour, Australia in 1892 and later in New Zealand. The boat has changed significantly since the early days, bringing in new technology as it became available. Because of the need of strength, agility and skill, the class is considered to be the top level of small boat sailing. Worldwide this boat is called the "18 Foot Skiff". It is the fastest conventional non-foiling monohull on the yardstick rating, with a score of 675, coming only third after the Tornado and Inter 20.
A chine in boat design is a sharp change in angle in the cross section of a hull. The chine typically arises from the use of sheet materials as the mode of construction.
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 of a sea turtle. The term can be applied to any vessel; turning turtle is less frequent but more dangerous on ships than on smaller boats. It is rarer but more hazardous for multihulls than for monohulls, because of multihulls are harder to flip in both directions. Measures can be taken to prevent a capsize from becoming a turtle.
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.
A sailing yacht, is a leisure craft that uses sails as its primary means of propulsion. A yacht may be a sail or power vessel used for pleasure, cruising, or racing. There is no standard definition, so the term applies here to sailing vessels that have a cabin with amenities that accommodate overnight use. To be termed a "yacht", as opposed to a "boat", such a vessel is likely to be at least 33 feet (10 m) in length and have been judged to have good aesthetic qualities. Sailboats that do not accommodate overnight use or are smaller than 30 feet (9.1 m) are not universally called yachts. Sailing yachts in excess of 130 feet (40 m) are generally considered to be superyachts.
The Hobie 33 is an American trailerable sailboat that was designed by Hobie Alter and Phil Edwards as one-design racer and first built in 1982. It was the first monohull design for Alter and his company, after establishing their reputations for their lines of surfboards and catamarans
The Alberg 22 is a Canadian trailerable sailboat, that was designed by Swedish-American naval architect Carl Alberg and first built in 1970.
The Sirius 20, 21 and 22 are a family of Canadian trailerable sailboats that was designed by Hubert Vandestadt for cruising and first built in 1976.
The Allegra 24 is an American trailerable sailboat that was designed by Fred Bingham and Lou Nagy and based upon the work of Fred Bingham's son, Bruce Bingham. The boat is intended as a cruiser and was first built in 1984.
The Holder 20 is an American trailerable planing sailboat that was designed by Ron Holder, in collaboration with sailmaker Dave Ulmann, as a one design racer and first built in 1980.
