Catamaran adapted for use as a scuba diving platform
FIELD OF THE INVENTION 
     This invention relates to a boat hull structure adapted for scuba diving and, more particularly, to a catamaran with such boat hulls which provides a particularly stable platform for scuba divers and their equipment. 
     BACKGROUND OF THE INVENTION 
     Catamarans are well known and available commercially. Collapsable and towable catamarans are also well known as is evidenced by, for example, U.S. Pat. No. 4,813,366 issued Mar. 21, 1989 and U.S. Pat. No. 5,313,908 issued May 24, 1994. Typically, a catamaran includes a pair of spaced-apart, elongated pontoons secured in position by fore and aft cross braces, with or without longitudinal braces, with a platform secured to the cross braces. 
     The pontoons usually are hollow, providing storage room in some catamarans and even providing sleeping room in large catamarans. The present invention is directed at small catamarans which may be collabsable and self trailering. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In accordance with the principles of this invention, a pontoon structure for a catamaran is designed to hold a plurality of scuba tanks in upright positions and protruding above the top surface of the pontoon. The protruding portions of the scuba tanks are used as supports for mating seat backs which slip over the exposed portions of each pair of scuba tanks. 
     The pontoon is fitted with a cylindrical recess for each scuba tank. Each recess has a lower platform on which a scuba tank rests and below which is a chamber which includes an expandable bladder. An air hose is connected to the bladder and includes, at it,s distal end, a fitting for attachment to a scuba tank or any source of air. The bladder can be inflated to fill the chamber and thus exhaust any water which may have accumulated there. An individual chamber may be formed beneath each cylindrical recess or a community chamber may be defined beneath all cylindrical recesses in which case only a single bladder need be used. 
     The arrangement not only provides secure storage for a large number of scuba tanks but also uses those tanks for increased comfort and for ensuring seaworthiness of the boat. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1-4 are side, top, front and rear views of a catamaran in accordance with principles of this invention; 
     FIGS. 5-10 are schematic views of the scuba tank holder assembly showing the structure thereof with a water-exhausting bladder in various levels of expansion during operation; and 
     FIGS. 11 and 12 are schematic views of a self-trailoring arrangement for the catamaran of FIGS. 1-10. 
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS OF THIS INVENTION 
     FIG. 1 is a schematic side view of a catamaran pontoon 10 in accordance with the principles of this invention. The pontoon, in the preferred embodiment herein, is sixteen feet long and two feet wide as indicated in the figure. 
     FIG. 2 is a schematic top view of a catamaran including two pontoons, 10 and 11, both of the type shown in FIG. 1. The two pontoons are fixed in a spaced-apart, parallel relationship by support members 14, 15 and 16 which attach to the pontoons and define a support for a platform (not shown) which mates with outer lip 18. Each pontoon conveniently includes a rear stairwell, 20 and 21, for pontoons 10 and 11 respectively. Each pontoon is two feet wide. 
     As is clear from FIGS. 1 and 2, each pontoon is fitted with a plurality (six as shown) of cylindrical recesses, accessable from the top surfaces 23 and 24 of pontoons 10 and 11 respectively. The recesses terminate, at their lower ends, at a floor or platform 25 conveniently of marine plywood or other suitable material. The recesses have cylindrical geometries to receive scuba tanks 26 which, as can be seen in figures, protrude beyond the top surfaces of the pontoons in the preferred embodiment. 
     FIGS. 3 and 4 show, schematically, the front and rear views, respectively, of the catamaran of FIG. 2. The rear support 16 can be seen to function as a transom on which an outboard motor 30 can be attached. 
     In a preferred embodiment,the chamber 50, formed between platform 25 and the hull of a pontoon (10) of FIG. 1, is divided into sections or chambers, each of which includes an inflatable bladder. An illustrative geometry for such a chamber is shown in FIG. 5. Specifically, FIG. 5 shows an illustrative cylindrical recess 51, with a platform 52 at it&#39;s lower end. Platform 52 has a boot 53 attached to it for receiving a scuba tank. The top surface of the pontoon includes a hole 54 through which a scuba tank protrudes. 
     Platform 52 defines a chamber 56 containing a bladder 57. The bladder is fitted, at it&#39;s lower extremity, with an air hose attachment 58. A hose 59 is connected to the attachment to provide a path for inflating the bladder. The hose includes a fitting at it&#39;s distal end for attachment to a scuba tank or to an alternate air supply indicated at 60 in FIG. 6. 
     FIGS. 5 and 6 also show water expansion channels 62. The channels provide an exit channel for water being forced out of chamber 56 when the bladder in the chamber is expanding. The channels terminate at holes 64 in the top surface of the pontoon as shown in FIGS. 5 and 6. 
     FIGS. 7 and 8 show an embodiment where the cylindrical recess 70 is fitted with a lower platform which is movable along a vertical axis as viewed in FIG. 67. In this embodiment, a bladder 72 is sufficiently large to fill the entire vertical recess when inflated. FIG. 8 depicts the situation when the bladder is fully inflated. It can be seen that, in an emergency situation,virtually the entire internal cavity of the potoon can be filled with air eliminating any water which may have accumulated there. With the bladder fully inflated, the platform (71) is positioned just below the top surface of the pontoon as shown in FIG. 8 with the scuba tank completely protruding from it&#39;s recess. The top of the bladder conveniently includes a release plug 90 as shown in FIG. 9 with support platform 71 including an aperture (not shown) for accessing the plug. 
     FIG. 10 shows a molded back support 100 which includes side sleeves or fittings 101 and 102 for slipping over a pair of adjacent protruding scuba tanks 103 and 104 as shown in the figure. Support 100 can be shaped to receive seat and back cushions for providing a considerable degree of comfort for a relatively small catamaran rigged for scuba diving. 
     The entire catamaran herein can be made of fiber glass and can be made collapsable and self towing by including swivel wheel assemblies or swiveling pontoons with attached wheels assemblies. The latter arrangement is shown in FIGS. 11 and 12. FIG. 11 shows the position of two pontoons 110 and 111 when in a spaced-apart position for use. It can be seen that wheel assemblies 113 and 114 are positioned above the bottoms of the hulls. FIG. 12 shows the pontoons swivelled upwards at hinge lines 116 and strapped in place by straps 117 so that the wheels extend below the bottom of the hulls as shown. With the pontoons in the swivelled-up position of FIG. 12, of course, the top surfaces 118 and 119 of the pontoons are facing downwards and the wheels are positioned below those faces to contact the ground when the catamaran is being trailored. 
     The invention has been described in terms of a catamaran, but it should be clear that an individual pontoon, in accordance with this invention, could be used in other than a catamaran configuration as with outriggers.