ABSTRACT
One of the many natural factors the ship’s navigator must be conscious of when in command of a ship’s steering is the effect of wind. Vessels such as container ships and roll-on, roll-off ships have large freeboards. This means they are more affected by the effect of wind than ships with lower freeboards, such as tankers and gas carriers. This exposed area of the ship is called the windage area, as it is here that the wind has the most prominent effect. The effect that wind has on a vessel is dependent on the location the wind assails the vessel’s freeboard, and on the draught condition of the vessel. For example, a wind with a force of 3–4 on the Beaufort Scale will have a similar effect on a ship in light conditions as a wind with a force of 7–8 on the Beaufort Scale when the vessel is down to her marks. This means wind direction is important for the ship’s navigator. When a vessel is making way at slow speed, manoeuvring, or when sailing near the coastline, wind direction is comparatively easy to establish. It is not nearly as easy to discern when the vessel is out in open sea. The reason being the perceived direction of the wind when standing on deck is relative to the position of the person making the judgement. This is because the true direction of the wind is masked by the vessel’s course. Because manually determining wind direction is so difficult, modern ships are fitted with a piece of equipment called the gyro compass. The gyro compass is linked to a set of repeater compasses via a transmission system. Within the compass is a fast-spinning rotor that weighs between 0.56 kgs (1.25 lbs) and 24 kgs (55 lbs). This is driven thousands of revolutions per minute by an electric motor. Connected to the motor is the spinning wheel, which is called a gyroscope. It is the gyroscope which provides the ship’s navigator with the true wind direction.
