Ship floodability

In boats and ships unsinkable refers to the property of a watercraft to remain buoyant in vollgelaufenem state, as it has through the use of floats or wood has a lower mean density than water. Unsinkbarkeit plays in the commercial vessels (apart from exceptions such as lifeboats or certain vessels for the fire service ) as opposed to recreational boating not matter, since the effort required in larger hulls increases disproportionately.

Unsinkable boat building

Definition

In the literature the term unsinkable is not clear. In Germany, each boat may be called unsinkable floating in vollgelaufenem state - regardless of whether it may also carry its crew in this case or in the process remains in a normal ( stable ) swimming position to start a safe harbor can. Tests of this buoyancy are not mandatory in Germany. There are even advertised as unsinkable boats that - once filled up with water - swimming under the water surface, so that only remain parts of the superstructure or the mast above water.

In the marine provisions of the French merchant marine ( Marine Marchande ) the term is unsinkable, however precisely defined. A boat is considered here only as unsinkable when it is in its normal, stable floating position remains in fully flooded state, it carries the maximum number of people and not capsize when all people are on the same side of the boat. It also needs to maintain a residual freeboard (as freeboard is that part of the ship's side denotes that rises out of the water ) of 3 % of the hull length and be equivalent to 80 ° of heel self-righting. These properties are tested and certified by Bureau Veritas.

Usual types of floats

Since wood usually does not provide enough buoyancy to reach unsinkable, buoyancy must be distributed in the boat. There are several variations:

• Creating waterproof, air-filled chambers in the hull Benefits: optimum utilization of space, no anchoring problems Cons: loss of function of defective seal or crack the chamber
• Inflatable floats, typically made ​​of PVC (so-called air sacs ) In addition to the available standard sizes Customised products are used to be the hull shape just and to use the space fully. Besides constantly filled floats, there are systems with CO2 cartridges that are (similar to an automatic triggering lifejacket ) inflate on contact with water itself. Advantages: cheap, easy to retrofit Cons: need to be anchored or otherwise secured, loss of function in case of damage
• Use of solid floats from geschlossenblasigem hard foam, polystyrene or similar material Advantages: no leak Beat possible Cons: The buoyancy can be wet ( the foam can a small part of its own weight in water absorb ), must be anchored or otherwise secured.
• Foam filling of cavities ( with a special geschlossenblasigem polyurethane foam ) In this case, no so-called expanding foam or mounting foam are used, because it is porous. Benefits: optimum utilization of space through the foam, no leakage Beat possible, no anchoring problems Cons: can be moist and pull corrosion according to
• The English Captain Frederick Marryat designed in 1820 a lifeboat, which was designed especially buoyant air chambers and Korkeinlagen. The principle is described in more detail in Dodsley 's Annual Register. A model of it is in the National Maritime Museum in Greenwich, London, issued.

Problems in the design and distribution of buoyancy

The amount of buoyancy used must be tailored to the boat, with too little lift the boat is too deep in the water to strong buoyancy, the righting a capsized boat difficult or impossible (due to stabilization in a wrong position ). If the normal swimming position of the boat be guaranteed and after a capsize erecting not be hindered, the lift must be distributed properly to the hull. It is recommended the concentration of buoyancy on the bow and stern, rather than on the sides of the boat, which, for practical purposes ( especially for dinghies ) is often difficult. Facilitates the distribution of buoyancy caused by the use of inner shells in the construction of the boat. The resulting cavities are usually filled with foam in yacht or filled with solid foam and often additionally sealed to prevent wetting of the foam and the odor associated with it.

Sailing in the fully flooded boat

While some yachts are fully maneuverable in vollgelaufenem state, most unsinkable boats can no longer be sailed in the flooded state - or at best on raumen courses ( with wind angle from the back ). Water sloshing around below deck, reinforced the roles of the boat, especially when the wind astern, and may at Wenden, lead jibe or fast rate changes to capsize. Even with the best distribution of buoyancy tend flooded boats for kerning, so for immersing the entire bugs under the water surface.

Unsinkbarkeit as a safety factor

At least with water temperatures that allow longer survival, and with a stable floating position an unsinkable boat is safer than a sinkbares. But at low water temperatures, the survival time is reduced in the water (and thus the fully accrued boat) because of hypothermia risk. Unsinkability a boat does not allow statements about its seaworthiness. In addition, other reasons as flooding can cause a boat must be vacated; so are the most common reasons for the abandonment of a boat fire and stranding. Therefore, the unsinkable yacht makes on appropriate grounds a liferaft not superfluous.

Other meanings

Generally, with unsinkable Titanic often associated, although this was not designed as an unsinkable ship. This myth is based on the buoyancy of the vessel with two compartments flooded (of 16 ), which was reinterpreted in the press for unsinkable. Especially in the press ships or oil rigs are called unsinkable or virtually unsinkable, if due to their size or seaworthiness of a decrease is considered unlikely over again. A recent example of this are modern representations, the sailing ship Pamir have the time counted as unsinkable.

In stock market jargon Unsinkbarkeit is a Ideologem that proclaims a high level of security. Example of this use of the term is the Austrian business newspaper with a separate section " Unsinkable ".