A patent slip or marine railway is an inclined plane extending from shoreline into water, featuring a "cradle" onto which a ship is first floated, and a mechanism to haul the ship, attached to the cradle, out of the water onto a slip. The marine railway was invented by a Scot, Thomas Morton, in the early 19th century, as a cheaper alternative to dry docks for marine vessel repairs, in particular below waterline. Larger modern marine railways can handle vessels of thousands of tons.
Invented by shipwright Thomas Morton in 1818, [1] [2] the marine railway offered an alternative to the expensive and time-consuming process of dry docking a ship to perform maintenance or repairs to its hull below waterline. The means and mechanisms over time became various, but always include a "cradle" onto which the ship is floated, and a mechanical mechanism for transferring the ship from water to land up an incline. The destination where work was performed was termed the slip.
Thomas Morton petitioned to extend the duration of his patent in 1832, before a Select committee of the House of Commons. The committee, chaired by the Rt. Hon. Sir George Cockburn, was convened and heard the claim that the slow construction and implementation of such slips required the extension, that the cost of using such slip was one tenth that of using a dry dock, and that by hauling completely onto a clear area it was easier to carry out maintenance. The committee was sympathetic, in particular regarding the small return that Morton had seen during the initial patent period, but ultimately did not support the requested extension. [3]
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The process of slipping a vessel is an inexpensive and straightforward way to take a large vessel out of water for inspection or repair. In tidal harbors and ports, it is normally necessary to wait for high tide. In many cases, it is possible to take the vessel out of the water on one tide, and to make repairs and return it to the water on the next tide.
The first step in use of a patent slip or marine railway system involves a "cradle" being lowered to the bottom of the inclined plane (the slip/slipway), at which point the vessel is moved into position directly above the cradle. The vessel is then moored to the cradle with a number of ropes fore and aft to prevent the vessel from moving in any direction. Large marine railways can handle vessels of 6,000 tons. [4]
Once the vessel is secured to the cradle, the process of hoisting the cradle out of the water and up the slipway begins. Care is taken when the cradle starts to bear the weight of the vessel; if the vessel is not sitting correctly in the cradle, it may damage the cradle or fall from it when fully out of the water. The vessel will usually sit on large wooden wedges when the lift out of the water begins; in the case of larger vessels, they may be temporarily welded to the cradle by divers. When slipway engineers and staff are satisfied that the vessel is correctly cradled, it is hoisted to the top of the slipway, normally beyond the high tide mark.
Originally, men or horses and block and tackle were used to provide mechanical advantage to drag the cradle and vessel up the slipway. With the advent of the steam engine, most marine railways were converted to steam powered operation. For remaining railways in existence, electric or electro-hydraulic winches are the norm.
A typical reason for slipping a vessel is so as to clean and paint it, and in particular, to apply anti-fouling protection to the hull. Other uses include repairs below the waterline, the replacement of propellers, inspections for insurance purposes, or the fitting of cathodic protection. Using a marine railway/patent slip avoids the need to pump out a dry dock, saving time and money. [4]
In addition, a marine railway can substitute for a traditional waterway lock in areas where the terrain is poorly suited to an installation of that kind. This would consist of a railway where two ends each access a body of water, with a dry high point in between. A working example still in use is the Big Chute Marine Railway in Ontario, Canada.
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One of the earliest surviving marine railways is the Creque Marine Railway on Hassel Island in the Caribbean.
The Evans Bay Patent Slip operated in Wellington Harbour, New Zealand from 1873 until 1980, and is now a heritage area. Point Hope Shipyard marine railway Victoria built in the 40's still in use today 1000 ton capacity
A dry dock is a narrow basin or vessel that can be flooded to allow a load to be floated in, then drained to allow that load to come to rest on a dry platform. Dry docks are used for the construction, maintenance, and repair of ships, boats, and other watercraft.
Chatham Dockyard was a Royal Navy Dockyard located on the River Medway in Kent. Established in Chatham in the mid-16th century, the dockyard subsequently expanded into neighbouring Gillingham.
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A slipway, also known as boat ramp or launch or boat deployer, is a ramp on the shore by which ships or boats can be moved to and from the water. They are used for building and repairing ships and boats, and for launching and retrieving small boats on trailers towed by automobiles and flying boats on their undercarriage.
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A ship cradle is a rig designed to hold a ship or boat upright on dry land to allow the vessel to be built or repaired. The vessel is held in place in the cradle by wooden chocks, cables, sand bags or restraining fixtures on the cradle. Ship cradles are made of timber or steel and are usually built adjacent the seashore, lake or river side or on the floor of a dry dock.
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Mort's Dock is a former dry dock, slipway, and shipyard in Balmain, New South Wales, Australia. It was the first dry dock in Australia, opening for business in 1855 and closing more than a century later in 1959. The site is now parkland.
Barry Docks is a port facility in the town of Barry, Vale of Glamorgan, Wales, a few miles southwest of Cardiff on the north shore of the Bristol Channel. The docks were opened in 1889 by David Davies and John Cory as an alternative to the congested and expensive Cardiff Docks to ship coal carried by rail from the South Wales Coalfield. The principal engineer was John Wolfe Barry, assisted by Thomas Forster Brown and Henry Marc Brunel, son of the famous engineer Isambard Kingdom Brunel.
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The Creque Marine Railway, formerly the "St Thomas Marine Repair Facility", is an inclined-plane ship railway on Hassel Island, in the bay of Charlotte Amalie off the coast of St. Thomas Island, in the U.S. Virgin Islands. Its site is below Fort Shipley, within Virgin Islands National Park.
Thomas Morton was a Scottish shipwright and inventor. His most widely known invention is the patent slip.
The Dartmouth Marine Slips was an historic shipyard and marine railway which operated in Dartmouth, Nova Scotia between 1859 and 2003. It was noted for important wartime work during the American Civil War as well as during the Battle of the Atlantic in World War II. After its closure, the site began redevelopment as King's Wharf, a high-rise residential development.
Morton Engineering and Dry Dock Company was a shipbuilding company from Quebec City, Quebec. It was located in the Lower Town area of the city, along the Saint-Charles River. Founded in 1858, the shipyard stayed in operation until 1949, when it constructed its last ship. It built ships for the Royal Navy and Royal Canadian Navy during both world wars. In 1947, the company was renamed St. Lawrence Metal and Marine Works.
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The Evans Bay Patent Slip is a heritage site of the former patent slip located in Evans Bay, in Wellington Harbour in the North Island of New Zealand. The first slipway on the site was commissioned in May 1863 to enable maintenance of the hulls of small vessels. The Wellington Provincial Council was keen to encourage shipping trade by improving facilities in Wellington Harbour and began planning later in 1863 for the construction of a larger patent slip. A concession was granted for the supply, construction and operation of a patent slip on the site. Equipment for the new slip was delivered in 1865 and 1866, but construction was delayed for several years because of a contractual dispute concerning the suitability of the design for the ground conditions. The original suppliers lost a court case and withdrew from the project. The Wellington Patent Slip Company was formed to take over the assets, and construction began in 1871. The Patent Slip was officially opened in March 1873.
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