EP1475303A2 - Surfboard and method for its production - Google Patents

Abstract

The sub-assembly comprises a hollow inner shell (7) made from resin-impregnated fibres with optional reinforcement or support, covered with a layer (8) of a high-density foam which can be reinforced locally by a plastic or cardboard honeycomb structure. The shell has a wall thickness of 0.1 - 2 mm; the foam has a density of 50 - 70 kg/cu m and is 3 - 20mm thick.

Description

The invention relates to a sub-assembly designed to make a gliding float on water. including a surf float.

It also relates to a method of manufacturing such a subassembly and a float made from the subset in question.

Traditionally, a surf float is made from a foam bar, especially polyurethane foam, which is formed in a mold. The foam bread is machined by planing and sanding on a small thickness to locally customize its then it is coated with a fiberglass shell impregnated with resin which forms an external reinforcement shell and gives the float its final shape. A decoration and a frosting give the float its final appearance.

In some cases, the foam bread is cut longitudinally into two parts which are then glued against a wooden slat which strengthens its structure and imposes a predetermined longitudinal camber.

The disadvantage of such a construction technique is the weight of the float in the end. In Indeed, the foam is relatively dense, typically its density is 50kg / m3. And it is not possible a priori to decrease the density of the foam without harming the mechanical characteristics of the float.

According to another construction technique from windsurfing, we start with a loaf relatively low density foam that is machined to shape it. We covers this bread with a fiberglass skin impregnated with resin. We report around this sub-assembly a higher density foam shell. Then we apply tablecloths resin impregnated glass fibers to form the outer shell.

Such a construction method allows a weight gain of about 20% or more while keeping good rigidity under the feet. However, its implementation is relatively complex. In addition, the central foam bar is generally made of polystyrene foam. This material has the defect of taking water. It happens that during its existence the float is hit against a reef or rock. If the outer shell is damaged, there is a risk to have water infiltration, water weighing down the float and being particularly difficult to clear out.

Finally, it is known to make hollow floats with sandwich skins. Or else produces two half-shells which are then assembled together, or else the whole in a closed mold with an internal bladder which is inflated to push and apply the sandwich skins against the walls of the mold.

This manufacturing technique allows for light boards. However, it it is not possible to customize the shape of the float. In this case the shape of the shell external depends exclusively on the shape of the mold.

An object of the invention is to propose an improved sub-assembly, which makes it possible to carry out lighter surf floats while maintaining a customizable shape, or more bulky for an equal weight.

This object is achieved by a structural sub-assembly which according to the invention comprises a hollow inner shell, which is covered with a foam envelope suitable for machining.

The float is characterized by the fact that it comprises the previously defined assembly covered with at least one layer of fibers impregnated with resin.

The invention will be better understood by referring to the description below and to annexed drawings attached to it.

Figure 1 is a top view of a surf float.

Figure 2 is a side view of the float of Figure 1.

FIG. 3 is a cross-sectional view of a float produced in accordance with the prior art.

Figure 4 shows, in cross section, the structural sub-assembly according to a first embodiment of the invention.

Figure 5 is a longitudinal sectional view of the float made from the sub-assembly in Figure 4.

Figure 6 shows the same float in cross section.

Figure 7, 8 and 9 are cross-sectional views illustrating three variant layouts of the invention.

Figures 10 to 13 illustrate in cross section a fourth variant of embodiment of the invention in which the structural sub-assembly is produced in the form of two half-shells.

Referring to Figures 1 and 2, in known manner, a surf float is presented like an elongated board with a central part 2, a tapered front spatula and slightly raised 3, and a rear heel 4 slightly raised and with a reduced width.

Traditionally, as shown in Figure 3, the float is made from a foam bar 5, typically polyurethane foam with a density of 50 kg / m3, which is covered with a sheet 6 of resin-coated fibers. Usually the foam bread is made in mold, and it is available in different length, width, volume and variable camber. Once chosen by the manufacturer, the foam bread is put to the final shape desired by local planing on a small thickness, and only then, it receives its external coating. This coating increases the characteristics mechanical foam, and also protect the foam bread.

Figures 4 and 5 show, respectively in cross section and in section longitudinal, a structural subset of the float according to the invention, that is to say the subset which is located under the outer lining of the final float.

According to this first embodiment of the invention, the sub-assembly is formed by an internal shell 7 which is coated with a foam envelope 8.

The inner shell is hollow. It is a structural element for example made in fiberglass, carbon or other synthetic material impregnated with resin, resin polyester, epoxy or other.

For example, the internal shell is made with a thickness of between 0.15 and 0.2 millimeters, or between 0.10 and 0.25 millimeters, or even more depending on the intended use for the float and the type of resin used. In some cases and depending on the material used, the thickness can reach 1 to 2 millimeters.

The internal shell can be produced using different techniques. For example she is formed around a central core made of polystyrene beads bonded with vinyl glue which is then dissolved in hot water. Other types of dissolvable chucks can be used or even an inflatable bladder.

According to another production technique, the shell is produced in several parts assembled together. For example, the shell can be made from two half-shells (or half-shells) which fit into each other. Both parties are assembled by gluing or any other appropriate means. Other possibilities still exist.

The shell 7 can also be constructed of materials other than fibers impregnated with resin, for example a thermoplastic, charged thermoplastic of fibers, of fibers projected with a polyester matrix, of stamped metal or any other material with high elastic modulus.

The shell is coated with an envelope 8. The envelope is made of foam, but different types of foams can be used. We can for example use a PVC foam relatively dense, with a density of 50 to 70 kg / m3. You can also choose to use less dense foams, for example polyurethane foams of around 50 kg / m3. We can also use polystyrene foam (extruded or expanded) from 30 to 50 kg / m3 or polyamide imide foams or any other waterproof foam.

The thickness of the envelope is determined to allow subsequent machining of this sub-assembly on this small thickness while ultimately having a resistant sub-assembly and lightweight. For example, the thickness is between 3 and 15 millimeters or even 20 millimeters. Optionally, a greater thickness can be provided along the lateral edges and front / rear of the subassembly, and lower on the top and bottom. We can also provide different thicknesses on the top and bottom, on the front and rear.

To make the foam envelope, glue sheets of foam that we curves to the shape of the shell by applying pressure, for example vacuum, leaving the inside of the shell at atmospheric pressure so as not to distort this shell. A variant consists in placing the shell in the center of a mold in which the foam is injected, or else pour or spray this foam on the shell and leave it expand in the open air. The polymerization of the foam ensures its surface cohesion with the shell. A primer can be applied to the shell surface to improve the performance.

The sub-assembly thus produced has the advantage of being light and resistant. Indeed, as the inner shell 7 is hollow, a significant weight saving is obtained by compared to a traditional mousse bread.

It is more resistant than a traditional foam bread given its structure, with the inner shell and the relatively dense foam shell. The two elements intervene in a complementary way, the shell by its own resistance and by the effect of closed shell, and the foam by its own resistance and the stress spreading effect that it produces on the surface of the shell and the role of nucleus in the final sandwich after contribution of the last surface layer.

In addition, thanks to the weight gain previously mentioned, one can choose a foam stronger and denser than traditional foam while retaining weight significantly lower than that of a traditional float.

In addition, thanks to the low thickness of foam used and the support of the shell, can locally strengthen the surface underfoot by adding a nest structure bee (plastic, cardboard, aluminum ...) when the foam is produced.

We could also use other filling materials, such as wood, or globally any material with a density less than 1.

The sub-assembly can be machined in the same way as a traditional foam bar, according to the wishes of the manufacturer, provided that the machining thickness remains less than the thickness of the foam.

As with traditional breads, the invention provides for making several models of structural sub-assemblies with length, width, volume and camber variable. However, we can use the same shell model for several models of board, and play on the shape and thickness of the foam envelope to get the shapes desired endings.

Finally, once shaped, the structural sub-assembly with its layer of foam machined 8 'is intended to be covered with a sheet 9 of glass fibers or other coated with resin, and to receive finishing operations in the same way as for a float traditional. This is shown in Figure 6.

During use, since the inner shell is hollow, a user will have less problem in evacuating the water which will have seeped if necessary following a shock thanks in particular to the incorporation of a drain screw. On this subject, we can plan to inside the shell a swollen bladder that reduces water penetration inside the shell. This bladder can even be inflated with a gas lighter than air, for example helium, to further lighten the structure.

Figure 7 relates to an alternative embodiment of the invention. According to this variant, the internal shell 10 is reinforced by a central partition 11. Such a partition is commonly used especially for long floats, to give them a determined camber and better longitudinal rigidity.

In the present case, the central partition 11 is for example made of foam or wood. She spans the length of the shell. The shell 10 is formed around this partition. Optionally, the partition is bordered by two layers 13 and 14 of fibers impregnated with resin, which are continuously connected with the shell wall.

As in the previous case, the shell 10 is coated with a foam envelope 12.

Figure 8 relates to another variant, where the upper wall of the shell 15 is supported by a foam plate 16 previously curved.

To make the sub-assembly, for example, the plate 16 is shaped by thermoforming or any other suitable technique.

The lower wall of the shell is first produced, on which it is placed the plate 16 in place.

Then, the shaping of the shell is finished by covering the plate 16 with the sheet of fiber impregnated with resin, then the foam envelope 17 is formed.

This plate 16 improves the resistance to penetration of the upper part of the sub-assembly, ie under the feet of the surfer.

According to the variant illustrated in Figure 9, the plate 18 is in two parts 18a, 18b which is join at the level of a central partition 19 of the same nature as the partition 11. As in the previous case, the shell 20 is closed above the plate 18 and the envelope 21 is formed around the shell 20.

FIGS. 10 to 13 illustrate yet another alternative embodiment of the invention in which the structural sub-assembly is produced from two half-shells assemblies. The sub-assembly can thus be formed by an upper half-shell 22, which will form the bridge of the final float, and of a lower half-shell 24 which will form the hull. Each half-shell is formed of a foam plate 26, 28 which is first thermoformed in a mold and then covered, on an internal face 30, 32, with at least one layer of fabric impregnated with resin. Advantageously, the laminating operation of the internal face 30, 32 half-shells 22, 24 will be produced under vacuum while the foam plate previously thermoformed 26, 28 is still in the thermoforming mold, so that the layer of resin-coated fabric hardens on the thermoformed sheet while it is still pressed against the mold. The shape of the front half-shell is thus best guaranteed assembly.

When the two half-shells 22, 24 are assembled to one another, for example by bonding, one obtains directly on the one hand the rigid internal shell 7, which is formed by the layers of resin-coated fabrics arranged on the internal faces of the half-shells, and on the other hand the outer foam envelope suitable for being machined 8. The foams used are for example sheets of extruded polystyrene foam with a density of the order of 30 to 50 kg / m3.

For the implementation of this variant, it may be advantageous to provide that one of the half-shells, for example the lower half-shell 24, is also laminated on its face 34 before the assembly of the two half-shells. The half-shell thus laminated on its two faces 32, 34 is then particularly rigid during assembly with the other half-shell, which allows to better control the precision of the assembly, and therefore the precision of the shape of the subset. Of course, the foam envelope covering the shell is not then more suitable for being machined over its entire surface. One of the faces is already laminate at the time of assembly, the geometry of this face can no longer be profoundly changed. However, we have noticed that, to modify significantly the final behavior of the gliding float, it is often enough to modify the geometry of the side edges of the float (usually called the float rails). This geometry can be modified even if one of the external faces of the float (for example the lower face) is already stratified.

In the example illustrated in FIGS. 10 to 13, it can be seen that the two half-shells are not symmetrical. Indeed, it can be seen that the lower half-shell 24 does not have no side edges. When shaped, the plate is bent in the direction longitudinal (which is therefore not visible in the drawings) to follow the camber curve longitudinal (sometimes called "rocker" or "scoop" curve). She could also be curved in the transverse direction, for example to form a V-shaped or double hull concave, but in the example illustrated the lower half-shell has no curvature cross. In this case, since the deformation of the foam plate with respect to in its initial plane state is relatively weak, the shaping of the plate can be done without thermoforming, simply by pressing the plate against the mold by vacuum when of stratification. After the resin has hardened, the stiffness of the resin-coated fabric is sufficient to maintain the plate in the desired shape of the half-shell.

On the contrary, the upper half-shell 22 is thermoformed so as to be curved longitudinally, but also transversely to form curved side edges 36 down. According to the invention the internal faces (that is to say the lower face 30 of the half-shell upper 22 and upper face 32 of lower half-shell 24) are laminated with one or more layers of fiber fabrics impregnated with thermosetting resin. As can be seen in FIG. 10, the lower face 34 of the lower half-shell 24 is also laminated, before the assembly of the two half-shells.

As can be seen in Figure 11, the assembly of the two half-shells is obtained by sticking the lower edge of the side edges 36 of the upper half-shell 22 against the face upper 32 of the lower half-shell 24. The adhesive will be chosen so as not to be too difficult to machine, i.e. so as not to create a hard spot in the foam constituting the lateral edge of the sub-assembly.

With this construction, we see in Figure 12 (which illustrates in more detail the side edge of the sub-assembly just after assembly) that most of the edge height lateral 38 of the structural assembly is formed by the lateral edges 36 of the half-shell upper whose outer face 40 is made of foam. The lower part of these edges lateral is constituted by the lateral edge of the lower half-shell which has a thickness of foam 28 framed (top and bottom) by two thicknesses of impregnated fabrics of resin 32, 34. As the thicknesses of fabrics 32, 34 are very small, they do not form obstacle to shaping by machining the side edges. So, in Figure 13, we can see that the geometry of the lateral edge 38 of the structural sub-assembly has been modified over the entire the height of the lateral edge 38, for example by planing and sanding.

However, as a variant (not shown), it will be possible to ensure that the part peripheral of the upper face 32 of the lower half-shell 24 is devoid of lamination so that the side edges 36 of the upper half-shell 22 are resting against the foam 28, this in order to ensure better continuity of the material forming the side edge 38 which then only consists of foam.

The stratification of the external surface, in this case the lower surface 34 of the lower half-shell, can be total (as illustrated). It can also concern only one part of the surface, for example the central part to preserve perfect machinability of the side edge 38.

With this construction, the precise assembly of the two half-shells is facilitated by the high rigidity of the lower half-shell, and the sub-assembly remains suitable for being machined on its entire upper face and on its lateral edges, which leaves a large capacity for customization of the sub-assembly. Once customized, the structural subset is covered with an outer layer of fibers impregnated with resin. Depending on the case, we can choose to also cover the already laminated external surface 34 of the sub-assembly with this outer layer, to increase the rigidity and solidity of the float, or on the contrary choose to do not cover this already laminated surface 34, this in order to limit the weight of the float.

Of course, in the case where one wishes to privilege the possibility of personalizing the hull of the float, one could foresee that the half-shell laminated on its two faces is the upper half-shell, the lower half-shell then being laminated only on its face upper 32. In both cases, the sub-assembly thus produced is a sub-assembly which, sense of the invention, comprises a hollow and rigid internal shell, and an envelope of foam capable of being machined which completely covers this internal shell. optionally part of this envelope (whose geometry we do not wish to modify, for example the upper face of the upper half-shell or the lower face of the lower half-shell), can be covered with a rigid outer layer.

As in the case of the embodiments of FIGS. 7 and 9, it will be possible to advantageously plan to provide the subset of Figures 10 to 13 with a partition longitudinal center vertically connecting the two half-shells.

Naturally, the present description is given for information only, and one could adopt other implementations thereof without departing from the scope of this invention. For example, we could double the internal shell and therefore stack alternately comprising layers of fibers and layers of foam for the sub-assembly. We could also have several longitudinal, transverse or other partitions appropriate directions, these partitions forming connections between the deck and the hull of the float. Optionally, these partitions may create a partitioning of the internal shell by several watertight compartments.

In addition, the invention could be applied to the construction of floats other than surf floats, for example for windsurfing floats, floats intended for swimming in the waves and overall, any nautical practice in which the float works mainly in the planar mode.

Claims (10)

Method for manufacturing a float for gliding on water, characterized in that it comprises the steps consisting in: forming an upper half-shell (22) by thermoforming a foam plate (26), which is covered, on its lower face (30), with an internal layer of fibers impregnated with resin; forming a lower half-shell (24) comprising a layer of foam covered on its upper face (32) with an internal layer of fibers impregnated with resin; assembling the two half-shells so that the said internal layers of fibers impregnated with resin form a hollow shell covered with a foam envelope. Method according to claim 1, characterized in that , in the step of forming the upper half-shell (22), the foam plate is first thermoformed and then covered, on a lower face (30), with minus a layer of fiber impregnated with resin. Method according to one of claims 1 or 2, characterized in that it comprises the additional step consisting of laminating at least part of the external surface of one of the half-hulls (22, 24) before the assembly of the two half-shells. Method according to one of claims 1 to 3, characterized in that the foam layer of at least one of the half-shells (22, 24) consists of extruded polystyrene. Method according to any one of the preceding claims, characterized in that the upper half-shell (22) is thermoformed to form lateral edges (36) curved downwards, and in that the lower half-shell (24) does not has no side edges. Method according to any one of the preceding claims, characterized in that it comprises a step consisting in providing at least one foam partition vertically connecting the two half-shells. Method according to any one of the preceding claims, characterized in that it comprises the additional step of covering the assembled half-shells with an external layer of fibers impregnated with thermosetting resin. Water float, characterized in that it comprises an upper half-shell (22) incorporating a plate of thermoformed extruded polystyrene covered, on its lower face (30), with an internal layer of fibers impregnated with resin , a lower half-shell (24) incorporating a layer of foam covered on its upper face with an internal layer of fibers impregnated with resin, an external layer of fibers impregnated with resin, and at least one foam partition vertically connecting the two half-shells. Water float according to claim 8, characterized in that the foam layer of the lower half-shell consists of extruded polystyrene. Water float according to one of Claims 8 or 9, characterized in that it comprises several longitudinal, transverse or other directions partitions.

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