When Paul Larsen decided to sail faster than physics would allow, he had only one choice: Reinvent the boat.
Seen from across Walvis Bay, the windswept patch of Atlantic Ocean known as Speed Spot is barely more than a sparkle of whitecaps against a long, low sandbar.
Larsen is originally from Australia, but he searched the world for years to find this spot, a perfect natural runway to test a sailboat so radical that it is more at home in an airplane hangar than in any harbor—a futuristic craft that, if he can make it work, will not only capture the outright world speed-sailing record but also open up a new, no-limit era in sailing. It was 2008 and he was at Speed Spot putting the Mark 1 through its paces when a gust got under the boat and launched it clear into the sky. Larsen is confident enough about the stability of his revised design, the Mark 2, that he included a passenger cockpit behind the driver’s seat. Tilted at a 30-degree angle like the wing, it keeps the boat from flipping (or taking flight).
Positioning the wing and foil away from the hull and on opposite sides prevents the boat from leaning—all power goes into forward motion. Boats rarely move through the water as fast as a spinning propeller, but when they do, they also cavitate. Granted, some powerboats do go faster than 50 knots, but they’re simply sidestepping the cavitation problem. Back at Speed Spot, Larsen has just offered me a chance to ride shotgun on SailRocket’s test run, and I don’t have to be asked twice.
As Larsen mentioned, there is no seat installed in my cockpit (much less a five-point harness), so I’m on my knees, being careful not to touch any of the lines.
Paul Larsen (center) and his team celebrate a successful run at Speed Spot in Walvis Bay, Namibia. While SailRocket is being dragged upwind and into position by the team on the zodiac, Larsen gives me the preflight briefing.
At the end of the 20th century, the world of high-end offshore sailboat racing was an especially dangerous game. The basic design he kept returning to was one proposed 50 years ago by an American rocket engineer named Bernard Smith. In more technical terms, what Smith proposed was a sailboat design that aligned the forces of sail and keel so that they opposed each other more directly.
While crewing on a maxi-cat that managed to set a new 24-hour speed record in the Pacific, Larsen decided that the next step was to form a speed team of his own. The Mark 2 is the first to be kitted out with the radical new foil that Larsen himself helped design to beat cavitation.
Back in SailRocket after our dud start, Larsen looks out at what remains of the watery runway. Despite the fact that his instrument cluster isn’t working, Larsen carves the turn perfectly. I look up just in time to see the photographer on the beach receding far into the distance.
Larson and reserve pilot Helena Darvelid pull SailRocket into Walvis Bay for one more shout at the speed-sailing record. Larsen desperately needs to get his foil unstuck before it’s damaged or, worse, snaps.
Data downloaded from the GPS show that we hit a top speed of 54.4 knots and raced at a sustained average of nearly 50 knots. After three months of trying, he takes the foil, retreats to his home in Weymouth, England, and thinks—for almost a full year. Post-calibration, the foil that Larsen’s A-team comes up with is still a thick V-wedge of carbon fiber, albeit subtly different in its angles and about half the size of the one that got stuck at the 50-knot mark. Almost a year to the day after our harrowing run, Larsen is again floating at Speed Spot, strapped into SailRocket with the wind blowing a steady 30 knots. At 58 knots, the leeward pod under the wing, which is supposed to just skim the water’s surface, is flying 4 or 5 feet in the air.
Back on the beach, after checking the GPS, Larsen writes the digits in the sand, from right to left, in reverse order, in front of the rest of the team. When I traveled to Namibia a year before, I had met a daredevil yachtsman with his eyes on a big prize. As we get closer to what is one of the world’s most perfect speed-sailing areas, I scan the shore. In fact, we are in Namibia, a roughly Texas-sized country at the southwest corner of the African continent. Indeed, if SailRocket were dropped from a great height, it would glide down rather than fall. At the core of the design is a unique trait: Unlike other sailboats, this speedster never leans. Under the right conditions, the brute force method can also get one through the 50-knot barrier. If he’s right, he not only takes the speed record for sailing, he also opens the door to an entirely new class of travel.

SailRocket is probably the only sailboat in the world that comes with a five-point seat belt harness as standard equipment.
In high school in the ’80s he raced the newfangled Hobie Cats and reached the national championships in 1984, followed by the world championship in 1985.
Multihull catamarans and trimarans were pushing out monohulls, carbon-fiber construction was supplanting fiberglass—and the experiments with new designs and materials led to a lot of failures. The sideways lift of the wind on the sail is opposed by the sideways lift of the water pushing on the keel, and the boat is propelled forward. With both an inclined mast and a similarly inclined keel, and neither keel nor sail anywhere near the hull, it looked bizarre. He’s humoring me by trying again, and this time, to our surprise, the launch procedure goes as planned. Viewed in cross section, keels, propeller blades, and even fish usually have an elongated teardrop shape.
His A-team of aerodynamicists who had modeled the forces on the boat and designed his foil were clearly wrong. The wind is whipping the water into such a frenzy that it’s actually swallowing the bottom part of the wing. Most vessels, however, need some sort of keel in the water to stay upright, and sailboats need a keel to move. He’s angled low, hands on a tiny steering wheel nearly between his knees, his helmet just peeking over the edge of the cockpit.
Moving the rudder doesn’t have much effect at low speed, yet to accelerate you need to get the boat pointed in the right direction. But Larsen stumbled across Smith’s book in the back of a dusty yacht chandlery just after high school. But he has gradually attracted enough talent and sponsorship to build two boats based on Bernard Smith’s design. The wing is lifting so hard that the leeward pod is no longer flying a few inches above the water, as it should be, but is gyrating several feet in the air. When that final transition happens, SailRocket will shed the last of its drag and leap into speeds unknown.
As the boat lurches to starboard, the g-forces throw me to port and, fortunately, back into the cockpit.
Looking for a second opinion, Larsen calls on a noted hydrodynamicist who agrees to act as a B-team.
And Larsen returns to Namibia to put the new foil to the test—this time in front of the World Sailing Speed Record Council, the official governing body of speed sailing. There are tiny ones that could slide along in a giant underwater bubble of vaporized seawater like the Russian torpedo does.
We motor our zodiac toward the remote beach until we have to kill the outboard and tilt it up to spare the prop. The dunes march right into the sea, setting up an elemental cycle that repeats itself nearly every day of the antipodal summer. Yet what looks at first glance like a water-striding sailplane is, on closer inspection, pure crazytown. This power play is mated with equally impressive tricks to minimize drag—be it from air, water, or the perplexing cavitation effect.
The name is something of a misnomer, because the barrier can drift slightly higher or lower depending on things like salinity and water temperature.
There’s a classic high school physics experiment where you put a glass of water under a bell jar and then pump out the air.
That keel functions as a hydrofoil, resisting the lateral pressure of the sail and creating forward motion. I’m in a coffin-sized carbon-fiber tube, with control ropes and coaxial cables running through the inside. Eventually Larsen’s motormouth and hail-fellow personality landed him an unpaid gig delivering one of the first maxi catamarans, an 86-foot-long version of a Hobie, to Japan. But the truth is that when things are going well, there’s a lot of free time during a crossing. The keel permits it to run across the wind or even point up close to the wind, so the sail becomes, aerodynamically speaking, a wing. The force of the wind, with a little help from the rudder, slowly brings the nose of the vessel around so that we’re pointing straight toward the beach.
The swoosh of water becomes louder still, like the static between TV channels, volume turned all the way up.
I see the world rotate around me as we burn off speed and then plow, with a carbon-fiber crunch, onto the shoal. But cavitation can’t take hold of this teardrop, because its trailing edge is made of nothing.
The mixture of air, vapor, and very high speed water wrapping itself around a boat at the limit is dynamic and extremely hard to model by computer or even simulate in a high-speed flow tank.

There are ultrathin V’s that can plow a trough in such a way that one whole side of the foil would be dry at 50 knots.
The five of us jump overboard into the waist-deep water, following our guide, Paul Larsen, who is wading toward the shore. Mornings break as clear and sunny as a Baywatch shoot, but in the afternoon, near-gale-force winds descend on the bay. For one thing, its wing is inclined at a 30-degree angle to the water and is nowhere near the fuselage.
It’s a matter of clambering up onto the front float, swinging a leg over the nose cone, and then using both hands to scooch down the fuselage, a couple of inches at a go. He looks out over the nose cone, which is angled slightly down like that of the Concorde jet, the better to keep the boat glued to the water. As I crouch down, I consider what would happen if we ended up in one of the catastrophic crashes that plagued Mark 1. But with a thumbs-up, Larsen signals to the zodiac to let us go, and he starts the launch procedure. Pushed through the water by the sail, the keel also generates lift and thus, in hydrodynamic terms, is also a wing. Draw arrows through their respective centers of lift and they point directly at each other.
And when it occurs it always attacks the trailing edge, because that’s where the pressure is lowest. The seas are parted by the foil’s leading edge and then collapse again into a turbulent mess once it passes. He tweaks the pitch of the foil, the angle of the wing, the ride height of the boat, the vector of the sails. Underlying all their computational fluid-dynamics equations and models were the same handful of scientific papers. When something structural breaks, you can usually feel the boat shudder as the load gives way. The wind howls in our faces, blowing so much sand that it runs down the beach in rivulets, like rain across a windshield.
The desert heat meeting the cool Benguela Current coming up from the Cape of Good Hope creates a powerful natural wind machine.
The physics are similar with cavitation: The pressure drops at the trailing edge of a spinning propeller, and the water around it boils.
Too much sail will overpower and eventually capsize a boat; too little and it will never go anywhere.
And then, suddenly, there are only two rooster tails—the wing has pulled the rear pod completely free of the water. The foil is pulsing rhythmically, blasting spindrift and sea foam into the air like a water cannon on full automatic. With a full foot and a half gone from the business end of the foil, SailRocket looks like an amputee. They maneuver the wing in and out and engage the hinge of the scythe-like foil, lowering it to its proper depth in the water.
The wing is on the port side of the boat (Larsen’s left, my right), and the foil is to starboard.
Hitting the beam to port would obviously break every bone in my body, while the foil on the other side looks like it could slice me in half.
With the acceleration, the leeward float pops out of the water, starts to plane, and pulls the bottom of the wing out of the drink. Cranking the foil up to the surface on its hinge, Larsen sees that the leading edge of his precious foil is pitted and chipped.
Even Larsen can’t believe it, at first mistaking that 500-meter average for the peak speed.
This is the Bonneville Salt Flats of speed sailing!” Larsen shouts, gesturing to the water just off the sandbar. As the boat keeps on accelerating through the 50-knot barrier, Larsen clenches: “Just hold it! The flying sand sticks to our teeth, turning the insides of our mouths to 600-grit with every word. SailRocket’s foil sprouts from the side of its fuselage, then turns to cut 3 feet down into the water.
Critical to any sailboat, a keel keeps a boat from blowing over—or, in this case, from flying away.

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