Spinnakers

Spinnakers are sails that are designed specifically for sailing with the wind 90°–180° off the bow. Spinnakers fill with the wind, bulging out in front of the boat when they are deployed.

They are lightweight, usually nylon, fabric. They can be optimised for a particular range of wind angles, and are known as reaching or running spinnakers, by the shaping of the panels and seams. Spinnakers are often called cruising chutes because of the similarity with parachutes.

Spinnakers are used for sailing with the direction of the wind. Spinnakers are a type of airfoil and will generate lift if flown at a reaching angle. Running spinnakers have extreme amounts of camber, making them almost hemispherical. The large camber maximizes the drag. Reaching spinnakers have less camber as they operate partially with an airflow that generates lift.

Well designed spinnakers will have taut leading edges when filled, will have a smooth curve when filled, with no bubbles or depressions caused by inconsistent stretching of the sail fabric.

Not so long ago, lightweight downwind sails were regarded by many cruising sailors as the exclusive preserve of the racing fraternity, who employed vast crews to tussle with acres of unruly spinnaker nylon. But the reality is now very different. In the same way that upwind sailing has been made less strenuous by the increasing popularity of self-tacking jibs, fully-battened mainsails and cockpit-controlled reefing systems, developments with spinnakers and cruising chutes have resulted in more stable, easily-managed sails which can be comfortably handled by smaller crews.

For optimum efficiency, you need a spinnaker whose tack is projected from the end of a pole to bring it out from behind the mainsail on a broad reach or run. The drawback is that, since the sail is larger than a cruising chute and only firmly attached at one corner (the head), it needs more care inh oisting, trimming and dowsing.

A cruising chute, on the other hand, is smaller and easier to manage, but less efficient as the wind comes further astern. The solution is to have one of each... perhaps a spinnaker for racing, and light-weather running/broad reaching in cruising mode, plus a cruising chute. Not only can the chute be tacked to the stemhead when cruising, but, flown from the pole as an asymmetric spinnaker, it will double as a highly effective reaching kite in breezy conditions.

By following a few simple rules and not trying anything too ambitious, you'll be OK with spinnakers. When hoisting a spinnaker, you have a choice of launching it from the bow or the leeward side. As a rule, the second option is safer because you hoist in the lee of the genoa.

Aerodynamic instability when running needs skillful handling and is a balancing act, often requiring reduced sail.

Symmetric and asymmetric  spinnakers 

There are two main types of spinnakers, symmetric and asymmetric. Asymmetric spinnakers operate more like a jib, generating lift from the side, rather than the top like a symmetric spinnaker. This makes asymmetrics a better choice on reaching courses than symmetric spinnakers, which excel when running. While a top racing boat might have a number of spinnakers, both symmetric and asymmetric, to cover all courses and wind conditions, cruising boats almost always use asymmetric spinnakers.

The use of spinnakers has caught on steadily. The tack of the sail may be attached at the bow like a genoa but is frequently mounted on a bowsprit, often a retracting one. If the spinnaker is mounted to a special bowsprit, it is often possible to fly the spinnaker and the jib at the same time. Usually the jib is furled when the spinnaker is in use.

Since they will only be used under certain conditions, raising and lowering spinnakers is a task that is often performed while under sail. Due to the size of spinnakers, this can be a difficult operation, since they will immediately catch the wind.

Dousing socks, spinnaker sleeves, snuffers, or in abbreviated form, socks, are used to make deploying and retrieving the spinnaker a much easier task. Socks are long fabric tubes with a ring in one end to hold them open. Since spinnakers are stored in their sock, the first step is to set up the sock.

Spinnaker chutes are a tube or aperture in the deck close to the forestay, for the launching and recovery of the spinnaker. They are most commonly found on modern dinghy designs, and updated older classes. To allow recovery of the spinnaker into the chute, one or more recovery patches are fitted to the spinnaker, to which the tail of the spinnaker halyard is attached or passed through. The spinnaker and its halyard thus form a continuous loop, passing through the chute.

If the spinnaker chute penetrates the hull and is required to be watertight, it takes the form of a hard tube sealed to the hull at both ends.

Spinnaker or cruising chute? Radial head spinnakers, Tri-radial spinnakers, Full tri-radial spinnakers, Cruising chutes (cross-cut), Cruising chutes (radial head), Asymmetric spinnakers.