science

Patent slip

Patent slip is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Patent slip rather than just read about it. In short: 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.

Key takeaways

Patent slip belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Patent slip to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Patent slip from memory before moving on to harder problems.

Reference excerpt

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.

History Invented by shipwright Thomas Morton in 1818, 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.

Operation

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. 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.

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 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. 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.

Examples

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.

References

External links

ClydeSite - Article and Photos on Patent Slips Article (1873) on Wellington, New Zealand Patent Slip

Illustrations

"Slipping" a vessel. Illustration of a vessel in profile view over the course of being slipped.

Worked examples

Example 1 — a first encounter with Patent slip

Start with the simplest possible case. Write down what Patent slip claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Patent slip before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Patent slip ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Patent slip

In research: Patent slip appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Patent slip in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Patent slip is common in secondary-school and first-year university syllabi. It links to neighbouring topics Coastal construction, Scottish inventions, Shipbuilding, so understanding it makes those chapters shorter.
In everyday life: Look for Patent slip outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Patent slip in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Patent slip means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Patent slip out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Patent slip in simple terms?

Why does Patent slip matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Patent slip?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Patent slip.