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S A Malliaroudakis Maritime Ltd Groundings due to Ship Squat Tables and curves (MS Excel) |
Ship Squat has always existed on smaller and slower vessels when underway. These squats have only been a matter of centimetres and thus have been inconsequential. However, from the mid-1960s to the present day, ship size steadily has grown until we have Supertankers of the order of 400,000 tonnes dwt and above. These Supertankers have almost outgrown the Ports they visit, resulting in small static even-keel underkeel clearances of 1.0 to 1.5 metres. Alongside this development in ship size has been an increase in Service Speed on several ships for example Container Ships, where speeds have gradually increased from 16 knots up to about 25 knots. Ship design has seen tremendous changes in the 1980s and 1990s. In Oil Tanker design we have the “Jahre Viking” with a dwt of 564,739t and an LBP of 440m. This is equivalent to the length of 5 football pitches. In August 2006, the biggest container ship to date, the "Emma Maersk", came into service. She has a dwt of 156,907 tonnes, a service speed of 25 kts, an LBP of 381 metres, Br Mld of 56 metres and a draft Mld of 14 metres. In March 2007, she became the longest ship in the shipping industry. As the static underkeel clearances have decreased and as the Service Speeds have increased, ship squats have gradually increased. They can now be of the order of 1.50 to 1.75 metres, which are, of course, by no means inconsequential. To help focus the mind on the dangers of excessive squat, one only has to recall the recent groundings of the twelve vessels listed below: 01/02/08 - Riverdance - Ro-Ro vessel - Shell Flat, Blackpool 02/01/08 - LT Cortesia- Container Ship - Varne Bank, Dover 29/12/06 - Emsland - Cargo Ship Montrose 04/01/06- Desh Rakshak - Oil Tanker - Port Phillip Bay, Melbourne 15/12/05 - Kentucky Highway - Ro-Ro vessel - Parana River 27/07/03 - Eastern Honour 100,000t dwt Tanker - Marsden Pt, NZ 31/03/01 - Don Raul Bulk Carrier - Pulluche Canal 05/02/99 - Napoleon Bonaparte Passenger Liner - Marseilles 02/07/97 - Diamond Grace 260,000t dwt VLCC - Tokyo Harbour 15/02/96 - Sea Empress Supertanker - Milford Haven 07/08/92 - QE2 Passenger Liner - Massachusetts 06/03/87 - Herald of Free Enterprise Ro-Ro vessel - Zeebrugge In the United Kingdom, over the last 40 years the Department for Transport (DfT). have shown their concern by issuing eight “M” notices concerning the problems of ship squat and accompanying problems in shallow water. These alert all Mariners to the associated dangers. It is important for shipboard officers to recognise the signs when a ship has entered shallow water conditions |
