Exam Question

### Part (a): Directional Stability and Manoeuvring
#### 1. Concept and Definitions
* **Directional Stability**: This refers to a ship's inherent ability to maintain a straight course without continuous rudder correction. A directionally stable ship, when subjected to an external disturbance (like wind or waves) that causes it to yaw, will naturally tend to return to its original heading. This is analogous to the weathercock stability of an arrow. As per the reference, a ship is stable if a deviation from its set course only increases while an external force is actively causing the deviation.
* **Manoeuvring**: This is the measure of a ship's ability to alter its course and direction effectively. It encompasses actions such as turning, zig-zag manoeuvres, and stopping. There is a fundamental trade-off between directional stability and manoeuvrability. A highly stable vessel is difficult to turn, requiring larger rudder angles and more time to initiate a change in heading. Conversely, a directionally unstable ship is easier to manoeuvre but requires constant, active steering to maintain a straight course.