Patent Publication Number: US-6341793-B2

Title: Self-propelled boat launch vehicle

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 09/604,280, now abandoned which was filed Jun. 26, 2000 as a continuation of U.S. patent application Ser. No. 09/395,977 filed Sep. 15, 1999, now U.S. Pat. No. 6,079,729, issued Jun. 27, 2000. 
    
    
     SCOPE OF THE INVENTION 
     The present invention relates to a vehicle for use in transporting, storing and launching boats or other small watercraft, and more particularly to a self-propelled boat launch vehicle. 
     BACKGROUND OF THE INVENTION 
     The use of trailers in the transportation and launching of boats and other small watercraft is well known. Conventional boat trailers consist of a wheel supported metal frame upon which a crib or boat bunk is mounted to support the boat hull. Conventional trailers are provided with a hitch coupling at a front end which permits the trailer to be secured to a vehicle-mounted trailer hitch for transport. In launching a boat, with the hitch coupling secured to a vehicle, the rear end of the trailer is backed down a public or marina ramp until the boat bunk is submerged to a sufficient extent that the boat can be floated clear of the trailer. The empty trailer is then pulled from the lake and must be stored until such time as the boat is to be retrieved for transport elsewhere. 
     In addition to the expense and inconvenience of storage, conventional boat trailers suffer a disadvantage in that the combined weight of the boat and trailer typically necessitates that only larger vehicles, such as pick-up trucks or sport utility vehicles, may be used to transport and launch the boat from the trailer. 
     In addition, if the launch ramp is privately owned, users may be liable to pay launch fees for its use. Public launch ramps are frequently inconveniently located, acquiring that the boat be driven up to tens of miles to and from the boat launch site to its mooring. As a practical matter, when small watercraft and boats are moored at a dock, it often is not possible to safely pilot the watercraft over long distances to a public launch ramp for removal and sheltering during sudden storms. 
     In an effort to overcome at least some of the disadvantages associated with conventional boat trailers, various individuals have proposed boat railway systems which are designed to enable individuals to remove boats from lakes and rivers without the difficulties associated with trailers. Boat railway systems are unsightly, however, and involve the laying of parallel steel railroad rails on sleepers from a user&#39;s boat house a distance into the lake or river. Boats are raised and lowered from the lake by positioning the boat onto a wheeled sled and winching the sled along the rails. Railway systems are quite expensive and may cost thousands of dollars. In addition, if the railways are not removed from northern lakes and rivers each winter, they may be susceptible to ice damage and fouling by sedimentation. Permanent railway systems also require relatively constant water levels and may also be prohibited by building or environmental restrictions, or even bottom or surf conditions. 
     SUMMARY OF THE INVENTION 
     The present invention seeks to overcome at least some of the prior art disadvantages by providing a boat launching vehicle which is adapted to travel over uneven terrain to launch or retrieve a boat. 
     Another object of the invention is to provide a boat launch vehicle which is self-propelled and which may be used to either transport, store and/or launch boats and other small watercraft from a lake, river or other water body (collectively referred to as a lake). 
     A further object of the invention is to provide a self-propelled boat launch trailer which may be moved over sand, logs, rocks or uneven terrain to launch or remove a boat from a body of water. 
     A further object of the invention is to provide a partially submersible boat launch vehicle which provides a raised platform on which a boater may stand or walk when entering or exiting from a boat or small watercraft. 
     Another object of the invention is to provide a vehicle for launching and retrieving boats from lakes, which is adapted to travel over shoreline banks and/or lake beds, without requiring installation of specialized rail systems or permanent lift structures, and which optionally may be left partially submerged on a lake or river bed for a period of several months to function as a seasonal dock. 
     The present invention provides a launch vehicle for boats, jet skis or other small watercraft, and which hereafter are collectively referred to as boats. The launch vehicle includes a partially submersible frame which is movably mounted on wheels. The vehicle frame has a lateral width and longitudinal length selected to enable a boat to be supported thereon. Preferably the wheels are provided with all-terrain type tires which enable the frame to move over rocks and uneven ground or lake beds, without becoming bogged down in sand, muck or lake bed sediments. Although not essential, preferably the launch vehicle tires are of a low pressure design, and are typically inflated to pressures at or below 25 psi, and more preferably at or below 5 psi. Suitable tires would include those for use with ATV&#39;s or Argo™ amphibious vehicles. Optionally, tire-located tracks such as those described in Canadian Patent No. 1,215,735, and which issued Dec. 23, 1986, could be used where increased traction is desired. 
     The frame supports a boat cradle or bunk which is configured to engagingly support the bottom sides of a boat hull thereon during its transportation and storage. A walkway is also coupled to the frame. The walkway is adapted to assume a suitable orientation so as to enable a user to stand or rest thereon. Preferably, the walkway has a lateral width of at least one foot, and most preferably between 1 and 6 feet, and extends substantially the longitudinal length of the boat launch vehicle. If desired, the walkway optionally may be hingely coupled to a remainder of the launch vehicle so as to permit its movement between the generally horizontal orientation when used to support a boater, and an inclined or vertical storage position. When in the horizontal orientation, the walkway assumes a position vertically spaced above the bunk, and at a location selected so as to substantially locate above the surface of the lake when the bunk and lower portion of the frame are sufficiently submerged to enable the boat to be floated free from or positioned over the bunk. 
     The boat launch vehicle is self-propelled with the wheels rotatably driven by an electric AC or DC motor, or by a gasoline powered engine. The motor is mounted at a position vertically above the submersible bunk so as to maintain it in a position above the lake surface while the boat bunk is sufficiently submerged to permit the boat to float free of the vehicle during its launching, docking and retrieval. A drive link(age such as a direct drive, or a continuous loop-type drive including a drive belt or drive chain assembly transmits power from the motor to drive the wheels. Where a belt or chain drive is provided, an adjustable tensioning mechanism is preferably also provided to maintain sufficient tension thereon so as to substantially prevent chain or belt slippage. Most preferably, the drive motor is mounted on top of a vertically extending motor support located at a forward end of the launch vehicle. The motor support is most preferably positioned at an angle between 0 and 60° from the vertical in a direction away from the rear end of the vehicle. The motor support extends upwardly from the frame a distance of between approximately two and five feet, such that the motor is maintained at a position above the water surface adjacent at the shoreline during boat launching. 
     Boats are launched either prow first or essentially the same manner as with conventional boat trailers. To launch or retrieve the boat from the lake, the launch vehicle is moved into a lake so that part of the frame and the boat bunk moved to a sufficient extent to enable the boat to float free of the bunk. When launching the boat, the vehicle is moved into the water so that the bunk submerges and the forward end of the vehicle carrying the motor remains at or immediately adjacent to the shore line. As the vehicle enters the water, the frame partially submerges enabling the boat to float free of the bunk. Because the motor and the walkway are spaced vertically relative to the bunk, they are maintained substantially above the lake surface. As such, once the vehicle is partially submerged in water, the walkway permits the user access from the shore to the boat in a manner of a conventional dock. 
     The launch vehicle advantageously may be moved up onto the shore line daily, protecting the boat and vehicle from wave action, algae and corrosion. To remove the boat, the boat is moved over the submerged portion of the launch vehicle in essentially the same manner as with a conventional trailer, and is tethered in place directly above the bunk. The motor is then activated to drive the launch vehicle together with the boat from the lake. As the vehicle moves from the lake, the boat hull is positioned relative to the bunk and the launch vehicle may be housed for storage with the boat resting on the boat bunk. Alternately, the launch vehicle could be left partially submerged within the lake to act as a seasonal dock which can easily be removed from the lake upon the approach of severe storms and/or each fall to avoid winter ice damage. 
     In a preferred embodiment, the walkway may be mounted on one or more telescoping pipes or supports which permit the vertical adjustment of one or both ends of the walkway to better assume a position generally horizontally above the water surface. The walkway supports could in themselves be supported either entirely by the frame, or alternately adapted for engagement with the underlying lake bed to assist in anchoring or stabilizing the launch vehicle in a partially submerged position. 
     Accordingly, in one aspect the present invention resides in a self-propelled boat launch vehicle for launching or docking a boat in water comprising, 
     a submersible longitudinally elongated frame, said frame being movably supported on each longitudinal side by a pair of low pressure tires inflated to a pressure of 25 psi or less, 
     a submersible boat bunk mounted to said frame for supportably engaging said boat during launching, 
     a drive motor supported at a position spaced vertically above said boat bunk, whereby during launching or docking of said boat, said drive motor is maintained at a position substantially above said waters, 
     a continuous-loop drive member connecting said drive motor and at least one of said wheels, whereby the activation of the drive motor drives said at least one of said wheels to move the boat launch vehicle, and 
     a walkway for supporting a user thereon being coupled to the frame. 
     In another aspect, the present invention resides in a boat launch vehicle for transporting, launching or docking a boat in water comprising, 
     a generally planar frame, 
     a submersible boat bunk mounted to said frame, and configured to engage and support said boat thereon during transport, said boat bunk including a pair of generally parallel and longitudinally extending side rails each extending from a first end to a second end, and wherein said side rails are pivotally coupled to said frame at a pivot so as to permit the second end of each of said rails to be lowered relative to said first end, 
     a pair of low pressure tires movably supporting said frame, each said tire being inflatable to a pressure of 5 psi or less and being coupled to a respective longitudinal side rail of said frame, 
     a drive motor selectively operable to drive said tires, said motor being supported at a position spaced a distance vertically above said boat bunk such that when said boat bunk is submerged during launching or docking of said boat, said drive motor is substantially maintained at a position above said water. 
     In a further aspect, the present invention resides in a self-propelled boat launch vehicle for transporting, launching or docking a boat in water comprising, 
     a partially submersible longitudinally elongated frame, 
     a submersible boat bunk mounted to said frame for supportably engaging said boat during transport or launching, 
     a low pressure tire inflated to a pressure of 25 psi or less rotatably mounted to each side of said frame, 
     a drive motor supported at a position vertically above said boat bunk such that when said boat bunk is submerged sufficiently to enable the boat to float free of the bunk, said drive motor is substantially maintained at a position above said waters, 
     a drive linkage independently connecting said drive motor and said wheels, whereby the activation of the drive motor drives the boat launch vehicle in movement, and 
     a generally planar walkway for supporting a user thereon extending substantially the longitudinal length of the frame, said walkway being coupled to said frame such that when said boat bunk is submerged sufficiently to enable the boat to float free of the bunk, the walkway is maintained in a position substantially above said water. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Reference may now be had to the following detailed description taken together with he accompanying drawings in which: 
     FIG. 1 is a schematic first side view of a self-propelled boat launch vehicle in accordance with a preferred embodiment of the invention, showing a boat positioned thereon for transport; 
     FIG. 2 shows a schematic second side view of the boat launch vehicle of FIG. 1; 
     FIG. 3 shows a schematic plan view of the boat launch vehicle shown in FIG. 2; 
     FIG. 4 shows an enlarged schematic rear end view of the boat launch vehicle of FIG. 2; 
     FIG. 5 shows a schematic side view of the boat launch vehicle shown in FIG. 2 in a partially submerged position and functioning as a seasonal dock; 
     FIG. 6 shows a schematic side view of a boat launch vehicle in accordance with a second embodiment of the invention; 
     FIG. 7 shows a schematic top view of a boat launch vehicle in accordance with a third embodiment of the present invention; 
     FIG. 8 shows a side view of a chain tensioner for use with the boat launch vehicle shown in FIGS. 1,  6  and  7 ; 
     FIG. 9 shows a perspective end view of the chain tensioner of FIG. 8; 
     FIGS. 10 a  and  10   b  illustrate schematically the operation of the chain tensioner of FIGS. 8 and 9; 
     FIG. 11 shows a top view of a modified boat cradle for use with the launch vehicle of FIG. 1; 
     FIG. 12 shows schematically the boat cradle of FIG. 11 mounted to a launch vehicle frame; and 
     FIG. 13 illustrates schematically a boat launch vehicle in accordance with a further aspect of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference may be first had to FIGS. 1 to  4  which show a self-propelled boat launch vehicle  10  used in the transportation, storage, launching and/or docking of a boat  12 , in accordance with a preferred embodiment of the invention. 
     The launch vehicle  10  includes a partially submersible generally planar aluminum or galvanized steel frame  14 . The frame  14  is elongated in a longitudinal direction and has an overall length of up to 8 meters and lateral width of up to 3 meters to enable the boat  12  to be supported or trailered thereon. FIG. 3 shows best the frame  14  as being generally symmetrical about a longitudinal center axis A-A 1 . The frame  14  is formed from a pair of sealed hollow rectangular left and right side rails  16   a , 16   b  which are provided in parallel to each other and joined by a number of longitudinally spaced cross braces  18 . 
     In the embodiment shown, the frame  14  is movably supported on an opposing pair of left and right front wheels  20   a , 20   b  and three opposing, pairs of left and right rear wheels  22   a , 22   b ,  24   a , 24   b  and  26   a , 26   b . Each wheel  20 , 22 , 24 , 26  includes a rubber tire  27 , an axle  28  (FIG.  3 ), a hub  29  mounted to an outboard end of the axle  28 . The rubber tires  27  are selected to enable the vehicle  10  to move over sand or soft and uneven terrain without becoming bogged down. To minimize the buoyancy of the vehicle  10  and provide better weight distribution, the tires  27  are most preferably, wide profile low pressure tires which are inflated to a pressure of 25 psi or less and preferably 5 psi or less, such as those which are used on ATV&#39;s or Argo™ amphibious vehicles. Alternately, the wheels may be weighted with sand, gravel, calcium or other suitable material for increased negative buoyancy. The tires  27  preferably also have a tread diameter of at least about 25 cm and a radial diameter of at least 30 cm, and more preferably between 30 and 60 cm to enable the movement of the vehicle  10  over rocks and uneven terrain. Suitable tires include the Goodyear Runamuk™ 22x10.00-8NHS and the Goodyear Rawhide III 25x12.00-9NHS (inflated to 2.1 psi or 0.67 psi when used with tracks). Each of the wheels  20   a , 22   a , 24   a , 26   a  and  20   b , 22   b , 24   b , 26   b  is rotatably mounted to a respective side rail  16   a ,  16   b  by means of its corresponding axle  28 . The axles  28  extend into the side rail  16   a , 16   b  so as to form a rotary seal therewith to prevent the movement of water into the interior of the side rail  16   a ,  16   b  while the launch vehicle  10  is partially submerged during boat launching and/or docking. A metal pinion  30  (FIG. 3) is mounted to an inboard end of the axle  28  used to mount each of the rear wheels  22   a , 22   b , 24   a , 24   b , 26   a  and  26   b . As will be described hereafter, the pinion  30  is provided on the inboard end of the axles  28  of wheels  22 , 24 , 26  so as to locate within the hollow interior of the side rails  16   a , 16   b . The pinion  30  is directly coupled to the axle  28  and has a radial diameter selected to permit its free rotational movement therewith within the interior of the rails  16   a , 16   b.    
     A boat crib or bunk  32  is secured towards a rear end of the frame  14 . The boat bunk  32  consists of a pair of neoprene covered aluminum rails  34  which are welded to the rearmost cross braces  18 . As seen best in FIGS. 1 and 2, the rails  34  extend a marginal distance above the frame  14  and have a height and a spacing selected to engagedly support the bottom side portions of the boat hull  36  (FIG.  1 ), so that the boat  12  may be trailered thereon without interfering with the rotation of the wheels  20 , 22 , 24 , 26 . In this regard, the bunk rails  34  are provided in parallel and extend preferably less than 40 cm above the frame  14 . The height of the rails  34  is also selected so as to assume a submerged position during boat launching and docking, so as not to interfere with the free movement of the boat  12  onto and off of the boat bunk  32 . The rails  34  are spaced apart from each other so as to maintain the boat  12  in a position mounted on the frame  14  during boat transport while not interfering with the boat propeller (not shown) during boat launching and/or docking. As will be described, with this configuration, when the rear end of the vehicle  10  is submerged into the lake, the boat  12  will float freely above the bunk rails  34 . While FIGS. 1 to  4  illustrate the boat bunk  32  as consisting of a pair of neoprene rails  34 , it is to be appreciated that other boat bunk configurations including rubber or neoprene rollers or carpeted bunk rails could also be used. 
     FIGS. 1 to  3  show best the vehicle  10  as being adapted to be driven in movement by a motor  40  which selectively provides power to each of the left wheels  22   a , 24   a , 26   a  and right wheels  22   b ,  24   b ,  26   b , by means of a clutch assembly  42  and drive linkage  44 . The motor consists of a 12 to 24 horsepower gasoline engine which is mounted on an uppermost end of vertically extending motor supports  46  secured to a forward portion of the frame  14 . The supports  46  are secured to a support base  47  (FIG. 3) which spans between and is joined in each of the side rails  16   a , 16   b . The supports  46  extend upwardly from its base  47  at an angle of between about 0 and 60° from vertical, and more preferably about 30° from vertical in a direction away from the rear end of the launch vehicle  10 . The supports  46  have a length of between 2 and 5 feet, depending upon the overall size of the boat  12  which is to be trailered. The length of the supports  46  is selected to enable the boat bunk  32  to be sufficiently submerged to permit the boat  12  to be floated free from the vehicle  10  during boat launching or docking while maintaining the motor  40  above the water. It is to be appreciated that by positioning the motor  40  on the supports  46 , the lower portion of the frame  14  and boat bunk  32  may be lowered into a lake  76  (FIG. 5) and submerged sufficiently to enable the boat  12  to float free thereof, while maintaining the motor  40  above the water and adjacent to the bank  78  (FIG.  5 ). 
     Each support  46  is formed having hollow interior  48 . As seen best in FIG. 3 the drive linkage  44  consists of left and right drive chains  50   a , 50   b , two independently rotatable left and right drive shafts  52   a , 52   b  and left and right shaft chain drives  54   a , 54   b . The shaft chain drives  54   a , 54   b  extend along the hollow interior  48  of the supports  46  to connect the motor  40  to a respective drive shaft  52   a , 52   b . The left and right drive shafts  52   a , 52   b  are rotatably positioned and sealed within the hollow interior of the support base  47  and extend into the hollow interior of each side rail  16   a ,  16   b , respectively. The drive chains  50   a , 50   b  extend along the interior of the side rails  16   a , 16   b  from the drive shafts  52   a , 52   b  to engage the pinions  30  associated with each rear wheels  22   a , 24   a , 26   a  and  22   b , 24   b , 26   b , respectively. The side rails  16   a ,  16   b  are formed as closed tubes with the result that the drive chains  50   a , 50   b  are sealed from lake water for prolonged life span. 
     The clutch assembly  42  is operable by means of controls  56  to provide forward or reverse power to the chain drives  54   a , 54   b  either together or independently to selectively rotate the rear wheels  22 , 24 , 26  and propel the boat launch vehicle  10  while permitting skid steering. 
     Although not essential, the preferred embodiment of the invention shown in FIGS. 1 and 3 illustrates the launch vehicle  10  as further including a winch  59  mounted adjacent the motor  40  to assist in launching and retrieving the boat  12 , as well as an operator platform  60  and seat  62  upon which a user may rest during the transport and launching of the boat  12 . It is to be appreciated that in a more economical embodiment, the platform  60  and seat  62  may be omitted and the vehicle  10  used with a user operating the controls  56  while walking. 
     FIGS. 2 and 3 show best the boat launch vehicle  10  as further including a walkway  68  secured to the frame  14 . Where longer frames  14  are to be used, the walkway is preferably formed from a number of longitudinally aligned aluminum panel segments  70  and extends substantially the longitudinal length of the boat launch vehicle  10 . The walkway  68  has a lateral width selected to enable a user to comfortably walk thereon when entering and exiting from the boat  12 . In this regard, the walkway has a lateral width of at least one foot and more preferably between about 2 and 6 feet. FIG. 3 illustrates best the walkway  68  in an operative position, extending generally horizontally along one longitudinal side of the vehicle  10 . It is to be appreciated that the walkway  68  is positioned so as to not interfere with the movement of the boat  12  to and from a position over the boat bunk  32 . The walkway is shown best in FIG. 2 as being secured to a number of vertical supports  72 . The walkway  68  is mounted on the supports by hinges  73  (FIG. 4) so as to be movable between a horizontal position which enables the launch vehicle  10  to function as a temporary dock in the manner shown in FIG. 5, and an inclined or vertical orientation (shown in phantom in FIG. 4) when, for example, tile boat  12  is resting on the bunk  32  for transport or storage. The segments  70  are coupled to the support  72  so as to be pivotal about the hinges  73  from the inclined or generally vertical orientation for boat storage and transport, and the horizontal orientation shown in FIG.  3 . 
     FIG. 5 shows the positioning of the boat launch vehicle  10  in a partially submerged orientation resting on the bed  74  of a lake  76 . To transport and launch the boat  12 , the motor  40  is started. The clutch assembly  42  is then used to selectively engage the drive chains  54   a , 54   b  to rotate drive shafts  52   a , 52   b  and chain drives  50   a , 50   b . In forward and reverse movement, chain drives  50   a , 50   b  are operated concurrently in the same direction. To steer the launch vehicle  10 , the chain drives  50   a , 50   b  are operated either independently, while braking the opposing drive to provide skid steering. To launch a boat  12  stored on the boat bunk  32 , the user operates the controls  56  to drive the wheels  22 , 24 , 26  and back the rear end of the frame  12  into the lake  76 . As the vehicle  10  moves into the lake  76 , the wheels  20 , 22 , 24 , 26  submerge and move over the lake bed  74 . The wider ATV-type tires  27  advantageously ensure that the wheels  20 , 22 , 24 , 26  will travel over the lake bed  74  and any debris which has settled thereon, and the vehicle  10  will not become mired in lake bed sediments and the like. The wide tire profiles provide the rear drive wheels  22 , 24 , 26  better traction over the lake bed  74  and softer terrain. As the vehicle moves off the bank  78  and into the lake  76 , the boat bunk  32  is submerged to a position such that the boat  12  may be floated free of the vehicle  10 . 
     With the launch vehicle  10  in the partially submerged configuration, the walkway  68  assumes an orientation substantially above the surface of the lake  76 . The launch vehicle  10  may be used to daily launch and retrieve the boat  12  from the lake  76 , thereby protecting it from wake action, corrosion and algae. Alternately, the walkway allows the vehicle  10  to be left in the partially submerged position shown in FIG. 5 to function as a temporary dock. In particular, the boat  12  may be moored over the boat bunk  32  and access to and from the boat  12  may be achieved via the walkway  68 . Either at the end of each day, upon the onset of severe weather or at the end of the season, the boat  12  is again floated over the neoprene rails  34  and tethered in position. The motor  40  is then activated to drive the launch vehicle  10 , together with the boat  12  from the lake  76  for storage elsewhere. 
     FIG. 5 illustrates the walkway  68  as consisting of a number of planar segments  70  mounted to fixed vertical supports  72 , however, the invention is not so limited. FIG. 6 illustrates a further embodiment of the invention wherein like reference numerals are used to identify like components. In FIG. 6, a single walkway segment  70  is secured to telescoping supports  72  which, depending on the desired configuration, may be extended up to 2 meters above the boat bunk  32 . The telescoping supports  72  advantageously provide the launch vehicle  10  with greater flexibility with respect to its use where the lake bed  74  may slope more dramatically. In particular, where increased lake bed slope is encountered, the vertical supports  72  may be telescopically moved to the extended position shown. The Supports  72  may then be locked in place by inserting pins  80  through a series of aligned holes in the telescoped sections. In the embodiment shown in FIG. 6, the supports  72  are also adapted for telescoping movement downward to engage the lake bed  74 , to assist in anchoring the vehicle  10  as a dock against wave and current action. 
     In FIG. 6, the launch vehicle is adapted for self-propulsion by means of a gas motor  40  operated by a user while walking. As with the embodiment shown in FIG. 1, the motor  40  is mounted upon the support  46  which extends upwardly from the frame  14  at an angle of between about 20° and 40° from vertical. The length of the support  46  is selected to maintain the motor  40  in a position spaced above the water surface and adjacent to the lake bank  78  while the bunk  32  remains submerged. 
     The preferred embodiment of the invention illustrates the launch vehicle  10  as being self-propelled by four pairs of wheels  20 , 22 , 24 , 26 . It is to be appreciated that the wheel configuration is not so limited and more or fewer wheels could be provided. For example, where the launch vehicle  10  is to be used to launch smaller watercraft, the frame  14  may be shortened and the number of driven wheels can be reduced accordingly. 
     The walkway  68  of FIG. 6 consists of a one to two foot wide deck which may, for example, be made from aluminum, galvanized steel, plastic or other suitable material, and which extends longitudinally along the length of one side of the frame  12 . Alternately, if a wider dock is desired, walkways could be provided along both sides of the frame  14  and which are adapted to be either covered with a dock platform or pivoted together into a horizontal position to form a wider combined platform. FIG. 7 shows a plan view of an alternate embodiment of the invention in which like reference numerals are used to identify like components. In FIG. 7, the launch vehicle  10  is provided with left and right walkways  68   a , 68   b  which extend along each longitudinal side of the frame  14 . Once the launch vehicle  10  is moved to the partially submerged position as shown in FIG.  5  and the boat  12  is floated free of the bunk  32 , the launch vehicle  10  may be transformed to a seasonal dock. A number of laterally extending aluminum panels  82  are positioned straddling laterally across the vehicle  10  with each end resting respectively on a walkway  68   a , 68   b . It is to be appreciated that with the use of the panels  82 , the boat  12  would be moored in position either across the rearmost end of the launch vehicle  10 , or along the outboard side of either walkway  68   a , 68   b.    
     Reference may be had to FIGS. 8 and 9 which illustrate a preferred chain tensioner  88  used to maintain the drive chains  54  under the desired tension. The tensioner  88  consists of two pairs of parallel arranged swing arms  90   a , 90   b , two pairs of parallel spaced calming arms  92   a , 92   b  and a threaded central shaft  94 . The pairs of swing arms  90   a  are pivotally coupled at one end to the swing arms  90   b  by a pivot bar  96 . In addition to maintaining the desired spacing between the pairs of swing arms  90   a , 90   b , the pivot bar  96  includes a centrally disposed bore  98  which is sized to permit free rotational movement of the threaded shaft  94  therein while preventing movement of the shaft head  100  therethrough. 
     FIG. 9 shows best the pairs of calming arms  92   a , 92   b  as being pivotally coupled at a respective end to the second other ends of the swing arms  90   a , 90   b , with the desired spacing therebetween being maintained by a nylon pin  102   a , 102   b . As will be described, a nylon bushing on guide  104  is secured about each of the pins  102   a ,  102   b  to facilitate free sliding movement of the drive chain  54  therepast. The opposing end of the ends of each associated pair of calming arms  92   a , 92   b  are pivotally joined to a second centrally disposed pivot bar  106  which, as shown best in FIG. 9, includes a threaded bore  108 . The bore  108  has an internal thread configuration sized to threadedly engage external threads  110  provided along the shaft  94 . A compression spring  112  is further provided axially over the portion of the shaft  94  which locates intermediate the pivot bar  106  and a boss  114  which is spaced towards the pivot bar  96 . 
     It is to be appreciated that with the chain tensioner  88 , the rotation of the shaft  94  results in the selective movement of the pivot bar  106  either towards or away from the pivot bar  96 . As the pivot bar  106  is moved away from the pivot bar  96 , the ends of the calming arms  92  which are coupled to the swing arms  94 , are drawn inwardly supplying the desired degree of chain tension. 
     As seen best in FIGS. 10 a  and  10   b , the chain tensioner  88  is pivotally secured to the frame  14  at a point adjacent the pivot bar  96 . The drive chain  54  is looped through the tensioner  88  in the configuration shown in FIG. 8 so that the guides  104  may be used to apply tensioning pressure against the chain  54 . Optionally, additional guides  114  may be provided along the frame  14  to further assist in chain movement. Because the tensioner  88  pivots about the bar  96  relative to the frame, the chain  54  may be effectively tightened regardless of whether or not the chain is driven in forward or reverse motion. 
     Although the embodiment of the invention illustrated in FIGS. 8 and 9 shows the chain  54  as running against the guides  104 , it is to be appreciated that the invention is not so limited. If desired, rotatable toothed wheels or other bushings or guides could be provided on the pivot pins  102  or elsewhere to a assist in guiding movement of the chain  54  therepast. 
     Although FIG. 1 illustrates the launch vehicle  10  having a boat bunk  32  fixedly secured to the frame  14 , the invention is not so limited. Reference may be had to FIGS. 11 and 12 which illustrate the boat bunk  32  mounted to a tipping cradle  120 . FIG. 12 shows the tipping cradle  120  as being pivotally mounted to the frame  14 , and wherein like reference numerals are used to identify like components. The cradle  120  consists of a jack  126  and a cradle frame  131  which supports the bunk  32 . Although not essential, the tipping cradle frame  131  extends from a forwardmost end  122  a distance rearwardly past the rearwardmost end  124  of the frame  14  (FIG. 12) to rear end  126 . The tipping cradle  120  is pivotally coupled to a respective side rail  16   a ,  16   b  of the frame  14  by associated stainless steel pivot pins  130   a ,  130   b.    
     A jack  132  is provided at the forwardmost end  122  to selectively pivot the cradle  120  about the pins  130   a , 130   b  to raise and lowered the forwardmost end  122 . The jack  132  consists of a hollow tube  136 , and most preferably is located adjacent the support  46 . A jack post  138  is telescopically received with in a bottom open end of the tube  136 . A manual handle  140  or optional power crank (not shown) is used to selectively raise or lower the jack post  138  relative to the tube  136 . The end of the jack post  168  is hingely coupled to the frame  14 . It is to be appreciated, however, that the jack  132  could be mounted in the opposite configuration with the jack tube  136  secured to the launch vehicle frame  14 , and the jack post  134  hingely coupled to the metal frame  131  of the cradle  120 . 
     To selectively tilt the cradle  120 , the jack post  138  may be lowered vertically from the tube  136 . By lowering the post  138  to pivot the cradle frame  131  about the pins  122   a ,  122   b , lowering, the rearward end  126 . This position advantageously perm-its easier launching, and retrieval of the boat on to and off of the cradle  120 . Once the boat is positioned over the cradle, for increased ground clearance at the end  126 , the jack post  138  may be moved into the tube  132 , with the tube  132  moving downwardly thereon. This lowers the forward cost end  122  of the cradle  120  and raises its rearwardmost end  126 . It is to be appreciated that once the cradle frame  131  is in the desired position, the jack  132  secures the frame  131  in place. 
     While the preferred embodiment of the invention illustrates the launch vehicle as having a pair of front wheels  20  which are not driven by the motor  40 , the invention is not so limited. If desired, the drive linkage could extend to one or both of the front wheels  20   a , 20   b.    
     While FIGS. 11 and 12 illustrate a tipping cradle  120  used to assist in the launching of a boat  12 , the invention is not so limited. FIG. 13 illustrates a further embodiment of the invention wherein life reference numerals are used to identify like components. In FIG. 13, the boat bunk  32  itself is secured to a series of pivoting support members  150 . The support members  150  are hingely coupled at one end to the boat bunk  32  by a respective hinge coupling  152  and at their other opposite end, are coupled to the frame  14  by a hinge coupling  154 . Aircraft cable is secured at one end to an upper portion of a first support  150 . The aircraft cable  156  is fed via a pulley  158  to the clutch assembly  42  of the drive motor  40 . 
     The operation of the clutch assembly  42  enables the tensioning of the cable  156  selectively moves the boat bunk  32  in the direction of arrow  160  between the boat supporting position shown and the position shown in phantom in FIG.  13 . This movement advantageously facilitates the launching and retrieval of a boat  12 . 
     While vertical adjustment of the horizontal walkway  68  is preferred as providing the maximum adaptability of the vehicle  10  for differing lake bottom conditions, the invention is not so limited. Similarly, while the preferred embodiment of the invention discloses the walkway  68  as being pivotally movable between a collapsed inclined or generally vertical orientation, and a horizontal operating position, it is to be appreciated that in a more economical embodiment the walkway  68  is permanently mounted in the horizontal orientation. 
     While the detailed description of the preferred embodiments describes the boat launch vehicle as being self-propelled, the launch vehicle  10  could be unpowered for towing by vehicles including by way of non-limiting example, all-terrain vehicles (ATV&#39;s), Argo™ amphibious vehicles, trucks, automobiles, lawn tractors or the like. 
     While the detailed description describes the present invention as a boat launch vehicle, it is to be appreciated that the invention is adapted for use with numerous types of watercraft. In particular, the present invention is adapted not only for use in transporting and launching smaller power boats having a length less than about 35 feet, but also other personal watercraft including Seadoos™, sailboats, paddle boats or the like. 
     Although the detailed description describes and illustrates various preferred embodiments of the invention, the invention is not so limited. Many modifications and variations will now occur to persons skilled in the art. For a definition of the invention, reference may now be had to the appended claims.