Abstract:
The present invention provides a foldable boat comprising a first rigid hull section having a bottom that is substantially V-shaped in transverse section, and a second rigid hull section hinged to the first rigid hull section, wherein an axis of the hinge is longitudinal. The foldable boat may further comprise an inflatable tube generally disposed above said first and second hull sections and extending rearwardly from a bow of the boat along opposite sides of the boat, a third rigid hull section hinged to the first rigid hull section, wherein an axis of the hinge is longitudinal and the third section is mounted on an opposite side of the first section from the second hull section such that the first section forms a center section and the second and third sections respectively form port and starboard sections, the second and third sections respectively forming upper edges of the V-shape. The hinges of the second and third hull sections are designed to permit the second and third hull sections to be folded upward from an unfolded state into a folded state, thereby significantly reducing the storage width of the boat relative to the unfolded state. The second and third sections lay on top of the first section when in the folded state. A latching mechanism is used for locking the second and third hull sections to the first hull section in the unfolded position. The boat is powered by a jet propulsion system integrally mounted in the first hull section.

Description:
CROSS-REFERENCE 
     This application relies on Canadian Application No. 2,274,439, filed Jun. 14, 1999, (including its specification, drawings, and photographs) for priority. That application is hereby incorporated by reference into this application. 
     FIELD OF THE INVENTION 
     The present invention relates to folding semi-rigid inflatable boat. 
     BACKGROUND OF THE INVENTION 
     Amphibious aircraft (i.e. aircraft that are capable of landing and taking off from land or from water) are especially useful for the coast guard&#39;s search-and-rescue (SAR) operations and other types of marine operations. In order to access a sinking or stranded vessel, the coast guard ideally would like to have a boat that can be deployed from such an aircraft. In that way, the coast guard can reach the vessel in distress rapidly by plane and then deploy personnel into a boat launched from the plane for water operations. 
     Several potential solutions exist for transporting boats in aircraft. For example, a boat may be carried externally on the aircraft. The primary shortcoming with this method of carrying a boat is that the boat creates aerodynamic drag and interferes with the desired airflow over the wings and control surfaces. Also, the externally-mounted boat is susceptible to coming loose (which is potentially catastrophic during flight). 
     A second method of transporting a boat is to carry the boat inside the fuselage. This precludes any of the foregoing problems. However, the boats that are transported inside the fuselage are bulky and make it difficult for personnel to embark and disembark on the boat from the plane (see FIG.  1 ). As shown in FIG. 1, a conventional inflatable or semi-rigid boat  2  (one type of which is often referred to as a Zodiac® boat) is too bulky to fit inside the fuselage of a SAR amphibious aircraft  100  without significantly interfering with passenger travel in the cramped cabin. 
     A further problem exists in that conventional rigid boats are bulky and difficult to fit into the confined space available in amphibious aircraft. One potential solution is to use inflatable pontoon boats that are only inflated when needed and can be stored inside the amphibious aircraft in a relatively small space when deflated. Unfortunately, because conventional inflatable boats are flat-bottomed, they become very unstable in choppy water and are at the mercy of side winds, which easily blow them off course. Such instability is especially undesirable in the SAR field where lives may depend on the rescue boat&#39;s ability to quickly maneuver to and from the rescue site. 
     Rigid inflatable boats (RIB) exist having inflatable gunwales and a rigid V-shaped hull. However, even in the deflated state, such boats are extremely bulky and not practical for use in SAR aircraft. U.S. Pat. No. 4,597,355 discloses a RIB having a transversely hinged two part hull. However, because the RIB only folds laterally, the width is not decreased. In aircraft, whose fuselages are much longer than they are wide, reducing the storage width of the boat is essential. This deficiency is not addressed either by the &#39;355 patent specifically or the prior art generally. 
     SUMMARY OF THE INVENTION 
     It is thus an object of the present invention to provide a boat which can be quickly and easily deployed from the relatively confined space of an aircraft or amphibious aircraft fuselage. 
     It is a further object of the present invention to provide a rigid-hulled boat for launching and recovery from inside an aircraft. 
     It is a further object of the present invention to provide such a boat which can be deployed from an amphibious aircraft in rough waters. 
     It is a further object of the present invention to provide such a boat which has an integral jet propulsion unit. 
     The present invention solves the above-identified problems by providing a rigid-hulled, foldable boat comprising a first rigid hull section having a bottom that is substantially V-shaped in transverse section, and a second rigid hull section hinged to the first rigid hull section, wherein an axis of the hinge is substantially parallel to the longitudinal center-line of the boat. 
     The foldable boat may further comprise an inflatable tube generally disposed above said first and second hull sections and extending rearwardly from a bow of the boat along opposite sides of the boat. 
     A third rigid hull section also may be hinged to the first rigid hull section, wherein an axis of the hinge is longitudinal and the third section is mounted on an opposite side of the first section from the second hull section such that the first section forms a center section and the second and third sections respectively form port and starboard sections, the second and third sections forming upper edges of the V-shape. 
     It is a further object of the present invention to provide a construction where the hinges of the second and third hull sections permit the second and third hull sections to be folded upward from an unfolded state into a folded state, thereby significantly reducing the storage width of the boat relative to the unfolded state. 
     Another object of the present invention is to provide a boat where the second and third sections lay on top of the first section when in the folded state. 
     It is still another object of the present invention to provide a latching mechanism for locking the second and third hull sections to the first hull section in the unfolded position. 
     Another object of the present invention is to provide a boat that is powered by a jet propulsion system integrally mounted in the first hull section. 
     Other objects and features of the invention will become apparent by reference to the following description and the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The various embodiments of the present invention is illustrated throughout the figures, in which: 
     FIG. 1 is a rear view of a prior art inflatable or semi-rigid boat illustrating how cramped the confines of the fuselage can be with a boat of that size; 
     FIG. 2 is a side view of a folding boat in operation in accordance with a first embodiment of the present invention; 
     FIG. 3 is a rear view of the first embodiment showing the travel of the sponsons when folding; 
     FIG. 4 is a front perspective view of the first embodiment in its folded configuration; 
     FIG. 5 is a rear view of the boat of first embodiment in its unfolded and uninflated configuration; 
     FIG. 6 is a front view of the first embodiment in its folded configuration; 
     FIG. 7 is a side view of the first embodiment in its folded configuration; 
     FIG. 8 a  is a top plan view of the boat according to the first embodiment; 
     FIG. 8 b  is a side view of the boat according to the first embodiment; 
     FIG. 9 a  is a front view of the boat of the first embodiment in its folded configuration; 
     FIG. 9 b  is a top plan view of the boat of the first embodiment in its folded configuration; 
     FIG. 9 c  is a side view of the boat of the first embodiment in its folded configuration; 
     FIG. 10 is a rear perspective view of the boat in its unfolded and inflated state; 
     FIG. 11 is a rear view of the boat in its unfolded and inflated state; 
     FIG. 12 is a rear view of the boat according to a fourth embodiment of the present invention; 
     FIG.  13 ( a ) is a rear view of the latching mechanism of the first embodiment; 
     FIG.  13 ( b ) shows the motion of the latching mechanism of the first embodiment; 
     FIG.  13 ( c ) shows a sectional view of the latching mechanism; 
     FIG. 14 shows the boat according to the present invention near an amphibious aircraft; 
     FIG. 15 shows a top view of the positioning of the folded boat in an amphibious aircraft; 
     FIG. 16 is a front sectional view of the folding boat of FIG. 1 on its launching rails according to the first embodiment; 
     FIG. 17 is a perspective illustration of the Canadair® CL-415™ amphibious aircraft with which the present invention is contemplated for use; and 
     FIG. 18 is a top view of the boat of the present invention, illustrating one embodiment where a stretcher is positioned thereon. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 2 illustrates a side view of the first embodiment of the present invention in operation. Folding jet boat  10  has a folding V-shaped hull  12  with an inflatable tube or collar  14 . Since the boat  10  is designed to be light (in weight) and to occupy a small storage volume, the preferred embodiment of the boat  10  is designed to carry up to five persons or equivalent cargo (300 kg). If desired, however, the boat can be constructed to be larger than that illustrated. If made larger than the embodiment illustrated throughout the figures, the boat can be designed to accommodate a greater number of passengers and a larger quantity of cargo. 
     As shown in FIGS. 3 through 12, the folding jet boat  10  comprises two outer sponsons  18 , a center main hull  20  equipped with an integral jet propulsion system  16 , and removable fuel tank  22 , which is described in greater detail below. The operator&#39;s station  24  is positioned on the main hull  20  toward the rear of the boat  10  and generally in the center of the boat  10  with respect to the port and starboard sides. 
     The operator&#39;s station  24  includes saddle-type seat  26  (which is also referred to as a “straddle-type” seat in some contexts) and a center handling steering column  28  for improved control and stability. The steering column  28  is foam-padded (like motorcycle handlebars) and has a thumb throttle. The boat operator  25  is seated on a foam covered saddle seat  26 . Four passengers  27  (one of whom is illustrated in FIG. 2) can be seated on the collar  14  (the tube). Grab handles  30  are provided on the tube  14  so that the passengers  27  may stabilize themselves thereon. 
     While the straddle-type seat  26  illustrated in FIG. 8 a  is designed primarily only for the driver  25  of the boat  10 , it is contemplated that the seat  26  could be designed to accommodate a second rider. Alternatively, if desired, the seat  26  could be designed to accommodate more than two riders. In addition, where the boat  10  is designed to hold more passengers and cargo than the embodiment illustrated, more than four passengers may be accommodated on the collar  14 . 
     The main hull  20  and sponsons  18  are made from lightweight long-lasting, impact-resistant materials. For example, the center hull  20  and sponsons  18  may be fabricated from fiberglass such that the boat  10  is light, strong and easy to maintain and repair. The proposed maximum weight of the preferred embodiment of the boat  10  is 600 lb. (without oil and fuel). 
     The sponsons  18  are filled with foam, making the boat  10  difficult to sink in most expected environmental conditions. In fact, in the preferred embodiment, the boat  10  is considered to be unsinkable because of the quantity of foam that can be accommodated in the sponsons  18 . 
     FIGS. 4,  6 ,  7 ,  9   a ,  9   b  and  9   c  illustrate the boat in its folded state. FIGS. 2,  5 ,  8   a ,  8   b ,  10 , and  11  show the boat  10  in its unfolded state. The outer sponsons  18  are hingedly connected to the center hull  20  by hinges  40 . To fold the boat  10  into its folded state from its unfolded state, the sponsons  18  are pivoted upwardly and inwardly over the center hull  20 , as illustrated by the arrow in FIG.  3 . This folding action significantly reduces the volume of the boat  10  such that the boat can be deployed, recovered and stored in a very confined space. In its folded and deflated state, the boat  10  is only 0.81 m (32 inches) wide, as opposed to the unfolded and inflated width of 1.8 m. 
     The hinges  40  will be described with reference to FIGS. 3,  7 , and  13 . Hinge portions  44 ,  46  of the hinges  40  pivot, relative to each other, about pivot pin  42  (see FIG.  13 ). A first hinge portion  44  is attached to the sponson  18  while a second hinge portion  46  is attached to the center hull  20  (see FIG.  7 ). A rotating, over-center locking hook  48  is pivotally mounted to the first hinge portion  44  and may be activated by rotating a torque rod  50  to positively engage the hook  48  with a bar  52  attached to the second hinge portion  46  (see FIG.  13 ). 
     Slots  44   a ,  46   a  are provided in the hinge portions  44 ,  46  to permit the free rotation of the hooks  48 . When engaged, the locking mechanism rigidly connects sponsons  18  to the center hull  20  in the unfolded position so that sponsons  18  remain tightly engaged against the sides of the center hull  20 . In the preferred embodiment, three hinges  40  are used for each connection of a sponson  18  to the center hull  20  (see FIG.  7 ). However, a greater or fewer number of hinges  40  may be employed in alternative embodiments of the boat  10 , as required. 
     The hinges  40  are L-shaped, which places the pivoting point above the center hull  20  slightly inward from the contact point between sponson  18  and center hull  20 . In the folded position, the sponsons  18  rotate both upward and inward to a folded state in which the sponsons  18  are directly above one side of center hull  20 . 
     The folding mechanism will now be described with reference to FIGS. 7 and 13. Because of the effect of gravity thereon, a great deal of rotational force is required to rotate the sponsons  18  upward from their unfolded state. Accordingly, to assist in rotating the sponsons  18  into their folded state, a lifting lever  60  is pivotally mounted to the first hinge portion  44  of the center hinge  40   a  on each side of center hull  20  at pivot point  60   d . The lifting lever  60  has a handle portion  60   a  and a leverage portion  60   b , which slides along lifting brace  62 . Lifting brace  62  has a curved shape and is mounted to second hinge portion  46 . As shown in FIG. 13 c , as handle portion  60   a  is rotated clockwise (direction of the arrow), leverage portion  60   b  pushes against lifting brace  62 , transfers that lifting force to first hinge portion  44 , and lifts and rotates sponson  18 . Lifting lever  60  can be operated manually because of the mechanical advantage created. An unfolding mechanism is not required because the boat  10  unfolds under its own weight (due to gravity). 
     In the manually-operated embodiment, there are two torque rods (not shown), one in each of the outer hulls. These rods are rotated manually in opposite directions to one another. This action rotates and engages the locking hooks  48  into the center hull hinge  40 . These locking hooks  48  rotate around their longitudinal axes. 
     In a second embodiment of the present invention, the torque rods  50 , which lock the hooks  48  into the locked position, are replaced by push-pull rods (not shown) that accomplish the same result of locking and unlocking the hooks  48 . The push-pull rods will push or pull the locking hooks  48 . In this embodiment, the locking hooks  48  will be repositioned and will rotate around their new vertical axes. In addition, it is contemplated in this second embodiment that the locking mechanism will be located outside of the outer hulls. 
     In a third embodiment of the present invention, the manually-operated hand lever can be replaced by either an electric winch or a hydraulic pump with a cylinder to fold the boat  10 . Where an electric winch or hydraulic pump are incorporated into the design as the primary folding mover, a manually operated mechanical hand crank is contemplated as a back-up. 
     Hole  60   c  is provided at the top of lifting lever  60  for attachment to the electric winch or hydraulic pump (not shown). A cable from the electric winch can be attached to hole  60   c  so that the folding process may be done automatically, thereby simplifying the recovery and consolidation of the boat  10 . Similarly, where a hydraulic pump is contemplated to assist in folding the boat, the push-pull rods connected to the pistons may be attached to holes  60   c . Whichever folding mover is used to actuate the folding mechanism, the operator simply unlocks the sponsons&#39; hinges  40  and activates hydraulic pump(s) or electric actuator(s) which cause the sponsons  18  to pivot and fold over top of the center hull  20 . 
     The inflatable, multi-chambered collar  14  increases flotation and stability of the boat  10  while improving boat and passenger protection. As shown in FIG. 16, in the preferred embodiment of the present invention, the inflation of the collar  14  is achieved with an air tank/hose  102  equipped with a 3 psi regulator located onboard an amphibious aircraft  100 . When incorporated into the present invention, the single hose  102  can include a quick-connect/disconnect fixture, as would be understood by those skilled in the art. 
     Deflation of the boat  10  is achieved by opening large bleed valves  105  so that the deflation can be accomplished quickly and the recovery time kept to a minimum. An electric vacuum system provided in the aircraft  100  also can be used to decrease deflation time and simplify operation. 
     A minimum of three chambers  110 ,  112 ,  114  (located at the starboard, port, and fore sides of the boat  10 ) are incorporated into the tube  14  in the preferred embodiment of the present invention. Alternatively, a smaller or greater number of chambers may be incorporated into the tube  14 . In the preferred embodiment, the boat  10  can carry a full load at 10 knots with only two of the three chambers in the tube  14  inflated. 
     In the preferred embodiment, an electric or motor driven air pump (not shown) with a regulator is also located on the boat  10  for self-inflation of the tube  14 , when required. Alternatively, a pressurized gas cylinder may be substituted for the air pump to inflate the tube  14 . 
     The boat  10  also includes provisions for transporting a stretcher  116  and for mounting the stretcher  116  with straps  118  across the bow of boat  10  for medical evacuation. Four rubber fitting  120  are positioned at the top of the inflatable tube  14 . The rubber fittings  120  may be bonded to the inflatable tube  14  or they may be attached in any other suitable manner that would be known to those skilled in the art. The four rubber fittings  120  cradle the four ends of the stretcher  116  placed thereon. In the preferred embodiment, four nylon straps  118  secure the stretcher  116  to the rubber fittings  120 . Alternatively, a greater or fewer number of rubber fittings  120  may be employed to secure the stretcher  116  to the boat  10 . In addition, while the four fittings  120  are preferably rubber, any suitable alternative material may be used. Also, the securing straps  118  may be substituted for any other type of securing device, strap, or mechanism as would be understood by those skilled in the art. 
     Should the boat  10  tip over, a self-righting system also can be employed to rotate the boat to an upright position. To re-orient the boat  10  in an upright position, this system deflates one of the side chambers of tube  14 , either manually or automatically. If manually operated, a pull handle can be located at a convenient position under the boat  10  (not shown). If automatic, a gravity activated check valve may be incorporated into the boat  10  to deflate one of the side chambers of the tube  14 . With one of the side chambers deflated, the boat  10  may be more easily righted in the water. 
     In the preferred embodiment of the boat  10 , the engine for the jet propulsion system  16  is a standard twin-stroke, twin cylinder Rotax® 717 (717 cc and 85 hp) (“Rotax” is a registered trademark of Bombardier, Inc., a Canadian corporation). Of course, any suitable motor with sufficient horsepower could be substituted therefor, and the motor may be either a two or four stroke motor. The propulsion system  16  is the standard Bombardier® Formula Jet Pump™ (“Bombardier” and “Formula Jet Pump” are both trademarks of Bombardier, Inc.) with bronze stator vanes that drives an axial flow, single stage impeller. However, as would be understood by those skilled in the art, any suitable propulsion system  16  could be substituted to practice the present invention. 
     The engine is mounted in center hull section  20  midway between the bow and stern. This arrangement enhances stability, maneuverability and speed, which are crucial when operating SAR vessels in rough seas. In the preferred embodiment, the maximum continuous speed of the boat  10  (with the Rotax® 717 engine) is 30 knots in normal sea conditions. In addition, the boat  10  is designed with an endurance of 2 hours at ⅔ wide open throttle (which equates to an approximate speed of 20 knots). 
     The use of a jet propulsion system  16  is preferable over an outboard motor because of the inherent dangers the outboard&#39;s propellers present to anyone nearby in the water. However, an outboard motor or other type of propulsion system also could be used in the present invention. 
     FIG. 12 illustrates a fourth embodiment of the present invention, which is similar to the previous embodiments, except that saddle seat  26  of the first embodiment is replaced by removable saddle seat  140 . In this embodiment, saddle seat  140  contains an integral fuel tank  142  (shown as a dotted outline). Removable saddle seat  140  fits into a positioning slot  144  in the deck of center hull section  20  and is held in place by clamps  146 . Under conditions where it is necessary for the boat  10  to make repeated trips from aircraft  100  (or any other delivery vehicle) to the rescue area, it may be desirable to have the option to refuel the boat  10  very quickly. Accordingly, removable saddle seat  140  and fuel tank  142  can be quickly removed when empty by unclamping clamps  146  and lifting saddle seat  140 . A second saddle seat  140  and fuel tank  142  that is full of fuel can then be easily placed in the slot  144  and clamped in position. This process minimizes interruption of the rescue operation. Fuel tank  142  may be used instead of the fuel tank  22  of the first embodiment. Alternatively, both fuel tanks  142 ,  22  may be used simultaneously to increase the boat&#39;s non-stop running time when endurance is required. 
     Fuel tank  22  may be fixed in the center hull  20  or it may be removable. If removable, fuel tank  22 , when empty, may be replaced during a rescue operation with a full fuel tank  22  from aircraft  100  (or other suitable rescue vehicle). The removability and replaceability of fuel tank  22  can greatly enhance any rescue operation because it can greatly reduce the time need to refuel the boat  10 . 
     Due to the deep V-shaped hull  12 , the ride is smooth and secure even in rough waters (which is where coast guard units often venture). The V-shaped hull  12  also allows greater speed and maneuverability compared to flat-hulled boats. The combination of the deep V-shaped hull  12  and integral propulsion system  16  provides excellent rough water performance with the speed, maneuverability and reliability needed for open-sea operations. 
     Hereinafter, the deployment and retrieval system of the present invention will be described with reference to FIGS. 14 through 16. In the preferred embodiment, the folding boat  10  is designed for rapid deployment and retrieval an amphibious aircraft  100 , such as the Canadair® CL-415™ SAR (Search and Rescue) (“Canadair” and “CL-415” are both trademarks of Bombardier, Inc.), for intervention in maritime operations. (The Canadair® CL-415™ is partially schematically illustrated in FIG.  15  and is illustrated in perspective in FIG. 17.) As shown in FIG. 15, the folding jet boat  10  can be easily stowed aboard the CL-415™ because of its compactness when folded. Due to the constrained width of the fuselage of the aircraft  100 , the longitudinal folding of the boat  10  is especially desirable because it decreases the width of the boat  10  significantly, allowing relatively unimpaired use of the fore/aft passageway of aircraft  100 . The folding jet boat  10  reduces its volume by more than half to facilitate storage and handling. 
     While the boat  10  is designed to be deployed from an amphibious aircraft  100  like the Canadair® CL-415™ SAR, it can also easily be deployed from any other type of aircraft. Alternatively, the boat  10  also can be deployed from a vehicle other than an aircraft. For example, boat  10  can also be deployed from a typical boat trailer in the conventional manner, should it be necessary to deploy the boat  10  from the shore of a body of water. It also could be lowered into the water from a truck using a cradle system similar to the one contemplated for the Canadair® CL-415™ SAR. In addition, the boat  10  could also be deployed from the deck of a larger boat, such as a coast guard cutter. It is also contemplated that the boat  10  could be dropped, in a container, from a helicopter where the boat  10  could be deployed after entry into the water. 
     When deployed the jet boat  10  is 3.8 m (12.5 feet) long, 1.8 m (5.9 feet) wide and 1.02 m high. When folded up, the boat has the same length and height but is only 0.81 m (32 inches) wide. The boat is presently capable of exiting and entering the aircraft  100  through the existing door  101  (1.12 m×1.02 m) or the larger cargo door  104  (1.07 m×1.52 m). 
     In the embodiment illustrated, launch and recovery of the boat  10  is accomplished with ease due to the unique integrated handling system onboard the Canadair® CL-415™. This is a dolly and rail system illustrated in FIGS. 15 and 16. The dolly  106  cradles the boat  10  and the guide rail  107 , embedded in a floor platform structure, ensures proper alignment and facilitates ease of movement. When stored in the aircraft  100 , the dolly  106  and boat  10  will be secured to the floor  108  and cabin sidewall  110 . The floor platform  108  encases the rail assembly  107  so that the rail does not protrude above the platform&#39;s upper surface and to safely dispose of any water entering the cabin. To deploy boat  10 , dolly  106  is rolled along rail assembly  107  from the storage location to the open cargo door  104 . When deploying or recovering, the dolly  106  cradles the stern of boat  10  allowing the bow of boat  10  to be set into the water outside cargo door  102  where it is then unfolded and the tube  14  inflated. 
     Once deployed from aircraft  100 , boat  10  is driven over to the people and/or equipment in need of rescue. The people are then loaded into the boat  10  and the boat  10  is driven back to the safety of the aircraft  100 , where the people and/or equipment are unloaded into the aircraft  100 . This process may be repeated, as necessary. 
     Because each of the hull sections are rigid and sponsons  18  are foam filled, the boat  10  will float even when the tube  14  is partially or completely deflated. This simplifies the deployment of the boat  10  because the boat  10  need not be fully unfolded and inflated until it is already in the water. Foam-filled sponsons  18  also make the boat safer because it is unsinkable. 
     Because of the compactness of the folded state of the boat  10 , several boats  10  may be stacked one on top of another and/or one beside another in a container. The single container can then be taken to the site where use of several boats  10  is required. At the site, the individual boats  10  can then be deployed. This application is especially useful in situations involving the rescue of numerous people such as during large-scale floods. Packaged in a single container, numerous boats  10  can be quickly and easily brought to the flood site and deployed. Similarly, up to six boats  10  (or even more depending on the type of aircraft) may be stored and transported on a single aircraft pallet. 
     While the boat  10  had been described in relation to its usefulness as a rescue vehicle, it should be understood that boat  10  could be employed for many alternative uses. For example, the boat  10  could be used in military operations or it could be used by local police who are required to patrol local waters. Regardless of its ultimate use, the benefit of the boat  10  is that it may be stored in a smaller space than boats with V-shaped hulls that are known in the prior art. 
     The above description and drawings are illustrative only because modifications could be made without departing from the present invention, the scope of which is to be limited only by the following claims.