Ship Squat

Most Deck Officers know about ship squat. Ship Squat is the reduction of the vessels under-keel clearance caused by its relative movement. A vessel tends to squat when making way through the water or riding with the current. How does a ship squat occurs?

A ship, while making way through the water tends to push a mass of water in or on her bow or stern. This water flows back the under and the side of the ship. Thus Ship Squat will cause the vessel to either trim on the bow while moving ahead, or by the aft when moving astern.

In case of a very small ship’s under-keel clearance as featured by tc.gc.ca, let’s say 1.0 or 1.5 meters. Ship Squat should be monitored carefully. At certain speed ship squat could cause the vessel to trim too much either forward or aft depending on the speed of the ship. Which would later on could cause the ship to ground. There are various ways to calculate a ship squat.

Open Waters:

Confined Waters:

Wherein: V = the speed of the vessel through the water in knots; and Cb = the Block Coefficient.

You can calculate the ship squat at different speed, in order to identify the effects of squat on the under-keel clearance of the ship at different speed.

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