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What’s In A Rig? – Wingsail

By: Pat Reynolds Sailboat Rigs , Sailboats

What’s in a Rig Series # 8 – The Wingsail

Although wingsails or rigid wings have risen to the limelight in the contemporary sailing world with the America’s Cup now employing the technology across the board, they are in no way a brand new concept. A sail, after all, in its purest form is essentially a wing. So, through the decades, many designers, looking for optimum performance, have of course instituted rigid wings (just like that of an airplane). A notable example would be the so called Little America’s Cup, a long-standing catamaran contest based around the pursuit of pure speed.

The efficiency of a hard wing has never been in question. They sail upwind higher and reach faster. Their purity of engineering allows for maximum proficiency. When compared to a solid wing, a soft sail is full of hard to manage variables. The shape, components and accompanying systems are no match for a wingsail. In many ways, a conventional sailboat rig is fighting against itself to do what it’s meant to do. Shrouds and stays are battling to keep everything in place while a sailor adjusts control lines incessantly. It’s not perfect. However, the relative practicality is another issue. A very large unbending non-folding solid structure has its obvious drawbacks. How do you stow this thing when you’re done sailing and how do you reef it if the breeze starts blowing and, for the traditionalists, where’s the romance in a big airplane wing sticking up from the front of the boat?

Before we address those questions, let’s look at how this rig works. Using the America’s Cup boats as great examples, a wingsail itself is usually composed of two parts and the surrounding system is essentially three ingredients.

The sail has a forward and trailing element. The trailing element is like the flaps on an airplane wing and the angle between the two elements is called camber. Increasing the camber (angle) produces power. If the power becomes too much, which it often does, another control system comes into play that deals with “twist”. Twist allows the ability to depower the boat by twisting the wing so wind can spill off.

After camber and twist, the third major aspect of control on these quite simple wing setups is the mainsheet. Like a normal mainsheet, it lets the sail out, but unlike a soft sail, a rigid wing doesn’t power up downwind, which is why soft genoas are often part of the sailplan.

So, without argument wingsails are more efficient engines, but, as we stated, are not nearly as practical as soft sails. Are you sensing the idea of a hybrid coming around the bend? Yes, in fact, world renown cruising boat manufacturer Beneteau has been developing just such an innovation. They have a soft wingsail prototype installed on a production boat that blends the two concepts. It’s made of cloth so it can be broken down like a traditional scale but is, in every other way, a wingsail. It’s an unstayed mast with an airplane style wing that they say behaves very much like its rigid cousin.

So, lets revisit the particular questions we asked earlier and make sure we answered them. How is the wingsail reefed? By adjusting the aforementioned twist control, a wingsai is depowered, thereby reefed. How can this big wing thing be stowed? Well, with this hybrid idea, it’s lazy jacks and sail covers – we know how that works.

The last question is more difficult to answer…where’s the romance? The feeling, sounds and shape that soft sails embody date so far back into our collective history, it’s a bit heartbreaking to think they could possibly be replaced. There’s a certain humanity…a beauty and art involved in harnessing these inherent imperfections. We share this struggle and achievement with those who sailed before us. We have continually developed materials, hardware and better systems to get an edge, and are always happy when we succeed, but a radical refit, should it happen on a grand scale, is sort of jarring and sad.

Alas, this is the quandary of technology and advancement. Change bringth and taketh away. But don’t worry too much about it – in this modern day it seems 18-year old yellow, fading Dacron sails hung about on aging wires are still representing strong!

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November 10, 2009

The Fixed-Wing Is In: America's Cup Sailors Plan to Use Rigid Carbon-Fiber Airfoil on U.S. Entry

The U.S. team for the America's Cup is replacing its boat's mast and cloth mainsail with a hard, fixed wing that is 80 percent larger than a Boeing 747 wing, not to mention difficult and dangerous to maneuver

By Lynn Fitzpatrick

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SAN DIEGO—After more than a year of practicing for the America's Cup, the U.S. team is replacing its boat's lofty 60-meter mast and 620-square-meter cloth mainsail with a hard, fixed wing that is 80 percent larger than a Boeing 747 wing and will tower 58 meters above their giant trimaran's deck. The team, known as the BMW ORACLE Racing Team, will start to practice with and evaluate the high-strength yet lightweight carbon-fiber wing on its 27-meter carbon-composite trimaran later this week.  The Americans have been testing new frontiers with the loads that their massive multihull endures while sailing . Crash helmets, personal floatation devices and other body armor have been de rigueur during BMW ORACLE Racing's practices—even while using a mast and a mainsail, which preceded the wing. During a practice session on November 3, the boat's huge mast snapped and toppled into the Pacific. Thankfully, no one was injured. Although the team's research and development unit has been conducting a forensic evaluation of the mast mishap, another unit has been finishing the assembly of the wing under the cover of a huge tent at the team's base in San Diego, in an attempt to keep the technology a secret from competitors. The America’s Cup is the oldest actively contested trophy in sport and dates back to a race held in 1851 in England in which the yacht America beat 15 boats representing the Royal Yacht Squadron.  Members of the winning America syndicate donated the Cup via a Deed of Gift to the New York Yacht Club on July 8, 1857, specifying that it be held in trust as a perpetual challenge trophy to promote friendly competition among nations. According to an Allianz Economic Report conducted in co-operation with Tom Cannon, dean of Buckingham University Business School, the America's Cup ranks just behind the Olympics and the FIFA World Cup in terms of worldwide direct and indirect economic benefits that accrue to the winner and the event's host city. It is the largest inter-club sporting event in the world in terms of economic scale and impact. The only other time that a multihull and a wing have been used in the America's Cup was in 1988. Back then, the U.S. team defied tradition when they unveiled an 18-meter catamaran equipped with a wing to compete against New Zealand's 27-meter monohull. Burt Rutan , whose company Scaled Composites went on to win the Ansari X PRIZE for SpaceShipOne , and who worked with John Ronz, David Hubbard and Duncan MacLane on the 1988 wing, reflected on that achievement: "The wing-sail designs were more challenging (than aircraft wing applications) because they needed high lift in both directions and because we had a requirement to vary the wing twist to account for different wind gradients above the sea. An aircraft wing lifts in only one direction and does not have any twist control. On the wing-sail we twisted the third element and thus had to make it torsionally flexible." The scale of the 21st-century sailboat and wing is astronomical compared with the 1988 vintage. The 1988 wing height was slightly over 30 meters, and its area was approximately 165 square meters. The new wing's main element is a monolithic box with an aerodynamic nose along its leading edge. Hinges at different points along the main element's trailing edge can be adjusted to change the gap between the forward and the aft elements to adjust airflow depending on the wind velocity. The sections of the trailing element can be moved independently to induce camber (the asymmetry between the top and bottom curves of an airfoil), making it possible to flatten and even induce negative camber in the top section as well as camber in the opposite direction in the lower sections. According to BMW ORACLE Racing, "the primary advantage of the wing over a soft sail is that it is easier to control and does not distort. This makes it easier for the trimmers on board to maintain an optimum aerofoil shape in a wide range of conditions." Unlike conventional monohull and multihull sailboats , the BMW ORACLE team's trimaran sails upwind and downwind at apparent wind angles less than 30 degrees (Monohulls typically sail at between 30 and 40 degrees upwind.) On board the racing machine it always feels as if the wind is in the sailors' faces. The wing technology will improve the trimaran's apparent wind angle, and may enable the multihull to exceed  two to 2.5 times wind speed. The upcoming America's Cup challenge will be the first time ever that an onboard engine will be used to assist trimmers in controlling the massive foils by powering hydraulic controls for the wing and the forward sails. Mark Ott, co-founder and executive vice president of Seattle-based Harbor Wing Technologies, the first company to employ a wing that rotates 360 degrees and uses a multihull as a platform, commented, "BMW ORACLE'S boat represents the pinnacle of race boat design; however, the nature of this design limits the wing sail's range of motion due to the shroud and forestay wires used to support it. This design limitation causes these wing sails to be impractical for use by the average sailor. By not allowing the wing full 360-degree rotational capability in everyday sailing conditions, it is bound to it be held on a shroud wire by the wind and damaged, or worse, possibly causing the boat to capsize." All eyes will be watching to see how BMW will store the boat and the wing, because the latter is not nearly as easy to take down and stow as a cloth mainsail. The America's Cup showdown is set to take place in February 2010 in Valencia, Spain.

How Does a Rigid Sail Work?

Sailing has been a popular mode of transportation and recreational activity for centuries. The traditional sailboat is powered by the wind, which propels the boat forward.

However, modern technology has introduced new ways to harness the power of the wind. One such technology is the rigid sail.

What is a rigid sail? A rigid sail is a type of sail that doesn’t use flexible materials like canvas or nylon. Instead, it uses a solid structure, usually made of lightweight materials like carbon fiber or aluminum. This structure is designed to be aerodynamically efficient and can be adjusted to optimize its performance in different wind conditions.

How does a rigid sail work? The rigid sail works on the same principle as a traditional sailboat’s sails. When the wind blows against the surface of the sail, it creates lift, which propels the boat forward. However, because a rigid sail is solid and fixed in shape, it can generate more lift than a traditional sail.

The shape of the rigid sail also plays an important role in its performance. The most common shape for a rigid sail is an airfoil, which is similar to an airplane wing. An airfoil-shaped rigid sail produces lift due to differences in air pressure between its upper and lower surfaces.

The efficiency of a rigid sail depends on several factors, including its size, shape, and angle relative to the wind direction. As with traditional sails, adjusting these factors can optimize the performance of a rigid sail in different wind conditions.

Advantages of using a rigid sail There are several advantages to using a rigid sail over traditional sails:

• Greater efficiency: Rigid sails are more efficient than traditional sails because they can generate more lift and maintain their shape better.
• Better control: Because they are fixed in shape, rigidsails are easier to control than traditional sails, especially in strong winds.
• Increased safety: Rigid sails are safer than traditional sails because they are less likely to rip or tear in high winds.

The future of rigid sails The use of rigid sails is still relatively new, but it has already shown great potential in the shipping industry. Several large cargo ships have been fitted with rigid sails, and early results suggest that they can reduce fuel consumption and emissions by up to 20%. As technology improves and more research is done, it’s likely that we’ll see more widespread use of rigid sails in the future.

The rigid sail is a promising technology that offers several advantages over traditional sails. By using a solid structure instead of flexible materials, it can generate more lift and maintain its shape better.

5 Related Question Answers Found

How does full sail work, how do sail boards work, how does a modern sail work, how does a rotating sail work, how does a magnetic sail work.

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Sail GP: how do supercharged racing yachts go so fast? An engineer explains

Head of Engineering, Warsash School of Maritime Science and Engineering, Solent University

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Sailing used to be considered as a rather sedate pastime. But in the past few years, the world of yacht racing has been revolutionised by the arrival of hydrofoil-supported catamarans, known as “foilers”. These vessels, more akin to high-performance aircraft than yachts, combine the laws of aerodynamics and hydrodynamics to create vessels capable of speeds of up to 50 knots, which is far faster than the wind propelling them.

An F50 catamaran preparing for the Sail GP series recently even broke this barrier, reaching an incredible speed of 50.22 knots (57.8mph) purely powered by the wind. This was achieved in a wind of just 19.3 knots (22.2mph). F50s are 15-metre-long, 8.8-metre-wide hydrofoil catamarans propelled by rigid sails and capable of such astounding speeds that Sail GP has been called the “ Formula One of sailing ”. How are these yachts able to go so fast? The answer lies in some simple fluid dynamics.

As a vessel’s hull moves through the water, there are two primary physical mechanisms that create drag and slow the vessel down. To build a faster boat you have to find ways to overcome the drag force.

The first mechanism is friction. As the water flows past the hull, a microscopic layer of water is effectively attached to the hull and is pulled along with the yacht. A second layer of water then attaches to the first layer, and the sliding or shearing between them creates friction.

On the outside of this is a third layer, which slides over the inner layers creating more friction, and so on. Together, these layers are known as the boundary layer – and it’s the shearing of the boundary layer’s molecules against each other that creates frictional drag.

A yacht also makes waves as it pushes the water around and under the hull from the bow (front) to the stern (back) of the boat. The waves form two distinctive patterns around the yacht (one at each end), known as Kelvin Wave patterns.

These waves, which move at the same speed as the yacht, are very energetic. This creates drag on the boat known as the wave-making drag, which is responsible for around 90% of the total drag. As the yacht accelerates to faster speeds (close to the “hull speed”, explained later), these waves get higher and longer.

These two effects combine to produce a phenomenon known as “ hull speed ”, which is the fastest the boat can travel – and in conventional single-hull yachts it is very slow. A single-hull yacht of the same size as the F50 has a hull speed of around 12 mph.

However, it’s possible to reduce both the frictional and wave-making drag and overcome this hull-speed limit by building a yacht with hydrofoils . Hydrofoils are small, underwater wings. These act in the same way as an aircraft wing, creating a lift force which acts against gravity, lifting our yacht upwards so that the hull is clear of the water.

While an aircraft’s wings are very large, the high density of water compared to air means that we only need very small hydrofoils to produce a lot of the important lift force. A hydrofoil just the size of three A3 sheets of paper, when moving at just 10 mph, can produce enough lift to pick up a large person.

This significantly reduces the surface area and the volume of the boat that is underwater, which cuts the frictional drag and the wave-making drag, respectively. The combined effect is a reduction in the overall drag to a fraction of its original amount, so that the yacht is capable of sailing much faster than it could without hydrofoils.

The other innovation that helps boost the speed of racing yachts is the use of rigid sails . The power available from traditional sails to drive the boat forward is relatively small, limited by the fact that the sail’s forces have to act in equilibrium with a range of other forces, and that fabric sails do not make an ideal shape for creating power. Rigid sails, which are very similar in design to an aircraft wing, form a much more efficient shape than traditional sails, effectively giving the yacht a larger engine and more power.

As the yacht accelerates from the driving force of these sails, it experiences what is known as “ apparent wind ”. Imagine a completely calm day, with no wind. As you walk, you experience a breeze in your face at the same speed that you are walking. If there was a wind blowing too, you would feel a mixture of the real (or “true” wind) and the breeze you have generated.

The two together form the apparent wind, which can be faster than the true wind. If there is enough true wind combined with this apparent wind, then significant force and power can be generated from the sail to propel the yacht, so it can easily sail faster than the wind speed itself.

The combined effect of reducing the drag and increasing the driving power results in a yacht that is far faster than those of even a few years ago. But all of this would not be possible without one further advance: materials. In order to be able to “fly”, the yacht must have a low mass, and the hydrofoil itself must be very strong. To achieve the required mass, strength and rigidity using traditional boat-building materials such as wood or aluminium would be very difficult.

This is where modern advanced composite materials such as carbon fibre come in. Production techniques optimising weight, rigidity and strength allow the production of structures that are strong and light enough to produce incredible yachts like the F50.

The engineers who design these high-performance boats (known as naval architects ) are always looking to use new materials and science to get an optimum design. In theory, the F50 should be able to go even faster.

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Cargo Ships Reclaim Wind Power With High Tech Rigid Sails

Canvas sails once powered the cargo ships that sailed the 7 seas, and now the modern day shipping industry is taking steps to reclaim its wind power heritage — with a high tech twist, that is. In the latest development, last week the French startup Zéphyr & Borée received validation for a new container ship decked out with 8 rigid sails engineered by the firm Computed Wing Sails.

This New Wind-Powered Ship Is No Small Potatoes

The new sails received approval in principle from the leading global certification firm Bureau Veritas, which has developed a new classification system for oceangoing wind propulsion systems .

BV certainly had its work cut out for it with the Zéphyr & Borée project. The ship is no demonstration-scale venture. It is a full sized, 185-meter (about 607 feet) cargo ship with a capacity of 1,800 TEU, which refers to the number of 20-foot containers it can hold.

That’s not nearly as big as the biggest cargo ships at sea today, which can easily top 20,000 TEU. However, it’s big enough to showcase how wind power can be scaled up to help decarbonize the global shipping industry.

High Tech Sails For More Wind Power

Zéphyr & Borée was founded in 2014 on a platform of shipping industry decarbonization , and it is casting a wide net in the wind power area.

The rigid wind power harvester designed by Computed Wing Sail is a thick, asymmetrical sail that resembles the wing of a glider. Depending on the wind conditions, it can fold down to hold a position half its height for optimal efficiency.

Zéphyr & Borée has also been working with the naval architecture firm VPLP, which has contributed its experience in designing rigid wing sails for racing yachts .

As described by Zéphyr & Borée, one challenge is to design a rigid sail that can be furled, meaning it can be folded into a more compact shape during rough weather.

The new sails also meet the challenge of minimizing crewing and training requirements.

“The control of the rigging does not require additional sailors, the settings are entirely automated and the structure meets the robustness and reliability imperatives required by maritime regulations and commercial ship activities,” Zéphyr & Borée explains.

How About Some Solar Power With Your Wind Power?

The idea of a rigid sail brings up the potential for adding on a layer of thin film solar panels. The Japanese firm Eco Marine Power introduced a patented rigid sail that doubled as as solar energy harvester back in 2011. Somewhere over the years, EMP separated the sails and the solar panels, which can be installed individually or as an integrated system.

By detaching the solar panels from the sails, EMP also gave the solar side more room to grow. EMP notes that its solar technology is lightweight and flexible, so it could be installed on awnings and other surfaces of a ship.

Earlier this year EMP received approval in principle from Nippon Kaiji Kyokai for its “Aquarius Marine Renewable Energy with EnergySail” solar and wind power combo.

EMP emphasizes that its clean power system can continue to generate electricity when the ship is at rest.  That’s a significant consideration in the context of the ongoing shipping bottleneck, which has left thousands of cargo ships waiting to dock while running their diesel engines.

New Shapes For Wind Power

Another interesting development to pop up is a cylindrical sail that resembles a smokestack, engineered by the firm Norsepower under the name Rotor Sail. The cylinder can be tilted down to allow for low bridges and other infrastructure, which opens up a broader array of shipping routes and destinations.

The Rotor Sail made its first appearance at CleanTechnica in 2015, when our friends over at Rocky Mountain Institute explained that the tubular design is an update of the Flettner rotor, a wind-powered device that spins within a cylinder.

“The rotor generates thrust for the same reason that a spinning baseball curves through the air after it’s thrown — the Magnus effect. When air moves across a rotating body, it exerts a force perpendicular to the direction of the air,” RMI explained.

All was quiet for a few years until 2019, when the tubular, tilt-able sails popped back onto the CleanTechnica radar in 2019. Norsepower has been awfully busy since then.

Among the recent developments is an agreement with the global mining and shipping giant Vale to outfit one of its “Valemax” Very Large Ore Carrier cargo ships with an array of 5 Rotor Sails .

Last month, Norsepower also signed a Memorandum of Understanding with the global maritime technology firm Kongsberg Maritime .

The new agreement adds wind power to KM’s growing portfolio of decarbonization solutions for the shipping industry.

Oskar Levander, SVP Business Concepts for KM, explains:

“This co-operation with Norsepower is an additional step towards KM’s ambition to become the leading integrator of green shipping technology, such as auxiliary wind power, alternative fuels/energy sources and energy saving devices…Together we will offer support to shipowners and shipyards looking for the most efficient and effective ways of applying Rotor Sail technology, and collaborate on new ship designs to integrate these technologies and improve energy efficiency overall.”

Onward & Upward For The Decarbonized Shipping Industry Of The Future

Of course, if people would just stop buying so much stuff from faraway places, there wouldn’t be nearly as much carbon emissions from the the shipping industry. However, that’s not going to happen. In fact, the whole industry is headed in the wrong direction.

According to the International Marine Organization, the global shipping industry (including fishing) has improved its carbon intensity in recent years. Nevertheless, the industry’s total greenhouse gas emissions are already 90% higher than the benchmark year of 2008 and they are projected to keeping increasing by up to 130% in 2050.

Meanwhile, IMO hopes to cut emissions back down to 2008 levels by 2050. It appears that wind power will be part of the solution, though only as a means of reducing fuel consumption. It’s difficult to imagine a Valemax ship of 360 meters and 400 tons dead weight powered exclusively by the wind, but using wind power to reduce carbon emissions from marine fuel can make a significant difference.

Norsepower confirmed a savings of more than 8% on fuel for its Rotor Sail back in 2018, and the company anticipates a savings of up to 25% under some conditions.

Battery-electric technology will also play a role. Though today’s batteries might not be up to propelling a full sized cargo ship, Yara has just launched a modestly sized electric ship in Norway that will amplify its own emissions savings by replacing thousands of truck trips annually on local roads.

Zero emission hydrogen fuel cells are emerging as another decarbonizing option, at least for ferries and other smaller watercraft, but only to the extent that the global supply of green hydrogen continues to grow (the primary source of hydrogen today is natural gas, but alternative sources are emerging).

For larger craft, shipping industry stakeholders are beginning to dip into the green hydrogen-ammonia field, in which renewable ammonia can be produced by combining renewable hydrogen with nitrogen from ambient air. That’s a huge sustainability step up from the current state of the ammonia supply chain, which leans heavily on natural gas.

There being no such thing as a free lunch, the shipping industry will have to do something about nitrogen oxide emissions from burning ammonia in a combustion system, so stay tuned for more on that.

Follow me on Twitter @TinaMCasey .

Image: Rigid sails provide wind power for cargo ship (courtesy of Computed Wing Sail ).

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Tina specializes in advanced energy technology, military sustainability, emerging materials, biofuels, ESG and related policy and political matters. Views expressed are her own. Follow her on LinkedIn, Threads, or Bluesky.

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Building, restoration, and repair with epoxy

Rigid Wing Sails

by John Holtrop

Cover Photo: John Holtrop sails in Kern County, California with a rigid wing sail he built.

Rigid wing sails offer high aerodynamic efficiency. They have been used in defending the America’s Cup, and are seen on some other high performance catamarans.

Aerodynamically, a rigid wing sail is identical to an airplane wing. Both reward increased lift and decreased drag. However, airplane wings are simple to design since they fly with a fairly constant angle of attack. So an airplane wing’s shape or camber can be optimized for a normal set of flight conditions. Sailboats, on the other hand, must operate under frequently changing conditions. For example, tacking a sailboat forces the airfoil shape of the sail to completely reverse itself, and wind velocity changes require that the sail’s camber and surface area be adjustable.

In the past, rigid wing sails for sailboats used hinged flaps and complex control mechanisms to achieve this flexibility. These designs were heavy, complicated, expensive, and impossible to reef or stow. Obviously, cloth sails are more practical for normal sailboats. Cloth sails are relatively simple and cheap. They can be stretched into many different shapes with simple control lines. For most sailboats, the increased efficiency of a rigid wing is not worth the bother.

A rigid wing sail’s extra efficiency (increased lift and reduced drag) is best utilized on wind surfers, ice boats, land sailors or other high speed applications. The biggest problem is designing a simple, light weight rigid wing sail. Modern composite materials make it possible to combine the efficiency of a rigid wing with the simplicity of a cloth sail.

Thin composite parts will bend easily without cracking, and these are many times stronger and stiffer than the best sail cloth. Thicker sections (solid or cored) can be added at specific locations where stiffness is critical. This allows one part of a composite structure to be rigid, while other areas are flexible. Composite materials (carbon fiber, aramid, honeycomb, foam etc.) can be added to optimize strength, stiffness and weight.

The wing sail concept combines a thick, rigid airfoil nose with a flexible center body and thin trailing edge. The wing sail is molded from composite materials in the form of a symmetrical airfoil. If the wing sail is rotated into the wind slightly, aerodynamic forces buckle the windward side of the flexible center inward and pull the lee side out. These flexible areas then deform smoothly into a shape resembling a conventional cambered rigid airfoil. The amount of camber is controlled by the out haul tension and the stiffness of the materials, just like a cloth sail. When tacking, the flexible surfaces snap over to the other side, and the camber shape is reversed (as with cloth sails). The rigid leading edge is stiff enough to handle all bending loads, eliminating the need for a traditional mast and shrouds.

While the basic concept is simple, the exact shape that the deformed wing sail will take and its efficiency, is difficult to predict without building a prototype. Some excellent research has been done on flexible airfoils, both single and double sided, with a variety of leading edges. Much of the airfoil theory in the following design was gleaned from an article written by Mark D. Maughmer (Department of Aeronautical and Astronautical Engineering, University of Illinois, Urbana) titled “A comparison of the aerodynamic characteristics of eight sailwing airfoil sections” (#N79-2389, 1972). Mark’s paper predicts at least a 50 percent lift/drag improvement for a thick, double surface airfoil, over a conventional sail/mast combination.

Theories are important, but the real proof is how well a full size operating prototype performs. I selected a wind surfer for the prototype, in order to reduce cost, weight and labor. Three years and many labor-hours later, I finally put the theory to test.

I selected dimensions based on a standard 60-70 sq. ft. wind surfer sail. Since the rigid sail was more efficient, I designed it one-third smaller, for a total of 40 sq. ft.:

• Length                         152″
• Max chord (width)        52″
• Head                             26″
• Foot                              30″
• Maximum thickness     6″

The thickness of an airfoil is usually expressed as a percentage of the chord. For low-speed efficiency, 12 to 18 percent is typical. I selected the lower value, 12 percent, to keep size and weight down. The leading edge shape was taken from a NACA (National Advisory Committee for Aeronautics) #63 cross section, which has a fairly sharp elliptical nose. I basically guessed at these values. They looked reasonable, but other NACA shapes and thicknesses may be more efficient. I attached the wishbone to a piece of tubing glassed into a socket molded behind the leading edge, and laced it to the clew with a four-to-one out haul. Then I bonded a tapered “C” section spar inside of the wing, from head to foot, at the 1/4 chord line. It terminated with a 12 inch tube, which contained a standard BIC sailboard gooseneck fitting. This spar, and the rigid leading edge, carry all of the bending loads and form a watertight chamber, providing several hundred pounds of flotation.

I built up a plug (top photo) from wood strips, and used it as a male mold for the rigid elliptical nose and tapered spar. Next, I attached plywood sides to the base of the plug to form a tear drop cross section. After I filled, sanded, and sealed the plug, I coated it with a fiberglass release film. Then I laid two layers of 60oz fiberglass over the entire plug, adding several extra layers in the nose region.

I pulled off the cured part, and glassed foam strips to the inside for increased stiffness. Next I molded a “C” section main spar to fit the plug base, fitted it to the nose (bottom photo), and glassed it into its final position. I added two layers of inch-wide, unidirectional graphite fiber to the spar caps to increase bending stiffness.

I molded the single surface trailing edge, on a flat plywood form, from two layers of 7-ounce Kevlar cloth. The unsupported trailing edge was a little too flexible, so I added three foam battens (1/4″ x1″x18″) to one side, about 24 inches apart. The openings at the head and foot of the double surface section, I filled with foam plugs, rounded, and glassed watertight.

To stress test the finished structure, I stood in the center of the spar while it was supported at both ends. My 190 pounds deflected the wing about half an inch, causing some creaking, but it held. With a fresh coat of paint and fitted with a wishbone and gooseneck, the finished sail weighed 36 pounds. This is 10 to 15 pounds heavier than a conventional rig.

Now for the moment of truth! Three of us trucked my BIC sailboard and the wing sail over to Lake Isabella in Kern County, Calif. Known for good wind, Isabella is a very popular lake for wind surfing. When we arrived, the winds were medium, about 15 knots, with occasional gusts to 20. Everyone was using big sails. The three of us tested the wing sail for the next four hours. We didn’t blow anyone off the lake, but we got a lot of attention and learned a great deal about the design.

Good features

1. The wing was very sensitive to changes in “angle of attack.” It could be feathered easily, then generate lift with just the slightest pull on the wishbone. At speed, the wing seemed to have a narrow “sweet spot,” and the rider could dump power very quickly. This made gusts easy to handle, and was predicted in Mark’s article. His data showed the L/D curve for a double-sided sail to be narrow. The single-sided conventional sail has a flatter L/D curve, and is not as sensitive to small changes in the angle of attack.

2. The wing was much stiffer than a standard rig. There was no “give” during gusts or when pumping. Twist was not excessive, and the trailing edge (leech) was stable and did not flutter.

3. The double surface section responded to air loads very nicely. The deformed shape looked like a “real” airfoil, and could be controlled without out haul tension. Due to the stiffness of the wing, the out haul had to be quite loose to develop the proper amount of camber for this wind condition. This made the wishbone feel sloppy, but did not cause control problems.

4. Speed was only slightly less than other similar wind surfers. During gusts the boat accelerated well, and matched speed with other boats. The general feeling was that our boat was performing well for such a small sail and light wind. Twenty-five knots winds, or a 60 sq. ft. sail,` would have been ideal.

5. The rig floated high in the water and was easy to up haul. We didn’t attempt any water starts, but the wing lifted well, and beach starts were easy.

Undesirable features:

1. The sail area was too small for the wind condition, and we had no easy way to increase it. With the advantage of hindsight, I would design the upper three feet to be removable. A larger than normal sail might work with a wing sail, since it luffs cleanly and very quickly. This would help under strong wind conditions.

2. With the out haul loose for more power, the wishbone felt sloppy. A “slip joint” out haul would hold the wishbone firmly, and still allow for camber adjustment. A one-to-one purchase is adequate, since the wing sail is so rigid.

3. When the wing was dropped, the rigid foot area hit the side of the board. Unlike cloth, the fiberglass would not give, so the foot of the sail ripped about 12 inches. This let water into the center section, but the damage did not get any worse, or effect performance. The foot section needs to be heavier, and padded like most goosenecks.

4. Thirty six pounds is a little too heavy. Using a foam core leading edge and thinner laminates could save five pounds, maybe more. On a larger boat, the extra weight may be offset since halyards, shrouds, turnbuckles, and chain plates are not needed.

5. Visibility behind the wing is poor. Clear windows could be stitched or laced into the sail.

I think these tests show that the basic concept is sound, and practical for some applications. Thick, well shaped, double surface airfoils are more efficient than cloth sails. Composite materials can be designed to deform into a smooth aerodynamic shape under air loads, without complicated flaps, hinges, and control lines. The bending and torsional stiffness in the leading edge is very high, and a free-standing rig is a definite possibility for larger sailboats. The design has a lot of potential for ice boats, sand sailors, and very high speed sailboats.

The design of a wingsail

Application of a holistic design optimization methodology

A wingsail is an aerodynamic structure analogous to an airplane wing, fitted to a marine vessel in place of a traditional sail. Over the past decade wingsails have become more and more popular among sailboat designers, owners, and skippers, due to their ease of use and control, but most importantly, for their advanced efficiency, compared to the traditional sail.

In this project Optiphore used design optimization and Computational Fluid Dynamics (CFD) technics to investigate the aerodynamic performance of two types of wingsail that can substitute the existing traditional sail of a sailboat. The first, a rigid single-component wingsail geometry, with variable chord length and varying airfoil geometry. The second, a flexible single-component wingsail geometry with variable chord length, varying airfoil geometry, and twist.

While new sailboats can be designed from scratch with a wingsail configuration, in this case the goal was to find an appropriate geometry that could also be retrofitted on an existing sailboat, producing equivalent sail characteristics by roughly maintaining the existing centers of gravity and effort respectively. Therefore, while the developed design methodology is generic and can be applied to a plethora of sailboat models, the end-result is a custom wingsail geometry, designed specifically for the needs of a certain sailboat model.

The applied strategy for obtaining a wingsail geometry is divided into two parts. In the first part a proprietary evolutionary algorithm is used to generate airfoil sections at various wingfoil spans, taking into account the wind’s speed and the airfoil’s angle of attack at each wingsail span. Every airfoil is described with an appropriate parametric, mathematical representation and subsequently, a panel-method software is employed to evaluate the airfoils’ lift-to-drag ratio. This is a versatile approach that can produce optimal product design solutions by exploring among a huge number of feasible designs, inside a given design space. It can be coupled with any type of third-party software to evaluate the validity of all the different design variable combinations it explores, promoting optimal solutions as result.

In the case of both the rigid and the flexible wingsail types, each airfoil section is submitted to a different wind velocity, based on its wingsail span location, to conform for the wind's velocity profile. In the case of the rigid wingsail, all airfoils have the same angle of attack, as a rigid wingsail cannot support a twist. In the case of a flexible wingsail a linear twist is applied to reduce its induced drag, with the angle of attack at the tip equal to zero.

In the second part of the utilized strategy, the 2D airfoil sections are used to produce the wingsail’s 3D geometry. At a first glance, any unexpected features of the wingsail shape can be identified, so the 2D analysis of specific sections can be performed again. A CFD analysis of the resulting shape can provide insight about any three-dimensional phenomena that occur on the wingsail, which cannot be identified with a 2D analysis. Moreover, its overall performance can be assessed at this point, by calculating the lift-to-drag ratio of the 3D shape and validating that the resulting shape is appropriate for the sailboat's needs.

Optiphore offers a comprehensive design optimization methodology. Starting with a blank canvas and a set of design requirements, a number of ideas get produced with the help of our proprietary design exploration tools. Those ideas can be evaluated often at a reduced computational cost. Eventually, the performance of the most promising ones is thoroughly evaluated to converge to the final design. Most product development design cycles can greatly benefit from such an approach.

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Airfoil Selection and Wingsail Design for an Autonomous Sailboat

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• First Online: 20 November 2019
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• Manuel F. Silva 19 , 20 ,
• Benedita Malheiro 19 , 20 ,
• Pedro Guedes 19 &
• Paulo Ferreira 19  

Part of the book series: Advances in Intelligent Systems and Computing ((AISC,volume 1092))

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Ocean exploration and monitoring with autonomous platforms can provide researchers and decision makers with valuable data, trends and insights into the largest ecosystem on Earth. Regardless of the recognition of the importance of such platforms in this scenario, their design and development remains an open challenge. In particular, energy efficiency, control and robustness are major concerns with implications in terms of autonomy and sustainability. Wingsails allow autonomous boats to navigate with increased autonomy, due to lower power consumption, and greater robustness, due to simpler control. Within the scope of a project that addresses the design, development and deployment of a rigid wing autonomous sailboat to perform long term missions in the ocean, this paper summarises the general principles for airfoil selection and wingsail design in robotic sailing, and are given some insights on how these aspects influence the autonomous sailboat being developed by the authors.

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This work was partially financed by National Funds through the Portuguese funding agency, Fundação para a Ciência e a Tecnologia (FCT), within project UID/EEA/50014/2019.

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Manuel F. Silva, Benedita Malheiro, Pedro Guedes & Paulo Ferreira

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Silva, M.F., Malheiro, B., Guedes, P., Ferreira, P. (2020). Airfoil Selection and Wingsail Design for an Autonomous Sailboat. In: Silva, M., Luís Lima, J., Reis, L., Sanfeliu, A., Tardioli, D. (eds) Robot 2019: Fourth Iberian Robotics Conference. ROBOT 2019. Advances in Intelligent Systems and Computing, vol 1092. Springer, Cham. https://doi.org/10.1007/978-3-030-35990-4_25

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Wiktionary.org offers this defintion of the word vang .

Although the etymology is all very interesting. The latter is the one we are the most interested in. Below is a good video describing the benefits of the boom vang and when to use it.

[youtube https://www.youtube.com/watch?v=C31nGzO54O4&w=560&h=315]

The Boom Vang , in its simplest form, is a block and tackle arranged in such a fashion that it applies downward force (also upward force, see rigid vang) to the boom. This will allow the sailor to control the tension of the leech at all points of sail, regardless of the boom’s sheet tension.

RIGID VANGS – Most modern day cruisers and racers alike will use a version of this called a rigid vang. A rigid vang, a.k.a. hard vang, or boom kicker, gets its name because it not only is able to haul the boom down but also pushes it up. This is very handy for a few reasons. The ‘main’ reason (pun intended) is it allows the user a quick way to de-power the booms sail if needed and also helps to support the boom much like a boom topping lift. The last part makes reefing, dousing and storing of the boom all a bit easier.

In taking a look at who’s making these rigid vang systems we find no shortage in manufacturers:  Boom Kicker , Barton Boom Strut , Bamar Rigid Vang , US Spars/Z Spar Vang , Selden Rod Kicker , Hall Spars Quick Vang , Vang Master , Forespar Yacht Rod , and  Sparcraft Vang . Those are just the mechanical vang makers of the world (and I’m sure I’ve missed some).

On the hydraulic end of things, there are far less manufacturers. If your boat is already equipped with a hydraulic system of any kind you’ll likely recognize one of these brands:  Navtec , Sailtec , Selden , and  Harken , which are all makers of high quality hydraulic systems…including vangs.

Let us just focus on the ones that we know best and sell the most of here at The Rigging Company!

Forespar Yacht Rod  is a tried and true system and our most popular model yet. It may not be the lightest or sleekest out there, but this vang has earned it’s rank among one of the most dependable in the rigid vang market. It is well suited for just about any racer/cruiser or dedicated cruising boat out there. The yacht rod uses a dependable coil spring as the return. Forespar vangs are adjustable, utilizing a very coarse adjustment (about every 4″) via a fast pin which allows the user a tool-less way to adjust the spring pre-load or boom kick height. The vang is constructed of one smaller anodized aluminum tube and one larger painted aluminum tube with cast anodized ends. Pricing is around the $870 – $1600 range, and they are available in just 3 different sizes. Mast brackets, block and tackles, boom lugs, all sold separately.

Hall Spars Quick Vang  has also been around for a long time. Although Hall USA has recently announced its closing of business , I think shoppers will still find an inventory of these super high quality vangs with various distributors throughout the US. The Hall Spars Quick Vang has always had a great reputation, and their most recent iteration is even better. Typically, this vang is found on racer/cruisers and dedicated racing boats. Although there is no reason this couldn’t be found on a cruising boat in my opinion. This vang also offers a coil spring as the return mechanism. The springs pre-load can be finely adjusted to set the boom’s kick height (hex keys required). It consists of completely anodized aircraft grade aluminum tubing with solid aluminum machined ends. These systems can vary in price from $1000 to $2800 and are available in 7 different sizes/configurations. Purchase block and tackles are always included, varying from 8:1 to 60:1 depending on boat size and sail requirements. As with all of these systems, mast brackets and boom lugs are purchased separately.

Selden Rodkicker  vangs have also been around a very long time and are rigged on many different styles of boats. It is likely they are equipped on more boats than any of the other manufacturers, from the club racer/cruiser, to the dedicated match racer, to the varying ranges of production cruising boats found in today’s sailboat market. Selden’s approach is slightly different in that it uses a gas spring (much like your gas strut on your hatchback) as the return. They also use a very attractive rectangular extrusion instead round tubing like Forespar and Hall. Selden’s Rodkicker vang does not offer any spring height adjustment. The ends are made of cast anodized aluminum (like Forespar). Price wise these are some of the most affordable systems on the market, ranging from just under $300 up to $1600 (hence their popularity). The Selden vangs come in 4 different sizes, and offer a soft and hard spring option within each size (they also offer the no spring option, but what’s the point? ). Purchase block and tackles, mast and boom brackets must be bought separately.

Hydraulic Vangs – Amongst the various hydraulic vang manufacturers you will see very similar design, functionality, and construction. It seems that Navtec, who also recently closed their doors , was the grandfather of all sailboat hydraulic system and cylinder design. The three big players left (see links at the top of this article) all have their own unique features and benefits, but are for the most part based on the same (Navtec) design. Whether we are talking about a double acting push pull vangs (reserved primarily for larger yachts with heavy booms) or gas return vangs, the gist is the same. There is a stainless steel piston rod with an aluminum piston that rides inside of an anodized aluminum cylinder/body. This is all accompanied by a series of seals that will need to be serviced/replaced once in while to keep things….sealed. The big deal is that all of these hydraulic vangs require the boat to be plumbed with hoses, a reservoir and a control panel that houses the pressure gauge and pump at a minimum. Besides just a basic vang cylinder (no plumbing, brackets, lugs or panels) costing as much as the most expensive mechanical vang mentioned above, these systems HAVE to be professionally installed thus making them the most expensive, but also the most robust option, by far.

~Some Final Thoughts~

All rigid vangs especially when properly installed and maintained will last a very (very) long time. Keep in mind, typically anything using fluid (and or gas) and seals will require service/ repair over time. One thing that all vangs require, regardless of whether choosing a simple block and tackle, mechanical, or hydraulic system, is for them to be installed properly; ensuring a properly mounted mast bracket and boom lug, rigging the vang in the correct orientation (not upside down), all the while achieving the appropriate boom to vang angle (approximately 30-45 degrees). This will ensure functionality, longevity and ease of use.

Have a question about which system might be right for you? Need your hydraulic vang serviced? Talk to our experienced sales staff for more information.

Thanks for the read. See you next time.

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Hi, I am chasing a vang for my Cape 35 that supports the boom. Eye to eye for the band is 1700mm. Cheers, John.

We’d be glad to help. Any vang from any of the manufacturers listed in the article should work. Although some have different pin to pin measurements, most are adjustable, and are about the same for the given size unit. Can you send us pictures of what you have now for a boom and a mast attachment? Email [email protected] . Is there a specific manufacturer that you might prefer based on the article? Let us know in an email and we can set you up a complete DIY solution with instructions after we answer a few questions.

Thanks for Choosing…

Greetings, looking for a Hall Spars cast aluminum vang boom lug to replace mine which deformed and failed. It attaches to the underside of the boom with eight 5/16″ machine screws. Older model which came with a 1988 Sabre 38 MkII. Thank you.

Hey Carter, Thanks for contacting us, it took me a while and we’re super busy, but I have some info….

For the boom portion there are still parts available. Pricing is coming your way, but first let me know which on you need the externally mounted one one internally mounted one.

Use [email protected] to let us know which you would like and we’ll will get pricing and ship one out to you.

Thanks and We Hope that Helps, ~T.R.C.

Hi there, thanks for the reply. It’s an external lug with 8 fasteners. Here’s a photo:

https://www.dropbox.com/s/uicq8ctizs3eoyg/20180603_172037.jpg?dl=0

$219 in stock. Give us a call and we’ll get one shipped to you.

I am trouble shooting a Navtec boom vang. Vang does not pressurize. Trying to determine if the cylinder seals need replacing or the actual vang seals.

My advice is that if the cylinder is not holding pressure, you just re-build the entire unit and re-charge the return. Then we test the unit overnight. There are complete seal kits available for this. We recommend professional certified service to do this. Please let us know if we can help further.

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I slip it onto a Sunfish mast; a 2.25" diameter by 10' aluminum tube. Three sets of mast holes were drilled into the ribs, one at the center of pressure (lift) and 2 on either side for experimental purposes. Three feet of duck-under room was created by plywood doubling the appropriate rib hole for the mast to rest and pivot on. No downhaul was used. This is a nine pound wing for those concerned about leverage moment arms and tipping. Theoretically, the airfoil will have less air drag than the plain round mast, so allowing it to weather-vane should prevent most tip-over worries.

Twenty-four ribs were easily made in half a day. Slots were made in each for a pair of 1" x 0.25" x 10' pine stringers by drilling three 0.25" holes side by side, then cleaned up using a 10" mill bastard file. The ribs were then strung six inches apart and bonded with Gorilla glue. The location of the stringers isn't critical. In hindsight, the ribs could have been spaced a foot or more apart, allowing for a slightly lighter structure, and a faster build. A 1/16" plywood "X" shaped stub mast (main spar) supports the section above the aluminum mast in one of the alternate sets of mast holes.

If I have lost you, just look at the pictures. It's far from rocket science. The leading (LE) and trailing (TE) edges are simply Duck TapeT ala Mythbusters. Try to keep the surfaces smooth. Three overlapping strips on the LE, and one on each side of the TE is enough. The covering material came from 2 large packages of 3M heat shrink window insulation film. That's another $15. It was attached to the four outer edges using 2" wide clear packing tape. I bought extra double sided tape to stick the film to every rib as well. (On Piper Cubs, the fabric covering is sewn to each rib.) The strings in the pictures mimic airplane drag/anti-drag wires. I was hoping to reduce any twist and assure that all the bits would stay together in a catastrophic failure. It wasn't worth the bother. The wing is now complete except for some spiffy colored and checkerboard tape, and number decals. Looking cool is 50% of the effort.

I transported the wing to the lake on top of my Uncle Johns Skiff in the back of my pickup. The wind plasters it down to the boat gunwales and it rides along at highway speeds just fine. Two people are required to hang onto it though once at the boat ramp and exposed to the wind. It's a handful. Keep it pointed edge into the wind because it wants to fly. The mast is slid into the bottom rib until it hits the stop rib. Then by keeping the top of the wing facing into the wind, and allowing it to weather-vane as it is brought to vertical, it can be stepped into the boat. Do this when no one is looking.

The first day I tested the wing, there was no wind and I simply drifted into the middle of the lake. The second day I tried it, there was too much wind and a gust pick up the boat and knocked it over on the launch ramp, a testament to the strength of my mast step and dispelling the "less drag then the bare mast" theory. The third day, a tornado damaged my house. Fearful of any fourth attempt, I dry sailed it a couple times on the front lawn. Contrary to the extreme flimsiness, there is absolutely no twisting in any amount of wind. And as far as strength, I have yet to accidentally puncture the skin or break any internal bits & pieces, even after the wind tried to double it in half a couple times while off the mast.

I finally found a decent 6-8 mph wind day on a 2,400 acre oxbow lake that is silting in at 4 feet deep (great waves though). After rowing out, I attached a sheet to both ends of the bottom rib for control. There is no conventional 'feel' to a wing sail, so the only way to point it is to watch a wind vane attached to the stub mast. The wind vane rocked with the boat and wasn't a lot of help. The wing also had a tendency to flop long its center of gravity if both sheets were not held firm. I haven't tried the mast in one of the alternate holes yet. But once pointed into a direction that moved the boat (speed measured by calendar, not GPS), some conventional handling pressure could be felt.

Unfortunately for aerodynamic theory, the wing was at a negative angle of incidence when propelling the boat! The NACA 0012 generates lift between just 12 and 15 degrees to the apparent wind, not much margin. So as a rigid sailboat sail, it's the wrong airfoil without adding lift devices (flaps, slats, slots, jibs, etc.). Once we put on the usual Sunfish Mach II lateen sail, we rocketed up and down the lake at a blistering 2.5 to 5 knots like always (eighth season sailing this fun flatiron skiff).

At this point, I'll probably let my son try to hang-glide it off a small hill. I sailed on Dennis Conner's Stars & Stripes 12 meter yacht (#56) in Cozumel Mexico last fall. I learned that when the wind isn't blowing, all sailboats handle exactly the same. The rigid wing sail is no exception, but it looks a whole lot cooler than a conventional polytarp sail!

Phil Frohne

Uncle Johns Skiff, 1974 Chrysler Buccaneer, Catyak

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The Pros and Cons of the Rigid, Fiberglass Dinghy

Dinghies are the Rodney Dangerfields of cruising. They get no respect, or at least not as much as they deserve. The little boat that will see nearly as many sea miles as the mother ship is often an afterthought.

Inflatables, and rigid inflatable boats (RIBs), hybrid craft with inflatable tubes and rigid (usually fiberglass) bottoms, have been the norm for years. I recognize the virtues of the RIB design, but when it comes to full time cruising, my allegiance remains with the hard dinghy camp. A hard dinghy is virtually indestructible compared to an inflatable or RIB. Its economical, and its always ready to deploy.

There are almost just as many reasons why hard dinghies are the wrong solution. They are harder to stow, hard on topside paint, relatively unstable, and require more patience when getting from here to there.

If youre an avid diver or surfer, like to explore, or prefer anchoring away from the crowd, having a RIB or inflatable with a turn of speed will be essential. Having that extra umph also comes in handy when setting kedges, playing tugboat, or rushing to help a neighboring boat whose anchor has begun to drag.

Ultimately, our dinghy preferences reflect our philosophies toward cruising. The romantic drawn to the idea of self-sufficiency (the kind of person who rides a bike to work), will be inclined toward a rugged hard dinghy that rows easily and requires virtually no maintenance. The pragmatic RIB aficionado will recognize that having fast transportation is worth the hassles associated with an internal combustion engine.

Years have past since our last head-to-head dinghy tests (see PS November 2009, and October 2008). Both focused on inflatables. Since then, there hasn’t been any significant advances in inflatables, but we have seen some interesting developments in hard dinghies.

A few years ago, West Coast designer Russell Brown came out with a kit for the PT11, a dinghy comprising two parts that nest inside each other. And the carbon-fiber Wing Dinghy, which we compared to the popular Trinka in October 2009, is so light that one person can easily load and stow it.

Since the wide introduction of the mass produced Walker Bay 8-a sluggish rower with a durable thermo-molded PVC hull-the more traditional fiberglass dinghies have been pushed to the fringes of the market. The familiar names-Bauer, Fatty Knees, Pelican, Trinka, Dyer, Gig Harbor-are still around, but the prices ($6,000 for a sailing Dyer) make an upwind slog in $600 Walker Bay 8 seem more tolerable. Kit boats like Browns PT11 or those from Chesapeake Light Craft offer a cheaper path to a hard dinghy. It requires an investment in time, but the experience gained building your own dinghy can be more valuable than the boat itself.

As we begin another round of dinghy testing, wed be interested in hearing from readers. How long have you had it? What problems have you had? And where the heck do you stow the thing? You can contact me at [email protected] .

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These 150-foot-high sails could help solve shipping’s climate problem

Harnessing the power of wind could both reduce emissions from cargo ships and extend the life of these vessels.

A previous version of this article said Norsepower's rotor sails typically help ships save 8 to 10 percent on fuel. Those numbers came from one trial onboard the Maersk Pelican; the company says a better estimate for typical fuel savings across all ships is 5 to 25 percent. The article has been corrected.

To cut costs and carbon emissions, cargo ships are putting a new spin on an ancient technology: the sail.

These aren’t the sailboats of yore. Modern sails look more like airplane wings, smokestacks or balloons, and they use artificial intelligence to catch the wind with little help from mariners who long ago forgot the art of hoisting a mainsail.

Sails can reduce an existing ship’s fuel consumption — and greenhouse emissions — by something like 10 or 20 percent, according to maritime experts, making them an attractive option for ship owners looking to cut costs or comply with environmental regulations.

Ships burn some of the world’s dirtiest fuels and generate roughly 3 percent of global emissions, a share that’s only expected to rise over time , according to the United Nations. The European Union created a cap-and-trade system for shipping emissions earlier this year, and the U.N. International Maritime Organization is finalizing its own emissions rules now that would penalize the owners of dirty vessels.

Rather than sending those dirty vessels to the scrapyard, companies can install sails to clean up some of their emissions and extend their ships’ lives. And as the industry eventually moves toward alternative fuels that are low-carbon but high-cost, saving money on fuel will become even more important.

There are now 39 large commercial ships with sails, according to the International Windship Association, an industry group that represents sailmakers, ship owners and ship designers. That’s a drop in the bucket compared with the roughly 100,000 cargo ships plying the seas , but the technology seems poised to take off as sails move from test projects to real-world use. Sailmakers are building new factories to meet the expected demand.

“We’re at an inflection point,” said Matthew Collette, a professor of naval architecture and marine engineering at the University of Michigan. “We’re going to see this coming very quickly to a larger number of ships.”

Here are some of the strange sails that may one day push your online orders across the seas.

Ships with wings

One of the most versatile sail designs looks and works a lot like an airplane wing.

“All we’ve done is taken that wing and put it vertically,” said John Cooper, CEO of BAR Technologies, a company that manufactures this type of sail, “so instead of creating lift, we’re creating thrust.”

On an airplane, wind flows over the wings and creates air pressure differences that push the plane up. On a ship, the wings work the same way — except they’re angled to push the ship forward.

The wings come with sensors that measure weather conditions, and they automatically change their angle and shape to catch the wind. These sails can typically be used for most of a voyage, but they fold down to the deck if the wind blows faster than 30 knots, or when the ship is docking or loading cargo.

Last year, BAR Technologies installed two of its wings on a 43,000-ton ship designed to carry dry bulk cargo such as grains, coal or minerals. Over its first six months, the ship saved 14 percent on fuel as it crisscrossed the Atlantic, Pacific and Indian oceans, according to the ship’s owner.

The return of the rotor sail

At first glance, rotor sails may look like smokestacks rising from the deck, but they’re actually tall, rotating cylinders that use wind to push a ship forward.

When the wind is blowing at the right angle, an electrical motor spins the rotor sails, speeding up the air flow on one side of the sail and slowing it down on the other. That creates an air pressure difference that pushes the ship forward.

Norsepower, the biggest rotor sail manufacturer, says they typically help ships save 5 to 25 percent on fuel.

Rotor sails are more than a century old; German inventor Anton Flettner patented the idea in 1922 and an experimental cargo ship fitted with rotor sails crossed the Atlantic in 1926. But Norsepower, which is based in Finland, says the sails have come a long way since then, thanks to lightweight composite materials and AI systems that adjust to the wind to make the sails more efficient.

“We can make a much better sail than Mr. Flettner did in the 1920s,” said Tuomas Riski, Norsepower’s CEO.

The Michelin Man sail

Michelin is developing a more experimental inflatable sail which, appropriately, looks a lot like the company’s mascot.

Michelin’s design works similarly to a classic sail, made to catch the wind and redirect its power forward. The main difference is that its sail is made of inflatable fabric instead of a canvas sheet, and its mast can retract down to the deck. The sail can change its size depending on wind conditions.

Like the other sails, Michelin’s product operates by itself. “It has to be fully automated because today’s sailors have no time and no particular knowledge about sails,” said Gildas Quemeneur, who is leading the project.

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You need a dinghy; why not one that can save your life?

You’re free to have fun on the water when you, your family, and your crew are safe. Portland Pudgy, Inc has re-imagined the dinghy in the context of safety at sea, and come up with something really new. A rugged, unsinkable dinghy you can row, motor, sail , and even use as a lifeboat. The Portland Pudgy safety dinghy makes boating even more fun, by making it safer.

The sail kit makes your Portland Pudgy a fun, safe sailing dinghy. The stability and buoyancy designed into the Portland Pudgy make it safe and sea-friendly as a recreational sailing dinghy for the whole family. The Pudgy takes surprisingly rugged seas and wind for a boat its size…

The Portland Pudgy is a rugged, unsinkable self-rescue boat, even without the inflatable exposure canopy and other survival gear. With the canopy and sail, the Portland Pudgy is a dynamic lifeboat. Unlike inflatable life rafts, the Pudgy can’t deflate, and you can sail, row, or motor to safety…

What is the Portland Pudgy safety dinghy?

The Portland Pudgy is a multifunction boat that was designed as a yacht tender and unsinkable, dynamic lifeboat for blue water sailors that can be sailed to safety. The resulting stability, buoyancy, ruggedness, roominess, and “unsinkability” designed into the Portland Pudgy make it unparalleled as an everyday tender, a safe and sea-friendly sailing dinghy, and a great all-around rowboat/motorboat. The Pudgy is a self-contained unit: all accessories, including the oars, sail kit, and exposure canopy, stow within the storage space in double hull of the boat with room to spare.

Recreational Small Boat for Sailing, Fishing, Hunting, Diving

Unlike inflatable boats, the Portland Pudgy safety dinghy is a joy to row. It can be rigged out as a fun sailing dinghy. It’s a safe and fun recreational sailing dinghy for the whole family. It’s stable and difficult to capsize, but if you manage to, it’s very easy to right, and comes up dry. No need to wait for rescue (as with some recreational sailing dinghies, like the Opti). The entire sail kit stows neatly out of the way in the interior of the double hull (rudder and leeboards under seats). Because the Portland Pudgy safety dinghy is so stable, rugged, and tracks so well when rowed or motored, it’s also a great fishing boat or duck hunting boat, and a great platform for nature photography and diving. See Sailing Dinghy.

Self-Contained Unit

All of the accessories, oars, sail kit (including telescoping mast and boom), inflatable exposure canopy, sea anchor, ditch bag, provisions, and more, can be stowed within the boat via the five watertight hatches.  This is very convenient in your everyday dinghy or sailing dink.  It’s an extremely important safety feature of the Portland Pudgy lifeboat. All of your equipment is there in an emergency.

Dynamic Lifeboat

The Portland Pudgy safety dinghy is a self-rescue boat, even without the optional inflatable exposure canopy and other survival gear. With the exposure canopy, sea anchor, and sail kit, the Portland Pudgy is an unsinkable, dynamic lifeboat. Unlike inflatable life rafts, the Pudgy cannot deflate, and you can sail, row, or motor this rugged self-rescue boat to shipping lanes or land.

Everyday Yacht Tender, Rowboat, Motorboat, Rugged Workboat

The Portland Pudgy safety dinghy is the safest, most rugged yacht tender on the market to row, motor, tow and carry. It tracks perfectly and moves along nicely with a small motor. The Pudgy is extremely buoyant and has huge carrying capacity, both in the roomy cockpit and inside the storage compartments in the double hull. The Portland Pudgy (7′ 8″, 128 lb., USCG-approved as a rowboat and motorboat for 4 people) is designed and manufactured (in the USA) to be an exceptionally rugged, stable, unsinkable boat. Its pram shape allows it to fit on the deck of many cruising sailboats. This small boat is so stable you can stand up and walk around in it. The Portland Pudgy safety dinghy has all the benefits of inflatable boats and RIBs (rigid inflatable boats), without the risk of deflation. There is no need for an unsightly, expensive, and deflation-prone RID kit (“dinghy dogs”) with the Pudgy: it’s an unsinkable boat, with built-in buoyancy. See Yacht Tender/Dinghy.

Live-aboards  Teresa Carey and Ben Erickson Carey  sent us this wonderful video about their Portland Pudgy. Lots of great sailing shots.  Deliberately flipping the Pudgy (:33) and then easily righting it (2:00). Inflating the exposure canopy using the alternative method (hand pump) and using it as a dodger (1:15). Sleeping in the Pudgy. Lots of shots that show how stable and roomy it is. And lots just showing what a fun little boat it is.

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