Method and apparatus for reducing a heeling moment of a sailing vessel

Various embodiments of a sailing vessel are disclosed configured to reduce a heeling moment acting on the sailing vessel as a wind acts on a sail of the sailing vessel. Generally, a mast of the sailing vessel is allowed to cant to leeward, thus reducing the heeling moment.

BACKGROUND

Field of Use

The present application relates to the maritime industry. More specifically, the present application relates to sailing vessels.

Description of the Related Art

Sailing vessels universally have a heeling, or roll, moment applied to their hulls by virtue of an aerodynamic force generated by the vessels' sails, mast or wing (collectively, the “rig”) during the normal generation of thrust used to propel the vessel. This heeling moment must be resisted by the vessel or the vessel will simply roll over to the horizontal.

Monohull vessels generate a righting, or restoring, moment to resist the heeling moment by virtue of their hull shape and the arrangement of ballast such that the center of gravity (CG) of a monohull vessel is lower in the water than its center of buoyancy (CB), and the heeling moment produces some amount of roll in the vessel that separates the CG and CB laterally, thus forming a restoring moment.

Multihull sailing vessels generate righting moments by virtue of their arrangement of hulls and aerodynamic arrangement of their mast, sails, and/or wings. A multihull vessel generates a righting moment because the roll moment raises the CG above the CG when the vessel is at a rest position, which generates a restoring moment in conjunction with the CB.

The action of a monohull to resist a rolling moment is inherently safe and self-restoring because more roll moment (caused by stronger wind) generally generates a greater righting moment, but rolling the vessel and particularly the mast, sails, and/or wing actually reduces the rolling moment, as aerodynamic forces on the sails are reduced by a function of the roll angle, i.e., by approximately a cosine of the roll angle. Thus, a vessel generally reaches an equilibrium roll when the rolling moment equals the righting moment. If the wind increases, the vessel may roll further, but the equilibrium angle is always less than fully horizontal, thus ensuring the vessel will right itself with lessening wind speed, providing that the vessel doesn't take on water when rolled significantly.

On the other hand, a multihull vessel (i.e., a catamaran (2 hulls) or a trimaran (3 hulls)), will eventually reach a roll angle where it will continue rolling to full horizontal (i.e., capsize), even without wind forces. The angle at which the multihull vessel will capsize may be referred to as a “capsize angle” and means that the vessel will not right itself after the capsize angle is exceeded—obviously a catastrophic situation for either a manned or unmanned vessel.

It would be desirable, therefore, to design a new type of sailing vessel that reduces the heeling moment, especially for multihull vessels, so that sailing vessels may continue sailing in conditions that would normally roll a single hull vessel to extreme angles, or that would capsize a multihull vessel.

SUMMARY

The embodiments described herein relate to a sailing vessel configured to reduce a heeling moment acting on the sailing vessel as a wind acts on a sail of the sailing vessel. In one embodiment, a sailing vessel is described, comprising, a hull, a mast, a sail coupled to the mast, and means for allowing the mast to cant to port or to starboard in a leeward direction when a wind acts on the sail.

In another embodiment, a method for reducing a heeling moment acting on a sailing vessel is described, comprising automatically allowing a mast of the sailing vessel to cant in a leeward direction when a wind acts on a sail coupled to the mast, thus maintaining the sailing vessel at an angle with respect to an imaginary vertical axis of less than a maximum heeling angle.

DETAILED DESCRIPTION

The present application describes various embodiments of a sailing vessel that automatically rotates, or “cants”, its mast to reduce a heeling moment generated by wind acting upon the sails of the sailing vessel, while still providing a thrust component for propulsion. The concepts described herein are applicable to manned or unmanned monohull vessels, such as traditional sail boats, or multihull vessels, such as catamarans or trimarans. While the embodiments described herein are most useful for multihull vessels to avoid capsizing, they can also be used to reduce the roll, or heel, angle of monohull vessels in order to reduce extreme roll angles that are typically uncomfortable for those onboard. Generally, embodiments of the invention cause a mast to rotate “with the wind”, i.e., in a leeward direction, with respect to the deck of a sailing vessel, thereby reducing the rolling moment.

FIG.1is a perspective view of one embodiment of a sailing vessel100that reduces heeling moments caused in an embodiment where a mast is allowed to rotate to the port and to the starboard with respect to a deck of the sailing vessel. Shown is hull102, mast104, sail106, pivot assembly108and deck110. It should be understood that sailing vessel100is merely representative of a number of different sailing vessel configurations, and that the inventive concepts described herein are equally applicable to those other configurations. For example, other sailing vessels may utilize two or more sails, be larger or smaller than sailing vessel100as shown, comprise two or more hulls, outriggers, rigs that comprise a traditional mast and soft sails (as shown), a rigid wing, a mast and a semi-rigid wing, an inflatable wing, a wind turbine, etc.

Sailing vessel100, in one embodiment, is 30 feet long, 10 feet wide, comprising a displacement of 10,000 pounds. However, the inventive concepts described herein could be applied to other sailing vessels that are much smaller, or much larger, than these dimensions.

In one embodiment, sail106is constructed from a lightweight, substantially rigid material such as molded fiber composite material or aluminum alloy. In cross-section, sail106(sometimes referred to as a “wing” or “wingsail”) is preferably configured as an airfoil that generates propulsive force (analogous to upward “lift” of an aircraft wing, but in a generally horizontal direction) regardless of whether an angle of attack is to the right or left of the wind, suitable foil configurations being known to those skilled in the relevant art. In another embodiment, the sail is constructed from a lightweight, flexible material such as cloth, nylon, Dacron®, Spectra®, Dyneema®, mylar, carbon fiber, etc. In these embodiments, sail106may be partially or fully inflated by the flow and pressure of incident wind, i.e., when sail106is formed similar to a ram air hang glider or kite wing.

In prior art sailing vessels, the mast is either rigidly fixed to the hull or the mast may be mounted on a mechanism that allows a mast to rotate fore and aft, forming a “rake” angle that alters the position of an aerodynamic center and thus relates to the relationship between the aerodynamic forces and the hydrodynamic forces generated by the hull(s) and or keel(s). This aero/hydro balance is critical for sailing efficiency. In contrast, sailing vessel100comprises mast104that is allowed to rotate, or “cant”, towards a port side and to a starboard side of sailing vessel100when a wind acts upon sail106. The mast is prevented from falling over to the waterline via a mechanical energy storage mechanism, such as a spring, that will be explained in more detail later here. In other embodiments, a restraint could be used, such as a typical shroud system where two shrouds are coupled near/to a top portion of mast104and one shroud coupled to a port side of hull102and the other shroud coupled to a starboard side of hull102, where each shroud may be shortened or elongated by means of either a block and tackle system or a hydraulic ram, stopping mast104form falling to the waterline.

FIG.2illustrates an aft view of one embodiment of pivot assembly108, i.e., from the aft of sailing vessel100, showing one end of mast104pivotally mounted to a fixed hub200. An additional hub200is typically used on an opposing side of mast104, hidden from view inFIG.2. Both hubs200are fixedly coupled to base plate202or to deck110. It should be understood that the relative dimensions shown inFIG.2are not to scale.

Mast104is rotatably coupled to the hubs200via a fulcrum204, such as a rod, bolt, pin, etc. In this embodiment, mast104comprises a through hole bored at a distance from the end of mast104that allows the bottom of mast104to clear base plate202. Similarly, a hole is formed through hub200in alignment with the hole in mast104such that fulcrum202may pass through the hole in hub200, then the hole through mast104and finally through another hole formed through the second hub on the opposing side of mast104. Fulcrum204is typically held in place via fastening means206, such as a nut, cotter pin, retaining snap ring, etc. The combination of the hub(s)200, base plate202, fulcrum204and fastening means206may be referred to herein as a gimbal208. This configuration allows mast104to cant towards the port side of sailing vessel100when the wind acts upon sail106from the starboard side of sailing vessel100and to the starboard side of sailing vessel100when the wind acts upon sail106from the port side of sailing vessel100. “Cant”, as used herein, generally refers to a rotation of mast104in a leeward direction, either to port or to starboard, away from an imaginary vertical axis perpendicular to deck110.

Mast104is prevented from falling to the waterline by a mechanical energy storage means208, shown inFIG.2as a leaf spring. Mechanical energy storage means208does this by applying a righting moment to the mast in a windward direction while the mast is canted, thus limiting a cant angle of the mast with respect to a perpendicular axis extending from deck110. More generally, mechanical energy storage means208comprises one or more springs, gas struts, hydraulic rams, etc. that provide a counter-moment to mast104in order to keep it from falling to the waterline, and for determining how far mast104will cant, given various heeling moments. InFIG.2, the leaf spring is mounted at one end to base plate202on the starboard side of mast104, while a planar surface of the leaf spring rests against or near a surface of mast104. In some embodiments, a second leaf spring is used, mounted in a similar fashion on the opposing side of mast104, on the port side of mast104. When the wind blows upon sail106from the port side, a heeling moment is created against sailing vessel100, causing the entire sailing vessel100to roll to the starboard, which causes mast104to cant leeward (i.e., towards the starboard) at an angle from the perpendicular to deck110by the leaf spring. The mast of the rig is what causes the mast to cant and mechanical energy storage means208limits the cant angle by applying a righting moment to mast104. Generally, the cant angle automatically increases linearly with respect to the heeling moment as the wind speed increases.

While rotary assembly108is shown inFIG.2as a two-axis gimbal, i.e., a mechanism for allowing canting of mast104in the port and starboard directions only, in other embodiments, rotary assembly108may comprise a three-axis gimbal, as shown inFIG.3.FIG.3illustrates an aft, cutaway view of mast104mounted to base308, where an end300of mast104is formed into a “ball” and a reciprocating, receiving “socket”302is formed into base308. It should be understood that the relative dimensions shown inFIG.3are not to scale. In this configuration, mast104is free to rotate in the fore, aft, port and starboard directions, and any position therebetween. In this embodiment, mechanical energy storage means208comprises at least two springs, port spring304and starboard spring306. As the wind acts against sail106from the port side of sailing vessel100, generating a clockwise heeling moment on sailing vessel100, causing mast104to rotate clockwise under the weight of the rig, port spring304limits the range of cant of mast104and prevents mast104from falling to the horizontal on the starboard side of sailing vessel100by applying a righting moment to mast104. Conversely, as the wind acts against sail106from the starboard side of sailing vessel100, generating a counter-clockwise heeling moment on sailing vessel100, causing mast104to rotate counterclockwise under the weight of the rig, starboard spring306limits the range of cant of mast104and prevents mast104from falling to the horizontal on the port side of sailing vessel100.

The “stiffness” or spring constant of mechanical energy storage means208is an important design consideration, as it defines how much mast104is allowed to cant, given a range of heeling moments. The spring constant or stiffness may be chosen to automatically cant mast104leeward to a particular cant angle, given a maximum desirable heeling moment (in single-hull vessels) or maximum heeling angle (i.e., a capsize angle in multi-hull vessels). For example, when sailing vessel is rolled 30 degrees from the vertical by the wind, a spring constant or stiffness may be selected such that mast104cants 10 degrees. Allowing mast104to cant leeward reduces the heeling moment acting on sailing vessel100, thus reducing the roll angle of sailing vessel100given the same wind conditions. This allows sailing vessel100to withstand greater wind conditions before reaching the same maximum desirable heeling moment or maximum heeling angle than would otherwise result if mast104were fixedly secured to deck110. In general, it is desirable to allow mast104to cant at an angle of between 0 and 30 degrees when a sailing vessel has been rolled by the wind at an angle of between 20 and 40 degrees.

A heeling moment generated by the wind against sail106is approximately a function of a chord of sail106, a height of sail106squared, the cosine of the heeling angle of mast104with respect to the vertical, wind speed and apparent wind angle. A righting moment of a multihull is principally defined by a width or “beam” of the vessel, a weight or displacement, and a vertical height of the center of gravity (Cg) that is lower in the water than a center of buoyancy (Cb). The righting moment is also a function of heel angle, initially approximately one-half of the beam times the weight, increasing with the heel angle until a windward outrigger just leaves the water, then decreasing rapidly until the vessel reaches a capsize angle. Ideally, a vessel should be designed so that the maximum righting moment is greater than the expected heeling moment just as the windward outrigger clears the water. From these two relationships, it is possible to calculate a maximum heeling moment that a multi-hull vessel can experience before capsizing and, thus, an amount that mast104must cant to keep the heeling moment below the maximum heeling moment. By canting mast104, the apparent area of sail106with respect to the wind is decreased, thus reducing the heeling moment by a factor approximately equal to the cosine of the heeling angle of the vessel caused by the wind.

Ideally, for a multi-hull vessel, mast104should remain perpendicular to deck110of hull102until the vessel is rolled by the wind to the heel angle where the windward hull just comes out of the water, where the heeling moment is at a maximum, and then should cant an amount to maintain the vessel at that heel angle or less (i.e., maintain the maximum heeling moment or reduce it). In this case, mechanical energy storage means208is non-linear, i.e., it does not allow mast104to cant until a multi-hull sailing vessel is rolled to the capsize angle.

However, in an embodiment where mechanical energy storage means208is a linear device, such as a linear spring, then an expected maximum wind speed limit may be placed on the design of a multi-hull vessel, such as 60 knots for example, where a maximum heeling moment will occur at that windspeed. A spring constant may then be chosen to allow mast104to cant enough to limit the heeling moment to the maximum heeling moment until the wind blows with enough force to cause the heeling moment to exceed the capsize angle, even with mast104canted.

Thus, a spring constant may be chosen by factoring a sail chord, a sail height, a beam of the vessel, a weight of the vessel, a maximum expected wind speed for any given heeling moment and capsize angle.

For example, a J-Class sailboat (a monohull in this example) comprises an approximate righting moment as a function of its ballast, keel dimensions and hull shape, for example 55,000 newton-meters per degree of heel. Typically, when sailing upwind, a J-Class yacht will heel about 25 degrees in 20 knots of wind, and more than 30 degrees in 25 knots of wind.

At 25 degrees of heel, the heeling moment due to the wind acting on the sails and the righting moment of the vessel balance at a value of 25*55,000=1,375,000 newton-meters. If it is desirable to limit the heel to less than 30 degrees, then ideally mast104would begin to cant leeward, relative to the deck of hull102, when the heeling moment exceeds this nominal heeling moment (i.e., 1,375,000 newton-meters). In this ideal embodiment, a non-linear spring mechanism would be used so that mast104would remain perpendicular to the deck until the heel angle reaches 25 degrees, and would then allow mast104to cant leeward to limit the maximum heeling moment to the 30 degree value (30*55,000=1,650,000 newton meters).

If the spring mechanism comprises a simple linear device, i.e., a spring having a spring constant of, for example, 55,000 newton-meters per degree, then in 20 knots of wind, equilibrium would be reached when the heel angle and mast104are about 20.5 degrees from the vertical. Increasing the wind speed to 25 knots produces an equilibrium condition of about 23 degrees of heel, as opposed to a non-canting mast104of about 30 degrees. Decreasing the spring constant will allow more cant of mast104, thus reducing the equilibrium heel angle.

It should be noted that a side effect of allowing mast104to cant is that the total equilibrium heeling moment value is reduced, thus the total driving force of sail106is reduced, which has a secondary impact on the sailing performance which feeds back to a small impact on the heeling moment, thus the calculation of final equilibrium conditions in terms of heel, and yacht speed, is an iterative process.

FIG.4is an aft, side, cutaway view of another embodiment of pivot assembly108andFIG.5is a starboard, side view of the pivot assembly108as shown inFIG.4, showing mast104rotatably coupled to pivot assembly108via fulcrum204placed through a hole in mast104and a hole through a port hub200aand a hole through a starboard hub200b(not shown inFIG.4in order to view the detail mechanical energy storage means208). It should be understood that the relative dimensions shown inFIGS.4and5are not to scale. In this embodiment, mechanical energy storage means208comprises two coil springs, a port coil spring400a(hidden from view by mast104inFIG.4) and a starboard coil spring400b, each having a spring constant that limits the amount of cant of mast104towards the port side and to the starboard side of sailing vessel100with respect to deck110, thus allowing a reduction in a heeling moment to sailing vessel100caused by the wind acting on sail106, as discussed above. Each coil spring is mechanically coupled at a first end402to mast104and at a second end404to each hub200, respectively, and the coil springs are mounted such that when the mast cants in one direction, one of the coil springs becomes coiled, generating a counter-moment, or righting moment, against mast104while the other coil spring uncoils, generating little to no torque on mast104, and vice versa. As a wind acts upon sail106from the starboard side of sailing vessel100, mast104is canted towards the port side (leeward) of sailing vessel100with respect to deck110by the weight of the rig, and coil spring400bresists this moment, limiting the range of cant to the port. The amount that mast104is allowed to cant with respect to deck110is determined by the spring constant of each coil spring, the height of mast104, the area of sail106and other factors as discussed above. Similarly, when a wind acts upon sail106from the port side of sailing vessel100, mast104cants towards the starboard side (leeward) of sailing vessel100with respect to deck110by the weight of the rig, and coil spring400aresists this moment, limiting the range of cant towards the starboard.

FIG.6is an aft view of one embodiment of a single-hull sailing vessel100with a wind acting on sail106from a starboard side of sailing vessel100, configured to allow sail106to cant towards the port side of sailing vessel100(and to the starboard side of sailing vessel100when the wind blows from the port side) with respect to deck110of hull102. It should be understood that the relative dimensions and angles shown inFIG.6are not to scale. For purposes of discussion, with the wind coming from the starboard side of sailing vessel100, a direction into the wind may be referred to herein as “windward” while a direction with the wind may be referred to herein as “leeward”.

FIG.6shows single-hull sailing vessel100at a maximum desired heeling angle600, i.e., an angle600between an imaginary vertical axis602and an imaginary axis606perpendicular to deck110as the wind blows against sail106from the starboard side of single-hull sailing vessel100. Imaginary axis606represents an axis where mast104would be positioned if it were not rotatable via pivot assembly108. The maximum desired heeling angle600is an angle at which persons onboard sailing vessel100may not be able to stand or otherwise be comfortable. For example, the maximum heeling angle600may be selected during design of sailing vessel100to be 40 degrees from vertical axis602.

As the wind acts upon sail106from the starboard side, it generates a heeling moment that causes single-hull sailing vessel100to roll towards the port side. The maximum desired heeling angle600is achieved when the wind blows with such velocity as to create a maximum heeling moment against single-hull sailing vessel100. The maximum heeling moment may be approximated using physical dimensions and characteristics of single-hull sailing vessel100, such as the chord of sail106, a height of sail106squared, the cosine of heeling angle600, the wind speed and an apparent wind angle.

As single-hull sailing vessel100begins rolling as a result of the wind acting on sail106from the starboard side, mast104automatically cants to the port side (i.e., leeward) with respect to deck604under the weight of the rig via rotary assembly108, forming a cant angle608with respect to imaginary axis606, generally in proportion to the heeling moment experienced by single-hull sailing vessel100when mechanical energy storage means208comprises one or more linear springs. In an embodiment that utilizes one or more non-linear springs or other mechanical devices, mast104remains generally perpendicular to deck110as the wind acts on sail106until single-hull sailing vessel100(and mast104) is at or near (i.e., within 1 to 10 degrees) of maximum desired heeling angle600. At this point, mast104begins canting leeward towards the port side in order to reduce the heeling moment experienced by single-hull sailing vessel100at or near the maximum desired heeling angle600.

In one embodiment, mast104is allowed to rotate until it reaches a maximum cant angle608, such as 5 degrees. The amount of cant is determined by the spring constant or restoring force of mechanical energy storage means208, the weight of mast104and sail106, and the wind speed and direction. In another embodiment, where the spring constant or stiffness is less, mast104may continue to rotate past maximum cant angle608, which would continue to reduce the heeling moment on single-hull sailing vessel100.

FIG.7is an aft view of one embodiment of a multi-hull sailing vessel708, in this embodiment, a trimaran, comprising pivot assembly108that allows mast104to cant with respect to deck110in order to reduce a heeling moment acting on multi-hull sailing vessel708when the wind acts on sail106. It should be understood that the relative dimensions and angles shown inFIG.7are not to scale. Multi-hull sailing vessel708comprises elements similar to the single-hull sailing vessel100as shown inFIG.6, with an addition of port outrigger700coupled to center hull102via at least two cross beams702(only one of which is shown as the other is hidden from view inFIG.7) and starboard outrigger704coupled to center hull102via at least two cross beams706(only one of which is shown as the other is hidden from view inFIG.7).

Similar to the single-hull sailing vessel100as shown inFIG.6, multi-hull sailing vessel708will roll to the port side or to the starboard side by a heeling moment created against multi-hull sailing vessel708when a sufficient wind force acts on sail106from the starboard side or port side, respectively. When rolled, one or the other outriggers may be lifted out of the water710, as shown inFIG.7. However, without use of pivot assembly108, if multi-hull sailing vessel708is rolled past a capsize angle600, the heeling moment overcomes the righting moment (caused by the weight of mast104, sail106, and one of the outriggers and cross beams), it will generally capsize. Utilizing pivot assembly108, mast104is allowed to cant past the capsize angle600, forming cant angle608with respect to imaginary axis606that is perpendicular to deck110. As mast104is allowed to cant past capsize angle600, the heeling moment against multi-hull sailing vessel708is reduced, thus avoiding capsizing.

As in the embodiment shown inFIG.6, as multi-hull sailing vessel708begins to roll as a result of a heeling moment applied to multi-hull sailing vessel708by the wind acting on sail106from the starboard, mast104begins canting in a leeward direction with respect to deck110(i.e., towards the port) due to the weight of the rig, forming cant angle608, generally in proportion to the heeling moment when mechanical energy storage means208comprises one or more linear springs. In an embodiment that utilizes one or more non-linear springs or other non-linear mechanical devices, mast104remains generally perpendicular to deck110as the wind acts on sail106until multi-hull sailing vessel708(and mast104) is at or near capsize angle600. At this point, mechanical energy storage means208begins allowing mast104to cant leeward in order to reduce the heeling moment experienced by multi-hull sailing vessel708, thus allowing the wind to blow harder against sail106than would normally be allowed before capsizing.

Also similar to the embodiment shown inFIG.6, in one embodiment, mast104is allowed to cant until it reaches a maximum cant angle608, such as 25 degrees. The amount of cant is determined by the spring constant or restoring force of mechanical energy storage means208and the righting moment created by the weight of mast104, sail106, one of the outriggers and associated cross beams, and the wind speed and direction. In another embodiment, mast104may continue to rotate past maximum cant angle608, which would continue to reduce the heeling moment on multi-hull sailing vessel708.

FIG.8is a perspective view of another embodiment of a multi-hull sailing vessel, shown as multi-hull sailing vessel800, comprising a fore pivot assembly802and an aft pivot assembly804coupling a fore cross beam806and an aft cross beam808to center hull810that allows center hull810to rotate to the port and to the starboard with respect to port outrigger812and starboard outrigger814in order to reduce a heeling moment acting on multi-hull sailing vessel800when the wind acts on mast and a sail of multi-hull sailing vessel800. It should be understood that the relative dimensions and angles shown inFIG.8are not to scale. The mast and sail of multi-hull sailing vessel800is omitted from the view shown inFIG.8in order to better illustrate the two pivot assemblies, but that the mast and sail are shown inFIG.9. It should be understood, however, that in this embodiment, the mast is fixedly coupled to center hull810.

Each of the pivot assemblies comprises a first portion816coupled to a respective cross beam, as shown, and a second portion818coupled to a deck820of center hull810. The two portions of each assembly are rotatably coupled together via rotary coupler822, such as a pin, a rotary collar, or some other well-known rotary coupling device, allowing center hull810to rotate clockwise and counter-clockwise, or to the port and starboard.

Each of the pivot assemblies may comprise one or more mechanical energy storage means824, shown in this embodiment as a pair of leaf springs extending from each pivot assembly. In other embodiments, only one of the two pivot assemblies comprises one or more mechanical energy storage means824. In this embodiment, when the wind acts on sail106from the starboard, fore leaf spring824aand aft rear spring824cact upon fore cross beam806and aft cross beam808, respectively, thus resisting the heeling moment caused by the wind and allowing center hull810and mast104to cant leeward, or counterclockwise, towards the port with respect to the outriggers. Similarly, when the wind blows from the port side, fore leaf spring824band aft rear spring824dact upon fore cross beam806and aft cross beam808, respectively, resisting the heeling moment caused by the wind and allowing center hull810and mast104to cant leeward, or clockwise to the starboard.

Each of the mechanical energy storage means824comprises a spring constant or stiffness that limits the cant of mast104as wind acts on the sail. The greater the spring constant or stiffness, the less the mast will cant, and vice-versa.

It should be understood that although multi-hull sailing vessel800is shown comprising two mechanical energy storage means824(one fore and one aft), in other embodiments, only one mechanical energy storage means824is used, either in fore pivot assembly802or aft pivot assembly804.

FIG.9is an aft view of multi-hull sailing vessel800, shown with cross beam808rotated to a capsize angle900formed between an imaginary vertical axis902perpendicular to waterline906and an imaginary axis904perpendicular to cross beam808as the wind blows against sail106from the starboard. It should be understood that the relative dimensions and angles shown inFIG.9are not to scale. Cross beam806is hidden from view behind cross beam808. The capsize angle900is the maximum angle from the vertical that multi-hull sailing vessel800, i.e., cross beams808and806, can roll with respect to vertical axis902before multi-hull sailing vessel800capsizes.

As the wind begins to act upon sail106, a heeling moment is created and applied to multi-hull sailing vessel800, causing center hull810to rotate counter-clockwise, or to the port side. Mechanical energy storage means208, in this case leaf spring824ccontacts an underside of aft cross beam808(as well as leaf spring824acontacting an underside of aft cross beam806, hidden from view), which resists the heeling moment, allowing mast104and hull810to cant to a canting angle908as shown. Thus, center hull810and mast104operate at a differential angle910with respect to one another, and different angles with respect to vertical axis904(i.e., center hull810/mast104at angle912from vertical axis904and cross beams806/808at angle900from vertical axis904).

Allowing center hull810and mast104to cant to canting angle908reduces the heeling moment experienced by multi-hull sailing vessel800so that multi-hull sailing vessel800can withstand greater winds without capsizing than would otherwise be possible if center hull810were fixed to cross beams806/808.

It should be understood that although the multi-hull sailing vessel800shown inFIGS.8and9utilize fore pivot assembly802and aft pivot assembly804to allow center hull810/mast104to rotate/cant with respect to cross beams806/808, other mechanical arrangements are contemplated in order to implement the inventive concept of allowing a center hull and mast to rotate/cant as a wind acts on one or more sails of a multi-hull vessel in order to reduce a heeling moment. For example,FIG.10illustrates an aft view of a multi-hull sailing vessel an embodiment where mechanical energy storage means208comprises a leaf spring1000coupled to a deck1002perpendicularly to a fore-aft axis of the vessel, with a port extension1004and a starboard extension1006extending upwards from each end of leaf spring1000, respectively. When sailing vessel1000is rolled clockwise by a heeling moment caused by a wind from the port, as shown, extension1004contacts aft cross beam1106, which resists the heeling moment and causes center hull1002and mast104to cant leeward, i.e., clockwise, towards the starboard, and vice-versa. The harder the wind blows, the more center hull1002and mast104is canted, limited by the stiffness or spring constant of leaf spring1000.

FIG.11is an aft view of another embodiment of a multi-hull sailing vessel, shown as multi-hull sailing vessel1100, comprising components similar to the embodiment shown inFIGS.8and9. It should be understood that the relative dimensions and angles shown inFIG.11are not to scale. In this embodiment, fore cross beam806is replaced by two, shorter, fore cross beams806aand806b(not shown in this view), fore port cross beam806acoupling a fore portion of center hull810to port outrigger812and fore starboard cross beam806bcoupling the fore portion of center hull810to starboard outrigger814, and aft cross beam808is replaced by two, shorter, aft cross beams808aand808b, aft port cross beam808acoupling an aft portion of center hull810to port outrigger812and aft starboard cross beam808bcoupling a starboard, port, aft portion of center hull810to an aft portion of starboard outrigger814.

In this embodiment, each of the cross beams are formed from a semi-rigid material, such as fiber reinforced composite material, having a stiffness that allows center hull810and mast104to cant to a predetermined canting angle1102from an imaginary axis1104from where mast104would be positioned, given the same heeling moment applied to multi-hull sailing vessel1100given the same wind speed and apparent wind direction, while maintaining a horizontal relationship between center hull810and each outrigger when a heeling moment is not acting on multi-hull vessel1100, or when one outrigger is lifted out of the water (for example, outrigger814as shown inFIG.10).

While the foregoing disclosure shows illustrative embodiments of the invention, it should be noted that various changes and modifications could be made herein without departing from the scope of the embodiments as defined by the appended claims. Furthermore, although elements of the invention may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated.