Technology
Updating the boats for a wider range of conditions and building new wing rigs for the SailGP fleet of F50 foiling cats is not only about making them super-fast and super-reliable... it is also about making sure all boats in the fleet are precisely as fast as each other
As the SailGP circuit moves into its second year, a great deal of refinement and development has been poured into every aspect of the complex operation – not least on the boats themselves, which will be fitted with a new set of wings for 2020, made by Core Builders Composites (CBC) in New Zealand, which handles all of the manufacturing for SailGP. When the SailGP project took flight with its inaugural event at Sydney in January last year, the first priority was to standardise the hull platforms and foils, but there was no time to build a new set of wings.
‘The whole concept is for all the equipment to be strictly one-design, but, while the America’s Cup wings were very similar in profile, they all had quite different control systems,’ says Mark Turner, the managing director of CBC. ‘The next phase was obviously to fully standardise the wings across the fleet, which provided an opportunity to take a clean-sheet approach and come up with a new solution that is tailored to the particular demands of SailGP.’ This has involved a total redesign with two primary but related objectives: to extend the range of wind conditions in which the boats can continue racing and also to improve the control systems, in terms of the speed, accuracy and range of shape adjustment that can be achieved.
In what is essentially a tightly run and sophisticated entertainment package, SailGP operates within a
70 SEAHORSE
No bigger ask
brutal set of constraints dictated by broadcasting schedules and spectators paying for stadium tickets to watch an open-air, weather- dependent sporting contest. When the curtain goes up at the advertised time on the allocated weekend, the show must go on.
Confirming the age-old adage that when “man plans, God laughs”, the first year saw racing curtailed on a number of occasions due to too much or too little wind.
Under the direction of SailGP’s design director, Mike Drummond, a team of designers and engineers spanning multiple disciplines set about tilting the odds more in favour of man’s plans. The result is a modular structure with elements that can be added or removed to provide three configurations: a standard 24m wing, a heavy weather 18m wing and a light-air 29m version.
The profile shape is determined by the top and bottom sections, while the height is determined by the middle section(s). Directly joining the top and bottom sections creates the 18m wing. Two different height mid- sections can be deployed, either creating the 24m or 29m rig. Because the top and bottom sections are always used, the main standing rigging components attach to them with the shroud lengths adjusted accordingly.
‘Solving the heavy wind part of the problem was fairly straightforward from a design point of view,’ says Drummond. ‘Just make the rig short
Above: the SailGP boats hit the water with new fully standardised wing sails and identical sail control systems to ensure even closer racing and a totally level playing field for the teams. The new rigs allow three different sail area options to enable the boats to race effectively across a wider range of wind
conditions. With the 29m tall light airs rig deployed, good racing should now be possible in just 4kts of breeze
enough and the limitations become sea state and foil control and cavitation. My expectation is that the boats could be sailed in more than 30 knots with the short wing. ‘Light winds pose a much harder technical problem because the force available is related to windspeed squared, so between six knots and four knots of windspeed, there is a 60 per cent drop-off in force to get moving. Other factors working against good light wind performance are that lift-induced drag from the rig increases at higher lift coefficients and a larger wing is heavier.’ Drawing some inspiration from racing One-Metre radio-controlled yachts, which utilise three rigs and can race effectively in a 3-30 kt wind range, Drummond says by gaining more area, reducing lift-induced drag and increasing heeling leverage, the 29m rig should enable good racing in as little as 4kts of breeze. In plan form, the wings look very similar to the America’s Cup versions. Developed by Tom Speer, the wing sections are slightly thicker, first to improve the lift coefficient in light air and second to improve buckling stability when the 29m version is deployed.
‘The new wing is derivative only because the original wings were very well designed,’ says Drummond. The constraints in the redesign were only the need to fit with existing boats, righting moment and balance, although reducing building time, material wastage and spare parts
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