Keel

A principal longitudinal structure along the lower part of a vessel’s hull.

In traditional construction, the keel forms the backbone from which frames and other hull members are built. On many sailing yachts, the term also refers to a fixed external fin or deeper hull structure that provides lateral resistance and may contain ballast to improve stability.

Keels take many forms, including full, fin, bilge and lifting arrangements, and not every keel is ballasted or shaped like a projecting fin. Its design affects strength, draught, directional stability, leeway, grounding behaviour and sailing performance.