Field of the Invention

The present invention relates to a mast and sail combination for a wind-powered craft such as for example a sailboat or the like.

Background of the Invention

Traditionally, sailboats are provided with a mast, a boom and a main sail attached to at least the mast and partially to the boom. Furthermore, foresails may be stayed between the mast and the bow of the vessel.

Much engineering has gone into designing the sails and the mast such that an optimum airflow across the mast and the sails is obtained in order to create maximum power and thereby speed of the vessel. It has been realized that especially with respect to the main sail it is advantageous to have a substantially laminar flow past the mast and the sail in order to generate maximum lift and thereby maximum power. For this purpose various suggestions in the art have been made on how to create a mast having a cross sectional shape corresponding to an airfoil and attaching the sail to the rear side of the mast with as little turbulence making implements as possible. One solution is suggested in DE 19520019 specifically directed at a mast and sail combination for a windsurfer, where the mast itself has a cross-sectional circular shape, but the mast is inserted into a pocket in the sail such that sail battens arranged in batten pockets in the sail will be tensioned whereby the sail will attain the curved shape. By arranging a flexible covering part of the sail as well as surrounding the mast the curva- ture in the sail will deform the covering and thereby create a mast and sail shape which is substantially free of any turbulence inducing implements. Theoretically, the shape of this construction is comparable to the shape of a wing used in airplanes such that maximum lift will be created on the lee side of the sail. A comparable construction is suggested in DE 8525953 wherein a circular mast is also surrounded by a covering which covering is shaped by a combination of sail battens and a special insert creating tension in the sail batten and at the same time being able to rotate around the circular mast.

In DE 20114841 the problem is addressed in a different manner. A hollow mast profile having a cross sectional part-airfoil shape has air channels provided on either side of the mast along the length of the mast. The mast is furthermore provided with an outer skin such that by providing air pressure in one or both of the channels on either side of the mast the outer skin can be deformed thereby attaining a more aerodynamic optimal shape such that the transition between the mast and the sail attached to the rear end of the mast is as smooth and non-turbulent as possible.

A further example is disclosed in EP 0446615 wherein a circular mast is provided with transition members where each transition member is furthermore provided with a sail attachment member, flexibly attached to said attachment member. The transition members are distributed along the mast.

A further example is illustrated in WO2008/136669. The sail is provided with a plural- ity of horizontal battens which all extends into a special profile provided in/on the mast. The object of the construction is to allow for easy hoisting and lowering of the main sail on sailing vessels. To this end the ends of the battens arranged inside the mast are provided with spherical bodies which shall easy the friction, avoid jamming and thereby facilitate easy hoisting and lowering of the sail.

Common for these prior art solutions are that they either require very complicated mast constructions, complicated connections between the mast and sail surface, or involve a number of parts which needs to act flawlessly together in order to achieve the intended purposes.

Object of the Invention

Consequently, it is an object of the present invention to provide a mast and sail combination which alleviates the disadvantages of the prior art and furthermore provides ad- ditional user friendly advantages and increases aerodynamic performances and thereby increased lift.

Description of the Invention

The present invention addresses this by providing a mast and sail combination for a wind powered craft, in particular a sailboat, wherein the mast has a length along a longitudinal axis, a forward surface and a rear edge relating to the intended direction of vehicle travel, and where for at least a part of the mast's length, the mast has a cross sectional shape corresponding to an airfoil, where along the rear edge of said mast, means are provided for attaching a sail, where said sail is provided with one or more battens arranged in batten pockets in the sail, where at least one primary batten extends from the sail's leech and into said mast, where said primary batten is arranged at an angle relative to the longitudinal axis of said mast, which angle is less than 90°.

With this setup the primary batten continues into the mast profile. Furthermore, the primary batten is movable inside the mast profile such that the primary batten may pivot about a point substantially corresponding to the rear edge of the mast. In this manner it is possible for the primary batten to attain a position relative to the side of the mast such that a substantially flush relationship will be obtained between the mast's aerodynamic/airfoil shape and the sail surface mounted to the rear edge of the mast. By furthermore arranging the primary batten such that the batten is not perpendicular to the mast, the primary batten will increase the batten's sail- shape performance characteristics, such that by adjusting the primary batten correctly relative to the mast the sail surface may obtain an optimum shape according to the present wind and sailing conditions. Had the batten been arranged substantially perpendicular to the mast, the leech of the sail would require special means in order to tighten/adjust the leech. The shape of the sail adjacent the leech is also very important in generating the most optimum passage of the wind past the sail, and thereby generating lift.

In this context the formulation "angle is less than 90°", shall be understood as the bat- ten not having an angle relative to the longitudinal axis of the mast of 90°, as for example the battens illustrated in WO2008/136669 has. Airfoil shape relates to a cross section which will increase the mast's performance. Traditional masts are round or rectangular in cross section, whereas some of the prior art cited above refers to masts provided with means between the mast profile and the sail, which in fact acts as an airfoil shape, see for example DE08525953. It is however a more stable, stiff and more reliable construction to have the mast itself in the shape of an airfoil.

In a still further advantageous embodiment of the invention a mounting clamp is provided at the luff edge of the sail where said primary batten extends into the mast, where said mounting clamp is provided on both sides of the sail material and that an aperture corresponding in size to the cross section of the primary batten is provided in said mounting clamp.

The mounting clamp serves to support the sail surface in the position where the pri- mary batten extends out through the batten pocket such that increased strength is provided in this position. Furthermore, by providing the mounting clamp with a certain thickness it will also serve as part of a "hinge" in that as the primary batten pivots around the rear edge of the mast, the mounting clamp will provide a larger surface and point of resistance such that the sail surface will not deform in this area but provide a smooth sail surface and thereby increased performance, i.e. no turbulence generating effect.

The mounting clamp in this manner serves at least five purposes: first to guide the batten into the masts profile, secondly to provide wear-protection between the batten, sail and mast, thirdly to allow the sail to slide easily up/down the mast in use, fourthly as a hinge member, allowing the batten and thereby sail to pivot relatively to the mast, and fifth as a backstop when the sail is strung out between the battens intersection with the clamp and the opposite end of the batten at the leech of the sail. In a still further advantageous embodiment the primary batten is provided with means for engaging the mounting clamp, said means is arranged at a distance from an end of said primary batten, such that only a pre-determined part of said primary batten may extend through the aperture in the mounting clamp into the mast. In this manner it is possible to tension the sail relative to the batten without affecting the part of the primary batten being inserted into the mast such that depending on wind conditions the sail may be more or less tensioned and/or provided with a curved shape without this having an effect on the part of the primary batten inserted inside the mast. The mounting clamp will provide a hold against the rear edge of the mast and as the primary batten is suspended between the mounting clamp and the claw of the sail the forces generated in the primary batten will be maintained in the sail's surface in order to shape the sail appropriately.

In a still further advantageous embodiment of the invention the end of the primary batten opposite the end of the batten extending into the mast terminates in the clew of the sail. By introducing the feature that the primary batten is arranged at an angle less than 90° relative to the longitudinal axis of the mast, it is possible to allow the primary bat- ten to extend to the claw of the sail whereby the primary batten and the tension brought to the sail by means of the primary batten will be transferred to substantially the entire surface of the sail both above and below the primary batten's pocket.

Especially for larger sails the invention in a further advantageous embodiment provides that a plurality of secondary battens are provided distributed in the sail's surface, extending at an angle relative to the mast, where said secondary battens does not enter the mast. In this manner it is possible to obtain an optimum shape of the sail over a substantially large sail surface where the form-giving properties added to the primary batten may be at least partly transferred to the secondary battens whereby a relatively fixed shape of the sail may be obtained for improved performance.

In a still further advantageous embodiment of the invention a leech tensioning cord, a luff tensioning cord and a foot tensioning cord are provided in the sail. Although leech, luff and foot tensioning cords may be considered trivial for traditional sails, these tensioning cords provide special and added advantages when implemented together with the primary batten. By initially tightening the luff tensioning cord thereby bringing the tack of the sail as far down as possible, the front edge of the sail will cause the mounting clamp to be arranged in a relatively fixed vertical position relative to the rear edge of the mast. In this position, however, the mounting clamp and the primary batten due to its insertion into the rear edge of the mast will still be allowed to pivot relative to the mast such that no horizontal limitation of the sail is induced by tension- ing of the luff cord. The primary batten will be able to pivot in a horizontal plane in order to follow the sails position, i.e. either sailing on starboard or port tack, and pivot in a vertical plane, having the point where the batten enters the mast as a pivot point. The pivotal action is created when the foot tensioning cord is loosened or tightened, which will cause the primary batten to rotate.

By furthermore tensioning the leech tensioning cord, the leach of the sail will be stabilised in a normal manner, also known from regular sail crafts. By finally tensioning the food tensioning cord the sail surface will be stretched all over the sail surface due to the provision of the primary batten and the mounting clamp. The mounting clamp will act as a pivot point around which the primary batten will be able to pivot slightly in a vertical direction whereby the leech of the sail will be stretched, activated by the foot tensioning cord. In this manner and optionally with help from the secondary battens it is possible to create a substantially stiff sail surface suspended between the mast, the leech and the primary batten and the foot tensioning cord.

In embodiments where the mast has an airfoil shape, the surface of the mast will continue, substantially unbroken onto the sail, whereby the sail and mast together forms a lift generating surface. In a still further advantageous embodiment the distance between the mast's forward surface and the rear edge is not constant, and the mast is provided with pivotal means connecting the mast to the craft. The mast is in this manner provided with a certain amount of flexibility along its length in that the decreased distance between the forward surface and the rear edge will make it relatively less stiff in the top than in the bottom. Therefore, by for example tightening the foot tensioning cord the mast will have a tendency to bend backwards due to the transfer of stress from the foot tensioning cord through the leech of the sail. Furthermore, by providing pivotal means such that the mast may pivot about a longitudinal axis it is possible to adjust the sail and the airfoil mast in such a manner that the mast and the sail together in any position will obtain the optimum curved shape relative to the wind in order to generate maximum lift.

In this context it shall be noted that the leech may be provided with a leech tensioning cord, which in cooperation with the foot tensioning cord is used to adjust the tensioning in the leech of the sail.

In a still further advantageous embodiment of the invention the primary batten terminates in the sail's claw, and the craft's main sheet is attached to the claw optionally directly at the primary batten's termination.

In this configuration the primary batten acts as a boom, i.e. having a combined effect as a sail batten and a boom such that it is possible to adjust and manoeuvre the sail in a conventional manner by manipulating the main sheet. Description of the Drawing

Figure 1 illustrates a mast and sail combination

Figure 2 illustrates a cross section through the primary batten and the mast

Figure 3 illustrates a mast and sail combination

Figure 4 and 5 illustrate details of the mounting clamp Detailed Description of the Invention

A mast and sail combination according to the invention is illustrated in figure 1. The mast 1 has as illustrated in figure 2, which will be described below, a cross section which is aerodynamically advantageous, for example in the shape of an airfoil. The mast has a front surface 2 and a rear edge 3. Along the rear edge a sail 4 is attached to the mast. The sail 4 is in this embodiment provided with a primary batten 5 as well as secondary battens 6.

The primary batten 5 extends between the claw 7 of the sail 4 and into the interior of the mast 1 as will be described below with reference to figure 2. In the sail 4 is pro- vided batten pockets in which the battens 5, 6 are accommodated. The batten pocket accommodating the primary batten 5 is furthermore provided with a mounting clamp 8 which will be further described with reference to figure 4 and 5. The primary batten is arranged at an angle ά which a less than 90° relative to the longitudinal axis of the mast 1 schematically indicated by the dashed line 10. A main sheet 9 is connected between the claw 7 of the sail at the primary batten's 5 termination point and the vessel 11. In this configuration 11 the primary batten 5 will in effect be acting both as a batten and as a boom.

The mast 1 is furthermore mounted to the vessel 11 by means 12 allowing the mast 1 to pivot about the longitudinal axis 1 of the mast such that the combination of mast and sail may be arranged at the most appropriate angle relative to the wind whereby both the mast and the sail will provide lift and thereby power to the vessel 11. In this manner it is possible to provide a mast and sail combination where both the mast and the sail provides part of the lift which is necessary in order to power the vessel. By furthermore providing the mast 1 with an aerodynamic shape and allowing the sail to be shaped due to the provision of the primary batten 5 and the secondary batten 6 the overall mast and sail combination will for the sake of generating lift be acting as one homogenous unit.

Turning to figure 2 a cross section through the primary batten 5 and the mastl is illus- trated. In dashed lines is illustrated the position of the primary batten 5 ' after the mast and sail combination has been tacked, i.e. after the vessel has changed its course relative to the wind. As is evident from figure 2, a part 5" of the primary batten 5 extends into the interior of the mast 1, and the extent is limited by the mounting clamp 8. Turning back to figure 1 the sail is provided with a foot tensioning cord 14 along the foot of the sail and a luff tensioning cord along the luff 15 of the sail. The luff tensioning cord is arranged such that the tack 16 of the sail may be pulled downwards relative to the head of the sail 17 in order to straighten the luff 15. When luff tensioning has taken place the mounting clamp 8 will in practice be fixed vertically relative to the mast 1 , but may still be free to pivot in a horizontal direction as indicated in figure 2. As it is important to shape the sail according to the wind conditions, i.e. for example in strong winds it is desirable to have a flat sail whereas in less wind it is desirable to have a strong curvature in the sail, the present invention also provides for these trim options. In order to trim the sail the luff tensioning line may be tightened more or less such that sail's luff along the rear edge 3 of the mast 1 may be more or less tensioned. This is carried out by adjusting the distance between the tack 16 and the head of the sail 17. By stretching these as far apart as possible the sail 4 between the tack 16 and the head of the sail 17 will be under heavy tension and thereby be relatively flat. By furthermore extending the leech of the sail 13 as much as possible from the rear edge 3 of the mast 1 the sail will also be flattened in that direction. This flattening is obtained by putting as much tension as possible in the primary and secondary battens 5, 6.

Therefore, by initially tightening the luff tensioning cord such that the tack 16 is mov- ing downwards the position of the mounting clamp is more or less fixed vertically relative to the mast.

Secondly, by tightening the foot tensioning cord 14 the claw 7 will be slightly rotated around the mounting clamp 8 whereby the leech 13 of the sail will be straightened and become tight. In this manner the sail is suspended around the primary batten 5. The main sheet 9 attached to the claw 7 where the primary batten 5 terminates will then use the primary batten 5 as a boom in order to adjust the position of the sail 4 and the mast 1 due to the pivotal mounting means 12 of the mast relative to the vessel 11. Turning to figures 4 and 5 details of the mounting clamp are illustrated where the mounting clamp 8 is provided along the luff 15 of the sail such that the primary batten 5 is provided with an extension 5 ' ' which when the sail is mounted on the mast 1 will extend into the interior of the mast 1 as already illustrated in figure 2. The primary batten 5 is arranged in a batten pocket 18. The mounting clamp 8 is in this embodiment a two-part member which is arranged on either side of the sail surface 4 as illustrated in figure 5. The two parts 8', 8" of the mounting clamp are connected by appropriate means, in this example illustrated by a bolt 19. In the mounting clamp part 8" is provided an aperture 20 which is connected to the batten pocket 18 such that as the pri- mary batten 5 is inserted into the batten pocket 18 the section 5 " of the primary batten 5 may extend through the aperture 20 and into the interior of the mast as illustrated in figure 2. The batten is fixed relative to the clamp. In this embodiment a two-part clamp is illustrated, arranged on both sides of the sail's surface. It is however possible to have a one-part clamp attached to one side of the sail, or a multi-part clamp. For example a clamp construction having apertures on both sides of the sail, where a double primary batten is arranged in pockets on either side of the sail may be contemplated with in the scope of the present invention.

In order to be able to tension the sail between the mounting clamp and the claw (the primary battens termination point) means (not illustrated) are provided for fixing the primary batten 5 relative to the mounting clamp 8 such that the sail surface 4 between the mounting clamp and the claw, see figures 1 and 3, may be extended in order to obtain the desired tensioning in the sail 4 and thereby the curvature desirable according to the present wind conditions.