What are factors affecting ship’s manoeuvring?

Written by Amit Sharma

Handling characteristics will vary from ship type to ship type and from ship to ship. Handling qualities are determined by ship design, which in turn depends on the ship’s intended function. Typically, design ratios, such as a ship’s length to its beam, determine its willingness to turn. However, desirable handling qualities are achieved only when there is a balance between directional stability and directional instability.

  1. Underwater hull geometry :

Length to beam ratio (UB),  beam to draught ratio (Bm, block coefficient,  prismatic  coefficient  (ratios of the ship’s volume of displacement  against the volume of a rectangular  block or a prism) and location of longitudinal centre of buoyancy, all give an indication  High values of UB are associated with good course directional  stability.
Container ships are likely to have a UB ratio of approximately 8, while harbour tugs, which need to be able to turn quickly and where course stability  is not required, have a value of 2.5 to 3. High values of BIT increase leeway and the tendency for a ship in a beam wind to ‘skate across the sea surface’. A BIT ratio of over 4 is large.

About the author

Amit Sharma

Graduated from M.E.R.I. Mumbai (Mumbai University), After a brief sailing founded this website with the idea to bring the maritime education online which must be free and available for all at all times and to find basic solutions that are of extreme importance to a seafarer by our innovative ideas.

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