Raising the bar further

This new 123ft flagship design is a significant step up for Southern Wind…

Southern Wind has long been renowned for creating some of the world's most desirable performance superyachts and its new 37.5m SW123 flagship raises the bar further in terms of design, elegance and engineering. This yacht also represents the pinnacle of the yard’s successful Smart Custom philosophy.

It’s a ground-breaking Farr design that was conceived with the aim of creating the lightest possible performance cruising yacht of this size and style, with a carefully judged balance of luxury, reliability and performance. It’s designed for fast and exhilarating long-range cruising, yet offers exceptional comfort and luxury.

Even in this part of the market it is important to remember the advantages of light displacement extend far beyond achieving planing speeds in a good breeze. In particular it also brings significant benefits in terms of comfort.

For a start, enhanced light-air performance means you can sail at respectable speeds when other yachts will be motoring. This is clearly illustrated by the polar performance data, which shows the boat sailing upwind at 8.37kts in only six knots of true breeze.

Close-hauled in 10kts of true wind the SW123 will still be sailing faster than the breeze, with 10.95kts of boatspeed. This figure rises to more than 14kts when reaching in 12kts of wind and rises to 18.7 kts broad reaching in 22kts TWS. This speed potential can also markedly increase comfort levels when passagemaking, enabling navigators to route around unfavourable weather systems in much the same way as Imoca 60s and giant Ultim trimarans.

When Seahorse visited the Southern Wind shipyard in Cape Town earlier this year, the construction of hull moulds for SW123#1 was already well under way

The design of the SW123 is optimised for a loaded displacement of 120 tonnes on a waterline length of 34.4m (113 ft) and a light displacement of 105 tonnes. If these sound like hefty figures it’s simply a reflection of the sheer size of this yacht, as the displacement-length ratio (DLR) is just 79 at light displacement and only 82 at half load, putting the SW123 in the ultra-light category. These numbers make it proportionately lighter than a J/70 and broadly similar to a Cape 31.

They are extraordinary figures for a fullon superyacht that requires a complete complement of heavy hotel systems to deliver the luxury environment that most owners seek. This has been achieved as a result of Southern Wind’s long history of building performance yachts, adopting new technologies and adapting them to perfectly suit a superyacht environment.

Farr Yacht Design’s VPP for the SW123 promises exceptional performance

The yard first started building in carbon, for instance, more than 25 years ago with the SW80 Acaia Cube and has used epoxy infusion since 2005. Three-piece hull mouldings that help optimise resin ratios followed in 2008. The sophisticated, customisable interiors are also as light as possible, with honeycomb or foam cores used for bulkheads and furniture.

How does Southern Wind’s Smart Custom concept relate to the SW123? This model was conceived from the outset as a versatile platform that can be adapted to match each owner's expectations and intended use, without needing to re-engineer critical aspects of the structure or essential systems. By blending customisation with these proven concepts, the Smart Custom system creates vessels that reflect the identity and requirements of their owners, while reducing lead times for construction and improving reliability.

‘We offer clients the feeling that they are able to create their own yachts,’ explains chief commercial officer Andrea Micheli. ‘Of course extreme yachts can only be full custom builds. However, many custom sailing yachts have a brief that aligns with what we can offer.’ In many respects Southern Wind’s Smart Custom yachts have the look and feel of being unique and they all incorporate a host of individual owners’ requests. SW123 #1, for instance, has a telescopic keel with a draught ranging from 3.85 to 5.9m, but lifting and fixed fin options are also offered.

The first SW123 is already under construction, with launch scheduled for February 2027, and when Seahorse visited the Southern Wind shipyard in Cape Town earlier this year the hull mould was nearing completion. This yacht is designed with the goal of being available on the charter market, in addition to being sailed and enjoyed by her owners.

SW123 #1 will have a serial hybrid propulsion system, with the primary objectives of enhancing comfort and flexibility of operation. Her battery banks will be sized to run all hotel systems, including air conditioning, overnight and for most of the following day. ‘We believe hybrid installations are important for our clients,’ says SW CEO Marco Alberti, ‘as the real value for them is comfort – there's a significant gain for owners in that aspect.’ He adds that while sustainability is important, it’s not the primary driver.

The SW123’s saloon is a mezzanine configuration with two separate but directly linked social spaces

‘On boats of this size it’s never possible to completely eliminate generator noise,’ adds Yann Dabbadie, SW technical manager, ‘so the possibility of silent operation offered by hybrid systems is very important.’ He also notes that with diesel-electric hybrid operation, motoring and motor-sailing are considerably quieter than with a diesel propulsion engine. What makes hybrid propulsion appealing is the ability to motor powered by quiet, encapsulated generators. The SW123 will motor at 11kts with the same level of noise that a superyacht with traditional propulsion would have at anchor, with only its generators running. Also, the SW123’s hybrid system offers about 20 miles of range in completely silent, zero emissions mode. Alternatively, a conventional diesel with IMO Tier lll compliance, as required for all propulsion engines over 130kW, with selective catalytic reduction can be fitted instead.

Viewed from any angle SW123#1’s deck profile is impressively sleek. Other coachroof options are offered and each yacht in the series will have unique features

Farr Yacht Design: a further evolution of a successful concept

The design of the Southern Wind 123 continues the overall concept begun with the SW96 and SW105, and followed up through the SW108. The new SW123 incorporates and advances the styling, hull design, appendages, and construction concepts that have continually been evolving from the earlier designs.

The hull shape, appendages and rig of the SW123 are designed to fully exploit the Smart Custom philosophy of Southern Wind Shipyard. While SW123-1 will have hybrid propulsion and a telescopic keel and be oriented towards cruising, there are options for various keel configurations with sailplans to suit many performance levels.

Beginning with the overall length of 123ft, that includes all the desired interior components and the unique Southern Wind folding transom giving access to the tender. The first choice is the length of the waterline and associated bow and stern overhangs. The light ship displacement of 107 tonnes yields a displacement-length ratio [(displacement/1025)/(length³) x 1000] of approximately 2.83 (or 79 in the standard imperial calculation) on a DWL of 33.59m. The choice of the waterline length is biased more to the loaded cruising configuration displacement of approximately 119.8 tonnes on a waterline length of 34.4m and results in a relatively longer aft overhang to prevent excessive transom immersion and drag.

The arrangement of the aft overhang length and transom height are carefully integrated with the opening transom and tender garage for ease of tender operations. The generously wide aft sections and transom of the SW123 allow for more internal volume and deck area, both of which are advantages for a highperformance cruising yacht. This generous width is carefully balanced with extra volume in the forward sections to ensure the yacht remains in control with a level fore-and-aft trim when sailing at typical upwind heel angles.

The optimised balance of canoe body beam-to-draught ratio (BTR), the ballast in the keel and the overall vertical centre of gravity are the primary drivers of performance of the yacht across the wind range. Some of the key considerations in choosing these parameters for a highperformance cruising yacht, designed to perform well in the generally light conditions of the Mediterranean, are: low hull wetted surface area to keep the size of the sailplan manageable, narrow beam at the waterline for an easily driven hull, relatively more ballast because the yacht often sails in flat water and a high righting moment for good upwind performance in moderate and strong winds.

Higher BTR increases wetted surface area, wave drag and resistance when sailing in waves but also increases stability and can reduce the amount of ballast required. Higher BTR is required in very light boats as a means to achieve the needed stability for good performance. The SW123 has a BTR of 5.9 which balances well with the displacement length ratio of 82 and keeps wetted surface to a minimum. The proposed ballast bulb weighs 26.5 tonnes producing a ballast ratio of 34.8 per cent (light ship) with the weight of the keel fin included in the ballast. For a yacht the size of the SW123 the maximum beam, relative to the waterline beam, is driven more by the needs of the interior and by styling than by basic naval architecture and performance. A relatively narrower maximum beam reduces weight and windage and improves performance. The maximum beam of the SW123 at 8.19m accommodates the interior and styling requirements without being excessive.

Parameters	SW123
LOA	37.46m
DWL	34.4m
Displacement (light)	107.3t
Beam (max)	8.19m
Beam (waterline)	6.94m
Draft	5.90m
Wetted surface (light)	207.3m²
Sail area (upwind)	740.3m²
SA/WS (light)	3.57
DLR (light)	79.0
Ballast ratio (light)	34.8

The hull shape of the SW123 has been developed to accommodate a twin rudder configuration in conjunction with either a lifting or telescopic keel, giving a manageable draft of 3.85m (keel raised). The twin rudder configuration is very efficient at the typical heel angles experienced when sailing upwind and when reaching as the two rudders can be installed farther aft in the yacht than a single rudder. The drag of a partially immersed windward rudder is typically very low in conditions when the full load is carried by the leeward rudder. It is not necessary for the windward rudder to be completely out of the water to achieve target speeds. The optimised transverse separation of the rudders was chosen after an analysis of the expected operational heel angles. This optimum separation is adjusted with consideration of the interior requirements in the aft areas.

The generous size of the sailplan ensures excellent light wind performance and ample acceleration in light winds. The aspect ratios of the mainsail and headsail and the distribution of area between the mainsail and headsail were selected to promote flexibility for efficient depowering while maintaining the overall balance of the configuration. The BTR generates stability without the need for excessive ballast weight.

Despite the generous size of the battery banks, the hybrid system generators are sized to be able to return the batteries to a full charge state in as little as 30 minutes. You can therefore wake up without the noise of a generator and it doesn't need to run until lunch.

The fold-out transom creates a large beach club area with an easy flow to and from the aft deck

Although the ultra-sleek lines of the first example resemble those of a flush-deck yacht, it has a generous raised saloon with enough space to provide 1.7m of headroom in the engine room below, while other coachroof options are offered as part of the Smart Custom concept. Cockpit arrangements are also fully customisable. The first Southern Wind 123 shares many design parallels with SW108 #2, Kiboko 4, which launched in February 2025.

A key priority was to provide cockpit protection without spoiling the SW123’s exquisite lines. The design therefore includes a removable sprayhood and the lower forward cockpit area also has excellent shelter behind the coachroof, which is at shoulder height when seated. To provide ample shade the bimini extends as far aft as the sun beds.

Southern Wind’s construction process has been gradually refined and evolved

While it might have been tempting to use the full 26ft beam of this yacht to create a wider on-deck living space, doing so would not be practical when heeled. ‘Wide is nice, but over wide is dangerous,’ cautions Micheli, adding ‘the yacht must be safe and practical.’ Crew members who are actively engaged in handling the boat can wedge their feet against the small island coachroof aft when sailing. Primary and secondary winches are within easy reach of this position, while the aft winches are mounted on the coaming at a comfortable and safe height for easy use even in strong winds.

Access to the water is via a two-component folding transom that creates a large beach club area connected to the expansive aft deck seating/sunbathing space via two curved staircases. Folding out the transom also reveals access to the tender garage, which is designed to accommodate a 17ft (5.35 m) diesel tender, as well as extensive on-deck stowage each side for watersports toys and other equipment.

It’s well known in the yachting industry that attracting suitable crew can be challenging and that comfortable accommodation for them is a critical factor in recruitment. The SW123 therefore features spacious three-cabin, three-heads crew quarters, which includes a well-appointed eight-seat crew mess at the hub of the yacht, plus a large (12.2m²) galley. ‘It’s crew friendly and highly appreciated, which is important for us,’ says Alberti.

The shape of the hull mould is created with timber battens and plywood, then laminated, infused and split into three parts

Nauta Design is responsible for the exterior styling and for the interior, which extends to 165m² in total. This includes a 25m² owner's cabin with an en suite heads, a 13.6m² VIP guest cabin, plus 12m² guest cabins on both the port and starboard sides. There’s also a separate TV lounge. In boat #1 the owner's cabin features a desk with two seats.

The yard liaises closely with clients to optimise the accommodation layouts, furnishings, systems and finishes to match their tastes and needs. As a result, no two Southern Wind yachts have the same style or ambience. When Seahorse visited the yard, for example, discussions with the owners of SW123 #1 were well under way regarding internal options and they were just about to begin conversations on colours, décor and other details of the interior finish.

At the end of the process they will have an enormously desirable, supremely comfortable and powerful yacht that's tailored to their exact tastes and needs. It will be an excellent platform for Mediterranean and Caribbean sailing, as well as for participation in superyacht regattas and for exploring further afield.

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