← The Encyclopedia of Sails
Part 10 — Reference
Glossary of sailing terms
Every term used in the encyclopedia, defined in plain language. Terms with a full entry link through to their own page.
No term matches that. Try “luff”, “clew” or “telltale” — or read the encyclopedia’s 28 chapters.
- Afterguy — full entry
- The spinnaker sheet that goes through the jaw of the spinnaker pole. Used on big boats where separate sheet and afterguy attach to both spinnaker clews. Heavier than regular sheets due to increased pressure.
- Aft — full entry
- Toward the rear of the boat
- Almanac
- Navigation reference
- Anchor — full entry
- Device used to secure a boat to the seabed
- Apparent wind — full entry
- The wind experienced by a moving boat
- Aspect ratio — full entry
- The height of a foil (sail, keel, or rudder) divided by its width. High aspect sails have long luffs and short feet.
- Backstay — full entry
- Wire supporting the mast from the stern
- Barometer — full entry
- Air pressure gauge
- Batten — full entry
- Flexible strip inserted into sail to maintain shape
- Beam — full entry
- Width of a boat at its widest point
- Bearing — full entry
- Direction to object
- Beaufort scale — full entry
- Wind force scale
- Becket — full entry
- Loop of rope or eye splice
- Berth — full entry
- Sleeping area or docking space
- Bias Elongation — full entry
- See Warp
- Bight — full entry
- Curve or bend in a rope
- Bilge — full entry
- Lowest inner part of a boat’s hull
- Bi-Radial — full entry
- A sail construction technique where radial panels emanate from the head and clew
- Block — full entry
- Pulley used in sailing
- Boom — full entry
- Spar at bottom of mainsail
- Boomvang — full entry
- A block-and-tackle or hydraulic ram controlling boom angle. Lowering the boom tightens the mainsail leech
- Bow — full entry
- Front of the boat
- Bowline — full entry
- Essential knot used in sailing
- Bowsprit — full entry
- Spar extending from bow
- Broach — full entry
- Accidental turning into the wind
- Camber — full entry
- Curve of a sail
- Capsize — full entry
- To overturn
- Catamaran — full entry
- Double-hulled vessel
- Centerboard — full entry
- Retractable keel
- Chainplate — full entry
- Metal plates securing rigging to hull
- Chafe — full entry
- Wear from friction
- Chart — full entry
- Marine map
- Cleat — full entry
- Fitting for securing lines
- Clew — full entry
- Lower aft corner of a sail. Outhaul attaches here on mainsails; sheets attach here on genoas
- Close-hauled — full entry
- Sailing almost directly into the wind
- Companionway — full entry
- Entrance to cabin
- Compass — full entry
- Navigation instrument
- Course — full entry
- Intended direction
- Cross cut — full entry
- A sail construction technique where panels are parallel to each other and perpendicular to the sail’s leech
- Cruising — full entry
- Recreational sailing
- Cunningham — full entry
- Named after Briggs Cunningham, a control that adjusts draft position by changing sail luff tension
- Dead reckoning — full entry
- Position estimate
- Deck — full entry
- Upper surface of boat
- Depression — full entry
- Low pressure area
- Deviation — full entry
- Compass error
- Downwind Sails
- Draft — full entry
- The deepest part of the curve in a sail.
- The distance from the water line to the bottom of a boat’s keel
- Drift — full entry
- Movement caused by wind/current
- Drogue — full entry
- Sea anchor
- E — full entry
- The distance from the aft face of the mast to the outermost point on the boom where the mainsail is pulled
- Ease — full entry
- To loosen a line
- Eye splice — full entry
- Permanent loop in rope end
- Eyelet — full entry
- Reinforced hole in sail
- Fairlead — full entry
- Fitting guiding a line
- Fall off — full entry
- Turn away from wind
- Fathom — full entry
- Unit of depth (6 feet)
- Fender — full entry
- Cushion protecting hull
- Fetch — full entry
- Wind-water distance
- Fictitious luff — full entry
- Imaginary line for sail design
- Fill Threads — full entry
- See Warp
- Fix — full entry
- Position determination
- Flattening Reef — full entry
- A sail control that flattens the mainsail’s bottom part using a grommet on the leech about a foot above the boom. Also called “flattener”
- Foot — full entry
- Bottom edge of a sail
- Foreguy — full entry
- Line pulling the outboard end of the spinnaker pole down
- Forestay — full entry
- Wire supporting mast from bow
- Foretriangle — full entry
- Triangle formed by the forestay, forward edge of mast and foredeck
- Foredeck — full entry
- Forward part of deck
- Front — full entry
- Weather system boundary
- Furling — full entry
- Rolling up a sail
- Gaff — full entry
- Spar supporting sail top
- Gale — full entry
- Strong wind
- Genoa — full entry
- Large headsail
- Gooseneck — full entry
- Boom attachment to mast
- Gore — full entry
- Vertical panel in sail
- Gradient — full entry
- Pressure difference
- Grommets — full entry
- Metal rings in sail
- Gunwale — full entry
- Upper edge of boat’s side
- Gybe — full entry
- Change course with wind aft
- Halyard
- Line for raising sails
- Hand
- To furl or take in sail
- Head
- Top corner of a sail
- Heading
- Direction boat points or current direction
- Headstay
- Forestay
- Headstay Sag
- Deflection of the headstay to leeward and aft caused by wind force on the sail
- Head up
- Turn toward wind
- Headsail
- Any sail forward of mast
- Heel
- Boat’s lateral incline
- Helm
- Steering control
- Hull
- Main body of boat
- I
- Measurement of foretriangle height, with specific measuring points varying by rating rule
- Irons
- In stays, head to wind
- Isobar
- Equal pressure line
- J
- Measurement of foretriangle base – distance between mast and forestay
- Jib
- Forward triangular sail
- Jib Lead
- Block or fairlead for jib sheet between clew and winch, affecting jib shape
- Jibing
- Same as gybing
- Jury rig
- Temporary repair
- Keel
- Fixed underwater fin
- Kevlar
- Sail fabric material
- Knot
- Speed measurement (1 nautical mile/hour)
- Knots
- Wind speed measure
- Laminate
- Multi-layer sail material
- Laminated Sail Cloth
- Multi-layer fabric with fiber and film bonded by adhesive, using film for bias stretch control and fiber for oriented direction stretch resistance
- Lanyard
- Short line for securing items
- Latitude
- North-south position
- Lazy Guy/Lazy Sheet
- Lines used on large boats for jibing spinnaker, attached to inactive clew
- Lazyjacks
- Lines supporting lowered sail
- Leach
- Aft edge of sail
- Lee
- Side sheltered from wind
- Lee Helm
- Boat’s tendency to bear off when helm is released, common in light air or with forward-positioned mast
- Leeward
- Away from wind
- Life jacket
- PFD (personal flotation device)
- Lifeline
- Safety wire around deck
- Lines
- Ropes used on boats
- Log
- Speed/distance record
- Longitude
- East-west position
- LP
- Luff Perpendicular – shortest distance from genoa clew to luff, used to express genoa size as percentage
- Luff
- 1. Forward edge of a sail. 2. Sail flapping from heading too close to wind or insufficient trim. 3. Altering course toward wind
- Luffing
- Fluttering of sail
- Mainsail
- Principal sail
- Mainsheet
- Line controlling mainsail
- Mast
- Vertical spar supporting sails
- Mooring
- Permanent anchoring spot
- Mylar
- Sail material
- Nautical mile
- 6,076 feet
- Navigation
- Determining position/course
- Noon sight
- Sun observation at midday
- Outhaul
- Control line pulling mainsail clew to boom end
- Overboard
- Off the boat
- Overlap
- Sail extending past mast
- Overpowered/Underpowered
- Describes when a boat has too much sail (heeling too much) or too little sail (causing slowdown)
- P
- Measurement from boom top at gooseneck to highest point of mainsail on mast
- Painter
- Bow line
- Peak
- Upper corner of sail
- Pennant
- Small flag
- Piloting
- Coastal navigation
- Pinch
- Sail too close to wind
- Plot
- Mark position
- Port
- Left side of boat
- Port tack
- Wind from port side
- Quarter
- Aft section of side
- Rake
- Mast’s inclination from vertical, measured from mast back at partners to main halyard plumb line
- Range
- Navigation markers
- Reach
- Sailing across wind
- Reacher
- High-clewed genoa for heavy wind reaching, also called “blast reacher”
- Reef
- Reduce sail area
- Rigging
- Boat’s line/wire system
- Roach
- Curved sail section beyond straight line from head to clew
- Rudder
- Steering blade
- Running
- Sailing away from wind
- Sail plan
- Arrangement of sails
- Sailcloth
- Sail material
- Schooner
- Two-masted vessel
- Scrim
- Reinforcement layer
- Scrim Cloth
- Extremely loose-woven cloth laminated to Mylar for strong, lightweight sailcloth, distinctive for spaces between threads
- Seam
- Join between sail panels
- Seam allowance
- Extra material at join
- Sea state
- Wave condition
- Shape
- Three-dimensional form
- Sheet
- Line controlling sail
- Shelf Foot
- Mainsail option providing extra lower third shaping control via flat cloth connecting sail bottom to boom
- Shrouds
- Side support wires
- Skeg
- Rudder support
- Slack
- Loose, not tight
- Sleeve
- Mast attachment method
- Sloop
- Single-masted vessel
- Spinnaker
- Large downwind sail
- Spreaders
- Horizontal mast supports
- Squaring the Pole
- Tightening afterguy to pull spinnaker pole back
- Stanchion
- Lifeline support
- Starboard
- Right side of boat
- Stay
- Support wire for mast
- Stern
- Rear of boat
- Stretch
- Fabric elongation
- Swage
- Metal fitting on wire
- Tack
- 1. Lower forward corner of sail. 2. Turning boat through wind. 3. Port/starboard designation based on boom position
- Tackle
- Block and line system
- Tape
- Reinforcement strip
- Tape-Drive®
- UK Sailmakers’ patented system using high-strength Kevlar tapes along computer-mapped load lines to maintain sail shape
- Tabling
- Edge reinforcement
- Telltales
- Wind indicators
- Tentering
- Fabric stabilization
- Thimble
- Protective metal eye
- Thread
- Sewing material
- Tiller
- Steering lever
- Topping lift
- Supports boom
- Track
- 1. Rail for sail hardware 2. Course made good
- Transit
- Alignment marks
- Transom
- Stern cross-section
- Trim
- Adjust sails
- Triradial
- Panel arrangement
- True wind
- Actual wind direction
- Under way
- Boat in motion
- UV cover
- Sail protection strip
- Vang
- Control for boom
- Variation
- Magnetic deviation
- Wake
- Trail behind boat
- Warp
- Length-wise threads in cloth
- Warp, Fill and Bias
- Terms describing thread directions in woven cloth. Warp threads parallel longest edge, fill threads perpendicular. Bias refers to off-thread stresses
- Warp-Oriented Cloth
- Sailcloth with greater warp direction strength, sometimes using only warp yarns glued to Mylar film
- Waterline
- Where hull meets water
- Weave
- Fabric construction
- Weather helm
- Tendency to turn windward; measured in rudder angle degrees needed for straight course
- Windage
- Wind resistance
- Windlass
- Anchor handling machine
- Windward
- Toward the wind
- Winch
- Line handling drum
Still not sure what you need?
Your local loft talks about sails all day. Tell them about your boat and how you sail it, and they will translate the jargon into an inventory.