Andi Robertson takes a detailed look at the new Mini 6.50 design hoping to win this year's Mini Transat.
Looking at the armoury of innovations incorporated in the Arkema 3 Mini it appears to be an all-out effort to blast every other Mini out of the water, pushing new performance frontiers for the offshore class, which has always been a development hotbed.
But there is much, much more to this project than winning a Mini 6.50 arms race. Arkema 3 is a design and technology testbed for a whole raft of new ideas.
Top of the list for innovation in the boatbuilding industry, which needs to do much more to clean up its manufacturing technologies, is the use of a range of new resins and glues manufactured by the global chemicals giant Arkema. The hull and deck of the boat were made from Arkema’s thermoplastic composite Elium, a liquid acrylic resin that is completely recyclable.
The €7.5 billion turnover Arkema group has a successful history of innovation in ocean racing through entrepreneurial French skipper Lalou Roucayrol. The successful Team Lalou Multi50 spawned a Mini Transat programme, which since 2011 has brought on young French skipper Quentin Vlamynck.
Designer Romaric Neyhousser is the very smart but practical thinker behind of much the foils work by Guillaume Verdier’s design and engineering group for the VPLP-Verdier IMOCAs. He also collaborates with Verdier on Team New Zealand’s America’s Cup cat.
The Arkema 3 Mini started with a blank sheet of paper in 2015. A menu of ideas was picked over, including canting rigs, canting and extending keel, mast rake modification systems, a system to control the orientation of the keel in 3D, the wingsail, and foils.
Neyhousser says the now popular scow Mini hull shape was a personal passion of his for some 20 years. Then from the shortlist it was decided the new Mini’s canting and extending keel would incorporate a device to set the tilt angle. It is believed to be the only 6.50, so far, using this concept.
A change to the Mini class rule opened the door for foils. The rule now states that ‘appendages can increase the beam defined in J-3 (3m) once the start has been taken’. The draught can also be increased after the start beyond the 2m limit.
Take a look back at 2015 Mini Transat: Eight Cube, or the Flying Frog, this eccentric new Mini Transat boat has foils.
The two-element wingsail is the boat’s biggest and boldest step. The Mini class allows only polyester mainsails and so constructing a shape which holds its design shape and rigidity was a challenge.
Neyhousser worked with La Rochelle’s Incidences Voiles. Ease of use, reduced loads and improved efficiency came ahead of speed potential.
In particular they sought improved handling and loads during the acceleration phase. The result is inspired by C-Class rigs but it is not as rigid.In effect it comprises two wings, each with symmetrical panels over a carbon framework.
The rig design is a continually evolving process, not least because there are neither load cells nor data analysis of the sort used extensively by the America’s Cup wingsail designers. Instead the initial design analysis included building a one-fifth scale model and literally feeling the loads.
The real gain with a wing is the ability to develop a really clean, aerodynamic leading edge and that is a work in progress on Arkema. “It is difficult to have a nice leading edge, only through the action of luff tension. It is too thin and not round enough. So it is very important that we improve here,” Neyhousser notes.
“The gains we are sure we have is the sheer usability factor. The tensions and loads are low. In strong winds with the foil set up it is important to be able to react with the sail when the acceleration is so quick, from 15 to more than 20 knots in a few seconds. Compared with the classical mainsail that is very good.”
Neyhousser’s priority was to design a boat that had good all-round capabilities across the wind range and was not too extreme. Safety and the ability to sail at high average speeds with ease were the watchwords, rather than pushing for a completely foiling design.
However, having designed and built Arkema 3, Neyhousser now believes full foiling is possible. “We could have designed a boat which would fly most of the time, but I was not convinced at the time,” he explains.
“We wanted to be prudent and the goal was to have a boat which typically foiled at 18-20 knots boat speed, at the highest end of the speed range.”
The boat came out around 150-200kg heavier than expected but still flies in 15-17 knots of wind at 18 knots. The top speed so far in flat water is 24 knots.
The designer says, smiling: “In 20 knots of wind you are sailing at 20 knots of boat speed, maybe a little more.’
Arkema 3 has relatively small foils, which work in different modes. The foils set on a canting axis similar to normal keel systems, with a 30° range.
When the shaft is set more vertically for slow speeds and upwind it acts more like a daggerboard; when it is canted up it acts more like an IMOCA-style foil creating lift and increasing the righting moment. The rake of the foils are also adjustable.
The scow hull shape also increases lift and stability, so why have both? Neyhousser says the wider scow bow allows them to better manage the angle of attack of the keel and the foils, giving a more direct flow onto the foils.
He adds: “This is not an extreme hull, it does not reach the max beam that I could have gone for. The aim here is to reduce the wetted surface at certain heeling angles. The foil generates a lot of dynamic stability, which compensates for the reduced beam.”
Close-up images of Arkema 3
Arkema 3 is a dynamic, exciting programme that will continue to test the full team in order to be optimised for the Mini Transat, which starts 1 October 2017. The boat does not yet have all her sails – least of all an overlapping Code 0 – and learning how best to use all the buttons will be a work in progress.
Arkema 3 specification
Length (waterline): 6.5m (21ft 4in)
Beam: 3m (9ft 10in)
Draught: 2m (6ft 5in)
Disp (lightship): 800kg (1,763lb)
Sail area (downwind): 107sq m (1,151sq m)
The hull is infusion moulded from a recyclable thermoplastic and carbon fibre composite. The windows are made of an elastomer called Altuglas ShieldUp which weighs half that of conventional glass. Bostik glues are used in the build.