4. Decrease of ship speed

4-1 Calculation method

Decrease of ship speed in actual sea is calculated by solving the following equilibrium equations.

Fig.1. Coordinate system

Forces and moment comprise:

hull resistance in a calm sea condition

hydrodynamic force in oblique motion

propeller thrust

rudder force

added resistance due to winds

added resistance due to waves

Table .1.Beaufort scale

Fig.2. Relation between power and ship speed

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