Abstract:
A vessel hull stabilization system is presented that uses hydrofoils mounted on the vessel. The hydrofoils create a counteracting force to the waves that would otherwise cause the vessel to roll pitch. the hydrofoil is connected to the vessel in both passive and an active modes. The hydrofoil consists of a number of configurations that include a number of attached struts and foils which provide additional counteracting forces in response to wave action.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a device for stabilizing boats, in particular yachts. 
         [0003]    2. Discussion of the Related Art 
         [0004]    Boats in general and yachts in particular are subject to the force of wind and waves. These wave actions cause a boat to roll, pitch and yaw in an unpleasant manner. This creates an unpleasant sensation for a person who does not spend a significant time on a boat. The sensation may be so extreme as to cause a condition known as seasickness. These unpleasant forces effect the yacht and passengers at all times, underway and at rest. 
         [0005]    Boat movement, relative to its level position, is measured in terms of pitch (movement along the axis line from bow to the stern), roll (movement along the axis line from the port side to the starboard side), and yaw (a rotational heading movement along the center point of the boat). 
         [0006]    There are a number of ways to reduce vessel movement. A solution is to build a larger vessel, which is usually not an economical solution in most cases. Another approach is to only use the vessel during calm seas, although this is impractical for vessels that must be used on a daily, commercial basis. 
         [0007]    Active control systems have been developed to reduce the problem of vessel roll only. One such device is disclosed in U.S. Pat. No. 4,487,152 to Larson which illustrates the use of an air foil-shaped stabilizer above the propeller to induce a lift at the stern portion of the boat. 
         [0008]    An attitude control device in the form of a wing or vane is also disclosed in U.S. Pat. No. 3,980,035 to Johansson which shows the vane positioned in the slip stream behind the propeller. 
         [0009]    Other developments involve forming the anti-cavitation plate with an inclined lower surface to preclude formation of low pressure areas into which air or exhaust gases can be sucked, and to exert a lift at the stern of the boat. A deflector has also been developed to create a high pressure area at the trailing edge of the anti-cavitation plate to improve trim tab effectiveness by forestalling the passage of air into the area of the trim tab, such as the device disclosed by Holterman in U.S. Pat. No. 3,955,527. 
         [0010]    U.S. Pat. No. 4,708,672 to Bentz a boat stabilization systems uses an adjustable wedge-shaped member formed on an adjustably mounted trim tab located on the underside of an anti-cavitation plate of an outboard motor. The wedge-shaped member tends to have a downwardly inclined lower surface extending generally laterally from and perpendicularly to a fin-shaped member of the trim tab. Movement of the boat through the water imparts a force against the downwardly inclined surface to effect a generally vertical torque on the boat substantially eliminating proposing of the boat in a given speed range. 
         [0011]    U.S. Pat. No. 4,968,275 to Carlson a stabilizer is attached to the cavitation plate on the leg of a motor boat motor. Two elongated tubular members are attached by mounting brackets to the motor&#39;s cavitation plate. The tubular members are attached at a downward angle away from the boat so that an upward force is created by the hydrodynamic jet action of water flowing through the tubular members at the rear of the boat when the boat moves in a forward direction. The upward jet created force at the rear of the boat keeps the boat horizontal and stable at high speeds. 
         [0012]    U.S. Pat. No. 4,995,840 to Seale, et al the describes a stabilizing fin for a motor boat which is of a generally triangular shape, and the fin is attached to the mounting side with a longitudinally extending slot for mounting on a cavitation plate on a motor post of an outboard motor. Suitable means are also provided for removably securing the fin to the cavitation plate. 
         [0013]    U.S. Pat. No. 5,048,449 to Templeman describes a stabilizing system that has the first and second arm portions that are removably attached. The first and second arms together and selectively movable toward and away from each other for varying the width of the slot. The ability to vary the width of the slot for receiving the drive unit allows the stabilizer to be adjusted to fit virtually any conventional outboard or inboard/outboard boat motor. 
         [0014]    U.S. Pat. No. 5,144,904 to Weldon describes a stabilization system when the boat was not in motion. The apparatus for stabilizing boats is comprised of a weighted concave body which is suspended from the boat and which is formed as a grid defining openings through the body and a flexible flap in the concavity of the body, the flap blocking the openings when the body rises in the water due to rolling of the boat so as to inhibit rolling and the flap moving away from the openings to permit the apparatus to rapidly fall as the boat rolls in the opposite direction. 
         [0015]    U.S. Pat. No. 5,848,922 to Itima, et al. describes a stabilization system that attaches above the propeller. It is a hydrofoil stabilizer for a marine motor that includes a hydrofoil wing having a generally planar configuration and a shroud member affixed to an underside of the hydrofoil wing. 
         [0016]    U.S. Pat. No. 6,973,847 to Adams uses a gyroscopic roll stabilizer for control of the boat. The stabilizer includes a flywheel, a flywheel drive motor configured to spin the flywheel about a spin axis, an enclosure surrounding a portion or all of the flywheel and maintaining a below-ambient pressure or containing a below-ambient density gas, a gimbal structure configured to permit flywheel precession about a gimbal axis, and a device for applying a torque to the flywheel about the gimbal axis. The flywheel, enclosure, and gimbal structure are conFIG.d so that when installed in the boat the stabilizer damps roll motion of the boat. Preferably, the flywheel drive motor spins the flywheel at high tip speeds. 
         [0017]    Commercially available stabilizers with varied designs are manufactured by Koopnautic (www.koopnautic.com) 
       SUMMARY OF THE INVENTION 
       [0018]    The present invention provides a way to reduce vessel roll, pitch and yaw motions to provide a more comfortable seagoing experience while the vessel is moving forward at any speed. Additionally the system controls vessel roll at rest. 
         [0019]    The system operates in both passive and active mode. 
         [0020]    In passive mode, the preferred embodiment consists of a hydrofoil attached to the transom of the vessel. The hydrofoil has NACA shaped foil members that create lift forces to counteract forces created against the boat by the waves. These counteracting forces reduce the unwanted movement of the boat, thus leading to stabilization. A jack screw maintains the hydrofoil at the most effective fixed angle of the attack. 
         [0021]    In active mode, a motion measuring transducer is mounted to the vessel and connected to a computer controlled hydraulic system. When the motion sensor transducer detects movement, the hydraulic actuator-coupled to the hydrofoil-moves the hydrofoil to create a counteracting force that reduces the movement of the boat, leading to stabilization. 
         [0022]    A number of embodiments of the hydrofoil are presented that provide vessel stabilization. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    Taking the following specifications in conjunction with the accompanying drawings will cause the invention to be better understood regarding these and other features and advantages. The specifications reference the annexed drawings wherein: 
           [0024]      FIG. 1  is systems diagram of the complete active stabilization system as mounted in the vessel; and includes system electrical and hydraulic components as located on the vessel; and 
           [0025]      FIG. 2  is a close up view of the passive stabilization system as mounted to the stern of the vessel; and 
           [0026]      FIG. 3  is a side view of one stabilization hydrofoil with winglets; and 
           [0027]      FIG. 4  is a side view of an alternate embodiment of the stabilization hydrofoil with a split flap element shown in the down position; and 
           [0028]      FIG. 4A  shows a fairing guide, with the split flap is in the up position; and 
           [0029]      FIG. 4B  shows the split flap in the down position with lines indicating the flow of water; and 
           [0030]      FIG. 5  is a side view of a third alternate embodiment of the stabilization hydrofoil; with the addition of the pull-down mini foil device shown in the up position; and 
           [0031]      FIG. 5A  is a side view of a third alternate embodiment of the stabilization hydrofoil; with the addition of the pull-down mini foil device shown in the down position; and 
           [0032]      FIG. 5B  is a side view of a third alternate embodiment of the stabilization hydrofoil; with the addition of the pull-down mini foil device shown in the down position with lines indicating the flow of water; and 
           [0033]      FIG. 6  is a side view of an alternate embodiment of the stabilization hydrofoil with a mechanical split-flap positioning in view of the wedge designed split flap; and 
           [0034]      FIG. 6A  is a side view of an alternate embodiment of the stabilization hydrofoil with mechanical split-flap shown in the up (nested) position; and 
           [0035]      FIG. 7  (not included); and 
           [0036]      FIG. 8  shows the detail of the internal torque plates; and 
           [0037]      FIG. 9  shows close up detail of the torque plates exterior; and 
           [0038]      FIG. 10  is a flow diagram of the actuator system connected to the hydrofoils. 
       
    
    
     DETAILED DESCRIPTION 
       [0039]    While describing the invention and its embodiments various terms will be used for the sake of clarity. These terms are intended to not only include the recited embodiments, but also all equivalents that perform substantially the same function, in substantially the same manner to achieve the same result. 
         [0040]    As shown in  FIG. 1 , a schematic diagram of a vessel  10  provides a view of the components of the hydraulic control system used to actively reduce roll of the boat underway or roll at rest. Optionally, the computer control system may be configured to actively control and reduce pitch motion. Each of the two hydrofoils requires a corresponding system of an associated hydraulic control valve and hydraulic actuator for active mode. 
         [0041]    The operator control  100  is electrically connected to an active control computer  110 . The active control computer  110  is electrically connected to a motion sensor  120 . The active control computer system  110  is electrically connected to a hydraulic control valve  130 . For each hydrofoil the hydraulic control valve  130  is hydraulically connected to a hydraulic cylinder actuator  140 , utilizing hydraulic hoses. The hydraulic cylinder actuator  140  is mechanically connected to the hydrofoil  150 . The hydrofoil  150  is mechanically connected to a hull bracket  160 , which is attached mechanically to the hull transom  170  of the vessel  10 . The hydrofoil position-sensor  145  is mechanically connected to hydrofoil  150  and or the actuator  140 . The hydrofoil position-sensor  145  is electrically connected to the active control computer  110  for position feed back. 
         [0042]    As shown in  FIG. 2  a schematic diagram of a vessel  10  provides a view of the components of the system used to passively reduce the roll, pitch and yaw of the boat underway only.  FIG. 2  shows a close view of the hull transom  170  of the vessel  10  where the hydrofoils  150   p  (port) and  150   s  (starboard) are mounted to the hull bracket  160  in passive mode configuration. A positioning jackscrew  130  replaces the active hydraulic actuator  140 . 
       Multiple Embodiments of the Boat Stabilizer 
       [0043]    A multitude of hydrofoils are available to be mounted on the transom of the vessel. FIGS.  3 , 4 , 5 , 6  show alternate detailed embodiments of the boat stabilizers using the hydrofoils. 
         [0044]      FIG. 3  Single Foil Embodiment 
         [0045]    Now referring to  FIG. 3  is a close up view of one embodiment of the hydrofoil  150 . The vertical NACA foil  200  is constructed to have a rounded leading edge,  202   b . The leading edge  202   b  at the front tapers to a trailing edge  202   a  at the rear. As the boat moves forward, the vertical NACA foil  200  passes through the water. The NACA shape passively generates the force of lift in one direction. This lift force is directed outboard on each side of the vessel to passively reduce roll and yaw. This also allows for a greater turning rate at certain cruising speeds. 
         [0046]    The effect of the NACA shape allows for minimal drag associated with generating lift, and limits drag associated with the resistance of an object moving through water 
         [0047]    This lift force dampens uncomfortable roll and yaw since the boat must overcome this opposing lift force, to move out of a straight and level position related to the earth&#39;s horizon and compass heading. 
         [0048]    The minimization of the roll and yaw is also dependent on the mounted angle of the vertical foil  200 , which is manually adjusted by the installer. 
       Horizontal NACA Foil 
       [0049]    Still referring to  FIG. 3 . Attached on the bottom and perpendicular to the vertical foil  200  is a NACA shaped horizontal foil  230 . The foil is rounded at the front leading edge  232  of the foil and tapers to a blunt point on the rear trailing edge section  234  of the foil. 
         [0050]    The horizontal foil  230  is bent at the center. The bend line begins at the leading edge, at the center point, just forward of the leading edge of the vertical foil  200 , and continues to the point where the vertical foil trailing edge  202   a  terminates. Then it continues to the trailing edge  234  at center. The bend is approximately 10 degrees and serves four purposes:
       1) Serves to increase the design strength of the horizontal foil.   2) Provides a cupping component for use as a low to zero speed roll stabilizer.   3) Allows the installation technician to make directional control adjustments for the direction of upward lift.   4) Allows for greater clearance between the hull bottom and clear water flow, from the effect of disturbed water flow emanating from the hull bottom, trim tabs and fittings.       
 
         [0055]    Mounted on, and perpendicular to the ends of the horizontal foil  230  are two optional winglet foils  240   a  and  240   b . As depicted, these winglet foils have a modified triangular shape, but, they may be configured in a multitude of dimensions or not used at all, in favor of a rounded or squared off wing tip. The winglets increase lift and decrease drag. Second, the winglets aid in retaining water in a cupping action for use as a zero to low speed roll stabilizer. The winglet dimension above  230  is reduced for maximum effectiveness as a stabilizer at rest, so water may more efficiently flow off the top of the horizontal foil  230 . 
       Passive Design Effect 
       [0056]    The total hydrofoil  150  design prevents uncomfortable boat movement in passive mode, without the need for hydraulic actuation. This makes this design a cost effective solution for boat owners. Other competitive systems require hydraulic actuation to overcome uncomfortable boat motion. 
         [0057]    Passive stabilization occurs when the hydrofoil is attached to the hull and placed at a fixed angle of attack. The design configuration of the hydrofoil is effective enough to dampen vessel pitch, roll, and yaw without the need for hydraulic actuation. 
         [0058]    Active stabilization uses the hydraulic actuator and computer control system as previously shown in  FIG. 1 . Active stabilization provides for additional roll or pitch control by altering the angle of attack of the horizontal foil  230 . Based on the vessel motion sensor information provided to the onboard computer, control hydraulics will increase or decrease the lift force generated by the horizontal foil  230 . Active stabilization ads roll dampening effectiveness produced by the horizontal foil. Active stabilization also allows for roll or pitch stabilization at low to zero forward motion of the vessel. Active stabilization also allows for vessel attitude trim adjustments (e.g. when vessel loading affects the heel or pitch of the boat). 
         [0059]    As shown in  FIG. 3 , for active stabilization the hydraulic cylinder actuator  140  ( FIG. 1 ) is connected to the vertical NACA foil  200  using the hydrofoil&#39;s actuator mounting hole  220  located at the torque plates above the upper trailing edge of the vertical foil  200 . The vertical NACA foil  200  is connected to the transom of the boat at the hydrofoil-bracket mounting hole  210  utilizing a bearing assembly inserted in hole  210 . 
       Multiple Element Foil Embodiments 
       [0060]    Now referring to  FIG. 4 .  FIG. 4  demonstrates a close up view of a second embodiment of the hydrofoil  450 . 
         [0061]    The hydrofoil  450  is configured in the same manner as shown in  FIG. 3 . A split flap  350  is connected to the horizontal NACA foil  230 . The split flap  350  is connected via tie rods  330 , pivot arms  332 , and mounts  320 . 
         [0062]    A pivot arm  332  is connected to the split flap  350  on each side. The pivot arm  332  exists to change the position of the flap. A flexible joint  331  with stops is used to allow for the proper angle to maintain the split flap  350  in a neutral position, at high boat speed. 
         [0063]    During periods of high boat speed operation, an automatic computer controlled system (as depicted in  FIG. 1 ) pulls the split flap  350  down. This decreases the lift generated by the foil and flap assembly. 
         [0064]    Computer controlled actuation moves this split flap  350  into position as directed automatically utilizing a position feed back sensor  311  and hydraulic, pneumatic or electric actuation. 
         [0065]    Optionally the split flap  350  is adjusted to an effective position by mechanical means. Mechanical actuation moves this split flap  350  into an effective position as directed manually by the operator utilizing a position feed back sensor  311  reading as a reference. 
         [0066]    A limit stop  310  prevents the tie rod member from rotating past a desired set point. This set point is adjustable via an externally accessible set screw device. In addition to providing the result described above, the split flap operates differently when the stabilizer  450  is controlling motion while the boat is at rest or at low speed. 
         [0067]    This split flap  350  is used to increase and decrease cupping action at low to zero speed operation. Cupping action is increased when the horizontal foil moves in its downward stroke and cupping action is decreased in its upward stroke, since the flap falls away. This cupping action is similar to a swimmer using cupped hands to maintain body orientation while treading water. 
         [0068]    During active stabilization at low to zero speed, one horizontal foil is directed downward on the side of the boat that is rolling away from upright attitude. At the same time, the foil on the other side of the boat is moving up. The split flap  350  separates and moves downward to decreases cupping action, so water spills out freely. 
         [0069]    Now referring to  FIG. 4A  the split flap  350  is shown in the full up and nested position.  FIG. 4A  shows a winglet fairing guide  360  which provides a track guide  331   a  for the roller pin  331  to guide and support the pivot arm assembly  332 . The winglet fairing guide  360  also provides for protection and decreased parasite drag from the arm  332  and other components.  FIG. 4B  depicts water flowing through the split flap. 
         [0070]    Now referring to  FIG. 5 , which is a close up view of a third embodiment of the hydrofoil  550 . 
         [0071]    The hydrofoil  550  works both passively and or actively with hydraulic control. A second rigid member assembly  340  is added and connected to the split flap  350 . The second rigid member assembly  340  has a mini foil  344  connected to a lower strut  342 , which is connected to the split flap  350 . 
         [0072]    During periods of high speed operation, the force of the flowing water pulls the split flap  350  down, utilizing the lift force in the downward direction produced by the mini foil  344 . This decreases the lift generated by the foil  230  and flap assembly  350 , since there is less surface area on  230  to generate lift. 
         [0073]    This mini-foil  344  is composed of a lower NACA section. The mini-foil  344  is connected by a lower strut  342  to the split flap  350 . An adjustment  410  is provided to set the lower NACA foil  340  at an angle of attack which will pull the split flap  350  down at a desired speed. 
         [0074]    In automatic operation, the NACA foil  344  generates a downward lift force which automatically pulls the split flap away from the horizontal foil  230  at a moment when pressure on the flap is reduced during hydraulic actuation. Additional mini foil assemblies may be added to the split flap  350  end or mid section if needed. 
         [0075]      FIG. 5A  shows the split flap in the pulled down configuration. 
         [0076]    Both  FIGS. 5 and 5   a  shows a winglet fairing guide  360  which provides a track guide  331   a  for the roller pin  331  to guide and support the pivot arm assembly  332   
         [0077]    The fairing guide  360  also provides for protection and decreased parasitic drag from the arm  332 . 
         [0078]      FIG. 5   b  shows the flow of water between the Horizontal Foil  230  and the split flap. An arrow shows the direction of lift generated by the mini foil  344 . In this configuration the split flap  350  is producing zero lift and is trailing (ultra low drag). When the split flap  350  is producing zero lift forces, the mini foil  344  is able to hold the split flap  350  down. 
         [0079]    Alternate Foil Embodiment 
         [0080]    Now referring to  FIG. 6 ; as shown  FIG. 6  is a close up view of a fourth embodiment of the hydrofoil  650 . 
         [0081]    The hydrofoil  650  is shaped the same and works as is described in the single foil embodiment, both passively and or with active hydraulic control. 
         [0082]    Except now, a split flap  390  is connected to the horizontal foil  630 . The split flap wedge is connected via a tie rod  330 , arm assembly  332 , and mounts  320  as before on each side of the horizontal foil  630 . 
         [0083]    A pivot arm  332  is connected to the split flap  390 . The pivot  332  exists to change the position of the flap. A flexible joint with stops  331  is used to allow for the proper angle which will maintain the split flap in a neutral position. 
         [0084]    During periods of high speed operation, hydrodynamic forces pull the split flap  390  down. This decreases the lift generated by the foil and flap assembly, since there is less surface area to generate lift. This split flap differs in design in that the wedge shape  552  at the leading edge of the split flap  390  produces high enough pressure at the upper surface of the split flap  390  to hold it in the down position away from the lower NACA foil  230 . It is then locked in position until hydrostatic forces release the locking mechanism  331   d  at low speed. A manual cable (not shown) may also release the hydrostatic locking mechanism. 
         [0085]    For operator reference only, a position feed back sensor  324  is installed and electrically connected to provide a position reading at the operator panel. 
         [0086]    As in other embodiments, a limit stop prevents the tie rod member from rotating past a desired set point. This set point is adjustable via an externally accessible set screw device. In addition to providing the result described above, the split flap works in a completely different way when the stabilizer is controlling motion while the boat is at rest. 
         [0087]    At rest, this split flap is used to increase and decrease cupping action at low to zero speed operation. Cupping action is increased when the horizontal foil moves in its downward stroke and cupping action is decreased in its upward stroke. This cupping action is similar to a swimmer using cupped hands to maintain body orientation while treading water. During active stabilization at low to zero speed, one horizontal foil is directed downward on the side of the boat which is rolling away from its upright attitude. At the same time, the foil on the other side of the boat is moving up. The split flap separates and moves downward. This decreases cupping action, so water will spill away from the horizontal foil  230  more easily. 
         [0088]      FIG. 6A  depicts the split wedge flap configured in the up position. 
       Torque Plate Configuration 
       [0089]    Now referring to  FIGS. 7 and 8 . As shown in  FIG. 8 . a torque plate assembly  810  consists of a hole  210  for a steel or composite tube to be attached. Two holes  220  are provided to facilitate the attachment of the hydraulic cylinder rod end. 
         [0090]    The two torque plates  810  where the hydraulic cylinder attaches at hole  220 , merge at the bend-line to form a single vertical interior support. 
         [0091]    The foil shell surrounds the torque plate to form the NACA shape of the vertical foil  200 . 
         [0092]    The torque plate  810  now features an extended area forward of hole  220  to act as a position-stop against the hydraulic cylinder body. This prevents the hydrofoil from moving at a greater position than needed for yacht stabilization. It provides for a safety stop to prevent the hydraulic cylinder from retracting to a position which would cause the hydrofoil to induce extreme roll. A pad area  820  now exists to provide a safety stop against the hull mounting bracket  160 . It provides for a safety stop, to prevent the hydraulic cylinder from extending to a position which would cause the hydrofoil to induce extreme roll. 
         [0093]    Reinforcement (not shown) is added around the tube installed in hole  210  to improve durability. 
         [0094]    Now referring to  FIG. 9 .  FIG. 9  shows a close up view of the external area of the torque plate  810 . 
         [0095]    Control System Implementation 
         [0096]    Now referring to  FIG. 10 , a decision tree  700  is shown that indicates how the stabilization control system operates. The process of active boat stabilization is essentially the same for each type of hydrofoil  150 ,  450 ,  550  and  650 . 
         [0097]    The rate of roll sensor reading  710 , from the motion sensor  120 , indicates the direction and rate of vessel roll. 
         [0098]    If the vessel rolls to the left  730 , the actuator on the port hydrofoil  150 , 450 ,  550 , and  650  is pushed down (increasing lift) and the actuator on the starboard side hydrofoil  150 , 450 ,  550  and  650  is pulled up (decreasing lift). This movement is proportional to the electrical signal value from the roll rate sensor  710  which is proportional to the vessel rate of roll. Operator inputs and computer programming parameter values are available to attenuate this action. 
         [0099]    If the vessel rolls to the right  735 , the actuator pushes the starboard side hydrofoil  150 ,  550 ,  650 , down (increasing lift) and pulls the port side hydrofoil  150 ,  550 ,  650  up (decreasing lift). This movement is proportional to the electrical signal value of the roll rate sensor  710  which is proportional to the vessel rate of roll. Operator inputs and computer programming parameter values are available to attenuate this action. 
         [0100]    When roll has been stopped, both actuators move the hydrofoils to their neutral position. These actions work the same way regardless of vessel speed. However, the angle of the horizontal foil  230  will be greater at slower speeds and at rest.