Displacement

Displacement is the total weight of the volume of water displaced by a vessel's hull, which, according to Archimedes' principle, strictly equals the actual total mass of the yacht. It is important to distinguish displacement from Gross Tonnage (GT); while gross tonnage measures internal enclosed volume, displacement measures physical mass in metric tons (t) or kilograms (kg). Volumetric displacement is expressed in cubic meters (m³), related to mass displacement by water density (approximately 1.025 t/m³ in seawater and 1.000 t/m³ in fresh water).

In naval architecture, a clear distinction is drawn between light displacement (unloaded hull, ballast keel, and machinery) and fully loaded displacement, which includes crew, fuel, fresh water, and provisions. A substantial portion of a monohull's displacement consists of its ballast keel. As illustrated in the dramatic story of the yacht Polbream, losing underwater weight drastically alters draft, freeboard, and righting moment.

According to Wikipedia's reference on large sailing vessels, displacement figures vary depending on load standards and conditions. For a skipper, understanding displacement is crucial when stowing heavy gear, selecting gifts and essential equipment, and calculating draft before navigating shallow waters.