If, like Yann Guichard, you started your sailing in the Optimist, you may remember the rudder and the centreboard. They always seemed to be heavy and cumbersome, especially in the winter chill, yet without them, you could not go where you wanted to. If that was a long time ago for Guichard, the skipper of the Spindrift racing’s team, and if the scale of his new boat is much changed, the appendages are more essential for performance than ever and require as much attention in the effort to handle them. This week in “40 metres solo”, the skipper explains how they work.
The maxi trimaran Spindrift 2 has six ‘appendages’, the generic term that includes the three rudders, the two foils and the centreboard. Designed by hydrodynamic experts and manufactured by specialists in carbon parts, these appendages are in direct contact with the water and undergo serious strain. To reduce their size and optimise their form in order to decrease drag and weight, without any compromise in reliability: that is the equation that the design office of the Spindrift racing must solve.
Rudders and daggerboards, (almost) like on any boat.
The rudders are used to steer the boat. “A sailing trimaran mainly relies on the leeward float. You need a rudder on each side as well as for the central hull,” Guichard explains. “They are interconnected so that movement in one causes a reaction in the other two.”
Positioned around the middle of the central hull, the centreboard weighs between 300 and 400 kilos, the weight of nearly ten Optimists on its own. “This part is to control drift. That’s to say, when it’s in the water it allows us to sail upwind. If it wasn’t there, with some wind in the sails, the trimaran would move forward like a crab. Downwind, it’s up completely, to avoid being slowed down. For the North Atlantic record and especially the Route de Rhum we have a new centreboard, which is optimised, smaller and lighter.”
The turbo chargers on Spindrift 2
The foils are the rocket ‘boosters’ of the modern multihull. With their so-called ‘C’ shape, these crescents of carbon pass through the floats. “From 20 knots on downwind, we put the foil down to accelerate,” Guichard says. “It’s a bit like the effect of the aircraft wing, creating lift, it takes the pressure off the boat, raising it out of the water. It limits the drag as the trimaran picks up speed, exactly like we saw when the America’s Cup AC72 catamarans were flying. Our boat is 23 tonnes and is not quite there yet, but it’s the same principle. You must use the foils at the right time so you don’t generate more drag than lift. It’s about finding the balance.”
Chasing Perfection
A fan of surfing and a tough competitor, the skipper adds finally: “We can gain an extra 3 to 5 knots once we are around 30-32 knots, but the prep work has to be very careful. These parts are in contact with the water at high speed and the smallest holes or defects can cause disruption or even loss of control. The team regularly take the time to polish and make perfect the surfaces of the all the appendages so that they are flawless.”