“We are designing a boat that is as much an aeroplane as it is a boat,” says Paul Larsen. And, when it comes to airflow and extreme performance, few are as knowledgeable as the holder of the outright world sailing speed record: an eye-popping 65.42kt (121km/h) over 500m.
That his Vestas Sailrocket 2 – which in November 2012 shattered the previous record of 55.65kt, held by a kite surfer – is painted orange like Chuck Yeager’s sound barrier-shattering Bell X-1 is no accident. “A huge amount of inspiration can be drawn from aviation,” says Larsen.
But lest anyone assume that the inspiration is all one-way, Larsen’s latest exploit provides ample evidence to the contrary. When the International C-Class Catamaran Championship (ICCCC) fleet gathered off Falmouth in September for its 2013 race meeting, Larsen was there as a member of Team Invictus, which was founded a decade ago by a couple of Airbus engineers who saw an opportunity to combine their technical skills and passion for sailing in a racing class that capitalises on wing power.
Airbus agreed to support the venture. Team co-founder and stress and fatigue engineer Mark Bishop says the experience has had him and Norman Wijker “on a constant learning curve”. The latest boat, which competed at Falmouth, is the best they have built, he says, in an ongoing quest to slash weight and improve the aerodynamic performance of the solid airfoils that have long since replaced fabric sails on boats of this calibre.
While the boats-to-aeroplanes technology transfer can be difficult to quantify, Bishop says the project has definitely fed knowledge into aircraft projects.
One example has been the team’s exploitation of Airbus’s interest in additive layer manufacturing, otherwise known as 3D printing. In 2010, he says, the team used ALM to make a mast foot. That part was the first major structural member that Airbus made by ALM in titanium, a potentially disruptive technology in which the airframer is investing heavily.
As Bishop puts it, the sailboat racing project encourages such experiments. It is a low-risk environment that allows ideas to be tried out and turned around quickly – and which tolerates failure, unlike an aircraft programme constrained by timetables, cost considerations and certification requirements.
Another example was Team Invictus’s pioneering use of liquid resin infusion to manufacture a composite leading edge for its wing. The result was “quite a heavy part” and could thus be seen as a failure from the perspective of the catamaran project. But, says Bishop, Airbus had not tried the technique before, so when it came to bringing it to an aircraft project the pitfalls had already been revealed.
The 2013 ICCCC boat’s wing also featured a hinge that Bishop is particularly pleased with. As it allows the trailing flap to both pivot and move side-to-side, airflow over the joint was improved regardless of which side of the wing was lift side; rival boats were using a “less tidy” solution, says Bishop.
As sailboats tack but aircraft wings always lift to the same side, it isn’t obvious how or if this mechanism will benefit Airbus directly. But, says Bishop, its design and manufacture has expanded the company’s understanding of ALM. As expected, the technique allowed for rapid prototyping in plastic – which is economical and “keeps the project rolling”.
But when it came to actually making the parts for Team Invictus, Airbus’s own titanium printing machine was unavailable, so they turned for help to GKN. However, machine time was limited to “one box” of parts, so they had to “throw out the rules” and pack them tight, essentially without the stand-off pegs that normally keep them separated. Success points to a more efficient use of printing machines than had previously been thought feasible.
More broadly, Bishop notes that engineers typically work closely within their own skill set once established in their careers. But, he adds, the cross-fertilisation of ideas that naturally goes on within an experimental and time-constrained project such as Invictus is “liberating”.
In the end, the ICCCC 2013 results show Team Invictus in ninth place out of 11 boats. But with two racing days lost to illness and a capsize, the results probably hide a much more encouraging performance on the water, certainly when analysing the time tracker results.
And, adds Bishop, it’s interesting to note that time tracker data shows that the ultimate winner was not the fastest boat – although it may have been the best behaved, most suited to the weather during that one week in September and the best sailed.
Control, as much as raw speed, is ultimately a key to ICCCC success. The Cat-C rules say the boats must, naturally, be catamarans, and no longer than 25ft (7.62m), no wider than 14ft (4.27m) and with no more than 300ft² (27.9m²) of sail area. Bishop believes that even if the catamaran requirement were relaxed, the boat builders would stick with that basic configuration, which is “ideal for course racing”.
Vestas Sailrocket 2, by contrast, is a straight-line machine built for what Larsen calls a “no holds barred” category. But when he gets back on the water, he will be much more concerned about what Bishop calls “sailability”. He is not divulging details, but says plans are moving forward on a boat designed to go after some of the world’s point-to-point sailing records.
Larsen is charged up for the challenge. The legendary “Blue Riband” transatlantic record held at various times by grand liners including Lusitania and United States and currently standing at just 41kt, is ripe for the taking in good weather, he says.
No amount of improvement in sail performance seems likely to herald a return to oceanic passenger travel. But Larsen says wind power today is going through a technology transition akin to aviation’s shift from propellers to jets that may well make it, once again, a viable component of commercial sea transportation.
Thus the obsessive and costly efforts being made to build faster sailboats probably mean much more than just thrills for racers. Sailing, says Larsen, is an area where one can “still make huge gains and cut corners”. His choice of X-1 orange stands as a reminder that the early days of aviation “are a huge inspiration”.
Source: Flight International