AU2005202732A1 - Artificial bombora for shaping waves - Google Patents

Description

PATENTS ACT 1990 ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Invention title ARTIFICIAL BOMBORA FOR SHAPING WAVES The following statement is a full description of this invention, including the best method of performing known to me.

This invention relates to underwater structures. More particularly, although not exclusively it discloses an improved artificial reef or bombora.

To achieve optimum performance in surf sports it is necessary to have waves of both adequate size and suitable shape.

Ideally the waves should have a smooth consistent contour and break evenly and progressively along their length either from one side or outwardly in both directions from a central "take off" position.

To create such waves a specific type of offshore seabed contour is required outside the natural shallow water beach zone. From observations of natural reef formations it is considered by some experts including the inventor that an offshore reef area having a upward leading edge slope of about 1/6 to 1/20 forms the best surfing waves. Such naturally occuring formations however are relatively rare and often occur at inconvenient or inaccessible locations. While it is known to construct underwater structures for coastal erosion control and/or surf sports these typically comprise crudely shaped piles of rocks or sandbags piled near the shore and within the naturally occuring surf zone. Their shape is imprecise and they are subject to erosion to the extent that ongoing maintenance is required. Moreover once installed they cannot be moved to another location It is therefore an object of this invention to ameliorate the afoementioned disadvantages and accordingly a sea swell modifying structure is disclosed for location at an underwater site. said structure when at a position of use displaying in plan view at least one rearwardly angled side edge with an upwardly sloped surface extending back from said side edge whereby said sea swell when encountering the structure is modified to form a surf wave which breaks progressively along said upwardly sloped surface and said structure being further adapted for buoyant and non-buoyant configuration to facilitate flotation to and subsequent submersion at said underwater site.

The said structure when in a position of use has a predetermined, constant evenly, smoothly contoured upper surface set in relation to sea level. The relatively large flat reef crest area produces a laminar flow over the reef of relatively constant depth which minimises any tendency of the waves "sucking dry" on the reef as they break Preferably the structure comprises a towable floatable hull which upon filling with water through built-in sea valves can be submerged at a preselected offshore location.

It is further preferred that said structure is adapted for removable installation at said underwater site.

It is further preferred that said structure includes height adjustable supports for aligning the position of the upper surface thereof relative to the sea level.

It is further preferred that said structure is adapted to be re-floated after submersion for positioning at another location.

It is further preferred that the sides and upper surface of said structure are modifiable to take on a range of shapes according to site requirements and/or design preference.

Currently preferred embodiments of the invention will now be described with reference to the attached drawings in which:figure 1 is a schematic perspective view from the front of a first embodiment of an artificial reef or bombora constructed according to this concept, figures 2, 3, 4 and 5 are plan, rear elevation, front elevation and side elevations views of the bombora of figure 1, figures 6 to 10 are schematic front perspective, side elevation, plan, front elevation and rear elevation views of a second embodiment of an artifical bombora according to this invention, figures 11 and 12 are schematic front and plan views of a third embodiment of the invention, figures 13 and 14 are plan and side elevation views of the bombora of figures 11 and 12 in a position of use, and figures 15 to 19 are plan and side elevation views of a fourth embodiment of the invention.

Referring first to figures 1 and 2 there is an artificial reef or bombora which in plan view has a generally triangular form with V-shaped leading edges 1. With this embodiment the edges angle back from a squared off nose section 2 at about degrees as shown at A. The top surface 3 of the bombora slopes upwardly from said leading edges preferably to a Vshaped planar area 4 toward the rear. Preferably but not essentially this slope is of the order of about 1/6 to 1/20.

It is envisaged that such configuration if submerged at an appropriate depth would mimic the wave shaping effect of those naturally occuring offshore reefs or bomboras which are known to produce the best surfing waves. In particular, the swells would initially form a peak on the nose portion 2 to provide a central "take off" zone and then subsequently break progressively out to each side along the sloped surfaces 3.

There are support legs or feet 5 as best shown in figures 3 to 5 which support the bombora at a selected height and orientation above the seabed 6. Preferably these supports are adjustable by hydraulic means or the like (not shown) whereby the top surface of the bombora is maintained at an optimum depth below the water surface 7 for wave shaping and to account for tides and swell size changes.

A self-illuminating safety marker 8 is also provided to alert boats to the presence of the bombora and/or support a surfcam antenna, water level marker and take off position marker.

It is also proposed, in accordance with this invention, that the bombora would comprise a watertight hull formed by a interior steel support frame and exterior skin using known standard methods for constructing marine structures/vessels.

The structure would be adapted to be floated under tow or self-power to a chosen offshore location at which point it would be weighted down with sand and/or onboard valves would be opened to flood the hull whereby it submerges in a controlled decent to the seabed on the aforementioned legs.

Preferably means would also be provided within the structure to subsequently expel ballast from the hull so that it can be raised again for maintenance or re-location.

With the second, third and fourth embodiments of the invention shown in figures 6 to 10, 7 to 14 and 15 to 19 respectively the main components which correspond in function to those of figures 1 to 5 are identified by the same numbers which however are primed and to distinguish them.

In the case of the second embodiment the nose portion 2' is more rounded and merges smoothly into the adjacent sloping side surfaces 3' to reduce turbulance for a more even wave break. The overall ratio of height/length for the bombora is also increased as best shown in figure 7. It is considered at this time that the structure would operate best when the upper planar area 4' is submerged about .5 to 1 metre below the water surface 7' In this case of the third embodiment the nose section is rounded in a similar manner to the second embodiment, the angles B, C of the swept back edges preferably reduce from about 65 degrees adjacent the nose portion to about 42 degrees toward the rear and the planar crest area is also enlarged. As shown in figure 13 an incoming wave 9 would initially form a peak and break over the nose portion to produce a central take-off zone. The swell would then progressively peak and break outwardly toward each side to produce a consistant properly shaped surfing wave 10 along each side of the central crest area From trials conducted by the inventor it is believed that the structural refinements of this embodiment may produce one or more of the following improvements in wave shape.

a shoaling wave shoulder adjacent the break point of each wave to enable surfers to take-off at any point along the breaking wave during its course along the edge of the reef, a more predictable wave formation and break, and constant wave peel angles in the surfable ranges along the full length of the reef edges.

The reef structure with this embodiment may have a width D of about 120 metres and a length E of about 95 metres. It may -7vary in height above the seabed from about 2 metres at the nose to about 5 metres at the rear. As shown in figure 14 it is intended for deployment in about 6 to 8 metres of water on open sand bottom beach areas approximately 300-400 metres out from the beach 10A. With incident wave heights of about 1-3 metres and an approximate 7-10 second wave period it is shaped to produce high quality surfing waves breaking both left and right from the take-off area or "Peak". A moderate to fast ride of about 75 metres in length in both directions would be obtained.

With the fourth "dynamic" embodiment as shown in figures to 19 the upper portion of the bombora also sits on a fixed base 11 which may be -4 metres AHD but is adapted to swivel either left or right of the centre-line 12 about a pivot point 13 at the centre of the nose. This would alignthe structure with incident ocean waves which can vary in approach direction. With this embodiment variations in incident wave angles of up to about 20 degrees from the centre-line 12 can be allowed for by the aforementioned degree mechanical swivel (see angles F, G) plus an inherent allowance of 10 degrees variation built in to the design shape of the bombora surface itself. Other amounts of mechanical swivel may be designed into the structure within the scope of this invention.

As a further novel feature of this "dynamic" embodiment the planar crest area is also adjustable in height (see arrow H) between normal and raised crest levels 13A and 13B.

The forward edges of this area may comprise a series of hinged or sliding plates 14 and the rear may be fitted with overlapping panels 15 whereby said area may be adjusted vertically with respect to the base 11 to follow tidal variations in water levels and/or wave height.

Preferably, although not essentially, the aforementioned swivel and height adjustment would include hydraulic mechanisms remotely operable from the shore. It is further envisaged that the bombora could be continuously tuned for optimum wave shaping by the use of sensors to monitor real time sea conditions and an automatic adjustment means of any suitable design (preferably with manual override).

It is believed that this particular "dynamic" version of the artificial bombora would allow rotation of the wave shaping upper panels relative to the main structure. They can thereby be aligned with incoming swells from a range of different directions.

For safety reasons it is further preferred that portions of the upper surface of the bombora which a user may contact be covered with an impact absorbing material. Non limiting examples of such material are silicon rubber or silicon foam as sold by Wacker Chemicals under the trade name "Elastosil" It is considered that such material of suitable texture and thickness would render a user's impact on the bombora -9structure equal to or less than an impact on a natural sandy beach bottom.

It will thus be appreciated that this invention at least in the form of the embodiments disclosed provides a novel and improved artificial bombora for shaping offshore sea swells into surf waves. Clearly however the structures described are only the currently preferred forms of the invention and a wide variety of modifications may be made. For example the slope and configuration of the edge portions may be changed to mimic the shape of certain naturally occuring bomboras and cavities or textures may be formed in non-critical areas of the structure for the encouragement of marine fauna. Also, while steel is currently preferred for constructing the reef structure the invention extends to the use of any other suitable material.

Claims (11)

1. A sea swell modifying structure for location at an underwater site, said structure at a position of use displaying in plan view at least one rearwardly angled side edge with an upwardly sloped surface extending back from said side edge whereby said sea swell when encountering the structure is modified to form a surf wave which breaks progressively along said upwardly sloped surface and said structure being further adapted for buoyant and non-buoyant configuration to facilitate flotation to and subsequent submersion at said underwater site.

2. The structure as claimed in claim 1 and having at said position of use an ability to maintain a predetermined upper surface in relation to sea level so that said structure produces said surf wave as the sea swell passes thereover.

3. The structure as claimed in claim 2 wherein said structure has in plan view a generally triangular form with two V-shaped side edges and upwardly sloped surfaces which extend from said side edges to a planar crest area toward the rear.

4. The structure as claimed in claim 3 and including a frontal nose portion from which said V-shaped side edges extend rearward whereby said swell initially forms a peak on said nose portion to provide a central take off zone for -11- surfers.

The structure as claimed in claim 4 wherein said structure sits on a fixed base and is adapted to swivel to each side of a centre-line position to align with a range of incoming directions for said swell.

6. The structure as claimed in claim 5 wherein said structure swivels about a pivot point located at the centre of said nose portion.

7. The structure as claimed in claim 6 wherein said planar crest area is adjustable over a range of heights to suit different water levels and wave conditions.

8. The structure as claimed in claim 7 wherein front edges of said planar crest area include hinged or sliding plates to maintain an unbroken structural surface over said range of heights.

9. The structure as claimed in claim 8 wherein said planar area is adjustable over a range of heights by means of hydraulic mechanisms remotely operable from the shore.

The structure as claimed in claim 9 wherein said structure includes a watertight hull formed by an interior steel support frame .and exterior skin. -12-

11. A sea swell modifying structure for location at an underwater site, said structure being substantially as described herein with reference to figures 1 to 5, 6 to 11 to 14 or 15 to 19. Dated this Z day of 17/m/- 2005 Stephen Raymond Barrett By His Patent Attorney MICHAEL ANDERSON-TAYLOR -13-