Slipways in the harbour of South Shields, Tyne and Wear, England
A slipway is a ramp on the shore by which ships and other vessels can be moved to and from the water. They are used for repairing and sometimes building ships and boats.
As the word "slip" implies, the ships or large boats slide over the ramp. Prior to the move the vessel's keel is coated with grease, which then allows the ship or boat to "slip" off the ramp and progress safely into the water. Slipways are used to launch (newly built) large ships, but can only dry-dock or repair smaller ships.
Pulling large ships against the greased ramp would require too much force. Therefore, for dry-docking large ships, one must use carriages supported by wheels or by roller-pallets. These types of dry-docking installations are called "marine railways". Nevertheless the words "slip" and "slipway" are also used for all dry-docking installations that use a ramp.
The traditional method to gain access to the lower hull of a ship is called careening. In its most primitive form, this was done by beaching a ship, putting it dry at low tide. It is assumed that the ancient Egyptians already practised this. The first artificial means for beaching were found at Carthage. Here, war galleys were drawn up a sloping shore on timber ways or slips.[1] In early 19th century Britain, it was not uncommon to use capstans to pull vessels of up to and slightly over 200 tons up on the beach.[2]
In about 1800, it was also quite usual for shipyards to haul ships up on a building slip. In 1832, George Graham, a shipbuilder in Harwich, made some statements about the old way of hauling ships up on his regular building slip, using the materials he already had for launching vessels. It involved capstans, laying ways, and use of a tempororary cradle. It was a costly operation with high risk of damaging a vessel.[3]
Mr. Graham dragged up ships of up to 1,000 tons.[3] The Royal Navy went further and drew up frigates of war.[4] It even experimented by hauling up the ship of the lineKent of over 1,800 ton.[2] Therefore, in about 1820, every ship could be hauled up on a regular building slip.
The total cost of dragging up Kent was £1,436. The cost of bringing a first rate into a dry dock was only £35.[5] However, building a dry dock cost about twenty times as much as constructing a regular (building) slip.[2] Therefore, the cost difference was far less in case prolonged repairs were needed.
In 1819, Thomas Morton of Leith, Scotland introduced the first modern slipway.[6] As it was an invention, he applied for a patent in the United Kingdom and its dependencies and obtained it. The patent led to the name patent slip. In a very extensive 1832 parliamentary discussion about a possible renewal (prolongation) of the patent, it was never called a 'slipway'. It was named 'patent slip', or simply 'slip'.[7] About fifty years later, the patent slip was seen as the first slipway.[6]
The patent slip consisted of rail-bearing 'ways'. These were generally longitudinal balks of timber which carried cast-iron or steel rails. These ways were laid at a suitable inclination on a foundation of rough stone. On these rails, a ship cradle moved on wheels. The permanent cradle had adjustable bilge blocks which allowed it to receive and hold ships of various sizes. Cradle and vessel were then hauled up by hauling gear. At first, this was done by hand, later by steam or hydraulic power.[6]
Terminology
Using a ship cradle was nothing new. Slips that were only used for shipbuilding used them before the slipway was invented. The form of Morton's cradle differed.[8] The launching ways of a building slip that used a cradle consisted of the standing and sliding ways. The standing ways were permanent and were also known as ground ways. The sliding ways or bilge ways formed the bottom of the cradle and were laid on top of the standing ways, separated by a layer of grease.[9]
The upper part of the standing or ground ways, was also referred to as the slipways (plural!).[10] (In an influential work the slipways were equalled to sliding ways.[11] This an error, because the sliding ways were launched together with the ship.[12])
The slipway
A slipway requires substantially more investment than a building slip. It is therefore not economical to use a slipway as a building slip. In spite of this, it was probably done at times.
Other uses
For launching and retrieving small boats, a boat ramp or boat launch may be used. A boat trailer is moved into the water. Traditionally, the boat then slides over the trailer by using a winch. Newer solutions let the boat drive off/on by its own power, or have it float off/on.
From 1925 onwards, modern whaling factory ships have usually been equipped by their designers with a slipway at the stern [13] to haul harpooned whales on deck to be processed by flensers.[14][15][16]
Lifeboat being winched back up its slipway after a launch
To achieve a safe launch of some types of land-based lifeboats in bad weather and difficult sea conditions, the lifeboat and slipway are designed so that the lifeboat slides down a relatively steep steel slip under gravity.
For large ships, slipways are only used in construction of the vessel. They may be arranged parallel or perpendicular to the shore line (or as nearly so as the water and maximum length of vessel allows). On launching, the vessel slides down the slipway on the ways until it floats by itself.[17] The process of transferring the vessel to the water is known as launching and is normally a ceremonial and celebratory occasion. It is the point where the vessel is formally named. At this point the hull is complete and the propellers and associated shafting are in place, but dependent on the depth of water, stability and weight the engines might have not been fitted or the superstructure may not be completed.
In a perpendicular slipway, the ship is normally built with its stern facing the water. Modern slipways take the form of a reinforced concrete mat of sufficient strength to support the vessel, with two "barricades" that extend to well below the water level taking into account tidal variations. The barricades support the two launch ways. The vessel is built upon temporary cribbing that is arranged to give access to the hull's outer bottom, and to allow the launchways to be erected under the complete hull. When it is time to prepare for launching a pair of standing ways are erected under the hull and out onto the barricades. The surface of these ways are greased (Tallow and whale oil were used as grease in sailing ship days).[18] A pair of sliding ways is placed on top, under the hull, and a launch cradle with bow and stern poppets is erected on these sliding ways. The weight of the hull is then transferred from the build cribbing onto the launch cradle. Provision is made to hold the vessel in place and then release it at the appropriate moment in the launching ceremony, these are either a weak link designed to be cut at a signal or a mechanical trigger controlled by a switch from the ceremonial platform.
Some slipways are built so that the vessel is side on to the water and is launched sideways. This is done where the limitations of the water channel would not allow lengthwise launching, but occupies a much greater length of shore. The Great Eastern built by Brunel was built this way as were many landing craft during World War II. This method requires many more sets of ways to support the weight of the ship.
In both cases heavy chains are attached to the ship and the drag effect is used to slow the vessel once afloat until tugboats can move the hull to a jetty for fitting out.
The practice of building on a slipway is dying out with the increasing size of vessels from about the 1970s. Part of the reason is the space requirement for slowing and maneuvering the vessel immediately after it has left the slipway, but the sheer size of the vessel causes design problems, since the hull is basically supported only at its end points during the launch process and this imposes stresses not met during normal operation.
State Street Corporation – State Street Trust Company; Walton Advertising and Printing Company, Boston. (1913). Some ships of the clipper ship era, Their builders, owners, and captains. Boston, MA: Printed for the State Street Trust Company. p.16.
Tønnessen, Johan Nicolay; Johnsen, Arne Odd (1 January 1982) [1959]. The History of Modern Whaling. Translated by Christophersen, R. I. Berkeley: University of California Press. pp.354–355. ISBN9780520039735. Retrieved 12 June 2024. [...] the Lancing, with the first stern slipway, left Sandefjord on 5 June 1925 [...]. [...] In order to train hands in the new form of catching, [...] whaling was carried out that summer off the Congo, and the occasion when the first humpback whale was hauled on to the deck on 14 July 1925 marked a milestone in the history of whaling. [...] the Lancing's operations in 1925–6 were to prove of decisive importance in the transition to the new epoch of whaling.
Cioc, Mark (15 November 2009). "The Antarctic Whale Massacre". The Game of Conservation: International Treaties to Protect the World's Migratory Animals. Series in Ecology and History. Athens, Ohio: Ohio University Press. p.122. ISBN9780821443606. Retrieved 12 June 2024. In 1925, [Petter] Sørlle outfitted the Lancing with a stern slipway–a large trapdoor in the back of the ship that could be opened and closed as needed [...]–as well as a ramp, winch, and whale claw. These tools enabled the crew to grab and hoist a whale into the main deck for flensing and processing before the carcass froze.
Marine Engineering and Shipping Review. Vol.51. Simmons-Boardman Publishing Company. 1946. p.132. The space between the upper (or flensing) deck and the lower (or tank) deck is occupied by the factory plant and machinery. [...] The whales caught by the attendant whale catchers are hauled up a slipway, which lies aft above the two propellers, on to the flensing deck
Small, George L. (1971). The Blue Whale. Columbia University Press. pp.13–. ISBN978-0-231-03288-9. In 1925 Captain Sørlle of Vestfold fitted out a large factory ship, the S.S. Lancing, with a stern slipway: a long sloping ramp that led from a large hole in the stern up to the main deck. With the stern slipway whale carcasses could be hauled up to the deck by a steam winch and flensed even while the ship was on the open sea. Flensers no longer had to work on slippery carcasses floating alongside, a dangerous practice that could plunge them into freezing water.
Nixon, Lewis (1898), "The Building of a ship", Cassier's Magazine, Engineering Illustrated, vol.XIII, The Cassier Magazine Company, London, p.397
Meade, Richard Worsam (1869). A Treatise on Naval Architecture and Ship-building. J.P. Lippincott & Co., Philadelphia. p.420. Retrieved 7 January 2026. [...] the apparatus [...] may be divided into two principal parts–the sliding-ways or slip-ways, which rest on the floor of the slip and present a smooth upper surface; and the cradle or temporary framework which rests and slides upon the slipways, and supports the ship [...].
Searle, Alfred B. (1919), "Concrete Shipbuilding", Concrete and Constructional Engineering, vol.XIV, The Cassier Magazine Company, London, p.523
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