Why do boats have captains?

Boat versus ship bulge

Where does a boat end and where does a ship begin?
Mr. Sontheim, Munich

A ship can carry a boat, but a boat can never carry a ship. This saying reflects one of several definitions of boat and ship, namely that a boat is a seaworthy vehicle less than 50 meters in length, a ship one over 50 meters in length. In everyday use, boats are often referred to as ships, but rarely the other way around. This is particularly evident in sailing boats and sailing ships.

The German Navy defines boats and ships according to the command structure on board: Ships that undertake long voyages need two disciplinary levels (the chief officer and the commander) in order to offer a second point of contact for complaints. There is only the commander on boats. As a result, the German Navy owns only boats - no matter how big - in addition to the sailing training ship "Gorch Fock", the destroyers, the frigates, supply ships and the supply ships.

Submarines, on the other hand, are always referred to as such, regardless of their size. The term underwater ship refers to the area of ​​a ship - or boat - that is under water.

Is there a list of the fastest boats in the world? (not military)
by Helmut Braun

Cruise steamer, sailing boat, container ship or mega yacht - their properties are as varied as the existing types of boats and ships - and of course their superlatives. It can hardly be faster than in a speedboat. Nowadays, the speedsters on the water reach an average of 250 kilometers per hour. The secret of speed: Helicopter or jet motors are built into the speed boats. By the way, the Australian Ken Warby holds the current speed record - and has been since 1978. With his boat "Spirit of Australia" he reached a speed of over 511 kilometers per hour. Despite technical progress, this record has stood for over 38 years - because like any other racing sport, speed boating is not entirely harmless, and many a record aspirant is killed in the process. The fastest luxury yacht is "The World is not Enough", whose top speed is specified as 70 knots, that is just under 130 kilometers per hour.

When I went to sea as a radio officer from 1964 onwards, it was always said: “German ship equals German soil”. Can boat refugees apply for asylum on board German ships?
Sylvester Foecking, Oppenheim

“In the Mediterranean Sea, German merchant ships rescued more than 2,300 boat refugees from distress at sea in the first few months of this year alone, which is their natural duty under maritime law,” says Dr. Max Johns, Managing Director of the Association of German Shipowners. The drama in the Mediterranean is also associated with enormous burdens for ship crews. It also raises legal questions. "The idea that ships sailing under the German flag are quasi extra-territorial area and thus German soil was and is still widespread," says Maritime Lawyer Prof. Henning Jessen from the University of Hamburg: "But that does not coincide with the today's legal opinion. Accordingly, ships are not floating national territory. ”Only the legal system of the flag state applies on board, including official responsibilities. Should a refugee ask for asylum from the captain of one of the 200 or so merchant ships still sailing under the German flag, the UN conventions on international maritime and refugee law apply. Accordingly, the captain has to inform the person rescued on the high seas that he is not authorized to consider the request for asylum or even to decide on it.
Is it possible to hold a submarine in a floating position without aids such as a machine or a down rudder?
Ralf Guddei, Bremen, by email

When a submarine dives, its dive cells are opened. The air present there escapes and is replaced by specifically heavier seawater.
In order to keep it in suspension underwater, the ship's technical officer must observe the principle of Archimedes of Syracuse. Accordingly, the buoyancy of a body in a medium corresponds to the weight of the medium it displaces. "In fact, the floating of a submarine is practiced every now and then," says frigate captain Arndt Henatsch from the German Navy training center for submarines in Eckernförde. “That requires a lot of instinct.” Because the steering state, in which the weight of the water displaced by the submarine exactly corresponds to its own weight, is influenced by many factors: The water pressure, for example, which increases with increasing depth and thus the volume of the hull decreased; but also by the salt content. "In the Skagerrak, for example, low-salt, lighter water from the Baltic Sea mixes with saltier, heavier North Sea water," says Arndt Henatsch. "In principle, submarines could use these leaps in density and" simply "lay down on a layer of salt."
Does one-way traffic sometimes apply to ships in the Bosphorus?
Ulf Benöhr, by email

Every year around 50,000 ships pass the 31-kilometer-long strait between Europe and Asia Minor; including around 5,500 tankers. The passage has high navigational demands: a bend at Kandilli - the narrowest part of the Bosporus at 698 meters - requires a course change of 45 degrees; at Yeniköy it's even 80 degrees. Here, violent northerly winds can move the ships dangerously close to the Asian shore. In addition, aft currents of up to eight knots impair the flow to the rudder blades and thus the maneuverability. After a few accidents, the Turkish government therefore issued new safety regulations in 2002. Accordingly, ships longer than 200 meters are only allowed to operate during the day. Speed ​​limits also apply. On a case-by-case basis, the district control centers order one-way traffic. "When a storm rages in the Black Sea, for example, the ships in the Bosporus are safer," says an employee of the Istanbul shipping agency Netship. "Then north-south traffic in the direction of the Mediterranean has the right of way." The authorities announce the direction blockages, which often apply for more than 12 hours, mostly at short notice. Waiting times at the entrances to the strait are then the result.
Is there actually a precise definition of the term brackish water?
Sandra Golz, Berlin

The term brackish water is derived from mostly smaller lakes that arise after dike breaches as a result of storm surges. These lakes are called Bracks in Low German; its content as brackish water. The specialist literature knows several limit values ​​for this mixture of salt and fresh water. Interestingly, the term is rarely found in any oceanographic textbook. Limnologists who study inland waters, on the other hand, do use the term. In 1958 the International Limnological Association organized a symposium in Venice and created the “Venice System”, a generally applicable classification for water. The term mixohalin refers to seawater with salt concentrations between 0.5 and 30 per thousand. The researchers gathered in Venice advocated avoiding the term brackish water because of its ambiguity. The Brockhaus, of course, cites exactly these limit values ​​under the keyword brackish water. The “Venice System” has three intermediate stages of mixohaline water. Their average salt content between five and 18 parts per thousand is called mesohaline. These limit values ​​are also used in a more recent textbook on limnology to define the term brackish water.

Bridge: front or back

Why do passenger ships have their bridges in front and cargo ships in the back?
Jannis Schneider, Paderborn

The engineer responsible for ship bridges at the Meyer shipyard in Papenburg, Hermann Hanneken, explains it this way: The captain and his officers must be able to see what is happening in front of their bow. The international shipping organization IMO has therefore stipulated that the water must be visible from the bridge no later than 500 meters or two ship lengths from the bow - whichever is shorter.

On a cruise ship, restaurants, cabins, and halls are often at the same level as the bridge. If this were at the stern, the captain would have a clear view of the pool, but not of what was happening in front of the bow. The front is clearly better visibility, but stormy waves can cause greater damage here. In the case of freighters, the bridge has therefore usually been at the rear, and their superstructures are usually lower, so this is possible. Bridge, crew and engine rooms form a compact area that ensures short distances and is well protected from waves. The captain also has a better eye on the cargo.

Professor Irminger from the Bremen University of Nautical Sciences adds that large car transporters often have the bridge at the bow in order to have a clear view despite the many parking decks. On the first container ship of the new generation with over 13,000 containers, the "Emma Maersk", the bridge is located about midships - at almost 400 meters, the stacked containers restrict the view very much.
Why does the bulbous bow save energy on moving ships, and why is it not found on smaller ships?
Bernhard Löbermann, Augsburg, by email

Bulges in the bow drive up construction costs, mean more space and thus increase frictional resistance. However, it is worth calculating the total drag a ship must overcome. And a large part of this resistance is determined by the waves generated by the ship.

A well-designed bead changes the pressure distribution at the bow and has a positive effect on the height and position of the waves that arise there. It can also improve the flow to the propeller at the stern. The majority of merchant ships today have a bulbous bow.

But there are exceptions: on ships that travel very fast in relation to their size, dynamic buoyancy forces have a significant influence. Here the bulge would interfere. Sports motor boats, for example, therefore do not have a bulbous bow. In addition, each bead is individually designed and is only efficient in certain speed ranges. In most merchant ships, beads can reduce the total drag and thus the required propulsion power by a few percent. That saves fuel, several hundred tons a year for a large container ship.