Abstract:
A shallow water boat is shown that operates well in both shallow water and deep water. A tunnel is provided along a centerline of a flat bottom, which tunnel starts near amidships increases in depth and terminates at the aft of the shallow water boat. A top of the tunnel has an S curve therein. A front end of the tunnel connects through a series of angled holes into a plenum via a conduit to atmosphere above the maximum water line of the shallow water boat. During shallow water operation, the motor is raised and the conduit is plugged so water flows through the tunnel to the propeller for the motor. During deep water operation, the motor is lowered and the conduit unplugged so that water does not flow through the tunnel.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates generally to boats and, more specifically, to a boat for alternatively operating in shallow water or at high speeds in deep water. 
   2. Background of the Prior Art 
   Various types of boats, ships or vessels have been used from the earliest recorded history of man. Different type boats have different functions. One boat may be designed for speed and another boat designed for hauling heavy loads. Likewise, boats may be designed for operation in shallow water versus deep water or in the ocean. Some boats are designed for maneuverability and others are designed for holding a straight line. 
   Fishing, whether as sport or as a means of making a living, is very popular throughout the world. While fishing can be performed from the banks, the best fishing is normally performed from boats operated either near the shore or in shallow water of bays or marshes which would normally have fish. To operate in such an environment, the boat should be maneuverable, but have the minimum amount of draft. Typically, some type of flat bottom boat best meets these requirements. However, getting to and from the good fishing areas from a suitable dock or put in location normally requires traveling some distance over open water. The traveling over open waters requires a boat having different characteristics than a boat that operates well in shallow waters. For example, to get to bays and inlets along the coast, it may be necessary to travel over open waters of the ocean or at least extended distances over inland ship channels. If the boat is designed entirely for shallow waters the time and efficiencies for traveling to and from various fishing points can be long and expensive. 
   It has been found that some type of hybrid between the shallow water boat and the deep water boat is necessary for most ideal conditions. One of the hybrid type boats that has been developed has been a tunnel-hull boat as shown in U.S. Pat. No. 6,125,781 by White. In White&#39;s tunnel-hull boat, a pointed bow is provided to cut through the waves when under way. A relatively flat bottom provides for a minimum draft to keep the motor from having to extend below the bottom of the boat when under way in shallow water. A tunnel is provided in the aft of the boat. The tunnel is straight and enlarging from the amidship to the aft of the boat. The tunnel draws water up to the propeller of the outboard motor when the boat is underway in shallow water as shown in White. 
   Further, White shows aeration with apertures to provide air at the beginning of the tunnel to reduce friction. However, the design as shown in White still has problems. The motor operates at the same depth in both shallow or deep water. Water is drawn up the tunnel when the boat is underway whether in shallow or deep water. The air being introduced at the entrance of the tunnel simply is used to reduce friction, not to cause separation between the water and the tunnel. The straight and enlarging design of the tunnel also does not induce separation of the water from the tunnel when operating at high speeds in deep water. A boat built in accordance with White never gets total separation between the water and tunnel even when the boat is operating at high speeds in open water. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a shallow water boat that will operate efficiently in deep water. 
   It is another object of the present invention to provide a shallow water boat that is maneuverable in shallow water, yet handles well in deep and open water. 
   It is yet another object of the present invention to provide a shallow water boat that has a partial tunnel to draw water into the tunnel when operating in shallow water, but not when operating in deep water. 
   It is still another object of the present invention to provide a shallow water boat with a tunnel that starts at approximately the amidship location in the hull with an unplugable openings at the beginning of the tunnel to cause separation between the water and the tunnel when operating in water. 
   It is a further object of the present invention to provide a tunnel in the hull of a flat bottom boat for use in shallow water, which tunnel starts at the amidship location and has a slight S shape top therein. At the beginning of the tunnel, a plenum connects through a series of holes to allow air to be drawn through venturi action into the beginning of the tunnel, which air causes a separation between water moving into the tunnel and the tunnel. The plenum may be connected (or disconnected) to a source of air. When the plenum is connected to a source of air, due to the venturi suction, air is drawn into the tunnel rather than water. This allows the boat to be operated more efficiently in open water, at which point the motor will be lowered down into the water below the bottom of the boat. However, when the plenum is not connected to a source of air, surface tension draws water moving across the bottom of the boat up into the tunnel. Because the tunnel is located in the center of the boat, the aft end of the boat and tunnel terminate in front of the propeller for the motor. The motor may be raised up above the bottom of the boat, but the propeller still strikes the water that is drawn through the tunnel. In this manner, the boat can operate and maneuver in very shallow water without the propeller or motor extending below the hull of the boat. 
   It helps to have a proliferation of holes connecting through the hull of the boat from the plenum to the beginning of the tunnel so that a complete separation of the water from the tunnel is accomplished when operating in deep water. Also, having a slight S curve in the top of tunnel further insures the complete separation of water from the tunnel. This allows the motor and propeller to be lowered down into the water when operating in open water, but raise when operating in shallow water. Also, the tunnel is not a traditional V-shape, but has a flat upper surface with rounded corners. The flat upper surface has the slight S shape to (1.) insure complete separation of water from the tunnel when connected to a source of air, but (2.) stay attached in laminar flow fashion when not connected to a source of air. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of a shallow draft boat operating in shallow water utilizing the present invention. 
       FIG. 2  is a top view of  FIG. 1 , but with the deck and seating removed. 
       FIG. 3  is a cross-sectional view of  FIG. 2  along section lines  3 - 3 . 
       FIG. 4A  is a partial longitudinal sectional view of a boat utilizing the present invention and operating in deep water, but the deck removed. 
       FIG. 4B  is a cross-sectional view of  FIG. 4A  along section lines  4 B- 4 B. 
       FIG. 5A  is a partial longitudinal section view of a boat utilizing the present invention setting still in deep water, but with the deck removed. 
       FIG. 5B  is a cross-sectional view of  FIG. 5A  along section lines  5 B. 
       FIG. 6A  is a partial longitudinal section view of a boat with the present invention being operated in shallow water, but with the deck removed. 
       FIG. 6B  is a cross-sectional view of  FIG. 6A  along section lines  6 B- 6 B. 
       FIG. 7  is a partial perspective view with the deck partially cut away to show the shape of the tunnel and plenum. 
       FIG. 8  is a top perspective view showing the shape of the tunnel and plenum, but with the deck removed. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1  of the drawings, a shallow draft boat  10  is shown in shallow water  12  that has a water line WL as the boat moves forward in the direction indicated by the arrow. The shallow draft boat  10  has the helm  14  mounted at approximately amidship  16  on the deck (not shown) of the shallow draft boat  10 . Seating  18  is also provided on the deck (not shown) of the shallow draft boat  10 . 
   In the view as shown in  FIG. 1 , the outboard motor  20  is in a raised position so that the lower portion  22  of the outboard motor  20  is approximately level with the bottom  24  of the hull  26  of the shallow draft boat  10 . As the shallow draft boat  10  moves forward, a ridge  28  of water follows a tunnel  30  in a matter described hereinbelow to strike the propeller  32  of the outboard motor  20 . The spinning of the propeller  32  in the ridge  28  of the shallow water  12  provides the forward motion for the shallow draft boat  10 . 
   Referring now to  FIGS. 2 and 3  in combination, the shallow draft boat  10  is shown with the deck removed as well as the seating  18 . The helm  14  remains in place for illustration purposes only. Rising out of the bottom  24  of the hull  26  is the tunnel  30 . The forward end  34  of the tunnel  30  is enclosed in a plenum  36 . The plenum  36  forms an air space  38  over the forward end  34  of the tunnel  30 . The air space  38  is connected to the atmosphere by vertical conduit  40 . By removing the stopper  42  from the vertical conduit  40 , direct access to the atmosphere is provided to air space  38 . 
   Below the plenum  36  in the forward end  34  of tunnel  30  is a proliferation of angled holes extended through the bottom  24  of the hull  26 . Motor  20  is mounted on the transom  46  of the shallow draft boat  10 . 
   Assume the shallow draft boat  10  is in deep water  48  and traveling at a good speed such as fishermen do when traveling to or from a fishing location. The outboard motor  20  will be lowered on the transom  46  so that the lower portion  22  and propeller  32  extend well below the bottom  24  of the hull  26  of the shallow draft boat  10  into deep water  48  (see  FIGS. 4A and 4B ). As the shallow draft boat  10  moves in the direction indicated by the arrow in  FIG. 4A , the water line WL in the deep water  48  is as indicated with no water being drawn in to the tunnel  30 . The reason no water is drawn into the tunnel  30  is because the stopper  42  has been removed from the vertical conduit  40  which allows air to flow into the air space  38  created by the plenum  36  because of the proliferation of angle holes  44  that are directed towards the aft of the shallow draft boat  10 . As the deep water  48  moves across the angle holes  44  venturi action is created to suck air out of the air space  38  and through the vertical conduit  40 . The air being drawn in through the angled holes  44  into tunnel  30  causes the deep water  48  to separate from the top  50  of the tunnel  30  by relieving the surface tension therebetween. The stopper  42  can be replaced by any type control valve the boat owner may desire including a fully automated electrical control valve. 
   The top  50  of the tunnel  30  is generally flat except for a slight S curve contained therein as can be seen  FIG. 4A . When the stopper  42  is removed, the S curve further aids in breaking the surface tension between the top  50  of the tunnel  30  and the deep water  48 . By the combination of the S curve in the top  50  and the drawing of air through the venturis created by the angled holes  44 , deep water  48  is not drawn into the tunnel  30 . By not drawing deep water  48  into the tunnel  30 , the laminar flow is broken and surface tension is eliminated in the tunnel  30 . Therefore, the shallow draft boat  10  will operate more efficiently in deep water  48 . This is particularly desirable for fisherman traveling to and from their put in point or dock to their fishing location. Hence, it will require less fuel and time to get to, or return from, a fishing location which is typically in shallow water that may be found in bays, bayous, marshes, coves, inlets, or shallow flats. Also favorite fishing locations may include reefs, sand bars or sunken ships. When traveling in deep water at a good speed, the shallow draft boat  10  will plane with the water line WL as shown in  FIGS. 4A and 4B . 
   When the shallow draft boat  10  is fully loaded and sitting still in the water with the stopper  42  of the vertical conduit  40  is removed, it is important that the vertical conduit  40  extend above the water line WL. Referring to  FIGS. 5A and 5B  in combination, the shallow draft boat  10  is shown still in the water  52 . Water  52  may either be shallow water or deep water. The water line WL rises on the hull  26  of the shallow water boat  10  as shown. If the stopper  42  is removed from the vertical conduit  40 , water  52  will rise through the angled holes  42 , the air space  38  of plenum  36  into the vertical conduit  40 . In the view as shown in  FIG. 5A , the outboard motor  20  is in the lowered position with the lowered portion  22  and propeller  32  extending below the bottom  24  of the hull  26  as if the shallow draft boat  10  is in deep water. However, the outboard motor  20  could be in the raised position and the shallow draft boat  10  could be in shallow water. 
   When the shallow draft boat  10  is operated in shallow water  12  and is traveling in the direction indicated in the arrow in  FIG. 6A ,  FIGS. 6A and 6B  give a good illustration as to what occurs. The hull  26  barely extends below the water line WL of the shallow water  12  with the bottom  24  barely extending below the water line WL. The outboard motor  20  is raised on the transom  46  so that the lower portion  22  is approximately level with the bottom  24  of the shallow draft boat  10 . As the shallow draft boat  10  moves forward, the ridge  28  of shallow water  12  flows through the tunnel  30  and strikes the propeller  32 . Air is prevented from being drawn into the angled holes  44 , air space  38  and vertical conduit  40  by the placing of the stopper  42  into the end of the vertical conduit  40 . As the shallow water  12  flows across the forward end  34  of the tunnel  30 , the venturi action on the angled holes  44  cannot draw air because the stopper  42  is in place. This prevents breaking the surface tension and the separation of the shallow water  12  from the top  50  of the tunnel  30 . Hence, the shallow water  12  flows upward through the tunnel  30  foiming a ridge  28  of shallow water  12  that strikes the propeller  32 . Because the lower portion  22  and propeller  32  of the outboard motor  20  is above the bottom  24  of the shallow draft boat  10 , there is no danger of the outboard motor  20  striking solid items below the draft of the shallow draft boat  10 . The surface tension between the shallow water  12  and the top  50  of the tunnel  30  will continue to draw the shallow water  12  therethrough to form the ridge  28 . 
   Referring now to  FIG. 7 , a partial perspective view of the shallow draft boat  10  is shown. The deck  54  is cut away to show an upper perspective view of the tunnel  30  with the plenum  36  on the forward end  34  thereof. The transom  46  forms the rear portion of the shallow draft boat  10  and is connected to the bottom  24  of the hull  26 . The vertical conduit  40  extends above the plenum  36  and through the deck  54  so that someone on the deck  54  can remove or replace the stopper  42  into the upper end of the vertical conduit  40 . The use or non-use of the stopper  42  determines if air can be drawn through the angled holes  44  in the forward end  34  of the tunnel  30 . 
     FIG. 8  gives a partial top perspective of the shallow draft boat  10  with the deck  54  removed to illustrate the top surface of the tunnel  30  with the plenum  36 . The outboard motor  20  (not shown) would be mounted on the transom  46  that connects to the rear portion of the bottom  24  of the hull  26 . The plenum  36  covers the forward end  34  of the tunnel  30  and has the vertical conduit  40  extending thereabove. The removable stopper  42  is in the upper end of the vertical conduit  40 . In both  FIGS. 7 and 8 , the slight S curve  56  in the top  50  of the tunnel  30  is illustrated by the shading. Similarly, the forward portion of the slight S curve can be seen in the partial cross-sectional views of  FIGS. 4A ,  5 A, and  6 A. The slight S curve  56  is important because it works with the air being drawn into the venturis caused by water flow over the angled holes  40  to ensure complete separation of the shallow water  12  from the top  50  of the tunnel  30  without doing damage to the ocean floor or the propeller  32 . This allows fishermen to get to and maneuver through, some of the best fishing areas in shallow water without doing damage to the ocean floor or the propeller. However, when in deep water, the fisherman can replace the stopper  42 , lower the outboard motor  20  and travel to or from the put in or take out points at a good rate of speed with a minimum amount of fuel consumption. When stopper  42  is in place the slight S curve  56  aids in laminar flow of water to the top  50  of the tunnel  30 .