Unsinkability
In boat building and shipbuilding, unsinkability refers to the property of a watercraft to remain buoyant when it is full, as it has a lower average density than water due to the use of buoyancy devices or wood . Unsinkbarkeit plays in the professional shipping (with certain exceptions such as lifeboats or certain vessels for the fire) as opposed to recreational boating not matter because the effort required increases more than proportionally with larger hulls.
Unsinkability in boat building
definition
The term unsinkability has not been clearly explained in the specialist literature . In Germany, every boat that swims in a full state can call itself unsinkable - regardless of whether it can still carry its crew in this case or remains in a normal (stable) swimming position in order to be able to enter a safe harbor. Tests of this swimming ability are not required in Germany. Even boats are advertised as unsinkable which - once filled with water - swim under the surface of the water, so that only parts of the superstructure or the mast remain above water.
In the boat building regulations of the French merchant navy (Marine Marchande), however, the term unsinkability is precisely defined. A boat is only considered unsinkable there if it remains completely flooded in its normal, stable swimming position, carries the maximum number of people and does not capsize if all people are on the same side of the boat. In addition, it must have a residual freeboard (the part of the ship's side that protrudes from the water is referred to as the freeboard) of 3% of the hull length and be self-righting up to 80 ° heel . These properties are tested and certified by Bureau Veritas .
Common types of floats
Since wood usually does not provide enough buoyancy to achieve unsinkability, buoyancy bodies have to be distributed in the boat. There are different variants:
- Creation of watertight, air-filled chambers in the hull
- Advantages: optimal use of space, no anchoring problems
- Disadvantages: Loss of function in the event of poor sealing or cracks in the chamber
- Inflatable floats, typically made of PVC (so-called air bags )
- In addition to the available standard dimensions, custom-made products are used in order to do justice to the shape of the hull and to make full use of the available space. In addition to constantly filled floats, there are systems with CO 2 cartridges which inflate themselves when they come into contact with water (similar to an automatically triggered life jacket ).
- Advantages: cheap, easy to retrofit
- Disadvantages: must be anchored or otherwise secured, loss of function if damaged
- Use of solid floats made of closed-bubble solid foam, polystyrene or a comparable material
- Advantages: no leakage possible
- Disadvantages: The floats can get damp (the foam can absorb a small part of its own weight in water), must be anchored or otherwise secured.
- Foaming of cavities (with special, closed- bubble polyurethane foam )
- So-called construction foam or assembly foam cannot be used here, as this is open-pored.
- Advantages: optimal use of space thanks to the foam, no leaks possible, no anchoring problems
- Cons: can be damp and corrosion lead to
- The English captain Frederick Marryat designed a lifeboat in 1820 that was designed to float with air chambers and cork inlays. The principle is described in more detail in Dodsley's Annual Register. A model of it is on display in the National Maritime Museum in Greenwich, London.
Problems with the design and distribution of buoyancy
The amount of buoyancy equipment used must be precisely tailored to the boat; if there is too little buoyancy, the boat is too deep in the water, and excessive buoyancy can make it difficult or impossible to straighten a capsized boat (by stabilizing in a wrong position). If the normal swimming position of the boat is to be guaranteed and if the righting is not hindered after capsizing, the buoyancy must be correctly distributed over the hull. It is recommended to concentrate the buoyancy on the bow and stern instead of on the sides of the boat, which (especially with dinghies ) is often difficult for practical reasons. The distribution of buoyancy is made easier by the use of inner shells when building the boat. In yacht construction, the resulting cavities are usually filled with foam or filled with solid foam and often additionally sealed to prevent the foam from becoming damp and the associated odor nuisance.
Sailing in a completely flooded boat
While some yachts remain fully maneuverable when full, most unsinkable boats can no longer be sailed when flooded - or at best on clear courses (with the wind at an angle from behind). Water that sloshes below deck increases the rate of roll of the boat, especially in aft winds, and can capsize when tacking , jibing or changing course quickly. Even with the best distribution of buoyancy, flooded boats tend to undercut, i.e. the entire bow is submerged under the surface of the water.
Unsinkability as a safety factor
At least at water temperatures that allow a longer survival, and with a stable swimming position, an unsinkable boat is safer than a sinkable one. But at low water temperatures, the survival time in the water (and therefore in a full boat) is reduced due to the risk of hypothermia . The unsinkability of a boat does not allow any statements about its seaworthiness . In addition, for reasons other than water ingress, a boat may have to be abandoned; so the most common reasons for a boat abandonment are fire and stranding. Therefore, the unsinkability of a yacht in certain areas does not make a life raft superfluous.
Other meanings
In general, the Titanic is often associated with unsinkability , although it was not designed as an unsinkable ship. This myth is based on the buoyancy of the ship with two flooded compartments (of a total of 16), which was reinterpreted in the press as unsinkable . In the press in particular, ships or oil rigs are repeatedly referred to as unsinkable or practically unsinkable if sinking is considered unlikely due to their size or seaworthiness. A more recent example of this are modern representations that the sailing ship Pamir was considered unsinkable at the time.
In stock market jargon, unsinkability is an ideologue that proclaims a high level of security. An example of this use of the term is the Austrian business paper with its own section “Unsinkable”.
See also
Individual evidence
- ↑ a b Torsten Moench ( Memento of the original of September 28, 2007 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. : What does unsinkable mean here? . ( Memento of the original from September 28, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Bielefeld 2003. (PDF 90 kB)
- ↑ a b c d e f g Harald Schwarzlose: Small yachts. 2nd Edition. Delius Klasing Verlag, Bielefeld 1997, ISBN 3-7688-0904-8 .
- ↑ a b c d Fridtjof Gunkel: "Unsinkbarkeit - Havarie ohne Not". In: Yacht . No. 9, April 18, 2007. Delius Klasing Verlag, Bielefeld, ISSN 0043-9932 , pp. 28-35.
- ↑ a b Etap Yachting: Unsinkability ( Memento of the original from February 28, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. . current homepage
- ↑ Boats.com: The Truth About Unsinkable Boats ( Memento of the original from September 27, 2007 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. . Internet 2007.
- ^ Dodsley's Annual Register. Volume 62 from 1820 on p. 1372
- ↑ Model of the boat on nmm.ac.uk
- ↑ a b c Schult, Creagh-Osbourne: That is sailing. 8th edition. Delius Klasing Verlag, Bielefeld 1990, ISBN 3-7688-0684-7 .
- ↑ Cinefacts.de: The sinking of the Pamir . current homepage
Web links
- Etap on etapyachting.com - manufacturer of certified unsinkable yachts
