Sail-Assisted Power: The Ultimate Hybrid - Yachts International
The unfashionable motorsailer may be about to make a comeback: Enter the sail-assisted superyacht.

In 1967, a German hydraulics engineer named Wilhelm Prölss proposed a square-rigged bulk carrier with six steel tripod masts. The innovative vessel was designed as a fuel-saving solution for commercial shipping in response to the looming OPEC oil crisis, but decades passed before the advent of lightweight composite materials, advanced hydraulics and optic sensors meant his theory could be put into practice. It took nearly 40 years before the venture capitalist Tom Perkins latched onto the DynaRig concept for his radical Perini Navi sailing yacht, the 289-foot (88-meter) Maltese Falcon.

Each successive rise in oil prices has led to renewed interest in sail-assist technologies. SkySails in Germany, for example, has tested high-altitude kites attached to the bows of cargo vessels with positive results. But only in recent years, as yacht owners come under increasing pressure to be seen as green, have designers started devising hybrid superyacht concepts that harness the wind to reduce fuel consumption.

Oliver Stacey is a British designer who honed his skills working alongside industry veteran Martin Francis. Together with naval architects from BMT Nigel Gee, Stacey has developed a 262-foot (80-meter) sail-assisted explorer concept called Norse, after the Viking longboats that inspired it.

“Despite appearances, Norse is a hybrid electric motoryacht that uses the wind as a secondary source of power,” Stacey says. “Sail-assist is a readily available technology that, in the right conditions, can save on fuel consumption at least 20 percent.”

Norse is a 262-foot sail-assisted explorer concept by  Oliver Stacey that draws on auxiliary wind power for passagemaking.

Norse is a 262-foot sail-assisted explorer concept by Oliver Stacey that draws on auxiliary wind power for passagemaking.

The vessel’s low-aspect sailplan has three identical wing masts and in-boom furling mainsails, a configuration that enhances reliability and flexibility while requiring minimum manpower for handling. Sail-assist mode would be engaged to reduce fuel consumption during long-distance passagemaking, and is expected to improve the vessel’s motion.

“One of the original themes that we wanted to address was eco-sensitivity,” says James Roy, yacht design director at BMT Nigel Gee. “When we actually sat down and thought [about] how we could achieve that, you can’t get away from the fact that using the wind was the obvious solution. But we didn’t just want to design a sailing yacht. In a way, this is the ultimate hybrid.”

Norse is designed with multiple climates in mind, but would be built to Polar Class compliance for cruising to remote destinations and higher latitudes. The yacht would have a shallow draft, dynamic positioning for increased maneuverability in restricted areas, and zero-discharge capability for environmentally sensitive areas.

Breaking with convention, Stacey says that only the superstructure would be fully faired and painted, with the aluminum hull unfilled and unpainted. An A-frame crane integrated into the stern could launch and retrieve a seaplane to extend the range of exploration.

VPLP Design in France has come up with a similar concept. First proposed in 2015, the 282-foot (86-meter) Komorebi explorer—named after the Japanese word to describe sunlight filtering through the leaves of trees—draws on a stabilized monohull platform, hybrid electric propulsion and automated wing sails that can drive the yacht at 15 knots with 20 knots of wind, reducing fuel consumption by around 30 percent.

VPLP is developing an automated wing sail system for its Komorebi concept, a 282-foot trimaran.

VPLP is developing an automated wing sail system for its Komorebi concept, a 282-foot trimaran.

“These are not pure sailing yachts or pure power vessels,” says VPLP co-founder Marc Van Peteghem. “You can use power or sail separately, but most of the time you would probably use both together. As an explorer, the idea is to enhance range and autonomy rather than speed.”

VPLP’s interest in rigid wing sails began in 2010, when it collaborated with BMW Oracle Racing, winner of the 33rd America’s Cup. Despite the superior aerodynamic efficiency of rigid wing sails, they cannot be reefed or furled like fabric sails to reduce their surface area. To overcome this obstacle, the studio is pioneering a new soft-wing sail technology called Oceanwings, which also can serve as a sail-assist solution.

Entirely automated, self-supporting and rotating through 360 degrees, Oceanwings adapts its angle of incidence to the point of sail to ensure optimal propulsion. Power is managed by trimming camber and twist. According to VPLP, Oceanwings is efficient to the point of halving the surface area required to propel a vessel under conventional sail. The design studio initially developed the technology with commercial shipping in mind, but Van Peteghem says the concept is more likely to be picked up by eco-conscious superyacht clients. His team has installed the Oceanwings system on a 23-foot (7-meter) trimaran prototype to fine-tune performance models.

“Of course, it depends on how you want to use your yacht, but it’s also a question of responsibility and image,” says Van Peteghem, who is taking shipyard quotes for a 305-foot (93-meter) project based on the Komorebi concept. “I believe it’s time to propose more eco-sensitive solutions to the power market. A lot of today’s owners don’t want, or simply can’t afford, to be seen as the bad guys, and I think it’s our duty as designers to start moving in the right direction.”

You could argue that sail-assist is just another name for motorsailing, and you wouldn’t be far wrong. Unfortunately, the term is associated with vessels that are too under-canvassed and heavy to move at anything like hull speed in average wind conditions without engine assistance. Laurent Giles Naval Architects in the U.K. took this criticism to heart when designing the 360-foot (110-meter), four-masted Atlas concept in collaboration with H2 Yacht Design.

Atlas, the 360-foot mega-motorsailer concept from Laurent Giles Naval Architects and H2 Yacht Design.

Atlas, the 360-foot mega-motorsailer concept from Laurent Giles Naval Architects and H2 Yacht Design.

At first glance, Atlas looks like other sail-assist projects, but Steve Wallis, co-director at Laurent Giles, prefers to call it a mega-motorsailer that can sail as fast as it can motor. Using a hybrid electric power plant that can store electrical energy, the vessel could motor in excess of 18 knots. Under sail in a fresh breeze and depending on the wind angle, she could cruise at comparable speeds. Moreover, multiple sails mean their individual sizes would be relatively small and, combined with automated sail handling, could be operated with a conventional number of crew. Cruising with sails alone would eliminate all but hotel loads from the power plant, with the advantage of near-silent operation.

“Sail-assist or motorsailing is something the superyacht industry has not really woken up to, and the potential to use the wind to either reduce power requirements for a given speed or eliminate it completely most of the time—apart from generators—is underappreciated,” Wallis says. “I think part of the problem is that motor-yacht owners discount sails because they don’t understand them, are worried by extra crew requirements and don’t like heeling over. On the other hand, sailing yacht owners probably want performance and think motorsailers are old clunkers.”

The fact is, even cruiser-racer sailing yachts spend relatively little time under sail alone, especially during long crossings with reduced crew. Too little wind and the yachts make heavy headway; too much and they risk breaking expensive spars and sails.

A sail-assisted vessel not only provides much less heeling with the interior volume and deck space of a motoryacht, but it also offers image-conscious owners the opportunity to flaunt their green credentials.

Who knows? The concept just might turn the motorsailer into the new icon of cool.

  

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