Crew organisation and duties
The crew is everyone working on the ship. They form a team with ranks, so that everybody knows who gives orders and who does which job.
The master (captain) has the full responsibility for the ship, the people and the cargo. The deck department steers, keeps lookout and handles ropes and nets; its leader is the chief officer (first mate). The engine department runs and repairs the engine and machines; its leader is the chief engineer. The radio/communication and catering (cook and steward) staff look after messages and meals. On a small fishing boat one person may do two jobs.
Why ranks? In an emergency there is no time to argue. A clear chain of command saves lives.
Hull maintenance
Maintenance means looking after something so that it keeps working. The hull is the steel body of the ship.
Steel in salt water gets rust (iron plus air and water makes a flaky red-brown layer). Rust makes steel thin and weak. So the crew chip off the rust, put on a rust-proof primer and then paint. Under the water, special anti-fouling paint stops shells and weeds from growing on the hull, because they slow the ship and waste fuel. Small steel blocks called sacrificial anodes are fixed on the hull. Rust attacks them first, so the hull is saved.
Docking and inspection
Some work cannot be done while the ship floats. In a dry dock the ship is floated in, the gate is closed and the water is pumped out. The ship rests on keel blocks. Now workers can reach the bottom.
In dock they clean and repaint the underwater hull, check the propeller and rudder, check the thickness of the steel, and repair damage. A ship goes to dry dock on a regular schedule, for example every few years.
An inspection (survey) is a check by an official or a classification society to see that the ship is safe and follows the rules. If the ship passes, it gets a certificate. A ship without valid certificates may not sail.
Communication
A ship must be able to talk to the shore, to other ships and to rescue centres. The main tools are VHF radio (short range, about 40 to 60 km, for talking to nearby ships and ports), HF radio and satellite phone (long range), flags and lights (signals when radio is not used) and the ship's horn.
Radio waves are invisible waves that carry voice. They go in straight lines, so a tall mast helps. Channel 16 on VHF is the international calling and distress channel. In danger, the crew sends a distress call ("Mayday" three times) with the ship's name and position. A message with a clear order, name and position is the golden rule.
Ensuring safety
Safety on a ship is not a single item; it is a habit. The crew keep a watch: a period of duty. Usually the day is divided into six watches of 4 hours, so every person works 4 hours and rests 8 hours. The lookout watches for other ships, rocks, fishing nets and bad weather. The engine watch checks temperature and pressure.
Other safety jobs: regular drills for fire and abandoning ship, checking lights and signals, keeping logbook records of everything that happens, and obeying the master's orders. Tired people make mistakes, so rest hours matter as much as watch hours.
Try it
In the 3D: in step 2, move the paint slider slowly and count how many parts are still rusty. In step 3 watch the water level fall and ask: why can't we paint the bottom when the ship floats? At home: leave two iron nails, one in water and one dry, for a week. Then paint a third nail and keep it in water. Which one rusts?
Key formulas and definitions
- Chain of command: Master, then Chief Officer (deck) and Chief Engineer (engine), then the crew.
- Watches: 24 hours / 4 hours = 6 watches a day. A person on 4-on, 8-off works 4 hours and rests 8 hours.
- Rust needs: iron + water + air (oxygen). Remove one, or cover the steel with paint, and rust slows down.
Worked examples
1. A ship uses 4-hour watches all day. How many watches are there in 24 hours?
24 / 4 = 6 watches.
2. A sailor stands a 4-hour watch and then rests 8 hours, repeating. How many hours does he work in 24 hours?
One cycle is 4 + 8 = 12 hours. In 24 hours there are 24 / 12 = 2 cycles. Work = 2 x 4 = 8 hours.
3. The underwater hull area is 600 square metres. One litre of anti-fouling paint covers 6 square metres, and two coats are needed. How many litres?
One coat = 600 / 6 = 100 litres. Two coats = 2 x 100 = 200 litres.
Common mistakes
- Thinking the master does all the work. The master is in charge, but every department has its own leader.
- Thinking paint is only for looks. Paint keeps water away from the steel and stops rust.
- Thinking dry dock is the same as a harbour. A harbour keeps the ship afloat; a dry dock lifts the water away so the bottom can be reached.
- Using VHF radio for very long distances. VHF is short range; use HF or satellite for far away.