The spinnaker, the ally of downwind sailing
The spinnaker, short for spinnaker is a very deep sail, designed to offer maximum surface area to make the most of the apparent wind on downwind points of sail. Its light, cambered design captures a maximum amount of wind for greater speed. It is hoisted onto the spinnaker halyard (often at the masthead on cruising yachts) and trimmed with two sheets and, if necessary, a boom vang. Unlike flat sails such as the genoa, which is rigged along a forestay, the spinnaker has a free edge, is less stable and requires constant trimming.
Some notable differences between symmetrical and asymmetrical spinnakers
- The symmetrical spinnaker is perfectly symmetrical around its central axis. It is rigged between its halyard point at the masthead and its two clew points. The first, to windward, is attached to a steerable spinnaker pole, allowing the spinnaker to be shifted to windward of the mainsail for maximum air and lift. This sail excels in downwind and broad reach conditions, as it is well clear of the mainsail wind. On the other hand, it's not so good when you get closer to the wind's bed. Often very hollow, it is easily unstuck.
- The asymmetric spinnaker has a leading edge shorter than its trailing edge, giving it the shape of an asymmetrical triangle. Its configuration is similar to that of a Code 0, but with a more pronounced hollow. The sail is mounted on a bowsprit to keep it as far away from the mainsail as possible. Its design favors beam and broad reach points, where it generates maximum lift using the apparent wind. Some yachts, such as the Mini 6.50s, have adjustable bowsprits to offset the tack to windward for better downwind sailing.
The symmetrical spinnaker, a technical asset for racing
The symmetrical spinnaker provides optimum control of wind angles and maximum downwind efficiency. By adjusting the height and orientation of the spinnaker pole, the wind center can be dynamically shifted to optimize lift. This makes it particularly popular in regattas, on courses where downwind gears are dominant.
However, setting up a spinnaker requires a certain amount of technical skill, due to the use of the spinnaker pole and the adjustments required for numerous manoeuvres (spinnaker boom, topping lift and downhaul, barber...). Good coordination between crew and helmsman is essential. Tack change maneuvers are also more complex. Gybing involves transferring the spinnaker pole from one side to the other, an operation requiring rigor and mastery. In strong winds, the risk of luffing is increased, requiring constant monitoring of helm and sheet settings.
The asymmetric spinnaker, an easier sail for cruising
The asymmetric spinnaker, on the other hand, is easy to install, as it requires no spinnaker pole. It can be rigged more quickly and allows for smoother sail reduction when needed. It's particularly well suited to modern cruising yachts and monohulls with rigid bowsprits, which make it easier to keep the tack forward.
It's easier to handle, especially for smaller crews, and excels on beam and broad reach. However, it shows its limitations on downwind points of sail, where it becomes difficult to maintain a laminar flow without taking a more open wind angle. Its optimum operating range lies between 90° and 140° of true wind, which may require successive gybes when sailing offshore.
Choosing your spinnaker according to your sailing program
The choice between a symmetrical and an asymmetrical spinnaker depends mainly on the type of sailing and the type of sailboat. For cruising, the asymmetrical spinnaker is often the preferred solution, thanks to its ease of use and versatility. It offers speed gains without requiring a large crew. On the other hand, for regattas, the symmetrical spinnaker remains the reference when the course calls for tight leeward angles, enabling greater control of VMG.
The symmetrical spinnaker is particularly well-suited to traditional sailboats, high-displacement units and racing or regatta yachts, as it is more effective at precise wind angles or on long downwind runs. Fast cruising yachts and multihulls, with a good power-to-weight ratio, will benefit from the asymmetric spinnaker to maximize their performance on the beam.
Practical advice on how to use your spinnaker
Before hoisting the spinnaker, it's essential to check that all halyards, sheets and maneuvers are correctly installed. Optimization of the spinnaker relies on careful adjustment of the sheets and anticipation of the apparent wind. Sheet tension must allow progressive planking without inducing oversailing, while the boom vang or bowsprit must be adjusted to prevent the top of the sail from buckling.
For the symmetrical spinnaker, gybing and spinnaker pole adjustment are key skills. This requires good coordination to ensure smooth transfer of the spinnaker pole without endangering the yacht's stability. The asymmetric spinnaker, on the other hand, requires careful attention to sail angle to best capture variations in the apparent wind and constantly adjust tack tension to maintain optimal shape. In terms of safety, the spinnaker should not be hoisted in strong or gusty winds, and should be able to be lowered quickly if necessary.
