dimanche 29 décembre 2019

100 footers in the 75th Sydney-Hobart 2019 - Comanche: a third win in five contests


The victory went to the Maxi 100 Comanche, - Saturday 28th December 2019, at 7.30am, after a stressful final for the skippers and their crews, on the River Derwent, in a near nil wind ... 
©F Chevalier
Alas, this 2019 edition will be remembered for the tragic spectacle of the wildfire nightmare that ravaged - the word is feeble - the Australian forest as the starting line in Sydney.
©F Chevalier
In any case, the winner Comanche completed the course - 628 miles - in one day, 18 hours, 30 minutes and 24 seconds, nearly 45 minutes ahead of its chaser, InfoTrack

©F Chevalier
The record for the event, set by the same Comanche in 2017 and which was 1 day, 09 hours, 15 minutes, and 24 seconds, has therefore not been broken.
©F Chevalier
Winner of the event nine times, Wild Oats XI took third place, beating Scallywag by 38 split seconds in the fourth place....

The fifth Maxi 100 to cross the finish line will be Black Jack IV.

Yacht Specifications:


Maxi 100’
Designers: VPLP et Guillaume Verdier.
Builder: Hodgdon Yachts, Boothbay, Maine, USA
Launched: 27 September 2014
LOD: 30,48 m
LWA: 30,48 m
LWL: 30,25 m
Beam: 7,85 m
Draft: 6,67 m
Air Draft: 45,75 m

Bowsprit: 3,70 m
Displacement: 29,5 t
Main Sail Area: 410 m2
Sail Area (upwind): 760 m2

Sail Area (downwind): 1 400 m2

 Infotrack (ex-Perpetual Loyal, ex-Rambler 100, ex-Speedboat)

Maxi 100 pieds
Designer: Juan Kouyoumdjian
Builder: Cookson Boat, Auckland (N-Z)
Launched: 17 April 2008
LOA: 30,48 m
LWL: 29,99 m

Beam:  7,35 m

Draft: 6,22 m

Air Draft:47 m

Bowsprit: 5 m
Displacement:30,6 t
Ballast: 8 t
Main Sail Area: 375 m2
Sail Area (upwind): 660 m2

Sail Area (downwind):: 1 340 m2

 Wild Oats XI 

Maxi 100’
Designer: Reichel/Pug
Builder: McConaghy, Sydney
Launched: 2nd December 2005
LOA:  30,48 m
LWL: 30,48 m
Beam:  5,10 m
Draft: 5,94 m
Air Draft: 44 m

Bowsprit: 4,15 m
Displacement: 31 t
Main Sail Area:  390 m2
Sail Area (upwind): 630 m2

Sail Area (downwind): 1 400 m2

 Scallywag (ex-Maximus, Investec Loyal, Ragamuffin Loyal, Ragamuffin 100)

Maxi 100’
Designer: Andrew Dovell
Builder: Cookson Boat, Auckland (N-Z)
Launched: February 2005 (Maximus)
LOA:30,48 m (ex 98’ Greg Elliot & Clay Oliver design)
LWL: 30,48 m
Beam:  5,80 m
Draft: 5,60 m
Air Draft: 45,10 m

Bowsprit: 4,40 m
Displacement:33 t
Main Sail Area: 395 m2
Sail Area (upwind): 630 m2

Sail Area (downwind): 1 400 m2

 Black Jack IV (ex-Esimit Europa II, ex-Alfa Romeo II)

Maxi 100’
Designers Reichel/Pug
Buuilder: McConaghy, Sydney
Launched: 2005
LOA: 30,48 m
LWL: 30,48 m
Beam:  5,19 m
Draft: 5,80 m
Air Draft: 44 m

Bowsprit: 4,25 m
Displacement: 34 t
Main Sail Area: 360 m2
Sail Area (upwind): 600 m2

Sail Area (downwind): 1 400 m2

mercredi 18 décembre 2019


The new flying mono hulls 
of the America's Cup
©F Chevalier

Amazing, the difference in the architectural solutions chosen by the design teams for the first four ac75s launched recently. On their blank sheet of paper, or rather their monitors, they started from a rather basic box rule, with a hull length of 20.70 meters, a maximum beam of 5 m, a displacement of 7.6 tons including two foils with ballast weighing 1215 kilos each, and a few contingencies. Two limit measures, at 17 and 19 meters from the stern are imposed to prevent scows, a minimum freeboard of 1.50 meter in one spot; the position of the mast and the length of the boom are both determined. An important measure, which helped us to reconstitute these drawings, considering the distortion of shapes that appears in most photos, is the distance between the two axes of foil rotation, i.e. 4.10 meters. The distance between the two axes of foil rotation is 4.10 meters. The distance between the two axes of foils is 4.10 meters. In fact, the 75 feet, or 22.86 meters, corresponds to the overall length, including the bowsprit.

©F Chevalier
Indeed, on the drawing view, there are radically different designs, both on the general shape and on the drawing of the waterline. Of course, the sections also display a wide variety of layouts. All these hulls are designed to lift off as fast as possible, and to offer the best hydrodynamic performance during the transition periods, between displacement sailboat and flying boat, then the best way through the air when they are in flight. The AC75 is relatively light, its weight can be compared to a 3.80 meters surfboard, boarded by a 35-kilogram teenager. 

Defiant, built by American Magic, is the narrowest yacht, its foil rotation axes extend beyond the width of the deck. 
©F Chevalier
The hull is that of a surfboard, with a small raised section around it, wide and full, with very shallow depth. 
©F Chevalier
DEFIANT sail plan
The waterline is short, with a more stretched line at the front. At 15 degrees of heel, an improbable or transitory situation, the hull has a narrow volume guaranteeing the minimum area wetted and a good stiffness.

INEOS' yacht, Britannia, is at maximum three fifths of its length wide, and the bow is full, at the limit of the rule measurements. Its waterline is symmetrical at the bow and stern, oval-shaped, the sections of its hull are more V-shaped than the American racer.

©F Chevalier
When heeling, the waterline is very long, the shapes soft and planning. Its lateral sidewall provides it a greater stiffness than its competitors. The Design Team has found a small loophole in the rule and has not hesitated to create a gap between the deck book which should be 1.50 meters and the deck which remains at the same level as the front deck and remains 36 centimeters below the deck book at its highest point. The deck runs from the bow to the mast horizontally, then goes down to the cockpit level on the mainsail track, radically lowering the center of gravity of the whole deck. 

©F Chevalier
BRITANNIA sail plan
Seen from the side, we can wonder about the usefulness of the great wall of the vertical side, with a surface area of more than ten square meters, we guess it is warranted by an additional wind surface area, while the other challenges have sought forms with a minimum one.

As Grant Dalton, manager of the 2021 America's Cup, announced, the AC75 rule allows a great deal of freedom in hull design, and the Italian Luna Rossa Design Team, Luna Rossa, has not been lacking in originality. 
©F Chevalier
The shapes from the bow are straight, up to the foil support, then narrow on the aft. The waterline is close to a faultless lozenge, sharp on the front and on the aft. A kind of long keel runs from the bow to the rudder, with a very wide-open garboard. 
©F Chevalier
LUNA ROSSA sail plan
It is true that this shape is the result of hydrodynamic research during the transition phase, between stationary and in flight, as well as its coming back when the lack of wind or any maneuver causes the sailboat to be lowered into its element. When Luna Rossa heels, its bottom is close to horizontal, but its keel must induce some distortions in the water lines.

While designing the lines of TNZ, Te Aihe, we noticed that the AC75 rule was radically different from the rules that are in use in France for Open, Mini Transat, Open 40 or IMOCA mono-hulls. We remember Jean-Marie Finot's speech, which made it clear in all these rules that there can be no inflection point on the sections of these sailboats. Finot dominated the races at this time and was keen not to be overwhelmed by radical architectural options, as some of them were at that time.

©F Chevalier
The AC75 rule only states that a horizontal can only cut the section twice. If this prohibits double hulls, and hollows in the bottoms, it gives way to an overlay of hulls, with inflection points. 

If we consider the evolution of the central hulls of oceanic trimarans since they have been fitted with foil dagger boards, we can see that there is a real superposition of hulls, a bulky hull at the top, and a round hull below, to minimize the wetted area as soon as the hull is lifted a bit. 
©F Chevalier
TE AIHE sail plan
An influential member of Te Aihe's Design team, Guillaume Verdier, well aware of this evolution in multihulls, has been able to use this solution by superposing an ultra-light TP52 hull, with flat bottoms and flared sides, on a canoe hull. As soon as the sailboat is lightened by the foils, the submerged volume is reduced to a canoe hull, with a minimum of wetted area. When heeling, the hull slides on the sloped side, which is ideal for planning.

All these designers and engineers have worked, some of them since 2010, on multihulls. This has had a profound impact on the organization of sailboat maneuvers in the America's Cup. From the very first studies on the test yacht The Mule, the New York Yacht Club's challenge, American Magic, we can see two separate cockpits, one on the port and the other on the starboard side. 

©F Chevalier
As regards the double sail, the challenges are still to analyze how best to maximize the profitability of the lower part of the mainsail and optimize the plate-like effect of the deck that tilts up to the mainsail sheet rail, between the two cockpits. While for years, on the America's Cup Classes, the winches had to be located on deck, the eleven crew members are hidden in their cockpits, offering no resistance to the wind. At the speeds reached by the AC75, we are talking about 50 knots, the apparent wind is such that the sailboat is upwind with a beam wind.

The fifth yacht planned, from the American Stars & Stripes challenge, has not yet been built, and already the challengers and the defender are working on their second yacht, which should be launched next summer, for the first ones. 

It was interesting to review the benefits of the different architectural options from now on, knowing that the challengers do not have the right to confront each other before the first official meetings, the AC World Series in 2020. It is conceivable that the second boats launched, which are allowed to be launched from 20 February 2020, will have benefited from each other's innovations and that the differences will be less pronounced.

©F Chevalier

Aera of Buancy


Overall length: 22.86 m
Hull length: 20.70 m
Beam: 5 m
Beam foils out: 16 m
Draught: 5.50 m
Air draft: 28 m
Solent: 90 m².
Genoa: 205 m²
Upwind sail area with solent: 256 m²
Sail area downwind: 371 m²
Displacement: 7.6 t
Crew members: 11

The Mule
Length: 11.58 m 
Beam: 3.30 m
Beam foils out: 8,10 m
Maximum draught: 4.95 m
Air draft: 18 m
Minimum wind for take-off: 5 to 7 knots
Mainsail area: 52 m².
Jib area: 34 m² 
Displacement: 1.8 tons
Crew members: 5

samedi 14 décembre 2019


IMOCA 2019 


©F Chevalier
Hugo Boss
More stiffness, planning shapes, but more wetted surface.
It is still a little early to know which of the two IMOCAs is the fastest, Hugo Boss or Apivia. Who could have said during the last Vendée Globe that the next ones will fly. It was then a question of lightening the hull, reducing drag, even the architects said they didn't know if the foils brought more speed over a long distance. As a result, the first three were foil-fed, the second having lost its advantage by losing a foil. Then there was a second generation of foils, but the competitions were missing and those that took place were not conclusive. The first to really fly, Charal, gave us a great demonstration. Yes, he is flying! And it's off to a good start for them all to fly. 

© F Chevalier
Hugo Boss
Alex Thompson likes knife cut hulls and straightforward options, his sailboat slides on a board, whether it's flat or no. The spray and sea water could fill the cockpit, it is removed!

Bruno Troublé's first reaction when I told him that the first two monohulls launched for the America's Cup had totally different shapes, he simply replied that it didn't matter, they would be above the water! However, two teams of about twenty big heads have been working on the shapes of these hulls, because these sailboats fly, but also return or fall back into the liquid element.
©F Chevalier
Less stiffness, round shapes, supported on a rail, little wetted surface.

©F Chevalier
A narrow hull with a maximum beam set back to the transom, a round, soft hull, surrounded by a step to ensure a close up, the result of the collaboration of the architect and the skipper does not lack originality.

The same will apply to IMOCAs, whether due to lack of wind or sea conditions. And even more, the 60' Open rule provides for two rudders, but their definition prohibits any winglet or carrier plane, and there is no question of giving them the slightest curve. "All leading and trailing edge points must be in the same plane."  Too bad, a curvature would have arranged well the architects who are working on these sailboats that are missing a paste. However, there is no limitation in the gauge on the shape of the foils, which could take the shape of the small planes seen under the windsurfing boards, because the skipper flies with a very precarious balance, and his boat rears up to find a support point on the back of the hull between two flights.

It is more and more difficult to reconstruct a lines the best time to read the lines of these boats is during the rollover test session, and I didn't have the opportunity to go there for the last 6 IMOCA launched.

To simplify the study of the evolution of the design of these 60', I chose two sailboats that left the shipyard in August, Hugo Boss and Apivia. Several reasons for this choice, Alex Thomson's sailboat, a VPLP design, offers radical and original options, and Apivia is Guillaume Verdier's recent first plan. The fact that the previous winners were signed by VPLP / Guillaume Verdier seemed to me one more reason to analyse that it is the share of each of these architects in the success of the first two places since 2012, or at least which architectural options resulted from their competition.

Of course, the share of the skipper's preferences of each yacht in the general choices is also taken into account. Charlie Dalin is a trained naval architect and has followed Guillaume Verdier's Apivia design in every detail, he says, "I was at the heart of all the choices".

For his part, with his experience in the plans on which he has sailed, as varied as Marc Lombard, Juan Kouyoumdjian, Finot-Conq, Farr Yacht Design, and the duo VPLP / Guillaume Verdier, Alex Thompson has had time to get an idea of the sailboat that would finally allow him to win a Vendée Globe.  His choice of VPLP, which had just designed the first IMOCA of the new generation for Charal, seems to be the logical continuation of his approach to obtain a sailboat that is as gliding as possible, with a reserve of power in the event of foil failure. His last experience, where he led a hell of a train until one of his foils encountered a floating object, made him want to protect himself from an overly radical option. Indeed, he had relied on his foils to obtain stiffness, by choosing a narrower sailboat with less drag. Also, the VPLP firm designed a powerful sailboat, with a beautiful width, 5.70 meters, a flat bottom that widens in planes parallel to the surface of the water at the list. and a bilge that starts from the bow just above the water and rises high on the transom. We find these flared shapes on the transom of the latest generations of TP52, these ultra sophisticated racing monohulls, a little heavier than the IMOCAs, displacing 7.5 tonnes for 15.85 metres in length. These flared plans allow the sailboat at the lodge to leave quickly for the planning. Faithful to his image as a destroyer of preconceived ideas, Alex went even further by refining the front axle, creating an even larger cut section than on the previous Hugo Boss. If the bottom of the bow is as flat and wide as possible, at the limit of the width allowed by the gauge, the bottom rises towards the bilge in the same inclined plane as at the stern. As Alex likes them, the shapes are cut with a knife, the sailboats have to fly or plane! The roof caught the attention of all those present at the first exit of the sailboat and was surprising in its length, original shape and colour. Actually, there's no cockpit, Alex is manoeuvring from the inside. All common manoeuvres open in the centre and are spread over four winches controlled by a column in the centre. 

©François Chevalier
Hugo Boss
More stiffness, planning shapes, but more wetted surface.
Less stiffness, round shapes, supported on a rail, little wetted surface.
Above the winches, the screens display the data and monitor the outside with 360° cameras. A tiller allows you to steer without leaving the boat. The deckhouse extends to the mainsail listening rail and the sea water dives aft without filling the floor, which is reduced to a minimum. Knowing that the previous generation of 60' could take more than five hundred litres of seawater into their cockpit, Alex preferred to design an enclosed cockpit for manoeuvres and let the water and spray pass over it and remove obstacles so that they would not have the possibility to seal the sailboat's balance.

©F Chevalier
Hugo Boss
Large flotation width at the heel, but planing shapes.
Narrow and hollow-deep flotation based on its step.
One would have thought that the shapes of the new IMOCAs from VPLP and Guillaume Verdier would be at least from the same family. However, he has nothing to do with it. It even seems that there has never been such a difference between two IMOCAs released in the same month. Guillaume worked on the reduction of the wetted surface, a hull that hangs on a rail over the entire length of the sailboat, on the flow of sea water and spray, on the centre of gravity of the hull and rigging. He took particular care of the hull for the light airs and all the transition phases. The result is a narrow hull, barely 5.35 metres, with the maximum beam on the transom, from a bilge just above the waterline, a hollow cake, slightly pinched at the front, surrounded by a very marked step. The centre of gravity is far to the stern, even more so than in the VPLP plane. While the middle beam is well defended and has a large clear edge, with a rounded bilge and soft shapes, the deck is gutter-shaped from the front, until it reaches a depth of forty centimetres at mast level. As a result, the centre of gravity of the rigging has dropped accordingly.  The only common point between Hugo Boss and Apivia, the bottoms on the back have a slight inflection point for "rocker", initiated by Juan Kouyoumdjian on Bernard Stam's Cheminée Poujoulat.

© F Chevalier
When flying, the sailboat is in unstable balance, its keel sail helps it to hold, but its centre of pressure is very close to the foil's. The sailboat has a very narrow and hollow float that rests on its step. At the slightest change in wind force or in front of a wave, the balance can be disrupted and the sailboat falls back on its stern.
On both yachts, the choice of foils is as different as the hull shapes. Hugo Boss is equipped with large semi-circle shaped foils, while Aviva rests on a very wide U-shaped foil, the hollow of the U being parallel to the water at the heel, which gives it more stiffness. In flight, when the sailboats rest on their stern, Aviva landed on her spoiler, while Hugo Boss fell on the flat surface of her flank. 

©F Chevalier
One could imagine a possibility of stabilizer, like windsurfing or kitesurfing foils, in the shape of a small plane that would be fixed just before its tip, the tip of the foil.
The regulations do not mention an impossibility, but the torsional forces are already considerable, and this appendix would certainly twist the profile.
This study could have been accompanied by an analysis of Arkea-Paprec by Juan Kouyoumdjian, which is not lacking in originality. But it seems to us that this comparison is already quite tricky for the average person, and we reserve for ourselves an analysis of the four architects who have worked on the new IMOCAs, after the first new generation of foils, by the Vendée Globe. 

©F Chevalier
Architects' expectations are clear, given the instability of IMOCA theft. It is time to modify the gauge and allow fins on the rudders, or at least, as here, that they can have a curvature. We will have to wait until the end of the next Vendée Globe to hope for this possibility.
Despite the frustration of architects, this class, which is the freest of all, is growing rapidly and its future is well secured if it can adapt to new challenges. Three particular points that could relaunch architectural research, the possibility of adding foils on the rudders, the one that blocks the width of the bow and the one that prevents the inflection points on the sections of the hull...

lundi 9 décembre 2019

IMOCA 2019 - VPLP contre Guillaume Verdier

IMOCA  2019 - VPLP contre Guillaume Verdier

©François Chevalier

Il est encore un peu tôt pour savoir lequel des deux IMOCA est le plus véloce, Hugo Boss ou Apivia. Qui aurait pu affirmer lors du dernier Vendée Globe que les prochains voleront. Il était question alors d’alléger la coque, de diminuer la traînée, même les architectes affirmaient ne pas savoir si les foils apportaient plus de vitesse sur une longue distance. Résultat, les trois premiers étaient à foils, le second ayant perdu son avantage en perdant un foil. Puis, il y a eu une deuxième génération de foils, mais les compétitions ont manqué et celles qui ont eu lieu n’ont pas été concluantes. Le premier à voler vraiment, Charal, nous a fait une belle démonstration. Oui, il vole ! et c’est bien parti pour qu’ils volent tous.

©François Chevalier - APIVIA Lines
Apivia, plan de formes
Une coque étroite avec un bau maximum reculé jusqu’au tableau arrière, une carène ronde, douce, entourée d’un redan pour assuré un près, le résultat de la collaboration de l’architecte et du skipper ne manque pas d’originalité. 

Que ce soit par manque de vent ou à cause de l’état de la mer, l’IMOCA retournera à un moment donné dans son élément. Et bien plus encore, la règle des 60’Open prévoit deux safrans, mais leur définition interdit tout winglet ou plan porteur, et il n’est pas question de leur donner la moindre courbe. “L’ensemble des points des bords d’attaque et de fuite doivent être dans le même plan“.  Dommage, une courbure aurait bien arrangé les architectes qui planchent sur ces voiliers à qui il manque une pate. Par contre aucune limitation dans la jauge sur la forme des foils, qui pourraient prendre la forme des petits avions que l’on voit sous les planches à voile, car le skipper vole avec un équilibre bien précaire, et son bateau se cabre pour trouver un point d’appui sur l’arrière de la coque entre deux vols.

Il est de plus en plus difficile de reconstruire un plan de forme d’après des photos, les appareils semblent prendre un malin plaisir à déformer les images, et créer des points de fuites aléatoires, qui se baladent suivant des courbes évolutives. Le meilleur moment pour lire les lignes de ces bateaux, c’est pendant la séance de teste de retournement, et je n’ai pas eu l’occasion de m‘y rendre pour les 6 derniers Imoca mis à l’eau.  

©François Chevalier

Pour simplifier l’étude de l’évolution des formes de ces 60’, j’ai retenu deux voiliers sortis de chantier au mois d’aout, Hugo Boss et Apivia. Plusieurs raisons à ce choix, le voilier d’Alex Thomson, un plan VPLP, présente des options radicales et originales, et Apivia est le premier plan récent de Guillaume Verdier. Le fait que les précédents vainqueurs étaient signés VPLP / Guillaume Verdier me semblait une raison de plus pour analyser qu’elle est la part de chacun de ces architectes dans la réussite des deux premières places depuis 2012, ou du moins quelles options architecturales résultaient de leur mise en concurrence.

©François Chevalier - Lines HUGO BOSS
Hugo Boss, plan de formes
Alex Thompson aime les coques taillées au couteau et les options franches, son voilier glisse sur une planche, qu’il soit à plat ou à la gîte. Les embruns et les paquets de mer risquaient de remplir le cockpit, il est supprimé !

Bien évidemment, la part des préférences du skipper de chaque voilier dans les choix généraux entre en ligne de compte. Charlie Dalin a une formation d’architecte naval et a suivi la conception d’Apivia de Guillaume Verdier dans ses moindres détails, il affirme d’ailleurs, “J’ai été au cœur de tous les choix“.

De son côté, avec l’expérience qu’il possède des plans sur lesquels il a navigué, aussi variés que Marc Lombard, Juan Kouyoumdjian, Finot-Conq, Farr Yacht Design, et le duo VPLP / Guillaume Verdier, Alex Thompson a eu le temps de se faire une idée du voilier qui lui permettrait de remporter enfin un Vendée Globe.  Son choix du cabinet VPLP, qui venait de concevoir le premier IMOCA de la nouvelle génération pour Charal,  semble la suite logique de sa démarche pour obtenir un voilier le plus planant possible, avec une réserve de puissance en cas de bris de foils. Sa dernière expérience, où il menait un train d’enfer jusqu’à ce qu’un de ses foils rencontre un objet flottant, lui a donné envie de se protéger d’une option trop radicale. En effet, il avait misé sur ses foils pour obtenir de la raideur, en choisissant un voilier plus étroit, avec moins de traînée. Aussi, le cabinet VPLP lui a conçu un voilier puissant, pas trop large, un fond plat qui s’évase en plans parallèles à la surface de l’eau à la gîte. et un bouchain qui part de l’étrave juste au-dessus de l’eau et remonte haut sur le tableau arrière. On retrouve ces formes évasées sur le tableau arrière des dernières générations de TP52, ces monocoques de régate ultra sophistiqués, un peu plus lourd par rapport aux IMOCA, déplaçant 7,5 tonnes pour 15,85 mètres de long. Ces plans évasés permettent au voilier à la gîte de partir rapidement au planning. Fidèle à son image de pourfendeur d’idée reçues, Alex est allé encore plus loin en affinant le pont avant, en créant un pan coupé encore plus important que sur le précédent Hugo Boss. Si le fond de l’étrave est le plus plat et le plus large possible, à la limite de la largueur autorisée par la jauge, le fond remonte vers le bouchain suivant le même plan incliné qu’à l’arrière. Comme Alex les aiment, les formes sont coupées au couteau, le voilier devant voler ou planer ! Le roof a retenu toute l’attention des personnes présentent à la première sortie de chantier du voilier et n’a pas manqué de surprendre par sa longueur, sa forme originale et sa couleur. En fait, il n’y a pas de cockpit, Alex manœuvre de l’intérieur. Toutes les manœuvres courantes débouchent au centre et se répartissent sur quatre winches commandés par une colonne au centre, Au-dessus des winches, les écrans affichent les données et surveillent  l’extérieur par des caméras à 360°. Une barre franche permet de barrer sans sortir. Le rouf se prolonge jusqu’au rail d’écoute de grand-voile et les paquets de mer plongent sur l’arrière sans remplir le plancher, réduit à l’accès au roof. Sachant que la génération précédente de 60’ pouvait embarquer plus de cinq cents litre d’eau de mer dans leur cockpit, Alex a préféré concevoir un habitacle clos pour les manœuvres et laisser l’eau et les embruns lui passer au-dessus et supprimer les obstacles pour qu’ils n’aient pas la possibilité de plomber l’équilibre du voilier.

©François Chevalier

À 20° de gîte, Hugo Boss glisse sur un fond plat, alors qu’Aviva a une surface mouillée réduite et un redan pour s’appuyer.

On aurait pu croire que les formes des nouveaux IMOCA sortis de chez VPLP et Guillaume Verdier seraient au moins de la même famille. Or, il n’en ai rien. Il semble même qu’il n’y ai jamais eu autant de différence entre deux IMOCA sortis le même mois. Guillaume a travaillé sur la diminution de surface mouillée, une carène qui accroche sur un rail sur toute la longueur du voilier, sur l’écoulement des paquets de mer et des embruns, sur le centre de gravité de la coque et du gréement. Il a soigné particulièrement la carène pour le petit temps et toutes les phases de transition. 

©François Chevalier
L’axe de la flottaison à la gîte est moins important, et la flottaison beaucoup plus étroite sur Aviva

Le résultat est une coque étroite, à peine 5,35 mètres, dont le bau maximum est au tableau arrière, à partir d’un bouchain juste au-dessus de la flottaison, une galette creuse, légèrement pincée sur l’avant, entourée d’un redan très marqué. Le centre de gravité est très sur l’arrière, encore plus que sur le plan VPLP. Si le bau du milieu est bien défendu et présente un franc bord important, avec un bouchain arrondi et des formes douces, le pont est en gouttière à partir de l’avant, jusqu’à atteindre quarante centimètres de profondeur au niveau du mât. Résultat, le centre de gravité du gréement est descendu d’autant.  Seul point commun entre Hugo Boss et Apivia, les fonds sur l’arrière présentent un léger point d’inflexion pour “rocker“, initié par Juan Kouyoumdjian sur le Cheminée Poujoulat de Bernard Stam.

Sur les deux voiliers, le choix des foils est tout aussi différent que les formes de carènes. 

©François Chevalier
La jauge interdisant un foil sur les safran, l’équilibre doit se faire entre le foil et la quille, qui sont très proches, le voilier a tendance à retomber sur son arrière. 
On pourrait imaginer un foil de stabilisation sur les foils, en forme de petit avion, comme sur les kites surf et planches à voile.

Hugo Boss est équipé de foils en forme de grands demi-cercles, alors qu’Aviva s’appuie sur un foil en U très large, le creux du U étant parallèle à l’eau à la gîte, ce qui lui donne plus de raideur. En vol, lorsque les voiliers reprennent appuis sur leur arrière, Aviva se pose sur son becquet, alors que Hugo Boss tombe sur l’aplat de son flan. 

©François Chevalier
Les attentes des architectes sont claires, devant l’instabilité du vol des IMOCA, il est temps de modifier la jauge et de permettre d’avoir des ailettes sur les safrans, ou du moins, comme ici, qu’ils puisent présenter une courbure.

Malgré la frustration des architectes, cette classe, qui est la plus libre de toutes, est en pleine croissance et son avenir bien assuré si elle sait s’adapter aux nouveaux défis. Deux points particuliers qui pourraient relancer les recherches architecturales, celui qui bloque la largeur de l’étrave, celui qui empêche les safrans de stabiliser le vol et celui qui empêche les points d’inflexion sur les sections de la carène…