Resistance and propulsion tests with a cruise ship model were carried out in seven wave directions. The motivation for the investigation is the powering performance of ships in real sea conditions. The measured data on propulsion efficiency show that in small to moderate waves the losses in propulsive efficiency can to a very high degree be traced back to the lower propeller open water efficiency under higher propeller loading due to the increased ship resistance, whereas the ship motions appear to have only a minor effect. Also the speed-loss of the ship was investigated in head waves. The added resistance in seaways of different wave directions is discussed.


In the framework of the joint research project PerSee (Ship Performance in Seaway) sponsored by the German Federal Ministry for Economic Affairs and Energy (BMWi) the HSVA carried out a large number of measurements on wave added resistance in regular waves in seven wave directions between 180° and 0° of ship heading. In all tests a new towing arrangement was used, which allows the ship model as free motions in all wave headings as possible, but makes it simultaneously possible to measure the towing resistance.

The ship model is towed with a vertical towing pole located in the middle of the ship. A vertical guiding pole at the bow controls the ship model direction. The ship motion components roll, pitch, and heave are completely free. The surge, sway, and yaw -components are restrained with suitably soft springs allowing the cyclic motions of the model in seaway, but keeping it softly on its course and position.

For accurate measurement of wave added resistance the ship model must be able to execute roll motions freely in all wave directions. For this it is important to have the roll axis of the model in the correct height above the baseline, also when the model is connected to the towing system. This is realized with two articulated force balances.

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