"Exlex": Small boat from Sven Yrvind with innovative solutions from many years of practical experience
Lasse Johannsen
· 26.10.2025
This must be what it feels like in a coffin. Lying on your back with your eyes closed and your hands on your trouser seams due to lack of space, this place evokes several associations that people find unpleasant. First and foremost, the confined space in this watertight container. It is called "Exlex", a yellow tube that floats on Stockholm's Långholmskanalen and rocks in the slightly moving harbour water in such a way that the cinema of the mind produces a film of the journey to one's own funeral. But it is interrupted. A whirlwind rumbles on deck, Yrvind in Swedish, in this case one with a first name: Sven.
It is a prominent whirlwind - far beyond the borders of the kingdom. Born Sven Lundin in 1939, this extreme sailor has been sailing the seas for over half a century in sailboats so big that you could almost put them on the windowsill in winter. His CV includes various Atlantic crossings with micro-cruisers. Yrvind has held the world record for the Cape Horn rounding in the smallest sailing boat (5.90 metres) since 1976, and his likeness adorns the Museum of Yachting's "Hall of Fame for Singlehanded Sailors" alongside greats such as Joshua Slocum, Bernard Moitessier and Robin Knox-Johnston.
More about Sven Yrvind:
"I want to show that you can sail almost anywhere with this boat," he explains about "Exlex"; "it's more seaworthy than many large yachts." To prove this, he unties the mooring lines and stands at the stern, where an asymmetrical Japanese-style wrigg belt serves as propulsion. Passing under bridges, they head out of the cover onto sailable water, where the two lugsails are set and "Exlex" picks up speed.
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Among the conventional watercraft here in front of Stockholm City Hall, the box-shaped vessel really does look like an experimental object. It is 5.76 metres long, 1.04 metres wide and, when equipped for the journey, should have a draught of 35 centimetres - with the centreboards raised. The hull is made of epoxy sandwich laminate with a four-centimetre-thick Divinycell foam core, which insulates the boat and makes it unsinkable. It is so oversized that it should be able to withstand all storms imaginable in the Southern Ocean.
The underlying philosophy behind the construction is simple and is based on the experience that Sven Yrvind has gained over countless nautical miles in mostly even smaller boats. He is convinced that the only laws to be followed when building an ocean-going yacht are written by nature. Hence the boat's name: "Exlex" is too small for a CE certification according to category A, but has far more important characteristics that are not even mentioned in this regulation - above all, it should be self-righting and absolutely watertight. Yrvind has already tested this in capsize tests. According to the single-handed sailor, contrary to the wording of the recreational craft directive, storms are not an "exceptional situation" on the ocean, but quite normal. A high stability index is of no use if a capsized boat remains keel up.
In his plea in favour of small boats, the inventor sees himself supported by Leonardo da Vinci's square cube rule. This states that the weight of a body increases more than all other factors when it is enlarged to scale; the smaller the boat, the stronger it can be built. Finally, the laws of kinetic energy also speak in favour of his project. Damage in the event of collisions or grounding depends on mass and speed. "If I sail my boat - the way it's built - with a weight of one tonne at three knots against a drifting container, it's no problem."
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Sven Yrvind originally intended to demonstrate his small boat philosophy with an even more extreme project. Together with a few other participants, he wanted to take part in a regatta that would lead non-stop around the world - in boats of a maximum length of ten feet, which corresponds to three metres and five centimetres.
"One day I realised how the project was changing me," says Yrvind, because he began to look for loopholes in the rules in order to extend the specified length of ten feet. "I had accepted a challenge because it gave me problems. Now it became difficult to remain honest with myself when solving it. And so I finally gave up on the whole project."
In search of a new challenge, the Swede returns to his old idea of the low-energy boat. The idea is to achieve hull speed with as little energy input as possible. A long-distance boat can then manage with considerably less sail area.
On paper, Yrvind deals intensively with the topic, with an entire book chapter describing his findings. The chapters deal with bow and stern waves, the resulting movements of the water molecules, the different influence of gravity on this movement in the wave trough and on the mountain. They deal with theoretical and practical experiments, with the help of which Yrvind finally finds out how he can reduce the Froude number - the measure of the ratio of inertial forces to gravitational forces in a hydrodynamic system - in his design.
"There are almost always simple solutions once you have found out what principles underlie a problem," explains Yrvind and that people often overlook such simple solutions because they stick to conventions. "They try to improve existing solutions instead of thinking up new ones." It was only after the attempt to build the three-metre boat for the single-handed non-stop circumnavigation that he was ready for the equally unconventional development of his low-energy boat. Even though this was initially only planned as a daysailer of a good four metres in length - a model. "But the thought quickly occurred to me: If I made it just a little longer and wider, I could really test it on long journeys."
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The wind is moderate when trimming off Stockholm, but the boat gets going well and responds reliably to the rudder. Although the centreboards are not yet on board, Yrvind can even turn up. Secured with a long lifeline, the sprightly senior man manoeuvres safely on the narrow deck and handles the tiny sails. About a third of the space that would be usual for a boat of the same dimensions is supposed to be enough for "Exlex" on her way to the other side of the world. It is divided into two by two square metres of pre-balanced lugger sails, each of which is attached to an unstayed and retractable mast made of carbon fibre tube and can be reefed. These can be operated from below deck via endless sheets from both superstructures. There is one mast foot aft and two forward, one on each side.
As the masts are driven side by side on rough courses and in front of the wind, their entire surface area can be utilised. "This sail plan has no patent jibes and contributes to course stability," assures its inventor. "An automatic steering system is superfluous." The rig, which is only two metres high, is also virtually maintenance-free and so oversized that it cannot break even in the event of capsizing. The two rudders can be adjusted against each other and then act like a drift anchor. They can be operated via ropes below deck from any of the watertight compartments.
Sven Yrvind sailed "Exlex" from Dingle in Ireland to Porto Santo in 2018. Along the way, Yrvind has already designed an improved version.
Technical data "Exlex"
- Design engineer: Sven Yrvind
- Total length: 5,76 m
- Width: 1,04 m
- Depth: 0,35-0,95 m
- Displacement: 0,8 t
- Ballast: 0,2 t
- Mast height: 2,00 m
- sail area: 4,0 m²
Brief portrait of Sven Yrvind
After a childhood on the Gothenburg archipelago island of Brännö, the then 23-year-old Swede Sven Lundin spent a year exploring the Baltic Sea in a converted fishing boat in 1962. In 1968, he sailed the 4.25 metre long "Anna" to England via the Kiel Canal. For his worldwide voyage, he finally converted a twelve-metre steel steamer into a staysail schooner and sailed it all the way to South America, where he ended the venture with the realisation that large boats were not for him.
Back on Brännö, he begins building the moulded "Bris", the size of which is limited by the workshop door and ultimately measures six metres long and 1.72 metres wide. The boat took him across the Atlantic seven times and once again to South America, from where he wanted to sail around Cape Horn to the South Seas. In the end, however, he returned to Sweden and the boat is now in the Museum of Yachting.
In 1976, Lundin, now Yrvind, set course for South America again in a self-built, 5.90 metre-long aluminium boat, the "Bris II". She managed to round Cape Horn in the middle of the southern winter. But even this boat did not continue to the South Seas because it corroded too quickly. Various adventures and small boat projects followed. More information: www.yrvind.com
The portrait was first published in 2018 and has been revised for this online version.
