DECODING THE TERMS
A variety of terms is used for downwind sails, though it has to be said that most are used aboard raceboats. In addition to the Code 0 you may have heard of an A1, A2, A3, A4 and even an A5 or A6. The A simply signifies it’s an asymmetric sail, while odd numbers are used for reaching-oriented sails, and even numbers are for sails designed for downwind use. The higher the number, the stronger the wind the sail is designed and built for. Similarly, symmetric spinnakers are often designated S1, S2, S4 or S5.
Terms such as gennakers, screechers (aboard multihulls) and reachers may also be heard. These are often applied generically, and the sails themselves may differ between different styles of boat. Therefore, when speaking to sailmakers it’s usually best to ignore the terminology and simply describe your problem and what you want a new sail to do. That way they can design the sail you need, as well as advising of any pitfalls you may not have foreseen.
As with asymmetrics, not all symmetrics are created equal. A sail designed for running, for example, tends to have broad shoulders to maximize area and a deep shape, again to help rotate it out away from the main. Before the advent of A3 asymmetrics, many racing yachts also carried smaller, lightweight, symmetrical “reaching spinnakers” with a flatter cut, to complement their downwind kites. In either case, if you happen to have one of these—or can pick one up used—it can still be effectively employed in apparent wind strengths of 10 knots or less. As an added benefit, while most of these are now old sails, many have not seen much wear and can be quite useful aboard a budget-conscious cruising yacht. It’s also nice gaining spinnaker-handling practice using a sail not worth thousands dollars!
OTHER CONSIDERATIONS
Of course, not everyone has either the budget to buy separate reaching and running sails or the space to stow them. This explains why many sailmakers offer “general purpose” asymmetric sails. Again, though, if you’re considering a single all-purpose sail it’s important to be aware of the design and shape compromises inherent in this approach. Many, for example, have a relatively small optimum wind angle and won’t achieve close angles when reaching, yet will easily collapse behind the mainsail when attempting to run at deeper angles. Before choosing a sail it’s therefore important to understand the deficiencies in your boat’s existing setup. (Note that those with large overlapping headsails will often have an easier choice, as the genoa will work well close reaching in light airs and beam reaching in heavier breezes, so the biggest gap in the inventory is a true downwind sail.)
With regard to materials, for sails other than Code 0’s, ripstop nylon remains universally the cloth of choice, usually in 0.75 and 1.5-oz. weights (although 0.9 oz. is sometimes used), while optimized light-airs race sails may be as little as 0.5 oz. When choosing the weight of cloth there are two key factors that have to be balanced—ease of filling the sail in light airs and the sail’s longevity. Unlike racers, cruisers don’t want to have to replace a spinnaker every few years, which suggests to a heavier cloth, although this can be counterproductive if the sail can’t easily be filled.
On a raceboat, for example, I like to have a heavy-duty 1.5-oz. sail in the inventory that can be used in up to 30 knots of true wind. However, given that cruising boats are most likely to use poled-out headsails to get downwind in anything much above 15 knots, their spinnakers do not have to be so bulletproof. My cruising boat therefore has a 0.75-oz. symmetrical kite for medium winds, plus a 0.5-oz. asymmetric for very light airs. That sail, which is now quite elderly, is dropped before the apparent wind reaches 10 knots. s