The teams and the America’s Cup Class Measurers received an unpleasant surprise when they started measuring the boats at the beginning of the measurement control period for the Malmö-Skåne Louis Vuitton Acts – many of the boats were too heavy.
It’s not uncommon for America’s Cup boats to be right at the extreme end of the maximum allowable weight. After all, more weight in the keel bulb increases stability and speed. It’s one of the easiest ways to make the boat go faster. But the maximum allowable weight is a hard limit; if you’re too heavy, you have to take weight out.
Ken McAlpine, the Chief Measurer for the 32nd America’s Cup explains what happened.
"Basically, the force of gravity is slightly stronger here than it is in Valencia," McAlpine said. "We learned this when one of the boats came in heavy. The team couldn’t understand it because they insisted they had changed nothing to the boat since Valencia. I wasn’t very happy, because I had to tell them to take 50 kilograms out. That’s a hard job for the shore crew, and the team was sure they hadn’t done anything to the boat that would warrant that."
Discussing it amongst his measurement committee, Guy Roland Perrin suggested that maybe there was a gravitational issue at work. The Measurers decided to do two things. They asked some technical people on the teams to search the internet for information that might explain how the force of gravity could differ from the more southern latitude of Valencia, compared to Malmö. McAlpine’s team also decided to weigh two other boats first thing in the morning, to see if the problem persisted across different teams.
Sure enough both other boats weighed in heavy, by about the same amount. Then, the internet search revealed a complex mathematical formula that suggested the boats should weigh about 50-kilograms too much. That’s the number McAlpine was seeing.
"Basically, the force of gravity changes with latitude, and the further north you go, the stronger it gets. It’s a very subtle change, but when you’re dealing with such a heavy object, even a small change makes a difference."
The solution Applying a calibration factor to the scale was the best way to move forward. "All the other equipment we use, we calibrate ourselves. So it wouldn’t be unreasonable to do that with the scale. We’ve decided to apply a calibration factor to the scale, and that brings the boats into line."
So what happens when the show moves to Trapani, or back to Valencia? "Had we asked them to take out 50 kilograms here, when we move to Trapani everyone would have to put it back in. What has effectively happened is that in Valencia, the boats have been showing as fractionally underweight as the scale is calibrated in the UK. But then coming this far north, it’s like a double whammy. The weight of the boats was maximised for Spain, and it makes them read over the limit in Sweden. But we’ll be weighing everyone again in Trapani."
For McAlpine, despite a couple of sleepless nights, it’s been an interesting experience. "It shows the quality of the people on the teams that when I went back to that first team and told them they could put the weight back in, they just got on with it and did it. We’re fortunate to have a good working relationship with the teams on issues like this, and it’s always interesting when we work through problems together."
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