The following vessel information shall be available to each Officer:
.1) Principal Dimensions
.2) Subdivision
.3) Tonnage
Propulsion Machinery
.5) Auxiliary Machine
.6) Steering Gear Systems
.7) Anchors
.8) Deck Machinery
.9) Mooring Arrangements
.10) Means of Communication
.11) Manoeuvring Capability
.12) Stability Information
.13) Navigation Instruments
Basic Manoeuvring Characteristics should be well-known of Master for Oil chemical tanker
Manoeuvring information in the form of a pilot card, wheelhouse poster and manoeuvring booklet shall be available to officers and pilots and shall be compiled and posted as appropriate on all vessels.
Squat
When a vessel navigates in shallow water,a reduction of speed and at the same time an increase in draught occurs. This draught increase is called squat effect and is a significant navigational factor.
The effect of squatting depends on the coefficient of the block of the vessel and increases with the square of the speed of the vessel.
The effect of squatting is different for wide or narrow vessels. For large vessels, the increase in thrust is usually the largest forward, while for narrow vessels – the largest in the stern direction.
Generally, vessels with block coefficient greater than 0.7 have an increase in trim forward, whilst vessel with block coefficient of less than 0.7 have an increase in trim aft. The calculations show that the squat effect in confined waters is twice the amount of the squat effect in open waters.
The message is clear:
“Avoid high speed in shallow or confined water”
When navigating in shallow water areas, especially when passing through narrow waters, it is important to always work out how and at what speed to travel safely, taking into account water depth, traction, squatting effect and the fact that waking bows and stern vessels can cause chaos.
When passing through such waters with the pilot on board the captain, make sure that the pilot is familiar with the characteristics of the ship’s squat and whether he understands the significance of this.
When proceeding through such waters, where speed is kept very low to avoid or reduce squat effect, it may be necessary to use tugs to ensure acceptable steering.
If a vessel is destined to a port and, in order to arrive there, has to proceed at deep draught through narrow waters with restricted depth of water, quite exceptional precau- tions may be necessary in order to comply with the requirement for sufficient under-keel clearance, and the navigation should therefore, if possible, be assessed in consultation with the Owners/Manager.
