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1. Field of the Invention
The present invention relates generally to sailing vessels, and more particularly to unique designs for aerodynamic wingsails having lightweight sail clothes, support members, mast features, hardware assemblies, as well as operation and control components.
2. Description of the Prior Art
Since their invention over thousands of years ago, sailboats have evolved in a multitude of fascinating ways. Many of the design advances made during that time were practical in nature, such as improving safety and simplifying operation, while others were made specifically to increase boat speed. For example, the recently developed rigid wingsails used on the America's Cup catamarans have only increased speed, while compromising simplicity and safety.
U.S. Pat. No. 6,892,660 is entitled Furling Sail and Means For Turning Mast, and discloses a furling sail and particular hardware/ball bearing assembly for turning the mast. The sail is described as to be fully battened by several thin, spaced apart battens which are positioned about steep angles to the sail. The battens are made of fiberglass rods which are held in place by cord and threaded through a batten. The lower ends of the battens are free to rotate inside pockets. This patent teaches the use of a rotating mast and diagonal battens to improve the functionality of a sail. In contrast, the instant inventive wingsail is supported by rotating brackets on a mast that does not rotate. The '660 patent incorporates an A-frame to support the upper mast bearing, functioning as a fixed base supporting the mast. The inventive wingsail herein utilizes two movable struts to form a tilting triangular base that supports the mast.
U.S. Pat. No. 5,619,946 is entitled Sail Furling Device With Bearings To Permit Simultaneous Cable And Extrusion Rotation, and illustrates a furling device and a particular upper and lower bearing assembly which compensate for static and horizontal loads, and rotates both the luff extrusion and the sail cable wire.
U.S. Pat. No. 4,699,073 is entitled Spaced Double Surface Sail Constructions, and relates to a spaced double surface sail construction wherein a sail envelope has an inner open area between two spaced sail surfaces. The sail surfaces have spaced battens, and battens support strips support, space, and guide the center portion of the battens. A batten socket support strip supports and spaces the batten sockets along the mast, and permitting pivotal movement. This wingsail has battens that pivot on the mast and are moved from side to side within the wingsail surface and camber is only reversible, not adjustable.
U.S. Pat. No. 4,064,821 is entitled Variable Camber Wing Sail, which describes a wing sail having a variable camber and having a two (2) sided spaced apart sail structure, including a plurality of resiliently deformable struts for each side. The beam produces a cam action to bend the struts producing an airfoil configuration. The design utilizes dual sliding tracks on rotating masts supporting twin sails that form thick wingsail profiles. Unlike the inventive wingsail, the masts are the leading edges of these wingsails, and include a variable camber control device consisting of a rigid boom and two pulleys connected to a bracket on the mast that also supports flexible battens that extend from the mast to the trailing edge of the surface. In contrast, the battens in the inventive wingsail surround the mast, forming the leading edge of the surface forward of the mast.
However, none of the above-referenced patents or the prior art address the designs, components and/or operation of the instant aerodynamic wingsail, which constitutes a substantial improvement over the art. Furthering previous wingsail concepts, the invention described below combines the superior aerodynamic efficiency of wingsails with the safety and simplicity of the best modern technology, thereby creating a useful and beneficial advance in sailboat evolution.
It is therefore an objective of the present invention to provide an improved lightweight wingsail and vessel with custom designed components providing for superior aerodynamic performance.
It is yet another objective of the present invention to provide an improved lightweight wingsail and vessel which eliminates problems with prior designs and provides enhanced benefits for operation and control.
Finally, it is an objective of the present invention to provide to provide an improved lightweight wingsail and vessel which is cost effective and operationally efficient while incorporating the above mentioned objects and features.
Furthering previous wingsail concepts, the invention presented herein combines the superior aerodynamic efficiency of wingsails with safety and simplicity rivaling conventional sails, thereby creating a useful advance in sailboat evolution. The present inventions relate to aerodynamic wingsails comprising lightweight sail cloths that have integral internal tubular slots which contain flat batten strips which are resilient and made of carbon fiber or other spring like material such as plastic/metal composites, fiberglass or the like. To form dual surfaces for the “wing” sail, the surface is folded in half about its centerline creating the wing profile around the mast. Related novel hardware and components control the deployment and operation of the wingsail and vessel, as the engineering designs also include top and bottom bracket assemblies, camber control components, hinged arms, bearings, floatation blocks, and certain free standing mast applications (having no stays). A unique fundamental wingsail is also disclosed having minimal components and simplicity of operation.
The invention may be better understood by reference to the drawings in which:
Fundamental Wingsail
The fundamental design of an inventive wingsail 5 of the instant invention is shown in
The rotation of the wingsail 5 is controlled by a rope (not shown) attached to grommet 30, and can be tied around the rod 10 as well, that supports the trailing edge. The wingsail rotates freely in response to the wind unless there is tension on the rotation rope. Left free to rotate, it continually turns in the direction of the wind while creating minimal thrust from drag. Thrust is created as aerodynamic lift when the operator uses the rotation rope to pull the wingsail toward the wind. Releasing the rotation rope stops the thrust immediately. This simple on-off function is extremely intuitive and risk free, providing greater safety than previous sailing systems.
Folding the wingsail is also a simple operation, because the bow rod 10 straightens alongside mast 12 as soon as the tension is released, either by sliding a clamp downward or by bending the bow rod 10 to unhook the lower bracket 28 from the mast. This basic version of the quintessential wingsail can also be raised and lowered about the mast by sliding the bow rod up or down.
In addition to the novel safety advantages, this fundamental wingsail 5 is also substantially more efficient than conventional sails. The generally semi-circular shape creates the efficiency advantage of elliptical area distribution, which increases the lift to drag ratio by providing uniform pressure distribution without the need for specific contouring of the surface. This theoretical principle was discovered in the early 20th century by Ludwig Prandtl, the father of aerodynamics. Furthermore, unlike conventional sails, the instant wingsails can always be aligned to the wind for maximum thrust, even when sailing downwind. With conventional sailing rigs, the mast support wires prevent the sail from rotating toward the front of the boat and therefore limit downwind sailing to the inefficient regime of simply being pushed by the wind. To overcome that limitation, many sailboats raise additional sails when sailing downwind, while the instant invention provides comparable thrust from a single easily controlled wingsail. Furthermore, the increased lift to drag ratio of this design also minimizes the side pressure that causes sailboats to lean over.
The novel self-tensioning structure of wingsail 5 has the extraordinary physical characteristic of uniformly distributed tension. This rare attribute, known as distributed compliance, is a structural ideal that maximizes strength and stability without rigidity or high tension. This advantage does not exist with previous sail and wingsail designs, which are classified as lumped compliance devices because they concentrate tension on one or more points. Benefits of distributed compliance include self-stabilization, extreme reliability and safety.
3 Dimensional Morphing Wingsail
With reference to
It is also understood that the curvature and shape of the wingsail surfaces can be designed to be generally oval, circular, elliptical or otherwise depending on the design parameters of choice.
The rounded leading edge of the wingsail surface is tensioned vertically by connections to the curved, generally oval portions of top and bottom brackets 48 and 50, respectively (top and bottom brackets are further illustrated in detail and discussed below in conjunction with
Mast 36 includes a top pulley 56, and the two brackets 48, 50 are free to rotate 360 degrees about the mast. The oval top bracket 48 and wingsail surface 32 are raised and lowered with a halyard assembly and a rope 58 that runs over the mast top pulley and down to a pulley and cleat (or a winch) on bottom bracket 50. A clamp mounted on the mast just above the bottom bracket prevents it from sliding upward. The rod that supports the trailing edge of the wingsail has a central hinge 60 that protrudes through an opening in the surface when the wingsail is lowered. As the wingsail is raised, two rod sections 62 and 64 are forced into the arc shape by the vertical tension and the constraint formed by the arc of the wingsail surface 32, as particularly illustrated in
With reference to
An additional structural innovation provides the dimensional flexibility that creates the continuously adjustable, optimally curved and fully reversible airfoil profiles. Internal straps 66 that tension the wingsail surface inward must also allow the surface to move across the leading edge from one side of the wingsail to the other as the camber is changed. That horizontal movement has been made possible by a system of rings 70 and straps 66. Straps 66 move freely within rings 70 providing a corresponding enhancement, flexibility and movement of wingsail and its profile. Ring material can be a lightweight plastic, but preferably stainless steel, as the added weight improves the overall mass balance of the wingsail. The rings 70 interact with the straps to maintain the leading edge radius as cambering shifts the surface around the mast. The rings also serve as counterweights to assist in keeping the mass of the wing balanced about the mast. As shown in
With reference to
Like many sailing rigs, the alignment of the wingsail to the wind is controlled by a rope connected to the trailing edge. Unlike conventional single-surface sails, which are located completely behind the mast, the dual surfaces of this wingsail surround the mast and place it approximately 25% of the way from the leading edge to the trailing edge. This results from the geometric design of the top and bottom curved brackets and placement of the mast aperture therein. Locating the mast at that position within the wingsail cancels most of the turning force produced by wind, creating a ‘semi-balanced’ condition that greatly reduces the controlling force required to keep the wingsail optimally aligned with the wind. The turning force of the wind is so low that this wingsail may be controlled by simply holding the rotation rope directly, providing a more tactile feeling of the wind pressure than when pulleys are used. Nonetheless, rotation control pulleys or other devices may be necessary or preferred depending upon the specific application and individual preferences.
As with conventional sails, the natural tendency of the upper wingsail surface to twist away from the wind is aerodynamically beneficial because it compensates for the wind speed gradient, which varies wind speed in relation to height above the water. The gradually decreasing wind angle toward the top of the wingsail effectively evens out the pressure distribution, thereby improving efficiency.
Since the inventive wingsail rotates easily, it is desirable for its mass to be balanced about the mast to minimize rotation caused by boat movement. To avoid such unwanted movement, this wingsail design provides nearly neutral mass balance. Specifically, the strap rings, oval bracket sections and camber mechanism are located forward of the mast, while most of the wingsail surface and the bow are located behind the mast. Consequently, any remaining mass imbalance will be minimal and easily correctable with small balancing weights.
An additional inventive safety feature can be realized by mounting a form-fitted block of plastic foam to the underside of the top bracket within the surface. That flotation improves safety by resisting submersion when the boat is tipped on its side. An inventive alternate flotation material is a form-fitted inflatable plastic float that would replace the foam block, potentially saving weight, cost and storage space.
Camber Control System
A camber (curvature) control system, consisting of a plurality of pulleys and two ropes, provides detailed control of the airfoil camber. This continuous curvature adjustment enables the operator maximize thrust over a wide range of wind speeds.
Referring to
Mast clamps 91 can be utilized to selectively position the oval brackets about the mast.
Pulling the camber control rope 90 in either direction shifts the camber in that same direction because it turns both sections of stepped pulley 76. Smaller pulley 80 controls camber actuator rope 92, which runs through the guide pulleys 94 located on both sides of oval bracket 50 and connects to the trailing edge of the wingsail surface and upper bracket 48. The friction brake prevents the camber from changing until the control rope is pulled. Consequently, the camber control rope 90 never needs to be secured to maintain a setting.
The two lowest camber control pulleys 86, located next to the mast clamp, are mounted on a ring or rope that rotates freely around the mast. That rotational freedom avoids unwanted wing rotation that would otherwise be caused by pulling on the camber control rope. The ring achieves that benefit by allowing the active pulley to move directly in line between the mast and the operator as the rope is pulled.
The bracket, pulleys and control assemblies illustrated in
Mast Features
The wingsails described above are most effective when used on masts that are free-standing, meaning that they are not supported by stays, which are wires that connect the top of a conventional mast to the front and sides of the boat. The use of stays would prevent the highly advantageous 360 degree motion of the wingsail. Instead of stays, the mast may be inserted into a rigid structural socket for support. That socket could be part of the boat hull or it could be an additional structure.
With reference to
There are many advantages to this arrangement, including fewer parts than stayed sail rigs and the ability to easily tilt the mast down toward the rear of the boat for assembly and transport. In the preferred embodiment, the mast and struts are carbon fiber tubes; however other materials, such as fiberglass, aluminum or even bamboo may also be utilized. Since sliding clamp 106 vertically on mast socket 100 changes the fore and aft angle of the mast and wingsail, aerodynamic efficiency can be improved by optimizing that angle for variations in sailing conditions. Improved control of the fore and aft angle may be facilitated with the inventive solution of a crank and gear mechanism that raises and lowers the clamp on the mast socket.
There are substantial safety and performance benefits afforded by the 360 degree rotational freedom of this wingsail design. Since there are no stays to prevent it from turning in any direction, releasing the rotation rope always releases the power of the wind. This is vastly safer than rigs with stays, which can easily break when user error or a failed part allows the sail to swing freely. This design also eliminates the danger of overpowering, because excessive wind force is automatically released by the flexibility of the structure. Excessive wind can cause conventional sail rigs to break or the boat to capsize unless the operator quickly releases the sail and/or turns the boat into the wind.
Mast Canting
Additional aerodynamic advantages may be provided by the side to side tilting adjustment known as mast canting. Canting reduces the leaning and downward force of the wind by tilting the top of the wingsail toward the wind. The instant system depicted in
Trapezoidal Version Supported by Gaff and Boom
A trapezoidal version of the 3D wingsail can replace conventional sails on boats that have stayed masts. With reference to
The upper and lower oval brackets 48 and 50 incorporate grooves 49 and 51 to accommodate the drawstrings described earlier.
A flotation block 124 attached to the upper bracket 48 assists with righting a turned vessel.
The surface of the rectangular wingsail is pictured in
Despite many previous attempts to create a practical flexible wingsail, relatively few have ever been produced. The most significant differences between the current invention and previous designs are the means employed to support and control the wingsail surface and the mast.
The above inventions have been described and illustrated with the reference structure, components and functions. Modifications and variations thereof will occur to those of ordinary skill in the art, and it is intended such modifications and variations will be within the scope of the inventive subject matter.
This application claims priority from the Provisional Application, Ser. No. 61/971,791, filed on Mar. 28, 2014.
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Number | Date | Country | |
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Number | Date | Country | |
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61971791 | Mar 2014 | US |