Draft (hull)

Draft marks on a ship's bow
Load line mark and draft marks on the side of a ship

The draft or draught of a ship's hull is the vertical distance between the waterline and the bottom of the hull (keel). The draught of the vessel is the maximum depth of any part of the vessel, including appendages such as rudders, propellers and drop keels if deployed. Draft determines the minimum depth of water a ship or boat can safely navigate. The related term air draft is the maximum height of any part of the vessel above the water.

The more heavily a vessel is loaded, the deeper it sinks into the water, and the greater its draft. After construction, the shipyard creates a table showing how much water the vessel displaces based on its draft and the density of the water (salt or fresh). The draft can also be used to determine the weight of cargo on board by calculating the total displacement of water, accounting for the content of the ship's bunkers, and using Archimedes' principle.

The closely related term "trim" is defined as the difference between the forward and aft drafts.[1]

  1. ^ "Glossary of Shipbuilding Terms S-Z". US Navy Naval History and Heritage Command. Archived from the original on 2017-04-29. Retrieved 2015-02-15.

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