Abstract:
The present invention relates to a flexible propeller that has the feature of generating propulsive force in only one direction, irrespective of the direction of rotation. The flexible propeller may be used in a mechanism similar to a sterndrive, being actuated by two cables and that are wound around a threaded spindle on the sterndrive shaft, one clockwise and the other anticlockwise, and capable of being actuated alternately longitudinally, causing the flexible propeller to rotate in alternate directions, first in one direction and then in the other. The sterndrive in turn may be used in compact structures that can be fitted to catamarans, kayaks or other types of small vessels, without the need for major alterations to the original vessel.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefits of PCT/BR2011/000469, filed on Dec. 15, 2011, and Brazilians Applications BR No. PI1005547-9, filed on Dec. 15, 2010, and BR No. C11005547-9 filed on Oct. 18, 2011, both of which are entitled “HÉLICE FLEXÍVEL E APLICAçÕES PARA EMBARCAçÕES MIÚDAS” translated here to “FLEXIBLE PROPELLER AND USES FOR SMALL VESSELS”, and are incorporated herein by reference in their entireties. 
     FIELD OF THE INVENTION 
     The present invention relates to the field of small boats. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a flexible propeller  7  that has the characteristic of generating propulsive force in one direction regardless of the direction of rotation. 
     The flexible propeller  7  can be used in a mechanism similar to a sterndrive, powered by two cables  12  and  13  that are wound around a threaded spindle  14 , present on the propeller shaft  8 , one clockwise and the other counterclockwise, allowing them to be driven along, alternately, making the flexible propeller  7  rotate alternately, sometimes in one direction, sometimes in another. 
     The sterndrive may be used in compact structures that allow themselves to be adapted to catamarans, boards, kayaks, boats or other small vessels, without requiring major changes to the original vessel. 
     The propulsive systems for boats of the current state of the art, for the most part, do not allow themselves to be adapted for surfboards, kayaks, canoes or similar, without the need to pierce the hull to allow the passage of the transmission system, as in the case of U.S. Pat. No. 4,474,502 and U.S. Pat. No. 5,194,024. And the few propulsive systems that can be adapted are inefficient, or complex, such as the U.S. Pat. No. 2,873,713. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The preferred embodiments of the present invention will now be described, by way of non-limiting examples of the invention, with reference to the attached drawings. In the drawings: 
         FIG. 1  is made up of figures showing the components of a propeller assembly according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 2  is made up of figures showing the details of mounting a propeller according to the invention “flexible propeller and uses for small vessels”, in a pusher configuration; 
         FIG. 3  is made up of figures showing the details of mounting a propeller according to the invention “flexible propeller and uses for small vessels”, in a tractor configuration; 
         FIG. 4  is made up of figures illustrating the operation of a propeller according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 5  is made up of figures that shows the items required to fabricate a flexible a propeller according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 6  is made up of figures showing the details of the fabrication of a flexible blade of a propeller according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 7  is made up of figures showing the details of bonding the blades at the PVC tube of a flexible propeller according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 8  is made up of figures illustrating the installation of propeller in a sterndrive shaft according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 9  is made up of figures that show a sterndrive that can be used with a flexible propeller according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 10  is made up of figures illustrating the mounting of the propeller shaft in the tube positioned at the bottom of the sterndrive according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 11  shows a sectional view of the tube and bushings located at the bottom of the sterndrive, showing the threaded spindle present in the propeller shaft according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 12  is made up of figures that illustrate the assembly of the plate in the base of a sterndrive according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 13  is made up of figures illustrating the operation of a retraction and locking mechanism of a sterndrive according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 14  is made up of figures showing the detail of the assembly of the mechanical parts of the propulsive system according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 15  is made up of figures illustrating the process of mounting the cables of the propulsion system according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 16  is made up of figures that complement the understanding of the process of mounting the cables of the propulsion system according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 17  is made up of figures showing the operation of the propulsion system according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 18  is made up of figures showing a device that uses the propulsion system according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 19  is made up of figures that show the installation of cables in a device that uses the propulsion system according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 20  is made up of figures showing a base containing three inserts that allow the assembly of a device that uses propulsion system according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 21  is made up of figures showing the assembly of a device that uses the propulsion system according to the invention “flexible propeller and uses for small vessels” on a base bonded to the front of a board; 
         FIG. 22  is made up of figures showing the operation of a device using the propulsion system according to the invention “flexible propeller and uses for small vessels” mounted on the front of a board; 
         FIG. 23  is a perspective view showing a device using the propulsion system according to the invention “flexible propeller and uses for small vessels” mounted on the front of a kayak; 
         FIG. 24  is a perspective view showing a device using the propulsion system according to the invention “flexible propeller and uses for small vessels” in a compact condition; 
         FIG. 25  is a perspective view showing a foldable structure to be used with the propulsion system according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 26  is made up of figures illustrating the mounting of the secondary structure at the main structure of a foldable structure to be used with the propulsion system according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 27  is made up of figures showing how it works the refraction, extension and locking mechanism of the secondary structure of a foldable structure to be used with the propulsion system according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 28  is made up of figures showing the mounting of cables and levers with pedals in a foldable structure to be used with the propulsion system according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 29  is made up of figures showing the assembly of a handlebar and connecting rod in a foldable structure to be used with the propulsion system according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 30  is made up of figures showing the mounting of a seat in a foldable structure to be used with the propulsion system according to the invention “flexible propeller and uses for small vessels”; 
         FIG. 31  is made up of figures showing a foldable structure to be used with the propulsion system according to the invention “flexible propeller and uses for small vessels” adapted for use with a pair of floats arranged in a catamaran configuration; and 
         FIG. 32  is made up of figures that present a mechanism for retracting and locking the sterndrive of a propulsion system according to the invention “flexible propeller and uses for small vessels”. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a perspective view of the propeller  96  according to the present invention. It is mounted on a rigid shaft  97 , which has two holes  98  and  99  to the insertion of a rigid rod  100 , which is positioned perpendicular to the shaft  97 . The propeller  96  is made from flexible material and has two perpendicular holes in its interior, one hole to accommodate the shaft  97  and the other along the leading edge of the blades, to accommodate the rod  100 . The propeller  96  can be mounted on the shaft  97  on the tractor or pusher configuration.  FIG. 2  shows the assembly procedure of the propeller  96  in the pusher configuration. First propeller  96  is inserted into the shaft  97 . Subsequently, the rod  100  is inserted through the slot  101  present near the blade tip, according sectional detail of  FIG. 2 , passing into the hole  98  of the shaft  97 . Finally the end of the blade is inserted on the rod  100 , which is positioned without dropping.  FIG. 3  shows the assembly procedure of the propeller  96  in the tractor configuration. First propeller  96  is inserted into the shaft  97 . Subsequently, the rod  100  is inserted through the slot  101  present near the tip of the blade passing into the hole  99  of the shaft  97 . Finally the end of the blade is inserted on the rod  100 , which is positioned without dropping. 
       FIG. 4  illustrates sections of the propeller  96  blades to facilitate visualization. The first pair of images, located above illustrates the operation of the propeller  96  in the pusher configuration, and the pair located below illustrates the operation in the tractor configuration. As the propeller  96  is made with flexible material and has a rigid rod  100 , positioned along the leading edge, as it rotates in one direction, the water exerts a pressure, which center of pressure Cp is located behind the leading edge, deflecting the blades as shown in  FIG. 4  and generating a propulsive force F. Turning in the opposite direction, the propeller  96  also generates a propulsive force F in the same direction. 
     The flexible propeller may be produced in various ways. One example is by injecting rubber material in a mold. The following describes a way to manufacture a propeller from flexible PVC fabric. Basically it uses two pieces of flexible PVC fabric  1 , cut as detailed in  FIG. 5  and a rigid PVC tube  2 , which has a hole as the detail of  FIG. 5 . Flexible PVC fabric  1  will form the propeller blades and the rigid PVC tube  2  will provide rigidity to the propeller shaft. First adhesive is applied to flexible PVC fabric  1  in the hatched region, as shown in  FIG. 6 . Later on fabric  1  is bent on its axis of symmetry and glued as  FIG. 6 . As the region close to the fold has no application of adhesive, a hole  3  is formed in the region of the fold. Subsequently, each of the fabric  1  is glued to the tube  2  as shown in  FIG. 7 . The fabric  1  should be positioned so that the hole  3  close to the flap  4  coincides with the hole  5  of tube  2 . The tab  4  involves the tube  2 , one for each side, providing a large area of bonding. It can be seen that the leading edges  6  of the blades form an angle α with less than 180 degrees.  FIG. 8  shows how propeller  7  is mounted on the shaft  8  of the sterndrive. First the tube  2  is inserted into the shaft  8  until the moment that their holes  5  are aligned with the holes  9  present on the shaft  8  of the sterndrive. Subsequently, a rigid rod  10  is inserted through hole  3  passing through the hole  5  and the hole  9  present on shaft  8  of the sterndrive. The rod  10  passes through holes  3  of the two blades, forcing the leading edge  6  to be aligned. As a result, the trailing edge  11  of the blade is loose. The smaller the angle α, the looser will be the trailing edge  11  of the blades and the lower the effective pitch of the propeller  7 . Therefore the angle α determines the value of the pitch of the propeller  7 . To prevent the rod  10  to move out of its position, the holes  3  at the ends of the blades are sealed with glue, as indicated by the arrow at the bottom of  FIG. 8 . The propeller  7 , as it is made of flexible material, can be deflected around the rod  10  by the pressure exerted by the water and assuming a helical shape, generating a propulsive force F whose direction coincides with the axis  8  and is always pointing from the trailing edge  11  to the leading edge  6  of the blades, regardless of the direction of rotation of the propeller  7 . 
       FIG. 9  shows a sterndrive that can be used with the flexible propeller  7 . The working principle consists of two cables  12  and  13 , which are wound around a threaded spindle  14  present on the shaft  8 . The cable  12  is wound clockwise and the cable  13  in a counterclockwise direction. Cables  12  and  13  go through two independent pulleys  15  and can be driven along alternately making the shaft  8  of the propeller  7  rotate alternately, sometimes in one direction, sometimes in another. 
     The threaded spindle  14  is fixed on the shaft  8 , thus, there is no relative motion between them. The shaft  8  is mounted on the tube  16  located at the bottom of the plate  17  of the sterndrive, as shown in  FIG. 10 . The shaft  8  is mounted supported by two bushings  18  which are fitted at the ends of the tube  16 . The threaded spindle  14  is a thread whose root fillet has a round profile to accommodate the cables  12  and  13 , which also have a round section.  FIG. 11  shows a sectional view of the tube  16  and bushings  18 , where it appears the shaft  8  also. It is noticed that the threaded spindle  14  serves as a guide to cable winding. The cable is positioned between the root of the fillet and the inner wall of the tube  16 . The tube  16  has two slots  19 , one on each side, allowing the cable to pass through it. The slot  19  is elongated to allow longitudinal movement of the cable as it rolls up and unrolls. 
     The plate  17  is mounted in the base  20  of the sterndrive in an articulated manner, as shown in  FIG. 12 . For this purpose the plate  17  is positioned in a way that the holes  21  and  22  are aligned. A spring  23  having a pin  24  is then positioned as shown in  FIG. 12  and the parts are joined by screw and nut. 
       FIG. 13  shows a configuration example of the spring  23 , plate  17  and base  20  of the sterndrive. In this example the pin  24  abuts the shoulder  25  present on the plate  17  while the force F acts on the axis  8 , maintaining the assembly in operating condition (propeller  7  was omitted). In a collision with an object, the plate  17  of the sterndrive is free to rotate backwards. And, for a situation of transport or storage, the plate  17  can be taken forward and kept locked. To do so, it must first pull the pin  24 , deflecting the spring  23  until the moment in which the pin  24  releases the movement of the plate  17  forward. The plate  17  can then be rotated forward until the moment that the pin  24  engages the hole  26  present on the plate  17  by the force of the spring  23 . 
       FIG. 14  shows the detail of the assembly of the mechanical assemblies making up the propulsion system, which are mounted on the end of a tube  27 . First, a pair of pulleys  15  is mounted in the end of the tube  27 . The pair of pulleys  15  rotates, independently, around the axis  28 . Subsequently the sterndrive base  20  is mounted on so that it can freely rotate around the axis  29  of base  20 . Washers  30  are positioned on both sides to facilitate articulation and finally the control lever  31  is mounted on the upper part of axis  29 , being linked thereto. 
       FIG. 15  illustrates a manner of assembling the cable  12  and  13 , which are identical and have a ball terminal  32  at one of its ends. First must rotate the shaft  8  until the moment when hole  33  is aligned with the slot  19 . At this time the cable end  12 , which has no ball terminal  32 , is inserted into the tube shaft  8  through the hole  33  and out through the slot  19 . The cable  12  can be pulled completely until the ball terminal  32  stops at hole  33 , as shown in the sectional drawing of  FIG. 15 . The shaft  8  can then be rotated about 6 times (this number is only given as an example and may be larger or smaller depending on the application), so that the cable  12  winds the threaded spindle  14 , being positioned between the root of the screw thread and the inner wall of the tube  16 . After six rounds, it must be rotated slightly more until the hole  34  is aligned with the slot (which does not appear in the  FIG. 15 ) located on the opposite side with respect to the plane of symmetry of the plate  17 . At this time the end of the cable  13  without ball terminal  32  is inserted through the tube  8 , through hole  34  and out through the slot on the opposite side. The cable  13  can be pulled completely until the ball terminal  32  stops at hole  34 . Now it is possible to pull the cable  12  causing a rotation on shaft  8 , causing the cable  13  winds the threaded spindle  14  while the cable  12  unwinds. As shown in  FIG. 16 , the end of the cable  12  must then pass through the hole  35  located in the lower right wall of the tube  27  and subsequently over the pulley  15  and then out the opposite end of the tube  27 . Similarly, the cable  13  must pass through the hole  36  located in the lower left wall of the tube  27  and subsequently over the pulley  15  and then out the opposite end of the tube  27 . To conclude this portion of the assembly, a square terminal  37  is inserted into the end of tube  27 . This terminal serves as finishing and also to prevent the cables  12  and  13  from leaving the groove of pulley  15  as the front wall of the square terminal  37  is located close to the pulley  15 , preventing the cables  12  and  13  leave the groove. The upper wall of the tube  27  is also located near the pulleys  15  preventing the cables  12  and  13  leave the groove. Thus, at the end of these operations, the propulsion system is mounted.  FIG. 17  shows a complete propulsion system. The working principle consists in pulling alternately drive cables  12  and  13 , which will make the propeller  7  rotate alternately clockwise and anti-clockwise. The cables  12  and  13  can be driven directly by the user&#39;s hands or feet, through different mechanisms. As shown in  FIG. 17 , the lever  31  allows the sterndrive to rotate about 45° on each side, enabling vectoring the driving force F of propeller  7 , while the cables  12  and  13  may continue to be actuated. This propulsion system can be adapted for a variety of small boats. 
     Below you will see a device that uses the propulsion system and can be adapted to stand-up paddle boards, as well as canoes and kayaks. According to  FIG. 18 , at one end of the tube  38  is mounted on the propulsion system. At the other end is mounted a lever  39  in an articulated manner to the axis  40 . In this same axis  40  is mounted a pulley  41  on the inside of the tube  38 . The pulley  41  has two grooves, one for the cable  12  and one for the cable  13 . Pedals  42  are mounted on the end of the lever  39  in an articulated manner. The bars  43  of the pedals  42  are then connected via cable  44  to the lever  45 , as shown in  FIG. 18 . According to  FIG. 19 , the cables  12  and  13 , after passing through pulleys  15 , followed by the inner tube  38  passing through the pulley  41  and following to the outside of the tube  38 . After going through the pulley  41 , cable  12  and  13  must reverse sides to allow them are being supported by pulley  41 . The end of the cable  12  and  13  should make loops  46  to enable the handles  47  being fixed by means of hooks  48 . The device described above can be fixed on vessels in three points: two holes located at the ends of the plate  49 , welded at the bottom of the tube  38 , and a third hole  50  located at the front of the tube  38 , near the propulsion system. The following will be presented a way to fix the device on a board  51 . Therefore, a base  52  similar to a traction pad can be pasted on the front of the board  51 . As shown in  FIG. 20 , this base  52  should have three inserts  53 , suitably spaced so that the device can be mounted on the base  52 . The base  52  can be made using, for example, an injection mold, where before injection of the rubber, three inserts  53  are positioned inside the mold. After the injection process, inserts  53  would be inside the base  52 , as suggested by  FIG. 20 . These inserts  53  should have a fixing mechanism, for example, an internal thread, so that the device can be mounted to the base using bolts  54 . As the inserts  53  are spaced apart, the base  52  has a degree of flexibility which allows it to adapt to different conditions of curvature of the deck, being possible to be glued in a variety of stand-up paddle boards. According to  FIG. 21 , being the board  51  equipped with the base  52 , the device can be mounted with the use of three screws  54 .  FIG. 22  shows how the device works. The occupant should sit on the board  51 , and then trigger handles  47  alternately with the hands while directing the vessel with the feet, through the pedals  42 . Removing the device, the board  51  can be used normally, since the base  52  is flat and do not interferes the use of the board. 
     The device can also be adapted to kayaks as shown in  FIG. 23 . The kayak must include three attachment points to permit mounting on the device.  FIG. 24  shows the device with the sterndrive collapsed for transport or storage. It can be observed that the device is simple and compact, occupying a small volume. 
     As  FIG. 25  illustrates a folding structure is designed to be used with the propulsion system, so that it can be actuated by the legs of the user. It basically consists of a main structure  55  and a secondary structure  56  serving as a support for the pedals  57 . The propulsion system is mounted on the rear of the main structure  55  and cables  12  and  13  pass through the tube of the main structure  55  coming out on front of it. On the front of main structure  55  is mounted in pivotable manner, the secondary structure  56 , as shown in  FIG. 26 . First, a pin  58  is mounted in the slot  59  present on the main structure  55 . The assembly procedure consists of introducing a guide tube  60  from the front of the main structure  55  until the axial hole of the guide tube  60  is aligned with the slot  59 . At this time, the pin  58  can be inserted into the axial hole of the guide tube  60  until the moment when the hole present in the central part of pin  58  is aligned with the hole present in the central part of tube guide  60 . Subsequently the hook end of the tension spring  61  can be introduced into the tube guide  60  hole passing through the pin  58  hole and eliminating thus the possibility of axial displacement between the guide tube  60  and pin  58 . The hook from the opposite end of the tension spring  61  is fitted in the hole present in the plate  62 . At this time the secondary structure  56  and two pulleys  15  are mounted on the same shaft  63  and the plate  62  is also mounted in the central part of this same shaft  63 . To the assembly, secondary structure  56 , the pulleys  15  and the plate  62  are positioned relative to the front of the main structure  55  so that the holes are aligned, as suggested in  FIG. 26 . When the holes are aligned, the shaft  63  can be introduced, completing the assembly of these elements. 
       FIG. 27  shows how secondary structure  56  locking mechanism works. The tension spring  61  maintains the pin  58  constantly pressed against the end of the slot  59 . To lock the secondary structure  56  in the operating position, simply rotate it in a counterclockwise direction, according to  FIG. 27 . As the secondary structure  56  is rotated, the plate  64  gradually triggers the pin  58  which is automatically inserted into the slot  65  present on the plate  64 , keeping the secondary structure  56  locked in the operating position. To retract, you must pull the pin  58  with the fingers toward the other end of the slot  59 , as suggested by the arrow in  FIG. 27 , until the pin  58  clears the slot  65  present on the secondary structure  56  allowing it to rotate clockwise. The secondary structure  56  can be rotated to be parallel to the main structure  55 . This condition minimizes volume for transport and storage. 
     As shown in  FIG. 28 , the end of the secondary structure  56  is a tube  66  for mounting levers  67  with pedals  57 . To assembly the levers  67 , first the bushings  68  are inserted into each end of the tube  66 . Then the levers  67  can then be introduced, one on each side. Finally a bolt and nut are added. The levers  67  are free to rotate around the axis of the tube  66 . 
     After mounting the propulsion system at the rear end of the main structure  55 , the cables  12  and  13  passes through the tube and out at the front of it, passing under the grooves of pulley  15 , as suggested by  FIG. 28 . Each one of the levers  67  has a shaft  69  for fixing the end of the cable  12  and  13 . The end of each cable is then fixed around lugs  70 . The lug  70  is then mounted on the shaft  69 . To do so, first the hole of lug  70  is inserted in the shaft  69  and a subsequent bolt is then added. The lug  70  has freedom of rotation around the shaft  69 . This way, you can trigger the pedals  57  with the feet, actuating the propeller  7 . 
     As shown in  FIG. 29 , handlebar  71  is mounted on the main structure  55 . To do so, the shaft  72  located in the central position of the handlebar  71  is inserted passing through the hole  73  located in the main structure  55 . Subsequently a bolt  74  is fixed in the upper position of the shaft  72 . The handlebar  71 , which has freedom of rotation around the axis  72 , is connected to the lever  31  by means of a rod  75 . The lever  31  is fixed to the sterndrive base  20 , which is pivotally mounted on the main structure  55 , allowing the user to drive the boat through the handlebar  71 . The ends of the handlebar  71  may be articulated to allow adjustment according to the height of the user and also to assume a more compact condition for transport and storage. 
       FIG. 30  illustrates the assembly of a seat, which consists of the bottom  76  and backrest  77 . The bottom  76  consists of a rigid rectangular base  78 , which is joined by rivets  79  to a pair of tubes  80 , each one having one end formed and drilled to be mounted on the backrest  77 , which is constructed in the same way. A triangular support  81  is mounted at backrest  77 . It consists of a round section metal bar, bent as shown in  FIG. 30 . On the sides of the tubes of the backrest  77  there are holes  82  where the triangular support  81  is embedded. The procedure consists of deforming elastically the triangular support  81  which can then be fitted into the holes  82 . After fitting, the triangular support  81  returns to its original shape, remaining positioned on the backrest  77  of the seat. The seat is fixed to the main structure  55  by a pin  83  and can be fixed in different positions to adjust according to the length of user&#39;s legs. The fixing procedure is to position the seat so that the holes  84  present at the ends of the tubes  80  are aligned with the holes  85  present on the side walls of the main structure  55 . At this point the pin  83  can be inserted, thus fixing the seat to the main structure  55 . The notch  86  at the tip of the triangular support  81  can then be fitted into one of the holes  87  in the upper wall of the tube of main structure  55 , providing the necessary support for the backrest  77 . This system allows to adjust the inclination of the backrest  77  by changing the hole  87  where the notch  86  is attached. 
       FIG. 31  shows how the folding structure can be used in a catamaran configuration. To do so, four tubes  88  are welded to the sides of the main structure  55  which subsequently receives sleeves  89 . Four connecting rods  90  can then be assembled to the tube  88  connecting the main structure  55  to a pair of floats  91 , arranged in a catamaran configuration. The folding structure can assume a compact condition for a transport or storage, as can be seen in  FIG. 31 . The plate  17  can be retracted forward and maintained locked, the secondary structure  56  can be retracted to be parallel to the main structure  55 , the seat can be removed by simply removing the pin  83 , and the ends of the handlebar  71  can be rotated to assume a more compact condition. These operations can be carried out quickly and without the need of any tools. 
       FIG. 32  presents a mechanism to retract and lock the sterndrive. The base  20  has a slot  92 , in which is mounted a pin  93  so as to be able to move longitudinally along the slot  92 . A wire spring  94  is also mounted on the base  20  to constantly press the pin  93  against the lower end of slot  92 . Finally the plate  17  is mounted pivotable about the axis  95 . The plate  17  has slots on its top to snap the pin  93 . To retract the sterndrive just pull the pin  93  as indicated by the arrow, unlocking the slot and allowing the plate  17  to rotate. When the plate  17  is at an angle of approximately 90 degrees, the pin  93  will automatically snap into another slot, pushed by the wire spring  94 , keeping the plate  17  locked in the retracted position.