Two cruise liners docked In the middle of the twentieth century, steam power began to give way to diesel power. Diesel engines are smaller, cleaner, far more efficient, and need fewer crew to operate them. Steam had almost completely disappeared by the 1980s. As air travel became convenient and cheap in the 1960s, passengers stopped travelling by sea and the age of the liner came to an end. But as cruise holidays became popular in the 1980s, construction of new, giant cruise liners began.
Parts of a ship
The main part of a ship is its hull, the part that sits in the water. It keeps the ship watertight and forms a strong structure that supports the other parts of the ship and its cargo. Inside the hull are horizontal decks and vertical walls called bulkheads. The parts of a ship above the main deck are called its superstructure. A tug, with part of its hull cut awayCertain types of ship have their own specialized parts. Tugs, for example, are ships specially designed to tow heavy ships, such as oil tankers. They have strong steel hulls and rubber fenders used for pushing ships. Tugs have an extremely powerful engine, which drives a large propeller. On some tugs, the propeller can be steered, changing the direction in which the tug is moving.
A ship's propeller and rudder
Most ships have a diesel engine housed low in the hull, which drives a screw propeller under the stern via a shaft. The propeller blades are large and curved. As they turn, the water around them is sucked in and pushed backwards. This drives the boat fowards. A rudder at the stern steers the ship. Large ships also have small, electrically powered propellers called thrusters for manoeuvring accurately in port.
A view of the control panel in the bridgeShips are controlled from a room high up near the bow, called a bridge. From here, the crew navigate from place to place, using engine and steering controls, and keeping track of their position using charts, satellite navigation systems, lighthouses and buoys. Radar helps to avoid collisions at night or in fog, and sonar warns of shallow water under the ship.
Types of ship
A port scene with a car ferry, seen in cutawayModern ships and boats can be categorized by the the jobs they do. Merchant ships include cruise liners, ferries, cargo ships, and utility ships, such as dredgers and tugs. Military ships include warships and support ships, called auxiliaries. There are also numerous different types of fishing boat and leisure craft, from luxury yachts to sailing dinghies. Small cargoes are carried in standard-sized metal boxes called containers on container ships. Cargoes such as ores, coal and grain are carried by bulk carriers. Oil and other liquids are carried by tankers.
Container ship, with some parts cut awayA modern container shipContainer ships, or “box ships”, are cargo ships that carry their load in lorry-size containers, reusable steel boxes can be moved from ship to lorry without unloading or reloading their contents. To avoid wasted space, the containers are packed on the ship as tightly together as possible. Loading and unloading of container ships can be done only at ports, called container terminals, where there are special cranes. Most manufactured goods are transported from port to port by container ships.
To load a container on to the ship, the crane’s hoist lifts it from a lorry, parked on the quay. A trolley, to which the hoist is attached, then runs along gantry rails out across the ship and lowers the container aboard. The crane itself runs on two rails so it can move along the quay and position the containers in different parts of the ship.
Oil tankers are the largest forms of transport in the world. They are specially designed to be very strong so they do not break on waves. But they can still break up if blown ashore. A tanker captain must navigate carefully since he cannot bring the ship to a stop in less than 6 kilometres (4 miles). Different ships compared in size The largest modern oil tankers measure up to 380 metres (1250 feet) long, and are known as ultra-large crude carriers (ULCCs). The supreme record-holder was the Knock Nevis, previously called the Jahre Viking and the Seawise Giant. Nearly half a kilometre (1640 feet) long, four football pitches could be laid end to end on its deck—with room to spare. The ship itself weighed about the same as a large ocean liner, but with its load of oil the total weight could be up to ten times as much. It was scrapped in December 2009.
Aircraft carriers have a flat main deck, called a flight deck, that forms a runway where aircraft take off and land. Aircraft hangars are on a lower deck. The nuclear-powered Nimitz-class aircraft carriers are the world’s largest carriers. They have a flight deck more than 300 metres (1000 feet) long and provide an operations base for nearly 100 attack aircraft. Carriers have a ship's crew of up to 3000 people.
Consultant: Chris Oxlade
See also in Geography