Sail membrane

Abstract

Sail membrane made of a woven fabric of synthetic fibers, with said fabric having a microroughness in the form of groove families crossing one another arranged so as to achieve a density of 5 to 25 grooves/mm deposited on or integrated into said fabric structure.

Claims

1. A sail membrane made of a woven fabric of synthetic fibers, characterized in that said fabric has a microroughness in the form of intersecting groove families arranged so as to achieve a density of 5 to 25 grooves/mm and deposited on or integrated into said fabric surface; wherein the grooves are generated by calendering both sides of the sail membrane.

2. The sail membrane according to claim 1, characterized in that the grooves, measured from valley bottom to top of crest, have a height amounting to 25 to 75% of the groove spacing from crest to crest.

3. The sail membrane according to claim 1, characterized in that said membrane has 8 to 20 grooves/mm.

4. The sail membrane according to claim 1, characterized in that the grooves are arranged at an angle of 30 to 60 in relation to the extension of the warp yarns.

5. The sail membrane according to claim 1, characterized in that the intersecting groove families have an intersection angle of between 80 and 120.

6. The sail membrane according to claim 1, characterized by hydrophobization.

7. A sail manufactured from the sail membrane of claim 1.

8. The sail membrane according to claim 1, characterized in that the grooves, measured from valley bottom to top of crest, have a height amounting to 40 to 60% of the groove spacing from crest to crest.

9. The sail membrane according to claim 1, characterized in that the grooves are arranged at an angle of approximately 45 in relation to the extension of the warp yarns.

10. The sail membrane according to claim 1, characterized by hydrophobization achieved by means of perfluoropolyalkylene and/or a nanoparticle coating.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is explained in more detail by way of the enclosed figures where

(2) FIG. 1 shows a sailcloth fabric after calendering, 60 magnified, and

(3) FIG. 2 shows another sailcloth fabric after calendering, 300 magnified, and

(4) FIG. 3 shows a third sailcloth fabric after calendering, 60 magnified,

DETAILED DESCRIPTION OF THE INVENTION

(5) In FIG. 1 a sailcloth is illustrated that consists of a woven polyamide fabric with its clearly visible warp and weft yarns extending perpendicularly to each other and being of plain weave design. By means of a calendering roll with X-corrugations an X-pattern of intersecting grooves is embossed into this fabric, said grooves running diagonally to the direction of the fabric. The individual grooves are spaced at approximately 125 m corresponding to 8 grooves/mm. The sets of grooves running diagonally from top left to bottom right and from bottom left to top right intersect at an angle of approximately 90. The embossing pressure was 300 N/mm.sup.2, the roll temperature was adjusted to a value of 200 C.

(6) FIG. 2 illustrates a sailcloth made of a polyamide fabric of plain weave design with 20 grooves/mm, magnified 300. Clearly visible are the crests of the intersecting grooves extending diagonally to the direction of the fibers and the enclosed diamond-shaped depressions made in the fiber surface, with said chain-like depressions continuing in fiber direction. The sailcloth was treated by means of a cross-corrugation calender at 200 C. and 300 N/mm.sup.2.

(7) In FIG. 3 a sailcloth is illustrated that consists of a woven polyester fabric with its clearly visible warp and weft yarns extending perpendicularly to each other and being of plain weave design. By means of a calendering roll cross-corrugations were embossed into this fabric, said corrugations running diagonally to the fiber direction. The individual grooves are spaced at 50 m from groove to groove corresponding to a groove density of 20 grooves/mm. The families or sets of grooves running diagonally from top left to bottom right and from bottom left to top right intersect at an angle of approximately 95. The embossing pressure was 400 N/mm.sup.2 at a roll temperature of 200 C.

(8) Examinations carried out on a raw polyamide woven fabric processed by means of a corrugated roll with 8 lines/mm at a temperature of 200 C. have shown that after calendering the permeability to air at 20 mm WC of 600 to 800 l/dm.sup.2/min was significantly reduced to 30 to 40 l/dm.sup.2/min for the gray cloth. Further reduction is to be expected for the dyed cloth. In case of the coated sailcloth the permeability to air goes down to zero, with the coating amount being considerably lower for the calendered cloth. A lower amount of coating enables the weight of the finished sail to be reduced and such a saving in weight can be utilized to apply reinforcing measures (reinforcing yarns).

(9) With a view to achieving optimum results the treatment by means of the corrugated roll must always be performed on both sides.

(10) Examination series carried out on a polyamide gray cloth processed by means of a cross-corrugation roll with 20 lines/mm at a temperature of 200 C. have shown a significant interdependency between air permeability and pressure, with an optimum at 200 to 400 N/mm.sup.2:

(11) TABLE-US-00001 Pressure N/mm.sup.2 Permeability to air, l/dm.sup.2/min 100 100 150 70 200 40 300 30 400 30

(12) The gray cloth had been calendered on both sides. With dyed cloth the permeability (at 300 to 400 N/mm.sup.2) was found to be 10 to 20 l/dm.sup.2.

(13) For the purpose of determining the resistance to air sail membrane samples were tested in a wind tunnel using an MAV scales test piece (6-component strain gauge MAV scales) at a windspeed of 18 m/s. The MAV scales test piece was a trapezoidal wing of small extension having a symmetrical profile. The leading edge sweep was 36, the rear edge was straight. The wing area was covered with the cloth patterns in such a manner that the covering embraced the top side of the wing completely while just abt. a quarter of the bottom side was covered.

(14) For a non-corrugated sail membrane the measuring results showed a coefficient of drag value C.sub.Wa of 7.0810.sup.3 on average, for a membrane with intersecting corrugations comprising 10 grooves/mm a value of 6.5410.sup.3 and with 20 grooves/mm a value of 6.410.sup.3. These are mean values determined from 500 measurements on eight measuring points.

(15) The sail membrane samples were made of a polyester/polyethylene mixed woven fabric.