Patent Application
20180148141
This invention relates generally to sportsboards, and more particularly to surfboards equipped with a stiffening system having a plurality of fibrous profiles.
Surfboards are recreational sporting goods used for surfing in the ocean. Surfboards are typically used in a stand up position during surfing. Therefore surfboard structures are necessary reinforced to achieve high stiffness and break resistance. In general, surfboard structures can be divided into two main categories according to surfboard structures and production technology: fiberglass surfboards and non-fiberglass surfboards.
A typical type one fiberglass surfboard manufacture utilizes a light density foam blank encased on both the deck surface and bottom surface with a hard coating of fiberglass cloth and resin. This type of surfboard has a hard surface and is usually referred as hard surfboard. Typical foam materials include expanded polystyrene foam (EPS) and polyurethane foam (PU). The foam blank can be incorporated stringer system for controlling flex and reinforcing strength of entire surfboard. Typically a centerline stringer, formed of balsa wood, is sandwiched between two halves of foam blank. Other stiffening materials suitable for stringers may include metal tubes, fiberglass tubes and carbon fiber tubes. In general, the design of reinforcing stringer tubes has a cross-section of round shape or other hollow profile shapes for the purpose of weight reduction.
A cross-sectional view of a typical hard surfboard reinforced by fiberglass layers is illustrated in
Type two non-fiberglass surfboards usually do not utilize any resin impregnated fibers in the layered structure. Typically, this type of surfboard comprises a bottom non-foam plastic plate and a deck foam skin. The surfboards have a soft foam skin on the deck and therefore are usually referred to as soft surfboards. These types of surfboards are usually not reinforced by any hard coating of fiberglass resin on the outer surface. Therefore the strength of this type of surfboard depends very much on the stiffness of stringer system within the foam core. As a result, the stringer of a soft surfboard is usually made into a bow shape to conform to the profile of a surfboard having an upturning front section and an upturning tail section.
Stringer materials for soft surfboards are usually selected from resin laminated bamboo board, plywood board and timber board and these boards are cut to the shape of stringers. Unlike the hard surfboard, wood stringer of soft surfboard cannot extend to the bottom surface or the top surface of the foam core. The top skin and bottom skin are laminated layered structures of flexible foam sheets which are prompted to permanent deformation by collapse of foam cells under prolonged compression force against the hard surface of wood stringer. As a result, wood stringers of soft surfboard are usually encapsulated by the foam core and therefore the height of wood stringers in the vertical direction is limited by the thickness of surfboard foam core. Therefore it is desirable to provide soft surfboards with stringer system of higher flexural strength which is not limited by the thickness of surfboard foam core.
The impact from large waves can cause board breaking problems. Such impacts will trigger the stringer to deform in both the vertical direction and the lateral direction. If the impact forces are strong enough and exceed the breaking strength of the wood stringer either in the vertical direction or the lateral direction, the surfboard fails by fracture and may pose a hazard to the user. The fracture problem is caused by the lower flexural strength of stringers made from plywood board, timber board and resin laminated bamboo board compared to fibrous materials. An optimum stringer system balances strength and weight. The flexural strength of a stringer can be effectively improved to avoid board fracture if, for example, the thickness (horizontal direction) of the stringer is increased. However such a change will considerably increase the weight of stringer and is not favorable for a surfboard application. It is desirable to provide surfboards with improved stiffness and break resistant property to enhance durability of the boards particularly in harsh wave conditions. There is a need for an improved stringer system which greatly increases the stiffness and breaking strength of surfboard while at the same time not significantly increasing the cost or complexity of manufacturing such a surfboard.
High performance surfboards are required to flex a desired amount and quickly return to its original position. Such characteristic is usually referred as flex recovery or memory of surfboard. Conventional hard surfboards generally have a hard shell of fiberglass resin coating as the stiffening structure. The advantage of the hard shell construction is its high stiffness and light weight. However surfboards equipped with hard fiberglass shell may be undesirable in the flex patterns because it has too little flex. In addition, hard surfboard can cause injury to riders and therefore only suitable for experience riders. Therefore it is desirable to develop a high stiffness and light weight surfboard comparable to the conventional hard surfboard. At the same time, the surfboard does not have a hard shell construction like soft surfboard, and thus enhancing safety use for surfboard riders.
It is desirable to provide a soft surfboard having different flexure and stiffness characteristics over selected predetermined regions of the board, which ultimately enhances maneuverability and performance of the board to the rider.
Soft surfboards are originally designed for beginner users. However there are demands for performance soft surfboards designed for more experienced surfers. These performance soft boards demand high stiffness and lighter in weight. Performance soft boards in most cases have a thinner foam core than conventional soft surfboards. It is therefore desirable to provide a soft surfboard with a light weight and high strength stiffening system in a thin foam core.
Wood stringers have an inherent problem of high water absorption, leading to degradation and breakage of the stringers. During surfboard usage, there are opportunities of water invasion from the fin holes seeping into the core of foam blank. The water invasion results in degradation and breakage of the stringers. Therefore, there is a need for a stiffening system for soft surfboard and the materials of such stiffening system is resistant to water absorption.
The invention relates generally to sports board for surfing in ocean such as a surfboard and body board. This present invention seeks to solve the above problems by providing a break resistant composite strengthening system for surfboard. The surfboard stiffening system exhibits higher stiffness and flex recovery and therefore the surfboard is more fracture resistant, greatly enhancing safety for surfboard riders.
The present invention provides a break resistant stiffening system for surfboard comprising: a foam core, a plurality of fibrous profiles evenly distributed on the top surface and/or bottom surface of the foam core, the fibrous profiles are completely or partially embedded inside the foam core wherein the fibrous profiles are bonded with the foam core; an adhesive layer located between the fibrous profiles and the foam core and creating bond between the fibrous profiles and the foam core. The fibrous profiles are substantially aligned along the longitudinal axis of the surfboard and extend substantially the length of the foam core. Reinforced fibrous strips may be applied to increase the bonding area between the fibrous profiles and the foam core so that the fibrous profiles are situated between the fibrous strip and the foam core.
Preferably, the fibrous profiles extend to the two upturning ends of the surfboard foam core and adhere thereon. Preferably, the fibrous profiles are bonded with the foam core via an adhesive layer. Preferably, the fibrous strips are bonded with the foam core via an adhesive layer. Preferably, the fibrous profile has a diameter in the range of 1 mm to 4 mm. Preferably, the adhesive is an epoxy resin.
Compared to conventional soft surfboards, the present invention has the following advantages:
A sports board stiffening system includes a foam core having a foam core top surface and a foam core bottom surface. The foam core receives fibrous profiles as either lower fibrous profiles or upper fibrous profiles. Lower fibrous profiles can be connected to the foam core bottom surface and a bottom laminated foam skin can cover the lower fibrous profiles. The lower fibrous profiles are preferably adhered to the bottom surface of the foam core, so that the lower fibrous profiles are adhesively bonded to the foam core. The fibrous profiles are preferably formed from synthetic fibrous materials, namely monofilament fiberglass.
The fibrous profiles may have a round cross-section. The foam core is encapsulated by a top laminated foam skin at a foam core top surface, and the foam core is encapsulated by an inner bottom foam layer and an outer bottom foam layer on a foam core bottom surface. The fibrous profiles are formed as high stiffness fiberglass profiles and low stiffness fiberglass profiles. The high stiffness fiberglass profiles have a higher stiffness than the low stiffness fiberglass profiles.
Upper fibrous profiles are molded to the foam core top surface. A top laminated foam skin can cover the upper fibrous profiles. The sports board stiffening system also has foam core grooves receiving the fibrous profiles at a surface to the foam core.
The following call out list of elements can be a useful guide in referencing the element numbers of the drawings.
The invention relates in particular to a surfboard equipped with the present stiffening system 10 for preventing board breaking, whereas the surfboard exhibits high stiffness, flex recovery and fracture resistance, and thus enhancing safety for surfboard riders. The surfboard 30 has a surfboard front end 31 and a surfboard rear end 32. In a prior art surfboard, the prior art stringer 54 is a vertically oriented strip that bisects the prior art foam core 51. The prior art upper skin 52 and the prior art lower skin 53 encapsulate the prior art foam core 51. In the present invention, there is no need for a prior art stringer 54, although one could be included for design purposes. Analogously, the present invention can be used for making a body board 33 including a body board nose at the body board front end 34 and a body board tail at the body board rear end 35.
In the preferred first embodiment shown in
In an alternative embodiment, the fibrous profiles may be adhered only on the top surface of the foam core. In another alternative third embodiment, the fibrous profiles may be adhered only on the bottom surface of the foam core. Various modifications can be made without departing from the spirit and scope of the invention. For example, the fibrous profiles may be adhered on any desirable position of the stringer body and additional number of fibrous profiles may be applied to the foam core according to the requirement of mechanical properties. For example, the foam core upper rail surface 28 and the foam core lower rail surface 29 can receive fibrous profiles as well.
The fibrous profile has a cross-section of round shape, rectangle, parallelogram, triangle or any other profile shape, more preferable a round cross-section. As illustrated in
The fibrous profiles and foam core may be bonded by adhesive, screws, rivets, or other mechanical fasteners. Preferred bonding method is using adhesive. The adhesive used for bonding the fibrous profiles should exhibit high bond strength and good toughness to tolerate the flex of stiffening system induced by the high impact force of ocean wave. Good heat resistance is also important in the application of surfboards because they are exposed directly to sunlight.
In the preferred embodiment, an adhesive coating 17 is applied between the fibrous profiles 11 and the foam core 21. Heat resistant adhesives suitable for the present application include epoxy base adhesives, polyester base adhesives, hot melt adhesives and rubber based adhesives. Epoxy base adhesives are more preferable because they have the characteristics of high bond strength, good toughness and heat resistance.
In the preferred embodiment, the fibrous profile has a cross-section of round shape and is made of fiberglass resin at a diameter in the range of 1 mm to 8 mm and more preferable in the range of 1 mm to 4 mm. When the fibrous profile has an elongated shape, the fibrous profile can be in the shape of a rod. The strength of the reinforced surfboard foam core is mainly contributed by the fibrous profiles. The application of fibrous profiles on the top and bottom surfaces of the surfboard foam core increases the flexural strength of the surfboard in both the vertical direction and the transverse direction and therefore significantly increase the breaking strength of the surfboard. The fibrous profiles can be interwoven to provide a net shaped structure from the individual strands of the fibrous profile.
The fibrous profiles applied to surfboard foam core in the present invention have a sectional thickness generally larger than the thickness of the fiberglass resin coating layer of the conventional hard surfboard. Therefore fibrous profiles exhibit higher elasticity in response to bending. When the surfboard foam core is equipped with stiffening system of fibrous profiles substantially along the entire length of foam core, the stiffening system has greatly improved its flex recovery characteristics. As the fibrous profiles are securely bonded to the foam core, the fibrous profiles function like a spring to evenly distribute any impact force from waves. When the surfboard flex under bending force, the deformation has a stretching effect to the fibrous profiles. The fibrous profiles tend to resist the stretching action from the bending force due to its high tensile strength. The result is that the surfboard has less flex and spring back more quickly under impact force. Consequently, the reinforced surfboard is less prone to breaking, enhancing the safety of the surfboard. In addition, surfboard with improved flex recovery is desirable for enhancing maneuverability and performance of the board to the rider.
Fibrous profiles are formed from synthetic fibrous materials, selected from fiberglass, carbon fiber, other synthetic fibrous materials or mixtures thereof. Alternatively, the stiffness of the stiffening system can be adjusted to the predetermined desired flex value by employing fibrous profiles having different strength. For example, a carbon fiber rod has greater stiffening effect to the composite stringer than a fiberglass rod. The flexural strength of the fibrous rod may be further adjusted by altering the mixing ratio of carbon fiber and glass fiber inside the fibrous rod. For example, a fibrous rod with increased volume percentage of carbon fiber filaments than glass fiber filaments will produce a rod with higher flexural strength. Fibrous rods made from strands of monofilament fibers provide the maximum stiffness compared with fibrous rods made from woven fibers.
The fibrous profiles are preferably formed as fibrous rods. The fibrous rods of the present stringer system are preferably made from strands of fiberglass monofilament because fiberglass rods have high stiffness and yet relative low cost. The fibrous rods made of fiberglass can be made of fiberglass strand mat that is rolled up and infused with a matrix such as an epoxy resin. The fibrous rods can also be made by spinning multi-filament fiberglass strands into a woven cord or rope and then setting with an epoxy resin.
For requirement of higher flexural strength of the stiffening system, the fibrous profiles may have a larger cross-sectional area at the same profile shape or the fibrous profiles have a cross-section shape designed to have higher flexural strength in the vertical direction.
A typical body board for surfing in ocean is shown in
In particular the invention provides a variable flexure body board in which one portion of the length of the board, constituting approximately the rear two-thirds of the board, is stiff relative to the nose of the board. The variation in the flexure characteristics of the board is provided by a combination of stiffening fiberglass rods. As shown in
In another second preferred embodiment of the stiffening system shown in
In another third embodiment of the stiffening system as illustrated in
During manufacture of the stiffening system, the fibrous profile 11 is made at a diameter in the range of 1 mm to 8 mm and more preferable in the range of 1 mm to 4 mm. The stringer plate 37 has a thickness in the range of 1 mm to 8 mm and more preferable in the range of 1 mm to 4 mm.
Unlike a wood stringer of a soft surfboard, the fiberglass rods of the present invention do not absorb any water and the strength of stiffening system will not be affected by water invasion. Furthermore, the application of the present fibrous profile stiffening system to a soft surfboard foam core will not form a hard surface layer on the foam core. Consequently, the resulting soft surfboard will be safer to user when the surfboard accidentally hits the rider, in particular for beginner surfers.
As shown in
The bottom laminated foam skin includes a plurality of expanded foam layers. In general, the densities of the expanded foam layers increases from inside layer to outside layer for enhancing strength of the bottom structure of surfboard. The preferred embodiment shown in
In the preferred embodiment, the foam core has a thickness between 13 mm and 150 mm and preferably a thickness between 25 m and 90 mm. The foam core has a density between 15 kg/m3 and 65 kg/m3 and preferably a density between 18 kg/m3 and 40 kg/m3. Suitable materials for use as foam core include expanded polystyrene foam (EPS), expanded polypropylene foam (EPP), expanded polyethylene foam (EPE), expanded polyolefin (EPO) and polyurethane foam (PU)., whereas polystyrene foam is the preferred foam core material in the present embodiment. The top laminated foam skin has a thickness between 1 mm and 6 mm and preferably a thickness between 3 mm and 5 mm. The top laminated foam skin has a density between 45 kg/m3 and 176 kg/m3 and preferably a density between 56 kg/m3 and 128 kg/m3. Suitable materials for use as top laminated foam skin include polyethylene foam sheet (PE), polypropylene foam sheet (PP) and ethylene vinyl acetate copolymer foam sheet (EVA), whereas polyethylene foam sheet (PE) is the preferred top foam skin in the present embodiment. The bottom laminated foam skin has a thickness between 1 mm and 6 mm and preferably a thickness between 2 mm and 4 mm. The bottom laminated foam skin has a density between 27 kg/m3 and 128 kg/m3 and preferably a thickness between 38 kg/m3 and 104 kg/m3. Suitable materials for use as bottom laminated foam skin include polyethylene foam sheet (PE), polypropylene foam sheet (PP) and ethylene vinyl acetate copolymer foam sheet (EVA), whereas Polyethylene foam sheet (PE) is the preferred bottom foam skin in the present embodiment. The plastic plate 23 has a thickness between 0.1 mm and 2 mm and preferably a thickness between 0.35 mm and 1.2 mm. Preferred materials for use as plastic plate 23 include polyethylene and polypropylene.
As shown in
In the preferred embodiment, the foam core has a thickness between 15 mm and 75 mm and preferably a thickness between 25 m and 55 mm. The foam core has a density between 15 kg/m3 and 65 kg/m3 and preferably a density between 18 kg/m3 and 40 kg/m3. Suitable materials for use as foam core include expanded polystyrene foam (EPS), expanded polypropylene foam (EPP), expanded polyethylene foam (EPE), expanded polyolefin (EPO) and polyurethane foam (PU), whereas polystyrene foam is the preferred foam core material in the present embodiment. The top laminated foam skin has a thickness between 2 mm and 8 mm and preferably a thickness between 3 mm and 5 mm. The top laminated foam skin has a density between 45 kg/m3 and 176 kg/m3 and preferably a density between 56 kg/m3 and 128 kg/m3. Suitable materials for use as top laminated foam skin include polyethylene foam sheet (PE), polypropylene foam sheet (PP) and ethylene vinyl acetate copolymer foam sheet (EVA), whereas polyethylene foam sheet (PE) is the preferred top foam skin in the present embodiment. The lower rail foam skin is of the same structure and composition as the top foam skin. The bottom laminated foam skin has a thickness between 1 mm and 6 mm and preferably a thickness between 2 mm and 4 mm. The bottom laminated foam skin has a density between 27 kg/m3 and 128 kg/m3 and preferably a thickness between 38 kg/m3 and 104 kg/m3. Suitable materials for use as bottom laminated foam skin include polyethylene foam sheet (PE), polypropylene foam sheet (PP) and ethylene vinyl acetate copolymer foam sheet (EVA), whereas Polyethylene foam sheet (PE) is the preferred bottom foam skin in the present embodiment. The plastic plate has a thickness between 0.1 mm and 1 mm and preferably a thickness between 0.35 mm and 0.55 mm. Preferred materials for use as plastic plate include polyethylene and polypropylene.
Fibrous profiles are formed from synthetic fibrous materials, selected from fiberglass, carbon fiber, other synthetic fibrous materials or mixtures thereof.
The method of making the first preferred embodiment includes the steps of coating a layer of adhesive material on the fibrous profiles; routing a plurality of groove on the surface of foam core; inserting the adhesive coated fibrous profiles into the grooves. After the adhesive coating has completely cured and hardened, the assembled foam core can be used for normal skin laminating process. The additional binding strip of the second preferred embodiment is bonded to the foam core through the similar steps of coating a layer of adhesive material on the binding strip and routing a groove on the surface of foam core. Alternatively the grooves for receiving the fibrous profiles can also be formed by molding of the foam core.
The method of making the third preferred embodiment as shown in
The fiberglass rods are small and the center of the cross-section of the fiberglass rods are very close to the foam core surface. The foam core surface is supported by the tensile strength and loading of the fibrous profiles which restrict the bending of the surfboard. The foam core is restricted in bending by the tension of the fiberglass rods.
While the particular embodiments of the invention have been illustrated and described above, it will be apparent that various modifications can be made without departing from the spirit and scope of the invention. For example, it would be within the scope of the invention to combine the technical features between the various embodiments. Accordingly, it is not intended that the invention be limited by such variations, modifications and improvements.
