A sheet is the line used to control a sail’s angle to the wind and, with it, the sail’s shape. Each sheet is named for the sail it trims: mainsheet, jib sheet, genoa sheet, spinnaker sheet, staysail sheet. Pull a sheet in and the sail moves toward the centreline and its leech tightens; ease it and the sail swings out and opens. The beginner should know that sheets are the lines you work most while sailing, and that easing one is nearly always the safe move. The experienced trimmer adds that on a headsail the sheet is the main depth and twist control, that its lead position matters as much as its tension, and that the word comes from the Old English for the corner of a sail, not from anything to do with bedding.
Types of Sheet
- Mainsheet: usually a single line led through a multi-part purchase to the boom, often with a traveller beneath it so angle and twist can be set separately.
- Jib and genoa sheets: a pair, one each side, attached to the clew. The loaded one is the working sheet; the other is the lazy sheet, ready for the next tack.
- Spinnaker sheets: a pair led to the quarters. On a symmetrical spinnaker the windward one becomes the guy, the leeward one the sheet; on an asymmetric both are sheets, one working, one lazy.
How a Sheet Shapes a Sail
Upwind, the mainsheet is a leech-tension control before it is an angle control. Sheet on and the leech straightens, twist reduces and the top of the sail starts to work; ease an inch and the leech opens, the top telltale flies and the boat stands up. The traveller then places the boom relative to the centreline. Off the wind the mainsheet becomes purely an angle control and the vang takes over the leech.
A headsail has no boom, so its sheet does both jobs at once, and the sheet lead, the point where the sheet turns down to the deck, splits them. Moving the lead forward pulls more down on the leech, closing the twist and rounding the foot; moving it aft lets the leech twist open and flattens the foot. The sheeting angle, the angle between the centreline and the line from tack to lead, is set by inboard and outboard tracks or a barber hauler; tighter angles point higher, wider angles give power and speed. When UK Sailmakers designs a genoa, the clew height and the expected lead position are part of the drawing, so the designed shape only appears when the sheet is led where the sail was drawn for.
Sizing, Material and Length
Cruising boats generally use polyester double braid, which is soft in the hand, grips a winch well and stretches little enough for the job. Racing boats use a low-stretch core such as Dyneema® with a polyester or blended cover, often stripped of cover in the section that never touches a winch to save weight. As a rough guide, a genoa sheet needs to be about one and a half times the boat’s length overall, and a mainsheet depends on the purchase and boom length.
Technique and Common Mistakes
- Ease in a puff: when the boat heels hard, easing the sheet is faster and safer than fighting the helm. When in doubt, let it out.
- Trim to the telltales: on a headsail, the luff telltales should stream together on both sides; on a mainsail the top leech telltale should fly most of the time.
- Never wrap a sheet around your hand: and keep fingers clear of the winch drum. A loaded sheet that gets away will take skin with it.
- Tacking: release the working sheet as the jib backs, take in the lazy sheet hand over hand before the load comes on, then finish on the winch.
A cruising crew want sheets that are comfortable and easy to handle short-handed; a racing crew treat them as instruments, marking reference points and easing and trimming constantly to keep the sail at its designed shape. Both should replace a sheet that has gone hard and shiny; it will not grip a winch.
Frequently Asked Questions about Sheets
Why is it called a sheet?
The word descends from the Old English sceata, meaning the lower corner of a sail, which became the name for the rope attached to that corner. The saying three sheets to the wind describes a ship whose sheets have all been let fly, so she staggers like a drunk.
How long should jib sheets be?
About one and a half times the length of the boat is a good starting point for each sheet, enough to reach from the clew round the winch to a cleat with a generous tail, on the widest sheeting angle you will use.
The sheet is the sailor’s direct connection to the sail. Halyards, backstays and outhauls set the stage, but it is the sheet in your hand that decides whether the sail is driving or stalling, and a trimmer who plays it constantly, easing before the puff and squeezing on as it passes, is doing the most important job on the boat. See also clew, lead, traveller and telltale.