Abstract:
A vessel transfer system utilizes a larger, surface effect vessel with a hull and a cargo deck, having a pressurized volume of air under its hull. The larger vessel cargo deck is lowered relative to a water surface in order to receive a smaller vessel. Lowering is achieved by depressurizing the volume of pressurized air under the hull. Movable propulsors on an air cushion vehicle permit efficient operation under way in an outer position, while minimizing the envelope dimensions for stowage in a well deck, providing clearance from bridges, docks, etc. in an inner position. In the outer position, the propellers operate in more uniform inflow conditions, resulting in improved performance and lower noise levels. In addition, the craft can be arranged to use a full width stern ramp resulting in time saved during cargo loading/unloading. The propellers will be less likely to ingest green water in high sea states.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     Priority of U.S. Provisional Patent Application Ser. No. 60/748,449, filed 7 Dec. 2005, incorporated herein by reference, is hereby claimed.  
         [0002]     Priority of U.S. Provisional Patent Application Ser. No. 60/756,951, filed 5 Jan. 2006, incorporated herein by reference, is hereby claimed. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0003]     Not applicable  
       REFERENCE TO A MICROFICHE APPENDIX  
       [0004]     Not applicable  
       BACKGROUND OF THE INVENTION 1. Field of the Invention  
       [0005]     The present invention relates to the deep water transfer of a first, smaller marine or amphibious vessel to a second, larger vessel that is a surface effect or air cushion vessel that travels upon a pressurized volume of air, wherein transfer includes depressurizing of the air cushion under the second vessel so that its cargo deck is lowered to an elevation that is at or near the water surface. Such transfer can optionally include a combination of ballasting and a lowering of pressure (or depressurization) of the volume of air under the second vessel.  
         [0006]     The present invention also relates to an improved air cushion vehicle having a multiple lane loading ramp and deck arrangement with air propulsors that move between inner and outer positions for enabling transfer to a larger vessel (inboard propulsion position) and increased propulsion efficiency (outboard propulsion position).  
         [0007]     2. General Background of the Invention  
         [0008]     In the prior art, transfer of a smaller vessel to and from a larger vessel (or a first vessel to a second vessel) has typically been achieved by ballasting with water. Usually, a larger marine vessel is ballasted until a cargo deck of the larger marine vessel is at an elevation sufficiently low in the water to enable the smaller marine vessel to float on the water surface while traveling to the cargo deck of the larger vessel.  
         [0009]     In general, air cushion vehicles or “ACV&#39;s” (also known as surface effect ships or hovercraft) are known. Examples of such ACV&#39;s are disclosed in the US Patents listed in the following table. The following table also lists some patents that involve transfer of item(s) to or from a surface effect vessel.  
                       TABLE 1                       US Document       Date       Number   Title   (MM/DD/YYYY)                   1,976,046   Waterfoil   10/09/1934       2,405,115   Floating Structure   08/06/1946       3,065,723   Supercavitating Hydrofoils   11/27/1962       3,077,173   Base Ventilated Hydrofoil   02/12/1963       3,141,436   Hydrofoil Assisted Air   07/21/1964           Cushion Boat       3,458,007   Captured Air Bubble (CAB)   07/29/1969           Ground Effect Machine       3,589,058   Toy Ground Effect Vehicle   06/29/1971           With Adjustable Stabilizing           Weight       3,621,932   Gas-Cushion Vehicles   11/23/1971       3,817,479   Helicopter Powered Air   06/18/1974           Cushioned Platform       3,893,538   Ground Effects Vehicle and   07/08/1975           An Air Terminal       3,917,022   Twin Cushion Surface Effect   11/04/1975           Vehicle       3,987,865   Gas-Cushion Vehicle Skirt   10/26/1976       4,469,334   Sealing System For The Air   09/04/1984           Cushion Of An Air-Cushion           Vessel       4,489,667   Surface Effect Ship Seals   12/25/1984       4,506,618   Propeller And Keel   03/26/1985           Arrangement For Surface           Effect Ships       4,535,712   Variable Air Cushion Mode   08/20/1985           Vehicle       4,543,901   Surface Effect Ship Air   10/01/1985           Cushion Seal System       4,646,866   Surface Effect Type, Side   03/03/1987           Keel Vessel Fitted With An           Improved Forward Buoyancy           Cushion Seal Apparatus       4,660,492   Catamaran Air Cushion Water   04/28/1987           Vehicle       4,708,077   Hull Shapes For Surface   11/24/1987           Effect Ship With Side Walls           And Two Modes Of           Operation       4,714,041   Structure of surface effect   12/22/1987           ship with side walls       4,739,719   Movable bow seal air ride   04/26/1988           boat hull       4,767,367   Integrated Combination   08/30/1988           Propeller Drive Shaft           Fairing and Water Intake           Sea Chest Arrangement, For           High Speed Operating Marine           Craft       4,984,754   Heli-Hover Amphibious   01/15/1991           Surface Effect Vehicle       5,651,327   Displacement, Submerged   07/29/1997           Displacement, Air Cushion           Hydrofoil Ferry Boat       5,711,494   Aero-Hydroglider   01/27/1998       5,860,383   Displacement, Submerged   01/19/1999           Displacement, Air Cushion           Hydrofoil Ferry Boat       5,934,215   Stabilized Air Cushioned   08/10/1999           Marine Vehicle       6,293,216   Surface Effect Ship (SES)   09/25/2001           Hull Configuration Having           Improved High Speed           Performance and Handling           Characteristics       6,439,148   Low-Drag, High-Speed Ship   08/27/2002       2002/0164231   Craft for Embarking/Landing   11/07/2002           On Unequipped Shorelines       6,487,981   Air Assisted Landing Craft   12/03/2002       2003/0000440   Air Assisted Landing Craft   01/02/2003       6,526,903   High speed M-shaped boat hull   03/04/2003       6,609,472   Stable efficient air   08/26/2003           lubricated ship       2005/0211150   Variable Hybrid Catamaran   09/29/2005           Air Cushion Ship       2005/0236200   Wrapped-cone fingers for   10/27/2005           skirt systems       7,013,826   Hybrid Catamaran Air Cushion   03/21/2006           Ship                  
 
         [0010]     Incorporated herein by reference are the foregoing and U.S. Pat. Nos. 5 4,767,367; 4,984,754; 6,293,216; and 6,439,148. These incorporated by reference patents relate generally to air cushion vehicles, surface effect ships or hovercraft.  
       BRIEF SUMMARY OF THE INVENTION  
       [0011]     The present invention includes a vessel transfer system which utilizes a larger vessel, that is a surface effect vessel with a hull and a cargo deck, having a pressurized volume of air under its hull. The larger vessel cargo deck is lowered relative to a water surface in order to receive a smaller vessel. Lowering is achieved by depressurizing or lowering the pressure of the volume of pressurized air under the hull. The present invention further relates to the use of movable propulsors on an air cushion vehicle or ACV to permit efficient operation under way in an outer position, while minimizing the envelope dimensions for stowage in a well deck, providing clearance from bridges, docks etc. in an inner position. In the outer position, the propellers operate in more uniform inflow conditions, resulting in improved performance and lower noise levels. In addition, the craft can be arranged to use a full width stem ramp resulting in time saved during cargo loading and unloading, and the propellers will be less likely to ingest green water in high sea states.  
         [0012]     The present invention relates to the use of an air cushion to vary the cargo deck height of a large ship for the purpose of loading and unloading a smaller craft or crafts from the sea, cargo from another ship or cargo from a dock. In all cases, the pressure in the cushion is varied to adjust the elevation of the cargo deck to facilitate cargo transfer. Cushion pressure may be used either alone, or in combination with ballast to achieve the desired cargo deck elevation. Relative to ballast however, pressure variation is much faster, and could be used dynamically to compensate for wave induced motions in addition to the adjustment of steady state deck height.  
         [0013]     The present invention provides a method of transferring a first, smaller marine or amphibious vessel to and from a second, larger vessel in a deep water marine environment. The terminology “deep water” as used herein means that neither vessel is supported upon land or a sea bottom during the transfer. The subject first smaller and second larger vessels and their component parts can be constructed from any high strength, light weight material, including but not limited to, high strength steel, aluminum, titanium, composites, or the like.  
         [0014]     The invention can be scaled to a wide range of sizes. The range of pressures most likely to be used are 50-250 lb./sq.ft. (24.41 to 122.06 gf/cm 2 ), or ⅓psi (23.41 gf/cm 2 ) to 2 psi (140.61 gf/cm 2 ) and typically less than 5.0 psi (351.53 gf/cm 2 ).  
         [0015]     Overall length of the larger vessel could range, for example, from around 500 to 1000 feet (152.40 to 304.80 meters), and overall length of the smaller air cushion vehicle would probably be, for example, about 50 to 150 feet (15.24 to 45.72 meters).  
         [0016]     The present invention provides a method of transporting a first marine vessel upon a second marine vessel in a deep water environment, wherein neither vessel is supported by land or a seabed.  
         [0017]     The method of the present invention includes providing a first marine vessel and a second vessel that is a surface effect vessel. The second vessel (surface effect vessel) provides a hull with a bow and a stem. The hull has a cargo deck and an under deck volume that can be pressurized with air so that the hull is primarily supported with a pressurized volume of air when it is propelled along the water surface. The first and second vessels are transported to a selected locale in the deep water marine environment.  
         [0018]     After reaching the selected locale, the pressure of the volume of air under the hull of the second marine vessel is lowered, so that the hull and cargo deck of the second marine vessel are lowered in elevation relative to the surrounding water surface. Thereafter, the first vessel is transferred to the surrounding water surface of the deep water marine environment from the lowered cargo deck of the second marine vessel.  
         [0019]     For recovery, the second marine vessel assumes a lowered position with its under hull volume of air depressurized. The first vessel then travels on the water surface from the surrounding water surface to the cargo deck of the second vessel. At this time of transfer, the lowered cargo deck of the second vessel can be partially submerged. The lowered cargo deck can be at least in part at the level of the water surface. The second vessel can then transfer the first vessel (now on board) to a selected destination once the volume of air under the hull of the second vessel is pressurized. This procedure can be reversed to off load the first, smaller vessel.  
         [0020]     The present invention also provides an air cushion vehicle (e.g. the first, smaller vessel) having a hull with a hull periphery, bow, stem, port side, starboard side and deck.  
         [0021]     An air based propulsion system is provided for propelling the hull by thrusting into the surrounding air mass.  
         [0022]     The air propulsion system includes one or more air propellers that move in reference to the hull between first and second positions, one position placing the air propeller at least in part outboard of the hull periphery. Hydraulic rams or linear motors are possible mechanisms for pivoting the air propellers between first and second positions.  
         [0023]     The air propellers engage the air during use.  
         [0024]     One of the air propeller positions places the air propeller within the periphery of the hull.  
         [0025]     There are preferably two air propellers, one placed on the port side of the hull, the other placed on the starboard side of the hull.  
         [0026]     The port side air propeller preferably moves between an outer position wherein it is at least partially outboard of the hull periphery on the port side of the hull to an inner position within the hull periphery next to the port side of the hull. Similarly, the starboard side air propeller moves between an outer position wherein it is at least partially outboard of the hull periphery on the starboard side of the hull to a position within the hull periphery and next to the starboard side of the hull.  
         [0027]     Each air propeller thus moves to a position outside the hull periphery for maximum thrust to a position inside the hull periphery for use in loading onto the deck of another vessel or other use wherein a narrowed width is of value. The air propellers are preferably positioned at the stern of the vessel. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0028]     For a further understanding of the nature, objects, and advantages of the present invention, reference should be had to the following detailed description, read in conjunction with the attached drawings which are identified as follows:  
         [0029]      FIG. 1  is a perspective view illustrating the method of the present invention;  
         [0030]      FIG. 2  is an additional perspective view illustrating the method of the present invention;  
         [0031]      FIG. 3  is a partial perspective view of the preferred embodiment of the apparatus of the present invention showing the position of the first and second vessels during a launch or recovery of the first vessel;  
         [0032]      FIG. 4  is a side, elevation view illustrating the method of the present invention and showing a smaller vessel that has been transferred from a surrounding water surface to a larger vessel and wherein the larger vessel is in a lower transfer position that is a displacement mode;  
         [0033]      FIG. 5  is a side, elevation view illustrating the method of the present invention and showing a smaller vessel that has been transferred from a surrounding water surface to a larger vessel and wherein the larger vessel is in a higher position, pressurized, travel mode;  
         [0034]      FIG. 6  is a perspective view of the preferred embodiment of the apparatus of the present invention showing the smaller, first marine vessel;  
         [0035]      FIG. 7  is a perspective view of the preferred embodiment of the apparatus of the present invention showing in more detail, the deck loaded with multiple vehicles occupying multiple (three) lanes;  
         [0036]      FIG. 8  is a front, elevation view of the preferred embodiment of the apparatus of the present invention showing the main propulsors pivoted outward for increased thrust, efficiency and full width stem ramp capability;  
         [0037]      FIG. 9  is a front, elevation view of the preferred embodiment of the apparatus of the present invention showing the main propulsors pivoted inward for well-deck compatibility;  
         [0038]      FIG. 10  is a fragmentary elevation view of the preferred embodiment of the apparatus of the present invention and showing the propulsor fan in an outboard operating position;  
         [0039]      FIG. 11  is a fragmentary elevation view of the preferred embodiment of the apparatus of the present invention and showing the propulsor fan in an inboard loading position;  
         [0040]      FIG. 12  is a fragmentary perspective view of the preferred embodiment of the apparatus of the present invention illustrating a mechanism for moving the propulsor fan in between inboard and outboard positions;  
         [0041]      FIG. 13  is a fragmentary perspective view of the preferred embodiment of the apparatus of the present invention illustrating a mechanism for moving the propulsor fan in between inboard and outboard positions; and  
         [0042]      FIG. 14  is a fragmentary perspective view of the preferred embodiment of the apparatus of the present invention illustrating a mechanism for moving the propulsor fan in between inboard and outboard positions. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0043]      FIGS. 1-5  show generally the preferred method of the present invention and the transfer system of the present invention which is designated generally by the numeral  10 .  
         [0044]     The method of the present invention involves the use of a first, typically smaller marine vessel  11  that is to be transferred to or from the cargo deck  18  of a second, typically larger marine vessel  12 . The second vessel  12  will receive the first marine vessel  11  and transport it to a selected locale. The first, smaller vessel  11  can then be off loaded. Such a transfer enables the two vessels  11 ,  12  to travel with the first vessel  11  resting upon a cargo deck  18  of the second vessel  12 .  
         [0045]     The first vessel  11  can be any vessel that floats and can include for example a hovercraft, an amphibious vessel or any floating vessel that is able to travel upon a surrounding water surface  30  of a surrounding deep water marine environment  29 . As part of the method of the present invention, the first, smaller vessel  11  travels from water surface  30  to the upper surface  19  of cargo deck  18  of second marine vessel  12 .  
         [0046]     In  FIGS. 1 and 2 , the first marine vessel  11  is a smaller marine vessel that provides a continuous inflatable wall that surrounds a pressurized volume of air under the hull of the vehicle. Vessel  11  can also be of the type that has a continuous inflatable skirt or wall  57  that extends around the periphery of the vessel  11 . Such a vessel with continuous inflatable skirt can be seen in U.S. Pat. No. 4,984,754, which is hereby incorporated herein by reference.  
         [0047]     The second marine vessel  12  is preferably an air cushion vehicle, hovercraft or surface effect vessel. Vessel  12  can be the type that has two spaced apart rigid hulls (e.g. catamaran) and that provides sealing members or skirts forward and aft. The second marine vessel  12  provides a hull  13  that can be a single hull or a pair of spaced apart hull members providing a catamaran type hull. Hull  13  has a bow  14  and a stem  15 , a port side  16  and a starboard side  17 .  
         [0048]     In such a catamaran rigid hulled vessel  12 , a pressurized volume of air  28  (see  FIG. 5 ) is trapped under the hull  13 . The pressurized volume of air  28  is trapped in between the two rigid hulls and in between front and rear seals or skirts  21 . Such rigid hull catamaran surface effect vessels can be seen in U.S. Pat. Nos. 3,987,865 and 4,714,041, each hereby incorporated herein by reference. In  FIGS. 3 and 4 , the vessel  12  that is shown is a larger vessel that has spaced apart rigid hulls including a port side hull  22  and a starboard side hull  23 . Flexible seals  21  can be provided fore and aft. A pressurized volume of air  28  (see  FIG. 5 ) can be trapped under hull  13  in between the spaced apart rigid hulls  22 ,  23 , under the cargo deck  18 , in between fore and aft flexible seals  21 , and above the water surface  30 .  
         [0049]     Hull  13  provides a cargo deck  18  having an upper surface  19  that is receptive of first, smaller vessel  11  according to the method of the present invention. The cargo deck  18  can provide an inclined section  20  that is next to or that communicates with the water surface  30 . Inclined section  20  or surface  19  can be positioned near or below water surface  30  when a transfer (see  FIGS. 2 and 4 ) of vessel  11  to cargo deck  18  is to take place.  
         [0050]     In  FIG. 4 , cargo deck  18  can provide an inclined section  20  that is near that part of vessel  12  that will receive vessel  11 . In  FIGS. 3 and 4 , vessel  11  transfers from surrounding deep water marine environment  29  to cargo deck  18  at a position next to stem  15  of hull  13 . However, it should be understood that such a transfer could take place at the bow of vessel  12 , or at another location if desired.  
         [0051]     Hull  13  can provide a superstructure  24 . Hull  13  can be propelled using propellers  25  or jets as examples. In the embodiment shown in  FIGS. 1-4 , a propeller  25  can be provided to each of the hulls  22 ,  23 . Steering is provided with a rudder  26  that is preferably positioned behind each propeller  25 , a rudder  26  is thus mounted on each of the port and starboard hulls  22 ,  23 .  
         [0052]     Gate  31  is an optional feature that is shown in  FIGS. 1-4 . Gate  31  can be a part of cargo deck  18  that pivots to an open position which is shown in  FIGS. 1, 2  and  4 . Gate  31  can pivot to a closed position as indicated schematically by arrow  33  in  FIG. 3 . It should be understood however that gate  31  is an optional feature that can help dampen waves during transfer.  
         [0053]     In  FIGS. 1 and 2 , arrow  32  schematically illustrates the forward movement of first vessel  11  toward cargo deck  18  of second vessel  12 . In  FIGS. 1, 2  and  4 , second vessel  12  is in its lowered or displacement mode, as indicated by the reference line  36  designating the water line relative to the vessel hull  13 . In  FIG. 5 , arrows  34  illustrate schematically the elevation of the hull  12  relative to the water surface  30 . Reference line  27  in  FIG. 5  shows the water line in reference to hull  13  when the hull  13  is on its air cushion  28  for traveling. Arrows  34  show that the upper deck  19  of cargo deck  18  has been elevated a distance indicated by arrows  77  in  FIG. 5 , i.e. the distance between reference lines  27  and  36 .  
         [0054]     In order to transfer the vessel  11  to the cargo deck  18  of the vessel  12 , the vessel  12  simply lowers the pressure of the pressurized volume of air that is contained under its hull  13 . For a hovercraft or surface effect ship such as the vessel  12 , this is accomplished by deactivating the powered fans that create the pressurized cushion of air upon which the vessel  12  travels. When a pressure lowering occurs, the vessel  12  is lowered in the water from a higher position shown in  FIG. 5  (reference line  36 ) to the lower position shown in  FIG. 4  (reference line  27 ).  
         [0055]     In  FIG. 5 , reference line  27  indicates the position of the water line when the vessel  12  is supported by the air cushion. In  FIG. 5 , a pressurized cushion or pressurized volume of air elevates the vessel  12  to the position shown. In  FIGS. 1, 2  and  4 , the pressure of the pressurized volume of air has been reduced so that the vessel  12  lowers in the water. This lowering of vessel  12  places cargo deck  18  upper surface  19  at, near or next to the water surface  30 .  
         [0056]      FIGS. 6-14  show a more detailed view of a suitable first, smaller marine vessel  11 . First vessel  11  provides a hull  41  having bow  42  and stern  43  portions. The hull  41  provides a port side  44  and a starboard side  45 . A hull periphery  46  is shown for purposes of reference when discussing the movement of the air propulsors or propellers  48  between the inner or inboard position of  FIG. 9  and the outer or outboard position of  FIG. 8 .  
         [0057]     A stem ramp  47  is positioned at stern  43 , in between propulsors  48 . Ramp  47  is preferably of a width that enables full width loading of three lanes of vehicles  50  when the propulsors  48  are in the outboard position of  FIGS. 7 and 8 .  
         [0058]     The hull  41  provides a deck area  49  for containing vehicles  50 . As shown in  FIG. 7 , multiple lanes of vehicles  50  are provided so that three vehicles  50  at a time can be loaded to deck area  49  using the three lane stern ramp  47 . A bow ramp  55  is likewise provided for unloading vehicles  50 , three lanes at a time.  
         [0059]     In  FIGS. 8-14 , the movement of air propulsors or propellers  48  is shown between the inner or inboard position  51  ( FIGS. 9 and 11 ) and the outer or outboard position  52  ( FIGS. 8 and 10 ). Each of the propellers  48  is a variable geometry main propulsor  48  that moves to the position of  FIGS. 8 and 10  for enabling more efficiency and the position of  FIGS. 9 and 11  which allows the first vessel  11  to be loaded onto second larger vessel  12  without damage to the propulsors  48 .  
         [0060]     In  FIGS. 8 and 9 , reference numbers  53  and  54  are provided on the port and starboard sides of hull  41 . Vertical reference line  53  extends upwardly from the periphery  46  of hull  41 . Vertical reference line  54  extends upwardly from the inside edge of propulsor  48 . In the position of  FIG. 8 , it can be seen that at least a part of each of propulsors  48  is outboard of hull periphery  46  and thus outboard of reference lines  53  and  54 . When the propulsors  48  are in the position of  FIG. 8 , the distance between them as indicated by arrow  56  is equal to or wider than the width of the multiple (e.g. three) lane stem ramp  47 . In the position of  FIG. 9 , it can be seen that at least a part of each of propulsors  48  is inboard of hull periphery  46  and thus inboard of reference lines  53  and  54 .  
         [0061]     The propulsors  48  in the position of  FIG. 8  do not in any way interfere with the loading of vehicles  50  to deck area  49 , including when loading multiple lanes at a time using the full width of multiple lane stem ramp  47 .  FIGS. 10-14  show in more detail the movable connection between the propeller  48  and hull  41 . In  FIGS. 10 and 11 , a pivotal connection  59  can be used to join propeller  48  to support structure  62  which is connected (for example, bolted or welded) to the vessel hull  41 . A motor such as hydraulic cylinder  60  can be used to rotate propeller  48  relative to ships hull  41  as indicated schematically by the arrow  58  in  FIGS. 9 and 11 . Hydraulic cylinder  60  can thus be connected to support structure  62  with pinned connection  61 . A pinned connection  74  can be used to attach hydraulic cylinder  60  to propeller  48 .  
         [0062]     In  FIGS. 12-14 , alternate methods for driving the propeller blades  66  are illustrated. In  FIG. 12 , motor drive  63  interfaces with propeller shaft  65  using a transmission  64 . Arrow  67  illustrates that transmission  64  rotates with motor drive  63  and with shaft  65  and fan  48 , as the fan  48  moves in an arcuate path as shown by arrow  67 . Similarly, the motor drive  63  in  FIG. 13  interfaces with drive shaft  69  using a transmission  68 . A right angle drive  70  connects shaft  69  to propeller shaft  72  using a gear box  71 .  
         [0063]     In  FIG. 14 , a power generator  73  produces electricity that travels via transmission lines  75  to electric motor  76  which rotates propeller shaft  72  to which blades  66  are attached.  
         [0064]     The following is a list of suitable parts and materials for the various elements of the preferred embodiment of the present invention.  
                                         PARTS LIST            Part Number   Description               10   vessel transfer system       11   first marine vessel       12   second marine vessel       13   hull       14   bow       15   stern       16   port side       17   starboard side       18   cargo deck       19   deck upper surface       20   inclined section of cargo deck       21   flexible seal or skirt       22   port hull       23   starboard hull       24   superstructure       25   propeller       26   rudder       27   reference line       28   pressurized air volume       29   deep water environment       30   water surface       31   gate section of cargo deck       32   arrow (vessel 1 launch/recovery)       33   arrow (gate movement)       34   arrow vessel 2 (on/off cushion)       35   arrows       36   reference line       41   hull       42   bow       43   stern       44   port side       45   starboard side       46   hull periphery       47   stern ramp       48   propulsors       49   deck area       50   vehicle       51   inner position       52   outer position       53   reference line       54   reference line       55   bow ramp       56   arrow, ramp width       57   inflatable skirt       58   arrow       59   pivot       60   hydraulic cylinder       61   pinned connection       62   support structure       63   motor drive       64   transmission       65   propeller shaft       66   propeller blade       67   arrow       68   transmission       69   drive shaft       70   right angle drive       71   gear box       72   propeller shaft       73   power generator       74   pinned connection       75   transmission       76   electric motor                  
 
         [0065]     All measurements disclosed herein are at standard temperature and pressure, at sea level on earth, unless indicated otherwise.  
         [0066]     The forgoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims.