The patent slip or marine railway is an

inclined plane An inclined plane, also known as a ramp, is a flat supporting surface tilted at an angle from the vertical direction, with one end higher than the other, used as an aid for raising or lowering a load. The inclined plane is one of the six cla ...

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 dock A dry dock (sometimes drydock or 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, ...

s for

marine vessel Any vehicle used in or on water as well as underwater, including boats, ships, hovercraft and submarines, is a watercraft, also known as a water vessel or waterborne vessel. A watercraft usually has a propulsive capability (whether by sail, o ...

repairs, in particular below waterline. Larger modern marine railways can handle vessels of thousands of tons.

History

Invented by

shipwright Shipbuilding is the construction of ships and other floating vessels. It normally takes place in a specialized facility known as a shipyard. Shipbuilders, also called shipwrights, follow a specialized occupation that traces its roots to befo ...

Thomas Morton in 1818, the marine railway offered an alternative to the expensive and time-consuming process of

ing 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

petition A petition is a request to do something, most commonly addressed to a government official or public entity. Petitions to a deity are a form of prayer called supplication. In the colloquial sense, a petition is a document addressed to some offi ...

ed to extend the duration of his

patent A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A ...

in 1832, before a

Select committee Select committee may refer to: *Select committee (parliamentary system) A select committee is a committee made up of a small number of parliamentary members appointed to deal with particular areas or issues originating in the Westminster system o ...

of the

House of Commons The House of Commons is the name for the elected lower house of the bicameral parliaments of the United Kingdom and Canada. In both of these countries, the Commons holds much more legislative power than the nominally upper house of parliament. T ...

. 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.Stuart Cameron (2005) "The Patent Slip", ClydeSite Magazine, Issue 5, Article 4 (23 March 2003), se

accessed 30 June 2014.

Operation

The process of slipway, 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 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 ...

), 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.Shipbuilding Technology International (UK) journal article, see
/ref> 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 A block and tackle or only tackle is a system of two or more pulleys with a rope or cable threaded between them, usually used to lift heavy loads. The pulleys are assembled to form blocks and then blocks are paired so that one is fixed and on ...

were used to provide

mechanical advantage Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. The device trades off input forces against movement to obtain a desired amplification in the output force. The model for ...

to drag the cradle and vessel up the slipway. With the advent of the

steam engine A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder. This pushing force can be ...

, most marine railways were converted to steam powered operation. For remaining railways in existence, electric or electro-hydraulic winches are the norm.

Reasons for use

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

propeller A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...

s, inspections for insurance purposes, or the fitting of

cathodic protection Cathodic protection (CP; ) is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell. A simple method of protection connects the metal to be protected to a more easily corroded "sacrifi ...

. Using a marine railway/patent slip avoids the need to pump out a dry dock, saving time and money. In addition, a marine railway can substitute for a traditional waterway

lock Lock(s) may refer to: Common meanings *Lock and key, a mechanical device used to secure items of importance *Lock (water navigation), a device for boats to transit between different levels of water, as in a canal Arts and entertainment * ''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 Big Chute Marine Railway is a patent slip at lock 44 (in the township of Georgian Bay) of the Trent-Severn Waterway in Ontario, Canada. It works on an inclined plane to carry boats in individual cradles over a change of height of about . It i ...

in Ontario, Canada.

Examples

One of the earliest surviving marine railways is the

Creque Marine Railway 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 S ...

Hassel Island Hassel Island (also sometimes Hassell Island) is a small island of the U.S. Virgin Islands, a United States territory located in the Caribbean Sea. Hassel Island lies in the Charlotte Amalie harbor just south of Saint Thomas and east of Water ...

in the

Caribbean The Caribbean (, ) ( es, El Caribe; french: la Caraïbe; ht, Karayib; nl, De Caraïben) is a region of the Americas that consists of the Caribbean Sea, its islands (some surrounded by the Caribbean Sea and some bordering both the Caribbean ...

. The Evans Bay Patent Slip operated in Wellington Harbour, New Zealand from 1873 until 1980, and is now a heritage area.

References

External links

{{Commons category, Patent slips
ClydeSite - Article and Photos on Patent Slips
Shipbuilding Coastal construction Scottish inventions