Many owners of cruising boats ponder what the best option is for reaching and downwind sails. This has been further confused by the rapid rise in popularity of furling code zeros. Rupert Holmes looks at the options.
Why have downwind sails?
Other than in strong winds, the standard mainsail and roller furling genoa of most yachts are not efficient when sailing with the wind on or abaft the beam, which is roughly 50 per cent of the time. This is particularly marked in light airs, where they simply won’t generate enough power to drive the boat and the engine is inevitably used instead.
But why do so when conditions are perfect for a lovely gentle sail? A lightweight reaching or downwind sail will often propel you at least 50 per cent faster than just the main and jib – maybe at six knots instead of four, meaning there’s no need for the engine.
Note the distinction in the paragraph above between reaching and running sails – no single sail can do both efficiently, other than on exceptionally high-performance craft that are so fast that the apparent wind is always forward of the beam and they therefore they don’t need a running sail.
It’s also worth emphasising that these sails can be really useful additions to a boat’s inventory without ever being used in lots of wind. While racing sailors love to push the boat as hard as possible in a blow – often surfing or planing at speeds well into double digits – the cruising sailor has no need of the challenges associated with sailing at these speeds, when conventional white sails will drive the boat easily at close to hull speed.
With the advent of reliable furling systems for code zeros and some asymmetric spinnakers these sails can now also be very easy to handle. This is especially true if they are used only in light airs. Granted, some knowledge is needed, but nothing like the skill required for competitive strong wind racing and there’s much less scope for anything to go badly wrong.
Reaching sails and code zeros
These tend to be relatively flat cut to allow tighter angles to the apparent wind to be sailed. Cruising code zeros may be built from nylon or, more usually, from a super-lightweight Dacron or laminate material – generally little more than 1.5oz for a 36-38ft boat. In some cases the sail shape has more similarity to that of an out-sized genoa than a downwind spinnaker.
In many people’s mind such a reaching sail is typified by the code zero of some racing boats. However, this sail is often something of a compromise, with the shape and size dictated by the need to avoid a handicap rating penalty. As a result, racing code zeros tend to be large sails that can’t be used at really tight wind angles. Cruising boats are not subject to this problem, so their gennakers can be smaller and flatter cut, allowing for apparent wind angles of as little as 50 degrees in light airs.
Most standard older cruising chutes were ‘general purpose’ reaching sails that aren’t designed for close reaching, but will cope with the wind a little further aft than code zeros. However, even then few are stable at apparent wind angles bigger than around 140 degrees.
Conventional symmetric spinnakers flown from a pole will happily sail with the wind dead aft, but even those cut for reaching will struggle to work efficiently with apparent wind angles much forward of 100 degrees. Traditionally running sails are cut to be as large as possible, with broad shoulders to project as much area as possible. However, a symmetric spinnaker cut for reaching with a flatter shape narrower shoulder will still set with the wind aft. This will be easier to handle and require less accurate helming – both important considerations for cruising boats.
Asymmetric sails cut for downwind sailing have a pronounced curved to the luff that enables the sail to project to windward of the forestay and therefore to windward of the mainsail. Even so, they don’t work with apparent wind angles greater than 160 degrees. As that means the boat’s course can’t wander beyond that figure without risk of the sail collapsing the effective limit for many cruising crews will be around 150 degrees.
With good sail handling systems you never need to worry about gybing the sail – the manoeuvre that’s most likely to cause race crews problems. Instead you can furl or snuff the big sail, gybe the mainsail at your leisure, then re-set the kite once you’re settled down on the new course. With a good pilot it’s easily done single-handed.
A perfect compromise?
If no single sail will cover all wind angles, what are the alternatives? In an ideal world, three sails would cover the entire range of off-wind angles. However, few cruising have room for more than two such sails. The most common compromise is therefore a cruising code zero that can be used at apparent wind angles of less than 60 degrees in light airs is clearly an attractive option, but will not set well with the wind aft of around 100/110 degrees.
An asymmetric spinnaker cut for downwind use) can be used at apparent wind angles from around 100-150/160 degrees. Both these can be set on furling gear – if necessary on a short (often retractable) bowsprit that will keep the sail and lines clear of the anchor, pulpit and other paraphernalia at the bow. Alternatively if the boat is already equipped for using a symmetric spinnaker this can be an option that covers a broader range of downwind angles than the asymmetric sail.