WO2007059345A2 - Horticultural netting with dimensional control - Google Patents

Abstract

In a preferred embodiment, a raschel knitted diamond or hexagonal mesh (18) net (10) is manufactured such that is may be dispensed and laid in place to equate to a length, and such a length can be identified on the packaging for the mesh net (10) The desired length is fixed during or after knitting by inclusion of a relatively non-stretchable portion (112) extending lengthwise in the net and fixed at lengthwise intervals to the meshing The portion may be a line such as a strip of plastic, a rope or other flexible line interwoven through the meshing and fixed to the meshing at intervals by tying or otherwise Additionally, the relatively non-stretchable portion can be a lengthwise strip of the netting suitably shrunk to provide a reduced rope length of the shrunken portion The net (10) is preferably stretched widthwise before bagging and is placed in the bag in a layered zigzag format.

Description

HORTICULTURAL NETTING WITH DIMENSIONAL CONTROL

FIELD OF THE INVENTION

The present invention relates generally to a protective net for horticulture. More particularly, the present invention relates to such nets having dimensional control, methods of providing such nets, methods of manufacture, methods of packing such nets, and methods of installation.

BACKGROUND OF THE INVENTION

Vineyards and orchards produce valuable fruit and other food crops for eating and for making wine and other beverages. Particularly when the fruit is ripening it is subject to depredation by birds which can cause not only crop damage, but crop loss. During ripening sugar content increases making the fruit highly attractive to birds and other vertebrate pests. If the fruit becomes injured or damaged as a result of predation it becomes increasingly susceptible to bunch rot pathogens. The bunch rot complex of fungi and bacteria establish infections most often through a wound on the surface of fruit. These fungi and bacteria are commonly present on soil debris and many plant surfaces, including the fruit itself. Bird saliva, ants, mites and other insects can also inoculate the wound with various undesirable pathogens. Because of the close proximity of pathogens to fruit, the rot process can begin almost as soon as the skin of the grape is compromised. Any injury to the skin of ripening berries, grapes or other fruit from large to very small, is a potential entry point for these pathogens causing infection on the damaged fruit which can and does spread to adjacent otherwise undamaged fruit. Additional wine flavor defects can be caused by the body parts of the insects attracted to the compromised grapes. Some insects employ bitterness and other flavors as a defense mechanism against predators. A local example is the Multicolored Asian Lady Beetle that gives of a foul odor when crushed. A single beetle could contaminate a large volume of wine.

In the case of wine or table grapes, "bird peck" damage can be very costly, one grape with broken skin can lead to a fungal infection and loss of the whole grape cluster. "Bunch rot" can include many different kinds of organisms many of which can be of detrimental affect to wine quality, for example, Botrytis cinerea. It is known that Botrytis can cause clarification issues and undesirable flavor modifications." Moreover, winery equipment can be contaminated with various organisms that can be very resistant to disinfection and cleaning causing problems in future use of the equipment.

It is difficult and thus relatively expensive to cull rotting grapes; such culling almost always necessitates removal of the infected grape cluster. There are two typical methods of culling, field culling from the vine and conveyor culling at the winery, both cumbersome and labor intensive. For grapes that are machine harvested, culling is not possible once the harvester removes the fruit and mixes the affected grapes in large gondolas that can hold tons. In such a case, a small amount of bird peck induced rot can cause large-scale crop rejections by the fruit buyer and or winery resulting in a severe economic loss to the grower. If the rot is not detected and the fruit is not rejected the winery suffers a loss of flavor and inclusion of various wine flavor defects.

Such bird induced damage to fruit can be reduced or prevented by a number of methods include killing the birds, scaring away the birds, trapping the birds, and providing barriers between the fruit and birds. Killing the birds is typically illegal and inhumane. Falconry, propane cannons, and passive means such as flash tape or balloons are utilized to scare the birds. If at all successful, these methods often only serve to temporarily move the birds to another location. It has been found that birds habituate within a few days to most negative stimuli and simply ignore such and stop moving. Similarly, trapping the birds and temporarily removing them from the area has not proven effective.

Net-type barriers can offer complete and continuous exclusion protection twenty four hours a day. With respect to vineyards, where grapes are grown in rows with multiple vines supported by trellis', the netting is typically utilized in one of three ways: 1) by draping netting over single or multiple rows of vines, 2) by securing netting in narrow panels along the sides of trellis rows to protect only the zone of the vine that bears fruit, or 3) by suspending the netting from a permanent overhead structure.

The most common method is to lay a net over the vine canopy, that is, simply over the entire vine. The efficiency of this method is facilitated by the great number of widths available, particularly for knitted nets. Such nets can cover two, three, four or more rows in one pass. Growers who want to avoid covering the entire canopy with net can instead install narrow nets at the side of the canopy to cover the fruit zone. This practice is labor intensive, particularly where such installation and removal occurs annually. Such side net must be physically attached to the trellis, that supports the row of vines, at multiple points which greatly increases installation and removal costs.

Nets can also be used in constructing bird exclosures. Bird exclosures require a permanent support structure of posts and wires than can interfere with the functioning of other critical vineyard equipment such as harvesting machines. Exclosures also necessitate the use of heavier and more expensive netting.

There are four common types of netting used: extruded, warp knitted, knotted and multi-filament knotless. One common type of modern commercial bird net is made as a single piece by extrusion. The resulting extruded net is stiff and has sharp edges requiring that workers wear leather gloves when working with it. Extruded net is stiff and has a property known as shape memory. Shape memory makes it difficult to pull the net in place. It must be manually secured below the fruiting zone, or it will revert to its original shape, lifting away from the fruit and allowing entry by birds from below.

The width of extruded net is limited to the width of the extrusion tooling. Extruded net is made in such a way that it generally must all be the same color, eliminating the potential for colored markers to be included in the manufacture of the net. Such colored markers can facilitate installation and removal by providing reference lines for positioning feedback when installing the net. The absence of such markers makes it hard to center the net over the canopy. Similarly, the edge cannot be made a contrasting color to make it easy for a worker to locate the edge. Extruded nets are handled on rolls, which are heavy; installation and removal require the use of heavy, expensive and potentially dangerous hydraulic equipment.

Extruded net offers the advantage that its dimensions are fixed; it cannot be stretched and therefore cannot be installed with the incorrect length or width.

Knitted net is more flexible than extruded net. A common form of knitting is warp knitting, with raschel knit being a class of fabrics of the warp type. Warp knits are characterized by the yarns, or threads, being formed into stitches in a lengthwise direction. Warp knitted net made from high density polyethylene, polypropylene, or nylon is supple and drapes easily in place. Such knitted netting does not have any shape memory, so it hangs all the way down to the ground protecting the vine or other fruit-bearing plant, and in many applications does not need to be secured, unlike extruded net. Further, knitted net is soft to the touch and does not have sharp corners or edges to cut the hands of workers, so workers do not need gloves to protect their hands. Most single or double row knitted net can be installed and retrieved with an inexpensive non-hydraulic applicator.

The same warp knitting machine can produce net from 1 foot to 100 feet wide. Warp knitted net is made with a wide variation in thread "denier" to create heavier or lighter weight nets. Further, warp knitted net has a rip-stop property, in that small tears caused by vineyard posts or other means do not propagate through the material.

Knotted and multi-filament knotless forms of net are highly effective alternatives to knitted and extruded net. Generally, these are used in permanent installations to create bird exclosures. A disadvantage of knotted and knotless nets is their high cost.

As currently manufactured, raschel knitted diamond or hexagonal mesh net is stretchy, or more precisely it is not dimensionally stable in either the length or width direction. For example, when such a net is pulled lengthwise, that is extended, the meshes- in the net will deform and become long and narrow resulting in a narrowing or retraction of the potential width of the net. When the net is pulled tight, in the longitudinal direction, with no widthwise tension, the meshes will essentially be closed; this defines the rope length of the net. The rope length can refer to the entire length of the net, for example 150 meters, or can refer to a unit length by reference to mesh opening density, for example 48 aligned openings per meter. Each of such nets have a "design" size where the individual openings defined by the meshing have the optimal size, which would normally be at or about the maximum opening area. The design size would have a design length, which can be stated as the entire length of the net, for example 100 meters and a design width, for example 5 meters, which would normally be at or about the labeled length and width assigned to the net by the manufacturer and put on the net packaging. The design length may also be stated in a unit length by reference to mesh opening density, for example, 32 aligned openings per meter. Referring to FIG. 2A, there can be seen a partial view of a prior art knitted net in a slack position with the meshes at approximately their optimal size relating to the design length, design width, and design size of such a net. FIG 2C illustrates an exemplary view of a net laid flat illustrating a "design" size. FIG. 2B and 2D illustrate a prior art net under tension in a lengthwise direction E such that the border rope is pulled taught and thus linear, the meshes are not of optimal size and may be extended to their maximum length. As can be seen in FIGS. 2A and 2B, when the net is subjected to tension in the direction of arrow E, for example lengthwise tension, a dimension B, the width of the "square" or meshes is reduced to a dimension D. Further, a dimension A, the length of the meshes, is increased to a dimension C when under tension in the direction of arrow E. The dimensions of the individual meshes of course correspond to the length and width of the net when the meshing positioning is uniform. In such prior art netting there is no easy indicator as to the proper lengthwise tension or stretch to apply to the netting. The easiest stretch length is the taut "rope" length of the border bundle of meshes which results in a net stretched lengthwise more than the optimal "design" length, width, and size.

When this type of net is installed, as the net is laid down over the canopy of trees or bushes, i.e. blueberries, vines or other crops, i.e. strawberries, the meshing immediately becomes engaged with the leaves and branches effectively preventing any longitudinal or lateral adjustment of the positioning of the net on the canopy. Thus, the net has to be close to its "design" size as it is deployed. Deployment in the design size is dependent primarily upon the tension the net is under primarily in its longitudinal direction, but also in its widthwise direction as it is being deployed. Moreover, the balance or differences between these forces directly impact the dimensions of the net as it is deployed. The balance or differences between these forces may vary dramatically along the length of the net such that the net is excessively wide along certain portions of the row of crops and excessively narrow along other portions as is illustrated in FIG. 2E.

This lack of dimensional stability makes it very difficult to simultaneously deploy or apply a knitted net in its design size, that is, both the correct length and correct width dimensions that would typically be marked on the label of the net. Workers installing the net attempt to apply the correct tension in the lengthwise and widthwise directions in order to achieve proper coverage of the net. Some nets include colored indicator lengthwise stripes to assist in installation. When the net is properly installed, the stripes will be a . predetermined distance apart. However, this can be a slow and cumbersome process, particularly to repeatedly monitor the spacing to properly install the net.

The problems associated with installing current nets are most acute when the installation process places either excess or insufficient tension in the warp direction, that is, the lengthwise, direction. When over-stretched lengthwise, the net cannot be stretched widthwise to the dimension as marked on the label. The net will be too long in the lengthwise direction, and too narrow in the widthwise direction. Conversely, if workers under-compensate and place too little tension on the net in the lengthwise direction, the net will be too short in the lengthwise direction, and too wide in the widthwise direction relative to the design size. As a result, nets would need to be sized larger than what is actually needed for the installation, to compensate for the less than optimal installation of the net. This can mean unnecessary higher costs for the nets.

With regard to packaging of warp knitted nets, they are conventionally knitted at rope length and they are then heat treated under tension to tighten the crocheted loops and make them more uniform. Heat treating also stiffens the net to some degree. After heat treating the nets are wound on spools at or near rope length. As a result the net acquires some memory. In the absence of tension the 'default' configuration of the meshes is oblong and nearly closed. When stretched in the widthwise direction the meshes will not remain stretched but will tend to return to an oblong shape, although not as elongated as before stretching.

Standard packaging of warp knitted netting consists of pulling the netting off of the pull, with the net fully taut at rope length, and then placing the rope net in a wooden frame using a back-and-forth method ("radiator fold"). The net is then bound with ropes, and placed in a bag with the folds of the net situated at the top and bottom of the bag, and the roped net running up and down between the folds. This combination of events and practices has several effects when applying the nets under field conditions:

1) The tightly packed radiator fold method prevents the net from flowing smoothly out of the bag at a pace with the forward motion of the tractor. Instead there is considerable friction preventing the netting from flowing out of the bag, thus creating tension in the lengthwise direction. 2) The method of radiator folding tightly roped net creates twists in the net. Too many twists can make it more difficult for workers to stretch the nets to the proper width, and therefore contribute to lengthwise tension.

3) The method of heat treating the nets and then spooling them under tension creates a memory that makes it difficult to stretch the nets to their full width.

With regard to the installation of netting, standard masts for suspending the net over the crop plants during installation have several eyelets (similar to a fishing rod) through which the netting must travel. Often these eyelets get progressively smaller toward the top of the mast, by which time the net has assumed rope shape and length. These eyelets also increase friction and tension on the nets.

Standard applicator masts have a small ring or bent tube at the tip placed over the row. After traveling through the small ring the net is allowing to fall on the vineyard row as workers pull the edges to stretch the width. The prior art applicator mast ring's small size creates two problems:

a) Adds additional friction and tension to the nets as it is applied.

b) Causes twists in the net (or concentrates and exacerbates twists that are already in the net as a result of the method of packing), thus making it difficult to stretch the net to its full desired width.

There exists a need then for a net to protect fruit or crops from bird damage that is cost effective or price-competitive, and has ready guidance for optimal installation, that has rip stop construction, and that is supple and easily draped over fruit or crops, and that is easier to apply with the proper or desired dimensions without injury to workers or the fruit itself.

SUMMARY OF THE INVENTION

In a preferred embodiment, a raschel knitted diamond or hexagonal mesh net is manufactured with dimensional control means for limiting lengthwise stretch when dispensed and laid in place. Said means provides a design size of the netting as well as a design length and design width. The design size appropriately is an optimal size and is appropriately identified on the packaging of the net. The desired length is fixed during or after knitting by inclusion of a relatively non-stretchable elongate portion extending lengthwise in the net and preferably fixed at lengthwise intervals or continuously to the meshing. The portion may be a separate member such as a strip of polymer or fabric, a rope cord, twine or other flexible but relatively non-stretchable material that may be interwoven through the meshing or fixed on one side of the meshing and preferably fixed to the meshing at intervals by tying or other attachment means. Such a portion is appropriately termed a tension control portion or tension control line and is preferably installed at the time of manufacture of the netting. Alternatively, a strip of relatively non- stretchable meshing extending lengthwise can be provided by shrinking a strip of existing meshes present in the meshing in such a way that when those shrunken meshes are pulled to rope length or close to rope length of the non shrunken portions of the meshing, the net will be at a design length resulting in the width being at or about the design width.

With the tension control portion installed, placing the correct tension and correct lengthwise stretch on the net during installation is achieved by simply pulling the net longitudinally, preferably at the tension control portion, fixed with the desired length in the lengthwise direction, until the tension control portion is taut. This structure of the net provides feedback to workers, ensuring the correct tension and correct lengthwise stretch; therefore the net is not over stretched lengthwise. Because of the readily ascertainable correct lengthwise stretch, it is easy for workers to install the net with the design size, including the correct width. Although it is contemplated that the tension control portions are most advantageous running lengthwise down the meshing, such portions could alternatively or additionally ran widthwise or diagonally providing dimensional control. Moreover, there may be a plurality of tension control portions extending lengthwise and/or widthwise.

hi particular embodiments, a strip of thin plastic sheeting or film may be utilized with a width sufficient to provide additional features such as rain and hail deflection and shade.

A further aspect of the invention is the packaging subsequent to knitting. In a preferred embodiment, this comprises the steps, although is some cases less than all of the steps may be used: 1) After heat treating the nets are stretched to their full desired width in order to reduce or weaken the memory.

2) The nets are then gathered loosely in a pleated or gusset folded fashion, rather than stretched taut to rope length and shape.

3) The net is then packed in the bag by simply lowering it into the bag in a loose zigzag pattern with the net running horizontally and the folds at the sides of the bag.

4) The bag is then compressed to optimize space on the shipping container, and then is bound around the outside. There are preferably no ropes or bands binding the net within the bag.

These modifications to the production and packaging methods serve to decrease lengthwise tension on the nets and make it easier for workers to stretch the nets to their full desired width.

The invention also encompasses several changes to the tractor-mounted applicator, designed to minimize lengthwise tension on the net and facilitate installation with the intended dimensions.

A wider bag mouth and corresponding ring frame on the applicator is preferred. The mouth of the bag is drawn up through the ring, is opened fully and turned down over the outside of the ring, and then is secured by means of a drawstring threaded through a channel sewn into the mouth of the bag. The wider bag opening allows for the freer flow of the net out of the bag with less friction and tension. In certain applications, the net may be wound on a spool and dispensed from and/or retrieved by the spool.

A wider mast ring with a concave lower side to expand the net and position it over the sides of the grapevine canopy, reduces twisting, reduces friction and tension, and makes it easier for the net to be stretched to its full intended width.

The present invention includes methods of manufacturing a knitted net having dimensional stability, methods of packing nets, and methods of installation of a net having dimensional stability. It is an advantage of the present invention that the net will retain its manufactured dimensions when installed. It is a further advantage of the present invention that the net may be installed faster, due to the net retaining the correct dimensions when being pulled and secured into place.

A still further advantage of the present invention is that less material is needed to create a net that covers the same area than is currently possible. Because the net retains its dimensions when installed, the net no longer must be manufactured larger than needed to compensate for stretching and distortion that used to frequently occur during installation.

BRIEF DESCRPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of the present invention being installed on fruit-bearing plants.

FIG. 2A is a view of a prior art net.

FIG. 2B is a view of a prior art net.

FIG. 2C is a plan view of a prior art net laid out flat at a "design" size, length, and width.

FIG. 2D is a plan view of the prior art net of FIG. 2C stretched lengthwise beyond the design length.

FIG. 2E is a plan view of the prior art net of FIGS. 2C and 2D that illustrates a deficiency of prior art nets in that different portions along the length may have different widths.

FIG. 3A is a perspective view of a net depicted in a slack position according to the present invention.

FIG. 3B is a perspective view of a properly tensioned net according to the present invention.

FIG. 3C is a view of the net of FIG. 3B with the border meshes that have been bound together pulled to their rope length. FIG. 3D is a close-up view of a net according to one embodiment of the present invention.

FIG. 4 is an overhead view of one embodiment of the present invention installed on fruit-bearing plants.

FIG. 5 is an end view of one embodiment of the present invention installed on fruit-bearing plants.

FIG. 6 is a flow chart depicting a method of manufacturing a net according to one embodiment of the present invention.

FIG. 7 is a flow chart depicting a method of manufacturing a net according to a further embodiment of the present invention.

FIG. 8 is a flow chart depicting a method of manufacturing a net according to a still further embodiment of the present invention.

FIG. 9 is a block diagram of manufacturing a net according to one embodiment of the present invention.

FIG. 10 is a block diagram of manufacturing a net according to a further embodiment of the present invention.

FIG. 11 is a perspective view of a net according to one embodiment of the present invention, prior to being heat treated.

FIG. 12 is a perspective view of a net according to one embodiment of the present invention, subsequent to being heat treated.

FIG. 13A is a view of a net with a tension control line therein.

FIG. 13B is a view of a net with a tension control line therein.

FIG. 13C is pictorial view of a knitting machine producing a stream of meshing with a tension control line therein in accord with the invention. FIG. 14 is a close up view of the net of FIG. 13 A.

FIG. 15 is a plan view of a net with a different embodiment of a tension control line therein.

FIG. 16 is an elevational view of a net of FIG. 15.

FIG. 17 is a plan view of a net with a plastic film providing the tension control.

FIG. 18 is a plan view of a thin film on a net.

FIG. 19 is a schematic illustration of how the net with film of FIGS. 17 and 18 could be manufactured.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. IA and IB, a net 10 according to one embodiment of the present invention has can be seen in FIG. 1, being installed on, fruit-bearing plants. A vehicle such as a tractor may be useful during the installation of the net 10. As the net 10 is draped over fruit-bearing plants, one or more workers may position the net 10 on the plants to ensure proper coverage of the plants. The net may preferably be dispensed from a bag 10.2 or other container where the net is loosely, packed. The net generally comprises generally meshing 11 and a tension control portion 11.2 which may be a line or strip of material separate or part of the meshing. The tension control portion may be manually or otherwise kept taut to facilitate correct dimensional control of the net during placement. Application of netting may be generally as disclosed in U.S. Patent No. 5,956,923 which is incorporated by reference herein.

When used herein, "rope length" and "design length" of meshing or nets or net portions can, depending on context, either indicate the actual total length of the net, meshing, or net portion, or may indicate a unit length which is appropriately stated as mesh opening per unit of measure. The design length of a net may be "100 meters" and also "32 aligned mesh openings per meter". For such a design length a Raschel knitted net could have a rope length of 150 meters and 48 aligned mesh openings per meter. Moreover netting may be in a rope length configuration which means the meshing, net, or net portion, is pulled taut lengthwise with no widthwise tension thus maximizing the mesh openings length. Similarly a design length configuration means the openings are at a selected opening sized and a design density per unit measure or area measure.

Referring to FIGS. 3A-D, 4 and 5, there can be seen a partial view of a net 10 according to one embodiment of the present invention. In this embodiment of the invention, the desired length of the net, the design length, is fixed after the knitting process by shrinking areas of the net, preferably lengthwise strips. The areas can be individual warp rows of meshes; multiple warp rows of meshes, also called bands of meshes; or portions of multiple warp rows, also called panels of meshes. This shrinking process has the effect of creating shrunk areas of the net, and un-shrunk areas. The shrunk areas feature physically smaller meshes than meshes in those areas that are not shrunk. Because the dimensions of meshes in the shrunk areas are physically smaller, those meshes will reach their rope length under tension much sooner than meshes in the un-shrunk areas. This has the effect of fixing the length of the net at the rope length of the meshes in the shrunk areas. The shrinking is sized such that when the shrunk meshes are pulled to rope length or close to rope length, the un-shrunk portions will be at their design shape and size, typically the length as marked on the packaging label and the width will be as marked when the net is stretched widthwise. The strip of meshes shrunk can be bound together to create a rope-like portion. Alternatively, rows of meshes can be bound together with the bound clump then shrunk.

The net 10 comprises a pair of lengthwise edges 12, an inner portion or body 14, and a plurality of meshes 18. Meshes 18 are ideally roughly diamond or hexagonal shaped. The figures generally represent only a small portion of the typical size of the nets. Such nets extend several hundred and several thousand feet in length and can be a few feet wide to 40 or 50 feet or wider.

FIG. 3B depicts net 10 stretched, such as by tension, in the direction of arrow F, the lengthwise direction to near or the optimal design size, including design length and width. The shrunk border portion is at or near its rope length. FIG. 3 C depicts such a net with the border shrunk meshes bound and pulled to their rope length.

In one embodiment of the present invention, one or more shrunk areas 20 are created by applying a targeted heat to the area desired to be shrunk, following a first heat treatment of the entire net 10. In such an embodiment, net 10 is comprised solely of a first monofilament yarn 16. In one embodiment of net 10 as seen in FIG. 3C, meshes 18 are comprised of a plurality of loops 19. Yarn 16 is knitted into loops 19 during the knitting process. An advantageous material for first monofilament yarn 16 may be high density polyethylene, although other materials may be recognizable to one skilled in the art.

In an alternative embodiment of net 10, one or more shrunk areas 20 are created by applying a targeted heat to the area desired to be shrunk, however net 10 is not subjected to a first heat treatment. Net 10 is comprised solely of a first monofilament yarn 16 in such an embodiment. An advantageous material for first monofilament yarn 16 may be high density polyethylene, although other materials may be recognizable to one skilled in the art.

In a further contemplated embodiment of net 10, wherein net 10 comprises a first monofilament yarn 16 and a second monofilament yarn 17, un-shrunk areas 22 are comprised of meshes 18 knitted from first monofilament yarn 16, while shrunk areas 20 are comprised of meshes 18 knitted from second monofilament yarn 17. Second monofilament yarn 17 has a greater susceptibility to shrinking at a temperature lower than first monofilament 16. An advantageous material for second monofilament yarn 17 may be polypropylene, although other materials may be recognizable to one skilled in the art. After subjecting net 10 to a heat treatment, meshes 18 in shrunk areas 20 are dimensionally smaller than meshes 18 found in un-shrunk areas 22. In one embodiment of the present invention, body 14 is mostly comprised of un-shrunk areas 22.

In a still further contemplated embodiment of the present invention, net 10 is comprised of a first monofilament yarn 16 and a second monofilament yarn 17. First yarn

16 and second yarn 17 are comprised of the same material, however first yarn 16 is subjected to a heat treatment prior to being knitted, while second yarn 17 is not subjected to a first heat treatment. Areas not desired to be shrunk are comprised of meshes 18 knitted from first yarn 16, while those areas desired to be shrunk are comprised of meshes 18 knitted from second yarn 17. Meshes 18 comprised of first yarn 16 and meshes 18 comprised of second yarn 17 have substantially identical dimensions immediately following the knitting process, however net 10 is then subjected to a heat treatment. During the heat treatment, meshes 18 comprised of first yarn 16 do not significantly decrease in size, creating un-shrunk areas 22, while meshes 18 comprised of second yarn

17 will decrease in size, creating shrunk areas 20. As can be seen in FIG. 3B, when net 10 is installed and pulled in the lengthwise direction of arrow F, the meshes 18 in shrunk areas 20 approach their rope length, at which point the meshes 18 will have a closed appearance. Net 10 is manufactured in such a way so that when meshes 18 in shrunk area 20 are closed, meshes 18 in un-shrunk areas 22 are slack and not under tension in the lengthwise or widthwise direction.

Referring now to FIGS. 11 and 12, a portion of net 10 is depicted, having meshes 18 and regions G and H. In FIG. 11, net 10 is depicted prior to any heat treatment. Regions G are those areas of net 10 that will not be shrunk during heat treatment, while region H will be shrunk during heat treatment. In FIG. 12, net 10 is depicted after being subjected to heat treatment. Meshes 18 in region H have been shrunk as compared to meshes 18 in region G. In an example embodiment, meshes in region H are shrunk approximately 30% compared to region G. The length K of one side of a mesh 18 in region G may be about 0.71 inches, while the length L of one side of a mesh 18 in region H may be about 0.50 inches. The ratio of K to L is 0.71/0.5, or about 1.4. In order to achieve such a ratio, meshes 18 in region H must be shrunk about 30%: (0.71-0.5)/).71 = 30%. During installation of net 10, region H is pulled to its rope length. The rope length of meshes 18 in region H is approximately equal to the diagonal length of meshes 18 in region G, as represented by length J in FIG. 12. In this example embodiment, length J is about 1.0 inch. The overall length of net 10 is limited to the length of the smallest meshes 18^ in this case those meshes 18 in region H. Therefore, meshes 18 in region G cannot be pulled lengthwise substantially beyond length J.

Region H need not be in the middle of net 10, as depicted in FIGS. 11 and 12. In an alternative embodiment, it may be desirable to locate regions H at the edges 12 of net 10. Edge 12 may comprise more than one row of meshes 18 bundled together to provide additional strength to net 10. Meshes 18 in region H at edge 12 are shrunk such that their rope length is approximately equal to the diagonal length of meshes 18 in the remainder of net 10.

Referring now to FIGS. 4 and 5, net 10 is depicted installed over a row of fruit- bearing plants. In this embodiment, net 10 features shrunk areas 20 at each of the edges 12, and a shrunk area 20 in the middle of the body 14. Referring now to FIG. 6, a method 100 of manufacturing net according to one embodiment of the invention is shown. A first step 110 in method 100 is to extrude a plurality of monofilament yarns, the yarns being constructed from the same material. A second step 120 comprises knitting a raschel knit net from the plurality of yarns. The as- knitted dimensions of the net may need to be increased to accommodate for shrinkage of the net during heat treatment. In a third step 130, the net is subjected to a heat treatment. During third step 130, the net is flat and pulled to rope length, wherein rope length is the length of the net when pulled lengthwise so as to stretch and close the meshes into a rope- like appearance. In the case of yarns constructed from high density polyethylene, an appropriate temperature for the heat treatment of third step 130 will be approximately one hundred five degrees Celsius. During third step 130, the entire net is subjected to the heat treatment. A fourth step 140 subjects only certain portions of the net to an additional heat treatment at a higher temperature. During fourth step 140, the net is not stretched to rope length, rather it is kept to a pre-determined amount of slack. Concentrated heat is applied to the areas desired to be shrunk. The amount of heat and amount of slack present in the net will determine the amount of shrinkage that occurs in the areas being subjected to the second heat treatment of fourth step 140.

Referring now to FIG. 7, a method 200 of manufacturing net according to a further embodiment of the present invention is shown. A first step 210 in method 200 is to extrude a plurality of monofilament yarns. An appropriate material to be extruded during first step 210 is high density polyethylene, although other materials may be used with success. A second step 220 comprises extruding a plurality of monofilament yarns made from a resin having a lower melting point than the yarns created in first step 210. A third step 230 in method 200 comprises knitting a net from the yarns created in first step 210 and second step 220. Yarns constructed from second step 220 are to be used in areas where the meshes are desired to be shrunk. Yarns constructed from first step 210 are to be used in all other areas to create non-shrunk meshes. The as-knitted dimensions of the net may need to be increased to accommodate for shrinkage of the net during heat treatment. A fourth step 240 comprises a first heat treatment for the net. The net is pulled to rope length, closing the meshes of the net, and the net is then subjected to a first heat treatment. The temperature of the heat treatment of fourth step 240 does not significantly alter the size of the meshes of the net. A fifth step 250 subjects the net to a second heat treatment at a temperature higher than the temperature of the first heat treatment, the temperature of the second heat treatment being close to the melting point of the yams created in second step 220. The second heat treatment of fifth step 250 causes meshes in the net comprised of yarns created in second step 220 to shrink up more than meshes in the net comprised of yarns created in first step 210. During fifth step 250, the net is kept at a pre-determined amount of slack, and heat is applied to the entire net.

Referring now to FIG. 8, a method 300 of manufacturing a net according to one embodiment of the present invention is shown. A first step 310 comprises extruding a plurality of monofilament yarns from the same material. An appropriate material may be high density polyethylene, however other materials recognizable to one skilled in the art may be used with success. Ih a second step 320, some of the yarns created in first step 310 are subjected to a heat treatment, wherein the heat treatment pre-shrinks the yams. During a third step 330, yams shrunk during second step 320 are knitted with yams created in first step 310. Yams from second step 320 are used to knit the body, or un-shrunk areas of the net, while yams from first step 310 are used to create areas that will be shrunk during a fourth step 340. In fourth step 340, the entire net is subjected to a heat treatment. The net is kept slack during the heat treatment. Areas of the net knitted from yams constructed in second step 320 will not shrink, or will not shrink significantly, as those yams were pre- shrunk during second step 320. However, meshes in those areas of the net knitted from yams constructed in first step 310 will shrink, reducing their dimensions, as the yams have not yet been subjected to any heat treatment.

Referring now to FIG. 9, a block diagram of the manufacturing equipment for making a net according to one embodiment of the present invention is shown. Material is fed into an extruder 410, and then passed to a knitter 420. After knitting, the net is drawn through a first heat treating apparatus 430 that heats the entire net. Finally, the net is fed through a second, targeted heat treating apparatus 440 that applies targeted heat to specific locations of the net. In an alternative embodiment, the net is not passed through heat treating apparatus 430, rather the net is fed directly from the knitter 420 to the targeted heat treater 440.

Referring now to FIG. 10, a block diagram of the manufacturing equipment for making a net according to a further embodiment of the present invention is shown. A first material is fed into an extruder 450, and a second material is fed into extruder 455. A knitter 460 then knits the two materials together. The entire net is then passed into a first heat treat apparatus 470, and finally into a second heat treat apparatus 480.

As described above, one embodiment of the present invention therefore includes a raschel knitted diamond or hexagonal mesh net that is manufactured with the length fixed to approximately equal the length as designed for by way of shrinking a portion of said net, and also includes methods of manufacturing such a net as well as a method of installing such a net.

Further embodiments of a preferred horticultural net with dimensional control are illustrated in FIGS. 13A, 13B, 14, 15, 16, and 17, with each embodiment including a relatively non-stretchable portion 500 appropriately termed a tension control line extending lengthwise on the meshing or net portion 510. Each of these figures represent a small portion of the typical size of the nets. Such nets extend several hundred and several thousand feet in length and can be a few feet wide to 40 or 50 feet or wider. FIGS. 13 A, 13B, and 14 illustrate a line which can comprise a rope, or a string, or a wire, or a cord that extends lengthwise substantially the length of the mesh net. The line can be made of various materials with the characteristic that the line does not stretch lengthwise compared to the mesh netting. The line may be interwoven through the meshes in a sinusoidal fashion as is illustrated in FIG. 14, or may be machine knitted into the meshing as illustrated in FIG. 13B and 13C and may be fixed to the mesh at intervals such as by tying the line onto the mesh at fixation points configured as knots 520. In the ideal situation the closer the attachment points to one another, the better, it is believed, that the invention will function; although it is believed the invention will suitably function with the spacing between fixation points of the line and mesh net to be 30 feet or more. Ideally the fixation points will be spaced 18 inches to 8 feet. Ideally where the line is intermeshed it will cross to the opposite side of the mesh at least every few inches, for example every approximately 5 inches, or 8 inches, or 12 inches, or 20 inches or less.

Referring to FIG. 13 C, a preferred method of accomplishing the invention is illustrated wherein a tension control line 500 is knitted into the meshing by the knitting machine 528. Conventional Raschel knitting machines will discharge the meshing in a stream 529 wherein the meshing is at substantially rope length, for example 48 aligned mesh openings per meter, with the individual opening substantially closed and oriented in the direction of the meshing stream discharge illustrated by the arrow 531. In this first portion 532 of the stream the tension control line is longer than is needed and corresponds substantially to the rope length of the meshing. At the second portion 533 of the stream, a portion of the tension control line, and a corresponding portion of the meshing are configured and attached such that the tension control line now maintains the netting at its design length. FIG. 13B illustrates the retraction of the meshing with respect to the tension control line such that the openings are substantially at their maximum and the width is at the design width and the length is as the design length, for example 32 aligned mesh openings per meter.

This may be accomplished by taking a segment of the meshing with a length Ll, for example 2.8 meters, with is in its rope length configuration, compressing or retracting the particular length on or with respect to the tension control line a percentage that equates to the segment design length L2, for example to 2.0 meters, and tying the tension control line with the control line taut at said design length L2 to both ends of the segment of meshing. Note that the right end of the segment will typically already be tied due to the downstream segments 535 already having been tied at the design length L2. The excess length of the tension control line after tying the line, is preferably removed and discarded.

The stream of meshing with the tension control line installed may then be further treated or can be packaged such as in a bag 536 or wound on a spool 537.

Referring to FIGS. 15 and 16, the relatively non-stretchable portion extending lengthwise on the mesh netting may be a flexible strip such as a fabric or a polymer sheet that is secured to the net. The strip may be transparent or opaque. For example the strip could comprise two strip portions 540, 542 on each side as illustrated in FIG. 16 that are secured together capturing the mesh therebetween and fixing the position of the strip with regard to the mesh essentially the length of the net and strip. In other embodiments, the strip could be interwoven through individual meshes and attached, that is fixed to the net at intervals as described above with respect to the line. The strip may be attached to the mesh by adhesive, for example adhesive on each of the adjoined faces of the strip portions 540, 542. The strip can be attached by sewing, the welding, by mechanical fasteners, i.e. staples, rivets, clips or by other means. The strip is preferably about an inch wide or wider. In a preferred embodiment a single tension control line runs down the middle of the net although in other embodiments more that one tension control line may be utilized for example along the edges of the net. The ultimate purpose of the tension control line is to limit the maximum length of the net as deployed and thereby prevent the lengthwise tension that would otherwise impede the full and proper opening of the net laterally.

The tension control line may be inserted into the meshes during knitting or after knitting. It is inserted or woven looping through the mesh in a substantially linear fashion. The tension control line preferably is not knitted and it is not part of the net fabric.

The tension control line may be inserted when the net is at rope length. The rope length of these types of nets are about 30% longer than the desired deployed length for the desired width. This factor will vary as a function of the mesh geometry (e.g. hex, diamond or other), knitting slack, etc. To be specific there is slack in the tension control line from weaving up and down through the meshes, slack sideways from light tension and finally any stretchiness of the tension control line material,

After the net is knitted and the tension control line inserted with the net at or near rope length, the tension control line must be shortened to the desired "as deployed" net length. Some factors that may affect how much the tension control line must be shortened include:

1) tension control line stretch under installation and removal forces;

2) tension control line slack from sinusoidal weaving of the tension control line up, over and through the mesh;

3) The tension control line does not need to go through each mesh. If inserted by hand a loop might preferably be 3 to 6 feet long. If done by machine during knitting, every lengthwise mesh in a could have the tension control line interwoven

4) Material stretch;

5) Knot tightening;

6) Temperature and humidity may impact the stretchiness of the net; and 7) Stretching and heat treatments during manufacture.

Experience indicates that the tension control line needs to be approximately 25% to 35% less in length^" than the rope length of the net. In a preferred embodiment the factory takes the newly manufactured net, still at rope length, and draws it across an area with a fixed length of say 25 meters. Then a length of the tension control line equal to the amount of length reduction required to achieve an optimally sized net in the field is identified. For example, 5 meters may be cut from the 20 meter tension control line positioned in a 20 meter section of rope length net. The tension control line ends are preferably knotted and secured to the mesh. This allows the mesh to float on the tension control line between knots that are say 15 meters apart. The mesh cannot move beyond the knot. This prevents excess bunching. This process is repeated until the entire net has been shortened.

The dimensions and geometry of the net can be controlled during manufacture or subsequent to manufacture by manipulation of the tension control line that has not been fixed at intervals or continuously to the net.

For example a warp knitted net with desired installation dimensions of 5m x 1000m and a mesh size of 20mm per side. In that each mesh can assume the shape of a square or a rhombus - and therefore have a variable area in terms of square mm occupied - the desired dimensions of 5m x 1000m can be achieved in different ways.

By inserting an un-knitted yarn or twine during the knitting process and then shortening that twine by a specified ratio, the dimensions of the net and the shape of the meshes can be manipulated and controlled in order to achieve specific performance requirements.

For a given weight of warp knitted netting optimal square meter coverage is achieved when the meshes are square in shape. This requires equal tension in both the lengthwise and widthwise directions. When the meshes are square in shape the sides of the meshes — the strands of the net — are oriented at 45 degree angles to the edges of the net.

When square the area of each mesh is 20mm x 20mm = 400 square mm. When frilly stretched the length of each mesh is 20mm + 20mm = 40mm.

When square the diagonal distance from corner to corner of each mesh is

28.28mm.

C

Therefore, to achieve the desired dimensions of 5m x 1000m, the net will be 177 meshes wide (177 MD or meshes of depth) based on 5,000mm divided by 28.28mm per mesh, and the net will be 35,361 meshes long (35,361 ML or meshes of length), based on 1,000,000mm divided by 28.28mm per mesh.

The rope length of this net is therefore 35,361ML x 40mm per fully stretched mesh = 1,414m.

The ratio of the rope length to the installed length is approximately 1.4 to 1. With the invention this can be achieved by inserted a straight (un-looped, un-knitted) yarn or twine during the raschel knitting process, and then shortening the inserted yarn or twine by 8 meters for every 28 meters of length.

The total number of meshes required to achieve the desired dimensions of 5m x 1000m is 177 x 35,361 = 6,258,897 meshes. This is the lowest number of meshes possible to cover the 5,000 square meter area of the net, and therefore requires the smallest quantity of raw materials and processing.

However, there are times when it is desirable for the net to be designed in such a way that the meshes are not square and are instead rhombic in shape when the net is installed to the desired dimensions. Reasons for doing so include manufacturing considerations, applications considerations, manipulating the percentage of shade cast by the net, or altering the effective opening size to block certain birds or other pests.

For example, a ratio of 1.25 to 1 means that the rope length of the net is 1,250m. Based on this the ML can be calculated as 1,250,000mm divided by 40mm = 31,250 ML.

The installed lengthwise diagonal measurement of each mesh can be calculated as 1,000,000mm divided by 31,250 meshes = 32mm. The installed widthwise diagonal measurement of each mesh can be calculated by solving the equation x² + 16^{2 =} 20² and then multiplying x by 2. In this case the installed widthwise diagonal is 24mm.

Based on a widthwise diagonal of 24mm the MD can be calculated as 5,000mm divided by 24mm = 208 MD.

The area of each mesh is ¹A (diagonal 1 x diagonal 2) = 384 square mm, which is less than the 400 square mm area of the same mesh in a square configuration.

The number of meshes required to achieve the desired 5m x 1000m dimensions can be calculated as 208 x 31,250 = 6,500,000, which is more than the 6,258,897 needed if all of the meshes are square in shape.

3.85% more meshes - and therefore more netting is required to cover the same number of square meters.

Therefore this net would cast 3.85% more shade than the net of the same dimensions made with a rope length to installed length ratio of 1.4:1 - and perhaps more shade than that depending on the angle of incidence of the sun at a given time of day. For certain crops this might be desirable as a means of reducing heat stress and sun exposure.

Reducing the rope length to installed length ratio from 1.4:1 to 1.25:1 also reduces the widthwise diagonal length of the meshes from 28.28 to 24mm. This reduction in the effective opening size of the meshes protects crops from smaller pests with less raw material and processing costs than a net with 17mm per side meshes and mesh diagonal lengths of 24mm when installed at 1.4:1.

The problem with conventional warp knitted nets is that there is no reliable way to control the lengthwise tension during installation to ensure that the nets will be installed with the desired ratio.

For example, a 1.25:1 ratio net with 20mm per mesh side and 208 MD x 31,250 ML can be installed with too much tension and stretch in the lengthwise direction, so that the installed length is 1,100m. At a length of 1,100m the lengthwise diagonal measurement of each mesh becomes 35.2mm.

Based on a lengthwise diagonal of 35.2mm the widthwise diagonal measurement becomes 19mm.

The installed width of the net can therefore be calculated to be 208 MD x 19mm - 3.95m - far less than the desired 5m width.

The invention, by fixing the length at a rope length to installed length ratio of 1.25:1 thus ensures that the desired dimensions will be achieved consistently and accurately in the field. The invention gives the manufacturer the ability to control the geometry and mesh configuration in order to optimize a range of performance parameters.

In preferred embodiments the meshes for the horticultural nets described herein have openings with sides that range from 8mm to 36mm, which with a diamond shape equates to a rope length of 16mm to 72mm for a mesh opening. More preferably the sides are 15mm to 23mm in length. The actual length of nets used herein, particularly as packaged, are preferably at least 100 meters long and 3 meters wide design length. More preferably the nets are more than 900 meters in design length. At design size, the nets preferably have a length to width ratio of at least 10 to 1 and more preferably at least 30 to 1. The preferred embodiments are raschel knitted nets but knotted and other styles of nets may also fall within the scope of the invention where the net, meshing or net portion has diamond or hexagonal aligned openings, a rope length that is 10 per cent more than a selected design length. More preferably the rope length is at least 15 per cent greater than the design length. Even more preferably the rope length is greater than 20 percent of the design length.

Additionally, it is desirable to pre-stretch the net widthwise preferably after knitting and before packaging. Also for packaging the net may be folded without pulling it into a rope. It is put into bag pre-stretched widthwise by gusset folding. The net is preferably packed in a zigzag pattern such that the net emerges from the bag with substantially less resistance than in the past. Referring to FIG. 17, a wider strip is illustrated. This strip may be a transparent film strip attached to the mesh in similar fashions as the strip of FIGS. 15 and 16 described above. In preferred embodiments this plastic may be several feet or more wide. This strip may be sufficiently wide so as to perform further functions such as rain shield, or moisture barrier, or may be tinted to limit sunlight. FIGS. 18 and 19 illustrate a means for attaching such a wider strip utilizing heat sealable film or film strips.

The present invention may be embodied in other specific forms without departing from the central attributes thereof, therefore, the illustrated embodiments should be considered in all respects as illustrative and not restrictive.

Claims

WHAT IS CLAIMED:

1. A knitted net with dimensional control for protecting crops as substantially shown and described herein.

2. A net with a tension control line for protecting crops as substantially shown and described herein.

3. A method of providing a protective net with dimensional control tension control line as substantially shown and described herein.

4. A method of providing a protective net with a tension control line as substantially shown and described herein.

5. A method of manufacturing a net for protecting crops as shown and described herein.

6. A method of packing a net for protecting crops as shown and described herein.

7. A method of installing a protective net onto fruit bearing plants, as substantially shown and described herein.

8. A horticultural net for providing protection of crops, the net comprising a net portion and a tension control line, the net portion having a length and a width, the net portion extendable from a design length to a rope length, the tension control line extending the length of the net and attached to the net at a plurality of locations along the length of the control line thereby limiting the length of the net to substantially the design length of the net.

9. The horticultural net for providing protection of crops of claim 8, wherein the length of the tension control line is substantially the same as the design length of the net portion.

10. The horticultural net for providing protection of crops of any of claims 8 or 9, and wherein the tension control line is selected from the set comprising: rope, twine, polymer strip, polymer cord, and a fabric strip.

11. The horticultural net for providing protection of crops of any of claims 8 through 10, wherein the tension control line is interwoven through the openings of the mesh of the net portion.

12. The horticultural net for providing protection of crops of any of claim 8 through 11, wherein the net portion has a first end and a second end and wherein the tension control line is tied to the net at the first end and at the second end and periodically tied to the net at intervals therebetween.

13. The horticultural net for providing protection of crops of any of claims 8 through 12, wherein the net portion has a first end and a second end and wherein the tension control line is tied to the net at the first end and at the second end and continually attached to the net therebetween.

14. The horticultural net for providing protection of crops of any of claim 8 through 14, wherein the tension control line is a strip of sheet material at least 1 inch in width that extends the length of the net portion and that is attached by at least one of sewing, adhesives, mechanical fasteners, welding, and tying.

15. The horticultural net for providing protection of crops of claim 14 wherein the tension control line is a plurality of feet in width.

16. The horticultural net of any of claims 8 through 15 wherein the net is raschel knitted net with diamond or hexagonal openings.

17. The horticultural net of any of claim 8 through 15 wherein the design length of the net is 20 to 53% less than the rope length.

18. A net for providing protection of crops, the net comprising a raschel knitted net portion and a tension control line, the net having a length and a width, the net flexible and stretchable lengthwise and widthwise and having a rope length when stretched lengthwise and not stretched widthwise, the net comprising meshing with a multiplicity of individual openings, with each opening defining an area that changes with the flexing and stretching of the net, the net having a design length and a design width wherein when the net is opened to said design length and design width the multiplicity of openings are each substantially at a maximum area; the tension control line having a length and being substantially less stretchable than the net, the tension control line extending the length of the net and attached to the net at a plurality of locations along the length of the control line thereby limiting the length of the net to substantially the design length of the net.

19. A method of protecting a row of crops comprising the steps of:

providing an elongate horticultural net in a bundled configuration for protecting crops, said elongate knitted net comprising meshing and a tension control line, the tension control line running longitudinally down the length of the meshing,

anchoring one end of the net at a fixed point at an end of the row of crops to be protected; and

transporting the bundled net on a vehicle traveling adjacent the row of crops;

dispensing the net over the row of crops while the vehicle is moving whilst generally keeping the tension control line under tension thereby providing dimensional control of the net as it is being dispensed.

20. The method of claim 19 wherein the horticultural net comprises the net of any of claims 8 through 18.

21. The method of claim 19 wherein the meshing has a first end, a second end and having a rope length, the method further comprising the step of utilizing a tension control line that is shorter than the rope length of the meshing,

22. The method of claim 15 wherein the net is supported above the row of crops as it is being dispensed by a closed loop.

23. A method of providing a dimensionally controlled horticultural net, the net comprising a rectangular portion of meshing having a length and a width, the meshing defining a multiplicity of openings, the openings rhombic or hexagonal in shape and aligned with the ends and sides such that the meshing has a lengthwise rope length with the rhombic or hexagonal openings being geometrically collapsed into a maximum length and the meshing having a selected design length that is less that the rope length, wherein at said design length, when the meshing is laid flat, the rhombic or hexagonal openings are geometrically open, the method comprising the steps of:

installing a tension control line the length of the rectangular portion of meshing;

affixing the tension control line to at least periodic lengthwise attachment points on the meshing, the at least periodic attachment points correlating to the design length of the meshing.

24 The method of claim 23 further comprising the step of attaching the tension control line continuously to the length of the meshing.

25. The method of claim 23 further comprising the step of packing the horticultural net in a bag, the bag having a bottom and an open top, the step further comprising layering the net in a back and forth arrangement stacking layers from a bottom of the bag to the top of the bag.

26. The method of any of claims 20 to 25 further comprising the steps of packing the net in a bag and dispensing the net over a row of crops from a vehicle moving adjacent to the row.

27. The method of claim 23 further comprising the steps of selecting the tension control line from one of the following: cord, twine, rope, strip of polymer film, and a strip of fabric.

28. A method of providing a dimensionally controlled net comprising the steps of:

utilizing a knitting machine to raschel knit a stream of netting, said netting having a rope length,

utilizing the knitting machine to knit a centrally located tension control line into the stream of netting,

fixing the tension control line to the stream of netting periodically at attachment points defining segments between the attachment points such that that the tension control line precludes the meshing from stretching to the rope length.

29. A dimensionally controlled net, the net comprising meshing and a tension control line, the net having a pair of opposite ends, a pair of opposite sides, a design length and design width with a length to width ration of at least 10 to 1, the net further having a rope length at least 15 percent longer that the design length, the tension control line extending the length of the net and attached periodically to the meshing thereby preventing the net from longitudinally stretching to the rope length, thereby stabilizing the dimensions of the net.