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A self-righting device is a watercraft that, thanks to its construction, always finds its way back to its normal swimming position - deck up, hull down - even after capsizing . In the case of heeling (inclined position), a righting moment is generated due to the construction.

Capsizing test with a self-righting DGzRS boat of the Eiswette II class


The righting moment is mostly achieved by weights or water tanks inside the ship or by the weight of the keel or the sword . A distinction can be made between dimensionally stable and weight-stable construction methods for all types of ship. Dimensional stability means that a ship does not heel a little below the waterline due to its wide hull . If a dimensionally stable ship capsizes , it remains in this position - that is, the keel up. A weight-stable ship is built slimmer (nautical: slim design), which means: the width is a maximum of a quarter of the ship's length. If such a ship capsizes, it will straighten up again in the normal swimming position at the latest with the next wave. This is done by the heavy ballast built into the keel area .

Self-righting ships in Germany

Keelboat with a view of the
fin keel

In Germany, the rescue cruisers of the DGzRS are known for their self-righting properties. The DGzRS, together with the respective designers, shipyards and shipbuilding research institutes, is in charge of the development of self-righting ships. The most recent example (2008) is the successful capsizing attempt of the rescue cruiser Eiswette during the construction phase. The ship was capsized using a crane. Then it straightened itself up again. An important design feature of the rescue cruiser is that the structure of the rescue cruiser (at full operating weight) has more buoyancy than the hull .

The capabilities of a self-righting ship have been proven in practice in two accidents.

  • The rescue cruiser Adolph Bermpohl capsized in a severe hurricane at the end of February 1967 on its way back from a successful sea rescue. The crew and all those who were rescued tragically fell victim to the sea, and the ship swam upright when found.
  • The rescue cruiser Alfried Krupp capsized at the beginning of January 1995 on its way back from an operation, killing two crew members.

In both cases, the upper control positions of the rescue cruiser were converted into closed ones.

Seagoing monohull sailboats are built as keel boats and are therefore also self- righting .


  • Ulf Kaack : The EISWETTE sea rescue cruiser class - design and construction of the DGzRS rescue units SK30 and SK31. Verlag Peter Kurz, Bremen 2009, ISBN 978-3-927485-93-8 .
  • Hans Georg Prager: Rescuers without fame - The adventure of sea emergency aid. Sutton Verlag, Erfurt 2012, ISBN 978-3-95400-024-1 , pp. 103-113.

Individual evidence

  1. Video of the capsizing attempt
  2. Ulf Kaack: The rescue cruiser class EISWETTE - design and construction of the DGzRS rescue units SK30 and SK31. P. 67.
  3. Hans Georg Prager: Rescuers without fame - The adventure of sea emergency aid. P. 113.

See also