Rev­o­lu­tion­ary tri­maran will foil solo at 50 knots

This rad­i­cal new 100ft Tri­maran is de­signed To do 50 knots across The open ocean. elaine bunting Talked To her de­signer

Yachting World - - Front Page -

Arev­o­lu­tion­ary 100ft fully foil­ing ocean-go­ing tri­maran ca­pa­ble of cov­er­ing more than 900 miles in a day and sail­ing at speeds of 50 knots was launched in July. De­signed by Guil­laume Verdier, the foil ge­nius be­hind the Amer­ica’s Cup win­ning Emi­rates

Team New Zealand, Gi­tana 17 is de­signed to be sailed solo and to beat the round the world record.

Gi­tana 17 is the lat­est of the race boats backed by Baron Ben­jamin de Roth­schild. The 100ft ‘Ul­time’ tri­maran is the cul­mi­na­tion of three years of work by the team and brings to­gether de­vel­op­ments from ar­eas as di­verse as the IMOCA 60s, the Amer­ica’s Cup and MOD70 tri­marans.

This is a beast of a boat and sig­nif­i­cantly dif­fer­ent from oth­ers in the grow­ing ‘Ul­time’ class such as François Gabart’s MACIF and Thomas Coville’s Sodebo Ul­tim. For the first time, this is a boat de­signed around foil per­for­mance.

High av­er­age speeds

Ac­cord­ing to the de­sign team, Gi­tana 17 will foil at speeds of 48-50 knots in 1625 knots of true wind and seas of 6-8m – typ­i­cal At­lantic con­di­tions. It could also sail across the South­ern Ocean in non­foil­ing mode at up to 40 knots.

“Foil­ing is not that [hard] but to do that and be stable in waves is a lot more dif­fi­cult and this is a first stage to do­ing that,” ex­plained Verdier. “Pre­vi­ously the boats were de­signed to go off­shore and slowly the foils got into that, but we have de­signed the ap­pendages as a prin­ci­pal [part] and tried to have a plat­form that goes well with that.

“It makes a boat that is a lit­tle heav­ier be­cause there are more sys­tems to con­trol the foil, more hy­draulics and the plat­form is stiffer in tor­sion.”

The foils on Gi­tana 17 share some com­mon think­ing with those on the Amer­ica’s Cup boats – the outer float foils are an L-shape. The main dag­ger­board on the cen­tral hull, how­ever, is a shape never seen be­fore on these boats and fea­tures a large hor­i­zon­tal com­po­nent to help with roll con­trol.

The con­cepts were evolved through 2014 and 2015 on Gi­tana 15, the MOD70 now known as Gio­vanni Sol­dini’s

Maserati. The team fit­ted one hull with sev­eral foil shapes to un­der­stand their per­for­mance off­shore. “One of the is­sues we had was that it was fairly un­sta­ble, rolling-wise, and an el­e­va­tor on the stern [alone] would not be enough for sin­gle­handed con­trol. So we in­tro­duced this el­e­ment,” ex­plained Verdier.

In­ge­nious rud­der sys­tems

The T-foil rud­ders on the outer hulls are an in­ge­nious and com­plex so­lu­tion and de­signed by the Gi­tana Team. They fea­ture el­e­va­tors to ad­just trim and are op­er­ated by a hy­draulic sys­tem mon­i­tored by soft­ware. But they can also kick up if they col­lide with some­thing in the wa­ter, and be raised out of the wa­ter.

The wind­ward rud­der is very ex­posed to slam­ming from waves when reach­ing, so can be lifted up, locked into the hull and dis­con­nected from the con­trol sys­tems. A large hous­ing that you can see pro­tects the rud­der and con­trols.

Verdier says that these foils are “a bit like the AC72 foils; they are auto-stable”.

He ex­plained: “They be­have a bit like a he­li­coil. When the boat raises up in the wa­ter it makes more lee­way, and when it makes more lee­way there is a com­po­nent of the force that pushes you down.”

Ac­cord­ing to Verdier, Gi­tana 17 could one day foil at over 50 knots. “But when foil­ing we are lim­ited by cav­i­ta­tion, so if we wanted to go above that we’d need to have dif­fer­ent pro­files and aero­dy­namic as­pects, and struc­ture of the boat. It’s a bit of an un­known ter­ri­tory, but maybe we should be able to do 53 or 54 knots.”

The main aim of the de­sign­ers, how­ever, is to im­prove the boat’s av­er­age high speed po­ten­tial, and Verdier says that Gi­tana 17 could reach 900 miles in 24 hours – the much big­ger fully crewed 130ft cata­ma­ran Banque Pop­u­laire V holds the record of 908 miles. This could be an ul­ti­mate record-breaker, though the qui­etly spo­ken French de­signer hes­i­tates to say so. “I could pick any crazy num­ber,” he smiles. “It’s pre­ten­tious to say. We have to wait a lit­tle.”

See our video of Gi­tana 17 on Yacht­ing World’s Youtube chan­nel.


Be­low: de­signer Guil­laume Verdier speaks about the boat at her launch from Mul­ti­plast in Vannes

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