The loading and discharging of cargo is greatly eased with the help of the proper equipment for its handling. In this chapter we will be discussing the various items of equipment and their uses. Rope slings. Rope slings are constructed by joining the ends of a piece of 25 to 30 mm rope, approximately 10…
Whilst currents/tidal streams have the greatest effect on the movement of vessels, the wind can also affect their movement. The effect of the wind on vessel movement is two fold: Firstly, it will cause an increase or decrease of the speed through the water depending on whether the wind is abaft or forward of the…
The following example is used to explain the procedure to follow: Problem: A vessel steaming at 10 knots wishes to make good a course of 110° (T) from its 1200 position. Find the course to steer allowing for a current setting 170° (T) at 2 knots. Solution: Plot the 1200 position on the chart. Lay…
The following example is used to explain the procedure to follow: Problem: From an observed position at 1200 a vessel steers 110° (T) at 10 knots. The current is setting 350° (T) at 2 knots. Determine the estimated position for 1330. Solution: Plot the true course from the 1200 position. Plot the DR position for…
The best way of demonstrating how to find the set, rate and drift of a current is by using a practical example: Problem: From an observed position at 1200 a vessel steers 110° (T) at 12 knots. At 1330 another fix is obtained. Determine the set rate and drift of the current.. Solution: Plot the…
When plotting courses of vessels and the set of a current/tidal stream, the direction of travel is indicated by arrow heads pointing in the direction of travel. The number of arrow heads differentiate between courses steered, courses made good and the set of a current/tidal stream: One arrow head = the course steered. Two arrow…
The following terminology is used with currents and tidal streams: Set – we speak about the set of the current/tidal stream when referring to its direction of flow. It is expressed in degrees (°). Rate – this is the speed of the current/tidal stream expressed in knots. Drift – this is the distance that a…
Nature of currents. Currents are permanent or seasonal horizontal movement of water flowing in a certain direction and in the oceans caused by differences in temperature, salinity, density and wind. Information concerning their direction and strength is given on charts, in Sailing Directions and various current atlases. The net result is a uniform movement of…
The tide tables are used to determine the heights and times of high and low water at all the major ports in Namibia and South Africa. They are also used to determine the height of tide at anytime during the year at these ports. When using the tables certain parameters concerning the safe depth a…
Highest Astronomical Tide (HAT) and Lowest Astronomical Tide (LAT). These levels are predicted to occur under average meteorological conditions and under any combination of astronomical conditions. They will not be reached every year. They are also not the extreme levels that can be reached, as storm surges and other meteorological conditions can cause considerably higher…