CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a National Stage Application of PCT International Application No. PCT/EP2011/059712 (filed on Jun. 6, 2011), under 35 U.S.C. §371, which claims priority to Austrian Patent Application No. A977/2010 (filed on Jun. 14, 2010), which are each hereby incorporated by reference in their respective entireties. 
     
    
     FIELD OF THE INVENTION 
       [0002]    Embodiments of the present invention relates to a watercraft, comprising at least one hydrofoil which is height-adjustable between a position disposed in the region of the hull and a position remote from the hull, with a recess preferably being provided in the hull which accommodates the hydrofoil in the region of the hull. 
       BACKGROUND OF THE INVENTION 
       [0003]    It is known to provide watercraft with hydrofoils which allow lifting the hull from the water from a specific minimum speed. Flow resistance can consequently be reduced considerably and higher speed can be achieved at lower fuel consumption. Furthermore, driving behavior which is substantially uninfluenced by the movement of waves can substantially improve comfort. 
         [0004]    The hydrofoils are usually attached to outriggers at sufficient distance beneath the hull in order to thereby reach the required height in hydrofoil operation. In standstill or at low travelling speeds, this leads to high draft with the likelihood of damage to the hydrofoils by obstructions under water. 
         [0005]    This also leads to the consequence that hydrofoil craft cannot be operated in shallow water or close to the shore. Furthermore, the sensitive hydrofoils are bulky during transport of the boat and can therefore easily be damaged unless they are dismounted. 
         [0006]    In order to avoid these disadvantages, vessels are known which comprise adjustable hydrofoils. As a result, the hydrofoils can be retracted in displacement mode for reducing the draft. Such a solution has been described in U.S. Pat. No. 4,582,011 A, for example. 
         [0007]    The disadvantage of this solution is that the likelihood of damage is reduced but not avoided. 
       SUMMARY OF THE INVENTION 
       [0008]    It is the object of the present invention to further develop the known watercraft in such a way that an especially sturdy construction is achieved which is insensitive to any obstructions and additionally allows simple, secure and compact transport. 
         [0009]    It is a further object of the invention to provide a watercraft which is extremely easy to steer and shows good maneuvering properties both at high and low speeds. 
         [0010]    It is provided in accordance with the invention that the hydrofoil is pivotably attached to an arm about a longitudinal axis and/or is arranged in a telescopically extendable manner in the axial direction. 
         [0011]    Pivotable about a longitudinal axis shall mean in this case that the hydrofoil which protrudes laterally from its linkage point can be brought for example from a horizontal position to an externally descending or an externally ascending position. As is the case with an aircraft whose airfoils have a specific angle in relation to the median plane, the position of the hydrofoils is relevant for the behavior in curves. It can be influenced as desired by the adjustment in accordance with the invention. 
         [0012]    Telescopic adjustment is additionally or alternatively provided, i.e. the length of the hydrofoils can be changed. This measure similarly contributes to influencing the behavior in the curve as desired. 
         [0013]    As a result of the solution in accordance with the invention, disturbances are minimized when the hydrofoil is retracted, i.e. in displacement operation. The watercraft can therefore also be operated in shallow water and can therefore drive up a beach without any likelihood of damage. 
         [0014]    It is especially advantageous from a constructional viewpoint when the hydrofoil is arranged on a telescopically extendable arm. A large adjustment range can be achieved thereby, with the hydrofoil also being optimally situated in intermediate positions. 
         [0015]    A further development of the invention is especially advantageous in which the adjustment range is increased by a pivoting arm to which the hydrofoil is attached. The pivoting arm can absorb forces and moments caused by the hydrofoils especially well. 
         [0016]    It is especially advantageous when a drive element such as a jet-ski drive is arranged on the telescopically extendable arm. As a result, not only is a position of the drive achieved which is optimal in all positions of the hydrofoil, but also the introduction of the drive force occurs directly on the component subjected to the flow resistance, leading to a reduction in the material stress. 
         [0017]    It is preferably provided that the recess accommodates the drive element and comprises flow channels for the inflow and outflow. As a result, the drive element can also be used when the hydrofoil has been retracted completely in order to achieve minimal draft. 
         [0018]    Agility and maneuverability can be improved in such a way that the hydrofoils are arranged to be horizontally and/or vertically pivotable. It can be provided alternatively or additionally that the hydrofoils comprise pivotable sections. Similar to the tail unit of an aircraft, control measures can be set by adjusting the sections in the manner of rudders or flaps which improve the maneuverability of the watercraft. 
         [0019]    Independence from the respective position of the hydrofoil during retraction can be achieved in such a way that the recess accommodates the hydrofoils and optionally the pivotable sections in different positions. Control is simplified thereby because the position of the hydrofoils or the sections need not be taken into account during retraction. 
         [0020]    Preferably, a main hull and at least one outrigger arranged in a height-adjustable manner are provided. The hydrofoils can be arranged both on the main hull and also on the outrigger, or on both. The height adjustment can optionally be provided in addition to an adjustment in the width. This allows substantially changing and influencing the driving properties of the watercraft. 
         [0021]    It is mechanically especially advantageous when the outrigger is pivotably arranged on the main hull. As a result, an especially large movement range can be realized with simple means. Preferably, the pivoting device is arranged as a parallelogram guide. 
         [0022]    An especially preferred embodiment of the invention is arranged in such a way that the outrigger can be moved from a position disposed laterally adjacent to the main hull to a position arranged beneath the main hull. 
         [0023]    This embodiment allows providing racing boat characteristics that principally show little stability in addition to the characteristics of an outrigger boat, which racing boat characteristics offer extreme lateral positions and favorable driving behavior in combination with the highest speeds. 
         [0024]    It is provided in an especially preferred manner that at least two outriggers are disposed directly adjacent to one another in the position arranged beneath the main hull and preferably form a common compact hull. Especially advantageous hydrodynamic properties can consequently also be achieved in this position of the outriggers. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    Embodiments of the present invention will be explained below in closer detail by reference to embodiments shown in the schematic drawings, wherein: 
           [0026]      FIG. 1  shows a top view of watercraft in accordance with the invention. 
           [0027]      FIG. 2  shows the watercraft of  FIG. 1  from the side. 
           [0028]      FIG. 3  shows the watercraft of  FIG. 1  from below. 
           [0029]      FIG. 4  shows the watercraft of  FIG. 1  from the front. 
           [0030]      FIG. 5  shows the watercraft of  FIG. 1  from behind with respectively extended hydrofoil. 
           [0031]      FIGS. 6 to 9  show illustrations according to  FIGS. 2 to 5 , with a respectively sunk hydrofoil. 
           [0032]      FIGS. 10 to 17  show a further embodiment of the invention in different positions in illustrations in  FIGS. 1 to 9 . 
           [0033]      FIGS. 18 to 31  show details of the watercraft of  FIGS. 1 to 9  in different variants. 
           [0034]      FIGS. 32 to 38  show a further embodiment of the invention in different positions. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0035]    The watercraft of  FIGS. 1 to 9  in accordance with embodiments of the invention include a main hull  1 , on which a front telescopically extendable arm  2  and a rear telescopically extendable arm  3  are arranged. A front hydrofoil  4  and a rear hydrofoil  5  are respectively attached to the extendable arms  2 ,  3 , which, as shown in  FIG. 2 , can be extended and, as shown in  FIG. 6 , can be retracted. The travel-out movement can be provided by any drive element, preferably a hydraulic drive. Recesses  6 ,  7  are provided in the hull  1  which accommodate the hydrofoils  4 ,  5  in the retracted state. The front recess  6  can be provided with an oval configuration for example, whereas the rear recess  7  can be substantially rectangular. 
         [0036]      FIGS. 10 to 17  show an embodiment in which a main hull  1   a  and two outriggers  10   a  and  10   b  are provided. The two outriggers  10   a  and  10   b  are adjustable to the side and in the height, and can be moved from a position arranged directly beneath the main hull  1   a , as shown in  FIGS. 10 to 14 , to a position arranged laterally adjacent to the main hull  1   a  as shown in  FIGS. 15 to 17 . 
         [0037]    The front telescopically extendable arm  2  and the rear telescopically extendable arm  3  are respectively arranged on the main hull  1   a . A front hydrofoil  4  and a rear hydrofoil  5  can be provided on the extendable arms  2 ,  3  as in the embodiment as discussed above, which hydrofoils are arranged in the extended position at a distance beneath the two outriggers  10   a  and  10   b , which is shown in  FIG. 11  and  FIG. 12 . In the retracted position, the two outriggers  10   a  and  10   b  form a front recess  6   a  and a rear recess  7   a  which accommodate the front hydrofoil  4  and the rear hydrofoil  5 , which is shown in  FIG. 13  and  FIG. 14 . 
         [0038]    Both in the retracted state and also in the extended state of the hydrofoils  4 ,  5 , the front telescopically extendable arm  2  and the rear telescopically extendable arm  3  extend downwardly between the two outriggers  10   a  and  10   b.    
         [0039]    The outriggers  10   a  and  10   b  are arranged in  FIGS. 15 to 17  adjacent to the main hull  1   a . In this case, the hydrofoils  4 ,  5  are accommodated in respective recesses  6 ,  7  of the main hull  1   a , as shown in the embodiment of  FIGS. 1 to 9 . 
         [0040]      FIG. 18  and  FIG. 19  schematically show in detail how the hydrofoil  4  is accommodated in the recess  6 , with differently large hydrofoils  4  being shown. The illustration shows that a flow channel  12  is provided above the hydrofoil  4 , which flow channel is in connection with an inflow channel  9  before the hydrofoil  4  and an outflow channel  11  after the hydrofoil  4 . 
         [0041]      FIG. 20  schematically shows a detailed view of an embodiment in which a jet drive  8  is attached above the hydrofoil  4  and  5 . An inflow channel  9  and an outflow channel  11  are provided before and after the jet drive  8 , so that the jet drive  8  can also be operated in the retracted state. The hydrofoils  4  and  5  comprise a pivotable section in form of an adjustable flap  14 , which enables improved control of driving operation and by means of which the outflow channel  11  can be continuously constricted or closed. 
         [0042]      FIG. 21  shows an intake channel  15  for a remote jet drive (not shown in this case), with the flow being partly guided in the extendable arm. 
         [0043]      FIG. 22  and  FIG. 23  show the hydrofoils  4 ,  5  and the recesses  6 ,  7  in detail. 
         [0044]      FIG. 24  shows a lateral view of a hydrofoil  4   a  which consists of a rigid section  16   a  and one or several extendable sections  16   b.    
         [0045]      FIG. 25  shows the detail of  FIG. 24  from the front. The illustration shows that two hydrofoils  4   a ,  4   b  are symmetrically provided on the holder  16   a . The hydrofoils  4   a ,  4   b  can be retracted telescopically into the holder  16   a  and are shown in the extended position. 
         [0046]      FIG. 26  shows a lateral view of a hydrofoil  4   a  which is inclined downwardly in an oblique fashion. 
         [0047]      FIG. 27  shows two hydrofoils  4   a ,  4   b  in different positions, which hydrofoils can be pivoted about a horizontal axis, i.e. an axis which is parallel to the longitudinal axis of the watercraft. 
         [0048]      FIG. 28  shows two hydrofoils  4   a ,  4   b  in different positions, which hydrofoils can be pivoted about a vertical axis, i.e. an axis which is normal to the longitudinal axis of the watercraft. 
         [0049]      FIG. 29  shows a view of hydrofoils  5   a ,  5   b  which are pivotable about an axis parallel to the longitudinal axis of the watercraft (comparable to  FIG. 27 ), in different positions from below. 
         [0050]      FIG. 30  shows a view of the variant of  FIG. 25  from below. 
         [0051]      FIG. 31  shows a variant of laterally telescopically extendable hydrofoils  5   a ,  5   b  in different positions also from below, similar to the illustration of  FIG. 30  for the hydrofoils  4   a ,  4   b.    
         [0052]    In the embodiment of  FIGS. 32 to 36 , the outriggers  10   a ,  10   b  are respectively linked to a mechanism which consists of two mutually connected pivoting arms  3   a ,  3   c  and  3   b ,  3   d . The outriggers  10   a ,  10   b  can be fastened to the outer pivoting arms  3   c ,  3   d  by being pivotable about a longitudinal axis in order to further increase variability. 
         [0053]    In  FIG. 32 , the outriggers  10   a ,  10   b  are arranged beneath the main hull  1   a , which in this case is only used as the carrier for the superstructures (not shown) and need not necessarily be floatable. The two outriggers  10   a ,  10   b  form a common compact hull at this point, i.e. they form the shape of the boat on their outside and they rest substantially close to one another with their insides. This is a typical position for high-speed travel in which lateral stabilization occurs dynamically. 
         [0054]    In the position of  FIG. 33  the outriggers  10   a ,  10   b  are arranged laterally beneath the main hull  1   a  at a distance, thereby producing an inherently stable position. 
         [0055]    A further displacement of the outriggers  10   a ,  10   b  to the outside leads to the position according to  FIG. 34  in which the pivoting arms  3   a ,  3   c  and  3   b ,  3   d  assume a stretched position. 
         [0056]    A further possibility for variation is shown in  FIG. 35  in which the main hull  1   a  is lifted.  FIG. 36  shows a position for travelling through curves with an inclined main hull  1   a.    
         [0057]      FIGS. 37 and 38  explain another aspect of this embodiment. The pivoting arms  2   a ,  3   a  carry the hydrofoils  4 ,  5  which are therefore height-adjustable because the pivoting arms  2   a ,  3   a  are pivotable about the pivots  22  and  23 .  FIGS. 37 and 38  respectively show the pivoting arms  2   a ,  3   a  in a front retracted position in which the hydrofoils  4 ,  5  are accommodated in their recesses  6 ,  7 , and in the extended position in which the hydrofoils  4 ,  5  are arranged at a distance beneath the outriggers  10   a ,  10   b . Reference numerals  20  and  21  indicate further recesses which are provided in the outriggers  10   a ,  10   b  on the inside in order to enable the passage of the pivoting arms  2   a ,  3   a  in the position of  FIG. 32  through the outriggers  10   a ,  10   b , which otherwise rest directly on each other.
A watercraft including at least one hydrofoil which is height-adjustable between a position disposed in the region of the hull and a position remote from the hull, with a recess being provided in the hull which accommodates the hydrofoil in the region of the hull.