Action/reaction and interaction a case study of a failed overtaking manoeuvre in a confined waterway
Drouin, P.; Bussieres, G. (2009). Action/reaction and interaction a case study of a failed overtaking manoeuvre in a confined waterway, in: Eloot, K. et al. (Ed.) International Conference on Ship Manoeuvring in Shallow and Confined Water: Bank Effects. pp. 141-145
In: Eloot, K.; Vantorre, M. (Ed.) (2009). International Conference on Ship Manoeuvring in Shallow and Confined Water: Bank Effects. Flanders Hydraulics Research/Ghent University/The Royal Institution of Naval Architects: London. ISBN 978-1-905040-46-9. IX, 152 pp., more
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Document type: Conference paper
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| Keywords |
Confined water
Ship maneuvering
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| Abstract |
A container vessel and a tanker made parallel body contact during an overtaking manoeuvre in a narrow dredged channel of the Saint Lawrence River, Canada. Both vessels had relatively low under keel clearance (UKC) and both were under the conduct of an experienced river pilot.
Because one of the vessels had a full VDR and the other vessel had pertinent navigation data from an electronic chart system, the Transportation Safety Board of Canada was able to reconstruct the occurrence in detail. As such, a greater qualitative and quantitative understanding of the hydrodynamic forces at work was achieved.
There were clear indications of hydrodynamic interactions at least 11 minutes before the collision. Bank effect on the overtaking ship was evident as up to 23º of port helm was required (flap-type rudder) to maintain the desired heading. Similarly, the ship being overtaken took a sheer to starboard at the beginning of the manoeuvre. Only a substantial increase in propeller thrust and hard port helm could stabilize that vessel on its intended heading.
In the two and a half minutes before the vessels made contact, the overtaking vessel failed to achieve a speed of greater than 9.1 knots—despite a propeller-pitch setting that should have produced a higher speed. This is a demonstration of the classic “trapping phenomenon” while overtaking in confined waters.
From other research it has been found that the actual pressure zones around vessels in a confined waterway extend much further than the currently accepted 100 m rule of thumb. The occurrence under review adds real-life data that further validates this finding.
The overtaking manoeuvre is understood to be one which presents greater risks due to the prolonged time period the hydrodynamic forces are present as well as their increased strength when overtaking is performed in a confined waterway. The trend towards larger vessels and smaller UKCs will only aggravate this situation. The development of localized quantitative overtaking guidelines for pilots and mariners can be a cost effective risk reduction measure in the operation of a confined waterway. |
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