Dimensions
Air draft
Air draft is the vertical distance from the waterline to the highest point of the boat, often the masthead or an antenna.
More info →THE SAILING KNOWLEDGE LIBRARY
Sailboat terms, in plain English.
Understand the language in a boat listing. Each definition includes a practical example and a question to ask when researching your next sailboat.
30 terms
Sailing skills
Apparent wind
Apparent wind is the wind experienced on a moving boat: the combination of the surrounding wind and the effect of the boat’s motion.
More info →Equipment
Autopilot
An autopilot is a system that steers a boat toward a commanded heading or another supported steering target. It uses a controller, sensors and a drive arrangement.
More info →Hull & keel
Ballast
Ballast is weight positioned to help a boat’s stability and trim. On many monohulls, a substantial portion is carried in or attached to the keel.
More info →Dimensions
Beam
Beam is a boat’s width, generally measured at its widest point.
More info →Boat types
Catamaran
A catamaran is a vessel with two main hulls connected by a structure or deck. Sailing catamarans include both light performance designs and spacious cruising boats.
More info →Hull & keel
Centerboard
A centerboard is a retractable underwater foil used to reduce sideways movement under sail. It generally pivots into a case; a daggerboard slides instead.
More info →Rig & sails
Cutter
A cutter is commonly a single-masted rig arranged to carry two headsails, with an inner staysail and an outer headsail.
More info →Dimensions
Displacement
Displacement is the weight of water a floating boat displaces; for a boat afloat in equilibrium, that equals the boat’s total weight.
More info →Dimensions
Draft
Draft is the vertical distance from the waterline to the deepest part of the boat below the surface, usually the keel or rudder.
More info →Hull & keel
Fin keel
A fin keel is a relatively compact keel projecting below the hull rather than extending along much of its length.
More info →Hull & keel
Full keel
A full keel extends along a substantial portion of a boat’s underwater length, with exact shape varying by design.
More info →Rig & sails
Genoa
A genoa is an overlapping headsail whose clew extends aft of the mast when set in its normal working position.
More info →Sailing skills
Gybing (jibing)
Gybing is changing direction so the stern passes through the wind and the mainsail changes sides. “Jibing” is another common spelling.
More info →Rig & sails
Halyard
A halyard is a line used to hoist a sail or another item up a mast or stay.
More info →Rig & sails
Jib
A jib is a headsail set forward of the mast. In common usage, it usually does not overlap the mast as a genoa does.
More info →Hull & keel
Keel
A keel is the lower central structure or appendage beneath a sailboat. Depending on the design, it contributes lateral resistance and may carry ballast.
More info →Rig & sails
Ketch
A ketch is a two-masted rig with a mainmast and a shorter mizzenmast positioned forward of the rudder stock.
More info →Navigation
Knot
A knot is a unit of speed equal to one nautical mile per hour. It can also mean a tied fastening in a line, so context matters.
More info →Dimensions
Length overall (LOA)
Length overall describes a boat’s overall length, but published measurements do not always include the same fittings.
More info →Rig & sails
Mainsail
The mainsail is the principal sail associated with the mainmast. On many common cruising rigs, it is set behind the mast and attached along a boom.
More info →Boat types
Monohull
A monohull is a boat with one main hull. In sailing, the term distinguishes it from catamarans and trimarans.
More info →Navigation
Port and starboard
Port is the left side of a vessel when facing forward toward its bow; starboard is the right side. These labels stay with the boat regardless of where a person faces.
More info →Sailing skills
Reefing
Reefing means reducing a sail’s working area while retaining a usable sail shape for the conditions.
More info →Rig & sails
Running rigging
Running rigging consists of lines and associated controls used to hoist, lower and adjust sails or movable spars.
More info →Rig & sails
Sheet
A sheet is a line used to control a sail’s position or trim. It is not the sail itself.
More info →Rig & sails
Sloop
A sloop is a single-masted sailing rig normally using a mainsail and one headsail at a time as its basic sail plan.
More info →Rig & sails
Standing rigging
Standing rigging supports the mast. On a conventionally stayed rig, it includes components such as shrouds, forestays and backstays.
More info →Sailing skills
Tacking
Tacking is changing direction so the bow passes through the wind and the wind changes from one side of the boat to the other.
More info →Dimensions
Waterline length (LWL)
Waterline length is the length of the hull where it intersects the water in a stated loading condition.
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