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#Mod70 #Foiler

C Foil on starboard, L foil on port for Gitana Team’s trimaran

Antoine Koch : "These two types of foils are linked to two philosophies of flight"

mercredi 22 avril 2015Redaction SSS [Source RP]

Toutes les versions de cet article : [English] [français]

The forms below the waterline, the size of the floats… at first glance, the Multi70 Multi70 #multi70 Edmond de Rothschild is the same boat as that which set sail from Saint Malo last November in the Route du Rhum Route du Rhum #RouteDuRhum  ! Indeed, true to its initial plan, the team opted to adapt the original platform, even though the latter has undergone some structural reinforcement. However, the 2015 version has a host of new features if we look more closely at the appendages.

The first of these relates to the aft section of the floats where the T-foil Foil #foil rudders, the principle of which was tested and validated in the Rhum, have been scaled up :

“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 Foil #foil volumes,” explains Pierre Tissier, Technical Director of the five-arrow stable.

What immediately draws the eye are the new appendages adorning the trimaran in the middle of the floats. Fully in line with its research and development ethos, the Gitana Team has opted for asymmetric foils. Indeed, whilst the starboard float is kitted out with a C-shaped foil, the port float reveals an L-shaped foil. These shapes and architectural choices are explained to us 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,” Antoine 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 America's Cup #AmericasCup 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 is the fruit of a close collaboration between Antoine Koch and Gitana Team’s design office, naval architect Guillaume Verdier and New Zealander Jamie France, American Bobby Kleinschmit as well as the Pure Design company, the latter being members of Team New Zealand.

For the Gitana Team, the completion of the refit and launch of the Multi70 Multi70 #multi70 Edmond de Rothschild is synonymous with the start of a test phase in real conditions on what is a demanding prototype. Experts in their field, the various members of the technical team will mould the machine piece by piece, one sea trial at a time. To pull this off, the communication Communication #Communication between the sailing team and the refit team will be constant. Naturally this extensive session of fine-tuning will be orchestrated by Sébastien Josse at sea. Boasting such a test platform is a huge advantage given that the information gleaned on this 21-metre trimaran will be incredibly precious for the future and for the team’s subsequent projects. According to the conclusions of the initial sea trials, the team is not ruling anything out, including a potential participation for the Multi70 Multi70 #multi70 Edmond de Rothschild in a famous transatlantic race, due to set sail from Le Havre in late October, which recently opened its doors to multihulls from the Ultime category. In the meantime though… she will have to prove herself offshore.

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