How do we know if the squat will result in forward trim, aft trim or no trim ?

In shallow water, the low pressure caused by a ship’s movement is affected by the shape of the ship. Fine-form ships have a bow shape that allows water to flow more easily, causing the low pressure to be located aft of the midship. This results in more squat at the stern and trimming aft.

On the other hand, full-form ships like super-tankers have a bow shape that obstructs water flow, causing the low pressure to be located forward of the midship. This results in more squat at the bow and trimming forward.

The block coefficient of a ship, which is the ratio of its underwater volume to the volume of a box it can fit in, also affects squat. A defining value of 0.7 has been established, where a block coefficient of less than 0.7 causes squat by the stern, a coefficient of more than 0.7 causes squat by the bow, and a coefficient of 0.7 causes bodily squat.

However, this rule only applies when the ship is at even keel in a static position.

If the ship is trimmed by the stern, the maximum squat will be towards the stern, and if the ship is trimmed by the bow, the maximum squat will be towards the bow.

squat

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