EP0195453B1 - Wishbone for a sail board - Google Patents

Abstract

Boom of the wishbone-type for sailing boards, where the spars (4,6) at least have a core (12) made from a rigid foam, which has essentially plane surfaces on the inside and outside of the spars, which extend across a significant section of the length of the core. On the plane surfaces there are arranged synthetic-resin-strengthened UD-slivers (22), which extend in the longitudinal direction of the spars across the length thereof, and there is provided an outer layer (24) from a synthetic-resin-strengthened fibre fabric or braiding with slivers intersecting at an angle of between 30 DEG and 60 DEG to the longitudinal extension of the spars. The UD-slivers (22) are preferably arranged between the inner and the outer fabric layer (20,24) in the form of previously cured CFK-UD-strips.

Description

The invention relates to a boom for sailing boards according to the preamble of claim 1.

It is known that the profile of the sail of a sail board depends crucially on the rigidity of the boom. Even small changes in the length of the boom under the load from the sail and the holding force lead to considerable changes in the sail profile and thus to a deterioration in the propulsion achievable with the sail.

The development of booms has therefore become more and more rigid booms in recent years. On the other hand, booms are required to be as light as possible.

In order to achieve high rigidity with low weight, highly rigid booms are made from high-strength aluminum tubes. The fork legs bent from the tubes are each connected to the boom end pieces via plug connections.

The achievable stiffness when using high-strength aluminum tubes are limits to the mate _"rial and in weight.

In a boom of the generic type (DE-U-82 00 406) one or more braided, knitted or woven tubes made of synthetic resin-bonded carbon fibers, aramid or glass fibers are provided on tubes preformed according to the radius of the spars of the boom. Only a very low degree of rigidity can be achieved with fork trees designed in this way.

Composite masts are also known (DE-A-2061921), in which an outer jacket made of a synthetic resin-bonded fiber fabric is formed on an inner mast made of a foam. The outer jacket is cured to achieve a prestress with radial compression of the inner mast. It is also known to provide reinforcing elements made of carbon fibers, glass wool or the like, which can be bound with synthetic resin, extending between the inner mast made of foam and the outer jacket and extending over the entire height of the mast.

The invention has for its object to improve a boom for sailing boards according to the preamble of claim 1 so that greater rigidity can be achieved with the same or less weight.

This object is achieved according to the invention based on a boom according to the preamble of claim 1 by the features highlighted in the characterizing part.

Appropriate configurations are the subject of the dependent claims.

Fork trees according to the invention are not only characterized by a higher rigidity than was previously achievable. Weights for the boom can also be achieved, which are one third less than the weights of the best booms currently known. Stiffness numbers, defined as the test load divided by mass x shortening, can be achieved that are almost twice as large as for these.

• Fig. 1 zeigt in Draufsicht einen Gabelbaum.
• Fig. 2 zeigt einen Schnitt längs der Linie 11-11 in Fig. 1. durch einen Gabelholm.
• Fig. 3 zeigt in vergrößertem Maßstab in Draufsicht die Ausbildung des Gabelbaums im Bereich des vorderen Gabelbaumendstückes, teilweise horizontal geschnitten.
• Fig. 4 zeigt in vergrößertem Maßstab in Draufsicht eine Ausführungsform des hinteren Gabelbaumendstückes in der unteren Hälfte teilweise horizontal geschnitten.
• Fig. 5 und 6 zeigen im Schnitt längs der Linie II-11 in Fig. 1 zwei weitere Ausgestaltungen des Querschnitts der Gabelholme.

The invention is illustrated in the drawing, for example, and described in detail below with reference to the drawing.

• Fig. 1 shows a top view of a boom.
• FIG. 2 shows a section along the line 11-11 in FIG. 1 through a fork leg.
• Fig. 3 shows an enlarged scale in plan view of the formation of the boom in the region of the front boom end, partially cut horizontally.
• Fig. 4 shows an enlarged scale in plan view of an embodiment of the rear boom end piece in the lower half partially cut horizontally.
• 5 and 6 show in section along the line II-11 in Fig. 1 two further configurations of the cross section of the fork legs.

The boom 2 shown in plan view in FIG. 1 has two spars 4, 6 and at the ends of the boom in each case boom ends, namely the front boom end 8 and the rear boom end 10, vertical rope bores being provided in the usual manner in the front boom end, while at the rear end a sail tensioning roller with a horizontal or vertical axis of rotation is arranged.

As shown in Fig. 2, the spars each have a profiled core 12 made of a rigid foam. Polystyrene foam is preferably used, since this absorbs moisture only to a negligible extent.

The foam core 12 is provided on two opposite sides, which correspond to the inside and outside of the spars, with flat surfaces 15, which form the bottoms of grooves 14 here. The surfaces 15 run essentially parallel to one another and to the bending axis X of the fork leg. The two other side surfaces 16, 18, which lie on the top or bottom of the boom or adjoin the flat surfaces, can be flat, but can also be curved outwards. In the cross-sectional shape according to FIG. 2, the transition takes place at the corners via transition radii 17, just as the flat grooves 14 on their lateral edges 19 can be designed with a cross-section with transition radii.

In the embodiments according to FIGS. 5 and 6, the cross sections of the fork legs are oval - FIG. 5 - or round - FIG. 6. The flat surfaces 15 'and 15 "go directly into the curved regions 16', 18 here 'or 16 ", 18" above, as shown in Fig. 5 top left.

The hard foam cores 12 are preferably made from a blank, for example from a Can be cut by milling or plate. Loops brought into their shape. The core need not extend in one piece over the entire length of the spar. Rather, shorter sections can also be brought to the necessary length by gluing on the end face.

The profiled foam core carries on its surface an inner or first layer 20 of synthetic resin-bonded fiber braid with fiber strands crossing at an angle between 30 ° and 60 °, preferably an angle of approximately 45 °, for the longitudinal extension of the bars. For this purpose, a customary fabric tube with fiber strands crossing at about 45 ° on the core is preferably used. But it can also be used strips of fabric that are cut at 45 ° to warp and weft, for example. Such strips are placed around the foam core so that they overlap with their free longitudinal edges. This overlap can take place, for example, in the area of one of the surfaces 16, 16 ', 16 "or 18, 18', 18" of the core. Such a layer also need not extend in one piece over the entire length. Rather, individual sections can be applied adjacent to one another. Inner layer 20 gives torsion resistance to the boom. The fiber network of this layer preferably consists of carbon fibers.

Lying on the inner layer 20, 20 ', 20 ", unidirectional fiber strands 22, 22', 22" are provided in the area of the opposing flat surfaces 15, 15 ', 15 ", which extend in the longitudinal direction of the spar The unidirectional fiber strands are expediently applied in the form of previously cured strips of synthetic resin-bonded unidirectional carbon fibers, so that there is no need for special tensioning means for these strands, with which the strands would otherwise have to be stretched and held parallel to one another during the curing of the resin in order to impair the strength The cured strips of unidirectional fiber strands 22 can have a substantially rectangular cross-section, as shown in Fig. 2. However, on their outside 23 they can also be curved in accordance with the cross-sectional shape of the fork leg, as in the embodiments according to FIGS Fig. 5 u nd 6. There, these strips 22 'and 22 "are formed in cross section as a circular section with a height h.

An outer layer 24 of a synthetic resin-bonded fiber braid is then provided over the entire length of the spars as a covering. For this purpose, a braided hose is preferably used, which can be easily stretched evenly when applied, gives a uniform surface and at the same time holds the inner layer 20 and the unidirectional fiber strands 22 during the impregnation with synthetic resin and during the curing of the synthetic resin under tension in contact with one another and at the core .

The outer layer 24 should consist of polyester or polyamide fibers, which give the boom good handling properties in use. A thin foam coating can be used to protect the skin and achieve high slip resistance. If the material of the outer layer is UV-sensitive, as is the case with aramid fibers, an opaque pigmented coating should be provided. Glass fiber fabric can also be used for the outer layer.

The spar profiles, as described above with reference to FIG. 2, can be placed after the impregnation of the inner layer 20 with synthetic resin and the previously cured strips of synthetic resin-bound unidirectional fiber strands 22 for curing on storage surfaces curved in accordance with the curvature of the boom spar. Due to the essentially flat outer sides of the profile according to FIG. 2, which lie parallel to the bending axis X of the profile, no special precautions need to be taken for holding the profile on the shape gauge. It is generally sufficient if means are provided at the ends of the spars with which they are held in abutment with the bearing surfaces. If appropriate, longitudinal guides for the profiles in the form of contact edges or the like may be expedient, in particular for the cross-sectional shapes according to FIGS. 5 and 6. The outer layer 24 is pulled onto the fork stiles which are dimensionally stable after the synthetic resin has hardened and is impregnated with synthetic resin. The bar can then be hung freely to harden this synthetic resin. The outer layer can also be applied wet on wet, that is to say soaked immediately after the inner layer and the unidirectional strips.

The fork legs are preferably made with a certain excess in length, so that they can then be brought to their final dimensions by severing the end pieces. If it is necessary to dismantle the boom, bushings can be laminated to the ends of the fork legs, if necessary with guide wedges or guide grooves. For this purpose, for example, appropriately prepared end pieces can be glued bluntly against the ends of the hard foam core. The bushings can be foam-coated on the outside with hard foam corresponding to the profile of the core of the spar, wherein a profile change is also possible within the end piece. For example, the roughly square cross-section of the spar profile according to FIG. 2 can be changed to a round or oval cross-section at the ends of the spar. The inner and outer layers as well as the unidirectional strands or strips 22 are expediently led beyond the end of such an end piece and cut off after curing.

In the manner described with spar ends assembled with bushings, for example, can be combined with known high-strength boom ends made of metal, in particular aluminum. But it can also be used boom end pieces that are constructed in a similar manner to the spar profiles. The spar profiles can also be rigidly connected to the boom ends.

The front end of a one-piece boom is shown in Fig. 3. The spars 4, 6 end in this embodiment in an end surface 26 to which the inner layer 20, the unidirectional strands 22 and the outer layer 24 extend, as can be seen from the upper half in FIG. 3, which shows a partial horizontal section. The boom end piece 28 is here a rigid foam molding which can have, for example, the same profile in cross section as the two spars which are connected via the fork end piece. Like the spars, the boom end piece is enclosed with an inner layer 30 made of a synthetic resin-bonded fiber fabric or braid, preferably made of carbon fibers. In the usual arrangement, vertical rope guide tubes 32 made of a plastic composite material are arranged in bores of the foam core and are held by the inner layer 30. A boom end piece 28 thus prepared is butt-glued against the end faces 26 of the two boom spars 4 and 6. To avoid thickening, the boom spars can be prepared for grinding the boom end pieces by grinding a bevel 34 at the ends of the unidirectional strands 22. After the fork end pieces 28 have been glued to the spars, impregnated unidirectional strips 36 are then placed on the inside and outside of the fork end pieces, which are graded in accordance with the sharpening of the unidirectional strips of the spars and thus enable a heel-free stocking with the unidirectional strips of the spars . The unidirectional strips can be held in place by thread windings after assembly.

The outer layer 38 is then applied to the preassembled boom end pieces. This outer layer can be a braided hose that extends at least as far as the shaft of the unidirectional strips over the boom stiles. However, it is also possible as an outer layer to apply as an outer layer a bandage wrapped around the ends of the spars and the boom end piece at an angle between 30 ° and 60 °, preferably at an angle of approximately 45 °. Such a bandage 40 is indicated in Fig. 3 in the lower half. As shown in dashed lines there, if necessary, two sanitary napkins with opposite slopes can be applied one above the other. In the area of the rope guide tubes 32, corresponding openings are then provided in the outer layer after curing.

In the same way as the front boom end piece, the rear boom end piece can also be firmly connected to the spars.

A releasable connection between the spars and the boom ends is shown in FIG. 4 in connection with a rear boom end 46. As already described above, bushings 47 are inserted into the ends of the boom spars 4, 6, via which the inner layer 20, the unidirectional strands 22 and the outer layer 24 are guided up to the end face 44 at the end of the spars 4, 6. The rear boom end piece 46 shown here is in turn a profile part made of a rigid foam, the profile in turn being designed in accordance with that of FIG. 2 or 6. A coupling tube 48 is held in the leg ends of the boom end piece 46. This can be done, for example, via a dimensionally stable molded piece, into which the coupling tube 48 is inserted and which, for example, can be butt-glued with its end against the rigid foam molding, which in this case can end, for example, in the region of the inner end 50 of the coupling tube 48. The boom end piece 46 with the lugs holding the coupling tube 48 is in turn covered with an inner layer 20, preferably made of carbon fibers. Unidirectional strips 52, 54 are also provided on the outside and here in any case also on the inside. Then again an outer layer 24 is applied on the outside, which can be a braided or fabric hose, but can also be a bandage.

In the embodiment according to FIG. 4, two sail tensioning rollers 58 with a horizontal axis are shown, which are mounted on an axle bolt 60 which can be inserted through tubes in bores 62 which are aligned with one another in the region of the legs of the boom end pieces 46. These tubes can penetrate the coupling tubes and thus contribute to their retention. For better guidance of the trimming tamping, the sail tensioning rollers are separated by the web 64, which contributes to the support of the bolt 60 by the bandage 87.

It is also possible to provide a guide tube 66 for holding a sail tensioning roller with a vertical axis in the area of the foam core, as shown in dashed lines in FIG. 4. Such a guide tube 66 can be supported radially via a thread winding 68 which is placed around the ends of the guide tube 66 and is guided over the outer circumference of the boom end piece via the unidirectional position. Such a thread winding 68 should expediently be attached below the outer layer 24. With this arrangement of the sail tensioning rollers 59, they would be mounted opposite on the axle pin 61 on the outside.

Guide tubes for fastening the axle bolts of the sail tensioning rollers can of course also be provided in the manner described in the case of a one-piece design of the boom.

Draw booms according to the invention Except for an outstanding rigidity and a very low weight. A boom with a length of 2.3 m can be produced, for example, with a weight of about 1 kg in a one-piece design.

According to the German standard DIN 7879, a boom must have a breaking load of 1000 N. High-performance aluminum booms are dimensioned for a breaking load of 2000 N. This results in a maximum bending moment of 600 Nm for a boom of 2 m length or span.

5 and 6 were dimensioned as follows to achieve the values mentioned.

The outer dimensions A = 36 mm and B = 30 mm were chosen for a boom spar with an oval cross-section according to FIG. 5. At the two ends with the smaller radius of curvature, mutually parallel flat surfaces 15 'are formed. A cross-section in the form of a circular section with a height h = 3 mm was selected for the strips 22 'of previously hardened synthetic resin-bonded unidirectional carbon fibers to be applied to these surfaces. This resulted in a cross-sectional area of approximately 30 mm 2 for the two strips 22 '. The strips 22 'were produced from a belt made of carbon fibers of the type T 800 H 12000 40 B from the company Torayka, Japan. The belts were impregnated with epoxy resin with 60 vol.% Resin and 40 vol.% Hardener and cured in the specified cross-sectional shape.

A carbon fiber braided sleeving of the type KB 400 S / Sigri from Sigri Elektrographit in Meitingen, FRG, was applied as an inner layer 20 'to the core 12' made of polystyrene foam with a density of 35 kg / m ³ and was coated with epoxy resin in a mixture of 50% by volume. Resin and 50 vol.% Hardener soaked. The pre-hardened strips 22 'were placed on this fiber tube and a carbon fiber braiding tube was applied as the outer layer 24', for which the same type was used as for the inner layer 20 '. This outer braided hose was impregnated with epoxy resin with 40 vol.% Resin and 60 vol.% Hardener.

After the resin had _hardened , the boom which had just been formed for the measurement had a bending stiffness of 119 x 10 ⁷ N mm ² and a maximum bending moment M _smax of 600 Nm around the bending axis XX. The bar weight was 194 g per meter.

A final diameter C of 33 mm was selected for a boom spar with a round cross section according to FIG. 6. For the strips 22 "made of unidirectional carbon fibers, a circular section with a height of 4.3 mm was selected as the cross-section, which corresponds to a cross-sectional area of approximately 50 mm ^2. The same types were used for the two braided sleeves and the two strips 22 'as for the 5. The boom boom according to FIG. 5. These were also prepared and applied in the same way as in the manufacture of the boom according to FIG. 5. The same bending stiffness of 119 × 10 ⁷ and a maximum bending moment M _smax = 600 Nm around the bending axis XX were achieved The bar weight was 254 g per meter.

Claims (16)

1. Boom of the wishbone-type for sailing boards, where the spars have a core, which is surrounded by a plurality of layers of a synthetic-resin. bonded fibre braiding or fabric with strands intersecting at an angle of between 30° and 60° to the longitudinal extension of the spars, and the spars are connected by means of boom end pieces, characterised in that the core (12) of the spars (4, 6) is composed of a rigid foam and has essentially plane surfaces (15) on the inside of the spars facing the sail and on the outside of the spars turned away from the sail, said plane surfaces extending across a significant section of the length of the core, in that on these plane surfaces (15) on a first layer (20) of synthetic-resin bonded fibre braiding or fabric there are arranged synthetic-resin bonded unidirectional strands (22) of carbon fibres, which extend in the longitudinal direction of the spars across the length thereof, and in that there is provided as an outer layer (24) above the unidirectional fibre strands (22) at least one additional layer from a synthetic-resin bonded fibre braiding or fabric, which extends across the entire length of the spars.

2. Boom according to Claim 1, characterised in that the unidirectional fibre strands (22) are applied in the form of previously cured strips from synthetic-resin bonded carbon fibres.

3. Boom according to Claim 1 or 2, characterised in that the core (12) is provided on the inside and the outside with flat grooves (14) for holding the synthetic-resin bonded unidirectional strands (22) of carbon fibres.

4. Boom according to any of the Claims 1 to 3, characterised in that the fibre braiding or fabric (24) of the outer layer is composed of polyester-or polyamide fibres.

5. Boom according to any of the Claims 1 to 4, characterised in that the core (12) is composed of foam polystyrene.

6. Boom according to any of the Claims 1 to 5, characterised in that there are designed at the ends of the spars (4, 6) sleeves (47) for connecting the spars with the front and rear boom end pieces (46).

7. Boom according to any of the Claims 1 to 5, characterised in that the boom end pieces (28) have a shaped core made out of rigid foam, which is provided with a layer (30) of a synthetic-resin bonded fibre braiding or fabric and which is provided at least on the outside with a flat groove for holding a previously cured strip (36) from synthetic-resin bonded unidirectional carbon fibres, which passes beyond the end faces (26) of the shaped cores such that the end pieces butting against the end faces (26) of the spars are fitted with the spars via the strips (36) and that the spar ends and the end pieces are provided with an outer layer (38) of synthetic-resin bonded fabric or braiding.

8. Boom according to Claim 7, characterised in that the outer layer (38) is designed as a fabric tube.

9. Boom according to Claim 7, characterised in that there is provided as an outer layer (38) a woven binding (40) wound at an angle of between 30° and 60°.

10. Boom according to Claim 9, characterised in that two bindings (40) wound in opposite directions are provided as an outer layer (38).

11. Boom according to any of the Claims 7 to 10, characterised in that perpendicular rope gud- ing tubes (32) are laminated into the front boom end piece (8, 28).

12. Boom according to any of the Claims 7 to 11, characterised in that in the rear boom end piece (10, 46) there are laminated aligned horizontal tubes for holding a pivot pin (60) for sail tension rollers (58).

13. Boom according to any of the Claims 7 to 11, characterised in that in the rear boom end piece (10, 46) in the axis of symmetry of the boom (2) there is laminated a guide tube (66) with perpendicular axis for holding a pivot pin (61), on either side of which are positioned sail tension rollers (59).

14. Boom according to Claim 13, characterised in that the guide tube (66) is supported radially by a thread winding (68), which is guided across the outer end curvature of the boom end piece (46).

15. Boom according to Claim 1, characterised in that the inner layer (20) and/or the outer layer (24) is formed by fibre braided tube.

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