Overview: The Harbor Wing Technologies Wingsail

A WingSail That Is Efficient and Easy To Use

Over many years, the potential benefits of WingSails for modern sailing vessels have been studied and discussed. Throughout his career David Hubbard, a member of the Harbor Wing design team, has designed well-known and very successful “hand-controlled” versions deployed on extremely fast vessels such as the winged America’s Cup winner "Stars and Stripes"   [+] Read More

Both hard and soft variations of WingSails are currently utilized on some of the world’s most technologically advanced vessels. Dr. Gabriel Elkaim, one of Harbor Wing’s primary WingSail control developers, has devoted many years of research and development to the characteristics of wings verses sails, particularly with regard to Autonomous Unmanned Wind Powered Vessels. His conclusions:

"There are three main reasons to use a wing instead of a sail: 1) efficiency, 2) low actuation force, and 3) self-trimming (passive stability). A rigid wing can be far more efficient than a cloth sail, with a CLmax of 1.8 vs. 0.8, though attention needs to be paid to Reynolds number effects. The lift/drag L=D ratio of the wingsail section is in the 30–100 range, whereas the L=D of the conventional sail is in the 3–5 range. Further, a cloth sail suffers from aeroelastic collapse when pointed high into the wind (the sail is said to be luffing), which causes a substantial drag rise and effectively limits how high the boat can sail into the wind. A rigid wing, by contrast, suffers no aeroelastic problems; it can point straight into the wind with very little drag and no noise, effectively reefing the wing. The feathered wing–tail combination has less drag than the bare mast. This addresses the most common objection to rigid wingsails: the inability to reef the sail (or reduce the area)."

As Harbor Wing has been primarily involved in the development of Autonomous Vessels, we moved quickly into the use of hard WingSails because of their significant ease of control and size/power considerations. We have explored the WingSail’s overall performance and control characteristics and how they differ from conventional sail rigs. In fact, the differences are so great that they are virtually “apples and oranges”. In considering the performance, control and development advantages of the hard wing, we have abandoned the paradigm of conventional sail performance and handling. One outstanding example of the WingSail’s capability is that it enables the Harbor Wing X-1 vessel to come to a complete stop and then sail BACKWARDS with no change in real wind direction or speed.   [-] close

Uniquely Designed Control System Provides Unparalleled Safety

Since the Harbor Wing WingSail rotates 360 degrees it is effectively uncoupled from the vessel platform below it. Because the inertial forces of the vessel are uncoupled from the aeronautical forces of the sail plan, the Wingsail will instantly and efficiently regulate the power produced regardless of the course of the boat (except inside 20 degree true wind angle).   [+] Read More

The stability of a “normal” sailboat is heavily influenced by the course steered relative to sail trim, the trim of the sheets, position of the traveller and relationship between the trim of the headsail and mainsail. All of these impacts are eliminated with the automatic trimming provided by the WingSail. The Harbor Wing control system monitors wind strength, direction, and aeronautical loads produced by the WingSail at 5 times per second (5 Hz) real time. Vessel dynamics such as thrust and overturning moment are also monitored at 5 Hz real time. Potentially dangerous loads to the platform are eliminated before they are transmitted from the WingSail into the boat below it by near instantaneous changes in the tail airfoils’ angle of attack. As a backup safety system Harbor Wing uses an aviation inertial navigation unit (“INU”) which monitors the platform’s pitch, roll and yaw. The INU’s function is to automatically depower the WingSail if it detects unstable boat attitudes in 5 Hz real time. After years of development, testing and enhancing our product, we can proudly say that our WingSail can be applied to virtually any multi-hull sailing platform (mono-hulls will be referenced later ). We have discussed the merits of our system with some of the world’s foremost cruising catamaran builders such as John Robertson (Robertson & Caine) and Peter Johnstone (Gunboat). These builders are impressed with the concept of our Wingsail design created by the team of designers Hubbard, Melvin and Ott, and have expressed a readiness to work on appropriate potential projects with Harbor Wing Technologies in the future. Our Wingsail design has been written about in prestigious sailing issues such as “Sea Horse Magazine” and “Boats International”. Other publishers are interviewing Harbor Wing Technologies in order to present our product in more detail. It must be said at this point that Harbor Wing is NOT trying to replace, re-create, remake or rebuff the classic sailboat. In fact most of Harbor Wing’s developers, engineers, designers and even marketers are world class sailors with years of cruising, racing and navigating experience - including V70 RTW race and Americas Cup. Sailing a WingSail catamaran is meant to be different, somewhere between the classic sail and a motor-cruiser. We sincerely believe that there is a market for this type of technology and our company now provides for it.   [-] close

So with this introduction, we would like to provide answers to some of the most Frequently Asked Questions:

What is new here? Hasn’t this been done before?

The Harbor Wing system is a culmination of years of research, development, testing and refinement. The initial thing that is unique and new about the Harbor Wing system is that it is first and foremost designed for more control, more safety and greater reliability than ever before.   [+] Read More

This is not remote control or “fly-by-wire” but actually intended to be deployed for long periods of time without human intervention or direction. This has never been done before with a WingSail powered sailing vessel of any kind. For recreational applications, our patented twin tail controls introduce new and unique design elements.  Our “Wing-on-wing” design allows for the highest level of control ever applied to a WingSail system of any kind. At last, the practical application of highly controllable WingSail technology to popular and standard multi-hull vessel designs will be available to owners desiring the thrill, silence and environmental benefits of wind sailing combined with the ease of control usually associated with motorized vessels.   [-] close

What happens when the boat is docked or moored in heavy wind?

When the WingSail is “turned off”, the projected area that the wind encounters is less than what is presented by a traditional rig with shrouds, spreaders, etc., so there is actually less wind resistance than a normal sailboat.   [+] Read More

The WingSail is designed to feather passively with the electronics turned off so that both the upper and lower wing sections’ leading edges are in line with the corresponding tail sections’ leading edges. Because of the split wing design, the upper section will feather or weathervane independently from the lower section. By breaking up the leading edge span into two separate sections, a unique patent pending feature, the WingSail is prevented from producing lift in disturbed or dirty air due to typical harbor conditions. And because the WingSail twin tails do not rotate outside the beam of the vessel when moored, it can be tied to a dock or fit into a slip without problem. Harbor Wing’s WingSail has much less aerodynamic drag in this configuration than a traditional sailboat rig with a non-rotating mast, spreaders and all of the associated rigging.

Because our WingSail is symmetrical and perfectly balanced, it can swing freely in either direction and maintain a constant no-lift state regardless of wind speed or direction. We have observed this with our X-1 vessel in winds up to 50 knots while she was docked.   [-] close

How do you reef the WingSail?

The WingSail is built in upper and lower sections that are controlled independently. The top half can be de-powered or “turned off” if conditions dictate. This is all done automatically by the computer, without requiring any human intervention. Once depowered, the WingSail remains turned into the wind and has less resistance than a standard naked mast, reefed sail and rigging.   [+] Read More

Rigid WingSails and traditional cloth sails are as different as night and day. WingSails are capable of handling very high wind speeds as long as they are precisely controlled. A radical example of the capacity of wings to handle extreme winds is the 4,000 sq. ft. of wing on the B-52 Bomber that is subjected to air speeds in excess of 600 mph.

An experienced traditional sailor looks at the surface area of a WingSail and may become concerned about the large exposed area that does not “go away”. An aviator familiar with wings thinks differently. In fact, the size or area of the wing is not the issue.  The above example of the B-52 aircraft demonstrates that the real issue for the WingSail is control. As long as the WingSail is feathered into the wind without being allowed to gain an angle of attack it can ride out extreme winds without a problem.

While the vessel is underway, Harbor Wing’s WingSail control system monitors the WingSails’ position relative to the wind in 5Hz real time. When the wing is feathered, with the tails set to zero angle of attack, the wing adjusts automatically to oncoming shifts or changes in direction of the wind. This safety factor is enhanced by Harbor Wing’s important improvement in WingSail control by splitting the wing into an upper and lower section. This enables the WingSail to produce twist for increased propulsion efficiency. And by feathering the upper section first, which effectively reefs the upper half of the wing, drive is produced only with the lower half, thus reducing the overall thrust and overturning force.   [-] close

What makes the WingSail turn?

The WingSail system is 100% wind driven. The computer controls the “twin-tails” which in turn, create an angle of attack for the WingSail and cause lift to be created by the WingSail.   [+] Read More

The heart of the WingSail system lies in the control mechanics and processor. Our patented “twin-tail” system provides the wind management and directional settings for the main WingSail. The twin-tails are given their direction by the system computer which commands them as fast as need be through redundant marine electronic servos. This control amounts to the ability to constantly trim the WingSail and keep it exactly at the commanded angle of attack for desired course and speed. The WingSail itself is mounted on a stub axle assembly via 360 degree rotational bearings that allow the WingSail to swing freely in response to the twin-tails positions.   [-] close

What controls the WingSail angle of attack?

The unique and patented twin tail design is the key to generating lift.   [+] Read More

The rear-most airfoils, the twin-tails, control the larger forward airfoil sections. The tails are rotated by computer command to an angle of attack to the oncoming wind and produce an aerodynamic force which rotates the entire WingSail assembly in the counter direction. Once the WingSail is rotated, the wing has an angle of attack that generates lift. The computer constantly monitors the load generated by the wing and adjusts the twin tails to maintain the desired amount of thrust. Once the tails are set to a specific angle of attack, the WingSail assembly passively rotates without servo movement in response to wind shifts in order to maintain the same angle of attack.   [-] close

How do you trim the WingSail for varying top to bottom wind conditions?

As in the case when the sail needs to be reefed, the top section of the WingSail is controlled separately from the bottom section, so the WingSail can be trimmed for various wind conditions.   [+] Read More

We understand that a rigid single WingSail does not have the classic “twist” of a soft sail. In order to maintain better control of the wind gradient and take advantage of shaping to the wind, we have developed a patent pending “wing on wing” design. A close look at our WingSail reveals a horizontal split between top and bottom. Very noticeable are two sets of twin tails, one set for the top half of the WingSail and one set for the bottom half. The upper and lower sections have separate anemometer inputs in their leading edges, and the upper WingSail assembly is allowed to move independently of the lower assembly with 45 degrees of freedom. Therefore the two sections are allowed to twist in relation to each other and gain the most efficient angle of attack to the oncoming wind. In a simple fashion this mimics the twist that is known to be beneficial in shaping a soft traditional sail.     [-] close

There are no stays. How does the WingSail keep from breaking off in rough seas?

The hull structure and WingSail have been extensively engineered using high tech materials and techniques. Safety is the first concern.   [+] Read More

The WingSail has a non-rotating mast or, as we call it, a “stub axle” in its center section. This is a very robust tapering carbon fiber pole with a large diameter base. The WingSail sections are mounted to the stub axle on large low friction composite bearings. The mast is engineered using Finite Element Analysis with a healthy safety factor above the maximum possible loads the WingSail assembly could generate from wind and pitching moment in a heavy sea. To insure the greatest strength to weight ratio possible, it is fabricated in a high-technology autoclave. For additional durability, the mast is structurally reinforced where it is joined to the vessel itself.   [-] close

How well does the WingSail perform up and down wind?

In both cases, with the exception of very deep downwind angles, the WingSail is equal to or better than a soft sail, especially up wind.   [+] Read More

Every boat will have somewhat different sailing polars due to the many vessel platform hydrodynamic and weight variables. Generally speaking, upwind is where a WingSail shines, because it will not luff or change shape like cloth sail. Data has been consistently collected from our X-1 AUSV in varying conditions showing the WingSail going to weather at up to 20 deg. true wind direction before stall. Down wind jibing angles vary with wind strength from 150 deg. to 170 deg. true wind direction.   [-] close

How would you pilot a recreational catamaran with the WingSail system?

Piloting a Harbor Wing Technologies Wingsail catamaran is closer to piloting a powerboat than a sailboat. A “throttle” controls the power of the WingSail.   [+] Read More

You steer the boat the same way as any sailboat with a tiller or wheel. There will be a flat screen display and a single Morse type throttle control located in the helm station within the pilot’s reach.  The pilot moves the throttle forward for greater amounts of thrust from the WingSail and backward for reverse thrust or forward braking, while the middle or neutral position is WingSail off or feathered. The pilot can toggle the flat screen display between an engineering screen, a sailing polar screen or a graphic overhead current view of the position of the WingSail assembly. Autopilot and auxiliary engine controls are operated in their normal fashion. For maximum enjoyment or relaxation, the pilot can concentrate on steering the boat without constantly adjusting and trimming sails or worrying about when to go on deck to reef the sail plan.   [-] close

What happens if power or a computer fails?

The default state of the WingSail is the neutral or feathered position. For safety, the vessel is equipped with redundant power supplies and also with redundant voting computers, so a single component failure during operation will not cause the WingSail system to become unsafe or fail.   [+] Read More

In the event of a single power failure or a single computer problem, the wing will automatically default to the “off” or feathered position. The vessel will come to a stop and not run out of control. There are several steps that can occur after that:  

  1. With the boat stopped, the cause of the problem can be addressed. Once power is restored or the computer system is re-booted, the boat can go back to normal operation.
  2. If the primary systems cannot be restored, there is a totally independent backup system that is run manually. This system has an independent battery system that is charged by solar panel so it is not dependent on the ship’s power systems. The manual operation of the wing does require some knowledge of how to operate the twin tails, but with this easy-to-learn system, the boat can be sailed home without the computer.
  3. The final back up is to control the wing manually with block and tackle. The wing will be fitted with attachment points to make this simple and safe. Obviously, this is not the most efficient method of operation, but it is a “get home safe” fallback for the offshore sailor.

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Can WingSails be applied to Monohulls?

Altogether a topic for a lot of discussion, but the answer is most definitely yes.   [+] Read More

There are however, in our estimation, some limits. The WingSail is very powerful and Harbor Wing believes that the stability of the multi-hull is a more suitable application. One must also remember that the WingSail turns through 360 degrees and the beam of the multi-hull allows the wing to rotate within the footprint of the hull.   [-] close

What other applications are there for the Harbor Wing system?

We continue to explore the use of our WingSails on commercial multi-hulls such as ferries, and on fishing vessels as a supplemental form of wind propulsion for greater fuel-efficiency and endurance.