The science of speed

Brent Vaughan | VOLUME 28, ISSUE 2

The innovative Vestas Sailrocket 2 has smashed the world speed sailing record, forever changing our notion of waterborne velocity.

If you’ve ever experienced a sailing boat that sails faster than the speed of the wind, then you know of the exhilaration of harnessing this force of nature – and overpowering it. With modern sailing boat designs, sailing faster than the wind is no longer the stuff of legend; it’s common practice, with racing catamarans, such as the monster hydrofoiling AC72s set to contest this year’s America’s Cup. However, despite sailing at speeds in excess of 40 knots (74.1km/h) at times, those boats are positively sluggish when compared to Paul Larsen’s speed machine, Vestas Sailrocket 2.

RECORD RUN

After 10 years of persistence, design innovation and an unbridled ambition to be the fastest sailor in the world, the work of Larsen, an Australian, and his dedicated team finally paid off, when Vestas Sailrocket 2 (VSR2) smashed the world sailing speed record over 500m by more than 5 knots (9.3km/h). At the ‘Speed Spot’ at Walvis Bay, Namibia, VSR2 soared into sailing history last November by averaging 65.45 knots (121.1km/h) over half a kilometre. Since ratified as the outright sailing speed world record, during the run the boat hit a peak speed of just under 68 knots (125.9km/h).

To put this achievement into perspective, you may remember fellow Aussies Simon McKeon and Tim Daddo, whose efforts aboard their own cutting-edgecraft, Macquarie Innovation, setanew world record mark of 50.27 knots (93.1km/h) in 2009 at Wilsons Promontory in Victoria. Larson’s new benchmark has upped the ante by close to 30 per cent – a virtually unheard margin in world record terms.

The latest Aussie-driven effort uses a fundamental concept first dreamt up some 50 years earlier by Bernard Smith in his book, The 40-knot Sailboat. Talk about being ahead of his time – a rough diagram of what could pass for VSR2 is sketched on the front page of Smith’s 1963 hardcover! If only Smith knew the true potential of his work – perhaps he may have given it an even more ambitious title …

LIFELONG PASSION

Larsen’s interest in experimental boat design began early, but when he stumbled across the theory in The 40-knot Sailboat, history was already on its way to being re-written. “The passion started when I played on a dam on the 30-acre farm we had overlooking Healesville in Victoria,” says Larsen.

“I was about 11 or 12. I had never sailed a proper boat before, but I started playing with small wooden model boats. I would play with all shapes and sizes just to see what could go to the other side of the dam the fastest – short monohulls, wide monohulls, proas, catamarans, big rigs, ketches, canted keels and more.

“There were no rules and I hadn’t yet been shown what ‘the norm’ was. Some of the models got quite complex considering I only had basic materials and no remote-control gear. I ended up with wing-sailed, canting-keel monos with selfsteering kit … until I discovered multihulls.

“I developed a solid understanding for what makes boats work – what the compromises of the various options were. The one thing I hadn’t seen or worked out myself was the beautifully simple model from Bernard Smith. It just solved all the big stability problems. When I first read The 40-knot Sailboat while working in a chandlery store just outside Airlie Beach, Queensland, the light went on. I knew the concept was special, and so the course was set for 65 knots.”

WEIRD SCIENCE

The VSR2 is certainly an incredible experiment, using a combination of a hard wing sail for efficiency, stepped floats to reduce drag as the boat’s speed increases, hard and shaped foils to eliminate cavitation and a low-wind-resistant ‘fuselage’ profile – all made from carbon and honeycomb core, with titanium used throughout.

The design principle adopts a theory whereby the forces against the wing sail and the forces against the primary foil cancel each other out. This is at odds with all other sailing craft, whereby they lean over as wind pressure increases. The concept allows the VSR2 to take full advantage of the apparent wind (the wind on the skipper’s face) generated from the boat moving through the true wind (the actual wind on the water) at a faster pace, rather than losing the energy of the wind from the boat leaning over. As the wind increases and the boat moves faster, it generates more wind, taking a fresh 20-knot true wind and multiplying it into a 50-knot-plus apparent-wind gale. The only thing slowing it down is the boat’s drag through the water.

That drag is minimised by using foils and low-drag floats. Interestingly, the ‘fuselage’, as it’s referred to (where Larsen sits), points into the apparent wind – not the direction the boat is actually heading – in another attempt to reduce drag from the wind. This means the sailor feels like he is sailing sideways. As the boat reaches speed, only the main foil, rudder and the stepped section of the forward float will remain in the water – the rest is literally flying above it.

The project hasn’t been without its challenges. On VSR2’s predecessor, Vestas Sailrocket 1, the foils experienced extreme cavitation just as they were hitting higher speeds. The foil, much like an aeroplane wing, relies on the high pressure on one side to lift in the direction of the low pressure on the other. However, when the foil moves at high speeds the pressure can reduce so much that the water boils and turns into vapour. This means the boat starts to slip as it loses its grip in the water, resulting in reduced control and higher drag. This has been overcome by changing the foil design from teardrop profiles to sharp, wedge shaped profiles, in much the same way that high performance powerboat propellers work. A first for sailing, it may well have made all the difference.

IN THE BLOOD

For Larsen, becoming the fastest sailor on earth was no accident. “I was pretty average at most Australian ball sports, but with sailing I knew I had found my ‘thing’,” he says.

“Dad bought a small yellow Hobie 14 and we sailed it on Port Phillip Bay. The Hobie scene was very active back then in the mid-’80s. I hung around on the beach and eventually picked up a few rides,” he adds.

Larsen eventually teamed up with a future Hobie World Champion, Mark Laruffa, who fed his sporting drive.

“Mark was very competitive,” says Larsen. “I loved it; we started cleaning up in everything. We won the Victorian state titles and just about every regatta we entered, including the VYC Oaks regatta. I would spend ages hitch-hiking and riding trains to get from Healesville down to the Bay – sailing was all that mattered. Mark certainly taught me to work hard and expect to win. When the first Hobie worlds came to Australia, I was there. At 15 I was the youngest sailor there and I got to race in some pretty epic conditions against some real legends.”

It was a decade later, after he stumbled across Smith’s book, that Larsen’s life was put on track for extreme speed, when he ended up sailing for Pete Goss’s Team Phillips outfit. The experimental Team Phillips maxi catamaran was entered in an epic round-the-world sailing competition called ‘The Race’, which wasn’t constrained by any design rules – the fastest sailboat wins. Sadly, the Team Phillip’s entry folded up in testing, but Larsen continued on in The Race with Tony Bullimore.

“I had plenty of time to think about what it was I wanted to do with sailing,” says Larsen. “I had an amazing few years literally blasting all over the world in maxi-cats. We set the 24-hour world record on Maiden II (ex Club Med) and then I knew it was time for me to start on my own speed sailing boat. I was already in contact with Malcolm.”

Malcolm Barnsley is a veteran naval architect plus a senior test engineer with Vestas, a world leading provider of wind-powered generators, with more than 47,000 turbines in operation in over 70 countries. When you think about it, it’s an incredible, but somewhat fitting marriage – speed sailing and wind turbines both use technology to extract the maximum amount of energy possible from wind.

WINNING TEAM

“Malcolm had built a 1/5th scale model of Sailrocket 1 and taken it to Pete (Goss) to see if he was interested,” Larsen says. “He left Pete with a video, which he later brought down and showed us. I knew straight away what it was about and what he was trying to achieve.

“I instantly knew he was the right guy to get involved with. We shared a common understanding of what we needed to do and how it needed to be done. It needed to be well engineered. We started with nothing in 2001 … and launched Sailrocket 1 in 2004. Very little money changed hands. We designed it and built it all ourselves in borrowed sheds. Gradually my ‘other’ sailing career faded away as I put everything into my own project. I turned down a few great rides, but that was okay.”

However, innovation often comes at a price, and that is usually learning from failure. When trialing the first prototype, the boat literally took off before back-flipping out of control and crashing back down to earth – and not just once, but on several occasions. This was due to a flaw in the design that caused the nose to lift into the air if a wave was hit at speed.

Despite Walvis Bay being very flat and protected, waves from the Atlantic would occasionally find their way in. Larsen was dragged from the boat unconscious after one such accident, but survived to live another day and build another boat. The second craft, VSR2, has been designed to handle such waves and to date it hasn’t flipped. But it takes nerves of steel to crash and burn, then step up for another round and push the throttle to the floor.

TIME TO FLY

So how does Larsen feel when sailing at 65 knots? “Pumped!” he says. “I’m just looking for the next big surge that will take us to the next level. That last run was awesome; I knew it was really fast. I was mentally working out what the average for the 500m run would be. As I was sailing across the wind at almost 90 degrees, I was bisecting the gusts. The run is usually a series of short surges. That 65-knot run was pretty solid. I knew it put us over 60 knots but averaging over 65 was just something else. That was a huge jump just after we had already made a huge jump. Yeah, that was the ride I’d dreamed of for all those years!”

So with a world record now in the rear-view mirror, what’s next for Larsen and his team? The VSR2 is designed to go three times the speed of wind, but they are now stretching that limit. With peaks of nearly 70 knots (129.6km/h), is a 70-knot-plus speed record possible? Will the kitesurfers make a comeback and catch up? Or will another, even more radical boat steal the title?

The real question, however, is just how fast is fastest? What are the physical limits at which a sailing craft can travel? Once 50 knots (82.6km/h) was thought to be unachievable, but that’s now considered slow compared to the capabilities of the latest crop of speed pioneers.

With so much interest in pushing the speed record, there are bound to be many more challengers harnessing untold innovation. For UKbased Larsen, however, the next big challenge will involve taking speed sailing to the oceans – and possibly an ocean near you. “It would be great to do a project back in Australia,” he says. “We have some big plans, but we need to work through them thoroughly before wheeling them out. I’m pretty keen to get started again.”


Tags
Features
Share
Subscribe
Previous
Next