Sail, sailcloth, method for producing them and apparatus for carrying out said method

Abstract

 The invention relates to sail cloths for producing sails for sailing ships, in order to obtain radar reflection from the sails when the sailing ships cruise at sea, according to the invention a number of electrically conductive elements (14) are included in the sail cloth structure.
These conductive elements (14) can for instance be formed by metal foil, and/or conductive polymer foil and/or metal wire elements. These elements (14) can be fastened by either gluing, stitching or plasma torch action.
The invention also relates to a method and apparatus for producing radar reflecting sails.

Description

[0001] The present invention relates to sailcloth for producing sails for sailing ships. Sailing ships cruising at sea commonly use a radar-reflector which is hoisted in the mast or the rigging so that large vessels or other vessels having a radar system can detect these sailing ships and avoid collision or other accidents. These radar reflectors have to be hoisted in a correct position in order to function properly. During heavy weather the reflector can get out of order or even get lost overboard. Furthermore due to their limited dimensions or too low position they cause a small echo on the radar screen of the vessel carrying the radar system. This may lead to not noticing the sailing ship and ensuing danger of collisions.
Furthermore in case of breakage of the mast the classical radar reflector can be lost.

[0002] The object of the invention is overcoming these disadvantages and providing a simple structure which is capable of reflecting radar waves and is already included in a part of the rigging.

[0003] This object is reached in that, a number of electrically conductive elements are included in the sail cloth structure. The use of electrically conductive elements in the sails enhances the electromagnetic signature of boats carrying such sail, rendering them more visible to radar and thereby improving the safety at sea.

[0004] In case of breakage of the mast a jury rig can be set-up and a new radar reflecting sail set thereby restoring better radar visibility to vessels or air search aircraft.

[0005] According to a first embodiment the electrically conductive elements are formed by metal foil elements including at least a substantial part of the structure of the sail cloth.

[0006] A second embodiment is characterised in that the electrically conductive elements are formed by conductive polymer foil elements including at least a substantial part of the structure of the sail cloth.

[0007] A third embodiment is characterised in that the electrically conductive elements are formed by metal wire elements including at least a substantial part of the structure of the sail cloth.

[0008] A fourth embodiment is characterised in that it is mainly according to one or more of the above embodiments but a substantial pan of the structure of the sail cloth is free of electrically conductive elements. This provides a location for transparent viewing "windows".

[0009] The electrically conductive element can be fastened on a substrate by gluing, stitching, spraying or plasma torch action respectively.

[0010] The invention also relates to a method for producing sail cloth and sails. and a new way of producing and reinforcing such sail. In order to facilitate the use of this type of sail by as many sail boats as possible, it is important to ensure that its production cost will remain low and a simple way of laminating such sail and simultaneously finishing its corners holding points is proposed.

[0011] The conductive layer used can be a metal foil or a conductive polymer foil. It has to be arranged in such way as to maximise the area exposed to incoming radar electromagnetic waves. This can be achieved by a conductive film or conductive strips or closely spaced metal wires or a combination of them covering and reinforcing as much as possible the polymer film.

[0012] A first practical and simple way of implementing the conductive layer on existing sails is to glue or stitch thin metal foils on the cloth of the sail. Another solution is to deposit a thin layer of metal with a plasma torch or spray a metal loaded polymer on the sail. This can be done on both sides of the sail to give it a distinctive metallic look.

[0013] Conductive wires or threads can also be used in the weaving of classical sail cloth to achieve the necessary electromagnetic reflectivity.

[0014] For new sails, it is advantageous to integrate the conductive material into the composite structure of the sail and additionally make use of their mechanical properties.

[0015] A conductive layer made of a few tens of microns of metal can be laminated with a polymeric substrate such as polyester or polyamide or polyethylene. The film of metal will provide additional strength to the polymeric substrate. Nevertheless, such thin membrane is reinforced by strands of metallic wires mixed or not with polymer fibres or threads as described below.

[0016] The invention will now be elucidated referring to the accompanying drawing.

Fig. 1 is a plan view of a triangular sail produced according to the method of the invention.

Fig. 1A shows a detail of a corner of the sail of Fig. 1.

Fig. 2 is a perspective view of an apparatus for producing a sail according to the invention.

Fig.3 is a schematic diagram of the apparatus according to fig.2.

[0017] In the following the term strand will be used indifferently for strands of wires or single wire. The wire metal can be the same as the membrane material or different. As it will finally constitute the loop through which the sail will be attached to halyard sheet and tack, the material will be selected for its strength, durability and ease of production in wire of small diameter of typically 20 to 200 microns. More wires of the smaller diameter will be needed to make the sail more pliable but that will be at the expense of production time and cost.

[0018] The strands used to reinforce the membrane will be disposed in an innovative straight triangular mesh arrangement shown in figure 1 such that for any elementary area of the sail, there are strands connecting it to the 3 corners of the sail, 2, 2a and 2b. The basic sail membrane with or without a loosely woven cloth covering the sail area can be shaped using any normal sail making techniques with shaped panels glued or stitched together. In order to place the reinforcement strands on the membrane, the membrane is slightly tensioned between one corner and one point on the opposite edge, and left free of tension in the perpendicular direction and at the other 2 corners. The strand coated with glue or weldable polymer or naked is rolled out under controlled tension and glued or hot welded or electrically welded on the membrane metal foil along the line of tension created in the membrane. The strands lay-up start from the edge of the sail, runs up to the opposite corner, pass around an eyelet specifically placed at the corner point and runs back to the starting edge at a point adjacent to the starting point. The point of tensioning of the membrane is moved to a place adjacent to the previous one. The next strand start from this new point on the edge, runs up and round the corner eyelet and back to the edge at an adjacent point, and so on. The process is repeated for the three sides of the sail, running strands around the opposite corner eyelet, thereby ensuing a complete coverage of the sail surface. The eventual need to have variable strength or stiffness in various zone of the sail can be accommodated by varying the pitch between strands, and close to the corner shorter runs of strands around the eyelet can be used as local reinforcement. In the case of a sail with reefing points, the process of laying the strands can be repeated around these reefing points. It is to be noted that the sail being held up on the boat rig by halyard and sheet, there is no need to lay on the sail much more strands that what is necessary to hold a force equal to the breaking force of the halyard and sheet.

[0019] It is to be noted that the process described above for the most commonly used triangular sails can also be used for quadrangular sails or awning tensioned on three or more points.

[0020] The process of rolling on the sail the strands being essentially unidirectional, it can be executed by hand or simply automated as described below and in the attached figure 2 and 3.

[0021] The radial arm 1 is positioned above the eyelet 2 attached to one corner of the sail membrane 3, and the tensioning device 4. The radial arm 1 carries a strand laying table 5 moving up and down the arm driven by an electric motor. The strand laying table 5 carries the strand feeder 6 and pressing roller 7 needed to lay and glue or weld the strands on the membrane. The arm can be a single arm attached above a flat surface or can have a counter arm 8 and second moving table 9 synchronised with the laying table and carrying the counter roller 10 positioned under the sail to react the pressing roller force. The pressing roller in action is always trailing the strand feeder. The strand laying table is organised such that the feeder and pressing rollers are offset from the centre line of displacement. The table rotates by 180 degree when arriving at the eyelet, thereby ensuring that the strand is wrapped around the eyelet with the pressing roller again trailing the feeder on the run back to the starting point. The rotating action can be triggered by roller riding on a ramp positioned on the radial arm at the level of the eyelet and mechanical linkages lifting first the pressing roller before driving the rotation of the strand laying as the table passes along the position of the eyelet and reverses toward the starting point on the edge of the sail. The same lifting and rotation action can also be triggered by an optical or magnetic sensor detecting the proximity of the eyelet and executed by electromagnetic or pneumatic actuators controlled by an electronic sequencer.

[0022] Finally a finishing film of polymer or fine cloth can be glued on top of the strands to protect them against environment aggressions or abrasion. A sleeve is placed on the strands running around the eyelet to hold them together and protect them. Tapes can be added to seal the edges and make a sail compatible with luff groove system found on many sailboats.

Claims

1. Sail cloth for producing sails for sailing ships, characterised in that, a number of electrically conductive elements are included in the sail cloth structure

2. Sail cloth according to claim 1, characterised in that, the electrically conductive elements are formed by metal foil elements including at least a substantial part of the structure of the sail cloth

3. Sail cloth according to claim 1, characterised in that, the electrically conductive elements are formed by conductive polymer foil elements including at least a substantial part of the structure of the sail cloth

4. Sail cloth according to claim 1, characterised in that, the electrically conductive elements are formed by metal wire elements (14) including at least a substantial part of the structure of the sail cloth.

5. Sail cloth according to one or more of the claims 1 through 4, characterised in that, at least a substantial part of the structure of the sail cloth is free of electrically conductive elements.

6. Method for producing sail cloth according to one or more of claims 1 through 5, characterised in that the electrically conductive elements are fastened on a substrate by gluing.

7. Method for producing sail cloth according to one or more of claims 1 through 5, characterised in that the electrically conductive elements are fastened on a substrate by stitching.

8. Method for producing sail cloth according to one or more of claims 1 through 5, characterised in that the electrically conductive elements are fastened on a substrate by spraying.

9. Method for producing sail cloth according to one or more of claims 1 through 5, characterised in that the electrically conductive elements are fastened on a substrate by plasma torch action.

10. Method for producing sail cloth according to one or more of the claims 1 and 4, characterised in that metal wire elements (14) are laid in a straight triangular mesh arrangement on at least a substantial part of the surface structure of the sail cloth (3), in which the metal wire elements are strands (14) comprising wire strands or single wires.

11. Method for producing sail cloth according to claim 10, characterised in that the metal strands (14) are laid in a straight triangular mesh starting from an edge of the sail (3), runs up to the opposite corner (2), passes around an eyelet (2) specifically placed at the corner point and runs back to the starting edge at a point adjacent to the starting point.

12. Method for producing sail cloth according to claim 10 or 11, characterised in that the metal strands (14) are started from several points along the edge of the sail adjacent to the previous one.

13. Method for producing a triangular sail cloth according to one or more of claims 10, 11 or 12, characterised in that the method is repeated for the three (or four) sides of the sail (3), running strands (8) around the opposite corner eyelet (2a,2b) thereby ensuring a complete coverage of the sail (3).

14. Apparatus for applying the method of one or more of claims 6 through 13, in particular for attaching strands of conductive material on a sail substrate(3), comprising a support surface (10) on which the sail substrate(3) is placed, whereas above the support surface (10) an arm (2) is spaced from which the strands (14) are dispensed, characterised in that a strand laying table (5) is mounted on the radial arm (1) guiding the strand (14) coming from a strand feeder (6), carrying a supply of rolled up strand (14), to a pressing roller (7) pressing the strand (14) on a sail substrate (3) supported by a counter roller (10) carried by a moving table (9) on a counter (8).

15. Apparatus for applying the method of one or more of claims 6 through 14 characterised in that the support surface (11) carries a pin (12) for an eyelet (2) in a corner of the sail substrate (3), whereas at the opposite end of the sail substrate (3) a spring actuated tensioning device (4) is mounted.

16. Apparatus for applying the method of one or more of the claims 6 through 15, characterised in that means are present for feeding the edge of the sail into the tensioning device (4) to execute automatically the displacement between consecutive runs up to the corner eyelet and back.

Drawing