Importance of Bow Pressure Waves & Hydrodynamics To Avoid Bottom Contact

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Meeting in very narrow channels takes special procedures whereby each vessel is on a steady course and almost pointed at the other, says a recent Nautical Institute report.

Deviations caused by the vessel

While rounding the curve, the up-bound vessel proceeded close to the north bank and then deviated towards the centre of the canal, as shown in A.

Meanwhile, the down-bound vessel approached the curve at a speed of 4.9 knots.

To correct the deviation, the bridge team altered the course to starboard and the Master made a VHF call to the up-bound vessel requesting more room. The up-bound bridge team did not acknowledge the call.

As the two vessels came above each other, as in diagram B, the up-bound vessel was slowly changing course to port, towards the centre of the channel. The down-bound vessel was still positioned close to the channel centre-line and maintained its course.

Conclusion

  • Meeting in a narrow way takes special measures.
  • A successful meeting relies on bow pressure waves and hydrodynamics to keep the vessels apart.
  • The actual location of the meeting was arguably too close to the curve to give the up-bound vessel enough time to stabilise in a correct meeting posture.
  • Once the stern of a vessel becomes close to a bank, hydrodynamic suction will bring the stern even closer and make bottom contact hard to avoid.

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Source: Nautinst

 

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