Making weight

Overall weight, crew weight, sail weights, centres of mass… it does not matter what it is, if it is going sailboat racing, the weight matters. A lot. It is no surprise then to find that the rules controlling the 36^th America’s Cup class, the AC75, have plenty to say about weight. What is different about the AC75 is that the rules impose a maximum weight - a very different concept to the minimum weight that might be more familiar to most sailors.

The weight limit for the AC75 is approximately 6.5 tonnes, that is not including sails or crew. However, over three tonnes of that is supplied by the event organisers; in the foil arms, the foil cant system, media equipment and supplied rigging. That leaves the teams with less than half the weight of the boat that they can control.

“There's no doubt that controlling weight effectively is a critical part of this America's Cup,” said Ben Ainslie, Skipper and Team principal at INEOS TEAM UK. “There's no give or take in the rule, if it's not down to weight, we will have to remove equipment before the race, and that might mean critical performance related gear.”

All the teams will have made someone accountable for monitoring the weight of the boat. At INEOS TEAM UK it is naval architect Alan ‘Booty’ Boot. “His job is to record everything that goes onboard the boat, from the bolts on the instrument displays to the drive train assembly and so on. He's really our weight police,” explained Ben Ainslie.

Being the ‘weight police’ for a boat as complicated as BRITANNIA, however, which is made up of over 17,300 individual parts, is by no means a simple job. It is effectively, as Alan Boot himself explains, one huge puzzle.

“The rule for the weight is split into three areas. Firstly, we have the hull, the appendages, the rig and the mainsail. Then there are the headsails which have their own weight limit and then finally is the crew itself and their equipment. These 75-foot boats are complicated to build and weigh roughly the same as the 52-foot TP-52s, which are considered light for their class. It is all about keeping track of every part that goes on to the boat and making sure it is as light as possible, without it becoming a reliability issue. It is very much a sliding scale.”

In the 36^th America’s Cup, INEOS TEAM UK has built two AC75 boats, both named BRITANNIA. With this being an entirely new class of boat, the learnings from the design and build of the first BRITANNIA were hugely valuable to the entire team, including to Alan from a weight management point of view. The learnings from that process meant that weight management was at the very core of the design process of the second BRITANNIA right from the outset.

“The weight measurement process in the build of our second AC75 started with a meeting with the design team where we reviewed the weights from our first boat, analysed how accurate we were, where we were close to the limit, and then set our weight targets at the very beginning of the concept stage to each department. From then on, the design team, the systems team, and the build team each went away and started to plan out their weights. That information was then fed into a huge spreadsheet and we keep track of every part from there.”

Every single time a part is taken off or added on to BRITANNIA, everything from a piece of hydraulic piping through to any temporary onboard cameras, it is recorded and logged along with its weight. That overall plan enables Alan to keep a very accurate overview of the weight of every single part of BRITANNIA, and feed that back to the relevant teams.

“To make sure we keep to weight in every department it has to be a constant dialogue, it is the only way to do it. We periodically check-in to measure the weights and ensure we are reporting back to the design team and the sailing team where we are at. By doing it on a weekly, or even daily basis, the entire team gets a picture of how the boat is going to form over time.

“It is a real team effort and all about getting the buy-in from everybody across the team. I am delighted to say we have that here. Everyone across the different departments is adamant that we have got to measure everything, weigh everything and make everything as light as possible without causing any reliability issues. It certainly makes my job easier!”.

The boat, however, is not the only element restricted by weight limits under the 36^th America’s Cup rules. The crew, 11 sailors, must weigh in between 960KG – 990KG. Together the crew is also allowed to carry a maximum of 55KG on board, five kilos of weight per person, which includes all the clothing, communications, and safety equipment. As the person in charge of weight across the board, Alan liaises closely with both Head of Human Performance Ben Williams and INEOS TEAM UK Trimmer Nick Hutton, who leads on the sailing team’s equipment, to ensure those elements too are accurately monitored and reported.                   

“Ultimately measuring the crew weight is the responsibility of the official America’s Cup measurer, and our Head of Human Performance Ben Williams will work with the sailors to ensure each and every one of them comes in at the correct weight. My role in that is to liaise with Ben and ensure we are reporting everything correctly.

“Then, on the equipment side I worked closely with Nick Hutton and our suppliers such as Spinlock, who provide our PFDs, Henri-Lloyd, who supply our on-water clothing, and SMITH who provide our helmets, sunglasses, and goggles, to ensure the kit is as light as possible and make sure we are legal from that point of view.

“Within the 5KG per person we have to include everything from wet suits, shoes, life jackets, any of the built-in crash protection, the helmet, spare air, knives, radios, headsets, sunglasses as well as any food and water. That means we have had to work really hard with our suppliers and they have been fantastic in helping us keep the weight down and get within that weight target.”

BRITANNIA was launched in Auckland in October 2020 and has since been put through her paces on the Hauraki Gulf. One of the most visible changes from the team’s first boat was the change in deck layout and grinding positions. It is an area of which Alan is particularly proud from a weight management point of view, and one which resembles the collaborative spirit across the team which, as he says, has made his job just that little bit easier.

“With this boat we had a clear programme of weight management from concept through to design, manufacturing and fit out. The grinding area is one of my favourite parts because it is so well laid out and a great example of that process. Everyone in the team, from the sailing team to the design team to the systems team had an input into that deck layout and, from my perspective, I really like it because you look at that area and you cannot see anywhere where you would save any weight.

“That runs throughout this entire boat, it is super neat, tidy and it is very clear where things go. When everything is so well thought out it helps us push the boundaries and gives people a chance to think about how we can improve things, because we will have a clear idea about where we can lose little bits of weight here and there and free up a bit of a margin to work with.

“Weight management and measurement is certainly important, but it is a part of the giant puzzle that is the America’s Cup rule. Our job is to build a boat to the limits set by the rule and to the limits of our technical capabilities. That includes weight management but also encompasses everything from the geometry of the boat to how the systems work and ultimately how it is sailed. Keeping to weight is simply a cog in the big machine that is an AC75.”