EXTRAORDINARY BOATS

MARK CHISNELL ON THE F50

The F50 is the new one-design foiling 50ft catamaran used for the Sailgp circuit, and is adapted from the AC50 used in the last America’s Cup

Ithink 99% of people believe that we received these boats from Bermuda, repainted them and sent them on their way again. I don’t think we’re ever going to be able to explain quite what we’ve done, but the amount of work that has happened here in

New Zealand has been simply phenomenal,” explains Brad Marsh, technical team operations manager for Sailgp.

“The only thing that resembles the previous boats is the length and width; they have been modified in every respect.”

Marsh is talking about the F50, the boat developed for the Sailgp circuit. The basic

plan was simple enough: to take the AC50S that raced in the America’s Cup in Bermuda in 2017 and use them to jump-start a one-design fleet for the new professional circuit. The AC50 would transform into a strict one-design F50 with standardised components.

The fundamentals of the boat didn’t change: it is still a 50ft foiling catamaran with a hard wingsail. The F50 foils using rudders with elevators, and two L-shaped daggerboards.

The crew control the angle of attack of both to achieve flat, fast and stable flight.

But almost everything was built new, from the daggerboards and rudder through the control systems and hydraulics to the headsails, as well as two new hull platforms.

“We have been going since November

2017, when they started laminating the daggerboards,” recalls Marsh, who has been overseeing the work at Core Builders Composites at Warkworth, north of Auckland.

“In April 2018 we received our first containers with the boats from Bermuda. In October 2018 we sailed the first boat, and in February 2019 we sail our first regatta. I think it’s been about 135,000 man hours.”

It’s an immense amount of work, a lot of which is not immediately visible – like the adaptations that mean the boats can now disassemble for shipping.

“It’s the closest thing that sailing has to Formula 1 now. We are a travelling circus going to international venues. We’ve had to take boats that weren’t intended to be dismantled at all, and turn them into something that could go on this travelling roadshow. Every component has to be stored in a container and assembled and disassembled quickly so we can get as much time on the water as possible.

“We know when we go to an event the

intention is to have two days of practice and two days of racing, so there’s no point in having two weeks of assembly for four days of sailing. So we’ve had to be very clever about how the systems and boat work so that it can be assembled quickly, sailed reliably, packed up quickly and transported safely around the world in containers.

“We have 66 40ft containers that have all been custom built. The wing goes in one container, the hull or platform breaks down and goes into two containers, plus the boards and rudders. It’s about having a system and set-up so you don’t lose all the pieces and you’re not running around looking for bits.”

Battery power

There have been philosophical changes as well as practical ones – one of which is very visible. There is just one grinding pedestal, compared to the two on which the Cup crews laboured so much blood, sweat and tears. The foil rake, rudder pitch, cant, wing twist and jib sheet is now driven by lithium ion batteries, leaving just the wing sheet adjustment needing the manpower of two grinders.

“The boats have moved away from the physical, grinding aspect, to focus more on the technical side of the sailing challenge,” said Marsh. “Using the batteries means we don’t need a sixth sailor as grinder, but we have changed the roles around.

“So we have one person, the flight controller, whose job is specifically to fly the boat. In the past that was done by the helmsman: now we’ve split that role off so it can be focussed on.”

During the last America’s Cup, the crews were restricted by the power available from the grinders. “They had to limit their tacks and gybes, but it also meant they had to limit how much they moved the daggerboards and rudders. Now we have unlimited battery power, the teams are able to move all the components as much as they like.

“The introduction of the flight controller means that one person is there with his or her joystick and they are constantly moving the daggerboard in an effort to keep the boat level and in constant flight.” The extra workload on the hydraulic system meant that it needed a complete redesign and rebuild.

Sailgp took delivery of four of the six boats that competed in Bermuda, and the F50’s development team – led by technical director Mike Drummond – was able to

go over all of them and select the best ideas from each for the new fleet. The details of the different control systems and hydraulics used on each AC50 had been tightly guarded secrets during the Cup.

“It was extremely interesting for us. We had the opportunity to take four different boats from the America’s Cup and bring them back into one shed, pull everything out and see what the different teams did. Then we had to go through and standardise these things, so that each boat is identical,” said Marsh.

The one thing that didn’t change significantly was the wingsails, at least not yet.

“The wings are still about 85% as they were in Bermuda. By the time we had rebuilt all the boats, built 28 daggerboards and 28 rudders, stripped, reconfigured, rebuilt and repainted the boats, we didn’t have time to do the wings as well.

“We have now started a project to build eight new wings for the 2020 season. They are going to be a modular wing, which will allow us to assess the conditions and set up for each regatta. They could be set to be 4m taller than the current wing, the same size, or 4m shorter than the current wing,” explained Marsh.

“The idea is to be able to have the boats foil in very light winds, and still sail in very heavy winds. This opens up different venues to us.”

The boats will constantly develop to keep them at the bleeding edge of what’s possible, while remaining one-design.

Nothing like this has ever been done before – the nearest is probably the developments the VO65 went through between the last two Volvo Ocean Races. Those boats generated some of the most exciting offshore racing ever seen.

It will be interesting to see if the same philosophy can deliver that result for highspeed, short-course inshore racing long-term. The America’s Cup community will be watching with interest.

The Sailgp Australia and GBR teams testing and practising in Sydney Harbour

The F50 daggerboards use a higher modulus carbon fibre than the previous generation foils, allowing for thinner sections that delay the onset of cavitation. “Each team receives two sets of daggerboards. One set is ‘LAB’ or light air boards, the other set are ‘HSB’, or high speed boards,” explains Brad Marsh, Sailgp technical team operations manager. “The intention is to choose the boards for the regatta so we are not changing them overnight, although we do have that ability.” In the centre of each steering wheel dials control the rake of the rudders, the differential between the pitch of the rudder elevators, and the rate at which the daggerboard rake and rudder pitch change. Twist grips on the rims control the leeward daggerboard rake.

The pilot’s flight control panel and joystick. These two devices give full control of the modes and motion of the rudders and boards. To the left-hand side of the cockpit the wing trimmer also has foot pedals, button controls and a screen, with controls for wing twist, inversion and camber.

The horizontal component of the rudder, the elevators, can be changed with light and heavy air components. The rudder differential – the difference in angle of attack between the windward and leeward rudder – has also increased, from 3° to 6°.

Adding batteries resulted in a redesign and rebuild of the entire hydraulic system. The system now demands over five times as much oil as when the hydraulics were grinder-powered.

The lithium ion batteries which have replaced the manual grinder-produced power are housed in a central pod.

A headsail lock on the forestay gives crews the ability to change sails very quickly. Teams now have a choice of three headsail sizes, which they can select on the day.

The boats have been redesigned for quick assembly and disassembly at each venue.