Monohulls

A monohull is a boat or ship with a single hull, as opposed to multihull designs such as catamarans and trimarans. The term is used across sailing and powerboat contexts to describe the primary hull configuration.

Construction and hull forms vary widely. Monohulls can be built from timber, fiberglass (fibreglass), aluminum, steel, or composite materials. Hull shapes include displacement designs, which move steadily through the water, and planing designs, which can rise partially out of the water at higher speeds. Keels are a key feature and come in several forms, such as fixed long or full keels, fin keels with ballast, and sometimes weighted bulb keels. Some racing or specialized monohulls use centerboards or daggerboards to improve upwind performance while preserving shallow-water capability.

Handling and performance are influenced by hull and keel geometry. Monohulls typically heel (lean) to windward when sailing, changing the underwater profile and sail efficiency. Ballast in the keel provides righting moment to resist capsizing. A deeper fixed keel generally offers better tracking and upwind performance but reduces shallow-water access, whereas lighter and shallower versions may be more maneuverable in certain harbors.

Rig, interior layout, and purpose vary with size. Monohulls can carry a range of rigs, including sloops, cutters, and sometimes ketches. Interior space in monohulls is usually elongated along the hull length, and overall living area can be more limited compared with multihulls of similar length.

Historically, monohulls have dominated many sailing traditions and remain common for cruising, racing, and commercial use due to their balance of cost, maintenance, and seaworthiness.