The best possible seakeeping behaviour for new RoRo vessels

These days, most commercial cargo ships are built with keels reducing its tendency to roll and providing better seakeeping qualities. Wallenius SOL assigned SSPA to perform an assessment of the risk for parametric roll for their new RoRo vessels. A model with new keel solutions was tested at SSPA to evaluate the seakeeping characteristics. 

Parametric roll is a seakeeping phenomenon where large roll angles build up during just a few wave periods. The roll motion, once started, may grow to large amplitudes. The magnitude of the roll angle is limited by roll damping values of hull and appendages. In extreme conditions the large roll angles may result in danger to the ship or its cargo. This phenomenon is referred to as "auto parametrically excited roll motion" which is usually shortened to "parametric roll". The conditions under which parametric roll occurs can be found by model tests.
Recently, the construction of Wallenius SOL´s new RoRo vessels begun at the shipyard in China. These new vessels shall carry sensitive cargoes such as paper and cardboard in sometimes tough conditions. Before the ships were built, SSPA carried out calculations and measurements on how to provide the roll damping.

- “Wallenius SOL has the ambition to make sure that the seakeeping would be the best possible for their vessels and carried out their tests at SSPA, since we can provide them with fact-based decision support. An assessment can be important to validate the choices that the client have, and our experts can also provide with possible recommendation for improvements”, says Per Ekblom, Project Manager, Hydrodynamics at SSPA.

Read more at wallenius-sol.com - How to reduce roll – deep, short bilge keels

Watch the film made by Wallenius SOL, 100 Seconds on Roll Decay Tests