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.

12.11.2013

Abeam of Cape Verde.

par Gitana

Nicely positioned on the tradewind expressway in a well-established north-easterly breeze, Edmond de Rothschild and Oman Air Musandam are continuing their rapid descent of the North Atlantic bound for the equator. Late this afternoon, the two travelling companions left the first islands that make up the Cape Verde archipelago abeam of them. Sébastien Josse and Charles Caudrelier were the first to put in a gybe to set a course to the west, while the Gavignet Foxall duo opted to continue their journey southwards. These differences in viewpoints explain why the Omani boat appears to have made up some ground at the 1600 GMT position report. In fact, each of the crews is refining its trajectory as it prepares to tackle the infamous Doldrums and, most importantly, adjust the point at which it hopes to enter the latter weather phenomenon.

Life at speed

Sébastien Josse has a clear voice when he calls his shore crew at midday: “The dampness is a constant aboard. We’re making fast headway and the deck is being washed by the spray. For the past forty-eight hours though, conditions have been much more manageable. We’ve succeeded in taking it in turns to get some rest and last night was a lot more pleasant than those that have gone before with some long siestas lasting nearly 2 hours. We’re running a more normal watch system now with two hours at the helm and each of those sessions followed by two hours of rest, during which we can eat, get the latest information sent by our routers and sleep,” the skipper of Edmond de Rothschild explains.

Despite the average speeds maintained by the 70-foot one-designs over the past few days – nearly 600 miles was covered by Edmond de Rothschild in the past 24 hours – it shouldn’t be forgotten how demanding and precise the piloting has to be on machines such as these when they’re powered up making between 25 and 30 knots: “The periods at the helm are really intense and our eyes rarely leave the true wind indicator. If you crack off 5° the boat takes off, but if you pinch 5° too high the boat comes to a standstill. We’re on the attack and that doesn’t leave a lot of time for reflection. On my last watch, it was only when I passed the helm to Charles that I noticed the trampolines were full of flying fish!” Sébastien Josse says with an amused air, the anecdote indicative of the degree of concentration required on a constant basis aboard the trimaran fitted out by Baron Benjamin de Rothschild.

At the gateway to the Doldrums tomorrow

From tomorrow, the organisation described above by Sébastien Josse is likely to be under pressure once again with their predicted entry into the infamous Inter-Tropical Convergence Zone (read the low-down below). Indeed, tomorrow, the two 70’ trimarans will make their grand entrance into the Doldrums, a passage famed for its meteorological instability, which often turns into a headache for the navigators. “This transition zone is always stressful as you can lose all the credit you’ve acquired over previous days here. It’s a place where you have to deal with a series of squalls and both of us are sure to be on deck together so that we’re ready to react as quickly as possible,” concluded the skipper of Gitana Team.

From this evening through until their exit from the Doldrums, the sailors will switch mode so that they can focus on dealing with a given situation at short notice with the emphasis on observation.

Low-down on the Doldrums or the Inter-Tropical Convergence Zone (ITCZ)

A dreaded navigation zone, the Doldrums consist of a belt of low pressure zones around the Earth and bordering the equator, which span several hundred kilometres from north to south. They are formed by the convergence of warm and wet anticyclonic air masses moving in from the tropics and carried along by the tradewinds. As a general rule of thumb, they are characterised by some sizeable cumulonimbus formations.

Ranking on Tuesday 12 November at 1600 GMT:

Edmond de Rothschild (Josse-Caudrelier) 2,965.4 miles to go /28.3kt average over 2 hours
Oman Air-Musandam (Gavignet-Foxall) 29.9 miles behind the leader /29.1kt average over 2 hours

Retourner aux articles

Heritage