Sail Design

Guy Waddilove looks at the advantages of a new hybrid sail.

What do you get when you cross a spinnaker with a staysail? Despite sounding remarkably like the sort of joke that my three-and-a-half-year-old son would tell, the answer: The spaysail is a piece of equipment that is being taken very seriously and finding popularity from those looking for that little extra edge on the competition.

Developed by Doyle Sails New Zealand’s head of design, Richard Bouzaid, the spaysail is a flying sail that resembles a small gennaker. It is used off-the-wind in place of a staysail. The spaysail’s loose luff allows the leading edge of the sail to project forward and to windward, rather than straight from tack to head as would a conventional staysail. This makes the spaysail a very effective design for downwind sailing.

The girth of a spaysail is much wider than you would see on a conventional staysail, which gives the sail the appearance of a small gennaker, and the overall shape mimics the shape of the main gennaker. The head of the spaysail is usually attached at the rig lower than a conventional staysail would be, and the tack is slightly further aft to stop the forestay interfering with the curved leading edge of the sail.

Downwind gains

Richard Bouzaid comments: “Upwind there are very few differences in sail shape at the moment between the major sail makers. Sure there are differences in fibre path mapping, cloth weights and stretch characteristics but the basic upwind shapes are not hugely different. Downwind is where there are the major differences in design philosophies and here is where the gains are made on the water.

“We have spent a lot of time developing unique downwind sail shapes that are proven on the water, and the development of the spaysail I feel complements this and takes downwind performance up another notch.”

Development of the spaysail started about four years ago with prototypes being tested aboard Wedgetail in Australia and Wired in New Zealand. In the years since these first trials, as a better understanding of how the sails are used and handled has developed, shapes and materials have been continually refined to optimise performance.

Spaysails have been tested in the wind tunnel at the University of Auckland to give empiric evidence showing that the concept is effective and that significant gains can be made with the sails.

For Bouzaid the main aim when developing the sail, was to get something more effective than a triangle in the large gap between the gennaker and the mainsail. As many boats now do not use poles and only fly the downwind sail from a centre-line prod, the area between the spinnaker/gennaker and the mainsail has become significantly larger. Initial modelling showed that a flying type sail “looked” to be the right solution for these boats, and further testing in the wind tunnel and on the water confirmed that in certain conditions significant gains could be made.

Richard Bouzaid: “Considerable work has gone into getting the geometry and profile of the sails right, but the basic logic is that it effectively increases downwind sail area and creates a more effective area than a regular triangular staysail can”.

Better VMG

Initially spaysails were developed for VMG sailing – getting to a bottom mark as quickly as possible in typical 10 to 20 knots of true wind. Often this means being able to soak lower than the other boats without giving up speed, and this aim has been the holy grail of downwind design for all sailmakers.

More recently Bouzaid and his team have found that spaysails are also very effective in under 10 knot conditions, particularly on flat water. As apparent wind angles heat up the sails have also been found to be very effective at helping to promote planing and surfing earlier. As a rule of thumb, spaysails are effective at similar wind angles and wind speeds to a conventional staysail, but generally work out to be more efficient.

Some users have commented that the spaysail has given them an extra knot of speed downwind and allows a deeper course to be sailed by between three and five degrees when compared with a conventional staysail.

Handicap issues

The cut and sizing of a spaysail allow the sail to be measured the same as a conventional staysail, ie as a headsail. There is no restriction on the number of headsails carried under IRC but there is a restriction on the number of spinnakers/gennakers onboard.

The increased downwind sail area that the spaysail gives can allow the spinnaker/gennaker areas to be reduced, which effectively reduces the boat’s IRC rating. This strategy has proven very successful as it allows the spaysail to be close to the same size as the maximum headsail area without any penalty, and spinnaker/gennaker area to be decreased.

Spaysails were originally developed for IRC boats and boats with prods but now the range of boats flying them has expanded. They have been used with great success on heavy displacement boats with spinnakers and poles and have proved to be equally successful on 30ft sportsboats. There is no restriction on the type of boat using them, as long as there is the practical ability to set the sail on the rig.

One of the noticeable differences in terms of practical usage between a spaysail and a conventional staysail is the sheet loading. Due to the way they fly and the power that they generate, spaysails have higher sheet loadings than a conventional staysail. It is often necessary therefore to lead the sheet to a winch whereas you would usually be holding a conventional staysail by hand through a ratchet block. Like a gennaker, spaysails need to be trimmed aggressively because if they are under-sheeted they will collapse.

Deck set-up

Setting up the sail on deck requires a topping lift or some way of hoisting the sail to a point about 75 per cent of the way from the deck to the forestay attachment on the mast. The deck fitting for the tack needs to be set well enough aft from the forestay to avoid interference as the sail will fly forward and to windward.

Spaysails can be built from nylon or a light laminate. Nylon is the more cost-effective alternative and a typical price would be approximately a third of the price of the gennaker for the boat. The laminated alternative is best suited to boats 50ft and over, and while more expensive, they offer very good value in terms of the increased level of performance they can give.

One of the early adopters of the spaysail was Neil Pryde’s Hi Fi which has had great success racing in South East Asia over the last couple of years. Hi Fi dominated the Racing Class in the 2009 Singapore Straits Regatta, winning seven out of seven races as well as winning the Sir Thomas Lipton Perpetual Trophy for the lowest scoring contender of the Perpetual Cup Series. The series consists of the Raja Muda Selangor International Regatta, the Phuket King's Cup and the Singapore Straits Regatta. Hi Fi’s tactician Kevin Costin was involved in the early design and development of the spaysail, an investment that has obviously paid off for the team.

Closer inspection of a spaysail’s DNA would probably suggest that the sail is more likely to be the love child of a gennaker and a staysail rather than a spinnaker and a staysail; but the portmanteau name that this would produce would just attract too many sniggers, so it looks like the spaysail is here to stay.

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