Beam

The widest part of a vessel, measured at its broadest point across the hull.

The term beam is a fundamental concept in nautical terminology, referring to the maximum width of a boat or ship, typically measured at the midpoint of the vessel’s length. The beam is a critical dimension in naval architecture, as it directly influences the vessel’s stability, handling, and overall design. A wider beam generally provides greater stability, as it increases the vessel’s resistance to rolling in rough seas. However, a broader beam can also reduce speed and manoeuvrability, as it creates more drag through the water. Conversely, a narrower beam may allow for faster speeds and more agile handling but can make the vessel less stable, particularly in challenging sea conditions.

The beam also plays a role in determining the interior space of a vessel. A wider beam allows for more room within the hull, which can be advantageous for comfort and storage on leisure boats or for cargo capacity on commercial ships. In sailing vessels, the beam affects the placement and efficiency of the sails, as well as the overall balance of the boat. The term “on the beam” is used to describe an object or direction that is perpendicular to the vessel’s centreline, while “beam sea” refers to waves approaching from the side of the boat, which can cause significant rolling. Understanding the beam is essential for both designing and operating a vessel, as it impacts performance, safety, and usability in various maritime contexts.