A sloop is a sailing vessel with a single mast carrying a fore-and-aft rig with one headsail set ahead of the mast and a mainsail behind it. It is by a wide margin the most common rig on modern yachts and dinghies. Beginners need only remember: one mast, one mainsail, one jib or genoa. Experienced sailors know the family divides into masthead and fractional sloops, Bermudan and gaff sloops, and that the distinction from a cutter, which also has one mast, lies in the number of headsails and where the mast stands. The word comes from the Dutch sloep, and the rig has been refined over three centuries into the most efficient general-purpose sailing machine there is.
Anatomy of a Sloop Rig
The mast is held up by a forestay to the bow, a backstay to the stern and shrouds to the sides. The mainsail is set on the after side of the mast with its foot along the boom; the headsail is set on the forestay, on hanks, a luff tape in a foil or a roller furler. Rating rules describe the rig with a handful of measurements: I, the height of the forestay above deck; J, the base of the foretriangle from the mast to the forestay; P, the luff length of the mainsail; and E, its foot length. LP, the perpendicular from the luff to the clew of a headsail, is expressed as a percentage of J to give the familiar 105, 135 or 150 per cent genoa.
Masthead and Fractional Sloops
On a masthead sloop the forestay attaches at the top of the mast. The foretriangle is large, the genoa is the main engine upwind, and the mast is stiff and controlled mainly by backstay tension, which tightens the forestay rather than bending the spar. The type remains popular for cruising because the big headsail is powerful and the rig is simple to tune.
On a fractional sloop the forestay attaches some way below the masthead, at seven-eighths or so on many modern designs. The mainsail becomes the larger sail, the headsail is smaller and easier to handle, and the mast is designed to bend: backstay tension bows the spar above the hounds and flattens the mainsail, while swept-back spreaders let the cap shrouds tension the forestay. Racing boats and nearly all modern performance cruisers are fractional sloops because the rig gives so much control over the shape of the mainsail through the wind range. From a sailmaker’s point of view, a fractional sloop’s mainsail is cut with a luff curve matched to the mast bend, and the trimmer can use that bend as a gear lever.
Sloop, Cutter, Cat Rig and Two-Masted Rigs
- Cutter: one mast set further aft, with two headsails, a yankee or jib on the forestay and a staysail on an inner stay. More versatile in heavy weather, more strings to pull.
- Cat rig: one mast right forward with a single mainsail and no headsail. Simplest of all.
- Ketch and yawl: two masts, with the smaller mizzen aft. Splits the sail area into smaller pieces for short-handed handling at a cost in upwind efficiency.
Why the Sloop Dominates
Two sails, each working on the other, make a remarkably efficient upwind machine. The headsail bends the wind onto the mainsail and the mainsail keeps the flow attached over the back of the headsail; the slot between them is where much of the drive is generated. One mast means one set of standing rigging, one halyard for each sail, one pair of sheets to tack, and a boat that can be sailed by one person. Nothing else combines that simplicity with that performance.
Sail Inventory for a Sloop
A cruising sloop typically carries a mainsail with two or three reefs, a roller-furling genoa of 120 to 140 per cent, and perhaps a code zero for light air. A racing sloop carries a mainsail cut for the mast bend range, headsails of several sizes to cover the wind range and spinnakers for downwind. UK Sailmakers designs each sail in the inventory to work with the others, because on a sloop the mainsail and headsail share the load: change the genoa size and the mainsail trim that balances the helm changes with it.
Frequently Asked Questions about Sloops
What is the difference between a sloop and a cutter?
Both have one mast. A sloop carries a single headsail; a cutter carries two, on a forestay and an inner stay, and usually has its mast stepped further aft to make room for them.
Is a masthead or fractional sloop better?
Neither is better in the abstract. Masthead rigs are simple, powerful in light air and easy to tune. Fractional rigs give smaller, easier headsails and much more control over mainsail shape through mast bend, which racers and performance cruisers value.
The sloop is where most of us learn to sail and where most of us stay, and for good reason: two sails and one mast give a boat that is efficient, handy and endlessly tunable. Understand how your mainsail and headsail work together and how the rig that holds them is tuned, and you have understood the essence of sailing a sloop well. See also cutter, fractional rig, masthead rig, genoa and I, J, P and E.