June 15, 2010

Voith Schneider Propeller

The Voith Schneider Propeller (VSP), also known as a cycloidal drive (CD) is a specialized marine propulsion system (MPS). It is highly maneuverable, being able to change the direction of its thrust almost instantaneously. It is widely used on tugs and ferries; but in recent years, it has also been used in offshore vessels, like Platform Supply Vessels, or even in Offshore Accommodation Vessels. Therefore, it is assumed that it could also be a good propulsion system for a structure for colonizing the ocean.

The advantages that the VSP presents for a seastead can be summarized in these points:

  • The very rapid and precise thrust variation according to cartesian coordinates makes the VSP an ideal propulsion system for efficient dynamic positioning even in extremely rough weather conditions, something of a great help if a solution similar to an MOB (Mobile Offshore Base) is adopted for the seastead.
  • Redundancy of the entire propulsion system, which guarantees full control of the vessel even with only one power train in operation. In a structure accommodating so many residents, like a seastead, this is very important; the same redundancy is desirable in cruise vessels and offshore accommodation vessels.
  • It offers additional roll stabilization, which reduces the roll motion of the seastead (ship shaped) while it is stationary, avoiding the installation of an additional anti-rolling system (like active tanks). It implies that a VSP is a cheaper option compared to a solution of thrusters + active anti-rolling system.
  • The compact design and installation procedure makes the VSP suitable not only for traditional steel vessels but also for concrete barges, although use in concrete barges has not been tried before. The only difference in installation in comparison to a steel vessel is that the steel well flange would be bolted or attached in a different way to the concrete, instead of being welded directly to the hull.

These advantages results in a better solution when compared to traditional thrusters, if the dynamic positioning system is used instead of mooring system for keeping the position of the seastead in the middle of the ocean.

One of the offshore flotel vessels designed in the recent years, the Edda Accommodation, incorporates this propulsion system, precisely due to the advantages listed above.

One of the main reasons that explain why the VSP is being used in offshore vessels is the special features of the Voith-Schneider Propeller that allow very effective roll stabilization. Very rapid thrust variation and generation of very high moments makes it possible to use the VSP for efficient reduction of the ship’s rolling motion, in particular when the ship is stationary or during slow motion along the longitudinal axis, where other systems are limited. This additional function has been proven by Voith in theoretical computations with the University of Hamburg-Harburg, during model tank tests and full scale measurements in the North Sea.

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