Service margin - solution of the problem or a problem waiting for solution?

Subiect of the paper is the problem of predicting sea-going ship resistance and/or horsepower in real operating conditions. Attention is drawn first of all to the need and possibility of revising the very much outdated but still used "service margin" method, which consists in adding an arbitrary percentage margin to the value of resistance or horsepower, relatively precisely determined for the calm water conditions. A negative impact in this respect is shown of the generally used delivery-acceptance procedures, where particular importance is attached to the ship propulsion tests on the "measured mile". The need of revising the "service margins" is a consequence of an obvious need for most efficient ships from the technical as well as economic point of view. Secondly, it is a "must" of permanent improving the ship design quality - the adequacy and accuracy of design methods. The work presents the "wave service margin" coefficient models. It is assumed that they may contribute to the necessary rationalization of the procedure of real ship resistance and/or horsepower determination. The work is based on the results of resistance tests of a series of ships designed within the Baltecologicalship project. The tests were carried out in the Chair of Ship Theory and Design of the Faculty of Ocean Engineering and Ship Technology, Gdansk University of Technology.