[ 1 ] A collector for rainwater comprising : a plurality of floating booms connected together by end joints to form an articulated boom ring; constraining means whereby said boom ring is constrained to form a predetermined polygonal shape; a catchment bag made from flexible waterproof membrane attached to said boom ring so as to form an open basin contained by said boom ring and separated from the surrounding body of water; whereby atmospheric precipitation may fall into said catchment bag and be collected.
 The collector for rainwater of Claim 1 wherein said booms are rigid and elongated and said end joints include flexible joint means selected from the group comprising of universal joints, swivel joints, hinges, chained links, wires and ropes whereby said booms are enabled to pitch and roll without transmitting substantial bending and torsional stresses to adjacent booms.
 The collector for rainwater of Claim 1 wherein said constraining means include means selected from the group comprising of tension ties, wires, ropes, tubes, bars, poles, boards, fabric and netting attached across the far ends of every two adjacent said booms.
 The collector for rainwater of Claim 3, further including said constraining means attached across the far ends of every three adjacent said booms.
 The collector for rainwater of Claim 1 wherein said constraining means include a plurality of anchors positioned on the sea bottom and connected to said booms with ropes and chains.
 The collector for rainwater of Claim 1, constituting a module of said predetermined polygonal shape, whereby a plurality of said modules are joined together to constitute a catchment network.
 The collector for rainwater of Claim 6 wherein said polygonal shape is selected from a group that includes hexagons, rectangles and triangles.
 The collector for rainwater of Claim 1, further including covering means to reduce losses of collected fresh water from evaporation and from water spray generated by wind and waves.
 The collector for rainwater of Claim 8 wherein said covering means include buoyant materials of density less than fresh water, said
covering means incorporating draining means, including perforations, which allow weather precipitation to drain through.
 The collector for rainwater of Claim 1 wherein said booms are flexible and elongated and said end joints include flexible joint means selected from the group comprising of universal joints, swivel joints, hinges, chained links, wires and ropes which enable said booms to pitch and roll without transmitting substantial bending and torsional stresses to adjacent booms and said constraining means include a plurality of anchors positioned on the sea bottom and connected to said booms with ropes and chains.
 The collector for rainwater of Claim 10, constituting a module of said polygonal shape, whereby a plurality of said modules are joined together modularly to constitute a catchment network.
 The collector for rainwater of Claim 11 wherein said polygonal shape is selected from a group that includes hexagons, rectangles and triangles.
 The collector for rainwater of Claim 10, further including covering means to reduce losses of collected fresh water from evaporation and from water spray generated by wind and waves.
 The collector for rainwater of Claim 13 wherein said covering means include buoyant materials of density less than fresh water, said buoyant materials incorporating draining means, including perforations, which allow weather precipitation to drain through.
 This invention relates to the collection, storage and distribution of rainwater and other forms of fresh water precipitation falling over the seas.
 The collection of rainwater has always been a necessity in many parts of the world where water is scarce, but this art has primarily been a land-based activity involving the use of land areas either as catchment sites or as foundations to support catchment structures such as basins, rooftops, gutters, tarmacs and fog collecting nets.
 The areas of seas where abundant rainwater falls is vast, and is of the order of billions of hectares. When rainwater falls into the sea, it is no longer fresh water. Unless rainwater falling over the seas is collected before it mixes with seawater, fresh water is lost.
 Rainwater in the open seas has never been collected to any significant degree.
Conceivably, floating marine structures such as ships and barges could collect water by utilizing their deck areas to contain precipitation out at sea. However, these areas are extremely small compared with the areas of seas over which rainwater falls. Moreover, the costs of construction of such deck areas and their supporting hull structures would be unfeasibly high especially if such a method were to be used for the purpose of collecting precipitation. Disclosure of Invention
 Relatively inexpensive floating vessels, similar in principle to inflatable dinghies, have been proposed for the collection or storage of rainwater in sheltered bodies of water such as lakes and coastal bays. To develop on this principle for use in the open seas, the problem of stability has to be solved. Essential to this solution is the size factor of the floating vessels. It is a known principle in naval architecture that an increase in the principal dimensions of a floating vessel, notably the width, generally increases the metacentric height of the vessel for greater hydrostatic stability. Furthermore, dynamic stability against the forces of wind and waves is increased when such floating vessels are flexibly rafted together. Even then, under sufficiently severe storm conditions, such rafted vessels could flip over and stack against one another much like the way a folding map stacks together, unless the individual size of the rafted vessels is large enough to withstand the capsizing moment of the severest of
projected storms in the area. However, when floating vessels increase in size, structural stress increases due to the increased bending moments when encountering longer waves and the increased dynamic forces from motion, such as rolling, pitching and heaving, acting on these longer structures. A very large inflatable dinghy would bend and kink in much the same way as an elongated toy balloon would kink when the ends are pulled towards each other. Using stronger materials for the vessel's structures may be a solution, but that would increase costs, and depending on the size of the vessel and the materials used, these costs could approach that of a conventional vessel's hull.
 A suitable invention needs to be not only economically feasible, but also needs to be scalable, to enable large-scale coverage while withstanding the forces of wind, waves and currents at sea. Additionally, the invention has to be able to substantially prevent contamination due to seawater spray generated during stormy conditions.
 U.S. Patent 3,230,967 to Castro (1966) discloses a rigid tank open at its top and with its bottom supported by a sea borne float and connected to storage bellows. It requires the use of sumps and pumps to transfer collected water into the bellows. From stability and cost considerations, it does not allow for large-scale coverage.
 U.S. Patent 3,730,120 to Dobell (1973) discloses an apparatus for collecting rainwater using a floating collar which supports a deck for rainwater to fall onto and drain via a non-return valve into a collecting vessel below. The floating collar incorporates a wave barrier surrounding each collecting vessel, which is connectable to other collecting vessels using grommets. As these floating collars are single units without articulating means, if they are connected to form a large-scale catchment area at sea, the enormous forces of wind, waves and current in storm conditions would cause the collectors to fold over and stack, as explained above, especially if the floating collars are not large relative to the heights of waves. On the other hand, if the collars were to be made relatively large, but when subjected to stresses from heavy seas and long-wave bending moments, use of large floating collars without articulating means would require the collars to be built from high strength materials such as steel, as for a modern ship's hull, instead of plastics as proposed. Furthermore, the pockets of sea surfaces exposed at the periphery of each collector will allow seawater spray to be generated by wind and waves resulting in contamination of collected rainwater. This renders the apparatus impractical and uneconomical for large-scale use in the open seas.
 U.S. Patent 4,092,827 to Schneider (1977) discloses an apparatus for capturing rainwater at elevated aerial locations above the seas. It requires the use of lighter- than-air balloons, aerial funnels and ducts. Since wind speeds generally tend to be high during times of precipitation, wind forces combined with the weight of the apparatus and the weight of an appreciable quantity of fresh water will require the use of many
large balloons. These will in turn generate yet greater wind loads. Even if suitably strong and light materials were available, the cost of the apparatus would be uneconomical compared to alternative means of fresh water collection on land or production through desalination processes presently available.
 U.S. Patent 5,010,837 to Hirose (1991) discloses a floating raceway consisting of a floating bank portion and a raceway portion, all made with flexible film material, with the intention of storing and transporting water. While the function of collecting rainwater is not claimed by Hirose, the lack of stiffness in the structure will not enable the apparatus to maintain the opening in the floating bank portion to collect rainwater as well as maintain the necessary volume in the raceway portion to contain the water. Under the action of wind and forces of the sea, the flexible floating banks would collapse together and cause the collected water to be squeezed out and over the floating banks.
 WIPO Patent Application International Publication Number WO 02/40125 A2 issued to Glozman (23 May 2002) discloses a water collection device essentially similar to Dobell's but without the collecting deck and the non-return valve. It also uses a single piece buoyant support fastened to an impermeable membrane collector sheet into which rainwater falls. A flexible material covers over the collected water under normal conditions to prevent evaporation and is individually rolled back with a roller for rainfall collection. It is rolled up or unrolled as necessary with the action and function similar to that of a cover for a small swimming pool. A baffle is used to form a shielding wall around a limited group of floating collectors so as to prevent waves washing over and depositing seawater onto the collector sheet. The floating collector is towed to a pump station to transfer the collected water for storage. As in Dobell's collar stated above, the buoyant support is a single piece frame without articulating means thereby causing it to fail for the same reasons if used on a large scale in stormy seas. Together with the individually operated cover rollers and the baffles, the design renders the apparatus impractical and uneconomical for large-scale use in the open seas.
 All the above designs do not envisage coverage of substantial areas of the open seas. They would fail to collect rainwater at sea on a practicable large-scale and are economically uncompetitive with present day alternatives of fresh water production such as desalination of seawater.
 The object of the present invention is to provide a method of rainwater collection at sea which is technically feasible and economically competitive with present day alternatives of fresh water production. It provides for floating booms connected together with flexible joints into a stable and seaworthy ring, which hold in place a flexible
waterproof catchment bag. Tension ties constrain the shape of the ring to ensure the mouth of the bag stays open for rainwater to fall into and allows the collected rainwater to be contained within the bag for storage and subsequent delivery. The articulated floating boom ring and catchment bag form a modular catchment unit, which is flexibly rafted together with other units to form larger catchment networks for increased stability and coverage. The size of individual catchment networks covering several hundred hectares of sea surface is envisaged. The design and installation of the system allows for the adoption of mass-production processes.
 Accordingly, the objects and advantages of the invention are:
 to provide a catchment module consisting of a ring of floating booms connected by articulating means to form a polygonal shaped boom ring from which suspends a catchment bag consisting of a flexible waterproof membrane for catching and storing rainwater and other forms of weather precipitation;
 to provide a plurality of such modules which can be flexibly rafted together in a modular fashion to form large scale catchment networks to cover large areas of the seas;
 the modules may be anchored to the sea bottom at as many points as necessary to prevent drift due to wind, current and waves and to maintain the shape of the modules;
 floating pump stations may be joined to the catchment network to deliver the collected rainwater via flexible piping into tankers or pipe delivery systems;
 the use of flexible joints to connect adjacent floating booms together allows large networks to be built yet reducing the problem of stresses due to bending and torsional forces, and motion caused by sea waves on elongated floating structures;
 the use of tension ties as constraining means for individual catchment modules enables the modules to maintain their desired shape;
 the use of flexible waterproof membranes for the catchment bags allows the collected rainwater to be completely buoyant in the sea without generating excessive load stresses in the membranes or floating booms;
 the use of flexible waterproof membranes for the catchment bags allows sea waves to be transmitted through the catchment network without generating excessive dynamic stresses in the membranes or floating booms;
 the large scale catchment network using modular units assembled tightly together minimizes exposed sea surfaces within the catchment network thereby reducing contamination especially to the inner modular units due to seawater spray caused by wind and waves;
 the use of articulating means to connect floating booms together allows for the construction of sufficiently large boom rings able to withstand capsizing moments in
stormy seas and yet able to withstand bending stresses due to long- wave bending moments;  the use of articulating floating booms avoids situations inherent in single-piece buoyant supports where one portion of the buoyant support is thrust downwards whilst the corresponding opposite portion is thrust upwards during stormy seas, a motion known as pitching, resulting in the uprising portion attempting to lift the load of collected water thereby causing damage to the buoyant support or membrane;  the modular nature of the catchment network allows all parts to be mass-produced to achieve economies of scale;  the modular nature of the catchment network allows any damaged module to be isolated without contaminating the collected water contained in the rest of the modules;  the modular nature of the catchment network allows any damaged module to be easily replaced;  the simplicity of the invention as designed allows for the use of a floating factory vessel to rapidly lay and connect the catchment network modularly onto the sea surface till the required coverage is achieved;  compared with desalination processes for fresh water production, collection of 'sea rain' by this means is economically competitive and uses no energy in the large-scale production of fresh water and therefore does not contribute to global warming.  Further objects and advantages will become apparent from a consideration of the ensuing description and drawings.
Description of Drawings
 Fig 1 shows a hexagonal catchment module. (Plan View)
 Fig 2 shows a vertical cross-section of the catchment module.
 Fig 3 shows flexible end joints and tension ties connecting the ends of booms. (Side
Elevation)  Fig 4 shows a catchment network consisting of several modules connected by rafting ties. (Plan View)
 Fig 5 is an expanded view showing a junction of the catchment network.
 Fig 6 shows the catchment module equipped with a perforated cover.
 Reference Numerals In Drawings:-
 10 Catchment Module
 12 Boom
 14 End Joint
 16 Tension Tie
 18 Catchment Bag
 20 Wood Log Core
 22 Rubber Tube
 24 Polymeric Foam
 26 D-Shackle
 28 Ringbolt
 30 Rafting Tie
 32 Suction Pipe
 34 Cover
 36 Perforation
 40 Sea
 42 Rainwater
 Fig 1 shows a plan view of the preferred embodiment of a catchment module 10.
Although the module has a hexagonal shape, other shapes such as triangles, rectangles and circles are possible. Module 10 consists of six buoyant struts or booms 12 connected at their ends to adjacent booms 12 by flexible end joints 14 to form an articulated boom ring. The boom ring, floating in the sea 40, is constrained to maintain the hexagonal shape by tension ties 16 connected across the far ends of every two adjacent booms 12. Anchors, not shown in drawings, may be used at as many points as necessary to further constrain the module to maintain its hexagonal shape and to prevent drift due to wind, current and tides.
 Fig 2 is a sectional side view of module 10 with catchment bag 18 suspending downward and attached to booms 12 to contain the collected rainwater 42. Bag 18 may be made of any flexible waterproof membrane or fabric such as polyethylene sheet. Depending on the design load of collected rainwater and sea conditions, a flexible waterproof material of appropriate tear strength may be used. Bag 18 may be shallow, essentially a membrane loosely stretching across the mouth of the boom ring, or it may be deep, if a larger quantity of water is to be collected and stored.
 Booms 12 may be constructed using any flexible or rigid elongated material that is buoyant in seawater including wood logs, rigid foam core tubes, and air-inflated and pressurized tubes. Fig 2 shows a preferred embodiment where boom 12 is of a composite construction consisting of a wood log core 20 within a rubber tube 22 filled with polymeric foam 24.
 Fig 3 is a side view of two adjacent ends of booms 12 connected by flexible end joints 14 which may be any form of flexible joints including universal joints, swivel joints, hinges, chained links and ropes. In the preferred embodiment, flexible joints 14 consist of wire ropes with looped ends. Tension ties 16 may be rods, poles, tubes, ropes or any material capable of sustaining a tension force. In the preferred embodiment, tension ties 16 also consist of wire ropes with looped ends. End joints 14 and tension ties 16 are shown attached to the floating booms through D-shackles 26 to ringbolts 28 attached to wood log core 20.
 Fig 4 shows a plan view of several catchment modules 10 joined together with rafting ties 30. The modules are positioned within a matrix where other modules may be added to form a large floating catchment network. The number of modules joined together may be any number necessary to cover an area of sea where rainfall is to be collected.
 Fig 5 is an expanded plan view showing a junction of the hexagonal matrix where a module is joined to other modules. Rafting ties 30 connect the modules flexibly together. In the preferred embodiment, rafting ties 30 also consist of wire ropes with looped ends connected through D-shackles to ringbolts 28.
 As shown in Fig 2, a flexible suction pipe 32 is installed with one end attached to the center of catchment bag 18. Suction pipe 32 is connected to other suction pipes serving other catchment bags and piped to suction pumps (not shown).
 Fig 6 is a plan view of an alternative embodiment showing an additional installation of a perforated cover 34 across the mouth of catchment module 10 and attached to the boom ring. Cover 34 is made from any material, such as firm, fabric or foam board, that is buoyant in fresh water and has perforations 36 or other means that allow water to drain through.
 Catchment module 10 is deployed individually or in combination with other modules to form a catchment network over an area of the sea where rainfall is sufficiently available for collection. Where necessary to prevent drift due to wind and current, anchors may be installed at as many points as appropriate to hold the modules in place and to assist in maintaining their geometric shapes.
 During rainfall, rainwater falls onto catchment bag 18, which is held afloat and open by the ring of booms 12. The hexagonal shape of the opening in this preferred embodiment is constrained by flexible end joints 14 and by tension ties 16. End joints 14 connect the booms into a ring while tension ties 16 maintain the angular orientation of adjacent booms. Although six tension ties 16 are shown in this embodiment, more may be used as necessary, such as across the far ends of every three adjacent booms, to further constrain the ring of booms 12 to maintain the desired hexagonal shape. End joints 14, being flexible, enable said booms 12 to individually pitch, roll, heave and yaw during storm conditions without transmitting substantial bending and torsional stresses to adjacent booms. This allows for the use of longer booms and, in turn, increases the overall size and stability of the individual modules 10. Other constraining means, such as installing a rigid floating foam board or a fabric or netting with the size and shape of the opening may be used, in place of or in conjunction with tension ties 16, to maintain the hexagonal shape of the opening and to reduce loss of collected water through evaporation.
 As shown in Fig 2, the accumulated rainwater 42, being less dense compared to seawater, floats on the sea surface separated from seawater by the flexible waterproof membrane bag 18. The collected rainwater level (FWL) is shown above the seawater level (SWL). The freeboard of booms 12 contains the height above the sea surface level of the accumulated rainwater within bag 18. For every 1 m design depth of collected rainwater, approximately 25 mm to 30 mm minimum freeboard is required depending on the salinity of the location at sea.
 For further increased stability and for increased coverage, several catchment modules 10 may be flexibly rafted together as shown in Fig 4. In the preferred embodiment, rafting ties 30 consisting of flexible joints connect adjacent modules and substantially enable the modules to roll and pitch independently. This reduces the stress load transferred between modules and allows for larger modules to be used.
 Perforated cover 34, as shown in Fig 6, reduces losses of collected rainwater through evaporation and through spray generated by wind and waves. Perforations 36 allow rainwater to drain into the collection space below the cover. An additional function of cover 34, if it is made from high strength or reinforced material, is to maintain the shape of the opening of the module.
 Although means for transferring collected rainwater to delivery systems is not claimed, Fig 1 shows suction tube 32 which suck the collected rainwater by means of suction pumps when sufficient rainwater has accumulated. The collected water may be pumped to tanker vessels moored nearby or via pipe delivery systems for use or processing onshore (not shown). In large catchment networks, contamination due to seawater spray will be very much reduced in inner catchment modules compared to the outer modules at the periphery of the network because the inner modules are protected by the outer modules. This fact allows for the advantageous selection of modules in the transfer of collected water to delivery systems and, if necessary, for the discard of collected water in the peripheral modules.
Mode for Invention
 Heretofore, rainwater falling at sea has largely not been collected. Seas cover four- fifths of the earth's surface. Although not all areas of the seas have abundant rainfall, many areas of seas especially in the equatorial latitudes and in coastal regions have sufficient rainfall to justify its collection. The demand for fresh water in many parts of the world has outstripped supply. Shortages of water caused by population growth, over-pumping of aquifers, pollution of riparian basins, climate change and global warming, and the increasing tendency of some jurisdictions to sequester sources of diminishing water supply previously shared with others have resulted in many areas of the world suffering from water crises.
 This invention of a collector for rainwater falling at sea is presented to solve many
of the problems faced by others when contemplating the means to salvage 'sea rain'. Even if they had wondered about the use of an inexpensive and vast plastic sheeting laid onto the sea surface, problems such as tearing of the sheeting, spilling of the collected rainwater into the sea, contamination by seawater spilling onto the sheet, and the drifting of the sheet away from the designated area are not easily solved.
 Accordingly, this invention using catchment modules presents a technically feasible and economical solution to these and other problems. The module may be used singly, such as for the fresh water requirement of a fish farm at sea, or in combination with other modules to form large networks to collect the world's 'sea rain', which would otherwise be lost.
 The rainwater catchment modules floating at sea or in lakes may also be used in conjunction with many other purposes including the following:
 as fresh water reservoirs;
 as ponds for fish and aquatic life;
 as ponds for marshy plants;
 as ponds for migratory birds to rest and feed; and
 as floating platforms to support plant and equipment such as solar energy conversion cells.
 Thus the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.
Next Patent: WO/2007/042865