Patent Description:
Sails have been known for a long time as means of propulsion of ships. Traditionally, flexible sails have been mounted on masts to harness the power of wind and propel the ship. The modern merchant vessels commonly use fossil fuels and combustion engines to propel the vessel. Use of wind propulsion has been suggested to reduce the overall consumption of fossil fuels. For this purpose, rigid sails can be used. The amount of power being generated is related to a large number of interlinked factors, but wing area and other geometric aerodynamic characteristics are primary performance indicators. A possible geometric setup can be achieved by combining a main wing with a flap that can generate a large propulsive force given the wing size, compared to a wing without a flap. High efficiency wingsail arrangement and structure that can generate a large amount of propulsive force given its absolute size can be obtained for example by adjusting a camber formed by the main wingsail and the flap. When aerodynamic propulsive force from the wingsails is not desired or the force should be limited, the vessel stability, vessel safety and operability should be taken into consideration. This adds complexity and challenges in using rigid wingsails as ship propulsors. In addition to this, the vessel performance is related to the prevailing wind strengths and directions. Due to the statistical distribution of for example wind strength, it is clear that during the majority of time the wind speed is fairly moderate. Therefore, the wing characteristics should be configured so that the wingsail can utilize low wind speeds and at the same time be able to cope with more rarely occurring high wind speeds in a safe manner.

The use of rigid sails has been discussed in the prior art. For example, <CIT> discloses a reefable double airfoil, having shape members for the respective fore and aft flap, which are traversed by a fore mast while being able to turn around an axis defined thereby. In a variant, the flaps are constructed as rigid boxes, which can be telescopically nested in series. <CIT> also discloses in a variant a double flap sail construction in which each flap can be made by telescopically nesting a series of generally rigid box type shape members. However, the telescopic nesting may lead to wear of the boxes and this in turn may lead to problems with fit of the boxes when nesting the boxes. In case of damage to the boxes, it may be difficult to retract the sail whereby the construction may be subject to forces exerted by the wind when propulsion by the wingsail is not desired.

A rigid sail is known for example from a document <CIT>, which discloses a construction for a rigid sail assembly which includes a rigid mainsail section and a rigid jibsail section, both of complemental airfoil cross-sectional configuration and rotatably displaceable, as a unit, through <NUM> relative to the ship centerline, and with the jibsail section being further independently arcuately displaceable within a sector of predetermined angular extent relative to said mainsail section. However, this construction may be subject to forces exerted by the wind when the vessel is docked or when propulsion by the wingsail is not desired. Further rigid sails are shown by <CIT> and <CIT>.

Another example of a rigid sail is shown in a document <CIT>, which discloses an articulated rigid sail intended to ensure the propulsion by wind of an aquatic or land vehicle. The rigid sail comprises a mast on which a plurality of modules are mounted, spaced vertically apart, and to which a rigid shell forming a sail is fixed. Each module of two articulated sections makes it possible to curve the profile of the sail. However, this sail poses problems when the vessel is berthed. The sail surface enabling the vessel to make headway when it is under way remains subject to the forces exerted by the wind when the vessel is docked, which can be harmful for the vessel.

Thus, in view of the known solutions, there is a need for a sail structure which can be placed in a neutral non-propulsive position in a robust and space-saving manner when propulsion is not desired, for example when the vessel is docked.

In view of the disadvantages and limitations with the prior art solutions, it is an aim with the present invention to provide a marine vessel with a wind-assisted propulsion arrangement, which at least partially solves the problems with the known solutions especially relating to arranging a sail structure in a neutral non-propulsive position in a robust and space-saving manner, when propulsion is not desired.

However, it has been additionally noted that since the rigid sails cannot be reefed and the telescopic solutions may not be sufficiently robust in harsh weather conditions, stowing of large rigid airfoil structures in a space-saving manner has been found to be a challenge. Therefore, it has been noted that there is a need to provide efficient and robust stowing of rigid wingsails in a space saving manner. It is therefore a further aim with the present invention to provide stowing of large rigid airfoil structures in a space saving manner.

The above aims are attained by the present invention as defined in the appended independent claims.

According to a first aspect of the invention, the present invention relates to a wingsail structure for a wind-assisted propulsion arrangement of a marine vessel and comprises a wingsail frame. The wingsail frame comprises a main wingsail, a flap and at least one upper and at least one lower coupling member connecting the main wingsail and the flap. The main wingsail is rigid or semi-rigid and has an aerofoil shape with a leading edge, a trailing edge, a top end and a bottom end and side walls extending therebetween. The flap is also rigid or semi-rigid flap and has an aerofoil shape with a leading edge, a trailing edge, a top end and a bottom end, and side walls extending therebetween. The flap may be smaller than the main wingsail. The wingsail structure further comprises a foundation arranged to be fixed to a body of the vessel. The foundation is associated with the wingsail frame such that the wingsail frame is rotatable in respect to the foundation via a first vertical axis of rotation. The upper and lower coupling members are configured to bring the main wingsail and/or the flap to a first unfolded standing position, and to bring the main wingsail and/or the flap towards one another to a second folded standing position. The wingsail structure further comprises a tilting arrangement configured to bring the wingsail frame from the second folded standing position to a third tilted position in respect to the foundation.

Since the flap and/or the main wingsail can be brought to a folded position before tilting the wingsail frame, stowing can be provided in a space-saving manner.

According to an aspect, the upper and lower coupling members are configured to provide a second axis of rotation for rotating the flap in respect to the upper and lower coupling members. The upper and lower coupling members may be further configured to provide a third axis of rotation for rotating the main wingsail in respect to the upper and lower coupling members. This may further improve the adjustment of a camber provided by the wingsail frame.

The upper and lower coupling members may be connected to the respective top end and a bottom end of the main wingsail, and the flap and the lower coupling member is configured to provide the first axis of rotation for rotating the wingsail frame in respect to the foundation. Thus, when the coupling members are rotated in respect of the foundation, the whole wingsail frame can be rotated.

According to a further aspect, the upper and lower coupling members are configured to provide a fourth axis of rotation associated with the main wingsail for rotating the flap in respect to the main wingsail. In this way the flap can be rotated also when it faces towards the same direction as the main wingsail and can thus be moved beside the main wingsail, and thus provides means configured to move the flap such that it faces the main wingsail in the same or opposite direction. Therefore, the transversal extension of the folded wingsail frame can further reduce the transversal extension compared to an unfolded wingsail frame, and thereby further limit the space required by the wingsail frame when in a tilted or stowed position.

The upper and lower coupling members can be connected to the respective top end and a bottom end of the main wingsail and the flap. In this way, e.g. accessibility to react the coupling members may be facilitated.

The upper and lower coupling members may be connected at a distance from the respective top end and a bottom end. In this way, they can be directly connected to the respective main wingsail and the flap.

According to an aspect, in the third tilted horizontal stowage position, the wingsail frame is arranged in a horizontal position in which a side wall extending between the leading edge and trailing edge of the respective main wing and flap faces the body of the vessel. In this way a robust stowage position is provided.

According to another aspect, in a third tilted vertical stowage position, the wingsail frame is arranged in a vertical position in which the leading edge or the trailing edge of the main wingsail faces the body of the vessel and the trailing edge or the leading edge of the flap faces the body of the vessel.

The main wingsail and the flap, respectively, may comprise one or more semi-rigid or rigid modules detachably connected to each other to form an integrated main wingsail or flap with the aerofoil shape. Thus, a modular concept enables for example for assembly of the wingsail frame close to or onboard a vessel where it is mounted.

The present invention also relates to a wingsail frame comprising a main wingsail, a flap and at least one upper and at least one lower coupling member connecting the main wingsail and the flap. The main wingsail is rigid or semi-rigid and has an aerofoil shape with a leading edge, a trailing edge, a top end and a bottom end and side walls extending therebetween. The flap is also rigid or semi-rigid flap and has an aerofoil shape with a leading edge, a trailing edge, a top end and a bottom end, and side walls extending therebetween. The flap may be smaller than the main wingsail. The upper and lower coupling members are configured to bring the main wingsail and/or the flap to a first unfolded standing position, and to bring the main wingsail and/or the flap towards one another to a second folded standing position. The upper and lower coupling means are further configured to provide a second axis of rotation for rotating the flap in respect to the upper and lower coupling members and a third axis of rotation for rotating the main wingsail in respect to the upper and lower coupling members. Further, the upper and lower coupling members are connected to the respective top end and a bottom end of the main wingsail, and the flap and the lower coupling member is configured to provide the first axis of rotation for rotating the wingsail frame in respect to the foundation. Since the flap and/or the main wingsail can be brought to a folded position, stowing can be provided in a space-saving manner, while the adjustment of a camber provided by the wingsail frame is more flexible. The present invention further relates to a wingsail structure comprising the wingsail frame and a foundation connected to a body of a marine vessel.

The present invention also relates to a further wingsail frame comprising a main wingsail, a flap and at least one upper and at least one lower coupling member connecting the main wingsail and the flap. The main wingsail is rigid or semi-rigid and has an aerofoil shape with a leading edge, a trailing edge, a top end and a bottom end and side walls extending therebetween. The flap is also rigid or semi-rigid flap and has an aerofoil shape with a leading edge, a trailing edge, a top end and a bottom end, and side walls extending therebetween. The flap may be smaller than the main wingsail. The upper and lower coupling members are configured to bring the main wingsail and/or the flap to a first unfolded standing position, and to bring the main wingsail and/or the flap towards one another to a second folded standing position. The upper and lower coupling members are further configured to provide a fourth axis of rotation associated with the main wingsail for rotating the flap in respect to the main wingsail. In this way the flap can be rotated also when it faces towards the same direction as the main wingsail and can thus be moved beside the main wingsail, and thus provides means configured to move the flap such that it faces the main wingsail in the same or opposite direction. The present invention further relates to a wingsail structure comprising the wingsail frame and a foundation connected to a body of a marine vessel.

Further, the present invention relates to a wind-assisted propulsion arrangement comprising at least one wingsail structure as defined above, and to a marine vessel comprising the wind-assisted propulsion arrangement.

Further features and advantages of the present invention will be described with reference to the appended drawings in which:.

In order to utilize wind as power for ship propulsion, the wingsails are formed so that they can in itself or together with an engine of the vessel generate sufficient propulsive forces to overcome the ship resistance forces. In this application, a wingsail is generally defined as a rigid or semi-rigid structure, which may be similar to an aircraft wing, and which can be fixed vertically on a marine vessel to provide propulsive force from the action of the wind. When such rigid wingsails are or cannot be used due to for example rough weather, limitation in height in the chosen route or during cargo operation, safety aspects should be ensured.

According to the present invention, a double wingsail configuration, herein referred to as a wingsail frame, comprising a main wingsail and a flap is provided. By folding the flap onto the main wingsail, a more compact wingsail position can be obtained. At the same time, when in use, the flap can be rotated along one or multiple vertical rotation axis/axes in respect of the main wingsail to provide a camber providing propulsive force. By providing a flap, which is rotatable in respect of the main wingsail it is possible to adjust the amount of generated power by adjusting the camber formed by the main wingsail and a flap. Since the flap can be folded towards the main wingsail, a projected area of a wingsail frame can be reduced. Thus, also the space required by the wingsail frame is reduced on board a vessel. When the main wingsail and the flap are folded, also the generated forces can be reduced. In this way, a minimum power configuration can be obtained in desired conditions, which may be important for vessel safety, structural integrity and operability.

To prevent propulsion provided by the wingsails, the wingsail frame can be tilted horizontally towards the deck to a tilted position. By "tilted" position is meant a position in which the wingsail frame is inclined towards a horizontal position and/or can lean towards a deck of the vessel or towards a support on the deck. The wingsail frame can be stowed in this position and the position is herein also referred to as a stowage position. In the tilted position and when the main wingsail and the flap are in a folded position, space can be saved on the deck of the vessel compared to the main wingsail and the flap not in a folded position. This is also illustrated in the appended drawings.

To provide the tilted position the wingsail frame is tilted in respect of a horizontal axis from a vertical standing position towards a horizontal position. The wingsail frame has longitudinal axis, which extends in a vertical direction in respect of the vessel deck when the wingsail frame is in a standing position. The wingsail frame is thus tilted in respect of the horizontal rotation axis, which is perpendicular to the longitudinal axis and thus essentially horizontal or transversal. In the tilted position, the longitudinal axis of the wingsail frame can be thus essentially horizontal. However, tilted wingsails require large space on a deck of a marine vessel, which can be difficult to find. It is therefore essential to minimize the needed space as much as possible to enable installation of the wingsail arrangements, which may comprise a plurality of wingsail structures, on different types of vessels. The present invention additionally provides a solution to minimizing space required when the wingsail is provided in the tilted position.

According to the present invention to minimize the space required, the wingsail and the flap are brought from a first unfolded standing position, in which the wingsail and flap provide propulsive forces to the vessel, to a second folded standing position. By folded standing position is meant that the main wingsail and/or the flap are rotated in respect of one or multiple vertical axis/axes towards one another. The vertical axis is essentially parallel to the longitudinal axis of the wingsail frame in the standing position. When located towards one another, the main wingsail and the flap are in an overlapping position when looking in a transversal plane, i.e. directly in front of the wing structure. The wingsail frame is then tilted in respect of a transversal or horizontal rotation axis, which is perpendicular to the vertical rotation axis, and is tilted towards the deck of the vessel. The folding can be obtained by for example rotating the flap to overlap the main wingsail. In this way, the wingsail frame may be stowed in a neutral, non-propulsive, position. Further, a transversal extension of the wingsail frame is reduced compared to when the wingsail frame is in a propulsive standing position when the main wingsail and flap are folded. This is a huge advantage, since the space onboard a marine vessel is limited. The wingsail frames are typically, but not necessarily, folded in an upright position before the wingsail frame is tilted. Further advantage is that the lifting force from wind will be reduced which can be useful in strong winds to reduce the stress on the components. The wingsail can be tilted down on deck and stored either flat or in an upright position.

The wingsail structure, which comprises the wingsail frame and a foundation, and an arrangement comprising one or more wingsail structures can be used in a marine, or maritime, i.e. a vessel which is used as a means of transportation on water. The main wingsail and the flap are substantially made of a rigid or semi-rigid material and have an aerofoil shape. Both the main wingsail and the flap have sidewalls, a leading edge and a trailing edge and a top end and a bottom end. By "rigid" material is meant a material, which may be a composition of several materials, that is not foldable and can support its own weight when rested upon parallel edges of such materials. "Semi-rigid" material is a material which is partly rigid and has some degree of flexibility but can still support its own weight when rested upon parallel edges of such materials.

By "aerofoil" shape is in this application meant a wing profile having an aerodynamic shape when looked in a transverse section in the fore-to-aft direction, i.e. from a leading edge to a trailing edge direction. The aerodynamic aerofoil shape is advantageous, since it lets the air to pass over wingsail more easily. The shape may be asymmetric in said direction, but it can involve symmetric sections, or the shape may be a symmetric aerofoil. The aerofoil shape may be for example defined according to NACA standardized series, but the shape is not limited thereto.

For better understanding of the invention of the present disclosure, it will now be described with reference to the appended drawings, which are provided to illustrate non-limiting example embodiments of the invention.

Referring to <FIG>, a marine vessel <NUM> comprising a wind-assisted propulsion arrangement <NUM> with three wingsail structures <NUM> is shown. Each of the wingsail structures <NUM> comprises a wingsail frame <NUM>, schematically shown by a rectangle with dotted lines in <FIG>. Both the main wingsail <NUM> and a flap <NUM> are rigid or semi-rigid, meaning that there is a certain degree of flexibility. The wingsail structure is further shown from above in <FIG>, also referred to herein.

The wingsail structure <NUM> further comprises a foundation <NUM>, which is arranged to be fixed to a body <NUM> of the vessel <NUM>. The foundation <NUM> is associated with the wingsail frame <NUM> such that it supports the frame when the wingsail frame is in an upright, vertical standing position, either in a propulsive position (I) or in the folded position (IIa; IIb). The foundation may also be associated with the wingsail frame when it is brought to a tilted position (IIIa; IIIb).

In the first unfolded standing position (I) illustrated in <FIG>, the wingsail frame is arranged in a first, standing, propulsive position (I). The propulsive force provided by the main wingsail and the flap can be varied by altering the camber, i.e. the convexity of the curve of the main wingsail and the flap form from the leading edge of the main wingsail to the trailing edge of the flap. <FIG> illustrates in a view from above an example of a camber in the first propulsive standing position (I).

Both the main wingsail <NUM> and the flap <NUM> have an aerofoil shape. The main wingsail has a leading edge <NUM>, a trailing edge <NUM> (<FIG>), a top end <NUM> and a bottom end <NUM> (<FIG>), and side walls <NUM> and <NUM> extending therebetween (<FIG>). In a similar way, the flap <NUM> has a leading edge <NUM> and a trailing edge <NUM> (<FIG>) and a top end <NUM> and a bottom end <NUM> (<FIG>), and side walls <NUM> and <NUM> extending therebetween (<FIG>). The shape of the aerofoil has generally a tapering shape from the leading edge towards the trailing edge.

The side walls <NUM> and <NUM> are integrated to form the aerofoil shape with the leading edge <NUM> and the trailing edge <NUM>. The side walls <NUM> and <NUM> and the top and bottom ends <NUM>, <NUM> may be formed of modules attached to each other permanently or detachably and the modules together form the integrated wingsail or flap with the aerofoil shape. The wingsail and flap profiles can be designed in different modular elements which can be combined to achieve different size of wing sails. The main wingsail and the flap may comprise any suitable material, such as a moldable polymeric material, glass fiber material, carbon fiber material and/or a composite material, but is not limited thereto.

The wingsail frame <NUM> further comprises an upper coupling member <NUM> and a lower coupling member <NUM>, which are configured to rotatably connect the main wingsail <NUM> and the flap <NUM> in respect to each other. By rotatably connected is meant that the main wingsail <NUM> and/or the flap <NUM> can be rotated around a vertical axis towards one another, which vertical axis is parallel to the longitudinal axis of the wingsail frame. In <FIG> this is illustrated by an arrow R showing how the flap <NUM> can be rotated from a first unfolded standing position (I) around the second vertical rotation axis <NUM> towards the main wingsail <NUM> to a second folded standing position (Ila) shown in <FIG>. In this variant, the second axis of rotation <NUM> in the upper and lower coupling members <NUM>, <NUM> is arranged such that the trailing edge <NUM> of the flap <NUM> is rotatable towards the leading edge <NUM> of the main wingsail <NUM>. In this second folded position (Ila) the side wall <NUM> on the right-hand side of the flap is folded towards the side wall <NUM> on the right hand side of the main wingsail <NUM>. By folding the flap towards the main wingsail, as illustrated in <FIG>, the transversal extension T, which is shown between <FIG>, of the wingsail frame <NUM> can be reduced. The rigid or semi-rigid main wingsail <NUM>, flap <NUM> and the upper and lower coupling members <NUM>, <NUM> form the frame <NUM> for the wingsail structure <NUM>.

The wingsail frame can be connected to the foundation <NUM> for example via a shaft <NUM> (<FIG>) defining a first axis of rotation <NUM> (<FIG>) The wingsail frame <NUM> can rotate in respect to the foundation <NUM> via this first axis of rotation. A non-limiting schematical example of a rotating arrangement <NUM> suitable for rotating the wingsail frame <NUM> is shown in <FIG> shows a simplified schematical illustration of the wingsail frame without the flap and not in scale. The rotating arrangement <NUM> is associated with the shaft <NUM>, which is connected to the foundation <NUM> via an associated tilting arrangement <NUM> explained more in detail below. The shaft <NUM> is connected to the wingsail frame <NUM> via the bottom end <NUM> of the main wingsail <NUM> and may pass through the bottom end <NUM>.

In the shown non-limiting example, the shaft <NUM> is in its upper end <NUM> housed in the interior of the main wingsail <NUM>. The shaft end <NUM> is connected to a drive arrangement <NUM> for the rotation of the wingsail frame <NUM> in respect of a longitudinal rotation axis RW, which extends in a vertical direction V in respect of the deck of the vessel body <NUM>. The drive arrangement <NUM> may be comprise an electrical motor (not shown) or any other suitable driving means including manual crank arms. The shaft <NUM> is also associated with applicable upper bearings <NUM> and lower bearings <NUM> housed in a housing <NUM>. The wingsail frame is rotated around the shaft <NUM> by means of the drive arrangement and by the upper and lower bearings, e.g. rolling bearings.

Generally, the main wingsail, the flap and the upper and lower coupling means may comprise suitable arrangement configured to provide the rotating movement in respect of the rotation axes, and may comprise e.g. shafts, bearings e.g. roller bearings and drive means. The rotation of the wingsail frame, main wingsail and/or the flap can be controlled by incorporating e.g. electrically controllable means to each rotation axis. A control unit can then be connected to the drive arrangement to regulate the rotation of the wingsail frame, main wingsail and/or the flap. The degree of rotation of the wingsail frame, main wingsail and/or the flap is adapted to prevailing surrounding conditions. The rotating arrangement and each of the vertical rotation axes for the main wingsail and flap can be arranged with stop means so that the degree of rotation is angularly limited to a certain degree. By limiting the rotation degree, uncontrolled rotation of the parts of the wingsail frame can be avoided, for example in case of change in the prevailing wind/weather conditions.

According to the present invention, a space saving, tilted stowage position (IIIa, IIIb) can be obtained for the wingsail frame <NUM>, when the flap <NUM> is folded towards the main wingsail <NUM>, and the wingsail frame <NUM> is brought to a third, tilted, stowage position (IIIa) as illustrated in for example <FIG>, <FIG>, <FIG> and <FIG>. The tilted position may be a substantially horizontal position in respect to the deck of the vessel and in which the wingsail frame lies towards the deck.

Reference is now made to <FIG>, in which the wingsail structures <NUM> are shown in the second, folded standing position (IIa). In the standing position, the longitudinal axis L of the wingsail structure (shown only in connection with one structure <NUM>) is essentially parallel with a general vertical axis V, which is perpendicular to a horizontal axis H of the vessel <NUM>. The horizontal axis H can extend substantially in the same direction as the deck floor. The wingsail structure also has an extension in a depth direction D, which is perpendicular to the plane formed by the two-dimensional longitudinal L and transversal T directions. The extension in the depth direction may increase when the flap is folded towards the main wingsail.

To provide the tilted position illustrated in <FIG>, the wingsail frame <NUM> having the longitudinal axis L extending in a vertical direction V when the wingsail frame is in a standing position IIa, is tilted around a transversal rotation axis RT, which is perpendicular to the longitudinal axis L and thus essentially horizontal. The arrow RT illustrates the direction of the tilting in respect of the rotation axis RT and is shown in <FIG>, and in <FIG>. In the tilted position, the longitudinal axis L of the wingsail frame is thus essentially parallel with the horizontal axis H or nearly parallel. The tilting can be obtained by a tilting arrangement <NUM> comprised in the wingsail structure <NUM>.

A non-limiting schematical example of the tilting arrangement <NUM> suitable for bringing the wingsail frame <NUM> from the second, standing position (II) to a third tilted stowage position (IIIa) is shown in <FIG>. The tilting arrangement <NUM> is associated with the foundation <NUM> and the shaft <NUM>, which is connected to the wingsail frame <NUM> via the main wingsail <NUM>. The shaft <NUM> is in its lower end <NUM> connected to a tilting means <NUM> having a rotation axis RT in respect of which the wingsail frame <NUM> can be tilted in the direction shown by the arrow RT. The tilting means <NUM> is in turn connected to the foundation <NUM> via the rotation axis RT. The tilting means <NUM> further comprises a locking means <NUM>, which prevents the tilting and fixes the shaft <NUM> and thus the wingsail frame <NUM> to a standing position. The locking means is released, when the wingsail frame <NUM> is to be tilted. The tilting arrangement <NUM> further comprises a tilting drive <NUM> comprising a tilting cylinder <NUM> connected to the foundation <NUM>. The tilting cylinder may be e.g. a hydraulic or pneumatic cylinder. On its second end, the tilting cylinder is rotatably connected to a moment shaft <NUM>, which is further connected to the shaft <NUM>. When the wingsail frame is to be tilted, the locking means is released. By driving the extension of the cylinder <NUM>, the moment shaft <NUM> pushes the shaft <NUM> to rotate in respect of the rotation axis RT. In this way, the wingsail frame <NUM> connected to the shaft <NUM> is tilted in respect of the rotation axis RT to the tilted position IIIa, in which the wingsail frame is stowed in a horizontal position, i.e. so that a side wall <NUM> or <NUM> of the main wingsail and the side wall <NUM> or <NUM> of the flap are facing towards the body of the vessel <NUM> and as shown in <FIG> and <FIG>. Alternatively, the tilting arrangement can be arranged to tilt the wingsail frame to a vertical upright position, in which the leading edge <NUM> or trailing edge <NUM> of the main wingsail <NUM> and the leading edge <NUM> or the trailing edge <NUM> of the flap faces towards the body of the vessel <NUM> and as shown in <FIG> and <FIG>. In this tilted vertical position IIIb, which is shown enlarged in <FIG> and <FIG> and in a view from bottom of the wingsail frame <NUM> in <FIG> and <FIG> the longitudinal axis L of the wingsail frame <NUM> is substantially parallel with the horizontal extension H of the body of the vessel <NUM>. The transversal axis T of the wingsail frame <NUM> is instead parallel with the vertical axis V in respect to the horizontal extension of the body <NUM> of the vessel. In this third vertical tilted position (IIIb), the footprint of the wingsail structure <NUM> on the deck of the vessel can be further decreased, which is a huge advantage. The vertical tilted position (IIIb) can be obtained also by rotating the tilted wingsail structure <NUM> from the horizontal tilted position (Illa) shown in <FIG> to the vertical tilted position (IIIb). Another variant is to arrange the wingsail structure with means that enable rotation of the wingsail frame around its longitudinal axis (I) during the tilting. Alternatively, the wingsail frame may be rotated from a horizontal to a vertical storage position, or vice versa, when it is tilted.

It should be noted that in the drawings <FIG>, <FIG>, <FIG> and <FIG> that illustrate the vertical tilted positions (IIIb), the foundation is separated from the shaft <NUM> due to illustration means. However, it is clear that the foundation <NUM> and the shaft <NUM> may be connected to each other also when tilted, for example via the tilting means <NUM>, which is the case when using the above-described tilting arrangement <NUM>. Additionally, or alternatively, other connecting means or additional rotation meanscould be used.

Returning to <FIG> and <FIG>, an embodiment of the wingsail frame according to the invention with upper and lower coupling members <NUM>, <NUM> is shown more in detail. Each of the upper and lower coupling members <NUM>, <NUM> in the shown embodiment are configured to provide a second axis of rotation <NUM> for rotating the flap <NUM> in respect to the upper and lower coupling members <NUM>,<NUM>. In the shown embodiment, the upper and lower coupling members <NUM>, <NUM> are additionally configured to provide a third axis of rotation <NUM> for rotating the main wingsail <NUM> in respect to the upper and lower coupling members <NUM>, <NUM>. Further, the upper and lower coupling members <NUM>, <NUM> are connected to the respective top end <NUM>, <NUM> and a bottom end <NUM>, <NUM> of the main wingsail <NUM> and the flap <NUM>. The lower coupling member is configured to provide the first axis of rotation <NUM> for rotating the wingsail frame <NUM> in respect to the foundation <NUM>. The first axis of rotation <NUM> is offset of the third axis of rotation <NUM> for rotating the main wingsail <NUM>. The first axis of rotation <NUM> is located between the third axis of rotation <NUM> and the second axis of rotation <NUM>. Each of the first, second and third axes of rotation extends in the longitudinal direction L of the wingsail frame <NUM>. Any commercially known means for providing the rotation axes can be used, such as commercially known shafts, bearings, etc. By having the first <NUM>, second <NUM> and third <NUM> axes of rotation as independent rotation axes, the loads can be transferred from the wingsail profiles to the vessel interface.

The upper and lower coupling members <NUM>, <NUM> may have a substantially similar shape, which extends from a point in proximity of the third axis of rotation <NUM>, located in proximity of the leading edge <NUM> of the main wingsail <NUM>, to a point in proximity of the second axis of rotation <NUM>, located in proximity of the leading edge <NUM> of the flap <NUM>. The shape of the coupling members may resemble a shape of an aerofoil or may have another shape accommodating to the transversal T and depth D extension of the coupling members and may thus be tapering in a direction from the main wingsail towards the flap. By providing the three individual rotating axes associated with the upper and lower coupling members, a robust connection of the main wingsail and flap is obtained while a flexible and fine adjustment of e.g. a camber provided by the wingsail frame is obtained.

Reference is now made to another embodiment of the wingsail frame shown in <FIG>. In an analogous manner as in connection with <FIG>, a marine vessel <NUM> comprising a wind-assisted propulsion arrangement <NUM> with three wingsail structures <NUM> is shown. Each of the wingsail structures <NUM> comprises a wingsail frame <NUM>, shown in more detail from above in <FIG>. The main wingsail <NUM> and a flap <NUM> are rigid or semi-rigid, meaning that there is a certain degree of flexibility, and are similar to the main wingsail and the flap already described in connection with <FIG>, and reference is made to the description above in this respect.

The wingsail frame <NUM> the embodiment of <FIG> differs from the one in <FIG> in respect of the shape and function of the upper coupling member <NUM> and the lower coupling member <NUM>, which are configured to rotatably connect the main wingsail <NUM> and the flap <NUM> in respect to each other. In the embodiment of <FIG>-10c, the upper and lower coupling members <NUM>, <NUM> are in addition to being configured to provide a second axis of rotation <NUM> for rotating the flap <NUM> in respect to the upper and lower coupling members <NUM>, <NUM>, also configured to provide a fourth axis of rotation <NUM> for rotating the flap <NUM> in respect to the main wingsail <NUM>.

The fourth axis of rotation <NUM> is associated with the main wingsail <NUM> to enable the rotation of the flap <NUM> in respect the main wingsail <NUM>. At the same time the upper and lower coupling members <NUM>, <NUM> may not be configured to provide the first rotation axis <NUM> for rotation of the wingsail frame in respect to the foundation. Instead, the first rotation axis <NUM> is associated with the shaft <NUM> connected to the bottom end <NUM> of the main wingsail <NUM>, for example as shown in <FIG>, <FIG> and <FIG> in connection with the rotation arrangement <NUM>. Thus, when the main wingsail <NUM> is rotated around the first rotation axis, the whole wingsail frame rotates. The coupling members <NUM>, <NUM> may in this embodiment comprise a link arm rotatable around the second axis of rotation <NUM> and fourth axis of rotation <NUM>.

<FIG> illustrates a the wingsail structure <NUM> in a view from above, when the wingsail frame is arranged in a first unfolded, propulsive, standing position (I). As can be seen, the main wingsail <NUM> and the flap form a camber having a convex arc-shape to provide a desired propulsion force. The flap <NUM> can be rotated from a first unfolded standing position (I) in respect of a second vertical rotation axis <NUM>, as shown by an arrow R in <FIG>, towards the main wingsail <NUM> to a second folded standing position (IIa) as shown in <FIG>. In this second folded position (IIa) the side wall <NUM> on the right-hand side of the flap <NUM> is folded towards the side wall <NUM> on the right-hand side of the main wingsail <NUM>, but the flap <NUM> could be alternatively folded in the opposite direction so that the side wall <NUM> of the flap <NUM> is folded towards the sidewall <NUM> of the main wingsail <NUM>. In this second folded position (Ila), the flap <NUM> faces the main wingsail <NUM> in an opposite direction, i.e. the leading edge <NUM> of the flap faces substantially opposite direction compared to the leading edge <NUM> of the main wingsail <NUM>. By folding the flap towards the main wingsail, the transversal extension T of the wingsail frame <NUM> can be reduced.

<FIG> shows a further variant of folding obtained by the fourth axis of rotation <NUM> which is provided in the upper and lower coupling members <NUM>, <NUM>. The flap <NUM> can be rotated from the first unfolded standing position (I) around a second vertical rotation axis <NUM> also in a counter clockwise (or clockwise) direction compared to the clockwise direction shown by the arrow R in <FIG>. At the same time, the upper and lower coupling means <NUM>, <NUM> are rotated in respect of the fourth rotation axis <NUM> in the clockwise direction so that the flap is rotated with the side wall <NUM> facing towards the side wall <NUM> of the main wingsail. Also, the trailing edges <NUM> and <NUM> of the main wingsail and the flap <NUM> are brought into proximity of each other. In this second folded position (IIb), the flap <NUM> faces the main wingsail <NUM> in the same direction. The transversal extension T of the wingsail frame <NUM> can be further reduced by this second folded position (IIb) compared to the second folded position (IIa).

By the "same direction" is meant the principal alignment of the main wingsail and the flap, i.e. that the leading and trailing edges are mainly pointing at a direction within <NUM> degrees.

Reference is now made to a further embodiment of the wingsail frame shown in <FIG>. In an analogous manner as in connection with <FIG>, the wingsail structure <NUM> comprises a wingsail frame <NUM> comprising a main wingsail <NUM> and a flap <NUM>, which are rigid or semi-rigid, and are similar to the main wingsail and the flap already described in connection with<FIG> and reference is made to the description above in this respect.

The wingsail frame <NUM> of the embodiments shown in <FIG>-10c differ from the one in <FIG> mainly in respect of the shape and function of the upper coupling member <NUM> and the lower coupling member <NUM>, which are configured to rotatably connect the main wingsail <NUM> and the flap <NUM> in respect to each other. In the embodiment of <FIG> and <FIG>, the upper and lower coupling members <NUM>, <NUM> are in addition to being configured to provide a second axis of rotation <NUM> for rotating the flap in respect to the upper and lower coupling members <NUM>, <NUM>, also configured to provide a fourth axis of rotation <NUM> for rotating the flap <NUM> in respect to the main wingsail <NUM>.

Reference is made to the embodiment shown in <FIG>, in which the upper and lower coupling members <NUM> and <NUM> are attached to the respective top end <NUM>, <NUM> of the main wingsail <NUM> and the flap <NUM> and to the respective bottom end <NUM>, <NUM> of the main wing <NUM> and the flap <NUM>. The coupling members extend between the second axis of rotation <NUM> associated with the flap <NUM> and the fourth axis of rotation <NUM> associated with the main wingsail <NUM>. By having the coupling members connected to the second and fourth axes of rotation <NUM>, <NUM>, the rotation of the flap <NUM> around the main wingsail <NUM> is enabled. At the same time the upper and lower coupling members <NUM>, <NUM> are not configured to provide the first rotation axis <NUM> for rotation of the wingsail frame <NUM> in respect to the foundation. Instead, the first rotation axis <NUM> is associated with the bottom end <NUM> of the main wingsail <NUM>, for example as shown in connection with the rotation arrangement <NUM> in <FIG>. Thus, when the main wingsail <NUM> is rotated around the first rotation axis <NUM>, the whole wingsail frame <NUM> rotates. The coupling members <NUM>, <NUM> may in the embodiment of <FIG> comprise a link arm. The link arm may be configured to be rotatable around the second and fourth rotational axes <NUM>, <NUM> and may be connected to the second and fourth rotational axes <NUM>, <NUM>.

Reference is made to the embodiment shown in <FIG>, in which the upper and lower coupling members <NUM> and <NUM> are attached to the trailing edge <NUM> of the main wingsail and the leading edge of the flap <NUM>. The upper and lower coupling members <NUM> and <NUM> are attached at a distance from the respective top end <NUM>, <NUM> of the main wingsail <NUM> and the flap <NUM> and to the respective bottom end <NUM>, <NUM> of the main wingsail <NUM> and the flap <NUM>. There is an additional coupling member <NUM> attached between the upper and lower coupling members <NUM> and <NUM>. , and it should be noted that more than one additional coupling member can be used between the upper and the lower coupling members <NUM>, <NUM>. The coupling members <NUM>, <NUM> and <NUM> extend between the second axis of rotation <NUM> associated with the flap <NUM> and the fourth axis of rotation <NUM> associated with the main wingsail <NUM>. To facilitate the folding of the flap <NUM> to the second folded position (IIa), the coupling members <NUM>, <NUM> and <NUM> may have a shape of a bent link arm. The link arm may be fitted to a recess in the respective main wingsail and flap and attached by suitable means to the side walls <NUM>, <NUM>, <NUM>, <NUM> of the main wingsail and the flap. Also in this variant, the coupling members <NUM>, <NUM> and <NUM> are not configured to provide the first rotation axis <NUM> for rotation of the wingsail frame <NUM> in respect to the foundation. Instead, the first rotation axis <NUM> is associated with the bottom end <NUM> of the main wingsail <NUM>, for example as shown in connection with the rotation arrangement <NUM> in <FIG>. Thus, when the main wingsail <NUM> is rotated around the first rotation axis <NUM>, the whole wingsail frame <NUM> rotates.

The wind-assisted propulsion arrangement <NUM> may be operated according to a method comprising the steps of:.

Claim 1:
A wingsail structure (<NUM>) for a wind-assisted propulsion arrangement (<NUM>) of a marine vessel (<NUM>), the wingsail structure (<NUM>) comprising:
- a wingsail frame (<NUM>) comprising:
∘ a rigid or semi-rigid main wingsail (<NUM>) having an aerofoil shape with a leading edge, a trailing edge, a top end (<NUM>) and a bottom end (<NUM>), and side walls (<NUM>; <NUM>) extending therebetween,
∘ a rigid or semi-rigid flap (<NUM>) having an aerofoil shape with a leading edge, a trailing edge, a top end (<NUM>) and a bottom end (<NUM>), and side walls (<NUM>; <NUM>) extending therebetween,
∘ at least one upper coupling member (<NUM>) and at least one lower coupling member (<NUM>) connecting the main wingsail and the flap,
- a foundation (<NUM>) arranged to be fixed to a body (<NUM>) of the vessel (<NUM>), the foundation being associated with the wingsail frame such that the wingsail frame is rotatable in respect to the foundation via a first vertical axis of rotation (<NUM>),
wherein the upper and lower coupling members (<NUM>; <NUM>) are configured to:
- bring the main wingsail and the flap to a first unfolded standing position (I), and
- bring the main wingsail and the flap towards one another to a second folded standing position (IIa; IIb) to reduce generated forces and the space required by the wingsail frame on board of the vessel, and where the main wingsail and the flap are in an overlapping position when looking in a transversal plane when in the second folded standing position, and
wherein the wingsail structure (<NUM>) further comprises a tilting arrangement (<NUM>) configured to bring the wingsail frame (<NUM>) from the second folded standing position (IIa; IIb) to a third tilted position (IIIa; IIIb) in respect to the foundation.