DSS, the strange wings sprouting from monohulls: history, benefits, examples

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dssFrom the insight and research of British designers Hugh Welbourn and Gordon Kay, experiments with DSS (Dynamic Stability Systems) foils began on monohulls in the early 2000s. In fact, Hugh Welbourn had already been on this track since the late 1990s and proposed to Ellen Macharthur that she experiment with these appendages on the Kingfisher, the boat in which she would participate in the 2000 Vendée Globe. The Briton declined the proposal, fearing too radical a technical solution for a project crucial to her career.

DSS were initially tasked with improving the boat’s righting moment and consequently performance. Later, as shapes and technology evolved, in addition to dealing with straightening, they began to look for lift, or so-called lift effect, which exponentially increased speeds.

Early appendages of this type consisted of a single horizontal, telescoping blade working downwind just at the beginning of the live work. Especially in the last 5 years, with the development of C- or L-shaped dinghies, there has been a gradual effort to increase vertical buoyancy as well, and numerous versions of DSS foils have emerged, differing from each other even according to the boat on which they were applied.

Except in a few cases, such as the Quant 23 released in 2014, most of the DSS appendages we have seen at work in recent years on monohulls are hybrid, that is, they favor both righting and lifting in a balanced way. The case of the Quant 23 is different: thanks to a lightweight and small design, it was possible to successfully apply C-shape drifts that enabled true full foiling, that is, the complete exit of the hull from the water. A phase that is now in full swing among Mini Transat prototypes, whose flight is more complex due to canting keel (canting keels) significantly bulkier and more powerful than seen on the small Quant.

THE “LANDING” OF DSS AMONG THE CRUISERS

Today, with the landing of foils on the IMOCAs, in the Mini class and among the Figaro, other designers are tackling this technology with increasingly spectacular results. The new frontier, however, seems to be cruising boats, and once again it is Gordon Kay’s Infiniti Yachts, with the new 56′, that is charting a new course: cruising on foils. From this point of view, DSS could really be a great upgrade for the cruising world, going on to improve a detail that is very dear to sailors who seek comfortable and quiet sailing: righting.

Less heeling equals more comfort, thus greater enjoyment of sailing, a perfect paradigm for the recreational world as well. Like all cutting-edge technologies, dynamic stability systems seek extreme limits in the racing world, only to find application with more proven versions on the cruising front.

The simplification of appendage handling systems may thus have reached a point where they are being offered to the general public, and potentially in the more or less near future we may see a cruising boat equipped with foils in large series production.

FROM DINGHIES TO LARGE OCEAN RACING BOATS, NOW DSS IS ALSO COMING TO THE CRUISING WORLD

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CQS (2016)
It was originally Nicorette, the 90-footer designed by South African Alexis Simonis. With the design by New Zealand firm Bakewell-White Yacht Design, it was lengthened to 100 feet, front volumes were reduced, and DSS foils were installed, as well as a special system for handling the shrouds. In this case, the main task of the appendages is to improve straightening and to a lesser extent to reduce hydrodynamic drag.
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INFINITI 36 (2012)
The daysailer according to Infiniti Yachts: a sporty boat, not extreme but very high performance, equipped with classic DSS foils. A horizontal, retractable blade that works just below the surface of the water. The more wind there is, the more the appendage is stretched, which upwind improves righting and on the slack at high speeds decreases hydrodynamic drag. This is the first model produced by Infiniti Yachts.
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INFINITI 56C (2017)
It could be the boat that will revolutionize the world of blue water cruising. This is the first real test of DSS on a pure cruising boat. The appendages will find a non-invasive internal location: working just below the surface of the water, on a horizontal trim, they can be installed without affecting the internal volumes.
THE EVOLUTION OF FORMS. Curved or L-shaped drifts are the recent frontier of DSS. Through the evolution of shapes, the function of appendages was no longer only to improve righting, but also to drastically reduce hydrodynamic drag. A solution that for monohulls is currently used only on small boats.
dss
QUANT 23 (2014 ) Hugh Welbourn’s design for Quant Boats can be considered the first “flying” monohull. In fact it is practically a drift with shapes curiously reminiscent of the Fireball. Thanks to the curved foils, above 12-13 knots the boat, with the DSS at full dive, is able to achieve full foiling. Under this intensity, foils mainly help straightening.
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QUANT 30 (2012)
Typical lake “drift” equipped with terraces and DSS appendages. It is the first boat Quant Boats has produced in a proper series, with a simplified appendage handling system. Equipped with classic DSS straightening foils, which at high speeds trigger a moderate lift effect by reducing hull drag on the water.
QUANT28 (2010)
It marks Quant Boats’ debut with DSS technology. It is the most extreme of the Quants, in fact the only difference with an acrobatic drift is the absence of trapezoids. The design is still by Welbourn but is dedicated to experienced sailors given the lightness of the hull (550 kg with 140 mw of canvas at the carriers). It is equipped with an early version of the DSS foils.

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