GB2288962A

GB2288962A - Beach net

Info

Publication number: GB2288962A
Application number: GB9411114A
Authority: GB
Inventors: Harold Kvam
Original assignee: MARITIME MECHANIC Ltd
Current assignee: MARITIME MECHANIC Ltd
Priority date: 1994-06-03
Filing date: 1994-06-03
Publication date: 1995-11-08
Anticipated expiration: 2014-06-03
Also published as: GB9411114D0; GB2288962B

Abstract

A beach net located in the sea adjacent a beach provides a safe enclosure of water for swimmers and the like acting as an effective barrier against visiting sharks, but also to prevent drifting debris from sullying the beach and the enclosed sea. The beach net comprises a continuous cylindrical buoyancy element 2, forming a rectangle with the shore, principle anchorage means 1 for the buoyancy element, a net 4 pendently supported from the buoyancy element, and secondary anchorage means 6 tethering the net at its lower edge to the sea bed. <IMAGE>

Description

BEACH NET This invention relates to a net structure for protection of a beach to provide a safe area for water activities. It is widely recognised that off the coasts of some countries and islands, there is the omnipresent threat to swimmers of sharks. The anxiety caused by this danger reduces the enjoyment of people swimming, or participating in other water activities, in the sea off such a beach.

Therefore, it is one object of the present invention to provide a robust and secure net structure boundary juxtapositioned with a beach, which inhibits the entry of sharks, thereby providing within the boundary a safe environment for water activities.

The use of a net to protect a beach has been proposed previously.

However, prior designs have not been totally satisfactory in combining reliability and strength with ease and economy in installation and manufacture.

It is one object of the present invention to provide an improved beach net which overcomes these disadvantages.

Accordingly, the present invention consists in one aspect in a net structure for the protection of beaches or the like, comprising an elongate, buoyancy element capable of withstanding substantial axial stress, principal anchorage means for tethering the buoyancy element to the sea bed, a net pendently supported from the buoyancy element and secondary anchorage means for tethering the net, at a lower edge thereof, to the sea bed.

Advantageously, the elongate buoyancy element comprises a pipe, preferably containing closed cell foam and suitably of high density polyethylene.

It is another object of embodiments of the present invention to provide a net structure which provides a floating support for tired swimmers who have overestimated their capacity.

It is a further object of embodiments of the present invention to provide a net structure that allows sea vessels to pass over it without damage to the vessel, or net structure.

It is yet another object of embodiments of the present invention to provide a net structure that collects drifting rubbish and debris, thereby preventing the debris from sullying the safe water activities area.

The invention will now be described by way of example, with reference to the accompanying drawings, in which: Figure 1 is a pictorial view of a net structure in accordance with the present invention.

Figure 2 shows a cut-away view of an elongate buoyancy means.

Figure 3 shows a beach landing floater of the present invention.

Figure 4 is a cross-sectional view of the net structure according to Figure 1.

Figure 5 is a side cross-sectional view of the net structure complementary to Figure 4.

Figure 6 shows an intersection between net sections.

Figure 7 illustrates anchorage means of the net structure.

Referring to Figure 1, a net structure generally comprises a cylindrical buoyancy element 2 (extending in this arrangement around three sides of a rectangle), principal anchorage means 1 for the buoyancy element 2, a net 4 pendently supported from the buoyancy element 2, and secondary anchorage means 6 tethering the net at its lower edge to the sea bed.

In the preferred embodiment the cylindrical buoyancy element 2 is constructed from a plurality of circular cross sectional high density polyethylene pipes 20, welded longitudinally to form an elongate buoyant pipe 2, shown in Figure 2. The buoyant pipe 2 is filled with closed cell foam 24. The position of the buoyant pipe 2 on the water surface is stabilised, and its perimeter shape defined, by principle anchorage means which consist of a plurality of buoys 3 attached to the buoyant pipe 2 and directly anchored to the sea bed by means of cables 11 extending between the buoys 3 and concrete anchor blocks 1. In the beach landing area spheroidal polystyrene floaters 9 (shown in Figure 1 and in greater detail in Figure 3) are roped together to form a chain between the end of the buoyant pipe 2 and the beach.

Turning to Figures 4 and 5, the net 4 comprises a plurality of net sections interconnected at a plurality of vertical junctions 14. The net 4 suspends in a vertical plane, pendently supported at its upper edge by a nylon rope 7 helically coiled around the buoyant pipe 2. At its lower edge the net is secured to second anchorage means 6. The interconnection of the net sections at the vertical junctions 14 is provided by means of steel hooks 16, affixed to the edges of the net sections, and looping around vertical high density polyethylene pipes 15; these are held in position by a nylon rope 17 threaded through the vertical pipe 15 and extending between the buoyant pipe 2 and second anchorage means 6. The net mesh is fabricated from thick plastics thread, interwoven into a small mesh size with a maximum opening of 45mm. The net is impregnated with an antifouling agent that checks organic growth which would detrimentally affect the weight, volume and buoyancy of the structure. The antifouling agent also discourages the growth of barnacles, which could easily harm swimmers who might accidentally grab or kick the net. The net is able to withstand high intensity ultra-violet light and even typhoons, with the option of being reversed once the upper portion has become weakened. The depth of the net is designed to be at least the water depth at highest high tide plus the maximum wave height. In the beach landing area the net is supported by the chain of polystyrene floaters 9.

A second anchorage means, shown in Figure 7, comprises an elongate stainless steel cable 10 fixed at axial intervals to a plurality of concrete anchor blocks 8. Spring loaded, normally closed, karabiner hooks 13 fasten the lower edge of the net 2 to the steel cable 10 at regular intervals along its length. The steel cable 10 is securely fixed to, and held in tension between the anchor blocks 8 through a clamping connector 18. The concrete anchor blocks 8 are firmly sunk into the sea bed; the height of these blocks vary between 800mm and 1200mm depending on the depth of mud on the sea bed into which the blocks are to be submerged. The concrete blocks are formed onto a pyramidical internal steel frame (not shown) and are treated with plastics to prevent water penetration. A non-buoyant veil 12 is attached to and drapes below the steel cable 10 to ensure that there is no gap between the net 2 and the sea bed, irrespective of variations in the height of the mud on the sea bed.

The robust and continuous construction of the net structure provides a floating barrier around swimmers and the like, offering many benefits.

Primarily, the net structure is an effective physical blockade against visiting sharks, and importantly being highly conspicuous provides a visible barrier between swimmers and visiting sharks. Psychologically, this serves to instil a sense of safety in the swimmer, thus reducing anxiety and creating a relaxed atmosphere. On a more practical level, the buoyant pipe 2 and net 4 together ensure that the protected area is free from debris and rubbish that may have been abandoned further out at sea and that will tend to drift in with the current and tide. The small mesh net size in combination with the rigid support of the net reduces the likelihood of folds occurring in the net, thus reducing the risk of aquatic life, such as dolphins and turtles becoming caught up and entrapped in the net. Also, the buoyant pipe offers floating support for tired swimmers or windsurfers who have overestimated their capacity. Despite the relatively large and rigid nature of the structure the buoyant pipe allows boats to pass over it, simply deflecting beneath the boat, thereby preventing damage to either the boat or the net. Another feature is the arrangement of floating markers 5 around the periphery of the net structure, anchored independently to the sea bed, providing visual forewarning to oncoming boats that they are approaching a swimming area.

In terms of reliability the net structure as a whole requires low maintenance with components having a comparatively long working life.

Claims

1. A net structure for the protection of beaches or the like, comprising an elongate, buoyancy element capable of withstanding substantial axial stress, principal anchorage means for tethering the buoyancy element to the sea bed, a net pendently supported from the buoyancy element and secondary anchorage means for tethering the net, at a lower edge thereof, to the sea bed.

2. A net structure according to Claim 1, wherein said elongate buoyancy element comprises a pipe.

3. A net structure according to Claim 1 or Claim 2, wherein said pipe contains closed cell foam.

4. A net structure according to Claim 2 or Claim 3, wherein said pipe is a plastics pipe of circular cross sectional pipe.

5. A net structure according to any one of Claims 2, 3 and 4, wherein said pipe is formed of high density polyethylene.

6. A net structure according to any one of the preceding claims, wherein said principal anchorage means comprises a plurality of anchorage cables linked at axial intervals to the buoyancy element and secured at respective opposite ends to the sea bed.

7. A net structure according to Claim 6, wherein said each said anchorage cable is linked to the buoyancy element via a buoy.

8. A net structure according to any one of the preceding claims, wherein the elongate buoyancy element is of sufficient rigidity to maintain in use a rectilinear orientation.

9. A net structure according to any one of the preceding claims, wherein said net is formed of plastics.

10. A net structure according to Claim 8, wherein said net is formed of polyimide.

11. A net structure according to any one of the preceding claims, wherein the net is adapted for reversal after a period of use to bring said lower edge into engagement with the buoyancy element.

12. A net structure for the protection of beaches or the like comprising buoyancy means1 a net pendently supported from the buoyancy means and anchorage means for tethering the net at lower edge thereof to the sea bed, said anchorage means comprising an elongate intermediate tethering element held horizontally in tension relative to the sea bed, the lower edge of the net being secured to said tethering element.

13. A net structure according to Claim 12, wherein said tethering element comprises a cable extending between fixed anchorage blocks.

14. A net structure according to Claim 12, wherein an auxiliary net of non-buoyant material is draped from said cable to close any gap between the cable and the sea bed.

15. A net structure according to Claim 14, wherein said net is formed of plastics and said auxiliary net is formed of metal.

16. A net structure according to any one of the preceding claims, wherein said net is held in tension between the buoyancy means and the secondary anchorage means, thereby to reduce the risk of entrapping aquatic life forms.

17. A net structure according to any one of the preceding claims, wherein at least the net is treated with antifouling agent to discourage organic growth.