You're out on the water when you spot a fleet of sailboats. You watch as crisp white triangles converge on a windward mark. As the boats round, large, brightly-colored sails blossom like flowers. The scene transforms from one of white against blue to a rainbow of moving balloons. They're spinnakers – fragile, delicate, tricky to handle, yet able to pull like a locomotive.

Spinnakers are yacht racing's most dramatic contribution to sailing technology. After 150 years of development, the sails have evolved into genres and sub-genres, with different cuts and techniques for deployment. No longer just for racers, today spinnakers have become part of the tool kit of casual and cruising sailors.

While the standard suite of sails is highly developed, for speed off the wind, a spinnaker is the way to go. Using one requires some extra rigging and new skills, but it is worth the effort when you see the wake boiling away behind you.

UK-HALSEY.COMThe sail was dubbed a "spinnaker" after the "Sphinx's acre," or so the story goes.'SPHINX ACRE'

Fore-and-aft sails, the staple of every sailor, are efficient when reaching and beating, but less so when running. Going downwind, sail area is the name of the game. In 1860, a racing yacht known as Sphinx gained an advantage by setting a large, very full cut sail forward, thus dramatically increasing her sail area and speed on a downwind leg. Other racers soon copied the idea and called the new sail a "spinnaker" after the "Sphinx's acre," or so the story goes.

True or not, a spinnaker can dramatically increase your speed downwind. But a traditional spinnaker requires a lot of rigging: halyard, pole, lift, downhaul, sheet and guy. It requires special techniques to set, trim, jibe and recover. Since it is set flying ahead of the jib stay, it can be quite a handful to manage and subject to spectacular mistakes. The sail can twist. It can wrap the head stay. And a spinnaker broach can lay your mast in the water in seconds.

So why is the sail so popular? Among racers it is a sine qua non because of the dramatic increase in speed. And what is popular with racers eventually gets picked up by more casual sailors. Meanwhile, developments have resulted in more forgiving versions of the sail. Now, spinnakers can be divided into two types – symmetrical and asymmetrical.

SYMETRY

Let's start with the traditional, symmetrical spinnaker. This is a large, roughly triangular sail built with a lot of draft, or curvature. It looks like a big bubble of cloth, especially at the top, causing it to resemble parachutes. That's why they call it "the chute." Some sailors also call them "kites" because they fly ahead of the boat (though now people are powering boats with actual kites, so maybe the term is no longer useful).

UK-HALSEY.COMThis straight-cut spinnaker provides a lot of lift.Spinnakers are made from nylon because it is very light, and a little stretch won't result in damage. They are typically three-quarters of an ounce to three ounces in weight per yard, usually of rip-stop nylon. Rip-stop cloth has a network of heavier threads embedded to give the very light cloth strength. Unlike Dacron, nylon can take dyes, so spinnakers are usually very colorful, and some have beautiful designs. A typical cut is the "tri-radial," with the cloths laid out in radiating lines from the three corners (since that is the direction of the strain).

In use, the spinnaker is flown free, ahead of all the rigging. It is connected to the boat by the halyard at the top, and lines at the lower corners, or clews, called the sheet and the guy. A pole holds the windward clew out opposite the mainsail (to starboard when on starboard tack). A line leads aft from that clew and is called the guy. The other clew flies free and is controlled by a line leading aft called the sheet. If it becomes necessary to jibe the spinnaker, the pole is shifted from one clew to the other and the sheet then becomes the guy and vice versa. The pole is usually attached to a track on the mast and is supported by a topping lift and a downhaul or foreguy.

There are many ways of setting a spinnaker. The object is to get a big wad of loose cloth up and drawing smoothly before it can tangle on something or twist into an unusable shape, like an hour-glass. One technique is to send the chute up in stops; that is, bundled into a long sausage held by rubber bands or light string. When it is all the way up a sharp pull on the sheet and guy breaks the stops and the sail fills.

Some dinghy classes use a launcher – a tube under the deck with an opening at the bow. The sail is stored in the tube with the three corners sticking out the opening and with the halyard, sheet, and guy attached. After rounding the windward mark, the crew hauls the chute out by the halyard and snaps on the pole. To take the sail in, there is a line from the center of the forward side of the sail down through the launcher. The pole is released and the halyard eased as the sail is pulled back into the launcher.

UK-HALSEY SAILMAKERSA spinnaker provides lots of extra sail area downwind.Many sailors simply pack the spinnaker into a bag, called a turtle, on deck with the corners out and set it similarly to the launcher (though it is retrieved differently). A more recent method involves the use of a sock. That is a long, cloth tube with the spinnaker in it, the head sticking out of the top and the clews out the bottom. There is an uphaul and a downhaul on the bottom of the sock. The sock is hoisted on the halyard. To set the spinnaker, you haul the bottom of the sock up and pull the sheet and guy. To snuff the sail, you ease the sheet and guy and pull the bottom of the sock down. Then lower the whole thing.

TENDING THE SAIL

Once the sail is up and pulling it needs to be tended carefully. The pole should be horizontal and at right angles to the apparent wind. Both clews should be the same height. The sheet is eased to just before the point where the weather leech starts to curl. If the sheet is too tight, the sail will not be pulling at full efficiency; if it is eased too far the weather leech will curl and the sail will collapse. The helmsman should steer a straight and steady course so that the sail doesn't need to be constantly adjusted. Assuming steady winds, an autopilot can help in this regard.

If the sail needs to be jibed, first trim the main to the centerline. Then remove the pole and guide the sail to the other side of the boat with the sheet and guy as the boat turns. Finally, set the pole on the other side and complete the jibe of the main. There are different techniques for moving the pole across, depending on the size of the boat and the crew available.

The basic way to take in a spinnaker is for the boat to jibe onto a broad reach so that the chute can be blanketed by the main as it is taken in. The guy is released and the sail flies forward. It is hauled aboard by the sheet as the halyard is eased. It requires fast work and coordination to keep from dropping the sail into the water. Using a sock is more controlled. Ease the sheet and guy as the sock is pulled down by its downhaul, then lower the bundle to the deck.

UK-HALSEY SAILMAKERSSome spinnakers can be carried on a reach.ASYMETRY

Traditionally, the symmetrical spinnaker was used only by more experienced sailors, with many preferring instead to use a large genoa to increase sail area downwind. Eventually someone thought to merge the genoa and spinnaker into a sail that combined the desired characteristics of each.

Every sailmaker has a different name for this sail, but the generic name is the asymmetrical spinnaker, or sometimes just the A-sail. Like the spinnaker, it is cut full for downwind use, though there are models designed primarily for reaching. Like a genoa, it is set on its own luff rope. Like a spinnaker, it is set flying ahead of the head stay. Like a genoa, it is flown without a pole, and controlled by two sheets.

Because the sail is easier to set and control, with fewer crew needed, it is popular with cruisers and day-sailers, as well as racers. Some of the racing boats, especially fast dinghies, set the tack to a short, retractable bowsprit.

Some people set and recover the asymmetrical flying, like a standard spinnaker. In that case, the sail may be packed into a turtle. Attach the lines to the three corners of the sail: halyard to the head, tack line to the tack, and sheets to the clew. Then send the sail aloft, with or without stops, and trim the sheet. To take in the sail, release the sheets so that the sail flies ahead of the boat. Pull the sail into the boat by the tack while easing the halyard. Asymmetricals can also be set and recovered with a sock.

UK-HALSEY SAILMAKERSA tri-radial cut spinnaker.EVOLVING MODELS

The asymmetrical spinnaker has been around for awhile, and different variations have evolved. They are referred to by the word "Code" and a number. Code 0 is the most genoa-like of the A-sails. It is heavier, more flat-cut, and usually has a wire luff rope. It is used in a tight reach situation, and is the only version suitable for roller furling. Codes 1, 3, and 5 are reaching sails. As the numbers increase, the sails are made of progressively flatter and with heavier cloth for progressively higher wind speeds. Codes 2, 4, and 6 are similarly arranged but are running sails with a fuller cut. Code 2 is for medium air, and Code 6 is for running in storm conditions.

Once the sail is up and flying, it is handled much like a genoa. Tighten the tack when reaching, and ease it up a bit when running to put some belly into the sail. While it is possible to run dead downwind, it is safer and faster to run on a broad reach and tack downwind. "Tacking" in this case is actually jibing. Unlike a symmetrical spinnaker, there is no pole to deal with. You simply ease out the working sheet; then, as the stern passes through the wind, haul in on the new working sheet. You may want to simplify the operation and jibe the main first, then the A-sail.

The advantages of an asymmetrical over a traditional spinnaker is that it requires less rigging, is simpler to set and recover, and has a much lower learning curve. If you already are familiar with a genoa, you basically have the A-sail down.