Technology
He’s back!
But this time Swiss engineer Thomas Jundt decided to go all old-school and squeeze in a hull between the rig and foils...
A no-compromise foiling 35ft yacht intended for European lake racing has driven a multinational group of sailors, designers and builders to the extreme edges of technology in a collaboration that has even stretched to what might be termed “positive deception” to achieve its objectives. Tasked with designing and producing the 14.5m rig, C-Tech’s Tim Willetts says they soon learned that Jundt’s ‘goal was to push us to the point where we were squealing and squirming like stuck pigs’. With discomfort and life in the red zone, however, comes a certain exhilaration and much learning. As a result, this foray into building a keelboat mast has enabled the New Zealand company to expand its capabilities to a new level, which is already bearing fruit in the form of new mast orders of similar size. If Geneva-based Thomas Jundt’s QFX project was an ancient mariner’s chart, it would be represented by the “terra incognito” regions, where dragons and sea monsters roam. High up in Jundt’s written brief is the rare injunction: ‘I do not need any guarantees against breaking’. Jundt is a soon-to-retire civil engineer, who is well-known in the lake racing scene for his willingness to explore new frontiers. His previous Mirabaud project, for example, tested the notion that foiling boats could dispense with hulls. The Mirabaud solution comprised a carbon web of tubular trusses supporting a rig and foils with virtually zero static stability. When it flew, it was very fast, but it depended
74 SEAHORSE
on a very specific and limited set of conditions to perform. ‘Nevertheless, it is the only boat to win the Rolle- Geneva race flying all the way and still holds the monohull race record,’ says Jundt.
The QFX project is aimed at creating an all-round lake performer, capable of high performance racing in anything from 0-30kts of wind. The concept is for an extremely light machine with three distinct modes: it must be highly efficient in displacement mode in 5-6kt breezes, which predominate on the lakes; as boatspeed lifts to around 10kts, it would utilise Hugh Welbourn’s DSS technology to semi-foil; and at 15kts, it should fly.
Stability comes from a deep bulb keel and three, possibly four, crew stacked out on trapezes. Jundt’s brief to all the technology partners was to pare back weight to the bare minimum. ‘I am a civil engineer,’ he explains. ‘For 40 years, I have had to build things with wide safety margins. The result is that everything is overbuilt, too big, way too heavy, too much material.’ In contrast, he admires the thinking behind the World War Two Mosquito strike aircraft that was built light in laminated wood, much like a yacht. ‘It was built to a safety factor of 0.8 and when it broke, they repaired it. That is my approach with this project.’ C-Tech’s reputation and expertise is based on its close involvement with skiff sailing, which is hardly the domain of the timid. However, even in an environment accustomed to pushing the limits, there is a sense
Above: tow testing the new 35ft QFX with its Hugh Welbourn- designed two-stage foils on Lake Geneva. The fundamental difference between this radical lake racer and almost any other boat ever built is that this one is designed with a far lower safety factor – even lower than an America’s Cup project. The benefit, of course, is a much lighter yacht that flies more readily on its foils. The entire rig weighs just 22kg and the mast wall is only 2mm thick, yet it supports a luff load of almost two tonnes in just 5kts of breeze... and will be raced hard in 30kts!
of tension between genuine admiration for Jundt’s daring ambition and trepidation over its practical implications.
‘A standard engineering approach is for a safety factor of 2.75, Willetts explains. ‘America’s Cup projects operate at about 1.3 to 1.5. Thomas wants to go less than 1.’ Working with Chris Mitchell at Applied Engineering Services and with Doyle Sails New Zealand, whose Sail Pack software provided accurate load cases for the rig, Willetts came up with an initial design weighing in at what he considered a minimal 30kg. After considerable dialogue – much squealing and squirming – that figure was pared back to 22kg. In that process, both sides applied a certain amount of subterfuge. ‘I told Tim I was reducing the righting moment, so the loads would be less,’ Jundt chuckles. ‘In order not to argue with him, I gave him the wrong righting moment.’
On the other hand, Willetts also snuck in a couple of provisional safety elements in case it transpires that the unsupported topmast section needs some assistance when the 90m2 Code Zero, which generates a luff load of 1,800kg in just five knots of breeze, is inevitably used to go upwind, for example; or an inner forestay is required to balance a deeply reefed mainsail. Describing some of the challenges in building down to such fine margins, Willetts explains: ‘The mast section is fairly big, which means the wall is only 2mm thick, which raises the risk of buckling.
LORIS VON SIEBENTHAL
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