The Italian Navy is currently developing a new hydro-oceanographic vessel for the Mediterranean sea. Among other requirements, the ship is asked to withstand a given sea state during the operations, both measurements and transfer. Specifically the overall operational efficiency at sea in the geographic area mentioned above is of fundamental interest at the present design stage.

To this end, the study has been undertaken adopting a state-of-art methodology and numerical tools to estimate the actual behaviour of the ship at sea over a wide and fine grid of geographic cells belonging to the central Mediterranean sea. In particular, the seakeeping performance in terms of motions and accelerations at given positions on board has been studied using a standard seakeeping code where the incident directional wave spectra have been derived from a state-of-art hindcast wave database developed by some of the authors. The database covers the central Mediterranean sea with cells of 60 nm and the wave data consist of hourly time series over the period 1989-2008.

The main advantage offered by this approach is its capability to distinguish the operational efficiency of the vessel over each geographic cell where the wave climate is well and consistently described by means of meteorological and wave models. The result of the analysis can be used for both design purposes in terms of comparison of the operational efficiency between different designs and for the planning of the operations at sea.

The paper presents the overall methodology, with some hints of the met-ocean ad seakeeping models. The actual application to a preliminary hull shape still under development is presented in details. The operational efficiency computed takes into account the entire set of design speeds, the full set of seakeeping criteria applied at different locations on board and a wide range of ship courses.