Hull resistance is the amount of force required to tow a vessel through calm water at a given speed and condition of load.
Bare hull resistance is the resistance of a hull, without appendages or penetrations, under tow. This resistance comes from a number of components, such as energy expended forming waves and friction between the hull and water. The amount of power required to overcome this resistance can be determined by;
where P = power (kilowatts), R = resistance (kN), and V is velocity (m/s). Thus, it is useful to determine the value of RT for the range of velocities the vessel will operate within.