Sail body for forming part of a wind power assist propulsion device

Abstract

A method of manufacturing a sail body (3) for forming part of a wind power assisted propulsion device (4) includes laying a first fabric (14) formed from a first fiber on a mold (16) defining the shape of a part (2) of the sail body (3), and laying a plurality of strips (22) formed from a second fiber on the surface of the first fabric (14) such that at least a part of the second fiber extends longitudinally along the sail body (3).

Description

Technical Field

[0001] The present invention relates to a sail body for forming part of a device for wind-aided propulsion of an object, in particular, but not limited to, for wind-aided propulsion of a ship or vessel. The present invention also relates to a method of forming such a sail body and a ship incorporating such a sail body.

[0002] Wind-aided propulsion devices such as rotor sails, wing sails, and suction sails are subject to similar loads during use and thus similar characteristics are required.

[0003] In the following, the present invention will be mainly described with respect to rotor sails. However, it should be understood that this is for illustrative purposes only and in no way limits the scope of the present invention to rotor sails only.

Background Art

[0004] Rotor sails are also known as Flettner rotors. Known rotor sails typically include a cylindrical sleeve that forms the sail or sail body. This sleeve is adapted to rotate on a stationary tower. Upper and lower bearings position the rotor on the tower. The wind load acts on the sail body and is typically seen as a reduction in air pressure on one side of the sail body known as the suction side. The air pressure distribution has two main structural effects. · A bending moment is applied to the entire sail body (i.e., it acts as a beam with a circular hollow cross-section receiving a distributed load). This causes stresses in the plane of the sail skin, mainly resulting in tension and compression in the rotor axis direction due to the bending moment, and some in-plane shear due to the accompanying shear forces. · Due to the non-uniform distribution of air pressure around the cross-section, the circular cross-section tends to distort due to local bending moments on the rotor skin. This mainly causes tensile and compressive stresses in the circumferential direction around the sail body.

[0005] During the lifespan of a rotor sail, the large stresses applied to the sail body fluctuate or even reverse with each rotation. The number of rotations during the lifespan of a rotor sail is very high, approximately several billion times. This means that the known sail bodies are made of materials that are resistant to fatigue failure. Composite materials obtained by laminating continuous glass fibers or carbon fibers in a polymer resin are known to be suitable for this application.

[0006] To provide strength to the rotor, it is necessary to align the fibers of the composite material used in the manufacture of the sail body with the principal stresses applied to the sleeve during sail use. This is because the fibers of the composite material provide maximum strength throughout the sail body.

[0007] In known rotor sails, approximately 50% of the total strength needs to be in the longitudinal direction, i.e., it needs to coincide with the sail axis, and approximately 30% of the total strength needs to be derived from fibers oriented approximately circumferentially / transversely, i.e., fibers wound around the sail axis.

[0008] The remaining material provides resistance to in-plane shear stress, but due to the inherent shear and torsional resistance of the large-diameter tubes of the type that form part of the rotor sail, the in-plane shear stress of the rotor sail is relatively small.

[0009] Furthermore, there is also a requirement that the circumferentially / transversely oriented fibers need to be as far as possible from the central plane or neutral axis of the laminated material forming the sail body. Such a configuration provides optimal bending strength in the circumferential / transverse direction. This helps to resist local bending moments that tend to distort the intended cross-section of the sail body.

[0010] The circumferential / transverse bending stiffness is also beneficial for resisting buckling of the sail body.

[0011] Since cylindrical and other similar-shaped sails have a naturally high resistance to axial buckling due to the curvature of the cylindrical surface, the sail body is more prone to buckling in the circumferential / transverse direction than in the axial / longitudinal direction.

[0012] A known method for forming composite materials is resin infusion, also known as VARTM (Vacuum Assisted Resin Transfer Moulding). This method reduces material costs and is quite economical for the mass production of wind turbine blades.

[0013] In a typical known rotor sail manufactured using the resin infusion method, a composite material with a sandwich structure having a foam core in the center of the composite structure is used. The foam core separates the outer layers and provides the required bending strength in the circumferential / transverse direction. The disadvantages of this method include the following. · In the resin infusion method, no tension is applied to keep the fibers straight while the resin cures, which means that the compressive strength of the material is lower, and thus more material is required than if the fibers were kept straighter. · The foam core is relatively expensive in terms of both material costs and labor, and also absorbs a significant amount of resin, increasing the weight of the part and further adding to the cost.

[0014] For example, in the case of a rotor sail, to achieve a sufficient fatigue life, it is necessary to keep the typical operating strain below about 0.15% in both the axial and circumferential directions.

[0015] Therefore, there is a need for an economical method of forming composite materials to form a wind power assist propulsion device having the required axial / longitudinal and circumferential / transverse strength. SUMMARY OF THE INVENTION

[0016] According to a first aspect of the present invention, there is provided a method of manufacturing a sail body for forming a part of a wind power assist propulsion device, the method comprising: laying a first fabric formed from a first fiber on a mold defining a shape of a part of the sail body; Laying a plurality of strips formed from the second fiber on the surface of the first fabric such that at least a portion of the second fiber extends longitudinally along the sail body.

[0017] The plurality of strips include second fibers that extend longitudinally along the resulting sail body, thereby providing the axial / longitudinal strength required for a wind-assisted propulsion device, particularly a rotor sail.

[0018] On the other hand, the first fabric can include fibers that ultimately extend around the sail body to provide circumferential / transverse strength. Thus, both circumferential and axial strength are provided to the sail body.

[0019] Accordingly, embodiments of the present invention can manufacture a sail body having suitable strength for use in a wind-assisted propulsion device at a relatively low cost.

[0020] The mold can be a female mold, which means the shape is concave, or a male mold, which means the shape is convex. In the case of the female mold, the strips are laid on the concave surface of the first fabric. Conversely, in the case of the male mold, the strips are laid on the convex surface of the first fabric.

[0021] In embodiments of the present invention, the method Introducing resin into the first fabric and optionally into and / or between the plurality of strips. Heating the mold to cure the resin.

[0022] In such embodiments of the present invention, the first fabric, the plurality of strips, and the cured resin can form a sail body portion for forming the sail body. Thus, in such embodiments of the present invention, it is preferable to use a female mold so that the strips are disposed on the inner surface of the sail body and the outer surface can be smoothed.

[0023] The advantage of forming one or more sail body parts in this way is that, in accordance with changes in the bending moment, the number of strips can be varied along the length of the sail body (by adding more strips in different regions or by spacing the strips apart), thereby minimizing the total weight and cost of the axial material.

[0024] Also, more expensive carbon fiber strips of a practical thickness can be used cost - effectively instead of glass fibers. This is because they can be spread apart rather than being adjacent in a continuous layer. Carbon fibers are advantageous because they are stronger, lighter, and have particularly better fatigue resistance than glass fibers. The strength advantage of carbon fibers is particularly prominent when they are drawn because the linearity of the fibers is beneficial. Therefore, even if the carbon fiber material is more expensive per kg, using carbon fibers in the axial / longitudinal direction of the sail body may be more cost - effective than using glass fibers.

[0025] The introduction of the resin can be carried out either before or after laying the plurality of strips on the first fabric. If the resin is introduced before the plurality of strips are laid, an additional step of joining the strips to the first fabric using a structural adhesive is required. Any suitable structural adhesive can be used.

[0026] Alternatively, if the resin is introduced after the strips have already been laid on the first fabric, the resin itself can join the strips to the fabric when it cures.

[0027] However, especially in the case of a rotor sail, a sail body formed only from the first fabric, the plurality of strips, and the cured resin has a non - uniform inner surface, which increases the resistance between the rotating sail body and the stationary tower and increases the power consumption of the motor.

[0028] Therefore, the method is The method may further include laying a second fabric formed from a third fiber on a plurality of strips.

[0029] This step can be carried out after introducing resin into the first fabric. However, laying the second fabric before introducing the resin is desirable to reduce the number of manufacturing steps required.

[0030] Thus, when the second fabric is added, the method includes introducing resin into the first fabric, the second fabric, and within and / or between the plurality of strips, and heating the mold to cure the resin. The first fabric, the plurality of strips, the second fabric, and the cured resin form a sail body portion for forming a sail body.

[0031] In such an embodiment of the present invention, the first fabric and the second fabric essentially sandwich the plurality of strips. Including the second fabric further improves the circumferential / transverse strength.

[0032] In an embodiment of the present invention, the method further includes forming a plurality of strips.

[0033] One or more of the plurality of strips can be formed using a drawing or draw-wrapping process.

[0034] The drawing process is suitable for producing a straight tube with a circular or any other hollow or solid cross-section in a single operation. Since the drawing process is automated, it is a low-cost process. Also, the raw materials are in the simplest form, i.e., liquid polymer resin and tows of glass fiber or carbon fiber, which are used directly from bobbins around which the tows are wound.

[0035] Tension is used to pull a profile through a die to form a strip of material. This has the advantage of axially orienting the fibers along the strip, maximizing the compressive strength of the material. A strip formed in such a way may be referred to as a drawn article.

[0036] Draw winding is similar to draw forming, except that some of the fibers used to form the draw-wound composite material are wound while being pulled through the die. As a result, a material is obtained that includes some straight fibers like those of a drawn material and some fibers oriented at an angle to provide greater strength in the transverse direction. The draw-wound material provides greater multi-directional strength but is also more expensive than the drawn material.

[0037] By using a draw forming or draw winding process, both the draw forming and draw winding processes can be automated, so that the sail body can be manufactured particularly efficiently.

[0038] Using a draw forming or draw winding process means that the strip can be formed to have any desired dimensions. In some embodiments of the present invention, the strip has a thickness of about 1 mm to about 10 mm, or about 1 mm to about 6 mm.

[0039] Both the first fabric and the drawn article can be made to any desired length.

[0040] In embodiments of the present invention, one or more of the plurality of strips can be formed to at least partially define a cavity within the sail body. In such embodiments of the present invention, the strip itself may be hollow. Alternatively, the strip may have a cross-sectional shape that defines a channel or groove. For example, the strip may have a U-shaped, V-shaped, or W-shaped cross-section. When laid on the first fabric, the open side of the channel or groove can be closed by the first fabric. Alternatively, the open side can be closed by laying a second fabric thereon.

[0041] The strip that at least partially defines a cavity within the sail body has an increased thickness in a direction perpendicular to the first fabric and does not have as much weight as a solid strip of equal thickness (i.e., a strip that does not form a cavity within the sail body).

[0042] When one or more cavities are provided within the sail body, the method may further include creating an opening that extends from the surface of the sail body portion to the cavity. Thereby, the cavity can be used as a channel for transporting air from the outside of the sail body to the suction mechanism within the wind power assisting propulsion device. Thus, the wind power assisting propulsion device can operate as a suction sail.

[0043] In an embodiment of the present invention, one or more of the plurality of strips are formed such that at least one end includes a taper, and preferably, the taper includes a concave surface. In other words, the thickness of one or more strips may taper towards one or both ends of the strip(s).

[0044] In an embodiment of the present invention, each strip of the plurality of strips may include a pair of shaped edges, and each shaped edge is formed to nest or engage with the shaped edge of an adjacent strip. Thus, the step of laying the plurality of strips on the surface of the first fabric may include nesting or engaging one or more of the shaped edges of the plurality of strips with or in relation to the shaped edges of adjacent strips.

[0045] Since each strip can function to hold its adjacent strip in a predetermined position, the shaped edges also make it possible to more easily position the strips on the first fabric.

[0046] As an alternative or additional means of holding the strip in place, laying a plurality of strips on the surface of the first fabric may include attaching the plurality of strips to the surface of the first fabric.

[0047] Attaching the plurality of strips to the surface of the first fabric may include pre - joining the strip to a backing scrim, using one or more rigid or flexible jigs to hold the plurality of strips against the first fabric, and, include at least one of weaving a fiber or a light fabric tape between the strips.

[0048] In an embodiment of the present invention, laying the plurality of strips may include laying the plurality of strips such that the average width of the area of the first fabric not covered by any strip (which may be referred to as the uncovered area) is less than 30% of the total width of the first fabric. Each width of the uncovered area is measured perpendicular to the strip, and the average width of the uncovered area is determined by all areas of the first fabric not covered by any strip.

[0049] It should be understood that the total width of the first fabric is defined by the shape of the first fabric when laid on the mold. This applies even when the first fabric is provided as a sheet that may have a width different from the width of the first fabric laid on the mold that defines part of the shape of the sail body. In other words, the total width of the first fabric is not necessarily the same as the width of the sheet of the first fabric that can be provided for laying on the mold.

[0050] The average width of the area of the first fabric not covered by any strip can be calculated by summing the total widths of all areas of the first fabric not covered by any strip and dividing that sum by the number of areas of the first fabric not covered by any strip.

[0051] Similarly, the step of laying a plurality of strips may include laying the strips so as to cover more than 30%, optionally more than 40%, preferably more than 50%, and more preferably more than 60% of the surface area of the first fabric.

[0052] In an embodiment of the present invention, the plurality of strips can form a first strip layer, and the method may further include the step of laying one or more additional pluralities of strips on at least a part of the first strip layer or on the second fabric to form one or more auxiliary strip layers.

[0053] In other words, the sail body portion is formed to include two or more layers of strips in at least a part of the sail body portion. Such additional strip layers can reinforce that part of the resulting sail body portion, particularly in the axial / longitudinal direction.

[0054] Each additional strip layer may be thinner or thicker than the first strip layer, depending on the required level of additional reinforcement.

[0055] Such an embodiment of the present invention may further include the step of laying an intermediate fabric on at least a part of the laid strip layer before laying an additional strip layer on at least a part of the laid strip layer.

[0056] This can be advantageous because the resin can penetrate all the gaps between the strips and help fill them.

[0057] To form a complete sail body, two or more sail body portions can be joined to each other.

[0058] The method may also further include the step of attaching one or more circumferential ribs to the inner surface of one or more sail body portions before or after joining the sail body portions to each other to form the sail body. The circumferential ribs can further reinforce the sail body.

[0059] In an embodiment of the present invention, the wind-assisted propulsion device may be a wind-assisted ship / ship propulsion device, and preferably, it may be one of a rotor sail, a wing sail, and a suction sail.

[0060] In an embodiment where the wind-assisted propulsion device is a rotor sail, the sail body may be a rotor sail body, and the shape may include a substantially semi-cylindrical surface.

[0061] According to a second aspect of the present invention, a sail body for forming a part of the wind-assisted propulsion device is provided. The sail body includes a plurality of sail body parts joined to each other to form the sail body, and each sail body part a first skin formed from a first fiber material formed from a first fiber, and a plurality of strips extending longitudinally along the sail body. Each strip is formed from a second fiber material formed from a second fiber, and at least a part of the second fiber extends longitudinally along the sail body.

[0062] The features and advantages of the first aspect of the present invention and its embodiments are mutatis mutandis applicable to the second aspect of the present invention and its embodiments.

[0063] The first fiber material may include a first fabric and a cured resin formed according to an embodiment of the first aspect of the present invention.

[0064] In some embodiments of the present invention, each sail body part may further include a second skin formed from a third fiber material formed from a third fiber, and the plurality of strips are disposed between the first skin and the second skin. The third fiber material may include a second fabric and a cured resin formed according to an embodiment of the first aspect of the present invention.

[0065] In an embodiment of the present invention, the second fiber may be glass fiber and / or carbon fiber.

[0066] One or more of the plurality of strips may be a strip of drawn or drawn-wound material, may have a thickness of about 1 mm to about 10 mm, or about 1 mm to about 6 mm, and / or in a direction perpendicular to the first skin, may have a thickness of at least twice the thickness of the first skin, preferably at least three times the thickness of the first skin, more preferably at least four times the thickness of the first skin.

[0067] In an embodiment of the present invention, one or more of the plurality of strips may define a cavity within the sail body. In such an embodiment of the present invention, the sail body may include one or more openings extending from the surface of the sail body portion to the cavity.

[0068] In an embodiment of the present invention, one or more of the plurality of strips have a substantially rectangular or substantially trapezoidal cross-sectional shape that is curved to substantially follow the shape of the sail body.

[0069] Substantially rectangular strips can be manufactured more inexpensively due to their simplicity. However, due to the curved shape of the sail body portion, the rectangular shape may prevent the strips from optimally fitting next to each other and adjacent to the skin (or skins) of the sail body portion.

[0070] Thus, strips having a substantially trapezoidal shape may be preferred because they can reduce the gaps between adjacent strips and between the strips and the skin(s). This means that less resin is required to fill the gaps, thereby reducing the weight of the sail body portion and reducing material costs.

[0071] Strips having a cross-sectional shape that is curved to substantially follow the shape of the sail body may be even more preferred because they can further reduce the size of the gaps.

[0072] Additionally or alternatively, each strip of the plurality of strips includes a pair of profiled edges, each profiled edge being shaped to nest or engage with the profiled edges of adjacent strips. The profiled edges can also reduce the size of the gaps between strips that are arranged side by side or engaged with each other, thereby similarly reducing the amount of resin required to fill those gaps, and thus reducing the weight of the resulting sail body and also reducing the material cost.

[0073] As described above with respect to the embodiment of the first aspect of the present invention, the profiled edges can also improve the ease of manufacture of the sail body portion.

[0074] In an embodiment of the present invention, one or more of the plurality of strips may include at least one end portion including a taper, preferably, the taper includes a concave surface.

[0075] The taper reduces stress concentration in the strips, particularly in the resin between the strips. The concave surface of the taper can further reduce stress concentration.

[0076] In an embodiment of the present invention, the sail body portion may be configured such that the average width of any region of the sail body portion without strips in a direction perpendicular to the first skin is less than 30% of the total width of the first skin measured perpendicular to the strips.

[0077] Similarly, in some embodiments of the present invention, the sail body portion may be configured such that the strips cover more than 30%, optionally more than 40%, preferably more than 50%, and more preferably more than 60% of the surface area of the first skin.

[0078] In an embodiment of the present invention, the first skin and / or the second skin can have a thickness of about 1 mm to about 4 mm. Also, the first fiber and / or the third fiber may be glass fiber.

[0079] The sail body can be regarded as having a sail shaft that penetrates the sail body in the longitudinal direction. In an embodiment of the present invention, the first fiber and / or the third fiber may be oriented at more than 45 degrees, preferably more than 55 degrees, with respect to the sail shaft.

[0080] The number of strips may vary along and / or around the sail body.

[0081] According to a third aspect of the present invention, there is provided a sail body according to an embodiment of the second aspect of the present invention, formed using the method according to an embodiment of the first aspect of the present invention.

[0082] The features and advantages of the first and second aspects of the present invention and their embodiments shall apply mutatis mutandis to the third aspect of the present invention and its embodiments.

[0083] According to a fourth aspect of the present invention, there is provided a ship, which includes a wind-assisted propulsion device attached to a part of the ship, and this wind-assisted propulsion device includes a sail body according to an embodiment of the second or third aspect of the present invention.

[0084] The features and advantages of the foregoing aspects of the present invention and their embodiments shall apply mutatis mutandis to the fourth aspect of the present invention and its embodiments.

[0085] Hereinafter, the present invention will be described by way of example with reference to the accompanying drawings.

Brief Description of the Drawings

[0086]

Figure 1

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Embodiments for Carrying Out the Invention

[0087] Referring now to FIG. 1, an example of a wind-assisted propulsion device that can be formed in accordance with an embodiment of the first aspect of the present invention is shown. More specifically, a rotor sail or a Flettner rotor is shown, where the rotor sail is generally defined by reference numeral 4. The rotor sail 4 includes a sail body 3 rotatably attached to a stationary tower 6 via an upper bearing 8 and a lower bearing 10 so as to be rotatable about a sail axis 18. The sail body 3 includes a plurality of circumferential ribs 5 that reinforce the sail body 3 and provide circumferential bending strength and bending rigidity. In this example, the circumferential ribs 5 are attached to the inside of the sail body 3, but the circumferential ribs may be attached to the outside of the sail body.

[0088] FIGS. 2, 3, and 5 show the steps of a method of forming a portion of a sail body such as the sail body 3 shown in FIG. 1. However, it should be understood that this method is equally suitable for forming a portion of a sail body used in other wind-assisted propulsion devices such as wing sails or suction sails.

[0089] In particular, FIG. 2 shows a first fabric 14 formed from a first fiber laid on a mold 16.

[0090] In this embodiment of the present invention, the mold 16 is a female mold, which means that the shape is concave. The mold 16 also defines the shape of a portion of the sail body 3. More specifically, the mold 16 defines a substantially semi-cylindrical shape, enabling the formation of a substantially semi-cylindrical sail body portion, and this substantially semi-cylindrical sail body portion can be joined to another substantially semi-cylindrical sail body portion to form a substantially cylindrical sail body 3.

[0091] The first fiber can be any suitable material such as, for example, carbon, aramid, basalt, E-glass, S-glass, or ECR-glass.

[0092] The orientation of the first fiber with respect to the sail axis 18 is determined by the orientation in which the first fiber is woven into the first fabric 14 and the orientation in which the first fabric is laid on the mold 16 with respect to the sail axis 18. At least a part of the first fiber may be oriented at more than 45 degrees, preferably more than 55 degrees, with respect to the sail axis 18. For example, the first fiber may have an orientation of ±45 degrees and 90 degrees with respect to the sail axis 18, 0 degrees, ±45 degrees and 90 degrees with respect to the sail axis 18, or ±60 degrees with respect to the sail axis 18.

[0093] To form the sail body for a rotor sail with a diameter of 4 m to 5 m and a height of 25 m to 35 m, the first fabric 14 may be, for example, an E-glass / epoxy-based fabric with a thickness of 1 mm to 4 mm. Since such fabrics are usually provided in sheets with a width of about 1.2 m to 1.5 m, they can be laid in strips along or across the mold 16. For the structural continuity across the sail body portion, adjacent fabric strips may overlap by 30 mm to 100 mm.

[0094] Figure 3 shows a plurality of strips 22 laid on the first fabric 14. The strips 22 are formed from a second fiber and are arranged on the first fabric 14 such that at least a part of the second fiber extends longitudinally along the first fabric 14, that is, longitudinally along the resulting sail body 3. The second fiber can be any suitable material such as, for example, carbon, aramid, basalt, E-glass, S-glass, or ECR-glass. Each strip 22 may be formed using a pultrusion or pultrusion winding process.

[0095] To form the sail body for a rotor sail with a diameter of 4 m to 5 m and a height of 25 m to 35 m, each of the plurality of strips may be, for example, 1 mm to 6 mm thick (in a direction perpendicular to the first fabric).

[0096] Attachment means can be used to attach the plurality of strips to the surface of the first fabric 14 so that they remain in place until the plurality of strips 22 are fixed to the first fabric 14 at a later stage of the method. This may be necessary, in particular, to prevent the upper strip 22 (on the substantially vertical side of the female mold) from falling into the mold 16.

[0097] In this embodiment of the invention, as shown in FIG. 4, the strips are pre - joined to a backing scrim 26. Thus, the plurality of strips 22 can be attached to the first fabric 14 as a single assembly rather than as individual strips. This is similar to, for example, mosaic tiles for bathrooms and kitchens, which, because they are attached to a backing layer, can be attached to the wall as a large sheet rather than as individual tiles.

[0098] Using the backing scrim 26 can simplify attaching the strip 22 to the first fabric 14, especially when using a male mold, to prevent the strip from falling off the side of the mold. However, the process of pre - joining the strip 22 to the backing scrim 26 requires additional process steps.

[0099] In other embodiments of the invention, the strip 22 can be held in place on the first fabric 14 using a rigid or flexible jig adapted to ensure the desired spacing of the strips on the first fabric 14. In a further embodiment of the invention, fibers of a light cloth tape can be woven between the strips to hold the strips in place on the first fabric 14.

[0100] In FIG. 5, a second fabric 34 formed of a third fiber is laid over the plurality of strips 22.

[0101] Similar to the first fiber, the third fiber can be any suitable material such as carbon, aramid, basalt, E-glass, S-glass, or ECR-glass. To form the sail body for a rotor sail with a diameter of 4 m to 5 m and a height of 25 m to 35 m, the second fabric 34 may be an E-glass / epoxy-based fabric with a thickness of 1 mm to 4 mm, similar to the first fabric 14.

[0102] The third fiber may also be oriented in the same way as the first fiber.

[0103] In some embodiments of the present invention, it may be beneficial to incorporate axial / longitudinal fibers oriented at approximately 0 degrees with respect to the sail axis into one or both of the first and second fabrics 14, 34. Preferably, such fibers are incorporated into the second fabric 34, thereby preventing the fibers from causing distortion in the path of the strip 22 within the mold. The axial / longitudinal fibers can be incorporated as a unidirectional material or, if there are also high stresses in other directions, as a multi-axial material such as 0 / 45 / 90 / -45 four-axis.

[0104] The first fabric 14, the plurality of strips 22, and the second fabric 34 form a laminated structure clearly shown in FIG. 6. To fix these components to each other, resin is introduced into the laminated structure while they are in predetermined positions on the mold 16, and then the mold 16 is heated to cure the resin.

[0105] One suitable method of introducing the resin is the injection process. However, other suitable processes for introducing the resin can also be used.

[0106] To carry out the resin injection process, sealing means including a vacuum bag and other consumables can be laid on the first fabric 14, the plurality of strips 22, and the second fabric 34 while they are in predetermined positions on the mold 16 and sealed around the edges. Next, air is sucked out of the sealed laminated structure and the resin is injected. When the resin has cured, part or all of the sealing means can be removed to form the sail body portion, which can then be removed from the mold 16.

[0107] The resin can be any suitable type of resin, such as, for example, an epoxy resin, a vinyl ester resin, a polyester resin, a polyurethane resin, or an acrylic resin. The resin may be thermosetting or thermoplastic and can be cured at ambient temperature or elevated temperature to suit the speed required for the process and the ultimate strength and temperature resistance required for the rotor body in use that forms part of the rotor sail. For example, the resin may be an epoxy resin. Thereafter, by raising the temperature of the complete rotor body, the resin and any adhesives used in the manufacture of the sail body 3 can be further cured (post-cured) to increase the degree of cure of the resin and further improve its strength and temperature resistance.

[0108] The advantage of using the female mold is that the surface of the sail body part 2 that ultimately forms the outer surface of the sail body 3 contacts the surface of the mold during the manufacturing process. The surface of the mold 16 may be smooth, and thus the cured resin forming the outer surface of the sail body will reflect the smoothness of the mold 16. Thus, by using the female mold, a sail body 3 having a smooth surface can be formed, improving the performance of the wind propulsion device.

[0109] Referring now to FIG. 7, a possible sail body part 2 formed using the above method is shown in cross-section. The sail body part 2 includes a first skin 12, a plurality of strips 22, and a second skin 32, with resin 20 joining the skin and the strips to each other. The first skin 12 is formed from a first fiber material formed from a first fiber, for example, a first fabric 14 (shown in FIGS. 2, 3, 5, and 6) into which resin has been infused. Similarly, the second skin 32 is formed from a third fiber material formed from a third fiber, for example, a second fabric 34 (shown in FIGS. 5 and 6) into which resin has been infused.

[0110] In this embodiment of the invention, each strip 22 is a strip of drawn material, which is a strip of material formed by a drawing process.

[0111] In another embodiment of the present invention, each strip may be a strip of drawn-wound material, which is a strip of material formed by a drawn-winding process.

[0112] In a further embodiment of the present invention, other suitable types of fibrous materials can be used.

[0113] Each strip 22 has a substantially rectangular cross-sectional shape, and its edges are in contact with the edges of adjacent strips 22. The resin 20 fills any gaps between adjacent strips 22 and between the first skin 12, the plurality of strips 22, and the second skin 32, and functions to join the first skin 12, the plurality of strips 22, and the second skin 32 to each other.

[0114] The first and second skins 12, 32 each include first and third fibers oriented at more than 45 degrees with respect to the sail axis. The orientation of the first and third fibers provides circumferential / hoop direction strength perpendicular to the sail axis to the sail body portion 2, so that as a result, the sail body including one or more sail body portions 2 can maintain its intended cross-sectional shape when used as part of a wind-assisted propulsion device. On the other hand, the strip 22 including the second fibers (at least a part of which is oriented parallel to the sail axis) provides axial strength parallel to the sail axis to the sail body portion 2, so that as a result, when in use, the sail body including the sail body portion 2 can withstand the bending force caused by the pressure from the wind.

[0115] The resin 20 joins the various components of the sail body to each other, but reducing the amount of resin used can advantageously reduce the material cost and the weight of the resulting sail body. Therefore, it may be desirable to avoid using more resin than is necessary to join the layers of the sail body portion to each other.

[0116] Accordingly, FIG. 8 shows a sail body portion 102 similar to the sail body portion 2 shown in FIG. 7, except that each of the plurality of strips 122 has an arcuate cross-sectional shape, such that the strips 122 can fit more closely with the first and second skins 12, 32. Also, the edges of the strips 122 are angled, such that each strip 122 can fit more closely with an adjacent strip 122. Accordingly, the space between adjacent strips 122, and the space between the first skin 12, the plurality of strips 122, and the second skin 32, is reduced as compared to the sail body portion 2 shown in FIG. 7. Accordingly, there may be less resin 20 required to fill the space and join the components of the sail body portion to each other. Accordingly, the sail body portion 102 can be manufactured at a lower material cost and with less weight.

[0117] The strips can also be shaped to improve the ease with which they are laid on and retained on the first fabric 14 during the formation of the sail body portion. For example, FIG. 9 shows a sail body portion 202 that can form part of a sail body according to another embodiment of the second aspect of the present invention, which includes a plurality of strips 222. Each strip 222 has a profiled edge 229 shaped to nest with a profiled edge 229 of an adjacent strip 222. Thereby, each strip 222 encourages its adjacent strip 222 to stay in place, and can reduce the burden on the manufacturer to hold the strip 222 in place.

[0118] Similarly, FIG. 10 shows a sail body portion 302 that includes a plurality of strips 322 that include profiled edges 329 that engage with profiled edges 329 of adjacent strips 322.

[0119] Despite the circumferential bending strength being improved by the strip layer between the skins, it is usually necessary to reinforce the sail body with circumferential ribs (such as the circumferential rib 5 shown in FIG. 1) to provide the required circumferential bending strength and bending stiffness. In some embodiments of the present invention, these ribs can be attached to the inside of the sail body at intervals of about 0.5 to 1.5 times the diameter or chord of the sail. Therefore, in the case of a typical rotor sail, 3 to 15 ribs arranged at intervals along the length of the sail body may be optimal.

[0120] Referring now to FIG. 11, a sail body portion 402 that can form part of a sail body according to another embodiment of the second aspect of the present invention includes a plurality of strips 422. The sail body portion 402 is similar to the sail body portion 2 shown in FIG. 7, except that each strip 422 is a hollow strip that includes a cavity 28.

[0121] Since each strip has a cavity, the strip can be formed with a larger cross-sectional area while using the same amount of material and thus having the same weight. Therefore, in the sail body portion 402, the first skin 12 and the second skin 32 may be further apart compared to the skin of the sail body portion 2 shown in FIG. 7. By increasing the distance between the first skin 12 and the second skin 32, the circumferential bending strength and bending stiffness of the sail body portion 402 can be increased without adding the parasitic cost or weight of the foam core or increasing the material cost or weight of the strip. This improvement in bending strength and bending stiffness can reduce or avoid the need for circumferential ribs.

[0122] During the manufacture of the sail body portion 402, particularly before the introduction of the resin, it may be necessary to prevent the resin from filling the cavity. This can be done by any suitable means, such as closing the open ends of the strip 422.

[0123] In FIG. 12, the sail body portion 502 is similar to the rotor tube 402, except that it includes a plurality of strips 522 having a trapezoidal cross-section. In other words, the edges of the strip 522 that abut against the edges of the other strips 522 are angled, such that the spacing between the strips 522 may be reduced, and the amount of resin 20 required to fill the space is also reduced.

[0124] In FIG. 13, the sail body portion 602 is similar to the sail body portions 402 and 502 shown in FIGS. 11 and 12, except that each strip 622 is wider and includes a plurality of cavities 28. This further improves the efficiency of the material required to form the strip 622 without sacrificing the shear strength of the strip 622. Each strip 622 can be formed to have angled edges, similar to the strip 522 shown in FIG. 12, and can further be formed to have an arcuate cross-section, similar to the strip 122 shown in FIG. 8, whereby the spacing present in the sail body portion 602 is reduced and the amount of resin 20 required is reduced.

[0125] The suction sail may be similar to the rotor sail and the wing sail, except that it preferably further includes means for controlling the flow of the boundary layer of air on the surface of the sail body by generating a significant pressure drop or vacuum on the surface of the sail body (e.g., by suction or aspiration through a fluid-permeable region of the surface). This can produce a high driving force with particularly low energy consumption.

[0126] In an embodiment of the present invention, the cavities present in the sail body as shown in FIGS. 11 to 13 can be used as channels for transporting air from the outside of the sail body to the suction mechanism within the wind power assist propulsion device. This can be achieved by creating one or more openings extending from the surface of the sail body portions 402, 502, 602 to the cavities 28.

[0127] In some embodiments of the invention as described with respect to FIGS. 7 - 13, the strips are laid in a single layer along most or all of the length of the sail body portion. However, in use, there are regions where the bending moment applied to the sail body (and thus the load applied to one or both skins in the axial / longitudinal direction) is higher than in other regions. For example, in a rotor sail 4 (such as that shown in FIG. 1), the region of high load typically includes the skin near the upper bearing 8 (FIG. 1), because the region of the rotor sail 4 above this point functions as a cantilever. In these regions, it is beneficial to reinforce the rotor locally rather than over its entire length.

[0128] Such local reinforcement can be achieved by adding more strips in a second layer. In FIG. 14, the sail body portion 702 is similar to the sail body portion 2 shown in FIG. 7, but includes a plurality of strips 722b contained in a second layer extending along a portion of the length of the sail body portion 702. These are provided in addition to the plurality of strips 722a provided as a first layer along the length of the sail body portion 702.

[0129] To reduce stress concentration in the strips, particularly in the resin between the strips, it is beneficial for one or both ends of the strip to include a taper 724. In other words, the thickness of each strip 722b tapers towards each end of the strip 722b. Even more advantageously, the taper 724 is concave rather than linear, which further reduces stress concentration.

[0130] The ends of the strips 722a of the first layer are not visible, but each end of these strips can also include a taper 724. Similarly, each of the strips shown in FIGS. 7 - 13 may include a taper at one or both ends of the strip.

[0131] During the manufacture of the sail body part including two or more layers of strips such as the sail body part 702, it may be advantageous to place a layer of the intermediate fabric 25 between the layers of the strips 722a, 722b to help the resin penetrate all the gaps between the strips and fill them. Such an intermediate fabric 25 can be a woven fabric, a stitched fabric, or a non-woven fabric (felt / veil).

[0132] Alternatively, the introduction of the resin can be carried out in multiple steps. For example, first, the resin can be introduced into the first fabric and the first strip layer, then the second strip layer and the second fabric can be added, and a further amount of resin can be introduced. However, this requires more time and vacuum consumables.

[0133] Referring now to FIG. 15, a sail body part 802 is shown that can form part of a rotor body according to another embodiment of the second aspect of the present invention. The rotor tube 802 includes a first skin 12 and does not include a second skin.

[0134] In this embodiment of the present invention, the first skin 12 can be fabricated according to the above method of injecting resin only into the first fabric 14. Thereafter, a plurality of strips 822 are added onto the inner surface of the first skin 12. The strips 822 are joined in place by a structural adhesive 821.

[0135] Advantageously, the amount of the axial material can be more easily varied along the length of the sail body (by locally adding more strips) in accordance with the variation of the bending moment, thereby minimizing the total weight and cost of the axial material.

[0136] Also, more expensive carbon fiber strips of practical thickness can be used cost-effectively instead of glass fibers. This is because they can be spread apart rather than being adjacent in continuous layers. In continuous layers, only carbon fibers with a thickness of about 1 - 2 mm are required for a rotor body with a diameter of 5 m, which means that in the aforementioned embodiments of the present invention, there is little benefit from having drawn or drawn-wound strips for separating the first skin and the second skin in order to obtain good bending strength. In this embodiment of the present invention, for example, narrower strips having dimensions of 50 mm in width and 5 mm in thickness and having a gap of 150 mm therebetween can be used. Carbon fibers are advantageous because they are stronger, lighter, and in particular have better fatigue resistance than glass fibers. The strength advantage of carbon fibers is particularly pronounced when drawn because the linearity of the fibers is beneficial. Therefore, using carbon fibers in the axial direction of the sail body according to an embodiment of the present invention may be more cost-effective than using glass fibers, even if the carbon fiber material is more expensive per kg.

[0137] In the sail body 802, each strip 822 is a drawn I-beam-shaped (strip of drawn material) having a considerable depth in a direction perpendicular to the first skin 12. Such strips can be spread apart as shown in FIG. 15 and thus can be used without sacrificing weight (compared to a continuous layer of adjacent drawn objects). The deep drawn object significantly improves the axial bending stiffness and thus provides resistance to shell buckling, especially when supported by circumferential ribs spaced along the length of the sail. Hollow strips as shown in FIGS. 11 - 13 may similarly be beneficial. However, the strips may have a simpler shape as shown in FIGS. 7 and 8.

[0138] Since the strip is not located at the center of the two skins, it may be necessary to compensate for the required thickness of the first skin 12 using more of the first fibers so that sufficient circumferential bending strength can be obtained. In other words, the first fabric 14 must be thicker. Furthermore, a second step of joining the drawn part to the first skin 12 is required, a large amount of adhesive 21 is needed, and the cost and weight increase.

[0139] Also, especially in the case of a rotor sail, there is aerodynamic resistance between the sail body 3 and the tower / stationary cylinder 6 (see FIG. 1), which increases the power consumption of the motor. When using an embodiment of the present invention without a second (inner) skin, this resistance is exacerbated by the non-uniform inner surface of the sail body caused by the strip.

[0140] Referring now to FIGS. 16-18, means are shown for arranging and joining two sail body portions so as to further extend around the sail axis.

[0141] In FIG. 16, the sail body portion 2 (such as that shown in FIG. 2) is joined to the sail body portion 902, which is similar to the sail body portion 2 but includes an extended inner skin 932. To join the two sail body portions 2, 902, they are arranged in contact with each other such that the curved shape of each sail body portion aligns with the curved shape of the other portion. Next, a joining fabric 936 is laid over the exposed edges of the two sail body portions 2, 902. While the two sail body portions 2, 902 are arranged together or after being correctly arranged, resin 920 can be introduced into the joining fabric 936 and any gaps between the two sail body portions 2, 902. Next, the resin 920 is cured, thereby fixing the two sail body portions 2, 902 to each other to form the sail body 903.

[0142] The resin 920 may be the same resin as that used to form the sail body parts 2, 902, or it may be a different resin. For example, the resin 920 may have a higher viscosity than the resin used to form the sail body parts 2, 902, and as a result, it generally retains its shape when introduced into the sail body parts 2, 902, thus making it easier to position the respective parts.

[0143] FIG. 17 shows a sail body 1003 similar to the sail body 903 shown in FIG. 16, except that the joining skin 1038 is used to cover the exposed edges of the two sail body parts 2, 902. The joining skin 1038 is different from the joining fabric 936 shown in FIG. 16 in that the resin has already been introduced into the fabric and cured. Thus, instead of curing the resin in the joining fabric to fix it to the two sail body parts 2, 902, the joining skin 1038 is joined to the two parts using an adhesive resin 1020.

[0144] In FIG. 18, instead of adding an additional joining fabric or skin, both sail body parts include an extended skin. In particular, a sail body 1103 is shown that includes a sail body part 902 (similar to FIGS. 16 and 17) and a sail body part 1102 that includes an extended first skin 1112. Thus, the extended first skin 1112 overlaps the exposed edges of the two sail body parts 902, 1102 in one direction, and the extended second skin 932 overlaps the exposed edges of the two sail body parts 902, 1102 in the opposite direction.

[0145] In other embodiments of the present invention, an extended skin that forms part of one sail body part may be received in a recess of the other sail body part so that the convex surface of the completed sail body is smooth. For example, the extended first skin 1112 may be received in a recess (not shown) of the sail body part 902.

[0146] The three options shown in FIGS. 16 - 18 can also be reversed. For example, the joining fabric 936 can be used to cover the concave surface instead of the convex surface.

[0147] Referring now to FIG. 19, means are shown for joining two sail body portions end to end so as to extend further in the longitudinal direction. This joining means can be applied to any of the sail body portions shown in FIGS. 7-18, and the sail body portion 2 (shown in FIG. 7) is used as an example. The joining parts 1242 are joined to each of the sail body portions 2 to be joined using an adhesive (not shown). Each joining part 1242 includes a vertical surface 1243 adapted to abut against the vertical surface 1243 of the other joining part 1242. The two joining parts 1242 are then bolted together using a bolt assembly 1248.

[0148] In other embodiments of the present invention, each joining part 1242 may be integrally formed with the respective sail body portion 2.

[0149] The advantage of this joining means is that it allows the sail body to be disassembled for transportation and can be adapted to incorporate circumferential ribs such as the circumferential rib 5 shown in FIG. 1.

[0150] Unlike FIG. 7, the ends of the sail body portion 2 are visible in FIG. 19. Thus, it can be seen that the ends of the strip include a taper 24 similar to the taper 724 described with respect to FIG. 14. As previously described, the taper reduces stress concentration in the strip 22.

[0151] Any preference and option regarding a given aspect, feature or parameter of the present invention should be considered to be disclosed in combination with any preference and option regarding all other aspects, features and parameters of the present invention, unless the context indicates otherwise.

Claims

1. A method for manufacturing a sail body for forming part of a wind-assisted propulsion device, comprising: laying a first fabric formed from a first fiber on a mold defining a shape of a part of the sail body; and laying a plurality of strips formed from a second fiber on a surface of the first fabric such that at least a part of the second fiber extends longitudinally along the sail body.

2. The method further comprises: forming the plurality of strips. The method according to claim 1.

3. One or more of the plurality of strips are formed using a drawing or drawing and winding process. The method according to claim 1 or claim 2.

4. One or more of the plurality of strips are formed to at least partially define a cavity within the sail body. The method according to any one of the preceding claims.

5. One or more of the plurality of strips are formed such that at least one end includes a taper. The method according to any one of the preceding claims.

6. Each strip of the plurality of strips includes a pair of profiled edges, and each profiled edge is formed to be nested or engaged with a profiled edge of an adjacent strip. The step of laying the plurality of strips on the surface of the first fabric includes nesting or engaging one or more profiled edges of the plurality of strips with or in relation to a profiled edge of an adjacent strip. The method according to any one of the preceding claims.

7. The step of laying the plurality of strips on the surface of the first fabric includes at least one of: pre-bonding the strips to a backing scrim; holding the plurality of strips against the first fabric using one or more rigid or flexible jigs; and weaving a fiber or a light cloth tape between the strips. The method according to any one of the preceding claims.

8. The step of laying the plurality of strips includes laying the plurality of strips such that an average width of the region of the first fabric not covered by any of the strips is less than 30% of the total width of the first fabric, each width being measured perpendicular to the strip, and the average width being determined by all regions of the first fabric not covered by any of the strips, the method according to any one of the preceding claims.

9. The mold is a female mold, and the plurality of strips are laid on the concave surface of the first fabric, the method according to any one of the preceding claims.

10. introducing resin into the first fabric and optionally into and / or between the plurality of strips; heating the mold to cure the resin, the method according to any one of the preceding claims.

11. The first fabric, the plurality of strips, and the cured resin form a sail body portion for forming the sail body, the method according to claim 10.

12. further comprising laying a second fabric formed from a third fiber on the plurality of strips, the method according to any one of claims 1 to 10.

13. introducing resin into the first fabric and the second fabric and into and / or between the plurality of strips; heating the mold to cure the resin, wherein the first fabric, the plurality of strips, the second fabric, and the cured resin form a sail body portion for forming the sail body, the method according to claim 12.

14. further comprising forming an opening extending from the surface of the sail body portion to the cavity, the method according to claim 11 when dependent on claim 4 or claim 13 when dependent on claim 4.

15. The plurality of strips form a first strip layer, and the method further comprises laying one or more additional pluralities of strips on at least a portion of the first strip layer or on the second fabric to form one or more auxiliary strip layers, the method according to claim 12 or any claim dependent thereon.

16. The method according to claim 15, further comprising the step of laying an intermediate fabric on at least a part of the laid strip layer before laying an additional strip layer on at least a part of the laid strip layer.

17. The method according to any one of the preceding claims, further comprising the step of joining two or more sail body parts to each other to form a sail body.

18. The method according to any one of the preceding claims, further comprising the step of attaching one or more circumferential ribs to the inner surface of one or more sail body parts.

19. The method according to any one of the preceding claims, wherein the wind-assisted propulsion device is one of a rotor sail, a wing sail, and a suction sail.

20. The method according to claim 19, wherein the wind-assisted propulsion device is a rotor sail and the sail body is a rotor sail body.

21. The method according to claim 20, wherein the mold comprises a substantially semi-cylindrical surface.

22. A sail body for forming a part of a wind-assisted propulsion device, the sail body comprising a plurality of sail body parts joined to each other to form the sail body, each sail body part comprising: a first skin formed from a first fiber material formed from a first fiber; a plurality of strips extending longitudinally along the sail body; each strip is formed from a second fiber material formed from a second fiber, and at least a part of the second fiber extends longitudinally along the sail body.

23. The sail body according to claim 22, wherein the second fiber is a glass fiber and / or a carbon fiber.

24. The sail body according to claim 22 or claim 23, wherein one or more of the plurality of strips are strips of drawn or drawn-wound material.

25. The sail body according to any one of claims 22 to 24, wherein one or more of the plurality of strips have a thickness of about 1 mm to about 6 mm.

26. The sail body according to any one of claims 22 to 25, wherein one or more of the plurality of strips have a thickness of at least twice the thickness of the first skin in a direction perpendicular to the first skin.

27. The sail body according to any one of claims 22 to 26, wherein one or more of the plurality of strips at least partially define a cavity within the sail body.

28. The sail body according to claim 27, wherein the sail body includes one or more openings extending from the surface of the sail body portion to the cavity.

29. The sail body according to any one of claims 22 to 28, wherein one or more of the plurality of strips have a substantially rectangular or substantially trapezoidal cross-sectional shape curved so as to substantially follow the shape of the sail body.

30. The sail body according to any one of claims 22 to 29, wherein each strip of the plurality of strips includes a pair of shaped edges, and each shaped edge is shaped to be nested or engaged with the shaped edge of an adjacent strip.

31. The sail body according to any one of claims 22 to 30, wherein one or more of the plurality of strips include at least one end portion including a taper.

32. The sail body according to any one of claims 22 to 31, wherein the average width of the region of the sail body portion without strips in the direction perpendicular to the first skin is less than 30% of the total width of the first skin, each width being measured perpendicular to the strip, and the average width being determined by all regions of the first fabric not covered by any strip.

33. The sail body according to any one of claims 22 to 32, wherein each sail body portion further includes a second skin formed from a third fiber material formed from a third fiber, and the plurality of strips are disposed between the first skin and the second skin.

34. The sail body according to any one of claims 22 to 33, wherein the first skin and / or the second skin has a thickness of about 1 mm to about 4 mm.

35. The sail body according to any one of claims 22 to 34, wherein the sail body has a sail axis penetrating the sail body in the longitudinal direction, and the first fiber and / or the third fiber are oriented at more than 45 degrees, preferably more than 55 degrees, with respect to the sail axis.

36. The sail body according to any one of claims 22 to 35, wherein the first fiber and / or the third fiber are glass fibers.

37. The sail body according to any one of claims 22 to 36, wherein the number of the strips varies along and / or around the sail body.

38. The sail body according to any one of claims 22 to 37, formed using the method according to any one of claims 1 to 21.

39. A ship, comprising a wind-assisted propulsion device attached to a part of the ship, wherein the wind-assisted propulsion device includes a sail body according to any one of claims 22 to 38.

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