Ships are undoubtedly the heaviest vehicle that human beings use today. It takes about two years to build a big ship. The biggest challenge that await shipbuilders is how to launch them into water.
Ships can’t use tyres to travel on land like an aircraft or a car. Hence several methods are used to launch a ship. If not done carefully, the ship could sink or put the lives of those engaged in launching the ship in danger.
Four types of ship launching methods are commonly used by ship builders. They are:
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Gravitational type launching
In this method, no external power is used from outside to launch a ship. Gravitational force is used to launch the ship in three different ways. They are:
Longitudinal slide
Oiled rollers are used to let the ship slide into water in this method. This can be used for vessels with any tonnage. It is one of the oldest forms of launching systems. However, the area where the ship enters the water has to be large. The ship will enter the area longitudinally and hence it could travel further once it enters the water. This type of launch can be carried out only at a large lake or sea.
Longitudinal roller slider
Instead of oil, steel rollers are used to reduce friction during sliding. This is the only change and the rest of the launch system is same as above. If the ship is built inside a shipyard that is situated onshore, this method is used to take it to water. Same as in oil slide, the area where the ship enters water has to be large enough here too.
Side oiled slideway
This method too uses the same longitudinal slide technique. However, instead of sliding longitudinally, the ship moves sideways. The slideway extends into the water and the ship slides into the water using the slideway. The slideway is oiled to reduce friction. This method is widely used these days. However, the ship could roll hard to one side and this could pose a danger. But this happens rarely. This method can be used even in canals that are narrow and not so deep. Which means, even if the shipyard is away from the shoreline, the ship could use a canal to reach the sea.
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Dry-dock building
Ships are built in dry-docks and are launched by filling the dock with water. In shipyards that are lying close to sea, this method is more convenient. Though the initial investment is high, this type of method is much safer.
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Mechanical launch
The ship is launched into water with the help of machines that range from cranes to helicopter. This method is mainly used for smaller size vessels. Bigger passenger and freight ships can’t be launched through this method. It is not only costly but since mobility and controlling factors of the systems are not up-to the-mark it is also risky. Hence, the method is used rarely.
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Airbag launch
Airbag launch is an innovative and safe technique to launch ships. Air-filled rubber bags are used to take the ship to water. Since the bags are made of reinforced rubber layers, the chance of rupture is rare even in case of large ships. Airbags are inflated to lift up the ship and then with the help of gravity, allow it to slide into the water in a controlled environment. This method can easily be used in all types and sizes of vessels.
The airbags technique can avoid oil pollution caused by other methods. But a large area is needed to carry out this procedure. As in longitudinal slide, the ship enters water longitudinally and will need space to move ahead. Hence, this type of launch is not possible in small canals.
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Source: OnManorama
