Patent Publication Number: US-2021188398-A1

Title: Dual Pumping Hydrofoil System And Balanced Dual Linear Drive Propulsion System And Vehicles And Boats Using Same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 62/954,394 to Zabovnik, filed Dec. 27, 2019, which is hereby incorporated by reference in its entirety. This application claims priority to U.S. Provisional Patent Application No. 63/048,656 to Zabovnik, filed Jul. 7, 2020, which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     Field of the Invention 
     The present invention relates to an electric linearly driven power system, and more specifically to a dual pumping hydrofoil system. 
     Description of Related Art 
     A hydrofoil usually consists of a winglike structure mounted on struts below the hull, or across the keels of a catamaran in a variety of boats. As a hydrofoil-equipped watercraft increases in speed, the hydrofoil elements below the hull develop enough lift to raise the hull out of the water, which greatly reduces hull drag. This provides a corresponding increase in speed and fuel efficiency. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view of a linkage based system. 
         FIGS. 2A-C  illustrate positions of a linkage based system. 
         FIG. 3  is a view of a linearly driven linkage based system according to some embodiments of the present invention. 
         FIG. 4  is a view of a linearly driven linkage based system with springs according to some embodiments of the present invention. 
         FIG. 5  is a view of a linearly driven linkage based system with springs according to some embodiments of the present invention. 
         FIG. 6  is a view of a linearly driven linkage based dual system according to some embodiments of the present invention. 
         FIG. 7  is a partial view of a linearly driven system with springs according to some embodiments of the present invention. 
         FIG. 8  is a view of a linearly driven linkage based dual system according to some embodiments of the present invention. 
         FIG. 9  is a view of a linearly driven linkage based dual system according to some embodiments of the present invention. 
         FIG. 10  is a view of a linearly driven linkage based dual system according to some embodiments of the present invention. 
         FIG. 11  is a view of a linearly driven linkage based dual system according to some embodiments of the present invention. 
         FIG. 12  is a partial view of a linearly driven linkage based dual system according to some embodiments of the present invention. 
         FIG. 13  are views of a linearly driven linkage based dual system according to some embodiments of the present invention. 
         FIG. 14  a view of dual linear drives according to some embodiments of the present invention. 
         FIG. 15  a view of a drive system according to some embodiments of the present invention. 
         FIG. 16  is a view of linkage components according to some embodiments of the present invention. 
         FIG. 17  is a view of linkage components according to some embodiments of the present invention. 
         FIG. 18  is a view of linkage components according to some embodiments of the present invention. 
         FIG. 19A-B  are views of linkage components according to some embodiments of the present invention. 
         FIG. 20  is a view of linkage components according to some embodiments of the present invention. 
         FIG. 21  is a view of a linearly driven linkage based dual system according to some embodiments of the present invention. 
         FIG. 22  is a block diagram of a drive system according to some embodiments of the present invention. 
         FIG. 23  is a block diagram of a drive system according to some embodiments of the present invention. 
         FIG. 24  is sketch of a boat with forward and aft hydrofoils. 
         FIG. 25  is a sketch of a boat with a dual rear pumping hydrofoils according to some embodiments of the present invention. 
         FIG. 26  is a sketch illustrating dual rear hydrofoil pumping with flexing foils according to some embodiments of the present invention. 
         FIG. 27  is a sketch illustrating dual rear hydrofoil pumping with flexing foils according to some embodiments of the present invention. 
         FIG. 28  is a sketch illustrating dual rear hydrofoil pumping with pivoting foils according to some embodiments of the present invention. 
         FIG. 29  is a sketch illustrating dual rear hydrofoil pumping with pivoting foils according to some embodiments of the present invention. 
         FIG. 30  is a sketch illustrating a rear hydrofoil with pivoting foils according to some embodiments of the present invention. 
         FIG. 31  is a sketch illustrating a foil pivot with springs according to some embodiments of the present invention. 
         FIG. 32  is a view of a linearly driven linkage based dual hydrofoil system according to some embodiments of the present invention. 
         FIG. 33  are curves illustrating aspects of the speed regime according to some embodiments of the present invention. 
         FIG. 34  is a view of a propulsion system with a tilting mechanism according to some embodiments of the present invention. 
         FIGS. 35A-B  are views of an articulated propulsion system according to some embodiments of the present invention. 
         FIGS. 36A-E  are views of a pivoting hydrofoil blade according to some embodiments of the present invention. 
     
    
    
     SUMMARY OF THE INVENTION 
     A linear drive system adapted for repetitive driving using a linear motor. The drive system may be used to power pumping hydrofoils which drive a boat or ship. Linkages are used to maintain the driven portion in linear motion. A coupled dual drive system in which two driven portions are coupled such that their coupled motions travel at the same velocity in opposed directions. A linear drive system with a return spring portion which is adapted to facilitate linear direction changeover. The coupled linear drive system which may be used as a mechanical power source for drive systems used in transportation and industry. 
     DETAILED DESCRIPTION 
     Various methods of supporting powered drivetrains are used in industry, including bearings and bushings. Friction in these supporting devices, and lubrication of these supporting devices, are important aspects of drivetrain support. However, linkage based systems may be used which reduce or eliminate the need for these common support devices. 
     In some embodiments of the present invention, as seen in  FIG. 1 , a linkage system  10  may include a base structure  11  which supports a first linkage subassembly  13  and a second linkage subassembly  14  whose design is adapted for allowing the linear motion of a drive rod  12 . The linearity of the motion of such a drive rod is discussed further below. The first linkage subassembly  13  consists of two base links  19 ,  23  pivotally coupled to the base structure  11  at their first ends with bearings  15 ,  16 . A joining link  21  is pivotally coupled to the second end of the base links  19 ,  23  with bearings  24 ,  25 . The rod links  20 ,  22  are also pivotally coupled to the second ends of the base links  19 ,  23  and then are pivotally coupled together at a first end of the drive rod  12  with a bearing  5 . The second linkage subassembly  14  is similarly constructed and pivotally coupled to a second end of the drive rod  12  with a bearing  6 . With such a construction, the drive rod will travel along a linear path (vertically in the view of  FIG. 1 ) through a central drive range. 
       FIGS. 2A, 2B, and 2C  are views of the center, top, and bottom of the linear travel path  35  of the drive link attachment  36  of a linkage subassembly. In this illustrative embodiment, and as seen in  FIG. 2A , the linkage subassembly consists of two base links  41 ,  44  which are of the same length and are pivotally coupled to the base structure  33  at their first ends with base bearings  34 ,  35 . A joining link  40  is pivotally coupled to the second end of the base links  41 ,  44  with bearings  38 ,  39 . The rod links  42 ,  43  are of the same length and are also pivotally coupled to the second ends of the base links  41 ,  44  and then are pivotally coupled together with a drive link bearing  36 . As the drive link bearing  36  moves  37  in concert with the various pivoting actions in the linkage subassembly, there will be a motion range  35 , or drive range, in which the drive link bearing  36  will move in a nearly perfectly straight line. The bearings  38 ,  39  of the second end of the base links  41 ,  44  will follow a curvilinear path  45 ,  46 . In this illustrative embodiment, the spacing  62  between the base bearings  34 ,  35  is a distance that is twice the length  61  of the joining link  40 , and the length  63  of the rod links is the length  61  of the joining link multiplied the square root of 2 (multiplied by approx. 1.414). The linear range, or drive range,  35  of the drive link bearing  36  will be in excess of 1.1 times the length of the joining link  40 .  FIG. 2B  illustrates the linkage subassembly with the drive link bearing  36  at the top  31  of the linear range  35 .  FIG. 2C  illustrates the linkage subassembly with the drive link bearing  36  at the bottom  32  of the linear range  35 . 
       FIG. 3  illustrate a single linear drive system  100  according to some embodiments of the present invention. In this illustrative embodiment a first linkage subassembly consists of two base links  119 ,  123  which are of the same length and are pivotally coupled to the base structure  111  at their first ends with base bearings  115 ,  116 . A joining link  121  is pivotally coupled to the second end of the base links  119 ,  123  with bearings  124 ,  125 . The rod links  120 ,  122  are of the same length and are also pivotally coupled to the second ends of the base links  119 ,  123  and then are pivotally coupled together and to a first end of the drive rod  112  with a drive link bearing  105 . Similarly, a second linkage subassembly is pivotally coupled to the second end of the drive rod  112  with a bearing  106 , and to the base structure  111 . The base bearings  115 ,  116 ,  117 ,  118  are in linear relationship. 
     The drive rod  102  is adapted to be driven by the outer linear drive motor portion  101 . The outer linear drive motor portion  101  is fixedly coupled to the base structure  111  and may have an internal cylindrical surface through which the drive rod may be driven, and through which the drive rod may travel. In some aspects, the outer drive portion has a plurality of windings along its linear length. In some aspects, the drive rod has a plurality of magnets and iron rings along its length. The windings of the outer drive portion may be electrically coupled to a power drive system adapted to energize the windings as appropriate to accelerate or drive the drive rod, with its magnets and iron rings, along the drive axis of the linear drive system. As the drive rod  112  moves  107  (vertically as shown in  FIG. 3 ) it travels through a linear path due to its coupling to the linkage subassemblies, as discussed above. Using the linkages which guide the drive rod along a linear path through its central drive range, the drive rod may travel through the outer linear drive motor portion without the need for bearings or bushings between the outer motor portion and the drive rod. The drive rod  112  may have an inner linear drive motor portion  102  adapted to interact with the outer linear drive motor portion  101 . The outer linear drive motor portion  101  may have electric coils which are coupled to an electric power source adapted to provide pulsating DC current. The drive rod  112  may have ring magnets and iron rings. In an exemplary functionality, the drive rod  112  may be driven downward in a power stroke, which may transfer mechanical power to a drive system. As the drive rod  112  is driven by the linear drive motor it travels through a linear path due to its coupling to the linkage subassemblies. A spring  103  may be coupled to a spring bracket  104  which is in turn coupled to the base structure  111 . As it reaches the extent of its power stroke, the spring  103  has worked to slow and stop the drive rod from over extension. The linear motor may then be driven in reverse and the drive rod is helped in its acceleration by the spring force. Similarly, as the drive rod reaches the extent of its reverse stroke, the spring  103  acts in similar fashion at the reverse end as well. In some aspects, the spring begins its retardation of the stroke in the final third of the central drive range. In some aspects, the spring begins its retardation of the stroke in the final fourth of the drive range. In some aspects, the retardation can begin as the drive rod leaves its centered position. 
       FIG. 4  illustrates a second embodiment  150  of a single linear drive system  150  according to some embodiments of the present invention. A spring bracket  155  supports a first spring  123  and a second spring  170 . The spring bracket  155  is coupled to the base structure  111 . The first spring  123  is coupled to a first base link  173  and the second spring  179  is coupled to a second base link  170 . The springs work to help slow, stop, and reverse the drive rod  112  as it changes drive directions. The springs also add efficiency by converting kinetic energy into potential spring then using the potential energy assist the reversal of motion. Using the linkages which guide the drive rod along a linear path through its central drive range, the drive rod may travel through the outer linear drive motor portion without the need for bearings or bushings between the outer motor portion and the drive rod. 
       FIG. 5  illustrates a third embodiment  160  of a single linear drive system  150  according to some embodiments of the present invention. Spring brackets  16 ,  166 ,  167  support a first spring  169  and a second spring  168 . The intermediate spring bracket  166  is coupled to the drive rod  112 , and the first and third spring brackets  165 ,  167  are coupled to the base structure  111 . The springs work to help slow, stop, and reverse the drive rod  112  as it changes drive directions. Using the linkages which guide the drive rod along a linear path through its central drive range, the drive rod may travel through the outer linear drive motor portion without the need for bearings or bushings between the outer motor portion and the drive rod. 
     In some embodiments of the present invention, as seen in  FIG. 6 , a dual linear drive system  200  couples two linear drive systems to a single base structure  211 . The first drive rod  212  moves along a first linear path  214  and the second drive rod  213  moves along a second linear path  215 . The first linear drive system and the second linear drive system share coupling points  215 ,  216 ,  217 ,  218  on the base structure  211 . The compact configuration of the dual linear drive system allows for two drive rods in close proximity. The drive rods  212 ,  213  may be further coupled to apparatus for motive transport, or for other uses. Although not illustrated in this view of  FIG. 6 , the drive rods  212 ,  213 , may each have linear drive motors as discussed above. In this illustrative embodiment, a very compact configuration is achieved. In this illustrative embodiment, although the first linear drive system and the second drive system share coupling position to a single base structure, they nevertheless are free to operate independently.  FIG. 7  illustrates a base structure with a first and second linear motor assembly affixed thereto. The motor external drive portions are fixedly coupled to the base structure. The motor drive rods are able to travel along their drive axes. The linkage assemblies are omitted in  FIG. 7  for clarity. 
     In some embodiments of the present invention, as seen in  FIG. 8 , a linked dual linear drive system  300  couples the motion of the first linear drive system to the second linear drive system. A first linkage subassembly of the first linear drive system consists of a base link  333   a  which is pivotally coupled to the base structure  311  at a first end with a base bearing  316 . A joining link  331   a  is pivotally coupled to the second end of the base link. The rod links  330   a ,  332   a  are of the same length and are also pivotally coupled to the second ends of the base links and then are pivotally coupled together and to a first end of the drive rod  312  with a drive link bearing  340 . The other base link  301 , however, is a coupled base link which couples the motion of the first linear drive system to the second linear drive system. This connection base link  301 , and the second connection base link  302 , couple the up motion of one drive rod to the down motion of the other drive rod. 
     A first linkage subassembly of the second linear drive system consists of a base link  333   b  which is pivotally coupled to the base structure  311  at a first end with a base bearing  316 . A joining link  331   b  is pivotally coupled to the second end of the base link. The rod links  330   b ,  332   b  are of the same length and are also pivotally coupled to the second ends of the base links and then are pivotally coupled together and to a first end of the drive rod  313  with a drive link bearing  342 . The other base link  301 , however, is a coupled base link which couples the motion of the second linear drive system to the first linear drive system 
     Similarly, a second linkage subassembly of the first linear drive system is pivotally coupled to the second end of the drive rod  312  with a bearing  341 , and to the base structure  311 . The base bearings  315 ,  316 ,  317 ,  318  are in linear relationship. A joining link  321   a  is pivotally coupled to the second end of a base link. A joining link  302  couples the second linkage subassembly of the first linear drive system to the second linkage subassembly of the second linear drive system. The second linkage subassembly of the second linear drive system has a coupled joining link  321   b  that is similarly coupled to the second linkage subassembly of the first linear drive system. 
       FIG. 7  illustrates a dual linear drive system shown without the supporting linkages. The outer linear motor drive portions are seen fixedly coupled to the base structure, while the drive rods which have inner linear motor drive portions are able to drive within the outer linear motor drive portions. 
     In the exemplary embodiment of  FIG. 8 , a very compact linked dual drive system  300  allows for linked driving of a power system when configured with linear drive motors as described above.  FIG. 8  illustrates the range motion of the system as the drive rods  312 ,  313  move up and down, as they would under powered driving. In this configuration, although the joining links  331   a ,  331   b ,  321   a ,  321   b  are parallel in the mid-range centered position, as the range is extended the attitudinal positions  325 ,  326  of the adjacent joining links of the first and second linkage subassemblies are not parallel, although close to parallel. Using the linkages which guide the drive rod along a linear path through its central drive range, the drive rod may travel through the outer linear drive motor portion without the need for bearings or bushings between the outer motor portion and the drive rod. 
     Although the drive rods  312 ,  313  are shown in  FIG. 8  as simple rods, they are illustrative of motor drive rods as discussed above. In some aspects, the linked dual drive system of  FIG. 8  would further have motor external drive portions around each of the drive rods. The drive rods may have a plurality of magnets and iron rings, and the motor external drive portions may have a plurality of windings which are coupled to drive electronics. In some aspects, the drive rods may extend past the one or more of the drive link bearings  340 ,  341 ,  342 ,  343  such that the drive rods may power an external device or mechanism. 
     In some embodiments of the present invention, as seen in  FIG. 9 , an optimized linked dual linear drive system  400  couples the motion of the first linear drive system to the second linear drive system in a manner which keeps the position and speeds of the first and second linear drive systems equal and opposite. In this dual linear drive system, the first linear drive system and the second drive systems are coupled using a first middle link  404  and a second middle link  405 . The middle links are coupled to an upper system joining piece  403  and a lower system joining piece  402 . The six pivots associated with the rectangle  420  formed by the base structure pivots of the upper and lower system joining pieces  402 ,  403  and the top and bottom pivots of the middle links  404 ,  405  are in line and as shown. In this system, the motions of the drive rods are coordinated and they will travel at the same speed, but in the opposite directions. Also, the attitudes  425 ,  426  of the joining links are parallel at all positions. 
       FIGS. 10-13  illustrate embodiments of very compact linked dual drive systems according to some embodiments of the present invention.  FIGS. 10 and 11  illustrate the system with its main base structure  1101 , which can be seen as the square-tubes structure residing outside of the linkages.  FIGS. 12 and 13  illustrate the system with the main base structure omitted for clarity, allowing for observation of the very complex linkage structure. In these exemplary views, the linkages are designed to occupy a very significant majority of the internal space while providing clearance for the moving linkage pieces and the drive rods. These large linkages can then take very large loads and provide significant stiffness. 
       FIGS. 14 and 15  illustrate aspects of the linear drive motor according to some embodiments of the present invention. In the illustrative view of  FIG. 14 , the drive rods, which may have a plurality of magnets along their length, are adapted to travel within the exterior motor portion, which may have a plurality of windings. In some aspects, the drive rods extend in order to provide drive power to a device or mechanism. In the illustrative view of  FIG. 15 , the active coils reside within the motor external drive portion, which is fixedly coupled to a base support structure. The drive rod may have a plurality of magnets, which may be alternating magnets, with iron rings in between them, such that electrical impulses sent to the windings in sequence result in the motion of the drive rod along the drive axis. In some aspects, coils of the first and second stators can be connected to the same controller, as the desired motions and speeds are equal and opposite. The coils of the first and second stators would be coupled in reverse order vertically. 
       FIGS. 16-20  illustrate components of the very compact linked dual drive systems according to some embodiments of the present invention. The various components may be combined to form the very compact linked dual drive system of  FIGS. 10-13 . 
     In some embodiments of the present invention, as seen in  FIG. 21 , a linked dual linear drive system  500  couples the motion of the first linear drive system to the second linear drive system in an extended fashion. A first linkage subassembly of the first linear drive system consists of a base link  433   a  which is pivotally coupled to the base structure  411  at a first end with a base bearing  416 . A joining link  431   a  is pivotally coupled to the second end of the base link. The rod links  430   a ,  432   a  are of the same length and are also pivotally coupled to the second ends of the base links and then are pivotally coupled together and to a first end of the drive rod  412  with a drive link bearing  440 . The other base link  401 , however, is a coupled base link which couples the motion of the first linear drive system to the second linear drive system. 
     A first linkage subassembly of the second linear drive system consists of a base link  433   b  which is pivotally coupled to the base structure  411  at a first end with a base bearing. A joining link  431   b  is pivotally coupled to the second end of the base link. The rod links  430   b ,  432   b  are of the same length and are also pivotally coupled to the second ends of the base links and then are pivotally coupled together and to a first end of the drive rod  413  with a drive link bearing  442 . The other base link  401 , however, is a coupled base link which couples the motion of the second linear drive system to the first linear drive system 
     Similarly, a second linkage subassembly of the first linear drive system is pivotally coupled to the second end of the drive rod  412  with a bearing  441 , and to the base structure  411 . The base bearings  415 ,  416 ,  417 ,  418 ,  460  are in linear relationship. A joining link  421   a  is pivotally coupled to the second end of a base link. A joining link  402  couples the second linkage subassembly of the first linear drive system to the second linkage subassembly of the second linear drive system. The second linkage subassembly of the second linear drive system has a coupled joining link. 
     In some aspects, the linear drive systems as described above may be used to drive pumping hydrofoils adapted for propulsion of a boat. In some aspects, the pumping hydrofoils as described herein may be driven by an alternate drive system. 
     Foiling refers to the use of hydrofoils attached to the hull of fast boats, which provides additional lift at planning speeds—often enough to lift the hull completely clear of the water. Lifting the boat clear of the surface can reduce the disturbance of waves, smoothing the ride, but only up to a point. It&#39;s not just about lift though—active foils can also be used to improve stability or handling and in some circumstances, can improve efficiency even without lifting the boat. Foils work in a similar way to aircraft wings. In simple terms, as they move through the water they deflect the flow, which exerts a force on the foil. If that force is upward, the faster they move, the greater the lift. 
     In addition, the pumping of hydrofoils may be seen when observing hydrofoil surfers, who gain propulsion by “pumping” the hydrofoil board. This is done, in the case of a fixed hydrofoil attached below a surfboard, by changing weight forward and then back, driving the foil first down and then up by changing its angle of attack. This pumping delivers forward thrust due to the hydrodynamics of the system. Similarly, there is an opportunity to gain forward thrust on boats by pumping hydrofoils, as discussed below. 
       FIG. 24  illustrates a hydrofoil boat  1000  with a hull  1002  traveling in a forward direction  1001 . The hull  1102  of the boat  1000  is raised above the surface  1003  of the water, as occurs with forward speed coupled to the lift of hydrofoils. A front strut  1006  or struts supports a front hydrofoil  1007  while a rear strut  1004  or struts supports a rear hydrofoil  1005 . In some aspects, the boat  1000  may be driven by a propeller which is located in the area of the rear hydrofoil  1005 . In this illustrative embodiment, the hull  1002  is raised above the water surface  1003  due to the lift of the hydrofoils  1005 ,  1007 . 
     In some embodiments of the present invention, as seen in  FIG. 25 , a hydrofoil boat  1010  is seen with double pumping rear hydrofoils. A front strut  1006  or struts supports a front hydrofoil  1007 , as seen in the regular structure  1000  above. The boat  1010  has two rear hydrofoils which are adapted to pump up and down, and in doing so provide forward propulsion for the boat. A forward rear foil  1014  is coupled to the boat  1010  by a forward rear strut  1013 . An aft rear foil  1012  is coupled to the boat  1010  by an aft rear strut  1011 . A drive unit  1060  is adapted to pump the forward rear foil  1014  and the aft rear foil  1012  up and down. In some aspects, the drive unit  1060  is a linked linear drive system as discussed above. In some aspects, the upper of the two foils (the rear foil  1012  in this illustrative example) will remain above the full travel range of the lower foil (the front foil  1014  in this illustrative example) at all points in its travel range. This may provide a more undisturbed fluid flow for each foil. 
     In some embodiments of the present invention, as seen in  FIGS. 26 and 27 , double pumping airfoils  1012 ,  1014  with flexible blades  1015 ,  1016  coupled to struts  1011 ,  1013 . The struts  1011 ,  1013  are adapted to be driven up and down, and may be up and down in a reciprocating alternating fashion, in that the front strut  1013  goes upward while the rear strut  1011  goes downward, as seen in  FIG. 26 , and vice versa, as seen in  FIG. 27 . The pumping of the struts  1011 ,  1013  results in the flexing of the flexible blades  1015 ,  1016  which then in turn provides forward propulsion of the boat. In some aspects, the hydrofoil boat  1010  is adapted to be propelled as a hydrofoil boat with the hull out of the water, and with the front foil and the dual pumping rear hydrofoils in the water and providing lift to keep the hull out of the water. Additionally, some or all of the forward propulsion of the hydrofoil boat derives from the propulsion resulting from the rearward flow along the flexed flexible blades  1015 ,  1016 . In some aspects, the upper of the two foils (the rear foil  1012  in this illustrative example) will remain above the full travel range of the lower foil (the front foil  1014  in this illustrative example) at all points in its travel range. This may provide a more undisturbed fluid flow for each foil. 
     In some embodiments of the present invention, as seen in  FIGS. 28 and 29 , double pumping airfoils  1040 ,  1041  with pivoting blades  1022 ,  1024  coupled to struts  1021 ,  1023 . The struts  1021 ,  1023  are adapted to be driven up and down, and may be up and down in a reciprocating alternating fashion, in that the front strut  1023  goes upward while the rear strut  1021  goes downward, as seen in  FIG. 28 , and vice versa, as seen in  FIG. 29 . The pumping of the struts  1021 ,  1023  results in the pivoting of the blades  1022 ,  1024  which then in turn provides forward propulsion of the boat. In some aspects, the hydrofoil boat  1010  is adapted to be propelled as a hydrofoil boat with the hull out of the water, and with the front foil and the dual pumping rear hydrofoils in the water and providing lift to keep the hull out of the water. Additionally, some or all of the forward propulsion of the hydrofoil boat derives from the propulsion resulting from the rearward flow along the pivoted flexible blades  1022 ,  1024 . In some aspects, blades may pivot in the range of +/−5 degrees. In some aspects, blades may pivot in the range of +/−10 degrees. In some aspects, blades may pivot in the range of +/−15 degrees. 
     In some embodiments of the present invention, as seen in  FIG. 30 , a pivoting blade  1022  contains a structural element  1028  which extends outward from the strut  1021  out towards the ends of the blade  1022 . The blade  1022  is coupled to the strut  1021  with a pivoting mechanism  1027  which allows for the pivoting of the blade. The pivoting mechanism  1027  may include mechanical stops adapted to constrain the pivoting of the blade at desired limits. In some aspects, blades may pivot in the range of +/−5 degrees. In some aspects, blades may pivot in the range of +/−10 degrees. In some aspects, blades may pivot in the range of +/−15 degrees. 
       FIG. 31  illustrates a pivoting mechanism  1027  which supports the structural element  1028  within a pivoting blade. Bearings  1029 ,  1030  rotatably support the structural element  1028  within the hydrofoil. Compression springs  1031 ,  1032  are adapted to help restore the blade to its neutral position from a deflected position. 
     In some embodiments of the present invention, as seen in  FIG. 32 , a drive system  1100  utilizes a compact linked dual drive system  1101  powering struts  1021 ,  1023  which results in the pivoting of the flexible blades  1022 ,  1024 , which then in turn provides forward propulsion of the boat. In some aspects, the hydrofoil boat  1010  is adapted to be propelled as a hydrofoil boat with the hull out of the water, and with the front foil and the dual pumping rear hydrofoils in the water and providing lift to keep the hull out of the water. Additionally, some or all of the forward propulsion of the hydrofoil boat derives from the propulsion resulting from the rearward flow along the pivoted flexible blades  1022 ,  1024 . 
     As seen in  FIG. 32 , the powering struts  1021 ,  1023  may be physical extensions of drive rods of the linear drive motors of the linked dual drive system as discussed above. In some aspects, it may be desirable to drive the powering struts at a high speed along the length of their drive range.  FIG. 33  illustrates a standard sine wave  900  which may represent the reciprocal speed of a drive blade of a dual bladed hydrofoil system. In contrast, the lower curve illustrates a more desirable time vs. speed curve for hydrofoil drive blades. The quick position changes  901 ,  903  with a flatter top  902  and bottom portions represent a drive system wherein the blades will move quickly when they are indeed moving up and down, with higher accelerations of the struts and hydrofoils. 
     In order to control the height of the boat above the water, or to raise the boat from the water, a variety of approaches may be used individually or in combination. Changing of the speed and/or power of the pumping double hydrofoils will affect this height of the boat above the water. Also, changing the angle of attack of the front hydrofoil will affect this height of the boat above the water. Also, changing the angle of attack of the rear dual pumping hydrofoil blades, which may be implemented with the fore/aft pivoting of the entire drive unit. 
     In some embodiments of the present invention, as seen in  FIG. 34 , a hydrofoil boat  1010  is seen with double pumping rear hydrofoils wherein the entire drive assembly  1060  and the struts  1011 ,  1013  and blades  1012 ,  1014  are adapted to rotate  1702  around a pivot  1701  in order to change the centered blade angle. The pivoting of the entire assembly allows for the entire drive system to maintain its rigidity and alignment while simultaneously allowing the blades to be tilted from a neutral position. In some aspects, as the hydrofoil boat with double pumping rear hydrofoils begins to gain speed the blade angles may be tilted upwards  1702 , as seen in  FIG. 34 , to raise the boat up using the lift of the hydrofoils. This may assist in the raising of the boat from a more traditional in-the-water configuration to a hydrofoil riding configuration. In some aspects, once the boat is lifted out of the water the blade angles may be re-established into a more neutral position. In some aspects, the front foil  1107  is adapted to similarly pivot  1707  to assist in the lifting of the boat. In some aspects, the front foil may include actuation mechanisms or other means to implement the pivoting. 
     In some embodiments of the present invention, as seen in  FIGS. 35A-B , a hydrofoil boat  1010  is seen with double pumping rear hydrofoils wherein the entire drive assembly  1060  and the struts  1011 ,  1013  and blades  1012 ,  1014  are adapted to rotate  1706  around a vertical axis  1705  in order to change the blade thrust direction, in order to turn the boat. The rotation of the entire assembly allows for the entire drive system to maintain its rigidity and alignment while simultaneously allowing the blades to be turned from a straight and forward orientation. In some aspects, the boat  1010  also utilizes a rudder  1703  wherein the shaft  1704  of the rudder is coupled to the rotating drive unit  1060 . In some aspects, a rudder coupled to the boat  1010  and not the rotatable drive unit is used. In some aspects, once the boat has completed a turn the rotation of the drive unit and struts and blades may be re-established into a more neutral position. In some aspects, the rotation of the entire drive assembly including struts and blades may utilized for reverse thrust, in that the entire drive assembly may be rotated 180 degrees. 
       FIGS. 36A-E  illustrate a pivoting hydrofoil blade system according to some embodiments of the present invention. In this exemplary embodiment, the struts  1121   a ,  1121   b  with their hydrofoil blades  1122   a ,  1122   b  may be coupled to or continuous from drive rods as described above. A strut  1121   a  may be removeably but fixedly coupled to the structural element  1128  of the blade  1122   a . The entire blade assembly may be adapted to be fixedly coupled to the structural element with a cap which may be inserted and attached from the underside of the blade assembly, for example. The blade  1122   a  is adapted to rotate around the structural assembly  1128 . The rotation of the blade may be resisted with springs  1141  which rotationally couple the blade to the structural element. A cover  1142  in the upper blade surface may allow access to a recess  1143  which allows for access to, and installation or removal of, various components. 
       FIG. 36D  illustrates a see through view of the blade  1122   a  wherein stiffening elements  1133 ,  1132 ,  1131 ,  1130  are used longitudinally to provide strength and stiffness to the blade. The stiffeners may have removable caps  1144  which allow the rod to be inserted into the blade via the recess  1143  with the cover removed. Bearings may be present at the center stiffening elements  1130  and the end stiffening elements  1132 , and other elements. The torsion springs  1141  are adapted to provide torsional resistance coupling between the structural element  1128  and the blade  1122   a . As the structural element is fixedly coupled to the strut  1121   a , the torsion springs allow for rotation of the blade along the axis of the structural element during loading of the blade. In an exemplary embodiment, there may also be mechanical stops which limit the rotation of the blade relative to the structural element  1128 . For example, the mechanical stops may limit the axial rotation to +/−15 degrees. The springs, however, are sized to limit that rotation to a lower range during expected operation loading. For example, the torsion springs may limit the rotation of the blade to +/−5 degrees during normal operation expected maximum loads. 
     As evident from the above description, a wide variety of embodiments may be configured from the description given herein and additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader aspects is, therefore, not limited to the specific details and illustrative examples shown and described. Accordingly, departures from such details may be made without departing from the spirit or scope of the applicant&#39;s general invention.