A compartment is a portion of the space within a ship defined vertically between decks and horizontally between bulkheads. It is analogous to a room within a building, and may provide watertight subdivision of the ship's hull important in retaining buoyancy if the hull is damaged. Subdivision of a ship's hull into watertight compartments is called compartmentation.
Bulkheads were known to the ancient Greeks, who employed bulkheads in triremes to support the back of rams. By the Athenian trireme era (500 BC), [1] the hull was strengthened by enclosing the bow behind the ram, forming a bulkhead compartment. Instead of using bulkheads to protect ships against ram attacks, Greeks preferred to reinforce the hull with extra timber along the waterline, making larger ships almost resistant to ramming by smaller ones. [2] Similar to how ships of the Age of Sail allocated more timber to strengthen the hull, so that enemy ships had to be close for cannon fire to be damaging.
Bulkhead watertight compartments were originally invented by the Chinese. These compartments strengthened the junks and slowed flooding in case of holing during the Han and Song dynasties. [3] [4] [5] [6] The wide application of Chinese watertight compartments soon spread to the Europeans through the Indian and Arab merchants. [7] [8] As wood began to be replaced by iron in European ships in the 18th century, new structures, like bulkheads, started to become prevalent. [9]
The economics of early unsinkable passenger ships was scrutinized in an 1882 Scientific American article. [10]
Watertight subdivision limits loss of buoyancy and freeboard in the event of damage, and may protect vital machinery from flooding. Most ships have some pumping capacity to remove accumulated water from the bilges, but a steel ship with no watertight subdivision will sink if water accumulates faster than pumps can remove it. Standards of watertight subdivision assume no dewatering capability, although pumps kept in working order may provide an additional measure of safety in the event of minor leaks. The most common watertight subdivision is accomplished with transverse bulkheads dividing the elongated hull into a number of watertight floodable lengths. Early watertight subdivision tested with hoses sometimes failed to withstand the hydrostatic pressure of an adjoining flooded compartment. Effective watertight subdivision requires these transverse bulkheads to be both watertight and structurally sound. [11]
A ship will sink if the transverse bulkheads are so far apart that flooding a single compartment would consume all the ship's reserve buoyancy. Aside from the possible protection of machinery, or areas most susceptible to damage, such a ship would be no better than a ship without watertight subdivision, and is called a one-compartment ship. A ship capable of remaining afloat when any single watertight compartment is flooded is called a two-compartment ship, but damage destroying the tightness of a transverse bulkhead may cause flooding of two compartments and loss of the ship. A ship able to remain afloat with any two compartments flooded is called a three-compartment ship, and will withstand damage to one transverse bulkhead. [11]
After the Titanic sinking, safety standards recommended spacing transverse bulkheads so no single point of damage would either submerge the end of the upper bulkhead deck or reduce bulkhead deck freeboard to less than 3 inches (7.6 cm). Wartime experience with torpedo damage indicated the typical damage diameter of 35 feet (11 m) defined a practical minimum distance for transverse bulkhead spacing. [11]
Three types of doors are commonly used between compartments. A closed watertight door is structurally capable of withstanding the same pressures as the watertight bulkheads they penetrate, although such doors require frequent maintenance to maintain effective seals, and must, of course, be kept closed to effectively contain flooding. [11]
A closed weathertight door can seal out spray and periodic minor flow over weather decks, but may leak during immersion. These outward opening doors are useful at weather deck entrances to compartments above the main deck. [11]
Joiner doors are similar to doors used in conventional buildings ashore. They afford privacy and temperature control for compartments formed by non-structural bulkheads within the ship's hull. [11]
Compartments are identified by the deck forming the floor of that compartment. Different types of ships have different deck naming conventions. Passenger ships often use letters of the alphabet sequentially down from A deck (the highest) above B deck, and B deck above C deck, and so forth. Another popular naming convention is numbering the main deck 1, the deck below it 2 (or the second deck), and the deck below that the third deck, and so forth. Decks above the main deck may be named, like the bridge deck or poop deck, [12] or they may be numbered upwards from the main deck with a zero prefix that is pronounced "oh": 01 above the main deck, 02 deck above 01, and so forth. [13]
The United States Navy (USN) has used the latter convention in a compartment numbering system since 1949. The USN system identifies each compartment by a four-part code separated by hyphens. The first part of the code represents a numbered deck, the second part of the code is a hull support frame numbered sequentially from the bow, the third part of the code is a number representing compartment position with respect to the ship's centerline, and the fourth part of the code is alphabetic representing the use of that compartment. [13]
The centerline position code is zero for a compartment on the ship's centerline, odd numbers for compartments entirely to starboard of the centerline, and even numbers for compartments entirely to port. For compartments sharing the same deck and forward frame, the first two parts of the code are identical, and the third part of the code is numbered outward from the centerline. For example, four main-deck compartments at frame 90 would be 1-90-1-L inboard and 1-90-3-L outboard on the starboard side of the ship and 1-90-2-L inboard and 1-90-4-L outboard on the port side. [13]
The fourth part of the code is: [14]
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.
Shinano was an aircraft carrier built by the Imperial Japanese Navy (IJN) during World War II, the largest such built up to that time. Laid down in May 1940 as the third of the Yamato-class battleships, Shinano's partially complete hull was ordered to be converted to an aircraft carrier following Japan's disastrous loss of four of its original six fleet carriers at the Battle of Midway in mid-1942. The advanced state of her construction prevented her conversion into a fleet carrier, so the IJN decided to convert her into a carrier that supported other carriers.
The Wayfarer is a wooden or fibreglass hulled fractional Bermuda rigged sailing dinghy of great versatility; it can be used for short 'day boat' trips, for longer cruises and for racing. Over 11,000 have been produced as of 2016.
A bulkhead is an upright wall within the hull of a ship, within the fuselage of an airplane, or a car. Other kinds of partition elements within a ship are decks and deckheads.
A cofferdam is an enclosure built within a body of water to allow the enclosed area to be pumped out or drained. This pumping creates a dry working environment so that the work can be carried out safely. Cofferdams are commonly used for construction or repair of permanent dams, oil platforms, bridge piers, etc., built within water. They also form an integral part of naval architecture.
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Floodability is the susceptibility of a ship's construction to flooding. It also refers to the ability to intentionally flood certain areas of the hull for damage control purposes, or to increase stability, which is particularly important in combat vessels, which often face the possibility of serious hull breach due to enemy action, and which rely on well-trained damage controlmen to equalize and then stop flooding of the hull.
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.
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The free surface effect is a mechanism which can cause a watercraft to become unstable and capsize.
The Olympic-class ocean liners were a trio of British ocean liners built by the Harland & Wolff shipyard for the White Star Line during the early 20th century, named Olympic (1911), Titanic (1912) and Britannic (1914). All three were designated to be the largest as well as most luxurious liners of the era, devised to provide White Star an advantage as regards to size and luxury in the transatlantic passenger trade.
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.
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Shipwrecking is an event that causes a shipwreck, such as a ship striking something that causes the ship to sink; the stranding of a ship on rocks, land or shoal; poor maintenance, resulting in a lack of seaworthiness; or the destruction of a ship either intentionally or by violent weather.
Longitudinal framing is a method of ship construction in which large, widely spaced transverse frames are used in conjunction with light, closely spaced longitudinal members. This method, Isherwood felt, lent a ship much greater longitudinal strength than in ships built in the traditional method, where a series of closely spaced transverse frames are fitted from the keel to the sheer line, with corresponding deck beams, a method that is well suited to support longitudinal planking.
SS William S. Ladd was an American Liberty ship built during World War II, one of the 2,710 type 'EC2-S-C1' ships that carried all kinds and types of dry cargo during the war. She was named for William S. Ladd, an American politician and businessman in Oregon, who twice served as Portland's mayor in the 1850s. The ship's keel was laid on August 29, 1943, and 15 days later, on September 13, the hull was launched. William S. Ladd was fitted out in seven days, and was delivered to the U.S. Navy on September 20. The Navy placed Ladd under charter to Weyerhaeuser Steamship Co.
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