Patent Publication Number: US-6213042-B1

Title: Small waterplane area multihull (SWAMH) vessel with submerged turbine drive

Description:
FIELD OF INVENTION 
     The present invention relates to improvements in small waterplane area multihull (SWAMH) vessels. Specifically, the present invention provides a SWAMH vessel having an upper hull platform which is maintained above the surface of a body of water by at least two submerged hulls joined thereto by supporting struts. The submerged hulls are filled with a buoyant core material and house a rotary propulsive means. An engine means present on the surface platform outputs work which is transmitted to the rotary propulsive means through a work translating means to effect movement of the vessel. 
     BACKGROUND OF THE INVENTION 
     Small waterplane area multihull (SWAMH) vessels are multihull vessels comprising at least two submerged hulls which are connected to a work platform or upper hull that resides above the water. Connections are made by elongated struts which have a cross-sectional profile substantially smaller than that of the submerged hulls. Constructed in this manner, the vessel through water presents a platform or hull which is relatively insensitive to water surface disturbances; however, large propulsive forces are required to impel a SWAMH vessel due to combined effects of frictional resistance of the large wetted surface of the hulls and interference resistance occurring as an interaction between the twin hulls. Numerous attempts have been made to improve the performance of watercraft in general and of SWAMH vessels in particular, whether to improve the buoyancy, durability or handling capabilities of a vessel or to improve the performance characteristics of passive motivating means such as sails or active motivating means such as engines or oars. 
     Attempts have been made in the prior art to improve both buoyancy and performance have included using multiple hulls and double walled hulls having a buoyant material entrained therebetween. For example, U.S. Pat. No. 3,811,141, issued May 21, 1974 to Stoeberl; U.S. Pat. No. 3,911,190, issued Oct. 7, 1975 to Myers et al.; U.S. Pat. No. 4,094,027, issued Jun. 13, 1978 to Vernon and U.S. Pat. No. 4,118,814, issued Oct. 10, 1978 to Holtom disclose double walled boat hulls, typically for multi-hull vessels, that include a buoyant material such as a gas or foam between the walls. U.S. Pat. No. 5,613,460, issued Mar. 25, 1997 to Stallard shows a submarine which has an outer skin which surrounds a foam. This foam is intended to provide buoyancy to compensate for external weapons launch systems. 
     U.S. Pat. No. 3,842,772, issued Oct. 22, 1974 to Lang teaches a vessel shaped to reduce the effect of large waves striking a platform. The semi-submerged ship has two elongated hulls which include a propeller at the stern thereof. U.S. Pat. No. 4,557,211, issued Dec. 10, 1985 to Schmidt, similarly has a pair of submerged hulls. The hulls provide a buoyancy support for the upper hull and have propellers at the sterns thereof. U.S. Pat. No. 5,313,906, issued Zapka discloses a SWAMH vessel per se. U.S. Pat. No. 5,184,561, issued Feb. 9, 1993 to Nickell, Jr. shows a vessel including finned planing pontoon hulls. 
     U.S. Pat. No. 3,338,203, issued Aug. 29, 1976 to Moore shows a watercraft hull fashioned of plural lighter than air gas filled compartments and U.S. Pat. No. 4,802,427, issued Feb. 7, 1989 to Biegel discloses a ship hull including sub-hulls that reduce pitch, roll and yaw. U.S. Pat. No. 5,178,085, issued Jan. 12, 1993 to Hsu teaches the wave cancellation properties of a multi-hull ship. 
     Propulsion systems have been the targets of improvements as in U.S. Pat. No. 4,838,819, issued Jun. 13, 1989 to Todorovic which discloses a marine propulsion unit including a ducted turbine having side inlets. U.S. Pat. No. 4,505,684, issued Mar. 19, 1985 to Holden et al. shows a thrust tube propulsion system including propellers disposed within the thrust tubes. U.S. Pat. No. 5,722,866, issued Mar. 3, 1998 to Brandt; U.S. Pat. No. 5,435,763, issued Jul. 25, 1995 to Pignata and U.S. Pat. No. 5,181,868, issued Jan. 26, 1993 to Gabriel relate to belt- and gear-driven turbines. 
     U.S. Pat. No. 2,941,495, issued Jun. 21, 1960 to Goldman shows a water craft propulsion system utilizing an impeller with spiral veins and a housing. U.S. Pat. No. 3,055,331, issued Sep. 25, 1962 to Singelmann teaches a centrifugal pump assembly driven with a turbine which is propelled by a jet engine. U.S. Pat. No. 5,722,864, issued Mar. 3, 1998 to Andiarena shows a marine propulsion system which includes a rotational unit having blades rigidly secured to the inner periphery of the rotational unit. 
     Despite the teachings of the prior art, a need still exists for a multihull vessel which is stable, maneuverable and sturdy and which can efficiently accommodate an active propulsive means which optimizes the passage of the vessel through the water. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a SWAMH vessel having a surface platform whereon an easily accessible engine or plurality thereof are situated. 
     It is another object of the present invention to provide a SWAMH having at least two submerged hulls which are filled with a buoyant core material, are joined to the surface platform by support struts and house a rotary propulsive means which is powered by the engine or plurality thereof through a work translating means. 
     It is an additional object of the present invention to provide a SWAMH vessel wherein the entire body of each submerged hull has utility in being a housing for a rotary propulsive means and aids in the channeling of water therethrough to increase the efficient propulsion of the vessel. 
     Additional objects, advantages and novel features of the present invention will be set forth in part in the description which follows and in part will become apparent to those skilled in the art upon examination of the following specification or may be learned by practice of the invention. To the accomplishment of the above-related objects, this invention may be embodied in the forms illustrated in the accompanying drawings, attention being called to the fact, however, that the drawings merely are illustrative, and that changes may be made in the specific construction illustrated and described within the scope of the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be better understood with reference to the appended drawing sheets, wherein: 
     FIG. 1 is an environmental rear view of a SWAMH vessel of the instant invention situated it water. 
     FIG. 2 is an axial cross sectional view of a submerged hull and supporting strut of the instant invention as shown in FIG.  1  and taken along line A—A (not to scale). 
     FIG. 2A is an axial cross sectional view of a submerged hull and supporting strut of the instant invention as shown in FIG.  1  and taken along line A—A, showing an alternative embodiment using a propeller. 
     FIG. 3 is a cross sectional view of the rotary propulsive means shown in FIG.  2  and taken along line B—B illustrating three embodiments of a work translating means to cause rotation of said rotary propulsive means (not to scale). 
     FIG. 4 is a rear-side perspective view of a submerged hull of the instant invention. 
     FIG. 5 is a side perspective view of an alternative embodiment of a submerged hull of the instant invention. 
     FIG. 6 is a side perspective view of another alternative embodiment of a submerged of the instant invention. 
     FIG. 7 is a side perspective view of yet another alternative embodiment of a submerged hull of the instant invention. 
    
    
     DETAILED DESCRIPTION 
     As shown in FIGS. 1 and 2, the SWAMH vessel  1  of the instant invention comprises a surface platform or surface hull  10  which in use may be situated above the design water line of the vessel and at some height above a body of water  1000 , at least two submerged hulls  20  each respectively housing therein a rotary propulsive means  24  and each respectively being fixedly connected to the surface hull  10  by a supporting strut  22 . An engine or a plurality of engines  12  is also present on surface hull and may comprise any sort of engine, e.g. internal combustion, electric, brushless DC, linear magnetohydrodynamic and the like, and is connected by a work translating means  30  shown in broken line, said work translating means being capable of converting the work done by the engine into a motivating force for rotating the rotary propulsive means  24  housed within a cylindrical passage  21  of the submerged hulls  20  to move the vessel  1 . Situating of the engine or engines  12  on the surface hull  10  permits easy access by a user for repairs and eliminates the need to provide housing for it/them within the submerged hulls  20 . The multihull construction may also include unpowered craft such as a sailboat or a barge which is towed by a second vessel, wherein the submerged hulls serve the single role of providing buoyancy. 
     As will be appreciated by a practitioner in the art of SWAMH vessels, the geometric configuration of the supporting struts  22  and the positioning of the submerged hulls  20  may be selected to suit the specific characteristics of a desired vessel such that performance features which are susceptible to optimization by such selection are in fact optimized. It is recognized that previous inventions have addressed the extent to which such optimizations by their nature occur independently from the teachings of the instant invention. In particular, the teachings of U.S. Pat. No. 4,802,427 to Biegel, which indicates the importance of carefully positioning submerged hulls relative to the surface hull in order to dampen roll and yaw movements, are noted and incorporated herein by reference as are the strut arrangements taught in U.S. Pat. No. 5,313,906 to Zapka. It should be further appreciated that the submerged hulls may comprise a single, or main, submerged hull which may be stabilized by ancillary submerged hulls or pontoons. 
     Looking now to FIGS. 1 and 2, the submerged hulls  20  comprise an outer wall  25  and an inner wall  26  separated by and containing a buoyant core material  28  and surrounding a cylindrical passage  21 . Preferred materials for the outer and inner walls  25 ,  26  are hardened plastics, fibreglass and composite materials which demonstrate resistance to degradation brought on by the continual contact of water sources. It is appreciated that a “topskin” of some useful material, such as a polymeric woven, nonwoven or reinforced web, may be applied to all or to a portion of the surface of the hulls in order to enhance characteristics including providing decorative or informative indicia, increasing degradation resistance, stiffening the hulls with respect to bending forces and decreasing surface friction. Alternatively, the surfaces of the outer and inner walls  25 ,  26  may be directly modified by chemical or mechanical means to effect these goals. The buoyant core material  28  is preferably a gas, especially a gas which is less dense than air such as hydrogen or helium, or a foamed polymer material entraining a gas within the foam structure. Moreover, where hydrogen or helium serve as buoyant materials, the outer and inner walls  25 , 26  may require barrier liners to prevent seepage of the gas. The volume of buoyant core material  28  contained between the outer and inner walls  25 ,  26  may be provided through direct calculative means to cause a displacement and concomitant buoyancy which is required by a particular vessel. For example, a thinner hull may be desirable where an increase in travel speed of the vessel is the primary goal, whereas different configuration/thickness of the hull may required to provide greater vessel payloads. Struts  22  may be constructed from stiff, durable material such as corrosion resistant alloys, plastics, fibreglass and the like. Construction methods may require the separate manufacture of the submerged hulls  20  and struts  22  which are thereafter joined to one another by suitable means such as welding, bonding, joining by screws and the like. Similarly, the struts are attached to the surface hull  10  by permanent joining means. Alternatively, the struts  22  may be formed integrally with both or either of said surface hull  10  and submerged hulls  20 . 
     The submerged hulls  20  are shown to be cylinders surrounding a cylindrical passage  21  with the inner walls  26  being open to the passage of water at ends  29  at either a fore  45  or aft  46  portion of the hull. The practitioner may apply hydrodynamic principles to the surface topology of the hulls and rotary propulsive means to produce performance-improving configurations, variants of which will be discussed in alternative embodiments of the present invention. A rotary propulsive means  24  is housed and is rotatably secured within each of the submerged hulls  20  and preferably comprises a helical screw extending the length of the hull although a propeller  24  could also be used. Turning of the rotary propulsive means in either rotary direction can effect either a forward or a backward draw to cause movement of the vessel. Because the submerged hulls  20  need not house an engine, the entire cylindrical spaces encompassed by them are available to house propelling means, viz. the rotary propulsive means  24 . Consequently, efficient use of the volume occupied by the submerged hulls  20  may be made. Moreover, the relative efficiency of the helical screw over that of simple propellers such as that shown in U.S. Pat. No. 5,313,906 to Zapka, provides the SWAMH of the present invention with an advantageous propulsion means. The entire body of the submerged hulls  20  function to channel water through the cylindrical space  21  containing the rotary propulsive means  24  so that the rotary motion of a helical screw or propeller is translated into a thrust guided in one primary direction by the submerged hull. In contrast, the rotation of the propellers shown by Zapka directs the flow of water not only in a desired thrusting direction, but also in movement directed outwardly from the plane of rotation along lines which are perpendicular to the desired direction of thrust. 
     Looking now at FIG. 4, fins  40  may be mounted to the outer walls  25  of the submerged hulls  20  to provide stabilization and lift to the moving vessel. Moreover, the submerged hulls may be provided with a pivotably secured fin  41 , the pivoting of which can create lift to effect turning of the vessel. As a further steering aid, rudders  42  may be pivotably mounted to the aft end  46  of the submerged hulls  20 . 
     Viewing FIGS. 1 and 3, it is seen that an engine  12  may be connected to the rotary propulsive means  24  through the struts  22  by a work translating means  30  which may constitute a drive having a belt  130  a geared drive shaft  230  or a chain  330  all of which are well-known mechanisms for work translating the work of an engine into rotary movement. It is required, therefore, that the struts  22  have a hollowed section  31  through which a respective belt  130 , drive shaft  230  or chain  330  may be housed and permitted movement. The belt drive may be moved by frictional contact with an engine-driven roller  133 , such movement being directed to the rotary propulsive means  24  which is also rotated by frictional contact with the belt  130 . The belt  130  may be secured in its movement path by the use of guide rollers  132  which guide the belt and prevent slippage thereof. The chain  330  articulates a translation similar to that of the belt  130 , having numerous connected links  332  which may be engaged by individual cogs  334  of an engine-driven cogwheel  333 . Ancillary cogwheels  335  secure the chain in a manner analogous to that of the guide rollers. The rotary propulsive means  24  is provided with cogs  336  which also engage the links  332  of the chain  330 ; thus, the propulsive means itself is a cogwheel. A drive shaft  230  rotated by the engine  12  may have a cogwheel  233  through which motion is transmitted to the is transmitted to the rotary means  24  through cogs  236  provided thereon 
     As shown in FIGS. 5 and 6, the fore end  45  of the submerged hulls  20  may be provided with slots  501  or comprise a screen front  502  for an increased draw of crosscurrent waters  1001  through the rotary propulsive means. 
     FIG. 7 illustrates a modified submerged hull  20  having a tapered profile gradually diminishing in diameter from the fore end  45  to the aft end  46  which has the general effect of boosting the thrust of the rotary propulsive means  24 . As shown, the submerged hull has a scalloped front at the fore end  45  to provide an increased draw of cross currents  1001  as with the preceding two embodiments. The contour of the tapered submerged hull may be incorporated into all of the previously-described embodiments without specifically requiring the scalloped front at the fore end. The practitioner may optimize the performance of the tapered submerged hull for a specific vessel through direct experimentation or through calculative methods. 
     While particular embodiments of the invention have been described, it will be understood, of course, that the invention is not limited thereto, and that many obvious modifications and variations can be made, and that such modifications and variations are intended to fall within the scope of the appended claims.