Abstract:
An apparatus and method for cleaning a boat in the water without pollution. Included are a floating, water-impervious basin and a filtration system. Included are a floating, water-impervious basin and a filtration system. The basin has side walls sloped downwardly to a nadir spanning substantially the full length of the basin, an opening allowing the surrounding water to enter the basin as well as ingress and egress of boats, and a gate movable into a closed position forming a cleaning chamber in the basin. After a boat is in the chamber, the gate is closed to create a pool of water in the chamber isolated from the surrounding water and in which a boat may float while being cleaned. As the gate is closing behind a boat, it allows water to pass therethrough thereby to facilitate closure, and yet is substantially sealed when closed. The filtration system includes a collector pipe lying submerged in the nadir and a pair of return pipes that float on the water in the basin. The sloped side walls and water exiting from the return pipes facilitate movement of materials resulting from the cleaning operation toward the collector pipe. The filtration system sucks the water-borne materials into the collector pipe, pumps them through a filter, and returns clean water to the basin through the return pipes. The relationship of the pipes and the basin facilitates reversibility of the basin so that its exterior surface may be periodically cleaned.

Description:
FIELD 
     The present invention pertains to boat maintenance and more particularly to a method and apparatus for cleaning a boat in the water while avoiding or minimizing pollution. 
     BACKGROUND 
     The necessity of having to clean the hull of a boat periodically has long been known. Marine organisms must be removed for hull preservation and boat efficiency. Hulls may need old paint removed and new paint applied. Decks and other boat parts also need to be cleaned. If the boat is cleaned in the water, these cleaning tasks typically involve brushing both above and below the waterline. Sanding and the use of various cleaning agents and paint strippers may also be used above the waterline. 
     Although such cleaning may be effective to maintain a boat, boat cleaning is also known to result in air and/or water pollution, unless special precautions are taken. Brushing and sanding the hull release contaminants, such as old paint containing lead. If cleaners are used, they are usually toxic. Even if the deck of a boat is washed down with fresh water, polluting materials can be discharged or washed overboard. 
     Voluntary campaigns to control pollution from boat cleaning have been organized, but unfortunately these efforts have not been sufficiently effective. Because of continued concerns about the environment, ever more stringent federal and state laws and programs with tough penalties have been, or are being, enacted or proposed. Under these laws, severe fines and even jail terms have been imposed for those who still pollute the harbor waters as a result of boat cleaning. 
     A well-recognized way of avoiding water pollution is to clean the boat on land, although the problem of air pollution still exists. Moreover, having to haul a boat onto land to perform the cleaning tasks is inconvenient and expensive, especially burdensome for routine maintenance. As a result many boats are still being cleaned in the water notwithstanding the resulting pollution. 
     Apart from applicant, no practical and relatively economical solution to the environmental problems associated with routine boat cleaning is known to exist in the past. Some have tried to minimize the fouling of the boat&#39;s hull by covering it while moored. For example, the U.S. Patent to Faidi U.S. Pat. No. 5,549,069 discloses a bag that is pressed against the hull a shield the hull from the water. However, providing a protective cover for the hull does not directly address the problem of cleaning as described above, which in any event may be required. If chemicals are placed in the bag to dissolve marine growths, the chemicals may escape into the water. On the other hand, the U.S. Patents to Seiple U.S. Pat. No. 3,752,109 and to Feurt U.S. Pat. No. 4,784,078 do disclose floating hull cleaning equipment so that hull cleaning can take place in the water. These are complicated constructions, expensive to build and use, and do not allow routine boat maintenance at a typical dock or slip. Moreover, Seiple has no provision for avoiding pollution, and Feurt, although providing for the evacuation of contaminated water, does not prevent contaminates from escaping through the entrance and exit curtains. 
     To applicant&#39;s knowledge, applicant&#39;s prior U.S. Pat. No. 5,138,963 discloses the only method and apparatus that directly addresses the problem of cleaning a boat hull in the water and at a typical slip while avoiding pollution. Although the concepts disclosed in this earlier patent are still valid, the subject invention provides certain improvements. 
     SUMMARY 
     An apparatus and method are disclosed for cleaning a boat in the water while avoiding or minimizing pollution. Included are a floating, water-impervious basin and a filtration system. The basin has side walls sloped downwardly to a nadir spanning substantially the full length of the basin, an opening allowing the surrounding water to enter the basin as well as ingress and egress of boats, and a gate movable into a closed position over the opening and forming a cleaning chamber in the basin containing a pool of water. After the gate is closed behind a boat, the boat is floating in the pool of water that is now isolated from the surrounding water. As the gate is closing behind a boat, it allows water to pass therethrough to facilitate closure and to control the volume of water in the chamber, and yet is substantially sealed when closed. The filtration system includes a collector pipe lying submerged in the nadir and a pair of return pipes that float on the water in the basin. The sloped side walls and water exiting from the return pipes facilitate movement of materials resulting from the cleaning operation toward the collector pipe. The filtration system sucks the water-borne materials into the collector pipe, pumps them through a filter, and returns clean water to the basin through the return pipes. The relationship of the pipes and the basin facilitates reversibility of the basin so that its exterior surface may be periodically cleaned. 
     An object of the present invention is to clean a boat in the water without causing pollution. 
     Another object is to facilitate routine maintenance of a boat without causing pollution. 
     An additional object is to provide a closed system for cleaning the hull and other parts of a boat while in the water, wherein the substances removed from the boat and the materials used to remove them are collected and filtered out and are not allowed to escape into the surrounding water or air. 
     A further object is to provide a basin into which a boat is placed for cleaning, wherein the shape of the basin facilitates collection and removal of the substances cleaned off the boat and of the materials used to clean the boat. 
     Yet another object is to form a sheet of flexible waterproof material into a floatable, boat cleaning basin of desired shape, in which a boat may be placed for cleaning purposes, and which facilitates removal of contaminates that result from cleaning the boat in the water. 
     A still further object is to provide a collector that cooperates with the shape of a basin in which a boat may be cleaned while in the water for the purpose of facilitating the collection and removal of undesirable substances and cleaning materials. 
     Another object is to provide a boat cleaning apparatus that includes a cooperating pre-shaped basin and filtration system that facilitates movement of contaminated water and solid materials toward a collection area, collects contaminated water from the basin, and returns cleaned water to the basin. 
     An additional object is to provide a waterproof, floatable boat-cleaning basin that is made of flexible material, that can be configured to retain a desired shape under water and around the hull of a boat, and that resists billowing out of such shape by controlling the volume of water in the basin. 
     Another object is to provide a collector pipe for a boat cleaning apparatus that cooperates with the cleaning basin of the subject apparatus so that the pipe assists in maintaining the shape of the basin when a boat is floating in water within the basin. 
     A still further object is to return cleaned water to the pool of water in the cleaning basin of a boat maintenance apparatus so that the water is returned without causing undesirable turbulence in the pool. 
     An additional object is control the buoyancy of different parts of an apparatus for cleaning a boat in the water in order to control the positions of the parts and their interaction. 
     Yet another object is to provide a basin, a collector pipe, and return pipes used in a boat maintenance apparatus that cooperate to facilitate easy reversibility of the basin, so that both of its surfaces can be periodically cleaned. 
     Another object is to provide a gate for a cleaning basin of a boat cleaning apparatus wherein the gate is movable from an open position to a closed position, and while closing, releases water from the basin so as to assist in controlling the volume of water in the basin. 
     Still an additional object is to provide a gate for a cleaning basin of a boat cleaning apparatus wherein the end wall formed by the gate, and its opposite end wall in the basin, help to retain the desired shape of the basin during the boat cleaning operation. 
     Yet another object is to provide a boat maintenance apparatus that is adaptable for use by existing boat maintenance facilities so as to reduce the amount of pollution caused by such existing facilities during their boat maintenance operations; for boatyards that have slips used for boat maintenance; and for individual boat owners who desire to clean their own boats, especially routine maintenance on a more frequent basis. 
     An additional object is to provide a boat maintenance apparatus that is suitable for use with various sizes of boats and types of boats, including both powerboats and sailboats, and various sizes of docks and slips. 
     A further object is to provide a boat maintenance apparatus that is composed of parts that can be readily assembled and subsequently disassembled, and in the disassembled condition can be folded and otherwise arranged for transport and storage. 
     A still further object is to provide a boat maintenance apparatus that is resistant to the corrosive action and other adverse effects of seawater but may be cleaned or repaired if damage does occur. 
     These and other objects, features and advantages of the present invention will become apparent upon reference to the following description, accompanying drawings, and appended claims. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation of an embodiment of the subject boat maintenance apparatus floating in a floating dock, the apparatus including a cleaning basin and a filtration system. FIG. 1 shows the collector and return pipes of the filtration system removed from the basin and in resting positions on the dock and further shows the gate of the basin floating in an open position. 
     FIG. 2 is a top plan view of the apparatus and dock shown in FIG.  1 . 
     FIG. 3 is an end elevation of the apparatus and the dock as viewed from the left end of FIGS. 1 and 2 but with the collector and return pipes shown in their operating positions in the basin. 
     FIG. 4 is a view similar to FIG. 1 but with gate closed and the collector and return pipes in their operating positions. 
     FIG. 5 is top plan view of the apparatus and dock shown in FIG.  4 . 
     FIG. 5 a  is a somewhat enlarged, fragmentary section taken on line  5   a — 5   a  in FIG.  5 . 
     FIG. 6 is an end elevation of the apparatus and dock shown in FIGS. 4 and 5 as viewed from the left end of FIGS. 4 and 5. 
     FIG. 7 is a plan view of the main sheet from which the side walls and gate of the basin of the subject apparatus are formed, it being noted that, except for rolled sleeves at several edges, this sheet is lying flat with the side walls and gate being in a common plane. 
     FIG. 8 is a plan view of the end sheet constituting the end wall of the basin of the subject apparatus prior to its assembly with the main sheet shown in FIG.  7 . 
     FIG. 9 is an isometric view of the main and end sheets assembled into the basin of the subject apparatus showing the gate in an open position. 
     FIG. 9 a  is an enlarged fragmentary section taken on-line  9   a — 9   a  in FIG.  9 . 
     FIG. 9 b  is an enlarged fragmentary section taken on line  9   b — 9   b  in FIG.  9 . 
     FIG. 10 is a fragmentary perspective view of the dock and basin showing the gate in open position, it being noted that the collector and return pipes are omitted for clarity. 
     FIG. 11 is a view similar to FIG. 10 but showing the gate in a partially closed position, that is, showing the gate as it is being moved from its open position into its fully closed position wherein water in the chamber of the basin is allowed to escape into the surrounding water through a passageway between the panels of the gate. 
     FIG. 12 is also a view similar to FIG. 10 but showing the gate in its fully closed position. 
     FIG. 12 a  is a fragmentary enlarged plan view of the aft end of the basin, as viewed from a position indicated by line  12   a — 12   a  in FIG. 12, showing the gate nearly closed, this view being for the purpose of showing the relationship of the panels of the gate in their closed positions. 
     FIG. 12 b  is a fragmentary enlarged section taken on line  12   b — 12   b  in FIG.  12 . 
     FIG. 13 is a perspective view of the subject boat maintenance apparatus in fully assembled condition floating within a floating dock, showing the aft end of the collector pipe resting in the nadir of the basin, showing one of the return pipes and part of the return manifold both floating on the water in the basin, and showing the gate open. 
     FIG. 14 is a side elevation of the subject apparatus and dock, showing the gate in closed position and a boat floating in the pool of water in the basin. 
     FIG. 15 is a top plan view of the floating dock, the basin floating in the dock, and the boat floating in the basin, it being noted that the superstructure of the boat of FIG. 14 is omitted for simplicity and to indicate that boats of various types may be serviced in the subject apparatus, and it being further noted that return piping is shown floating both port and starboard and forward of the boat. 
     FIG. 16 is a transverse vertical section taken on line  16 — 16  in FIG.  15 . 
     FIG. 17 is schematic diagram of the filtration system used in the apparatus of the present invention. 
    
    
     DETAILED DESCRIPTION 
     The number  20  in the drawings generally indicates an embodiment of a boat maintenance apparatus for cleaning the hull and other parts of a boat. The apparatus may be supported in the water from a dock or slip  22 , or other suitable structure. As shown, the dock is floating in seawater  24  and is U-shaped having spaced side portions  26 , a closed forward portion  28 , and an open aft end  30 . Notwithstanding the reference to “seawater,” it is understood that the subject invention is not limited to use in seawater but may be used in bodies of fresh water, although it is more likely to be used in cleaning boats that have been subjected to the effects of seawater. For purposes of subsequent reference, the level of the water outside of the apparatus is indicated by the number  32 . The dock is provided with a plurality of cleats  36  spaced along the side and rear portions. With particular reference to FIGS. 1-6 and  10 , the subject boat maintenance apparatus  20  includes a cleaning basin  42  and a water filtration system  44 . Each of these main components of the subject apparatus will now be described in detail. 
     The basin  42  (FIGS. 7-9) is made of sheet material that is flexible, durable, chemically and ultraviolet resistant, waterproof or impervious, relatively lightweight, and resistant to algae and other corrosive and deteriorating effects of seawater. Development of the subject apparatus indicates that vinyl sheet of the type used for lining swimming pools is very suitable for the purposes of the present invention. More particularly, thirty-mil vinyl sheet sold under the trademark Plastimayd by the Plastimayd Corporation of Clackamas, Oreg., 97015, has been successfully used for the subject basin. It should be understood, however, that there are many other sheet materials having the foregoing qualities that would be suitable for the subject basin, and thus the invention is not limited to the Plastimayd sheet. In general, my development indicates that sheet material of the foregoing qualities of a thickness in the range from about thirty mils to about forty mils is preferable for the subject basin. Moreover, for a basin to be used in a dock having a length of about forty-eight feet and an opening of about eighteen feet, a basin made of the Plastimayd sheet will weight approximately two hundred-fifty pounds, a weight that can be handled by one person. Sheet materials that result in much greater weight could be used but because of the handling problem, are not preferred. 
     With continued reference to FIGS. 7-9, the basin  42  is formed from an end sheet  50  and a main sheet  52  of the selected material. The end sheet or piece is planar and in the shape of an equilateral triangle having side edges  54  and an upper edge  56 . The end sheet constitutes the end wall of the basin and for simplicity is given the same reference numeral, namely  50 , as the end wall The upper edge of the end wall is formed with a sleeve  58  along its length. 
     The main sheet  52  is also shown in its flat planar condition in FIG.  7 . Although this main sheet is formed into a V-shape, it will first be described in its flat condition so as to enable a better understanding of how the basin is formed. In its flat condition, the main sheet may be thought of as being divided into the various walls or panels of the basin into which it will be formed, it being understood that in the preferred embodiment, these walls and panels are not delineated on the sheet, although for descriptive purposes, they are so illustrated in the drawings. Thus, the sheet has rectangular, planar port and starboard side walls  64  and  66  with each sidewall having an upper edge  68 , a forward end edge  70 , an aft end edge or fold line  72 , the later being shown in dashed lines to indicate that it is merely an eventual fold line in the sheet. The side walls meet along a central juncture or eventual fold line  74  that extends from one end edge  70  to the other end edge  72  of the panels. The end edges  70  and  72 , the upper edge  56 , and the side edges  54  are all of equal length. In addition, the upper edges  68  and the juncture  74  are of equal length. 
     Sleeves  80  (FIGS. 7-9) are provided along the upper edges  68  of each side wall  64  and  66 , extending from end to end of the upper edges. In addition, grommets  82  are provided in the side walls in inwardly adjacent relation to the sleeves at the forward and aft comers and centrally therebetween. 
     The main sheet  52  of the basin  42  also includes a gate  90  (FIGS. 7 and 9) that extends rearwardly from the side walls  64  and  66  and is planar with the side walls when the sheet is laid out flat as shown in FIG.  7 . As with the walls  64  and  66 , the main sheet may be thought of as having port and starboard panels  92  and  94  and an intermediate panel  96  between the port and starboard panels. The port and starboard panels have outer edges  98  equal in length to the length of the edges  54 ,  56 ,  70  and  72 . The intermediate panel also has an outer edge  100  of this same length and which joins the outer edges  98  of the port and starboard panels. Sleeves  102  of smaller diameter than the sleeves  58  and  80  are formed in the outer edges  98 . 
     With continued reference to FIGS. 7,  8  and  9  and, the main sheet  52  is initially folded along the juncture  74  to bring the side panels  64  and  66  into a V-shaped relationship to each other. It is to understood that because of the sheet material used, such folding produces merely rounding along the juncture as opposed to creasing. The end sheet or wall  50  is assembled with the folded main sheet so that the side edges  54  mate with the forward end edges  70  and the upper edge  56  spans the distance between the forward ends of the upper edges  68 . The end and side walls are then hot sealed together in this assembled relationship, as best seen in FIG. 9, wherein the end wall maintains the side walls in the V-shaped relationship, although with the gate  90  open and the basin  42  not confined within the dock  22 , as shown in FIG. 9, the side walls may diverge rearwardly somewhat towards the gate. When the gate is closed, however, in a manner to be described, and as shown in FIGS. 5,  6 ,  12  and  15 , for example, the complete basin  42  is formed with the gate having the same triangular shape and size as the end wall  50 . 
     To describe the closing of the gate  90 , reference is initially made to FIG.  7 . There, it will be seen that the starboard and port panels  92  and  94  have imaginary first and second fold lines respectively  106 ,  108 ,  110  and,  112 . All of these fold lines as well as the center fold line or juncture  74  of the panels intersect at a point  114 . The first fold lines  106  and  110  of the starboard and port panels are collinear, whereas the second fold lines  108  and  112  extend from the intersection point  114  rearwardly to the aft ends or corners  116  and  118  on the starboard and port panels, respectively. 
     Closing of the gate  90  may be initiated at either the starboard or the port panel  92  or  94  (FIGS.  7  and  9 ). Assuming that closing of the gate is initiated with the starboard panel, the corner  116  of the starboard panel is brought transversely of the basin  42  to the aft end of the upper edge  68  of the port side wall  64 . In so doing, the gate folds along the first fold line  106  and the second fold lines  108  and  112 . This causes the intermediate panel  96  to be brought into substantially parallel relation with the port panel  94  and the starboard panel  92  to be brought into parallel relation with the end wall  50 . It is to be noted that the folds along the first fold line  106  and the second fold line  112  project outwardly of the basin, whereas the fold along the second fold line  108  projects inwardly of the basin. In other words, the second fold line  108  is brought into substantially parallel, adjacent relation to the first fold line  110 . 
     Closing of the gate (FIGS. 7 and 9) is completed by bringing the now adjacent and parallel port and intermediate panels  94  and  96  transversely forwardly up into adjacent parallel relation against the starboard panel  92 , with the folding action occurring along the second fold line  108  and the first fold line  110  so that the first fold line  106  and the second fold line  112  are now in adjacent parallel relation to each other. The gate is then held in this closed position in a manner to be described thereby forming the basin into a polyhedral, trough shape, or what may be visualized as an inverted tent. 
     With the basin  42  (FIGS. 4-6) formed in the manner described above and understanding that the basin is used in a horizontal upwardly open orientation, the side walls  64  and  66  converge or slope downwardly to the juncture  74  which constitutes a nadir at the bottom of the basin. Moreover, the side and end walls  64 ,  66  and  50  meet in a lower forward tip  122 , the side walls and the gate  90  meet in an aft tip  124 , with the nadir extending the full length of the basin between these tips, and the end wall and the gate are in opposed parallel relation to each other. In the closed position of the gate, the basin provides a chamber  130 , which is substantially sealed by the integral association of the end and side walls and because of the folded relationship of the panels  92 ,  94  and  96  of the gate. 
     Hollow side and end flotation tubes  140  and  142  are fitted in the side and end sleeves  80  and  58 , respectively, of the basin  42 , and have their ends capped. These tubes are preferably made of PVC flotation pipe (FIG. 5A) of sufficient diameter to provide positive buoyancy in order to support the basin  42  in the water. On the other hand, flotation tubes  146  (FIGS. 9,  9 A) are fitted in the sleeves  102  of the port and starboard panels  94  and  92  but are filled with lead shot  148 , and their ends capped, in order to provide these tubes with a measure of negative buoyancy, for a purpose to be described. Still further, grommets  150  are provided in the port, starboard and intermediate panels  94 ,  92 ,  96  adjacent to corners  116  and  118  and the fold lines  106  and  110 . 
     The basin  42  is fitted within the slip of the dock  22  as best seen in FIGS. 2,  3 ,  5 ,  6 ,  13  and  15 . It will thus be understood that the sheets  50  and  52  from which the basin is constructed are dimensioned so as to fit the basin within the slip and that these dimensions may be varied to fit slips of various sizes. That is, as fitted in the slip, the end wall  50  and the upper edges  68  of the side walls  64  and  66  are in closely adjacent spaced relation to the front and sides  28  and  26 , respectively, of the dock. Furthermore, the common aft end edge  72  of the side walls is in substantial alignment with the opening  30  in the dock so that when the basin is fully within the dock, the gate  90  in its open position extends rearwardly from the dock, as best seen in FIGS. 1,  2 ,  10  and  13 . Because of the flotation tubes  140  and  142  as well as the sheet material from which the basin is made, the basin floats within the dock and is moveable upwardly and downwardly in the water relative to the dock. 
     Because of the negative buoyancy of the flotation tubes  146 , however, the gate  90  in its open position extends downwardly and rearwardly from the aft end of the dock as seen in FIGS. 1,  3 ,  10  and  13 . The buoyancy of the flotation tubes is adjusted by adding more or removing some of the lead shot  148  in the tubes so as to maintain the gate at the desired downwardly sloping angle in its open position. In other words, the gate must extend rearwardly and downwardly in order to allow entry and egress of boats into and out of the basin  42  without the keel, the rudder or propeller of a boat becoming fouled with the basin. Furthermore, the gate must not hang vertically downwardly from the dock since this will tend to lift the sidewalls  64  and  66  upwardly, again causing interference with the boat. Tie lines  160  (FIGS. 2,  3 ,  5 ,  6 ,  15  and  16 ) extend through the grommets  82  in the basin and are fastened around the cleats  34  thereby tethering the basin to the dock while allowing relative vertical movement of the basin and the dock. 
     As thus floating and tethered, the side and end walls  64 ,  66  and  50  of the basin  42  extend downwardly from the dock  22  with the side walls in the previously described V-shaped relationship. The construction of the basin  42  in the manner described above is accomplished so as to provide an angle of decline or slope of the side walls that is from about forty-five degrees to about sixty degrees to the horizontal. With the gate  90  open, as shown in FIGS. 1,  2  and  3 , for example, water of course enters the basin from the surrounding sea water  24 . The trough-like or inverted tent shape of the basin results from the construction of the basin, as above described, but also because the weight of the water within the basin tends to maintain this shape, as long as the weight of the water does not exceed certain limits, as further described below. 
     With the gate  90  in closed position (FIGS. 5,  12  and  15 ), the end and side walls  50 ,  64  and  66  and the gate form the closed working or cleaning chamber  130  previously described. Moreover, when the gate closes, it captures a pool  170  of water in the chamber having a water level  172  very close to but below the upper edges  56  and  58  of the basin including the gate. Since the forward end wall  50  is integral with the side walls, no water can escape from the forward end of the basin. In addition, because of the folded panels  92 ,  94  and  96  of the gate, the gate essentially seals the aft end of the basin so that no water can escape through this route (FIG.  12 A). 
     In order to limit the amount of water that is retained in the pool  170 , the gate  90  allows water to exit from the basin  42  while the gate is being closed. More specifically, with reference to FIGS. 10,  11  and  12 , the steps of closing the gate are further described. When the starboard corner  116  is brought up to the aft end of the port sleeve  80 , a passageway  180  is formed between the intermediate and port panels  96  and  94 , allowing water to escape from the basin into surrounding sea water as indicated at  182  (FIG.  11 ). When the port and intermediate panels are folded up against the starboard panel  92 , as shown from FIG. 11 to FIG. 12, water is allowed to escape at  184  from between the intermediate and starboard panels. How this latter escape of water occurs can also be visualized by reference to FIG.  12 A. Thus, by limiting the volume of water in the basin and by allowing the basin to float within the dock  22 , the pool  170  of water effectively maintains the V-shape of the basin without causing the basin to balloon or billow outwardly and downwardly as might occur if the upper edges  56  and  68  of the basin were securely tied by the lines  160  to the cleats  34 . Even if the basin sinks down far enough to place the tethering tie lines  160  under tension, the flotation tubes  140  and  142  have a tendency to yield somewhat and counteract a tendency of the basin to balloon in the water out of its desired shape. Of course, another reason for maintaining the level  172  of the pool  170  below the upper edges of the basin is to isolate the pool  170  from the surrounding sea water. 
     The downwardly sloping, planar walls  64  and  66  of the basin  42  (FIGS. 3,  6 ,  9 ,  16 ) of the present invention are to be contrasted with the concave, rounded shape of the walls of the bag of my prior U.S. Pat. No. 5,138,963. As will be described in more detail subsequently, the side walls of the basin of the present invention are sloped at favorable angles directed toward the juncture  74 , which is at the nadir of the bottom of the basin, in order to allow substances that settle on the side walls to gravitate toward the nadir. 
     The water filtration system  44  (FIGS. 5,  13 ,  15  and  17 ) of the subject apparatus  20  includes a pump  200 , a filter  202 , a collector pipe  204 , return piping  206 , an collector hose  208  interconnecting the collector pipe and the pump, and a return hose  210  interconnecting the filter and the return piping. The collector pipe is elongated and perforated having a forward end  216 , an aft end  218 , and provided with a plurality of apertures  220  along its full length from the forward end to the aft end. The length of the collector pipe is approximately the same as the length of the juncture or nadir  74  in the basin  42  and lies along this nadir with the forward end  216  adjacent to the forward end wall  50  and the aft end adjacent to the gate  90 . As positioned in the basin, the apertures of the pipe are directed upwardly and preferably also laterally, as shown in FIG.  5 . The collector pipe may be made of plastic, metal, a composite or other suitable material. 
     The collector pipe  204  is merely rested in the nadir  24  of the basin  42  but is not attached to the basin. As such, the collector pipe can readily be moved from its operating position in this nadir, as shown in FIGS. 4-6 and  13 - 16 , into a displaced position on one of the side portions  26  of the dock  22 , as shown in FIGS. 1-3. The collector pipe has sufficient weight so that when it is located on and in the nadir of the basin, it remains in that position and helps to hold the basin in its V-shaped or trough configuration, as discussed above. The return piping  206  (FIGS. 5,  13 ,  15  and  17 ) includes a forward, floatable manifold  221  having a diameter approximately the same as the collector pipe  204  and floating on the pool  170  of water in the chamber  130  in adjacent spaced relation to the forward end wall  50  of the basin and with its opposite ends in adjacent spaced relation to the upper edges  68  of the side walls  64  and  66 . Elongated floatable lateral return pipes  222  are individually connected by quick connect swivel couplings  224  to the ends of the manifold and have capped aft ends. The manifold and the return pipes are made of PVC flotation pipe so that the return piping readily floats on the surface  172  of the pool  170 . The return pipes are of a diameter less than that of the manifold or the collector pipe and have inwardly and downwardly directed apertures  230  along the entire length of each return pipe. The length of the return pipes is approximately the same as the length of the basin so that the aft ends of the return pipes are adjacent to gate  90 . Also, the length of the manifold is such that the U-shaped return piping fits within the upper portion of the basin  42  with the return pipes in adjacent spaced relation to the side walls  66  and  64  and so that the return piping may float up and down within the basin a limited distance without necessarily resting on the side walls. 
     With reference to the hydraulic filtration circuit shown in FIG. 17, the collector hose  208  connects the forward end  216  of the collector pipe  204  to the inlet of the pump  200 , and the return hose  210  connects the outlet of the filter  202  to the manifold  221  intermediate the ends thereof. It will thus be understood that with the pump operating, water and water borne contaminants are sucked through the apertures  220  of the collector pipe  204 , drawn by the pump into the filter, and forced by the pump through the filter wherein contaminants are removed from the water. Clean water exits through the return hose into the manifold where it passes into the return pipes and from there through the apertures  230  back into the pool. The apertures in the return pipes are directed downwardly and slightly inwardly over the sloping side walls  64  and  66  and create a gentle downwardly directed current causing the solid materials in suspension in the pool to gravitate downwardly onto the side walls and thence downwardly toward the collector pipe. The apertures  230  in the return pipes are of smaller diameter than the apertures  220  in the collector pipe and are more numerous than the apertures in the collector pipe. Thus clean water is returned to the pool in a gentle shower from each of the return pipes rather than in a higher velocity jet that would emanate from a single return pipe, the later causing turbulence in the water which would counteract the natural tendency of particulants in the pool to gravitate onto the side walls. 
     Because the both the collector pipe  204  and the return piping  206  are not attached to the basin, they may be readily manually lifted from their operating positions into resting positions on the dock  22 , as illustrated in FIGS. I through  3 . This construction allows the basin to be easily reversed in order to keep both the inside and the outside surfaces of the basin clean. By reversal of the basin is meant to remove the basin from the dock by untying the lines  160  and  270 , turning it inside out so that the surface of the basin that previously faced downwardly in the water will now face upwardly into the chamber. Since there is no outlet cut in the bottom of the basin or associated fitting, as provided in my prior U.S. Pat. No. 5,138,963, and since the pipes  204  and  205  are removable as described, the reversal of the basin is greatly facilitated. As will be understood, the basin is symmetrical irrespective of which surface faces up and, as above noted, has sufficient flexibility to allow it to be turned inside out as it is being reversed, and is light enough to be handled for this purpose. Moreover, this reversal may be accomplished whether the gate  90  is open or closed. Once the basin has been reversed, it is again placed within the dock, tethered thereto by the lines  160 , and both the collector pipe  204  and the return piping  206  are returned to the positions previously described. 
     OPERATION AND DESCRIPTION OF THE METHOD 
     As previously indicated, the subject boat maintenance apparatus  20  may be used to clean or otherwise maintain or service various types of boats, but a sailboat  250  is generally shown in FIG. 14 to illustrate how the subject apparatus may be used. Although the apparatus is ideally suited for boat cleaning purposes, other types of service or maintenance may readily be accomplished, such as under-hull or keel inspections or servicing the engine for example. For convenient reference, the boat shown has a bow  252 , a stern  254 , a mast  256 , a hull  258 , a keel  260 , a rudder  262 , and a deck  264 . 
     Assuming that the basin  42  is suspended and floating within the dock  22 , that both the collector pipe  204  and the return piping  206  are placed in their operating positions, and that the boat  250  is to be cleaned, the gate  90  is opened as seen in FIGS. 1-3,  10  and  13 . In its open position, the gate extends downwardly and rearwardly from the dock, as shown in FIG. 1, and is maintained in this attitude by the negative buoyancy of the flotation tubes  146  in the gate. The boat  250  is then moved into the basin over the open gate without the keel or rudder becoming fouled with the gate or the bottom of the basin since the gate is maintained at an appropriate sloping position below such parts of a boat. After the boat is completely within the basin, the gate is closed by manually handling the sleeved flotation tubes  146  and folding the panels  92 ,  94 , and  96  together in the manner previously described. It is to be understood at this point that either the port panel or the starboard panel may be initially brought toward its kitty-corner aft end of the sleeves  80 , although as above described and as shown in FIGS. 10 through 12, the starboard panel is initially folded upwardly. 
     Assuming that the gate  90  is closed as illustrated in FIGS. 10-12, the corner  116  of the starboard panel  92  is fastened to the kitty-corner aft end  118  of the port sleeve  80 , and the corner  118  of the port panel  94  is fastened to the aft end of the cattycorner starboard sleeve, both by tie lines  270 . As previously mentioned, during the closing of the gate, water escapes as indicated at  182  and  184  thereby to equalize the pressure inside and outside of the basin so as to prevent the capture of water in the pool  170  from causing the basin to billow out of its desired shape. It is to be noted that the presence of the flotation tubes  160  in the sleeves  102  of the port and starboard panels not only assists in closing the gate but also helps to maintain the lateral V-shaped configuration of the basin. 
     It is here to be noted that the use of the terms “forward” and “aft” may suggest that a boat, such as  250 , must always enter the apparatus  20  with its bow  252  first. It will be understood, however, that a boat may be backed in if so desired since the apparatus  20  will operate the same irrespective of which end of the boat enters the apparatus first. 
     With the boat  250  floating in the pool  170  of water in the chamber  130  (FIGS.  14 - 16 ), several dimensional relationships are to be noted. Thus, the maximum transverse dimension of the basin  42  between the upper edges  68  is greater than the maximum width of the hull  258  so that port and starboard spaces are provided on opposite sides of the hull, between the hull and the sidewalls  64  and  66  of the basin. Likewise, the length of the basin is longer than the boat so as to provide for minimal aft spaces between the forward end wall  50  and the bow  252  and between the gate  90  and the stern  254 . These port and starboard spaces and the forward space provide room for the return piping  206  to float in the pool around the boat. Still further, the depth of the basin is sufficient to provide space between the keel  258  and the rudder  262  and the collector pipe  204  as well as the nadir  74  of the basin. Working space is thus provided around the boat for divers to operate in the chamber for cleaning the hull of the boat. If additional space is required at a particular location the boat can be moved transversely and longitudinally within the chamber by limited amounts. In this regard and as mentioned above, the principles of the present invention are adaptable to boats of various sizes, that is, the apparatus may be made larger or smaller as desired, although the invention is particularly suited for use with boats from about thirty feet in length to about seventy feet in length. 
     In this regard, it may be useful to provide the dimensions of a working example of the basin  42  of the present invention in order to gain an appreciation of the sizes here involved. In this example, the length of the sidewalls  64  and  66  laid out is approximately forty-eight feet, and each edge  54 ,  56 ,  98  and  100  is about eighteen feet, so that the total length of the forward and aft edges  70  and  72  in this example is about thirty feet. In the formed basin, however, the maximum transverse dimension of the basin in this example is about eighteen feet. If the basin is made of the Plastimayd vinyl sheet, the weight of such a basin approximates two-hundred pounds, as previously mentioned. 
     With the gate  90  closed behind a boat  250  in the chamber  130  (FIGS.  14 - 16 ), a closed fluid system is achieved by the filtration system  44  operating in the pool  170  of water in the chamber  130 . That is, after the boat  250  is within the closed chamber  130 , the filtration system  44  is turned on and a diver or divers enter the pool  170  and are free to move about in order to work on the hull  258 , the keel  260 , the rudder and other parts of the boat accessible to the diver or divers. The divers normally use scrub brushes to clean the hull and other underwater parts of the boat causing the removed materials to enter the water. These materials may include toxics such as lead from paint removed from the hull. The deck  264  of the boat may also be cleaned allowing the dirty water to wash over the sides of the boat into the pool. 
     Debris removed from the boat  250  (FIGS. 14-16) as well as cleaning materials used above the waterline enter the pool  170  of water and settle onto the side walls  64  and  66 . Because these walls are planar and sloped toward the nadir  74 , the solids and particulates in the water gravitate down these walls toward the collector pipe  204 . There, the water and water borne solids are sucked into the collector pipe through the apertures  220  and are carried by the pump into the filter. The filter removes the contaminants and releases clean water to the manifold  221  and the return pipes  222 . Clean water exits the return pipes in gentle sprays through the apertures  230  onto the upper surface of the pool adjacent to and above the side walls. This gentle downward spray or shower of clean water tends to establish currents causing the suspended materials to gravitate onto the side walls and toward the collector pipe. 
     The slope of the side walls  64  and  66  (FIGS. 14-16) and the spray of clean water from the return pipes  22  greatly facilitate movement of settling solids toward the collector pipe  204 . Moreover, the reach of the collector pipe throughout the entire length of the basin  42 , that is the length of the nadir  74 , greatly improves the speed and thoroughness of circulation and removal of contaminated water from the pool. This is to be contrasted with my prior U.S. Pat. No. 5,138,963 wherein all of the contaminated water must enter the single outlet from the basin. Since this is a relatively closed system, the pool  170  is isolated from the surrounding sea water  24  so that the water borne contaminants do not enter the surrounding sea water nor even the surrounding air since the substances remain in the water, gravitate into the collector pipe, and are immediately sent into the filter  202 . 
     After the boat  250  (FIGS. 14-16) has been cleaned or otherwise serviced, the divers exit from the pool  170 , and the filtration system  44  continues to operate in order to clean the water in the pool sufficiently to allow the gate  90  to be opened. Experience shows that after the diver or divers have completed their cleaning operating, the water in the pool is very discolored and may even appear to be black. Before the gate can be opened, therefore, it is necessary to clean this water so that its clarity returns to a normal state of cleanliness. It is here noted that when the divers are in the pool and cleaning the hull, there is considerable turbulence in the water tending to prevent the unwanted solids from gravitating toward the collector pipe  204 . With the divers out of the water and cleaning operation completed, the water in the pool can become more placid, and for thorough cleaning of the pool, it is important that the water in the pool remain in a relatively quiet state. Since it is necessary to continue to operate the filtration system  44  in order to clean the water in the pool, however, the water would remain turbulent if the cleaned return water were merely ejected back into the pool in a strong stream, as in my earlier patent cited above. The subject return piping  206  avoids this problem. That is, the use of the return pipes  222  that feed the returning clean water to the pool in a gentle shower along each side wall  64  and  66  minimizes the turbulence in the water. As a result, not only is the turbulence minimized but the gentle shower of water over the side walls tends to assist in causing solid materials to gravitate toward the collector pipe  204  along the side walls. 
     Although a preferred embodiment of the present invention has been shown and described, various modifications, substitutions and equivalents may exist without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been disclosed by way of example and not by way of limitation.