Abstract:
A method of operating a sailing boat is provided, comprising detecting a force of a mast of a sailing boat on a mast step of a hull of the sailing boat, while the sailing boat is sailing across a body of water, and providing a reading of the force.

Description:
BACKGROUND OF THE INVENTION 
     1). Field of the Invention 
     This invention relates to a sailing boat and, more specifically, to detection of a force in an elongate direction of a mast of the sailing boat. 
     2). Discussion of Related Art 
     Various factors may influence the performance of a sailing boat in racing conditions. One of the factors that influence the performance of the sailing boat is the positioning and shaping of the sails. The positioning and shaping of the sails depend to a large extent on the positioning of a mast of the sailing boat and any bends in the mast. The positioning and shape of the mast can be calculated by measuring, amongst others, a force in an elongated direction along the mast. 
     In some boats, the force can be increased by sliding more lift plates in between a lower surface of the mast and an upper surface of a mast step of a hull of the boat. The force can be decreased by removing lift plates. A jack is typically used to elevate the mast so that the lift plates can be inserted or be removed. The force can also be increased or decreased by tightening or loosening the rigging. 
     A rough indication of the force in the mast is obtained by elevating the mast slightly off the lift plates and then measuring the fluid pressure of the jacks that are used to elevate the mast. Once the mast is lowered into its sailing position, there is no way of accurately knowing what the force in that mast is. The disadvantage of this is that there are varying differences between the measured force when the mast is slightly raised, and the actual force when the mast is in its sailing position. A further disadvantage is that force measurements can only be made while the boat is at dock in a stationary position, i.e., not in “real time” while sailing. 
     BRIEF SUMMARY OF THE INVENTION 
     According to one aspect of the invention, a sailing boat is provided, having a hull, a mast, at least one detector, and an output device. The hull has a mast step. The mast extends upward from the mast step and has a lower end resting in a sailing position on the mast step. The detector detects a variable, indicative of a force exercised by the mast onto the mast step while resting in the sailing position. The output device is connected to the detector, and provides a reading indicative of the variable. 
     Preferably, no lifting jack is used to keep the mast in the sailing position. 
     The detector may detect strain deformation. The detector may, for example, include at least one strain gauge or a piezoelectric crystal. 
     The sailing boat may, for example, include at least a first lift plate. The detector may be secured to the lift plate. The lift plate may be removably located between an upper surface of the mast step and a lower surface of the mast, together with the detector and, after lifting up the mast relative to the mast step, be removable together with the detector from between the upper surface of the mast step and the lower surface of the mast. 
     The sailing boat may further include a load cell body, wherein the detector is secured to the load cell body, to jointly form a load cell. The load cell body may be mounted to the lift plate, and the detectors may detect strain deformation of a portion of the load cell body. 
     The load cell body may have a button portion standing proud of a surface of the lift plate, and the detector may detect depression of the button portion toward the lift plate. 
     The sailing boat may further include a second lift plate having a surface against which the button rests. 
     The sailing boat may further include a plurality of load cells around the mast. 
     The sailing boat may further include a plurality of detectors around the mast. 
     The output device may be mounted to the plate, and a change in the force exercised by the mast causing a direct change in the force displayed on the output device. 
     The reading provided by the output device is preferably force. 
     The sailing boat may further include rigging connected between an upper portion of the mast and the hull. The rigging may include a forestay, one or more backstays, and/or shrouds. The forestay may be connected between an upper portion of the mast and a front portion of the hull, and the backstay may be connected between the upper portion of the mast and a rear of the hull, the forestay and the backstay both being under tension to at least partially contribute to the force. The rigging may thus be adjustable to change the force. 
     According to another aspect of the invention, a combination lift and force detection plate is provided, including a lift plate and detector. The lift plate is insertable between a mast step of a hull and a mast of a sailing ship. The detector may be mounted to the lift plate, to be insertable with the lift plate between and to be removable with the lift plate from between the mast step and the mast. The detector may detect a force exercised by the mast thereon, and provide an output of the force. 
     The lift plate may have a slot which moves over a post that aligns the mast. The combination may further include a plurality of load cells around the mast. 
     According to a further aspect of the invention, a method of operating a sailing boat is provided, comprising detecting a force of a mast of a sailing boat on a mast step of a hull of the sailing boat, while the sailing boat is sailing across a body of water, and providing a reading of the force. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is further described by way of example with reference to the accompanying drawings, wherein: 
     FIG. 1 is a perspective view of a combination lift and force detection plate according to an embodiment of the invention; 
     FIG. 2 is a perspective view of a load cell used in the combination of FIG. 1; 
     FIG. 3 is a partially cross-sectioned rear view illustrating components of a sailing boat, including a mast which is elevated into a raised position; 
     FIG. 4 is a view similar to FIG. 3, after the mast is lowered into a sailing position; 
     FIG. 5 is a side view of the sailing boat, illustrating further components thereof; and 
     FIG. 6 is a rear view of the sailing boat. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 of the accompanying drawings illustrates a combination lift and force detection plate  10 , according to an embodiment of the invention, including a lift plate  12 , three load cells  14 A,  14 B, and  14 C, a signal converter  16 , and an output device  18 . 
     The lift plate  12  is made from a rigid material such as aluminium or titanium. The lift plate  12  has upper and lower surfaces  20  and  22  that are precision-machined to be extremely flat and in planes parallel to one another. The lift plate  12  has a length in an x-direction, and a width in a y-direction, the length being longer than the width. The lift plate  12  also has a height in a z-direction, both the length and the width being multiples of the height. A slot  24  is formed in the lift plate  12  along the length thereof, and is open toward the rear of the lift plate  12 . 
     Three circular openings  26 A,  26 B, and  26 C are machined into the upper surface  20  of the lift plate  12 . Each opening  26 A, B, or C is formed through a portion only of the lift plate  12 , so that a respective land  30  remains below the respective opening  26 A, B, or C. Three grooves  28 A,  28 B,  28 C are formed in the upper surface  20  of the lift plate  12 . Each groove  28 A, B, or C extends from a respective opening  26 A, B, or C to a front of the lift plate  12 . The grooves  20 A, B, and C are relatively shallow and much thinner than shown in the drawing. 
     FIG. 2 illustrates one of the load cells  14 . The load cell  14  has a load cell body  31  with an upper surface thereof forming a button  32 . The load cell body  31  is typically made of a metal. Strain gauges (not shown) are secured to the load cell body  31 . When the button  32  is depressed in a downward direction, and the load cell body  31  deforms, the strain gauges deform together with the load cell body  31 . The strain gauges can thus detect depression of the button  32 . In another embodiment, a piezoelectric crystal can be used instead of a strain gauge. A piezoelectric crystal provides an electric output in response to a physical load. 
     A cable  34  is secured to the load cell body  31  and connected to the strain gauges. An electric voltage can be applied to the strain gauges, and signals can be received from the strain gauges through the cable  34 . The signals received through the cable are indicative of the force depressing the button  32 . 
     Referring again to FIG. 1, a respective one of the load cells  14 A,  14 B, and  14 C is inserted into a respective one of the openings  26 A,  26 B, and  26 C. The buttons  32  stand proud of the surface  20  by approximately 0.125 mm. A respective cable ( 34  in FIG. 2) attached to a respective load cell  14 A,  14 B, or  14 C is positioned so that it runs in a respective one of the grooves  28 A,  28 B, or  28 C to the front of the lift plate  12 . The signal converter  16  is attached to the front of the lift plate  12 , and all the cables are connected to a signal converter  16 . The signal converter  16  thus receives signals through all the cables from all the load cells  14 A, B, and C. 
     The output device  18  may, for example, be a liquid crystal display output that can provide a visible reading. The output device  18  is connected to the signal converter  16 . The signal converter  16  adds the signals received from the strain gauges of the load cells  14 A, B, and C and converts the summation to a value, which is provided to the output device  18 . The value is then displayed as a reading on the front of the output device  18 . The reading on the output device  18  is the summation of the forces depressing the buttons of the load cells  14 A, B, and C in a direction opposite to the z-direction. A change in the forces depressing the buttons causes a direct change in the reading of the output device  18 . A change in the summation of the forces from 15000 lbF to 16000 lbF, for example, will cause a change in the reading from 15000 lbF to 16000 lbF. 
     FIG. 3 illustrates components of a sailing boat  40 , according to an embodiment of the invention, including the combination lift and force detection plate  10 , two additional lift plates  42  and  44 , a hull  46 , a post  48 , a mast  50 , and a lifting rod  52 . 
     The hull  46  has a mast step  54  having an upper surface  56 . The post  48  is secured to the mast step  54  and extends upward therefrom. The mast  50  has a lower end  58 . A cavity  60  is formed into a lower surface of the lower end  58  of the mast  50 . The lifting rod  52  is located on opposing sides of the lower end  58  of the mast  50 , and is secured to the lower end  58 . 
     The cavity  60  is positioned over the post  48  so that the post  48  aligns the mast. Two jacks  62  are located between the lifting rod  52  and the mast step  54  on opposing sides of the mast  50 . The jacks  62  are operated so that they engage the lifting rod  52  and elevate the lifting rod  52  together with the mast  50  into a raised position. This is normally done while in a stationary position at dock and with the sails down. 
     The lift plate  42  is inserted between the upper surface  56  and a lower surface  63  of the lower end  58  of the mast  50 . The lift plate  42  is the same as the lift plate  12  illustrated in FIG. 1, except for the cutaways and components attached thereto. The slot ( 24  in FIG. 1) in the lift plate  42  allows for the lift plate  42  to be moved so that the post  48  moves down the slot. 
     The combination lift and force detection plate  10 , with all its components, is then located on the lift plate  42  and inserted below the mast  50  in a similar manner. The lift plate  44  is then also inserted below the mast  50  and located on the combination lift and force detection plate  10 . A lower surface of the lift plate  44  rests on the three buttons of the three load cells  14 A, B, and C illustrated in FIG.  1 . More than three load cells may be used, although at least three load cells are sufficient to create a plane. 
     FIG. 4 illustrates the components of FIG. 3 after the jacks  62  are operated to lower the mast  50  into a sailing position on top of the lift plate  44 , and after the jacks  62  are removed. The mast  50  now creates a downward force F onto the lift plate  44 , and through the lift plates  12  and  42  onto the mast step  54 . The force F is carried by the buttons of the load cells  14 A, B, and C illustrated in FIG.  1 . The reading provided by the output device  18  indicates the magnitude of the force F in the mast  50 . 
     What should be noted is that the magnitude of the force F can be determined while the mast  50  is in its sailing position illustrated in FIG.  4 . Moreover, the output device  18  can provide an indication of the magnitude of the force F while the sailing boat is sailing across a body of water. The sailing boat may, for example, be cruising at speeds of 5 knots, 10 knots, or more while the magnitude of the force F is displayed in “real time” on the output device  18 . The output device  18  is also conveniently located directly on the lift plate  12 , thereby allowing a person essentially to “read the plate.” The magnitude of force can also be written to a computer storage medium such as a hard drive. 
     FIG.  5  and FIG. 6 illustrate other components of the sailing boat  40 , including a rigging in the form of a forestay  70 , a backstay  72 , and shrouds  74 . The forestay  70  is connected between an upper end of the mast  50  and a front of the hull  46 , and the backstay  72  is connected between the upper end of the mast  50  and a rear of the hull  46 . In another embodiment, there may be more than one backstay, or no backstays at all. The shrouds  74  form a link between the side of the mast  50  at multiple positions along the mast  50  and sides of the hull  46 . The forestay  70 , backstay  72 , and shrouds  74  are all under tension so that they contribute the force F together with the weight of the mast  50 . The rigging can be tightened or loosened at any time including when the sails are up and the sailing boat  40  is sailing, with a corresponding change in the force F and a corresponding change in the readout on the output device ( 18  in FIG.  1 ). 
     While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative and not restrictive of the current invention, and that this invention is not restricted to the specific constructions and arrangements shown and described since modifications may occur to those ordinarily skilled in the art.