Stena Teknik has co-operated with SSPA in Gothenburg in the development project and the construction of the P-MAXair model. The Stena Airmax will be tested in the Gullmars Fjord on the Swedish West Coast, during 2010 when extensive, test programs will be run. The model will be powered by electric motors during these tests.

Air cushion reduces friction :

The concept involves reducing the “wet surface”, i.e. the part of the hull that is in contact with the water, thus slowing down the ship. This is achieved by means of a cavity filled with air in the bottom of the hull. It means that the water is in contact with air instead of steel plate, thus reducing friction. This may seem simple, but a number of phenomena complicate the picture. These include for example internal wave formation in the cavity, which reduces the positive effect. A balance must also be struck between optimising the air pressure to achieve the greatest possible reduction in resistance and, at the same time, minimising air leakage.

The effect of air in full scale :

Testing ship models in test basins has a long history and the technique of scaling up the results from a model to an actual ship is well known. However, Stena’s project is different in that air is also involved. There is little previous experience of the effect of the air on slow speed ships when a model is scaled up to full scale. Building a ship based on normal model tests with a normal sized model would have been very risky. Accordingly, Stena decided to build a 1:12 model, i.e. a 15 m long model, to verify that the results achieved also applied on a larger scale. This has never been done before. Testing the air regulation system will also be an important part of a future project.