ON THE SQUATTING OF SHIPS IN SHALLOW AND RESTRICTED WATER

A.M. Ferguson, R.C. McGregor

Abstract


A major feature of the advances in marine technology is the increasing number, size and speed of ships and, consequently, an increased interest in hydrodynamic problems associated with water restricted in depth and/or lateral extent. The transport of dangerous cargoes and their impact on the benefits of resolving the areas of uncertainty. Experience of 1,104 vessels of different flags and trades during 1978, shows that grounding/stranding is the third most frequent cause of damage[1], An examination of the total expenditure of money and time required to repair the resulting damage shows this category to rank highly in both. Indeed, the total repair cost expended as a result of this cause rank top and account for more than l/5th of the total. Although the shipowner bears a large proportion of the cost of lost revenue, grounding represents a significant cost to underwriters, shipowners and port authorities. The continuous increase in size and draught of vessels in relation to water depth ensures that this situation will continue unless there is a radical development in instrumentation. To limit the risk of grounding it is extremely important to be able to predict which of a vessel's extremities will experience the greatest sinkage and ground. Where the underkeel clearance is low, reasonable accuracy is demanded in order to ensure safety and to avoid unduly reducing the earning capacity of the vessel by overcaution. This requires a sound knowledge of a vessel's tendency to 'squat'.

Keywords


squat; restricted water; shallow water; ship squat

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