EP0064937B1 - Method and construction of sail boards and surfboards - Google Patents

Abstract

According to this method a cellular core (1) is produced, having dimensions smaller to the prescribed dimensions and such size difference is compensated by applying on said core a fiber tissue (2). The space existing between the core (1) and the hull (3, 4) of the board, thus occupied by the tissue (2), is filled with foam in order to form, in the edge area of the core, a highly pressure resistent foam layer reinforced by the fibers, which perfectly binds the rigid hull (3, 4) of the board to the core.

Description

The invention relates to methods for the production of sailing or surfboards, in which a foam core element is inserted between two shell parts and at least regionally interposed mat between two shell parts and the shell parts are joined together.

Furthermore, the invention relates to a sail or surfboard made of a shell, a foam core element and an intermediate layer provided at least in some areas between the shell and the foam core element.

For the production of light-weight sailing or wave riding boards, the two-shell construction is generally used, in which a core made of expanding polystyrene (EPS core) is inserted between two deep-drawn, cooled shell parts before the shell parts are glued together. For the connection between the EPS core and the shell, a foaming adhesive is applied to the EPS core before it is inserted. This is, for example, a foaming adhesive based on polyurethane or epoxy. It also serves to compensate for tolerances between the core and the shell.

The disadvantage of the known method is that the thickness of the shell parts and the density of the EPS core must be chosen to be relatively high in order to achieve sufficient pressure resistance and rigidity over a long service life. In addition, there is the disadvantage that it is difficult to bond the two shell parts to one another with resistance.

From DE-A-2 928 579 a method of the type mentioned is known, in which a sailing board is assumed which consists of two half-shells made of a plastic material, to which a base layer made of rigid foam is first applied. After gluing these two shells made in this way, the cavity is filled with light foam. In order to be able to form a sailing board of this type even more easily, it is proposed according to DE-A-2 928 579 to insert prefabricated lightweight foam parts into the half-shells and then to glue them together, the lightweight foam parts using a compensating material in the form of an absorbent soaked in adhesive known depot mat can be connected to the outer shell. If these light foam parts are not to fill the entire board interior, but only part of the same, they are arranged exclusively in the front part and in the rear part of the fuselage, while the middle section of the board hull is designed in a known manner, namely with a supporting foam and a filling foam. The depot mat used according to this known method is a mat which consists of a fabric made of glass fiber and a fleece applied thereon, this mat having a total thickness of approximately 1 mm. The mat itself has no compressive strength or rigidity of its own. Only when the adhesive has hardened is the outer shell reinforced and the desired adhesion between the outer shell and the foam core part achieved. When the adhesive has hardened, there is practically a correspondingly thicker outer shell, which is perfectly glued to the foam core. The thicker outer shell practically formed with this results in a relatively high board weight in spite of the light foam used to ensure the necessary compressive strength. It is obvious that the impregnated depot mats used here serve as compensation material between the outer shell and the foam core to compensate for manufacturing inaccuracies of these parts and at the same time enable gluing between the outer shell and the foam core.

CH-PS 597 032 discloses a method for producing a sailing board, in which a mold is first lined with at least one layer of glass fibers and plastic and then a glass fiber mat is inserted into the mold in the area of the greatest extent. On this mat and the part of the first layer not covered by it, a layer of a mixture of glass fibers and plastic, e.g. sprayed onto a polyester resin and hardener. Then foam core elements are introduced into the mold, the top of which is then sprayed with the same mixture of glass fibers and plastic. The protruding edge of the glass fiber mat is then placed on the top of the foam core elements. The mold is then closed and its interior evacuated. This known method also produces a relatively thick skin which surrounds the foam core elements and which entails a high board weight.

In this regard, the so-called single-shell construction is more favorable, in which the EPS core is already inserted between the shell parts, while the shell material is still heated and therefore plastic, so that the deep-drawn shell parts are welded to one another and, if appropriate, also to the core material when they are subsequently joined together . However, this requires a high dimensional accuracy of the EPS core, which, in addition to high manufacturing costs, is contrary to the time shrinkage behavior of the expanding polystyrene. The EPS core must also be handled very carefully before it is inserted between the shell parts, since any damage to the core affects the connection between the core and the shell. In addition, there is the problem of ventilation when assembling the shell parts. Inevitably, a certain amount of air remains trapped, which partially excludes a connection between the core and the shell, especially on the upper side. Due to the heat of the shell parts on the core, the core can finally melt locally, which in turn creates cavities between the core and the shell. For all of these reasons, this method also requires the shell design to be overdimensioned ke and the density of the EPS foam to give the board sufficient strength and durability. This oversizing means a high board weight, which runs counter to the desired lightweight construction.

The invention has for its object to improve a method according to the preamble of claims 1 and 2 so that a light board body with high strength and long life can be produced with it. Furthermore, it is an object of the invention to improve a sailing or surfboard according to the preamble of claim 4 in such a way that it is characterized by low weight, high strength and durability.

To solve this problem, two methods and a sailing or surfboard of the type mentioned are proposed, which according to the invention have the measures mentioned in the characterizing part of claims 1, 2 and 4.

By applying the knitted thread to the foam core element at least in the area of a part of the outer surface thereof, a support layer is created at least in regions between the foam core and the shell, which fixes the foam core element spatially exactly and eliminates tolerance problems of the foam core element due to its own elasticity.

In contrast to the known, according to the invention not only a compensating material in the form of a thin depot mat is used, but a part or the entire outer zone of the foam core is replaced by a mat in the form of a knitted thread. In practice, a three-dimensional support structure is created, the knitted thread being a mat made from a large number of stiff threads which penetrate the mat volume irregularly. The mat therefore forms a fixed volume, which for example can have a thickness of 1.5 cm, although the mat is flexible to the extent that it can be adapted to the curvature of the shell parts, but at the same time has its own considerable pressure stability with an extremely low weight . This pressure stability already exists before the mat is foamed. This fact is based on the use of comparatively stiff threads in the mat, which pass through the mat volume in large numbers and in a tangled position. This special type of mat with its own pressure stability makes it particularly suitable for transferring forces to the foam core which act on the board shell from the outside. A special additional reinforcement and thus an increase in weight of the shell is therefore not necessary. The stiffening effect of the mat is improved, however, by foaming the cavity created by the mat.

Since the cavity in which the thread is located is also foamed, larger manufacturing tolerances in the manufacture of the foam core element and damage to it remain without any influence on the board quality. The qualitative requirements for the foam core element are therefore significantly lower, which also leads to a cost reduction in the production of the same. The thread-reinforced edge foam zone formed by the foaming serves at the same time as a secure binding agent between the shell and the foam core element and gives the core excellent compressive strength, so that it absorbs loads that are transmitted through the shell to the inside. It becomes possible to use extraordinarily light foam (up to 12 gr / Ltr) for the foam core element, without the board's strength being impaired, so that overall a very low board weight results.

Advantageous embodiments of the invention are the subject of the dependent claims.

The invention is explained below with reference to the description of exemplary embodiments with reference to the drawing, which shows a cross section of a sailing or surfboard.

A foam core element 1 is produced in accordance with the shape of the sail or surfboard to be produced. This does not already have the nominal size of the foam core, but it is manufactured with an undersize of, for example, 15 mm. Depending on the requirements placed on the sailboard, the foam core element is manufactured all around with this undersize or only certain outside surface areas are given this undersize. For example, the undersize can be limited to the outer surface area of the foam core element, which corresponds to the upper surface of the sail board or only the footprint of the sail board. Expanding polystyrene or another lightweight packing material is particularly suitable as the material for the foam core element, specifically with a density of 12 to 15 gr / liter.

The undersized surface areas of the foam core element 1 are then covered with a knitted thread 2 so that the resulting composite element receives the target contour of the core. The knitted thread 2 is expediently needled onto the foam core element. It has the shape of a mat with a thickness that corresponds to the undersize, for example 15 mm.

The knitted thread consists of relatively stiff plastic threads which run through the mat area in an irregular course and are welded together at points of mutual contact. For example, it is polypropylene threads. On the one hand, the mat is so flexible that it can be needled onto curved surfaces, while on the other hand it is relatively hard perpendicular to the plane of the mat and can absorb and transmit appropriate loads. Flexibility and hardness naturally depend on the rigidity and number of threads per unit volume. Instead of a knitted fabric made of plastic threads, one made of metal wires, such as aluminum wires, or even a knitted fabric made of for example, coconut fibers are used.

The foam core element 1 provided with the knitted fabric 2 is then inserted between two deep-drawn shell parts 3 and 4 of the sailing board and the shell parts are then joined together against one another via the foam core element. Here, the two-shell construction can be used, in which the two shell parts 3, 4 are glued to one another at their butt joint, or the single-shell construction, in which the foam core element 1 is inserted between the shell parts 3, 4 while the shell parts 3, 4 are still heated and thus plastic, and the shell parts then be welded together when joining. Thermoplastic or thermosetting plastics can be used as the material for the shell parts.

With the joining of the two shell parts 3, 4, the manufacturing process according to a first variant of the method is ended. The knitted thread 2 connects the shell parts 3, 4 to the foam core element 1. If the shell parts are still in a plastic state when they are joined together, welding can occur between the shell parts and the knitted thread, while the knitted thread, on the other hand, penetrates slightly into the foam core element 1 and there is mechanically anchored next to the needling. When using the two-shell design, a similar connection between the shell parts and the knitted fabric 2 can be achieved by previously coating the shell parts with adhesive.

A second variant of the method is to foam the cavity formed by the undersize of the foam core element, in which the knitted yarn 2 is located. This can be done by applying foaming adhesive to the foam core element 1 over the undersize area of the foam core element 1. This foaming adhesive based on polyurethane or epoxy then completely fills the cavity created when the shell parts are joined with foam 5. An advantageous embodiment of the method, however, is to foam the cavity in which the knitted thread is located after the shell parts have been joined by injecting a foaming substance, in particular polyurethane or epoxy foam 5. The foaming substance wets the knitted thread and fills all cavities, in particular also damaged areas of the foam core element 1.

This foaming results in an intermediate layer between the shell and the foam core element in the undersize areas of foam reinforced by the thread knit, which has excellent compressive strength and provides a secure connection between the shell and the foam core element, which is equivalent to gluing.

Claims (12)

1. A method for producing sail- or surfboards, respectively, in which a foam core element is placed between two shell parts with the interposition at least in a partial area of a matting, characterised in that for achieving the nominal contour of the core element prior to the placing the exterior surface of the foam core element is provided with the matting in the form of a threadwork composed of a plurality of stiff threads extending in a random and irregular fashion through the volume of said matting, and in that a foaming agent is injected into the void space present between the shell parts and the foam core element after the joining thereof, in which void space the threadwork in located.

2. A method for producing sail- or surfboards, in which a foam core element is placed between two shell parts with interposition at least in a partial area of a matting, characterised in that for attaining the nominal contour of the core prior to the placing the exterior surface of the foam core element is covered with the matting consisting of a threadwork composed of a plurality of stiff threads extending in a random and irregular fashion through the volume of said matting, and in that the area of the exterior surface of the foam core element covered with the matting prior to the insertion is covered with a foamable adhesive which is foamed after the joining of the shell parts.

3. A method according to claim 1 or 2, characterised in that the threadwork is needled onto the foam core element.

4. A sail- or surfboard, respectively, having a shell, a foam core element and an intermediate layer at least in a partial area between the foam core element and the shell, characterised in that as the intermediate layer a matting in the form of a threadwork (2) is provided consisting of a plurality of stiff threads extending in a random and irregular fashion through the volume of said matting, and in that the space between the shell (3, 4) and the foam core element (1) containing the thread work (2) is foamed with a foamable substance (5).

5. Sail- or surfboard, respectively, according to claim 4, characterised in that the foam core element (1) on its complete upper surface of the sailboard is covered with the foamed threadwork (2).

6. Sail- or surfboard, respectively, according to claim 4, characterised in that the foam core element (1) within the standing area of the sailboard is provided with the foamed threadwork (2).

7. Sail- or surfboard, respectively, according to claim 4, characterised in that the foam core element (1) at all sides is covered with the foamed threadwork (2).

8. Sail- or surfboard, respectively, according to any of the claims 4 to 7, characterised in that for the threadwork (2) threads of thermoplastic plastic material, such as e.g. polypropylen, are provided which are welded together at locations of mutual contact.

9. Sail- or surfboard, respectively, according to any of the claims 4 to 7, characterised in that metal wires such as e.g. aluminium wires are provided for the threadwork (2).

10. Sail- or surfboard, respectively, according to any of the claims 4 to 9, characterised in that the threadwork-matting is 15 mm thick.

11. Sail- or surfboard, respectively, according to any of the claims 4 to 10, characterised in that as a foamable substance there is provided polyurethane foam or epoxy foam.

12. Sail- or surfboard, respectively, according to any of the claims 4 to 10, characterised in that as the foamable substance a foaming adhesive on a polyurethane or epoxy-basis is provided.

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