Abstract:
An adjustable wake setting device for modifying a wake produced by a watercraft traveling through water. The system has a mounting member dimensioned and configured for attachment to the watercraft, a foil dimensioned and configured for movement between a stowed position adjacent the mounting member, out of the water, and an active area below the mounting member, in the water, such that the foil adjusts a relative position of the watercraft in the water thereby modifying the wake produced by the water craft traveling through the water, a linkage movably securing the foil to the mount, the linkage being dimensioned and configured for adjustably positioning the foil in the stowed position and the active area, an actuator mounted on the mounting member and connected to the linkage for moving the linkage such that the foil moves between the stowed position and the active area, and a controller for selectively actuating the actuator thereby selectively moving the foil between the stowed position and the active area. A method of using the adjustable wake setting device is also disclosed.

Description:
TECHNICAL FIELD 
   This invention relates, in general, to methods and apparatus for modifying wakes, and more particularly to remotely adjusting the wake behind powerboats towing wake boarders and water-skiers. 
   BACKGROUND OF THE INVENTION 
   In water sports, a typical tow boat is operated at speeds in excess of 15 mph. At these speeds, the boat hull creates a trailing wake with a low, turbulent middle developing near the stern of the boat. The outer edge of the wake forms a V-shaped lip with water outside the middle of the wake. 
   As a boat travels through the water, the stern of the boat hull lowers in the water and the bow rises at an angle of attack to oncoming water. The stern of the boat hull displaces water, which effectively creates the wake behind the boat. A heavier boat lying lower in the water will create a larger wake due to the greater water displacement. The shape of the hull also affects the wake shape and size. 
   While often referred to generically as “waterskiing” and “wake boarding”, water sports utilizing a tow boat generally encompass many different sports using skis, skates, boards, water foils, and even bare feet. With the advent of wakeboarding and trick skiing, the wake shape has become a more prominent component of the water-ski sports and tow boats. Many of these sports, especially wakeboarding, primarily focus on use of the wake to perform aerial maneuvers. 
   Typical wakeboards have a wide and flat form for sliding over the water surface. In comparison to water skiing or hydrofoil water sports, a wakeboarder is pulled through the water at a lower speed, typically in the range of 15–25 mph. 
   Wakeboarding and trick skiing enthusiasts, in particular, use the wake repetitively as a “ramp” by jumping over the wake. As such, the size of the wake is of primary concern for wakeboarders. As the sport has matured, wakeboard enthusiasts have developed increasingly complex tricks like spins, grabs, and flips. A larger wake allows wakeboarders to get more “air” when crossing over the wake, meaning that the rider can jump higher over the wake. 
   In order to increase the wake size, enthusiasts and boat designers have employed various techniques for lowering the stern of the boat and increasing wake size. One simple method is to place weights in the stern of the boat. Some tow boats have been designed specifically with additional weight in the transom for this purpose. The additional weight lowers the stern of the boat during towing and increases the size of the wake, however, there are several disadvantages to this method. The lowered floating position of the boat translates into slower cruising speeds. This is disadvantageous when the boat is used for cruising rather than skier towing. It can also be disadvantageous when one desires to use the same boat for pulling wakeboarders at slower speeds with a larger wake and skiers at high speeds with a small wake. One cannot increase or decrease the wake size and maintain a top cruising speed without stopping ashore to load or unload the weights. 
   Furthermore, the additional weight poses a safety risk. Every boat has a maximum load capacity, and the additional weight lowers the margin of safety. Typical weight additions can be from 800–1200 pounds. In a smaller boat, this additional weight combined to the passenger weight can be close to the maximum rated load-capacity. 
   Another class of boats has been developed to adjust the wake. These tow boats, known generally as “tournament boats,” have been developed for competitive skiing. The hull section of these boats are relatively flat such that minimal wake is produced at speed. The smaller wake is suitable for high-speed skiing and slalom competitions requiring precise turning patterns. Because these boats do not employ a deep V-shaped hull, they have lower top speeds typically under 50 mph. These boats are said to run “wet,” meaning that they have high drag from the added area contacting the water surface. Tournament boats also employ control devices for changing the size of the wake. Several devices have been employed to balance the need for less drag with a smoother wake. An example of such a control device is disclosed in U.S. Pat. No. 5,549,071. Generally, these devices and designs minimize the wake size, which is not desirable for wakeboarding and trick skiing. 
   In contrast to tournament boats with smooth wakes, some boats have a hull designed with a deep deadrise. A deep deadrise creates a larger wake preferable for trick skiing. However, all the hull designs require a tradeoffs between speed and wake size. 
   U.S. Pat. No. 4,915,048 to Stanford discloses a submerged hydrofoil device for adjusting the trim and stability of a tow boat. The hydrofoil is also integral to the boat design and cannot be retracted for cruising. Norwegian patent no. 86,945 to Troenge is directed to a retractable stern-mounted foil. However, similar to the Stanford patent, Troenge is directed to improved stability and not adjustment of the wake size. Both patents are directed to adjusting and balancing the pitch and yaw forces and angle of attack of the tow boat. 
   Some submerged hydrofoil devices have been employed specifically to increase wake size. These hydrofoil devices increase downforce on the boat hull and in turn increase the wake size. Fixed hydrofoil devices are limited in that they do not allow for adjustment of the wake size; the single position of the hydrofoil allows for only a single wake size at a particular speed. In particular, known hydrofoil devices either require manual removal of the hydrofoil at cruising speed or they cannot be removed at all. If removable, these devices require manually removing the hydrofoil. If the hydrofoil is not retracted, it decreases the top speed of the boat. Thus, known hydrofoil devices are fixed or cannot be easily adjusted between cruising and towing conditions. 
   Newer methods have been devised which allow for increasing the wake size at tow speed without sacrificing cruising speed. One such method uses of an inflatable bladder. When towing riders, the bladder can be filled with water to increase weight in the stern of the boat. At cruising speeds, the water in the bladder can be excreted out of the boat. This device has the limitation of requiring users to wait for the bladder to be filled and emptied and also has limited adjustability. Moreover, the increased weight of the bladder also lowers the loading margin of safety as discussed. 
   What is needed is a method and apparatus that allows adjustable wake modification while overcoming the above-mentioned disadvantages. 
   BRIEF SUMMARY OF THE INVENTION 
   In summary, one aspect of the present invention is directed to a wake modifying system for modifying a wake produced by a watercraft traveling through water. The system has a mounting member dimensioned and configured for attachment to the watercraft, a foil dimensioned and configured for movement between a stowed position adjacent the mounting member, out of the water, and an active area below the mounting member, in the water, such that the foil adjusts a relative position of the watercraft in the water thereby modifying the wake produced by the water craft traveling through the water, a linkage movably securing the foil to the mount, the linkage being dimensioned and configured for adjustably positioning the foil in the stowed position and the active area, an actuator mounted on the mounting member and connected to the linkage for moving the linkage such that the foil moves between the stowed position and the active area, and a controller for selectively actuating the actuator thereby selectively moving the foil between the stowed position and the active area. 
   The active area may include a plurality of active positions, wherein each active position of the foil modifies the wake in varying degree. The plurality of active positions of the foil may be incrementally spaced within the active area. The actuator may be a step motor configured for moving the foil between the incrementally spaced active positions. The mounting member may be mounted to a transom of the watercraft. 
   The actuator may include at least one linear actuator having one end pivotally attached to the mounting member and another end pivotally attached to the linkage, and, the controller may be configured to output a control signal to the at least one linear actuator such that the actuator moves the linkage to move the foil between the stored position and active area. The controller may be configured for control by a user within the watercraft. 
   The controller may be configured to control the actuator in response to one or more operational parameters of the watercraft. The controller may be configured to prohibit the actuator from moving the linkage and foil between the stored position and active area unless speed of the watercraft may be less than a predetermined threshold speed. The predetermined threshold speed may be approximately 10 miles per hour. The controller may be configured to allow the actuator to move the linkage and foil between a plurality of active positions within the active area when the speed of the watercraft may be above the predetermined threshold speed but below a predetermined maximum speed. The predetermined maximum speed may be approximately 25 miles per hour. The controller may be configured to prevent the actuator to move the linkage and foil between a plurality of active positions within the active area when the speed of the watercraft may be greater than approximately 10 miles per hour. The controller prohibits the actuator from moving the linkage and the foil when the speed of the watercraft may be approximately zero. 
   Another aspect of the present invention is directed to a wake modifying system for modifying a wake produced by a watercraft moving through water. The system includes a mounting body, the mounting body being configured to be secured to the watercraft, a linkage including an arm being pivotably attached at an upper end thereof to the mounting body, a water foil attached to a lower end of the arm, the water foil being dimensioned and configured for movement between a stowed position adjacent the mounting body and an active area below the mounting member, the water foil being configured for enhancing the wake produced by the moving watercraft, and an actuator pivotably attached at one end to the mounting body and pivotably attached at another end to the arm adjacent the upper end. The actuator may be configured for positioning the arm and the water foil in response to a control signal. 
   The mounting body may be secured to a transom of the watercraft. The linkage may include a pair of arms, each arm being pivotably attached at an upper end thereof to the mounting body and attached at a lower end thereof to the water foil, wherein the actuator may be configured to stow between the pair of arms when the foil may be in the stowed position. In the stowed position, the actuator may be positioned substantially within a cavity formed by the mounting body and the pair of arms, and the foil may be positioned aft of the mounting body. The mounting body may include a forward mounting plate, opposing sidewalls extending from side edges of the mounting plate, each sidewall having a pivot point for pivotal attachment of a respective one of said arms, and a top member extending from an upper edge of the mounting plate and interconnecting the sidewalls. A rear portion of the top member may form an attachment portion to which the actuator may be pivotably attached. 
   The water foil may have a leading edge and trailing edge, and the leading edge may extend along a transverse axis at a sweep angle. The water foil may have a non-planar cross-section configured for producing downforce when in the active area and moving through water. The water foil may be dimensioned and configured to be positioned between 0 degrees and 45 degrees relative to the longitudinal axis of the watercraft. A fore-and-aft dimension of the arms may be substantially less than a fore-and-aft dimension of the water foil. 
   Yet another aspect of the present invention is directed to method of modifying a wake produced by a watercraft moving through water. The method may include one or more of the steps: providing a water foil dimensioned and configured to adjust the relative position of the watercraft moving through water relative to the waterline; providing an actuator to move the water foil from a stored position out of the water to an active area within the water, wherein the relative angle of the water foil within the active area varies the amount of adjustment of the relative position; and remotely controlling the actuator to selectively move the water foil. 
   The method may further include incrementally controlling the relatively angle of the water foil within the active area to modify the wake in varying degree. The remotely controlling step may be accomplished by a user controlling the actuator remotely from within the watercraft. The remotely controlling step may be accomplished by automatically controlling the actuator in response to one or more operational parameters of the watercraft. The method may further include prohibiting the actuator from moving the linkage and foil between the stored position and active area unless speed of the watercraft may be less than a predetermined threshold speed. The method may further include allowing the actuator to move the linkage and foil between a plurality of active positions within the active area when the speed of the watercraft may be above the predetermined threshold speed but below a predetermined maximum speed. The method may further include allowing the actuator to move the linkage and foil between a plurality of active positions within the active area when the speed of the watercraft may be greater than approximately 10 miles per hour. The method may further include preventing the actuator from moving the linkage and the foil when the speed of the watercraft may be approximately zero. 
   The method and apparatus for modifying wake of the present invention has other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated in and form a part of this specification, and the following Detailed Description of the Invention, which together serve to explain the principles of the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a wake modifier in accordance with the present invention, the apparatus shown mounted on a boat. 
       FIG. 2  is schematic view of an instrumentation and control system for controlling the wake modifier of  FIG. 1 . 
       FIG. 3  is a perspective view of the wake modifier of  FIG. 1 . 
       FIG. 4  is a cross-sectional side view of the wake modifier of  FIG. 1 . 
       FIG. 5  is a perspective view of the wake modifier of  FIG. 1 , illustrating a stowed position. 
       FIG. 6  is a cross-sectional side view of the wake modifier of  FIG. 1  in the stowed position of  FIG. 5 . 
       FIG. 7  is perspective view of the wake modifier of  FIG. 1  illustrating variability with a plurality of operating positions. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to those embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. 
   For convenience in explanation and accurate definition in the appended claims and detailed description, the terms “up” or “upper”, “down” or “lower”, “inside” and “outside”, “fore” or “forward” and “aft” are used to describe features of the present invention with reference to the positions of such features as displayed in the figures. 
   While reference will be made to towing a wakeboarder, it will be understood that the present invention can be applied to all manner of watersports where it is desirable to increase and adjust or otherwise modify the wake of a watercraft. 
   Referring to  FIGS. 1 and 2 , a wake modifying system, referenced by the numeral  32 , generally includes a wake modifying device  34  having a foil assembly  35  adjustably mounted on a stern end  37  of a watercraft  39 . The wake modifying device includes an actuator  41  for adjustably setting the position of the foil assembly, which actuator is remotely controlled by a control system  42  mounted within the watercraft. The wake modifying system allows the boat operator to adjust the trailing wake of a watercraft thus allowing the boat operator to enhance the recreational enjoyment and challenges for a wakeboarder being towed by the boat. 
   With reference to  FIG. 1 , the watercraft has a hull bottom  44  from which a propeller shaft  46  extrudes to drive propeller  48  in a conventional manner. A rudder  49  is mounted from the hull and adjacent the drive propeller in a conventional manner. The hull of power boats are typically V-shaped formed by generally symmetrical sides  51  converging along a longitudinal axis of the watercraft. As the watercraft moves through and displaces water, a wake is formed aft of the stern end transom  53  of the watercraft. As briefly discussed above, the shape of the hull and the depth at which the hull moves through the water effects the shape and size of the wake. 
   The control system includes a controller  55  that is operationally connected to actuator  41  of the wake modifying device and a control input  56  to control the position of the foil assembly. The control input may take the form of a toggle switch, control lever, push button or other suitable means. In the illustrated embodiment, the controller is also connected with an instrumentation panel  58 , which displays data from the onboard control and diagnostics system of the watercraft, as shown in FIG.  2 . The instrumentation panel may include information such as fuel level, watercraft speed, engine speed and other conventional information useful in the operation of the watercraft. In accordance with the present invention, the instrumentation panel may also include information about the wake modifying system including the status thereof. For example, a status gauge  60  may be provided to inform the operator of the position of the foil assembly. One will appreciate, however, that the controller need not be connected to the watercraft electronics and may, instead, be discrete from the controls and instrumentation of the watercraft. Controller  55  may take the form of any processor controller including, but not limited to, a central processing unit (CPU) that is independent of, or integral with, the control system of the watercraft. 
     FIG. 4  shows a detailed view of the wake modifying device  34  of  FIG. 1 . In the illustrated embodiment, a mounting member or body  62  is mounted to the stern end transom  53  of watercraft  39 , which is at the rear of watercraft  39 . Mounting body  62  is formed by a top member  63 , sidewalls  65 , and a mounting plate  67 . Mounting body  62  may be a monolithically formed component or may be separate pieces welded or fixed together by other suitable means. In the illustrated embodiment, the mounting body is formed of stainless steel, however, one will appreciate that other suitable materials may be used including, but not limited to, aluminum, aluminum alloys, composites, and other suitable materials. The illustrated embodiment also includes substantially closed planar members, however, on will appreciate that other suitable members may be utilized to provide the appropriate framework for movably mounting the foil assembly to the stern of the watercraft. 
   Mounting plate  67  mounts the mounting body to watercraft  39 . Opposing sidewalls  65  extend from side edges of the mounting plate. Top member  63  extends rearwardly from an upper edge of the mounting plate and are affixed to at least a portion of upper edges of the sidewalls. A rear portion of top member  63  is provided with rearward attachment flanges  69  for pivotally supporting actuators  41 , while a portion of each sidewall  65  is provided with a pivot  70  for pivotally supporting foil assembly  35 . In the illustrated embodiment, the pivot is formed with a through-bolt, however, one will appreciate that other suitable means may be utilized. Pivot  70  is preferably at a lower end of the sidewalls to maintain foil assembly  35  as low as possible. Additionally, locating the pivot point lower than the attachment flanges creates a configuration whereby actuators  41  can be utilized to apply an extension force versus pulling force. Furthermore, such configuration subjects the actuators to compressive forces as opposed to tension forces during operation. 
   The foil assembly, generally designated  35 , is movably secured to mounting body  62  and includes a pair of arms  72  and a water foil  74 . In the illustrated embodiment, the foil assembly is formed of stainless steel, however, one will appreciate that other suitable materials may be used including, but not limited to, bronze, aluminum, aluminum alloys, composites, and other suitable materials. The arms each have two openings at an upper end thereof for receiving a respective through-bolt to provide a pivotal connection between the arm and the mounting body. Further, upper ends of the arms are interconnected by a transverse bracket  76  including forward attachment flanges  77  secured to forward ends of actuators  41 . The illustrated transverse bracket is affixed to the upper ends of the arms by bolts, welding, or other suitable means. One will appreciate, however, that the transverse bracket may be integral with, and/or monolithically formed with the arms. 
   In the illustrated embodiment, the forward attachment flanges are provided with similar fasteners (best seen in  FIG. 3 ) to provide a pivotal connection between the actuators and the transverse bracket. As noted above, actuators  41  are pivotably secured to the mounting body  62  at an opposite end thereof. Actuators  41  are preferably linear actuators including electric motors, however, one will appreciate that other suitable actuators may be employed to move foil assembly  35  including, but not limited to, hydraulic and pneumatic motors. Actuators  41  allow for adjustably positioning foil assembly  35  between a deployed position, as shown in  FIGS. 3 and 4 , and a stowed position, as shown in  FIGS. 5 and 6 . In addition, actuators are also configured to position the foil assembly within a plurality of deployed positions in the flow of water, as will be discussed in greater detail below. 
   As actuators  41  extend or contract, arms  72  rotate about pivots  70 . Such a configuration creates a fulcrum point about the pivot, however, alternative structures are envisioned. The pivots can be located anywhere along mounting body  62  or at ends of arms  72  to adjust the rotating motion of the arms. The arms may also be formed by a multibar linkage or replaced with other components suitable for effecting movement of the water foil. Use of a mounting body  62  instead of direct attachment of foil assembly  35  to watercraft  39  is preferable over attaching pivot points directly to the watercraft to alleviate concentrated stresses on the walls of the watercraft as well as to provide a discrete device which may be installed on a watercraft as an original equipment device or as an aftermarket device. 
   In the illustrated embodiment, two arms  72  are utilized, however, one will appreciate that two, three, four or more arms may be used. The two arm configuration allows each arm  72  to be offset from a longitudinal axis aft of the propeller and the rudder thereby minimizing any negative effects on propulsion and steering. Use of at least a pair of arms  72  also allows for a more rigid structure which is better suited to handle torsional and transverse forces on the foil assembly. The illustrated embodiment having a pair of arms advantageously allows for adjustably positioning the foil assembly and withstanding reactionary forces with minimal materials. 
   In the preferred embodiment, arms  72  are streamlined and have minimal cross-sections to reduce drag and to avoid deleterious effects on steering. In particular, the fore-to-aft dimensions of the arms, when in the deployed position, is minimal to prevent the arms from having a rudder-like effect. In the illustrated embodiment, the arms have a narrow foil-shaped cross-section in order to minimize turbulence across the arms and promote maneuverability. An irregular or blunt shape of the arms may create air pockets aft of the arms  72 , which in turn move across foil  74  and obviate its effectiveness. An irregular flow of water across the arms  72  may also create a whistling sound. Likewise, if the arms are excessively wide, the arms may counter the steering of the rudder  49 . Therefore, the arms preferably have a shape that promotes laminar flow and minimizes the disruption of water flow. 
   Foil  74  is secured to a lower end of arms  72 . In the illustrated embodiment, the arms are attached to foil  74  at an angle of approximately 75°, but one will appreciate that the actual angle between the arms and the foil may depend on the overall configuration of the wake modifying device. As best shown in  FIG. 3 , with foil assembly  35  in an active or deployed position, foil  74  faces an incoming water flow at an attack angle α. When the arms are rotated all the way down with actuators  41  fully retracted, an attack angle α of foil  74  is approximately 1° to 7° with respect to the longitudinal axis of the watercraft and the horizontal, preferably within approximately 3° to 5°, and most preferably approximately 4°. The angle between arms  72  and foil  74  is approximately 13–15°, preferably 14°. It has been found that with the above-described configuration and a 14° attachment angle the foil tends to move downward and establish equilibrium adjacent the lowest active position. Thus, at speed, the force on actuators  41  will be compressive even with foil  74  in an active position. 
   Foil  74  has a leading edge  79  and trailing edge  81 . When water foil  74  is in an active position below the surface of the water, the leading edge enters the flow of water first. A transverse axis is formed through opposite corners of the leading edge. As shown in  FIG. 4 , the leading edge preferably extends along the transverse axis at a sweep angle θ in order to decrease drag when watercraft  39  is moving. Sweep angle α is preferably within the range of approximately 4°–12°. 
   In some embodiments of the present invention, water foil  74  has a non-planar cross-section configured for producing downward force when moving in the flow of water. Applying known methods employed in aeronautics and fluid dynamics, the shape of water foil  74  can be designed to create amplified downforce or negative lift. 
   Water foil  74  can be positioned in a stowed position, as shown in  FIGS. 5 and 6 , as well as a plurality of positions in the active area of the water flow, as shown in  FIG. 7 . When water foil  74  is in the stowed position, actuators  41  are fully extended between arms  72  and the rearward attachment flanges on mounting body  62 . In the stowed position, foil assembly  35  and actuators  41  have a compact profile. In the preferred embodiment, actuators  41  and arms  72  are designed to collapse and fit substantially within a cavity formed by mounting body  62 . In the stowed position, extended actuators  41  extend from the pivot points of forward attachment flanges  77  on the foil assembly rearward to the attachment flanges on the rear end of the mounting body. Thusly, as the actuators expand, the actuators rotate foil assembly  35  such that water foil  74  is positioned adjacent mounting body  62 . Foil assembly  35  is preferably designed to allow foil  74  to stow aft of mounting body  62  in the stowed position to minimize air drag by foil  74 . The compact profile also decreases the obtrusiveness of foil  74  in the stowed position. 
   Additionally, wake modifying device  34  is preferably mounted as close to the hull bottom  44  as possible and below a swim platform mounted on the swim platform mounts in an conventional manner. When watercraft  39  is moving, the water level will be near hull bottom  44 . However, at idle, the water level will rise above the hull bottom and thus submerge wake modifying device  34 . Generally, the space between the hull bottom and swim platform is in the range of ten to twelve inches. 
   Turning now to operation and use, controller  55  is configured to respond to inputs from the watercraft operator and/or to the onboard electronics of the watercraft. One will also appreciate that the controller may be configured to be operated by a remote user such as the wakeboarder and/or an observer traveling with the watercraft operator. Controller  55  is preferably programmed with predetermined parameters for added safety and reliability of the wake modifying system  83 . According to these predetermined parameters, controller  55  outputs a control signal to actuators  41  in response to operational data of watercraft  39 , which can be from the onboard electronics and/or operator inputs. 
   In one embodiment, the controller is configured to prevent movement of foil assembly  35  while a motor of watercraft  39  is idling or near idle, or if the watercraft is not moving. For example, the controller may be configured to prevent movement of the foil assembly unless the engine of the watercraft is operating above 1000 RPM. Preventing motion of the foil assembly  35  in such conditions may serve to prevent risk of injury to swimmers who are entering or exiting the watercraft. Thusly, in the this embodiment, controller  55  will send a control signal, or prohibit a control signal, to actuators  41  thus leaving the foil assembly motionless when the speedometer reads nearly zero or the engine is idling or off. 
   In operation and use, an operator can select a position for foil assembly  35  using control input  56  in a remote location, preferably on or adjacent the instrument panel  58 . Preferably, the system is provided with an audible alarm that sounds when the foil assembly is being deployed from or retracted to the stowed position. In order to reduce the likelihood of injury, controller  55  is preferably programmed to prevent movement of foil assembly  35  from the stowed position of  FIGS. 5 and 6 , to the deployed positions of  FIGS. 3 and 4  and/or the intermediate positions of  FIG. 7  unless watercraft  39  is moving less than a threshold speed. In the illustrated embodiment, the threshold speed is about 10 miles per hour. This condition serves to prevent positioning the water foil in the water in excessive attack angles (e.g., greater than 45° to the longitudinal axis of the watercraft and to the horizontal) in order to keep the drag forces on the foil assembly within acceptable levels and prevent the watercraft from porpoising. 
   When towing a wakeboarder, an operator may select a position for the foil assembly  35  to modify the wake. Preferably, foil assembly  35  may be positioned at a plurality of angles within the active area, which active area extends from the fully deployed position of  FIGS. 3 and 4  to an angle of approximately 45° to the longitudinal axis and to the horizontal. Preferably, the foil assembly can be positioned in the fully deployed position and in four, five or more intermediate positions within the active area. In such cases, the actuator may be in the form of a linear actuator having a step motor configured to position the foil assembly in the intermediate positions. More preferably, the actuator and controller are configured to position the foil assembly at any angle within the active area. 
   When the foil assembly  35  is placed in an active position, the flow of water imparts a force upon a top surface  83  of the foil  74 . The reactionary force on the top surface imparts a downward force through arms  72  and through mounting body  62  and, in turn, causes the stern end  37  to be forced downward relative to the waterline. This, in turn, causes the stern to set lower in the water and to displace more water thus increasing the size of the wake. It has also been found to advantageously change the shape of the wake. Thus, the relative position of the stern of watercraft  39  can be adjusted thereby adjusting the wake of the boat on the fly, and without stopping to adjust weight distribution within the watercraft and/or to manually adjust watercraft accessories. 
   In the preferred embodiment, controller  55  is preset to only allow movement of foil assembly  35  under preset conditions to prevent failure of control system  83 . Controller  55  preferably will not allow movement of foil assembly  35  between a stowed position and an active area when watercraft  39  is moving less than a predetermined threshold speed. In the preferred embodiment, the threshold speed is about 10 miles per hour. This condition prevents a user from lowering foil  74  from a stowed position into a flow of water at high speeds and potentially damaging wake modifying system  83 . However, foil assembly  35  may be moved from an active area to the stowed position when watercraft  39  is below the predetermined threshold speed. 
   Additionally, controller  55  is preset to allow a user to select a position for foil assembly  35  when watercraft  39  is traveling within a certain speed range, preferably in the range of approximately 10 to 40 miles per hour. By setting an upper speed limit for actuation of foil assembly  35 , the reliability of wake modifying system  83  may be increased. Furthermore, limiting adjustment of foil assembly  35  to speeds below approximately 40 miles per hour may lessen risk of damage to the wake modifying system and minimizes deleterious effects on handling. 
   Thus, in operation and use, a user can actively place the foil assembly into an active position for adjusting the wake for trick riding. When watercraft  39  is being used for cruising and traveling, foil assembly  35  can be alternatively raised to a stowed position for greater maximum speed and stability. In the illustrated embodiment, controller  55  will however override the user&#39;s input according to the foregoing operational conditions. 
   Additionally, the controller may be configured such that the foil assembly automatically moves to the stowed position as the watercraft is loaded on a trailer as well as in other applications outside of the water. 
   The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.