When it comes to displacement, racing yachts today cover the widest spectrum – from fully flying AC75s to the heavyweight J Class. In between lie light displacement and planing boats, and now, filling their own unique sector, are yachts fitted with a lateral foil, or retractable Dynamic Stability Systems (DSS) foil, the latest of which is the Infiniti 52.

The Infiniti 52 follows on from the company’s Infiniti 36 and Infiniti 46. The first example of this Hugh Welbourn-designed offshore racer, Helsinki lawyer Arto Linnervuo’s Tulikettu, was launched in early 2022.

She was sea trialled on the Solent in the spring of 2022 where she managed 28 knots, while her creators anticipate the design is capable of regularly achieving 30-plus knots. 

Sadly Tulikettu suffered a severe collision during a delivery trip off north-west Spain at the end of April 2022. Her crew abandoned ship and after an unsuccessful search she was presumed sunk.

However, in an incredible turn of events, Tulikettu was spotted by a passing yacht. That yacht’s crew reached out to the team via their social media channels and the search operation was immediately restarted.

Tulikettu was found on Saturday, June 4, approximately 100 nautical miles west of Cape Saint Vincent, the southern tip between Lisbon and Gibraltar. The yacht was towed to the port of Portimão where she underwent a thorough inspection and assessment of damage sustained.

In another incredible turn of events, the damage was not as significant as was originally thought and the boat was able to be repaired and relaunched. She recently completed the very heavy weather 2023 Rolex Fastnet Race, so any fears of another failure will have been very much allayed.

Tulikettu taking part on the 2023 Rolex Fastnet Race. Photo: Paul Wyeth/pwpictures.com

DSS myths

The basics of the DSS foil are generally understood – deployed to leeward, it provides lift that is ‘dynamic’, ie the faster the boat goes, the more lift and righting moment the foil automatically generates. It’s like having extra crew miraculously appear on the rail or bulb weight increase whenever a gust hits.

But many of the DSS foil’s characteristics are less obvious. For example, the foil providing righting moment ‘on demand’ allows the keel to be both lighter and shallower with less need to follow the trend of maximum hull volume and a scow bow providing form stability. This equates to a lighter, not to mention better looking, boat.

The shape and configuration of the DSS foil has been refined over years with computer modelling, tank testing and tens of thousands of race miles. Photo: Rick Tomlinson/Infiniti Yachts

In light conditions, when the foil on the Infiniti 52 isn’t doing much, it can be retracted leaving a ‘regular’ hull shape. However, the Infiniti 52 comes into its own when sheets are cracked and the breeze is above 10 knots – thus its true forte is coastal and offshore racing.

Another subtlety of the DSS foil is how it ‘locks’ the boat to the water, not only reducing heel, but also pitching. A side effect of this is improved flow across the rig and the foils, increasing their efficiency, especially upwind and/or in waves.

However, there are several myths and misunderstandings surrounding the DSS foil. It does not produce massive (or indeed any) lee helm when it is deployed. While,the DSS foil provides righting moment on demand, it also creates significant lift beneath the boat. Thus most of the time it is reducing displacement and speed-sapping hull drag, but there are times (and I can attest to this first-hand) when suddenly it goes quiet on board and for a few seconds you are fully flying, IMOCA-style.

Below: the DSS foil gives the Infiniti a much more bow-out attitude compared to other 52 footers. Photo: Rick Tomlinson/Infiniti Yachts

Third parties have unsuccessfully fitted small DSS foils forward on racing yachts with the sole aim of keeping the bow out. While a properly positioned Welbourn-designed DSS foil achieves this too (compare the videos on social media of the Infiniti 52 at pace to that of the Pac 52 Fox at St Thomas International Regatta) this is but one small part of what the foil is designed to do.

Critics of the system argue that the DSS foil ‘cannot be as good’ as the foils used on IMOCA 60s or America’s Cup yachts as they are not trimmable. For example, there are no complex hydraulics to adjust rake.

However, that fails to appreciate the difference in approach: the DSS foil is designed to provide, on the one hand, a turbo boost to performance at times, while on the other being simple and easy to use (you pull the foil out and that’s more or less it) thus allowing it to be used by regular sailors without physics degrees or supreme athleticism. And far from the lack of trimmability making the DSS foil ‘dumb’, it takes a keen eye and some wisdom to appreciate the subtlety of its shape, curvature, and section, as well as how it relates to the water plane, the centre of buoyancy, and the boat’s centre of effort.

Obviously a DSS foil doesn’t provide benefits in all conditions. The foil is usually retracted upwind unless there are waves and when sailing VMG downwind in up to 15 knots: less boat speed equals less lift.

Thanks to the DSS foil, typical heel angles are less than 20° and as a result it was considered there was no need to have twin rudders. Photo: Rick Tomlinson/Infiniti Yachts

Taking on TP52S

Fifty-two feet is an interesting length for a new pure racing design as it allows direct comparison with Super Series 52s and Pac 52s. In comparison to the former, the Infiniti 52 has a slightly taller mast, deeper keel and is fractionally heavier. Kiwi pro sailor and sailmaker Stu Bannatyne is well placed to make comparisons: he sailed extensively on the Infiniti 46 Maverick (class winner in the Rolex Middle Sea Race, RORC Transatlantic, Newport Bermuda, etc.) but among his many accolades also won the 2022 RORC Caribbean 600 on Christopher Sheehan’s Pac 52 Warrior Won.

Bannatyne notes that even the offshore-orientated Pac 52s to date have come from hull moulds of boats designed for windward-leewards in the 52 Super Series. By contrast, the Infiniti is one of the few 52-footers designed for offshore racing from the outset.

The case for the DSS foil runs discretely across the cabin sole. On larger boats it can be hidden beneath soleboards. Photo: Rick Tomlinson/Infiniti Yachts

“If it was to line-up against a Super Series boat in 12 knots upwind or anything similar, it would probably be a bit slower,” notes Bannatyne. “Anything outside of that – any reaching or downwind sailing, the Infiniti should be faster and as soon as you get powered up reaching and running it should be a good chunk faster. And not just in conditions where the DSS foils are being used – it should be faster in all underpowered conditions, when the Infiniti has lower form stability and therefore lower drag.”

While the Infiniti 46 has twin DSS foils that ‘flipped out’, with one on each side, the 52 has a single DSS foil that slides laterally across the bottom of the boat within a casing. Instead of the 46’s canting keel and canard, the 52 has a fixed keel and 600kg water ballast, split into twin tanks each side aft. This provides stability upwind and Welbourn says he prefers this arrangement as the added weight of the water need only be brought on board when required. The water ballast also permits crew numbers on the Infiniti 52 to be reduced to between seven and 12 depending upon the race.

The carbon fibre wheels are made by French company Isotop, who also built the rudder, DSS foil and foil case. Photo: Rick Tomlinson/Infiniti Yachts

Offshore focus

Compared to a TP52, for example, the Infiniti 52 has a much smaller cockpit with a sliding companionway hatch, while considerable effort has gone into preventing water getting below, such as avoiding apertures in the deck. In case of dismasting while at sea, the mast (from New Zealand Rigging) is deck stepped.

Offshore capability has also affected the sail wardrobe from Doyle, with a broad inventory, including many reaching sails. To permit varied cutter-type headsail configurations (up to three sails can be hoisted up front at a time), there are six tack positions from the spinnaker flown from the end of the 3m long bowsprit to the furling J4/staysail and storm jib mid-foredeck.

The net result is a boat that is one of the world’s fastest 52ft monohulls: particularly impressive is its ability to hold sail in 20-plus knot winds with the TWA just forward of the beam. While Tulikettu had been optimised for fully crewed offshore, the 52 could be reconfigured for short-handed offshore racing.

Infiniti 52 specifications

LOA: 16.0m / 52ft 6in
Beam (max): 4.5m / 14ft 8in
Draught: 3.6m / 11ft 9in
Mast height: 21.5m / 70ft 6in
Weight: 7,200kg / 15,873lb
Water ballast capacity: 600kg / 1,322lb
Mainsail area: 103m² / 1,108ft²
Headsail area: 68m² / 731ft²
Spinnaker area: 278m² / 2,992ft²

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