World class America’s Cup performance often looks effortless; because the boat has been perfectly designed, built and set-up for the conditions.
When a stronger gust of wind hits the wing – as it does all the time – the increased force will inevitably deform the carbon fibre structure. It’s one thing to build the wing strong enough to withstand the extra force. It’s another level to design it and build it to do that with the lightest possible structure; but the clever part, the ultimate level of sophistication is ensuring that the deformation of the wing turns the extra force into acceleration and speed – not drag. The wing’s deformation should put the afterburners on, not the hand brake.
This is where the advanced engineering capabilities of Title and Exclusive Innovation Partner Land Rover have been so useful to the team. If the wing can be designed to deform in a way that automatically turns the extra breeze into extra speed, then the sailors don’t have to expend their precious energy and attention on retrimming the wing – adjusting its shape with human-generated hydraulic power – and instead can focus on their opponent, tactics and strategy.
While the idea is simple enough the execution is much harder, and it has involved a technology in which Land Rover have a world class capability – Fluid-Structure Interaction (FSI), a discipline that studies deformable structures in fluid flows. It’s a mix of two other technologies: Computational Fluid Dynamics (CFD), the study of how fluids flow around structures (wings, tower blocks); and Finite Element Analysis (FEA), the study of how the same structures react to forces (like the wind) in the real world.
Taken separately, CFD examines whether the wing produces lift efficiently. While FEA will look at the structure of the wing and how it deforms as it loads up and produces that lift. The next level is FSI – taking the newly deformed shape of the wing and re-analysing the aerodynamic properties in CFD, then looping back to see how the new shape will distort, and checking how that new shape performs aerodynamically... and so on.
Land Rover use the technology to check how their cars will respond to high motorway speeds or rough roads. At 70mph the designers don’t want the shape of the car to produce vibration or aerodynamic forces that are trying to lift the bonnet, or pull the doors off. The shape of the car needs to be working to help the structural engineers, not force them to add more weight into the structure to combat those loads – that just makes the car heavier and less fuel efficient.
It’s very similar to the needs at Land Rover BAR, and both require a very detailed structural analysis –– the wing designs used in the FSI project for the America’s Cup Class wing include every single rib, there are no approximations here, there’s no guesswork.
“This is complex work in the fine grain of the wing’s performance,” commented Andy Claughton, Chief Technology Officer. “We are even seeing how the Clysar – the film covering the wing – distorts, and how that impacts the speed of the boat. We couldn’t possibly have done this work without Land Rover, their computational sophistication and resource has made a substantial difference to how we have tackled this problem and we will see real gains out on the water next summer as a result.”