Retractable Y-shaped foils, adjustable in three dimensions

Inspired by the appendages of the America's Cup foiling monohulls, these Y-shaped foils have a wingspan of over 5 metres. They are designed to generate powerful lift, increase power and offer a wide range of adjustments to optimise flight at every point of sail and in all conditions. Beyond their impressive size, these foils feature many unique innovations.

Revolutionary U-shaped rudders

These are probably the most visually striking innovations on the new Maxi Edmond de Rothschild. To fly high above rough seas while maintaining control, the team wanted very long rudders that would remain in contact with the water. The challenge is that longer rudders tend to flex under load, severely affecting steering and the efficiency of their lifting surfaces. A new geometry was needed to give these appendages maximum stiffness, resist cavitation and ultimately improve control of the boat and make better use of its power. The result is a set of U-shaped rudders over 4 metres long, a metre longer than those on Gitana 17. Their shape, reminiscent of a tripod or an inverted π, is only the visible part of what makes them so distinctive.

A daggerboard optimised to stabilise the boat and limit cavitation

With its wide span, the daggerboard resembles an aircraft tail assembly, with two adjustable flaps: one on the vertical section and the other on the horizontal section, the distinctive “manta-ray wing”. On Gitana 18, the innovation is to position this wing behind the vertical part of the appendage, rather than directly beneath it, to minimise flow disturbance and cavitation.

Rig: adjustable spreaders to control mainsail power while sailing

Gitana 18’s mast is 1.50 metres taller than its predecessor’s. The boom is also shorter, creating a more slender sail plan. The major innovation is a set of spreaders that can be adjusted while sailing to bend the mast fore and aft. Actuated by hydraulic rams, these spreaders can pivot through 35 degrees to adjust the bend in the middle of the mast. This unprecedented system allows the sailor to control mainsail power: adding depth in light winds to take off sooner, or flattening the sail to reduce power at high speed or in strong winds. Adjusting the depth, and therefore the power, of the mainsail can also save a solo sailor time and energy by reducing the need for risky manoeuvres or headsail changes.

Central hull:
an integrated, structural coachroof

The naval architects and Gitana design team wanted an exceptionally stiff, structurally robust platform. This applies both to the floats, which must withstand heavy loads from the foils and rudders, and to the central hull, which is subject to torsion. The enclosed coachroof is integrated into the hull and contributes to its structural strength. Inside, the cockpit brings all sail-handling controls together, with ergonomics shaped by many hours of design and development. The coachroof also stands out for the number and size of its windows. This configuration meets the visibility requirements of the Ultim class rules and gives sailors the best possible view to keep a visual watch.

28.01.2008

Back up to speed.

par Gitana

We are encountering our first dark nights as the waning moon is rising later and later. In the celestial sphere, the Southern Cross is where it should be, to port, as we are on a heading of 240° in order to ride the western edge of a high-pressure system here in the southern hemisphere. It took quite an effort to reach this system! We were hoping to catch it easily, only 48 hours after crossing the equator. But the stormy depression that built up as we entered the Doldrums changed the equation. Now that we are again cruising full-bore toward Cape Horn, we can estimate the amount of time lost: a full day of sailing, around 500 nautical miles. First, the stormy low-pressure system weakened the southeasterly trade winds to about 10 knots. We then had to cross the related low-pressure trough, the dangerous zone where the winds rotate freely and there is also a windless zone whose size depends on where you hit it. This stretch cost us five hours—five hours at a near standstill overnight from Saturday to Sunday, our first “pit stop” so far. This was the lesser of two evils given the extent of the low-pressure trough…our thanks go again to Sylvain Mondon in Toulouse who guided us with a sure hand, keeping us informed with satellite photos and other GRIB files. And then there’s the question of interpreting the photos and files…Lionel and Dominic spent many hours at the map table.

Once past the low-pressure trough, we picked up speed rapidly. I’m always surprised at how the weather conditions can differ so widely over such a small distance—only around 10 miles. We went from zero to 20 knots of wind! For us, that translates into an average speed of 25 knots. A sigh of relief. Yesterday we managed to cover 350 miles despite our pit stop in the middle of nowhere. Today we should be able to knock off more than 600 miles. We are zipping right along under the solent and two reefs, with 30 knots of wind and a real wind direction of 120-130°. As soon as the breeze moves aft, the small gennaker will come out of its bag. That’s the next sail change planned on Gitana 13.

Good night

Nicolas Raynaud

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