Advancing in speed sailing
We were talking about getting the very best from sailing equipment, and how often the best is not the obvious. There is a famous photo from 20 years plus ago of Fred Hayward breaking the world speed record (then around 35 knots) on a windsurfer with his battens forming an S shape, so the sail was far from the perfect foil that all had thought was essential until that time. In fact many people still believe that foils are the ideal shape, which is ironic when we look at the massive contortions that the current America’s cup wings are producing. These wings have sensors in them, which tell the trimmer the optimum trim via flow devices on each wing section, so the fully knocked appearance in some instances with the most unfoil like appearance is generated by computer, not feel.
The evolution of speed, the theories and the practice all give somewhat conflicting evidence on the matter of what is fast. The old theory that waterline length produces speed (even upwind) is blown apart by windsurfers, foils, kites and other new evidence. Probably one of the most radical looks at sailboat design is the Vesta’s Sail rocket (the latest eccentric looking craft to hold the world speed record) which had a relatively small sail area, cranked to windward, and a huge leverage between the pontoon that the sail was mounted on and the pod the driver rode in. The innovation to overcome the deficiencies of traditional boat and catamaran design were a massive departure from conventional wisdom, yet worked because it was technically very sound.
If we diverge for a moment, one of the challenges of sailing is that when a boat heels, or is even sailed flat, a small proportion of the driving force from the sail is downwards – in other words the drive from the sail sinks the hull and causes more hydrodynamic drag. Kite boarding have the opposite problem – they create lift into the air, which may be controlled IF the kite can be flown low (not overpowered). However, the kite board cannot be controlled for power like a sail, so the angle of flying will dictate the lift, and therefore the ability to go upwind fast, and downwind efficiently. The advantage of the kite board is that it lifts, reducing hydrodynamic drag. The disadvantage is that it cannot be depowered at the optimum angle – it is depowered by bringing it away from the optimum driving angle. This is an important feature of sails – they are controllable.
Getting back to Vesta’s Sail-rocket: The oddly cranked to windward rig produces hull lift, but is controlled by the pilot who can sheet in and adjust the wing. The driver pod achieves leverage beyond normal proportional to the side of the craft. There is little doubt that balance was not perfectly achieved, as the craft went down the speed course crabbing, but the foils (float types)appeared to look after the hull angle change. If we talk about efficiency, the Vesta’s Sail-rocket clearly broke boundaries. It also broke the worlds speed record by ten plus knots – an extraordinary achievement by any standards. Then we look at airflow and hydrodynamics, and begin to realize the potential of this innovative design. To sheet the wing to optimum was a really difficult task, as airflow was nothing like a conventional vertically mounted sail. To steer the craft whilst traveling partly sideways must have been a special skill. We would love the Vesta’s Sail-rocket team to produce some documentation giving their “secrets” away – this innovation always trickles down to racing through brilliant designers.
Why do Toplevel Sailing have such interest in these special projects? The answer is that although we work with largely production and one design sailing equipment, our rudimentary understanding of the latest developments and theories can only add to our ability to understand speed from sailing craft, and how to apply this within all sailing classes. A mere understanding of these machines can open doors that the less informed can only access with the masses, so reading extensively about the theories behind the designs may open a door early for us, that others wait for. Toplevel Sailing seek to stay ahead in all disciplines of sailing.