Introduction

The power of the installed propulsion machinery is an indirect measure of the maximum resistance of a vessel. However, the actual amount of this power that can be transformed into thrust to counteract the resistance depends on the efficiency of the propulsion device. For an ACV and an SES, power is also needed to lift the vessel. For an SES, this is about 10% to 20% of the power needed for propulsion. Casanova and Latorre (1992) have collected data on installed horsepower in different types of high-speed marine vehicles (HSMV).

Our focus in this chapter is on resistance and propulsion in calm water. When we consider a ship with constant speed on a straight course in calm water conditions, the balance of forces is simple: the ship resistance must be equal to the thrust delivered by the propulsion unit.

It is most common in model tests and in numerical calculations to consider the ship without an integrated propulsion system. The resistance is therefore evaluated without the presence of the propulsion unit. We will follow this approach. This means the ship resistance RT is defined as the force that is needed to tow the ship in calm water with a constant velocity U on a straight track (of course, the towing unit must not affect the flow around the ship).