Course Keeping Aspects in the Design of Fast Deep-V Monohull

The dynamic course stability of modern, fast, deep-V monohulls is still difficult to evaluate by means of purely theoretical methods and model tests with the specific design are generally necessary for new hull designs. There is not enough experimental data available concerning hydrodynamic derivatives and/or manoeuvring characteristics of these kinds of hulls to make it possible to assess even the elementary linear criteria of dynamic course stability. Moreover there does not yet seem to be any reliable theoretically method to calculate the hydrodynamic forces acting on a hull moving rectilinearly with a drift angle or moving around a circular path. Such theoretical methods should also include the contributions of waterjet inlets and other appendages and their interactions with the hull. As a part of the design activity of Fincantieri in the field of fast monohull ferries, an extensive investigation on optimisation of the course keeping ability of such of hulls has been conducted, by combining theory and experimental analysis (PMM tests). Alternative configurations, including minor hull modifications and various fixed and movable appendage configurations, have been evaluated from the course keeping and resistance points of view, resulting in the definition of the best options, which were applied to new designs and have been verified in full-scale trials. The various solutions will be presented and critically discussed in the paper, which also describes the simple theoretical approaches used to account for the 'fin effect' of waterjet inlets and various fin/hull and fin/waterjet interactions.