WO2016168918A1

WO2016168918A1 - Composite kite line for kite boarding and method of manufacture of the same

Info

Publication number: WO2016168918A1
Application number: PCT/CA2016/050384
Authority: WO
Inventors: Peter G. Berrang
Original assignee: Epic Ventures Inc.
Priority date: 2015-04-20
Filing date: 2016-04-01
Publication date: 2016-10-27

Abstract

A composite kite line for kite boarding which includes a high tensile strength inner load-bearing line encapsulated in a sheath which increases die composite kite line buoyancy.

Description

[0001 ] Composite Kite Line for Kite Boarding and Method of Manufacture of the same FIELD

[0002] There is described a composite kite line used in kite boarding and a meuiod of manufacture of the same.

BACKGROUND

[0003] Kite boarding, sometimes also referred to as kite surfing, is an extreme sport where a person uses a kite, generally having a "C" or modified "C" shape, with an air-inflated leading edge to provide a rigid aerodynamic structure. The kite is attached to lines which are also attached to a harness worn by the kiter, allowing the kiter, while standing on a surfboard-like device, to be pulled along the surface of the water by the kite. U.S. Patent 4,708,078 teaches the first use of a kite design that could be re-launched from the water surface, which innovation spurred the sport of kite boarding.

[0004] Besides water-based kite boarding, kites are also used on land where the kiter stands on a skateboard type device (with wheels) travelling on, for example, packed sand, or sitting in a device with wheels for travel over a hard surface. Recently, kites have also been deployed by snow boarders for use over snow-covered areas.

[0005] Numerous patents have subsequently been filed to improve the various components used in kite boarding and by kiters. A key innovation was the design of a mechanical system that allows the kiter to de-power the kite (see FR 2,762,583). This innovation made kite boarding much safer as the kiter could de-power the kite during a gust of wind, or a sudden increase in wind velocity by simply moving the control bar towards the kite, thus changing the kite's shape and reducing the aerodynamic lift of the kite. [0006] U.S. Patent 6,988,694 and U.S. Patent 6,691,954 describe safety mechanisms for releasing the centre kite lines connecting the kite to the kiter, allowing the kite to de-power but still remain tethered to the kiter.

[0007] Most commercial kite designs use four lines, although five line kite systems are also known (see for example U.S. Patent 7,810,759). [0008] Prior art lines are thin, non-compressible, flexible and are generally 10 to 30 metres in length. Such prior art lines are made by tightly braiding ultra high molecular weight polyethylene (UHMWPE) fibres (trademarked as DyneemaR by DSM Dyneema, B.V., and as SpectraR by Honeywell International Inc.). Although it is possible to use other high strength polymer fibres, or even high strength carbon fibres, the use of UHMWPE fibre kite lines has become an industry standard.

[0009] To minimize fnctional and form drag, prior art lines have been designed for minimum diameter, while still providing sufficient line strength. Such lines generally have a diameter from 1.3 mm (racing lines) up to 2.0 mm, with a breaking strength of about 300 daN to 400 daN, and a line weight of about 1.7 g/m for 1.6 mm diameter lines.

SUMMARY

[0010] According to one aspect, there is provided a composite kite line for kite boarding which includes a high tensile strength inner load-bearing line encapsulated in a sheath which increases the composite kite line buoyancy.

[001 1 ] According to another aspect, there is provided a composite kite line assembly for kite boarding, which includes a plurality of high tensile strength lines each having a kiter or control bar attachment end and a kite attachment end. A length of each of the lines at the kiter or control bar attachment end being encapsulated in a sheath which provides added buoyancy to each of the lines. [0012] According to a further aspect there is provided a method of manufacture of a composite kite line for kite boarding which involves encapsulating a length of the composite kite line at a kiter or control bar attachment end in a sheath which increases the buoyancy.

[0013] The composite kite line, as described above, is highly buoyant in water. Such increased line buoyancy allows the kiter to better see the lines floating on the water surface, especially in the presence of waves and surf, thereby reducing the possibility of the kiter getting tangled within the lines while in the water, which entanglement can be dangerous. [0014] There are two alternative embodiments that will be hereinafter described. A first embodiment uses an outer tube having lumens to create the desired buoyancy. A second embodiments uses a closed-cell extruded polymer or elastomeric material to create the described buoyancy.

[0015] The sheath also imparts an element of rigidity to the composite line, making it stiffer. A stiffer line is advantageous as this will tend to cause the line to straighten and to stream away from the kiter when the line is slack, thereby reducing the tendency of the lines to entangle the kiter during a fall into the water, especially at times of breaking waves or rough sea conditions. Additionally, stiffer lines have the advantage of reducing entanglement of lines when the lines fall into the shore surf, which scenario commonly causes the lines to tangle, sometimes forming knots, making the process of untangling and unknotting such lines a difficult and tedious process. The tensile strength of a line is reduced by about 50% by the presence of a knot. In order to get the benefits, the sheadi should extend for at least two metres from the kiter or control bar attachment end.

[0016] It is preferred that the sheath be resilient, always returning to a "round" shape. Prior art lines tend to "flatten" over time as the line is steeped on or latterly compressed, thereby degrading the line's optimal "round" aerodynamic shape.

[0017] The sheath can be permanently shaped into a coil by thermoforming to hold such a shape, which shape can act to take slack out of lines. [0018] Although the sheath over the inner load-bearing line increases the composite kite line diameter, which dimensional increase increases the frictional and form drag of the composite kite line, such increased line diameter provides the kiter with a more secure manual grasp of the composite kite line, as does the compressibility of the composite kite line. In comparison, grasping the smaller diameter prior art lines is more difficult, as such lines generally have a hard and "slippery" feeling due to the fact that these lines are generally made from a low friction polyolefin (UHMWPE).

[0019] In this regard, the sheath outer extruded tubing is preferably comprised of a polymer, co-polymer, filled or unfilled, preferably the co-polymer EVA (ethylene vinyl acetate), which material, against itself, has a coefficient of static friction of about 0.6, which coefficient is much higher then, for example, braided UHMWPE fibre line, which material, against itself, has a static coefficient of friction of approximately 0.2.

[0020] Experimental testing shows that a composite line comprised of a 1.6 mm diameter fibre core, with an outer tubing having an outside diameter of 3.6 mm, with 8 lumens, with the lumen and tubing wall thicknesses in the range of 100 - 150 microns, such a configuration has a ratio of the cross-sectional area provided by the air-filled lumens, to the solid portion of the tubing cross-sectional area of about 3.5, which configuration reduces the overall line density from about 1 g/cm³ (widiout the air-filled lumens) to a composite line density of about 0.6 g/cm³ , thus greatly increasing the composite line buoyancy.

[0021 ] The use of tubing containing a plurality of lumens, where such tubing tightly fits around a load-bearing inner core also provides an element of compressibility to the composite line (due to the air inside the lumens able to compress) making manually grasping and tightly holding onto such a composite line easier, with a reduced tenancy of the line to cut into tissue.

[0022] The use of air-filled lumens minimizes the added weight to the composite line resulting from extruding a tubing over the inner load-bearing line. Experimental results show that for a load-bearing core line diameter of 1.6 mm, the composite line weight increases from about 1.7 grams/metre for the core line only, to about 3.7 grams/metre with the addition of an 8-lumen tube having an outer diameter of 3.6 mm, which represents an increase of 2.1 X the weight of the core line only. Based on field trials, doubling the core line weight by extruding multi-lumen tubing over the load-bearing core line does not appear to significantly affect the kite's performance.

[0023] The form and frictional drag coefficient of the composite line increases linearly with the diameter of the composite line. Thus, for a prior art line with a diameter of 1.6 mm, the form and frictional drag of such a line would be half of that for a composite line with a diameter of 3.2 mm. Too much line drag causes the kite's "back lines", which are the steering the lines, to "bow", affecting the de-power range and rate of response of the kite. The front lines are generally under much higher tension, and as such, tend to "bow" much less than the back lines for a given wind velocity. Although the addition of an extruded outer tubing over the inner load-bearing line provides various benefits to the kiter, such outer tubing increases the overall line diameter, thus increasing line drag. This increased drag can become significant, affecting kite performance, when the sheath length approaches about 20 metres. To minimize the increase in line drag, it is preferred that the sheath length be limited to amaximum of 20 metres , as measured from the control bar attachment of the kite.

[0024] It is preferred that the composite kite line is comprised of two sections. A section proximal to the kiter or control bar attachment end of 20 metres or shorter being covered with the sheath and a section toward the kite attachment end being unencapsulated load-bearing line known in the prior art. Such a hybrid kite line arrangement has the advantage of providing the kiter with the benefits of the kite line proximal to the kiter, where such benefits are most useful , and also reduce the overall line drag nearest the kite, where lower line drag is beneficial for kite performance. Generally, if a kiter becomes entangled in lines, such entanglement occurs in the line section proximal to the kiter.

[0025] Although the inclusion of multi-lumens provides the composite line with various positive features, if one or more of such lumens is ruptured, some water could like into the line, adding unwanted weight to the line. It is, therefore, preferred that the lumens be heat-sealed at various points along the sheath. Such heat-sealed points may be spaced 10 cm to 300 cm, but preferably 30 cm to 100 cm along the length of the line.

[0026] It will be appreciated that the composite kite line, as described, can replace various segments of prior art thicker lines, which lines can be 4 - 5 mm in diameter, that connect the kite control bar to thinner kite lines and bridles, distal to the kiter, thereby reducing the overall line weight and line drag.

[0027] Line visibility is a key parameter, especially when the lines fall into the water in waves and surf, as the kiter can easily become entangled in lines that are not readily visible. Accordingly, it is preferred that the colour of the sheath of the composite kite line is coloured one or more of yellow, orange, red or blue. Colours such as gray, white and black are more difficult to see in sunlight while kiting on the water, although such colours (except white) may be appropriate for kiting on snow. [0028] In the second embodiment, a closed-cell foamed tubing covering can be extruded over the inner load-bearing line, in conjunction with the extrusion of a second tubing over the first tubing, which second tubing is comprised of a polymer or co-polymer, which can be filled or unfilled with additives, which additives are well known by those skilled in the art. Such co- extruded second tubing over the first tubing provides mechanical protection for the soft underlying first tubing foam. Such alternate embodiment is also compressible, and buoyant, due to the closed-cell foam first tubing having a density range of 100 - 500 kg/m³ and an overall composite line density of less than 0.8 g/m\

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] These and other features will become more apparent from the fol lowing description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to be in any way limiting, wherein:

[0030] FIG. I is a perspective view of a composite kite line used in a kite line assembly for kite boarding.

[0031 ] FIG. 2 is a cross-sectional view a first embodiment of the composite kite line.

[0032] FIG. 3 is a cross-sectional view of a second embodiment of the composite kite line. DETAILED DESCRIPTION

[0033] A composite kite line will now be described. A first embodiment will be described with reference to FIG. 1 and FIG. 2. A second embodiment will be described with reference to FIG. 1 and FIG. 3. Structure and Relationship of Parts:

[0034] Figure 1 illustrates a kiter 10 engaged in the sport of kite surfing or kite boarding. The kiter stands on a kite board 12 on the surface of water 13 holding a control bar 14. Outside (steering) lines 15 are connected near the wingtips 17 of kite 18, and inside lines 16 are also attached to the kite. Outside lines 15 are connected to control bar 14 to provide for steering the kite. Inside lines 16 are connected to a hook mechanism on the kiter's harness. A safety leash line 1 1 connects the kiter to one or two of the inside lines to remain tethered to the kite in the event the kiter lets go of the control bar and also detaches from the hook connecting the inside lines. The kite 18 is not attached to the board 12. The kiter 10 manoeuvers kite 18 so as to pull the kiter and the board 12 across the surface of the water 13.

[0035] In accordance with the present invention, outside lines 15 and inside lines 16 are "composite" lines, as will hereinafter be further described with reference to FIG. 2 and FIG. 3. FIG. 2 illustrates a first embodiment of composite line, generally indicated by reference numeral 20. FIG. 3 illustrates a second embodiment of composite line, generally indicated by reference numeral 30. [0036] Fig. 2 is a cross-sectional view of composite line 20. Line 26 provides the tensile strength necessary for the kiter to remain tethered to the kite without risk of composite line 20 breaking. The multi-lumen polymer tube, shown as 22, which is extruded over line 26, provides only very minimal tensile strength to composite line 20. [0037] The multi-lumen tubing 22 covering line 26 illustrates 8 lumens, which lumens provide a radial symmetric shape around line 26, which allows composite line 20 to slightly compress when manually grasped by the kiter. Although 8 lumens are illustrated in Fig. 2, more lumens can, in theory, be incorporated within tubing 22, although the number of lumens is limited by machining tolerances and injection moulding orifices. A plurality of lumens also provides an element of redundancy in the event one or more lumens are ruptured, allowing water ingress.

[0038] The wall thicknesses of tubing 22, and lumens 24 therein, are made as thin as practically possible, to minimize weight, and to increase over composite line buoyancy. The outer wall thickness 21, inner wall thickness 23 and spokes 25 wall drickness can be 50 - 500 microns, but are preferably 100 - 300 microns. The length of spokes 25 can be 0.3 to 1.5 mm, but are preferably 0.5 to 1.2 mm. The number of lumens 24 can be from 2 to 20, but re preferably 6 - 10. [0039] The preferred method for making composite kite line 20, as depicted in Figure 2, is to extrude a lumen containing polymer tubing over a prior art kite line. A key aspect of such a process is diat the extrusion temperature does not exceed about 120 °C, as the melting point of UHMWPE fibre is in the range of 130— 136 °C. Too high an extrusion temperature would start to degrade the tensile strength of the underlying UHMWPE fibre core line. Such a relatively low extrusion temperature greatly limits the choice of possible polymer materials that can be used. EVA, a co-polymer, has various formulations that can meet this temperature requirement, and other parameters, such as UV resistance, flexibility, and resistance to moisture and micro-organisms.

[0040] The sheath also imparts an element of rigidity to the composite line, making it stiffen A stiffer line is advantageous as diis will tend to cause the line to straighten and to stream away from the kiter when the line is slack, thereby reducing the tendency of the lines to entangle the kiter during a fall into the water, especially at times of breaking waves or rough sea conditions. Additionally, stiffer lines have the advantage of reducing entanglement of lines when the lines fall into the shore surf, which scenario commonly causes the lines to tangle, sometimes forming knots, making the process of untangling and unknotting such lines a difficult and tedious process. The tensile strength of a line is reduced by about 50% by the presence of a knot. In order to get the benefits, the sheath should extend for at least two metres from the kiter or control bar attachment end.

[0041 ] It is preferred that the sheath be resilient, always returning to a "round" shape. Prior art lines tend to "flatten" over time as the line is steeped on or latterly compressed, thereby degrading the line's optimal "round" aerodynamic shape.

[0042] The sheath can be permanently shaped into a coil by thermoforming to hold such a shape, which shape can act to take slack out of lines.

[0043] Although the sheadi over the inner load-bearing line increases the composite kite line diameter, which dimensional increase increases the frictional and form drag of the composite kite line, such increased line diameter provides the kiter with a more secure manual grasp of the composite kite line, as does the compressibility of the composite kite line. In comparison, grasping the smaller diameter prior art lines is more difficult, as such lines generally have a hard and "slippery" feeling due to the fact that these lines are generally made from a low friction polyolefln (UHMWPE). [0044] In this regard, the sheath outer extruded tubing is preferably comprised of a polymer, co-polymer, filled or unfilled, preferably the co-polymer EVA (ethylene vinyl acetate), which material, against itself, has a coefficient of static friction of about 0.6, which coefficient is much higher then, for example, braided UHMWPE fibre line, which material, against itself, has a static coefficient of friction of approximately 0.2.

[0045] Experimental testing shows that a composite line comprised of a 1.6 mm diameter fibre core, with an outer tubing having an outside diameter of 3.6 mm, with 8 lumens, with the lumen and tubing wall thicknesses in the range of 100 - 150 microns, such a configuration has a ratio of the cross-sectional area provided by the lumens, to the overall tubing cross-sectional area of about 3.5, which configuration reduces the overall line density from about 1 g/cm³ (without the air-filled lumens) to a composite line density of about 0.6 g/cm³ thus greatly increasing the composite line buoyancy.

[0046] The use of tubing containing a plurality of lumens, where such tubing tightly fits around a load-bearing inner core also provides an element of compressibility to the composite line (due to the air inside the lumens able to compress) making manually grasping and tightly holding onto such a composite line easier, with a reduced tenancy of the line to cut into tissue.

[0047] The use of air-filled lumens minimizes the added weight to the composite line resulting from extruding a tubing over the inner load-bearing line. Experimental results show that for a load-bearing core line diameter of 1.6 mm, the composite line weight increases from about 1.7 grams/metre for the core line only, to about 3.7 grams/metre with the addition of an 8-lumen tube having an outer diameter of 3.6 mm, which represents an increase of 2.1 X the weight of the core line only. Based on field trials, doubling the core line weight by extruding multi-lumen tubing over the load-bearing core line does not appear to significantly affect the kite's performance. [0048] The form and frictional drag coefficient of the composite line increases linearly with the diameter of the composite line. Thus, for a prior art line with a diameter of 1.6 mm, the form and frictional drag of such a line would be half of that for a composite line with a diameter of 3.2 mm. Too much line drag causes the kite's "back lines", which are the steering the lines, to "bow", affecting the de-power range and rate of response of the kite. The front lines are generally under much higher tension, and as such, tend to "bow" much less than the back lines for a given wind velocity. Although the addition of an extruded outer tubing over the inner load-bearing line provides various benefits to the kiter, such outer tubing increases the overall line diameter, thus increasing line drag. This increased drag can become significant, affecting kite performance, when the sheath length approaches about 20 metres. To minimize the increase in line drag, it is preferred that the sheath length be limited to a maximum of 20 metres, as measured from the control bar attachment of the kite.

[0049] It is preferred that the composite kite line is comprised of two sections. A section proximal to the kiter or control bar attachment end of 20 metres or shorter being covered with the sheath and a section toward the kite attachment end being unencapsulated load-bearing line known in the prior art. Such a hybrid kite line arrangement has the advantage of providing the kiter with the benefits of the kite line proximal to the kiter, where such benefits are most useful, and also reduce the overall line drag nearest the kite, where lower line drag is beneficial for kite performance. Generally, if a kiter becomes entangled in lines, such entanglement occurs in the line section proximal to the kiter.

[0050] Although the inclusion of multi-lumens provides the composite line with various positive features, if one or more of such lumens is ruptured, some water could like into the line, adding unwanted weight to the line. It is, therefore, preferred that the lumens be heat-sealed at various points along the sheath. Such heat-sealed points may be spaced 10 cm to 300 cm, but preferably 30 cm to 100 cm along the length of the line.

[0051 ] It will be appreciated that the composite kite line, as described, can replace various segments of prior art thicker lines, which lines can be 4 - 5 mm in diameter, that connect the kite control bar to thinner kite lines and bridles, distal to the kiter, thereby reducing the overall line weight and line drag. [0052] Line visibility is a key parameter, especially when the lines fall into the water in waves and surf, as the kiter can easily become entangled in lines that are not readily visible. Accordingly, it is preferred that the colour of the sheath of the composite kite line is coloured one or more of yellow, orange, red or blue. Colours such as gray, white and black are more difficult to see in sunlight while kiting on the water, although such colours (except white) may be appropriate for kiting on snow.

Variations:

[0053] Fig. 3 is a cross-sectional view of second embodiment of composite line 30. Line 36 provides all of the tensile strength necessary for the kiter to remain tethered to the kite without risk of composite line 30 breaking. A first closed-cell foam tubing, shown as 34, is, preferably extruded over line 36, at the same time as second polymer tubing 32 is co-extruded over first tubing 34. [0054] The wall thicknesses of first foam tubing 34, can be comprised of a closed-cell ex tradable polymer or elastomeric foam, such as EPE (expanded polyethylene) or EPDM, preferably EPE, with an inside diameter the same as the diameter of core line 36, where first tubing 34 has a wall thickness of preferably less than 2 mm, preferably less than 1 mm. [0055] First foam tubing 34 is covered with second tubing 32, to provide mechanical protection for first foam tubing 34, and also to increase the coefficient of friction of the composite line 30, as first tubing 34 is, preferably, comprised of EPE, which is a polyolefin with a low coefficient of static friction. Second tubing 32, is, preferably, comprised of EVA, which has a higher coefficient of static friction than EPE.

[0056] The overall density of composite line 30, which line is comprised of an inner core line 36, a first or inner foam tubing 34, and a second or outer polymer tubing 32 is, preferably, less than 0.6 g/cm³ preferably less than 0.4 g/cm³. Advantages:

[0057] The advantages of the above described composite kite lines, although not necessarily common to all embodiments, include: the ability of the cross-sectional area of the sheath to be compressible and deformable in the lateral direction normal to the line direction when manually grasped and held;

the ability of the sheath to resiliently return to its original optimum round cross- sectional shape after the deforming lateral pressure is removed;

the sheath providing increased buoyancy to the composite kite line when floating in the water compared to the prior art lines, and less entanglement of the composite kite line when floating in the water in waves and shore surf;

the improved convenience for persons to manually grab and hold onto the composite kite lines, as they are compressible and deformable line system;

the improved security of manually grasping and holding the composite kite line system having a higher coefficient of friction compared to the prior art lines;

the improved ability of the tubing-covered inner line to minimize against sand and dirt intrusion into the braided fibre openings of the inner load-bearing line;

the improved ability of the tubing covering the inner line to provide stiffening of the line system, such that lines do not easily tangle or form knots compared to prior art lines; and

the provision of a round aerodynamic shape.

[0058] To fully appreciate the above described composite kite lines, one must re-visit the prior art. Prior art UHMWPE kite lines have an overall density of about 0.97 g/cm³, which makes them just buoyant in fresh water. Such minimal buoyancy, especially when the lines are floating in waves or surf, tends to submerge the lines, making them all but impossible to see. Such prior art lines are highly flexible, and hard, and do not compress or deform under load when wrapped around the limbs or appendages of a kiter, creating a dangerous tendency to cut into tissue when tightly wrapped around a person's limbs or appendages. They also tend to tangle easily, especially when un-tensioned lines are floating on, or below the surface, in waves and surf. Thus, the thin diameter, and the high tension in the lines when the kite is powered, presents a major risk of injury to the kiter if any part of the kiter becomes entangled in the lines. There is a similar danger of injury to any person assisting the kiter during launch and recovery of the kite at or near the shore, to bystanders on the shore or beach, or to other kiters in the water during any cross-over of lines, and the entanglement of lines between two kiters in the water.

[0059] The use of non-round kite lines, such as lightweight ribbons is problematical, as a round cross-sectional shape is the basis of line's aerodynamic stability, which minimizes vortex shedding and associated line strumming. Because of its axial symmetry, a circular cross- sectional line will also induce the least degree of line twisting. Also, lines having a low-drag, airfoil-shape cross-section are impractical, as field testing of such lines has shown them to twist and oscillate, at times creating a "humming" sound.

[0060] In this patent document, the word "comprising" is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article "a" does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements.

[0061 ] The scope of the claims should not be limited by the illustrated embodiments set forth as examples, but should be given the broadest interpretation consistent widi a purposive construction of the claims in view of the description as a whole.

Claims

What is Claimed is:

1. A composite kite line for kite boarding, comprising:

a high tensile strength inner load-bearing line encapsulated in a sheath which increases the composite kite line buoyancy.

2. The composite kite line of Claim 1, wherein the composite kite line has a kiter or control bar attachment end and a kite attachment end, and a length of the inner load- bearing line that is encapsulated in the sheath is at least two metres extending from the kiter or control bar attachment end.

3. The composite kite line of Claim 1 , wherein the sheath provides increased rigidity to the composite kite line.

4. The composite kite line of Claim 1 , wherein the sheath has 2 to 20, air-filled lumens running longitudinally along the length of the sheath.

5. The composite kite line of Claim 4, wherein the sheath has 6-10 lumens radially positioned around the inner load-bearing line.

6. The composite kite line of Claim 4, wherein the sheath increases the buoyancy of the line by having a ratio of a cross-sectional area provided by the air-filled lumens, to the solid portion of the sheath cross-sectional area, being in a range of 10: 1 to 4: 1.

7. The composite kite line of Claim 4, wherein the lumens provide a density of less than 0.8 g/cnr' to the composite kite line.

8. The composite kite line of Claim 1, wherein the sheath is comprised of a polymer material.

9. The composite kite line of Claim 8, wherein the outer surface of the sheath has a static coefficient of friction when in contact with an epidermal skin surface of a palm of a kiter, that is greater than the static coefficient of friction of the inner load-bearing line in contact with the epidermal skin surface of the palm of the kiter.

10. The composite kite line of Claim 9, wherein the static coefficient of friction between the outer surface of the sheath and the epidermal skin surface of the palm of the kiter, is at least 0.4.

1 1. The composite kite line of Claim 8, wherein the polymer material is Ethylene Vinyl Acetate (EVA).

12. The composite kite line of Claim 8, wherein said polymer has a melt extrusion temperature of 130 °C or lower.

13. The composite kite line of Claim 1 , wherein the weight of the sheath is less than two times the weight of the load-bearing line.

14. The composite kite line of Claim 1 , wherein the sheath has an outside diameter of between 2.2 mm and 4.0 mm.

15. The composite kite line of Claim 1 , wherein the inner load-bearing line is comprised of ultra-high molecular weight polyethylene (UHMWPE) fibres.

16. The composite kite line of Claim 15, wherein the inner load-bearing line has a diameter of between 1.3 mm and 1.7 mm.

17. The composite kite line of Claim 1 wherein the sheath is comprised of a first foam tubing covered with a second tubing.

18. The composite kite line of Claim 17, wherein the first foam tubing is comprised of a closed-cell extruded polymer or elastomeric material.

19. The composite kite line of Claim 17, wherein the first foam tubing is comprised of expanded polyethylene (EPE) with a density range of 50 - 500 kg/W and wherein the first foam tubing provides the composite kite line with an overall density of less than 0.8 g/cm\

20. The composite kite line of Claim 19, wherein the density of the first foam tubing is in the range of 100 - 200 kg/nr¹ and the overall density of the composite kite line is less than 0.5 g/cm\

21. The composite kite line of Claim 17, wherein the first foam tubing is comprised of Ethylene Propylene Diene (EPDM) with a density range of 200 - 500 kg/m\

22. The composite kite line of Claim 17, wherein the second tubing is comprised of Ediylene Vinyl Acetate (EVA), with a wall thickness range of 0.05 - 1.0 mm.

23. The composite kite line of Claim 22, wherein the wall thickness range is 0.1 - 0.3 mm.

24. The composite kite line of Claim 1 , wherein the sheath is permanently shaped into a coil which acts to take slack out of the lines.

25. The composite kite line of Claim 2, wherein a maximum length of the sheath is 20 metres.

26. The composite kite line of Claim 4, wherein the lumens are heat-sealed at various points along the sheath, thereby forming water tight compartments.

27. The composite kite line of Claim 1 , wherein the sheath is coloured to improve visibility.

28. The composite kite line of Claim 1 , wherein the sheath is resiliently deformable, returning to its original shape when a deforming force is removed.

29. A method of manufacture of a composite kite line for kite boarding, comprising:

encapsulating a length of the composite kite line at a kiter or control bar attachment end in a sheadi which increases the buoyancy.

30. The method of Claim 29, wherein the encapsulating is by co-extrusion of polymer material having an inner tubing which encapsulates the inner load-bearing line and an outer tubing that protects the inner tubing.

31. The method of Claim 29, wherein not less than two metres and not more than 20 metres of the inner load-bearing line is encapsulated.

32. The method of Claim 29, wherein the sheath is comprised of a polymer material which is resiliently deformable, returning to a round shape when a deforming force is removed.

33. The method of Claim 29, wherein an outer surface of the sheath has a static coefficient of friction when in contact with an epidermal skin surface of a palm of a kiter, that is greater than the static coefficient of friction of the inner load-bearing line in contact with the epidermal skin surface of the palm of the kiter.

34. The method of Claim 29, wherein the sheadi provides added rigidity to the inner load- bearing line.

35. The method of Claim 33, wherein the outer surface of the sheath has a static coefficient of friction when in contact with the epidermal skin surface of the palm of a kiter, of at least 0.4.

36. A composite kite line assembly for kite boarding, comprising:

a plurality of high tensile strength lines each having a kiter or control bar attachment end and a kite attachment end, a length of each of the lines at the kiter or control bar attachment end being encapsulated in a sheath which provides added buoyancy to each of the lines.

37. The composite kite line assembly of Claim 36, wherein each sheath increases a rigidity of the lines to reduce entanglement.

38. The composite kite line assembly of Claim 36, wherein each sheath is comprised of a polymer material.

39. The composite kite line assembly of Claim 36, wherein the outer surface of the sheath has a static coefficient of friction when in contact with an epidermal skin surface of a palm of a kiter, that is greater than the static coefficient of friction of the inner load- bearing line in contact with the epidermal skin surface of the palm of the kiter.