Manoeuvring Large Ships in Shallow Water-I

Dr. J. P. Hooft who is a Vice-President of the Netherlands Ship Model Basin at Wageningen, discusses the hydrodynamic forces which act upon a large ship sailing in shallow water. Their effects on the manoeuvrability and control of the ship include a smaller response to a given rudder angle, a shift of the pivoting point aft towards the centre of gravity, a larger turning circle and less reduction in speed when turning. In general a ship becomes more sluggish in shallow water.

Since manoeuvres with large ships are usually only performed in the proximity of harbours while in deep water the ship is kept on course by means of an autopilot, it will be difficult to compare the manoeuvrability of large ships in shallow water with their manoeuvrability in deep water. The influence of water depth on the hydrodynamic characteristics of the ship will therefore be the main subject of the present paper; the consequences of these ship characteristics on manoeuvrability will then be considered. This term ‘manoeuvrability’ is often replaced by ‘controllability’. In this respect a ship is said to be controllable when the navigator is able to manoeuvre the ship with ease in such a way that departures from the anticipated manoeuvre remain within acceptable limits.