Keelsprays

Keelsprays refers to the spray produced by the keel of a moving vessel. The term is sometimes used in lay discussions to describe the stream of spray that forms along the hull’s underside when a boat travels at speed or rides over waves. The character and intensity of keelsprays depend on hull shape, speed, trim, sea state, and the angle of attack.

In naval architecture, spray from the keel is analyzed as part of seakeeping and hydrodynamics. Designers seek to minimize keelsprays to reduce deck spray, improve visibility, and decrease drag. Techniques include hull form refinement, spray rails, chines, and appendage shaping; high-speed planing hulls may exhibit different spray patterns compared to displacement hulls. The use of bilge keels or other vertical elements can alter spray direction and magnitude.

The term has no formal, standardized definition beyond describing a physical phenomenon associated with the hull–water interface. Consequently, keelsprays may appear in hobbyist or journalistic writing, and in some cases may be used as a brand name or fictional term, but such uses are context-dependent and not part of the technical vocabulary.

See also: spray, hull design, seakeeping, hydrodynamics, spray rails.