Foiling MOD70

The next step is revealed in the latest mods to Gitana XV

In refit since her return from Guadeloupe in December, the Multi70 Edmond de Rothschild left her technical base in Lorient on Wednesday morning returning to the water and her berth in the Keroman submarine base.

For the Route du Rhum last year, the team created in 2000 by Baron Benjamin de Rothschild carried out various modifications to its former MOD70 especially to her foils with the addition of T-foil rudders, etc.

The aim at that time was to give skipper Sébastien Josse the possibility of competing with the giant multihulls in the Ultime class; the largest of which measuring almost twice the size of the Multi70.

But in her latest transformation Edmond de Rothschild is to become the first flying trimaran on the offshore racing circuit.

The team loves this type of ambitious challenge and the 3rd place posted by Josse into Pointe-à-Pitre proved them right, as General Manager Cyril Dardashti observes: “From the outset our idea has been to try to get an oceanic trimaran flying offshore. The refit period we had last year prior to the Rhum wasn’t long enough to carry out all the necessary work. As such, it was decided that the process would be completed in two stages. Sébastien’s performance in the Rhum enabled us to consolidate our choices. Phase 2 is underway and we’re eager to see the boat put in her first tacks in her 2015 configuration.”

Looking at her platform, the Multi70 Edmond de Rothschild is the same boat as she has always been, however less obvious is that this has undergone some structural reinforcement. However her appendages have been updated.

The T-foil rudders, tested in the Rhum, have been enlarged, as Technical Director Pierre Tissier explains: “The rudders have been extended both along the vertical section and the lower section. We’ve had new rudder elevators made so as to increase the surface area of the foils. The latter elevators are twice the size they were last year, which is essentially to balance out the platform following the added foil volumes."

However the biggest change is to her main foils. In line with its research and development ethos, the Gitana Team has currently opted for a foil configuration in each hull. So in the starboard float is a C-shaped foil while in the port float is an L-shaped one.

These shapes and design choices are explained by Antoine Koch, head of the Gitana Team’s design office: “With Gitana XV we’re in the process of carrying out research and performing trials so we’re using the platform as a laboratory for the Gitana Team’s future projects. To date the theoretical studies reveal two types of foils, which we’re hoping to trial. The C-shaped foil is a very efficient appendage in terms of hydrodynamics as it generates very little drag. Its ability to generate vertical lift is well established. Although we’re interested in flight, this form does lack stability. In contrast, the L-shaped foiled generates significant drag but it provides great stability and hence a sizeable saving in relation to the drag created by the platform itself. The boat’s handling at sea with such appendages remains a great unknown, but that is what is the interesting element to gauge in real conditions,” Koch stresses.

“These two types of foils are linked to two philosophies of flight. However, it all depends on what you call flight in offshore racing in big seas. Today, during inshore races, the boats in the last America’s Cup showed that one L-shaped foil, despite the drag it causes, is a more high performance compromise. However, the AC72s didn’t have the sea and swell parameters to take into account. That makes all the difference and it’s the primary difficulty that we’re currently trying to get our heads around.”

As with the first T-foil rudders, this second phase of modifications comes from a collaboration between Antoine Koch, Gitana Team’s design office, naval architect Guillaume Verdier and New Zealander Jamie France, American Bobby Kleinschmit as well as Pure Design who are part of Team New Zealand.

Gitana XV will now undergo a test phase with experts in their fields and various members of the technical team will eke out the bugs of the new developments, all overseen by Séb Josse.

Tomorrow the boat will set off on the first of these out of Lorient, but the 70ft trimaran will make her competitive debut on 9 May in the Tour de Belle-Ile. This 42 mile race, which is the French equivalent of Britain's Round the Island Race sees more than 400 yachts competing and, weather permitting, the Gitana team will also be fielding its modified GC32 foiling catamaran Edmond de Rothschild. The helm of his will be entrusted to Gurvan Bontemps, a 2015 recruit to Gitana Team, with a wealth of experience in ‘small’ cats, including several Formula 18 titles (double French champion, world No.2…), plus several years as demo sailor for the Flying Phantom.

The developments being made to the MOD70 turning her into a full foiler, are believed to be the test bed for a new 'Ultimate' flying 100ft Gitana.