Field of Invention

The present invention concerns water sports board with a ribbed internal skeleton structure, in particular a water sports board with corrugated ribs, and a method of manufacturing a ribbed water sports board.

Background of the Invention

Water sports boards, for example, surfboards, body boards, paddleboards and windsurfing boards, are required to be sufficiently strong to withstand forces both from the weight of a user and from environmental conditions, for example waves, winds and impacts. The boards must therefore have sufficient compressive strength to resist downward forces from the weight of the user, and sufficient tensile and torsional strength to resist torque or bending forces that may arise from external conditions. It is desirable for boards to be lightweight, for ease of use, and to improve performance. The boards must also be sufficiently water resistant to withstand repeated exposure to water for extended periods of time.

Typical water sports boards comprise lightweight polymer foams such as polyurethane foam. These materials have a low density, and therefore can be used to produce reasonably lightweight solid boards. These boards can be coated or covered to improve their strength and to increase their water resistance, for example, using a fiberglass and epoxy, or polyester resin coat.

Plastic or polymer based boards are becoming increasingly undesirable with consumers, owing to the environmental impact of boards comprising non-recyclable materials and their short useable lifetime.

Wooden boards provide a sustainable, environmentally friendly alternative to plastic or polymer based boards. Wood can provide a high degree of compressive and tensile strength. However, owing to the relatively high density of many woods, solid wooden boards are often too heavy to be used, especially for high performance surfing or watersports activities. Wooden boards often also absorb moisture. Cardboard offers a lightweight alternative to wood, but has low water resistance and tends to lack the strength of wooden materials.

Reinforced hollow structures for boards have been proposed to enable buoyancy to be maintained without sacrificing strength, and some examples are described below.

US2531946A discloses a surfboard with a hull formed of aluminium sheets built about a corrugated skeleton and a corrugated frame.

US2009/0142975 A1 discloses a biodegradable surfboard comprising wood veneers over a wooden framework, thereby creating a hollow wooden body.

WO2018035351 A1 discloses a paper-based watercraft board comprising paper based materials that form a honeycomb structure.

FR2826907 A1 discloses a reinforced structure for sailboards comprising a corrugated surface adjoined to the primary skin of the structure.

US5807512 A discloses a lightweight flotation device structure suitable for surfboards, body boards and sailboards, manufactured from plastic materials with structural cores configured to provide strength and rigidity.

Several other attempts have been made to produce cellular cardboard or wooden water sports boards or surfboards, but none of these have achieved both high performance and commercial viability. There remains a need to develop improved water sports boards that are cost effective and environmentally friendly, whilst being sufficiently strong, water resistant and lightweight.

Summary of Invention

According to the first aspect, the present invention provides a water sports board with an internal ribbed structure provided between a top deck and a bottom surface. The water sports board extends along a longitudinal direction, and the ribbed structure comprises a plurality of ribs extending across the board in a lateral direction connecting the top deck and the bottom surface. Each rib is corrugated, and the flutings of the corrugated rib run in an upward direction between the top deck and bottom surface. The internal rib structure enables a water sports board with a high strength to weight ratio to be produced compared to, for example, foam or expanded plastics water sports boards. The corrugated ribs with flutings that run in an upward direction between the top and bottom decks have a particularly high strength to weight ratio compared to materials commonly used for ribs. Corrugated ribs have anisotropic strength properties, and will have a higher compressive strength in a direction parallel to the fluting direction than perpendicular to the fluting direction. The bottom surface may form part of a base.

The water sports board may further comprise rails that provide a frame around the perimeter of the ribs. The rails may comprise cork. The rails may comprise hollow cork rails, which advantageously are lightweight but have a good resistance to impacts, and are easily repairable. Each of the plurality of ribs may extend in a lateral direction across the board between the rails. Each of the plurality of ribs may extend approximately parallel to the other ribs. Each of the plurality of ribs may extend perpendicular to the longitudinal direction.

In some embodiments, the fluting may comprise a material that exhibits strength anisotropy. The ribs may be constructed from a strength-anisotropic material such that the higher strength direction lies substantially along the fluting direction. In some embodiments, the fluting may comprise an anisotropic material formed from elongate grains. The grain direction may lie substantially along the fluting direction. The material may have a higher strength in a direction parallel to the grain, and thus the compressive strength of the ribs may be further improved if the grain lies substantially along the fluting direction.

In embodiments, each rib comprises a supporting strip, wherein the strip connects peaks, and preferably adjacent peaks, of the fluting. The supporting strip may extend the entire length of the rib, connecting each of the peaks. The supporting strip may be located along a top or a bottom edge of the rib. Providing a supporting strip has been found to increase the flexural strength of the rib, such that the ribs and the water sports board will be more resistant to point loads. This may result in a more robust water sports board with an improved lifespan. A supporting strip may be located along each of the top and bottom edges of the ribs. The supporting strip may comprise a grained wood. The supporting strip may comprise a material with a higher tensile strength than the corrugated fluting. This may further improve the torsional strength properties and point load resistance of the board, without adding significant weight.

A supporting strip may be affixed to a peak of a rib using an adhesive. The supporting strip may be affixed to each of the peaks of a rib using an adhesive. Adhesive may be applied to a peak of the ribs to adhere the strip to the ribs. Adhesive may be applied to each peak of the ribs to adhere the strip to the ribs. Adhesive may be applied along the strip to adhere the strip to the ribs. The adhesive may be a wood glue. The adhesive may be an epoxy resin.

In some embodiments, the supporting strip is located along the bottom edge of the rib and affixed to a peak of the rib using an adhesive. The supporting strip is located along the bottom edge of the rib and affixed to each peak of the rib using an adhesive. This strip may increase the effective contact area when the rib is attached to the bottom surface and/or act as an adhesive to the bottom deck (in an embodiment in which the strip is added after the rib is attached to the bottom surface). Advantageously, the supporting strip may therefore improve the adhesive join between the rib and the bottom surface. The supporting strip may also increase the ribs resistance to bending. The water sports board may further comprise a stringer extending along the board along the longitudinal direction. The plurality of ribs may extend outwardly from the stringer.

The ribs may extend approximately perpendicularly to the stringer. Thus, the ribs may extend perpendicular to the longitudinal direction.

Adjacent ribs may extend either side of the stringer and may be connected together, such that adjacent ribs form a pair of ribs.

In some embodiments, it may be that adjacent ribs extending either side of the stringer are connected together. The adjacent ribs may be a pair of ribs. The pairs of ribs may be a monolithic structure. Each pair of ribs may comprise a central slot that enables the pair of ribs to be slotted on to the stringer. The slot may be positioned approximately half way along the length of each pair of ribs (i.e. at the root of each rib in the pair), and the slot may extend approximately halfway between the top and bottom deck.

In some embodiments, each rib may comprise a contact surface parallel to the top deck for gluing thereon. The contact surface may extend the entire length of the rib. The contact surface may be provided along the top edge of the rib and may be arranged to increase the contact area between the top deck and the rib. This may improve the adhesion between the top deck and the rib. Alternatively, or additionally, a contact surface may be provided along the bottom edge of the rib. In this case, the contact surface may be parallel to the bottom deck and may be arranged to increase the contact area between the bottom deck and the rib. The contact surface may be provided along the opposite long edge to the supporting strip. Adhesive may be applied to the contact surface or surfaces to enable the ribs to be adhered to the top deck and/or the bottom surface. The contact surface may comprise a strip of wood such as plywood.

In order to affix the contact surface to the rib, the contact surface may be inverted such that its underside is exposed. Adhesive may be applied to either the exposed underside of the contact surface, or to an edge of the rib, or both. The top edge of the rib may be applied downwards onto the underside of the contact surface. The adhesive may be allowed to partially cure, and the rib and the contact surface may be inverted such that the contact surface is provided along the top edge of the rib when the rib is in its normal state.

Advantageously, affixing the ribs to the underside of the contact surface using liquid adhesive whilst the contact surface is in its inverted state has been found to be beneficial as the liquid adhesive may pool at the join between the ribs and the contact surface, leading to particularly good adhesion between the ribs and the contact surface.

The liquid adhesive used to affix the supporting strips to the ribs and the contact surfaces to the ribs may be a wood glue or an epoxy resin. Everbuild D4 Wood glue has been found to be particularly advantageous for pooling whilst in the liquid state and setting hard.

The water sports board may comprise a body board, a paddleboard, a windsurfing board or water sports board suitable for supporting a person during a water-based activity. Preferably, the water sports board is a surfboard.

The water sports board may further comprise a water resistant fibreglass coating applied to an exterior surface of the board to protect the top deck, the bottom surface and the internal rib structure. The fibreglass coating may be applied to the exterior surfaces of the board. The water sports board may comprise a waterproof coating. The water sports board may further comprise a decorative coating such as a painted or coloured coating or a varnish.

Each rib may be formed from a sheet of corrugated material. The material may be a lightweight corrugated material with a density of between 50-90 kg/m ³ . The material may have a density of between 60-80 kg/m ³ , preferably about 70 kg m ³ . The corrugated material may have a higher compressive strength in the direction of the corrugated fluting.

The corrugated sheets may have an edge crush test of about 3.5-4.5 kg/mm, preferably about 4 kg/mm. In the context of the present invention, edge crush test refers to the test method used in the field to measure the strength of corrugated material in a direction parallel to the fluting direction.

By forming the ribs from a material that has a high edge crush test value, the compressive strength of the water sports board will be improved.

Each rib may comprise a veneer based composite. Each rib may comprise a material that conforms to the CARB2 exempt certification, and/or the IPPC ISM15 exempt certification, and/or the FSC certification. This enables the skeleton structure to be used in an environmentally friendly water sports board.

The material may have a high water resistance and may have a moisture content of about 7- 9%. By forming the ribs from a material that has a high water resistance, the lifespan of the water sports board will be improved, as the ribs will be less susceptible to absorbance of moisture and water damage.

In some embodiments, the material may be CorrShield 1904 - found to have favourable values of the above-mentioned parameters.

In embodiments, the fluting has a peak to trough height of between 18 and 22 mm, preferably about 19 mm. In embodiments, the fluting has a wavelength of between 40 and 60 mm, or between 45 and 55 mm, preferably about 50 mm.

In some embodiments, the top deck of the water sports board may comprise, and is preferably manufactured from, wood. A wooden top deck enables an environmentally friendly water sports board to be produced, avoiding the need to use plastics and foam based materials. The top deck may comprise paulownia wood or another lightweight wood but proportionally strong wood with similar properties. The top deck may comprise a material with a density of around 260-290 kg/m ³ , preferably about 280 kg/m ³ . The top deck may comprise a material with an elastic modulus of approximately 4.1-4.6 GPa, preferably about 4.4 GPa. The top deck may comprise a material with a modulus of rupture of approximately 35-40 MPa, preferably about 37 MPa. Compared to other woods, paulownia wood will enable a lighter top deck to be produced that will have the strength to withstand the weight of a board user.

According to a second aspect, the invention provides a method of manufacturing a water sports board with an internal ribbed structure. The method comprises providing a bottom surface, a plurality of corrugated ribs, and a top deck. The plurality of ribs are arranged between the bottom surface and the top deck, such that the ribs extend across the bottom surface in a lateral direction thereby forming the internal ribbed structure, and such that the flutings of the corrugated ribs run in an upward direction between the top deck and the bottom surface.

According to a third aspect, the invention provides a method of manufacturing a rib. The rib is for use in a watersports board that may include any of the features set out in the description of the invention above. The rib is a corrugated rib, and further comprises a contact surface for gluing thereon. The contact surface is provided along the top edge of the rib. The method of manufacturing the rib comprises affixing an edge of the rib to an underside of the contact surface using an adhesive. The method comprises allowing the adhesive to partially cure, and inverting the contact surface and rib, such that the contact surface is affixed to the top edge of the rib. The method may further comprise applying adhesive to either the underside of the contact surface, or to the edge of the rib, or both.

The method may comprise affixing an upper surface of the contact surface to a top deck. The method may comprise applying adhesive to an upper surface of the contact surface, and affixing the upper surface of the contact surface to a top deck using adhesive.

The method may be used to manufacture a water sports board comprising a plurality of ribs wherein the ribs and the board have any of the features set out above.

According to another aspect of the invention, there is provided a surfboard with an internal ribbed structure provided between a wooden top and bottom surface. The ribbed structure comprises a stringer extending centrally along the board in a longitudinal direction and a plurality of ribs extending outwardly from the stringer. The ribs extend across the width of the board, lying approximately perpendicular to the stringer and parallel to each other, and the ribs connect the top deck and the bottom surface, thereby reinforcing the internal structure of the board. The ribs are formed from sheets corrugated anisotropic material (for example CorrShield 1904). The ribs are arranged such that the fluting direction runs upwardly between the top deck and the bottom surface. Each rib is reinforced by at least one supporting strip affixed to an edge of each rib, and each rib further comprises a contact surface to facilitate gluing of the rib to the top deck.

It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of the invention may incorporate any of the features described with reference to the apparatus of the invention and vice versa.

Description of the Drawings

Embodiments of the present invention will now be described by way of example only, with reference to the accompanying schematic drawings, of which:

Figure 1 shows an exploded view of a surfboard with an internal ribbed structure according to an embodiment of the invention;

Figure 2 shows a connected pair of corrugated ribs for use in the water sports board of Figure i ;

Figures 3a and 3b show a connected pair of corrugated ribs comprising supporting strips and a contact surface, for use in a water sports board according to a second embodiment of the invention;

Figure 4 shows method of manufacturing a water sports board according to an embodiment of the invention;

Figure 5 shows method of manufacturing a water sports board according to an embodiment of the invention; and

Figure 6 shows a pair of corrugated ribs comprising a supporting frame, for use in a water sports board according to another embodiment of the invention;

Detailed Description

According to an example embodiment of the invention (Figure 1), there is provided a surfboard 1 with an internal ribbed structure 3 provided between a top deck 5 and a bottom surface 7. The top deck 5 and bottom surface 7 (i.e. the base 7) provide substantially planar surfaces, and the top deck 3 provides an upper surface on which a user may stand when the board 1 is in use. The top deck comprises paulownia wood, which is advantageous as it is particularly light and strong. The surfboard also comprises a set of cork rails (not shown), which provide a frame around the perimeter of the ribs and the stringer. The surfboard is coated with fibreglass (not shown) to improve water resistance and durability of the board. The ribbed structure comprises a stringer 9 extending along the board in a longitudinal direction. The stringer 9 forms the spine of the skeleton structure, extending centrally along the entire length of the board. A multiplicity of ribs 13, extend outwardly from the stringer 9, spanning the width of the board, in a direction substantially perpendicular to the length of the stringer 9. The ribs 13 run approximately parallel to one another, and the ribs 13 connect the top deck 5 and the bottom surface 7, thereby reinforcing the hollow cavity between the top deck 5 and the bottom surface 7. The skeleton structure 3 gives the surfboard an improved strength to weight ratio compared to more traditional hollow frames.

Each rib 13 is corrugated, and is manufactured from sheets of CorrShield 1904, which has been found to show high compressive strength, torsional strength and water resistance, whilst being lightweight and made of natural materials. The flutings of the corrugated rib run in an upward direction between the top deck 5 and the bottom surface 7. The corrugated ribs 13 have a higher compressive strength in a direction parallel to the fluting direction, and the arrangement of ribs shown in Figure 1 therefore ensures a relatively high compressive strength of the surfboard, particularly in a direction parallel to the fluting direction.

CorrShield 1904 is an anisotropic grained material, with a grain length running parallel to the direction of the flutings, and a higher compressive strength in the grain direction than perpendicular to the grain.

The surfboard 1 is manufactured from responsibly sourced materials, including paulownia wood and CorrShield 1904. The materials exhibit good water resistance and good strength to weight properties particularly exhibiting good compressive strength in a direction parallel to the flutings of the ribs.

A connected pair of corrugated ribs 14, 15 for use in an embodiment of the invention are shown in Figure 2 to which reference is now made. The ribs 14, 15 are a made from a single piece of material (i.e. form a monolithic structure 17). The pair of ribs 14, 15 comprises a central slot 19 that enables the pair 14, 15 of ribs to be located onto a stringer. The slot 19 is positioned halfway along the length of each pair of ribs 14, 15, to enable the ribs 14, 15 to slotted onto a centrally positioned stringer. The slot 19 extends approximately halfway between the top deck and the bottom surface, i.e. approximately halfway along the height of the rib. The ribs 14, 15 comprise fluting that has a peak to trough height / of 19 mm and the fluting has a wavelength / of 50mm. The arrangement in Figures 1 and 2 has been found to be especially beneficial in providing a strong but lightweight surfboard design.

A connected pair of ribs 114, 115, in a second embodiment of the invention is shown in Figures 3a and 3b. The ribs are for arranging along a central stringer in the same manner as the first embodiment. Corresponding features are provided with the same reference numerals as Figures 1 and 2 but incremented by 100 Each rib 114, 115 comprises supporting strips 121, 122 and a contact surface 123. The supporting strips 121, 122 are affixed to the bottom edges of the ribs 114, 115 connecting the peaks, and thereby increasing the torsional strength of the ribs 114, 115 by restricting the ribs from twisting or deforming under point loads. The supporting strips 121, 122 may increase the resistance of the ribs 114, 115 to bending. The width of the supporting strips 121, 122 are narrow compared to the width of the ribs 114, 1 15 and the supporting strips 121, 122 therefore improve the torsional strength of the ribs 114,

115 without adding significant weight.

The supporting strips 121, 122 are affixed to the bottom edges of the ribs using an adhesive (not shown). The adhesive may be applied to the junctions 125 between the strip and the peaks of the rib 114, 115. During assembly of a water sports board, a plurality of ribs may be affixed to a bottom surface. Pooling of the adhesive at the junctions 125 between the strip and the peaks of the ribs 114, 115 advantageously increases the effective contact area for when the ribs 114, 115 are attached to the bottom surface, and may provide additional adhesive for affixing the ribs 114, 115 to the bottom surface thereby improving adhesion, and improving the strength of the join between the ribs 114, 115 and the bottom surface.

The pair of ribs 114, 115 shown in Figure 3a also comprises a contact surface 123 provided along the top edge of the pair of ribs 114, 115 (i.e. on the opposite edge to the supporting strips, 121, 122. The contact surface 123 increases the contact area between a top deck and the pair of ribs 114, 115, and provides a gluing surface. Adhesive is applied to the contact surface 123 to enable each pair of ribs 114, 115 to be adhered to a top deck. The increased contact area improves the adhesion between a top deck and each pair of ribs 114, 115.

According to a further embodiment of the invention (Figure 4), there is also provided a method 201 of manufacturing a water sports board comprising an internal ribbed structure. The method 201 comprises steps of providing a top deck, a plurality of ribs and a bottom surface 203. The method 201 comprises arranging the plurality of ribs between the bottom surface and the top deck, such that the ribs extend across the bottom surface in a lateral direction, thereby forming the internal ribbed structure, and such that the flutings of the corrugated ribs run in an upward direction between the top deck and the bottom surface 205.

According to a further embodiment of the invention (Figure 5), there is also provided a method of manufacturing a rib 301. The rib is a rib for use in a watersports board that may include any of the features set out in the description above. The rib is a corrugated rib, and further comprises a contact surface for gluing thereon. The method of manufacturing the rib 301 comprises affixing an edge of the rib to an underside of the contact surface using an adhesive 305. The adhesive is allowed to at least partially cure 307. The contact surface and rib are inverted such that the contact surface is affixed to the top edge of the rib 309. The method may further comprise applying adhesive to either the underside of the contact surface, or to the edge of the rib or both 311. The method may comprise affixing an upper surface of the contact surface to a top deck 312.

A further alternative embodiment of the invention, shown in Figure 6. This arrangement is similar to the second embodiment shown in Figures 3a and 3b except that the supporting frame 339 comprises a supporting strip 341 affixed to the top edges of the ribs 314, 315 and a further supporting strip 343 affixed to the bottom edges of the ribs 314, 315. The frame 339 is formed from a single piece.

Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described.

In other embodiments of the invention (not shown) the ribs may not extend substantially perpendicular to the longitudinal direction across the board, but may instead be offset at an angle (for example to form a herringbone layout).

In other embodiments of the invention (not shown), each rib may comprise contact surface provided along both its top long edge and its bottom long edge.

In other embodiments, the water sports board comprises a body board, a paddleboard, a stand-up paddleboard, a kite-surfing board or a windsurfing board.

In another embodiment, the board may not necessarily comprise a stringer and may instead just have a plurality of ribs extending in a lateral direction. Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.