Feature 1 | CRUISESHIP TECHNOLOGY
Table 1. Queen Victoria - General Particulars.
thus is made up of two components, namely mean bodily sinkage plus a trimming effect. If the ship is on even keel when static, the trimming effect depends on the ship type and block co-efficient (Cb) being considered. Ship squat thus is the overall decrease in
the static underkeel clearance, for’d or aſt as she moves forward through the water. It is not the difference between the draughts when stationary and the draughts when the ship is moving ahead. If the ship moves forward at too great
a speed when she is in shallow water, say where this static even-keel underkeel clearance was 1.0m to 1.5m, then grounding due to excessive squat could occur at the bow or at the stern. For full-form ships such as supertankers
or OBO vessels, grounding will occur generally at the Bow. For fine-form vessels such as passenger ships (similar to the Queen Victoria), the grounding will generally occur at the stern. Tis is assuming that when stationary, they are on even keel. If Cb is > 0.700, then maximum squat
will occur at the bow. If Cb is < 0.700, then maximum squat
will occur at the stern (like the Queen Victoria). If Cb is very near to 0.700, then
maximum squat will occur at the stern, amidships and at the bow. Squat will consist only of mean bodily sinkage. Tere will be no trimming effects. When static, if a ship has trim by the
stern, then when underway she will develop further trim by the stern. Te dynamical trim will add to the static trim. Maximum squat will occur at the stern. Likewise, when static, if a ship has trim
Figure 1 (includes Table 2). Squats for Queen Victoria in open water and confined channels.
to leave a ‘hole’ in the water, this volume of water must return down the sides and under the bottom of the ship. Streamlines of return flow are speeded up under the ship.
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Tey cause a drop in pressure resulting in the ship dropping vertically in the water. As well as dropping vertically, the ship generally trims forward or aſt. Ship squat
by the bow, then when underway she will develop further trim by the bow. Te dynamical trim will add to the static trim. Maximum squat will occur at the bow.
Open or confined When a vessel is operating in water with no breadth restraints such as riverbanks or canal sides, she is said to be in open water conditions. Shipping personnel
The Naval Architect February 2009
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