Multifunctional hydrofoil surfboard

Abstract

The invention relates to water sports and methods for manufacturing the devices and has applicability to surfboard like devices having two or more turning, lifting and planning hydrofoils that optionally can combine or separate the functions of riding a wave that includes but is not limited to, 1. a fully lifted or hull out of the water foiling state, 2. with a partially lifted hull and foils lifting and planning state and or, 3. an enhanced maneuvering state with the foils and hull in a low to non lifting or lifted state. The performance and control features inherent in this invention achieve one or combinations of one or more of the desired riding states while enhancing the speed and maneuverability for turning, lifting and planing the surfboard and rider. The watercraft of this invention has internally located structural elements for the physics of the foil fins and the rider.

Description

This patent application claims the benefit of provisional patent APPL No. 60/643,506 filed Jan. 13, 2005, inventor J. Michael Caldwell.

BACKGROUND OF THE INVENTION

The invention relates to water sports and methods for manufacturing the devices and has applicability to surfboard like devices having two or more turning, lifting and planning hydrofoils that optionally can combine or separate the functions of riding a wave that includes but is not limited to, 1. a fully lifted or hull out of the water foiling state, 2. with a partially lifted hull and foils lifting and planning state and or, 3. an enhanced maneuvering state with the foils and hull in a low to non lifting or lifted state. The performance and control features inherent in this invention achieve one or combinations of one or more of the desired riding states while enhancing the speed and maneuverability for turning, lifting and planing the surfboard and rider. The watercraft of this invention has internally located structural elements for the physics of the foil fins and the rider.

The function and advantages of this invention are to enable the rider to achieve greater speed and maneuverability in all modes of the devices use. The intended uses include wave riding and flat water riding. This device may be paddled into ocean waves by the rider or the rider may be towed by motor boat or jet ski into the wave or on flat water.

A surfboard, ridden standing and employing two or more hydrofoils fixed to the underside rear portion of the surfboard. Two or more of the hydrofoils positioned off center of the centerline of the surfboard and optionally one or more on the centerline of the craft provides the stability and control requirements of this device for the dynamics found on a waves face. This devices configuration, has improved speed and maneuverability with superior stability, ease of control, in comparison with presently existing similar craft.

A modern surfboard with its highly rockered or curved bottom shape, when combined with inefficient small flat sided steering fins that are positioned to point at the surfboards nose, is designed to be constantly “pump-turned” to attain speed and maneuverability. The concept of a hydrofoil wing pitch control aspect or the nose of the board being elevated or lowered during maneuvers to achieve new speed and turning controls is a new feature of this device for the water sports marketplace. The potential forces of the wing on the board and rider are significantly greater than those forces experienced with current steering or maneuvering fin systems. The results of these point or localized forces on the surfboard can require very specialized reinforcements and construction materials to be used in the design and manufacturing of the surfboard hull and wing foil assembly attachment areas. These specialized reinforcements or suspension subassemblies are described and shown in detail in the following sections titled

DETAILED DISCRIPTION OF THE INVENTION AND DRAWINGS

In related U.S. Pat. No. 6,736,689 a structural subassembly is provided to produce an aquatic gliding board. The subassembly includes a hollow inner shell, which is covered with a casing made of foam capable of being machined. The invention also relates to a method of making such a subassembly and to a board made by covering the preceding subassembly with a layer of resin-coated fibers.

In many related U.S. patents such as U.S. Pat. Nos. 5,807,152 and 5,921,833 additionally U.S. Pat. No. 4,964,825 and U.S. Pat. Nos. 6,652,340, 5,062,378 and 5,309,859 have various structural elements structural subassemblies and a number manufacturing methods are provided to produce watercraft boards. Some of these patents describe hydrofoil devices. These inventions relate materials and methods of making such watercraft and subassembly and to a board made by covering the subassembly with layers of various materials including resin-coated fibers.

A number of patents have been granted by the United States Patent Office for hydrofoil-based surfboards, beginning with a patent granted to Morgan (U.S. Pat. No. 3,747,138) in 1973. According to Morgan, a hydrofoil surfboard with a pair of centerline mounted hydrofoils or one rear hydrofoil used in combination with Ramos hull step would achieve enhanced speed and control on the wave face. The stability requirements of this configuration are unsuitable for the dynamic conditions found on a wave face and would not provide the intended results. This is due in part to the centerline placement of the hydrofoils not providing sufficient stability for the rider. However, examination of these designs suggests than the inventors may have failed to fully appreciate that these craft will be operated on an inclined, and compound curved sea surface. As a result, the speed potential of the craft is compromised, and the craft can have substantial stability, control, and maneuvering deficiencies.

At the present time, there appears to be only one hydrofoil-based surfboard design that is being successfully ridden on ocean waves. It utilizes a hydrofoil assembly originally developed for a water sports device towed by a powerboat over flat and level water. This device is disclosed in U.S. Pat. No. 5,100,354 (granted to Woolley and Murphy in 1992), with improvements disclosed in a number of subsequent patents.

In order to ride a wave, the surfer first “catches” it (i.e. attains a speed in the direction of motion of the wave that is in excess of the wave speed before reaching the crest of the wave). Traditionally he accomplishes this by paddling while simultaneously utilizing the forward thrust of the sloping wave face on his surfboard as the wave passes under him. However, waves and riders move at relatively slow speeds in relation to the potential of a hydrofoil surfboard therefore the hydrofoil surfboard rider may be towed into the wave to first achieve full flight conditions and therefore the highest speed and then release once on the wave. This condition provides the starting point for accelerated wave maneuvers with the potential for extreme air or above the wave opportunities due to the increased speed and duration of this speed and maneuvering opportunity.

A fairly recent development in big wave riding is the use of a power craft (especially a “personal water craft”) to tow the surfer onto the face of the wave to be ridden. At that point, the rider can release the tow handle and ride the wave propelled solely by the sloping face of the moving wave and the force of gravity. With this initial assist by the power boat, much bigger waves can be ridden than is possible by paddling and the design of the multifunctional hydrofoil surfboard can be tailored to handle the high speeds that occur. Longer vertical foil struts with ultra high lift foil sections with reduced areas would be used to reduce the penalties and compromises previously experienced by the riders particularly related to the speed and choppy water surface conditions.

Once the wave has been “caught”, a typical ride consists of traversing across the face of the wave while pursued by the progressively breaking crest. Thus the success of completing a ride without being overtaken and impacted by the breaking crest requires that the speed of the board and rider must equal, or exceed, the speed of progression of the breaking crest. This device both achieves the speed and control requirements stated above.

Hydrofoil-based watercraft has long been recognized to have the potential to enhance performance and provide a smooth ride in choppy waters. Therefore the hydrofoil-based surfboard device of this invention offers significant advantages for the big wave rider in comparison with more traditional although specialized surfboards presently used in big wave surfing.

The hydrofoil wave-riding foil boards that are presently being ridden were developed by a group of big wave riders in Hawaii. The craft consists of the hydrofoil assembly described above, but with a specially modified and strengthened board that resembles a snowboard. The foil board is ridden with the rider standing on the board. A pair of snowboard bindings is fastened to the hull with the feet facing transversely to the longitudinal axis. The bindings are centered over the longitudinal axis of the craft, and separated from each other in the fore and aft direction with the rear binding positioned almost directly over the strut.

Although there may be exceptions in certain situations, in general, fully submerged hydrofoils are more hydro dynamically efficient than are surface-piercing foils and thus offer the greatest speed potential an important factor for a big wave rider. However, a fully submerged foil is inherently unstable in both pitch and roll. A properly designed pair of surface-piercing foils separated from each other along a horizontal axis (transverse to the longitudinal axis) of the craft can be made to be stable in roll and pitch (at least for small deviations from the equilibrium trim), but the elevation of the hull above the sea surface must still be controlled by the rider. Hence the rider of such a craft must control the pitch angle of the craft, balance the craft in roll, and initiate and coordinate rotations in pitch, roll, and yaw, in order to maneuver on the sea surface. He accomplishes this by shifting his body weight fore-and-aft, and from side-to-side, and by torsional rotations of his body segments (e.g. upper torso). The rider can control the partial planning configuration of his board by the same motions, but in addition he can use the hull to further facilitate control. Thus he has a powerful alternative or supplemental means of control to weight shifting.

BRIEF DISCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The invention and the individual elements will be better understood from the description that follows, with reference to the drawings, in which:

FIG. 1 is a top view of a structural flex member and attached fin receiving boxes;

FIG. 2 is a side view of a structural flex member and attached fin receiving boxes;

FIG. 3 is a bottom view of a structural flex member and attached fin receiving boxes;

FIG. 4 shows a top view illustrating view line C-C of the subassembly according to an embodiment of the invention,

FIG. 5 shows a cross-sectional view C-C of the subassembly according to an embodiment of the invention, with a main tube structure for flex controlling and structurally reinforcing beneath the feet of the user and the forward and rear curved panels;

FIG. 6 shows an alternative cross-sectional view of the molded watercraft and the honeycomb outer shell and the watercraft containing the structural subassembly thru the section line C-C in FIG. 4 according to an embodiment of the invention

FIG. 7 shows a perspective of multifunction hydrofoil fin incorporating the inner and outer lower wing structure as viewed from a position on the left side and slightly below the fin.

FIG. 8 shows a frontal view of multifunction hydrofoil fin incorporating the inner and outer lower wing structure;

FIG. 9 shows a perspective of multifunction hydrofoil fin as viewed from a position on the left side and above the fin incorporating the inner and outer lower wing structure

FIG. 10 shows a perspective of a center multifunction hydrofoil fin incorporating the inverted “Y” lower wing structure as viewed from a position forward of the fin;

FIG. 11 shows a center multifunction hydrofoil fin incorporating the inverted “T” lower wing structure as viewed from a position forward of the fin;

FIG. 12 shows a rear view of a number of progressively smoothly warping and smoothly curving multifunction hydrofoil fins;

FIG. 13 shows a perspective view of the of the subassembly according to an embodiment of the invention, with a main tube structure for flex controlling and connecting the fin receiving boxes, additionally FIG. 13 shows the centrally located tube like structure connecting device that structurally reinforces the watercraft beneath the feet of the user.

FIG. 14 shows a perspective view of the of the fins section thickness and the fins cord lines;

FIG. 15 shows an example of a fin planform;

FIG. 16 shows a graph example of a fin smoothly bending in the mid-plane of the foil;

FIG. 17 showing an example of a smoothly warping foil through the difference in depth between the leading and the trailing edges of the foil along the depth of the foil;

FIG. 18 showing the chord in relationship to the vertical position along the foil;

FIG. 19 shows an example of the difference in change in yaw angle along the span of the foil;

FIG. 20 shows an example of the difference in change in pitch angle along the span of the foil;

FIG. 21 shows a perspective view example of the smooth warped and smooth curved foil with attached wing;

DETAILED DISCRIPTION OF THE INVENTION

The objective of the design is to optimize the craft for speed, maneuvering and control when riding on the inclined and curved faces of ocean waves and optimize the craft for use on a flat, horizontal water surface when towed by a powerboat. To the maximum extent possible, this optimization will be done though selection of components with specific hydrodynamic characteristics, and said craft will be controlled by the rider by weight shifting and torsional rotations of his body. However, an enhanced version of the craft is also disclosed in which the rider obtains additional control and performance capabilities via a movable foil surface whose position among a plurality of rotational positions is controlled by the rider pushing a control device with one of his hands or his foot.

An additional optional objective of the design is to optimize the craft for speed, maneuvering and control when riding on the inclined and curved faces of ocean waves and horizontal water surfaces, through the optimization by selection of components with specific hydrodynamic characteristics covered in this document. An example of a specific foil assembly selection to achieve a desired performance feature of this invention would be for the rider to achieve an above water the state configuration with an overall lift value in the foil assembly of less that the rider's and surfboard weight even at very slow speeds. The selective ability to achieve the momentary out of water state is a result of the assistance gained with the use of this specific foil assembly (lower overall area and specifically tip areas and possible lower lift capability in the foil design), in this instance coupled with the rider's experience and control requirements not the total lift component found in the foil assembly. In this example the rider's choice of foil assembly was weighted to more on, and in, the water performance than out of water performance.

According to the invention, the structural flex subassembly is formed by one or more internal structural flex members as shown in FIGS. 1, 2, and 3 in various forms such as 2. 2 shows side mounted tubes connecting the side receiving fin boxes 5 to the center box 1 and main members 4 and 3 with 11 showing the bottom of the main members and 12 showing the top. 4 shows a rectangular main member that can have a number of internal materials in combinations such as foam, honeycomb, foam filled honeycomb and other structural and or flex controlling materials. These complete structures containing 2, 3 and 4 are shown in cross sections in FIGS. 5 and 6 and 14 shows a receiving part for the main tube 3 and the side tubes connecting with the curve forming elements 7. As defined and incorporated and claimed in this invention FIG. 5 shows the optional honeycomb cored composite on the top 8 and the bottom 6 of the watercraft board, with the main tube 3 or panel 4 in cross sectional views in FIGS. 5 and 6. This subassembly of the flex members and rockered foam blank, without the final covering of the blank can be termed a foam blank subassembly for the subsequent production of a watercraft board.

The benefits of the one embodiment of the present invention involves the use of advanced materials coupled with engineered foil fins coupled with the specialized structurally tuned suspension to improve on both the traditional solid foam core and fiberglass construction and the solid core molded and molded hollow boards. This improvement is in both the performance and durability of the surfboard.

In the preferred embodiment of this invention the boards are characterized by an internal carbon composite tube-like structure to respond and support the rider, analogous to the suspension on some pedal driven mountain bikes. The internal composite structure can connect hydrofoils or standard fins to one another and to a central or longitudinal main flex control backbone structure. This combination of fin and central board flex movement controls the main planning area under the rider's feet leading to increased control of the foils and the flex movement of the board in both flex speed and degree. This board deck and bottom movement can be coupled or connected in specific areas such as a few areas centrally located or only in the back area connections 14. Additionally foam or other materials may be used in areas were additional through hull reinforcements are needed. The areas of the board most flex controlled are the foil attachment areas and the areas under the front and back feet of the rider. This area is termed the boards planning area or speed spot. The bottom portion of the hull can be to by partially free floating as shown in FIG. 5 or additionally structural reinforcements made added as shown in FIG. 6 as 15. 15 may be attached on the edge or rail and/or more centrally located for variations in the board's bottom areas. The suspension area under the back and front feet of the rider is designed to serve two main functions. The first is to stabilize and create a torsion stabilizing effect in the connecting or joining of two or more fins. The composite elements connect to the fins attachment areas and to one another for an integrated movement of the fins and the riders back control foot. The second element is the main suspension system, which acts and reacts to rider weight and movement control for maximizing the flexing movements of this area.

In the preferred embodiment of this invention the suspension system is a main longitudinal carbon fiber tube or tube like structure of various shapes including oval, round, square or rectangular or combinations of these shapes. The structural tube like structures can incorporate varying carbon and/or fiberglass wall thicknesses, with thinner top and bottom tube wall thicknesses, and/or internal varying wall constructions. In the case of the round tube an internal tapering wall can be incorporated with a thicker wall at the rear and a progressive tapering thinner wall forward. This thicker wall tube area provides the suspension board with an increase or higher loading capabilities and faster movement speeds in the up and down flex properties. The oval tube also can continuously taper in its overall height progressing forward towards the nose of the board. Dimensional changes in the height of the tube moving forward can reduce the suspension effects in the nose of the board. This serves a number of purposes such as a transition zone in the rigidity properties of the tube to reduce the likely hood of the board breaking at the tubes forward termination point. This also serves to reduce the abrupt termination feel of the tube for the rider in the nose area of the board. The reduced tapering forward tube allows the nose of the board to move or flex more resulting in a variety of beneficial factors such as movement in steep turns on the wave face

The following is an example foil assembly described above termed a Scimitar Fin (smooth warping and curving). A Scimitar Fin for the watercraft of this invention consists of at least one foil segment or segments capable of generating a lift force when moving through the water, and at least one of the foil segments is smoothly warped.

• • Definitions for the Scimitar Fin and other elements of the invention:
  • Smoothly curved fin: a watercraft fin consisting of at least one foil segment capable of generating a lift force when moving through the water and which is comprised of at least one of the foil segment which is smoothly warped.
  • Warp: (1a) to turn or twist out of shape; esp. to twist or bend out of a plane (Webster's Seventh New Collegiate Dictionary).
  • Lift force: the component of a dynamically generated force that is perpendicular to the direction of the free stream flow.
  • Smoothly: (function and first and second derivatives characterizing one or more properties of the foil are mathematically continuous; or the rate of change of all the properties of the segment lie below specified values).
  • Planform: the outline of the set of foil segments if the foil segments comprising the fin is dewarped to lie in the x-y or y, z plane.
  • x-y plane: the plane containing both the x- and y-axes
  • x-axis: a horizontal axis lying parallel to the centerline axis of the watercraft.
  • y-axis: a horizontal axis lying perpendicular to the centerline axis of the watercraft.
  • z-axis; an axis perpendicular to both the x- and y-axes (and hence also perpendicular to the x-y plane).
  • First foil segment: the segment in contact with the watercraft.
  • Fin base: the edge of the first foil segment that is in contact with the watercraft.
  • Fin tip: the point on the planform most distant from a line paralleling the x-axis and running through the fin base.
  • Leading edge: the portion of the planform extending from the forward tip of the fin base to the fin tip.
  • Trailing edge: the portion of the planform extending from the trailing tip of the fin base to the fin tip.
  • chord: the distance from a point along the leading edge of the planform to the corresponding trailing edge point of the planform as measured along a line paralleling the x-axis and passing through the leading edge point (also defines the corresponding trailing edge point as where this line intersects the trailing edge).
  • chord line: the straight line connecting a point on the leading edge of the planform to the corresponding point on the trailing edge.
  • Mid-chord: a point midway between the leading edge and the trailing edge along a chord line.
  • Span line: a line connecting the locus of mid-chord points from the fin base to the fin tip.
  • Span curve: the locus of points representing the projection of the span line onto the y-z plane where y=0 and z=0 at the mid-chord point of the fin base.
  • Pitch angle: the angle between a line paralleling the x-axis and a chord line as projected onto the x-z plane. Varies with position along the span line.
  • Yaw angle: the angle between a line paralleling the x-axis and a chord line as projected onto the x-y plane. Varies with position along the span line.
  • Cant angle: the angle between a line tangent to some point on the span line and the z-axis as projected onto the y-z plane. Varies with position along the span line.
  • Smoothly: (a function and its first and second derivatives that characterize one a foil segment—e.g. pitch, yaw, and cant angles—are mathematically continuous as a function of position along the span line of the foil segment; or the rate of change of each of those properties of the segment along this path are less than pre-specified limits).
  • Segment: is bonded by discontinuity in the properties of the foil; an example of the this would be a smooth warping, curving segment proceeded or followed by a planar segment;
  • Canard; forward or rearward placed from the main foils in a laterally central location.
  • Toe-in; the term toe-in for the definitions relating to this invention shall be considered synonymous with the rotation around the yaw axis.

In the following sections, we present examples of a scimitar fin and the winged fin that illustrate the characteristics of the fins as well as an application of the above definitions. A Scimitar Hydrofin Foil and surfboard for the personal water craft defined in this patent application can be described as the board having a hull, the Scimitar Hydrofin Foil having a hydro dynamically efficient shape designed to facilitate lifting, planing, and turning of the board's hull, the foil comprising a smoothly curved or planar surface defined by the locus of chord lines comprising the foil, the surface is smoothly rotationally warped about at least one of the angular axes of cant, toe-in/yaw, and pitch, said warping along the span of the foil having at least a minimum angular variation around these rotational axes. The Scimitar Hydrofin Foil (smoothly warping and optionally smoothly curving) is affixed so as to be vertically downward depending and may be positioned laterally to the main longitudinal axis of the hull of the board near the mid to rear peripheral edge of the watercraft board. One application of the Scimitar Hydrofin Foil on the surfboard of this invention is the Foil or fin having a significant outwardly extended curve such that it extends as per the definition to a tip point parallel to the bottom surface of the surfboard. In FIG. 21 a Scimitar fin 29 is shown with a wing 30 attached to the fin on inside of the fin. In this configuration a portion of the foil fin structure would replicate some of the particular functions of the alternative wing and down fin assembly described in the disclosure.

The following describes the watercraft as viewed from the perspective view of the bottom of the board seeing the various hydrofoil fins mounted on the structurally flex controlled surfboard with an optional rear hydrofoil swept or un-swept “T” FIG. 11 and “Y” FIG. 10 and foil fin elements 16 the bases, the down segments 20 and extending foils portions 22 and 21 shown in these single center canard foil fins. The viewer could see the side or edge mounted fin/foils FIGS. 7,8 and 9 having main wing foils shown in element 18 and the intersecting connection 19 attached to the down fin 17 and extending out and/or downwardly from the side mounted down-fin. Optionally the viewers frontal view would be of a pair of the various hydrofoil fins mounted on structurally flex controlled surfboard with an optional rear (non-hydrofoil) single center canard fin. Optionally the viewers frontal view could be of a pair of the various hydrofoil fins mounted on structurally flex controlled surfboard FIGS. 5 and 6.

The wing and down or vertical/horizontal hydrofoil assembly of this invention is defined as at least one outwardly and one inwardly extending foil segments form a point of the down fin connecting to the horizontal wing. There may by multiple outwardly and inwardly foils and foil segments with some attachment points positioned paralleling the longitudinal axis of the board and off center from the central longitudinal axis. A wing can be placed on the down or vertical foil segment on all foil fin types defined and described in the invention and are considered aspects of this invention. The foil assembly with its optionally attached wing foil is attached either forward or in the rear of the main wing foil assemblies. Structural and control considerations again lead to the streamlined vertical wing assembly connecting to the hull at a location in the general area of the rider. For some conditions involving yaw stability, the preferred point of connection is aft of the center of mass of the rider. The main wing assemblies resemble more of a mirror-imaged unequal sided “T” or inverted “Y” and can be configured in a number of alternative forms. The rider's choice would be based on his preference for control. These control features include the wing foil section choices, overall area choices and angles either wing tip forward or wing tip swept aft and or wing tip raised or lowered on the horizontal axis. Optionally the main foil assemblies may be asymmetrical in configuration. Motivation for this choice also may include the rider's requirements for his predominate forward foot side stance (left foot forward=“regular foot” stance, right foot forward stance=“goofy foot” stance). An example of the control would be if the rider wants to drive out or extend out his front side bottom turns, he might choose a lowered (greater angle from the vertical foil strut to the main wing foil) front side (side which he is facing) main foil wing tip (from that of the left side tip angle) thereby creating an asymmetrical setup or rigging angles in that particular axis. These equipment or rigging choices could be to benefit the full flight (hull out of the water) or the combinations of full flight and hull particularly planing riding modes.

The rear center trim or forward trim foil (canard foil when configured with wing element) can be a single fin or can be configured with an inverted “T” or inverted “Y” and possible an arrowhead shape. The optional vertical center fin or center fin with wing foil and placements of downward pointing forward and aft configurations as well as choices in wing rigging angles (wing tip up, neutral or down) selection is to achieve specific controls for individual or combinational hull riding attitudes. The benefit to having the hull to return to the surface of the water in the event of either a mistake or a deliberate maneuvering requirement or choice is a significant feature of this device. This adjustment can be both at wing and vertical fin strut interface through a mechanical screw adjustment and or at the vertical fin strut attachment point with a screw or shim device.

An additional optional feature of this invention is the connecting of the two main wing foils with a streamlined or foiled structural section. This section could join the two main wing foils in a straight across method or in forward or rear “V” section. This additional section achieves a number of benefits for the rider. This section joining the two main wing foils in a forward or rear “V” section both structurally reinforces the main wing foils and extends the lift area and affects the pitch characteristics of the overall device.

An additional feature of this invention is the wing assembly pitch rigging angles feature found in both the main wing foil assemblies and optionally in the center mounted wing assembly. The rigging angles of the complete combination vertical foil strut and main wing foil are combined into a continuous and or warped curve foil. The main foil assembly originates at the hull attachment point and extends downward with curve and optionally extending downward with both curve and warp in the individual foil sections forming what could be defined as wing tip area washout (tip down configuration) or warping in the opposite direction to form a tip area up configuration. An example of this type of continuously curved and warped foil can be seen in FIGS. 8-10. This curving and or warping foil feature can be achieved in all foil sections including both a downward outwardly extending foil and a downwardly and inwardly extending foil. This curving and or warping foil feature can be achieved in the center mounted foil section. In the case of the center foil/fin this wing/foil warping can be achieved with the lower portion of the foil forming two separate outwardly extending foil areas extending in opposite directions from one another forming a inverted “Y” with curved extended arm sections.

Stability requires that when the foils are balanced (“trimmed”) in pitch, the forward foil is either more heavily loaded (i.e. generating more lift per unit foil area) or has a lower lift coefficient slope than the main foil for the canard configuration, and the opposite response for the conventional configuration. This means that the trim foil is the less efficient (greatest drag for a given lift force) of the two foils for the canard configuration, but the main foil is the less efficient for a conventional configuration. Since the main foil typically generates substantially more lift than the trim foil, this means that the additional induced drag resulting from the reduced efficiency of the main foil in the conventional configuration is greater than the additional induced drag resulting from the reduced efficiency of the trim foil in the canard configuration.

The end result is that for comparable foil designs, a canard either a forward or a rear placed canard configuration hydrofoil or hydrofoil board yields a greater speed potential than the equivalent hydrofoil board utilizing a conventional configuration. A disadvantage of the canard configuration is that one has lost the shock dampening when “landing” from an aerial maneuver that is provided with the conventional configuration depending on overall surface areas and angles.

Both configurations are unstable in roll. In the absence of a pull from being towed by a power craft, the primary method of roll control is by turning the craft into the direction of roll (analogous to how one balances a bicycle in roll). Once a turn is initiated, a centrifugal force is generated close to the elevation of the center-of-mass of the board and rider above the foils. This force lies along the radius of the turning circle and is directed outward (away from the direction of roll). By varying the pitch angle of the craft, the rider can alter the radius of the turn circle, and thus the magnitude of the centrifugal force (which is inversely proportional to the radius of the turning circle). If the turn radius produces a centrifugal force, and creates a moment around the roll axis equal to the moment created by gravity in combination with the displacement of the center-of-mass of the rider and board relative to the center-of-effort by the foils, then the bank (roll) angle remains constant and a coordinated turn is executed. A smaller turning radius, and greater centrifugal force, causes the bank angle to decrease and the craft roll more upright; conversely a larger turning radius results in a still increasing bank angle, but at a reduced rate of increase.

A turn is initiated with the rider initially rotating the upper portion of his body in a dockwise direction to turn right, or counter-clockwise direction to turn left. From Newton's Third Law of Motion, this causes the rider's lower body and craft to rotate in the opposite direction about the yaw axis (axis perpendicular to the plane of the foils). In the case of a rotation of the upper body clockwise, this results in a counter-clockwise rotation of the craft about the yaw axis. The vertical strut then acts to move the foils to the left of the center-of-mass of the craft and rider. In combination with the force of gravity and the lift forces generated by the foils, this causes the craft and rider to begin to roll to the right. As this roll develops, the rider shifts his weight aft to increase the pitch angle. This initiates the turn to the right and at least partially compensates for a reduced vertical component of the lift force generated by the foils and slows down the rate of change of the elevation of the hull above the water. If the pitch angle is properly set, a steady constant radius turn will occur. Otherwise the radius of the turn and/or the bank angle of the craft will continue so change (as when entering or exiting a turn).

If the board is off-balance in roll, the rate of change in bank angle will increase as the bank angle increases. Thus minimal effort is required to correct for a small, undesired bank angle, but if the bank angle is allowed to become too large, it may be impossible for the rider to keep from capsizing. Two factors that affect roll control are the controllability of the craft in setting up a turn, and the rate at which an uncorrected bank angle accelerates. The later is partially controlled by the spacing between the plane containing the pair of hydrofoils, and the center-of-mass of the rider and board above that plane (the greater the separation, the slower the angular acceleration of the bank angle). But that's if the lift forces generated by the foils are equal on the both sides of the foil with respect to their centerlines (i.e. the longitudinal axis of the craft). However, if the craft is rotating, the flow over the leading edge of the foil on the side of the foil toward the roll will have an upward component added to the free stream flow, while the flow over the leading edge of the foil on the opposite side will have a downward component. The effect is to increase the angle-of-attack of the flow over the side into the bank, and a reduction in the angle-of-attack of the flow over the opposite side. Since the lift generated is proportional to the angle-of-attack, this means that the side of the foil in the direction of bank is generating more lift than is the foil on the opposite side. Hence a moment is created that opposes the moment generated by the force of gravity. This reduces the rate of angular acceleration, and gives the rider more time to recognize the developing roll angle and correct it.

The effectiveness of this process in dampening roll rate is related to the span and to the lift-slope coefficient of the foil. The span is especially effective as the greater the distance from the roll axis to some section across the chord of the foil, the greater the moment arm contributing to the torque opposing the gravitationally driven rolling moment, and the greater the magnitude of the induced flow past the leading edge, thus increasing the increase in effective angle of-attack, and hence the magnitude of the lift force. Thus both the differential lift force and the moment arm increase as the span is increased.

For a given foil area, the foil span increases as the aspect ratio increases. As noted above, for a canard-configured hydrofoil, pitch stability requires that the main foil or foils be less heavily loaded than the canard foil, or that the canard foil generate less lift per unit increase in the angle of attack (per unit foil area). Which of these approaches, or what combination of the two, should be used is primarily related to trade-offs between drag minimization and the likelihood of a foil stalling (and the characteristics of that stall, should it occur).

One way to accomplish the latter is if the aspect ratio of the main foil or foils is greater than the aspect ratio of the canard foil. This is consistent with increasing the aspect ratio of the main foil, and hence it's span. Thus increasing the aspect ratio of the main foil in a canard configuration builds pitch stability and also reduces roll rate. Conversely, the pitch stability condition for a conventional configuration promotes a reduced aspect ratio for the main foil, relative to that of the trim foil. Hence roll rate will be increased for this configuration for the same pitch stability as with a canard configuration.

The advantages and disadvantages of a Y configured main foil over the T configuration is summarized in the following table (assuming the same strut or down fin length and the same projected horizontal area for both foils):

TABLE II
Main Foil Configuration
Parameter	“Y” configuration	“T” configuration
Wetted area/parasitic drag	Increased	Decreased
Induced drag	Uncertain	Uncertain
Interference drag	Uncertain	Uncertain
Roll rate	Reduced	Increased
Aspect ratio	Increased	Decreased
Minimum water depth	Increased	Decreased
Handling ease	Decreased	Increased

Of course, other main foil configurations are also possible. For example, a foil with canted down or up outside or inside tips segments mated to a horizontal outer or inner segment section. In addition, one can further modify the characteristics of the foil (and its effects on drag, stability, and control) by adding twist to one or more foil segments, or varying the foil section and pitch, cant, and sweep angles among the foil segments. The effect of the foil wing tip emergence from the water on a turn is that the “T” tip would emerge from the water sooner that the “Y” and reduce performance of the device.

These various means of influencing the drag, stability, and control characteristics of the craft allow extensive tailoring of the craft characteristics to best match the performance (speed and maneuverability) and stability and control desired by the rider, resulting in a significant improvement over the present state of the art hydrofoil wave-riding craft and conventional surfboard ridding.

These broad objectives are achieved by the addition of two or more multifunctional hydrofoil fins extending downward and generally outward from the bottom of the board hull. One member of a pair shall be disposed at least halfway from the centerline of the hull, and other member of the pair shall be similarly disposed on the opposite side of the centerline. The multifunctional hydrofoil fins need not be identical. For example, one multifunctional hydrofoil fin may be the mirror image of the other about the longitudinal axis of the craft or they are asymmetrical in all aspects of their design from one another. The two outer multifunctional hydrofoil fins shall be positioned within the rear one-half of the hull. Optionally, an additional multifunctional hydrofoil fin may lie on the centerline of the craft and positioned fore or aft of one or more of the multifunctional hydrofoil fins.

Each multifunctional hydrofoil fin is comprised of one or more foils and foil segments. Each foil segment is bounded by a leading edge, a trailing edge, and two chord ends. The leading and trailing edges of a foil segment may be curved, straight or combinations of the two. A chord end connects the end of the leading edge on one end of a foil segment with the trailing edge on the same end of the foil segment. The chord line at one end of a foil segment may be angularly displaced from the chord line at the opposite end of the same foil segment (i.e. the segment may be “warped”, or twisted, between chord ends). Foil segments are distinguished from one another by abrupt or discontinuous changes in their rigging angles (with respect to the longitudinal, transverse, and vertical axes of the watercraft), and/or their cross-sections, and/or their flex characteristics, and/or their planforms, areas, and aspect ratios.

Each multifunctional hydrofoil fin is comprised of one or more foil sections. Each foil section is bounded by a forward point, a trailing point, and two chord ends. The leading portion and trailing portion of a foil section may create a curved, straight or combinations of the two in the foil section. A chord end connects the end of the leading portion on one end of a foil section with the trailing portion on the same end of the foil sections. The completed section at one end of a foil section may be angularly displaced from the section plane at the opposite end of the same foil segment (i.e. the section may be “warped”, or twisted, between the section ends).

Another characteristic of the multifunctional hydrofoil fins is that the set of foil segments comprising the multifunctional hydrofoil fin shall have a projected area onto the plane defined by the longitudinal and transverse axes of the hull. The foil segment that is joined to the surfboard hull is defined as the “first foil segment”. A further optional characteristic of the multifunctional hydrofoil fin is that the projected area defined above extends outward from both sides of the first foil segment. Another characteristic of the multifunctional hydrofoil fin is that the first foil segment has a projected area onto the plane passing through the longitudinal axis and the vertical axis of the craft.

Another characteristic of the multifunctional hydrofoil fins is that the set of foil segments comprising the multifunctional hydrofoil fin have a projected area onto the plane defined by the longitudinal and transverse axes of the hull (and may extend past the outer edge of the craft). The foil segment that is joined to the surfboard hull is defined as the “first foil segment”. The continuous or simi-continuous warping of the individual foil segments may extend down and out in either or both the outward (away from the center line of the craft) and the inward direction of the centerline of the craft (extend into the centerline of the craft).

The (vector) force generated by water flowing past a foil segment is defined as the “pressure force”. In the subsequent discussion, the sum of the components of the pressure forces paralleling the vertical axis of the craft generated by each member of the set of foil segments comprising a multifunctional hydrofoil is defined as the “lifting” force generated by the multifunctional hydrofoil fin. The “lift” force generated by the multifunctional hydrofoil fin is defined as equal to the product of this lifting force and the cosine of the angle between the normal to the (bottom) hull of the board and the normal to the local sea surface. By analogy with the diving planes on a submarine, if the lift force is directed upward, the fin is said to be “up-planing”; if downward, it is “down-planing”. Alternatively, a planing force may refer to the pressure force generated by segments of the multifunctional hydrofoil fin that only have one of their two faces in contact with the water. The two usages can be distinguished by the context of the usage. The sum of the components of the pressure forces generated by the set of foil segments comprising a multifunctional hydrofoil fin parallel to the transverse axis of the craft is defined as the “turning” force generated by the multifunctional hydrofoil fin.

The foil segments comprising a hydrofoil fin have their centers-of-effort spatially displaced from each other. Hence a variable hydrodynamic response is created as the rider manipulates the trim angles of hull of the watercraft in pitch, roll, and yaw, thus altering the magnitude, spatial distribution, and angle-of-attack of the wetted area of the hull (as with a conventional planing hull). The magnitudes, directions, and locations of the centers-of-effort associated with the totality of foil segments making up the set of hydrofoil fins also contribute to the hydrodynamic response of the craft. Since the craft is typically operated on, or in the immediate vicinity of, the sea surface, the force characteristics are not only dependent on the normal hydrodynamic characteristics of the foil segments (e.g. planform area, aspect ratio, foil section, etc.) but also on the wetted areas, degree of immersion of each segment (since portions of a multifunctional hydrofoil fin may emerge from the water during maneuvering and riding across the face of a wave). Hence the multiplicity of degrees-of-freedom available in the design and rigging of the individual fin segments comprising a hydrofoil fin provides the designer and/or rider with considerable latitude in tailoring the response of the craft to the needs and desires of the rider with regard to speed, maneuverability, stability, and control.

An additional feature of this invention is that in a traditional single main hydrofoil, as the aspect ratio is increased for greater lift potential the roll stability increases and may increase to unacceptable control point of roll resistance. The separation and design of the main lifting foils of this invention coupled with either the forward Canard or the rear conventional center foils, effectively separate the foils to create greater roll control.

In an alternative embodiment of this invention the outboard foils are rider controlled to actuate a pitch up or down attitude change in the foil assemblies. In one embodiment of this, the rider's foot and or hand can actuate the foils simultaneously or independently. The pitch control actuation could be termed a virtual pivot point due to the performance resulting from the foil pitch angle (up as an example) change. The results from this pitch attitude change can be a significant increase in lift without having to move the entire board attitude correspondingly up to achieve the lift factor.

In an additional embodiment of this invention the virtual pivot point control is integrated into a suspension or support (structural) system and the foil point attachment point in the rear area of the surfboard. The surfer's rear foot can control a connected structure joining the outside foils to one another either directly or indirectly. Alternatively the center foil's pitch attitude can be controlled or changed affecting the pitch the surfboard. The pivot rotational foil is specifically designed to enable the novice and intermediate as well as the expert surfer to perform at higher levels of performance very quickly. This specific advanced ability is achieved by allowing the novice or expert surfer to move the foil fin or to lock out the movement on the surfboard for the initial learning process.

In an additional embodiment of this invention the virtual fin control is integrated into a suspension or support (structural) system and the foil point attachment points in the rear area of the surfboard. The surfer's rear foot can control a connected structure joining the outside foils to one another either directly or indirectly and the central connecting point is directly in close proximity to the surfers rear foot thereby limiting the effects of the significant force loads and distortions on the fins and board. This structural connection or a portion of the internal suspension subassembly provides the necessary integration of the fins on the bottom of the board through the board and into the surfers foot without significant torsional loss of the fins surfaces resulting in the loss of fin power and control. Additionally and alternatively the center foil's torsional pitch attitude can also be controlled remain unaffecting buy the significant forces in the water and potential through the surfboard. An additional element of the structural options of the invention is the fixing of additional composite or structural enhancing structures such as carbon or fiberglass tubes along the inside edges or surfboard rails. This structural addition reinforcing of the edge areas particularly the central center or middle can significantly reduce the board buckling or folding in half in some conditions experienced in the sport.

The surfboards described in this invention may be manufactured in a variety of construction materials and methods such as hallow and partially hallow or cavity boards or solid foam corded. The fins claimed in this invention may be manufactured using a variety of materials and methods but not limited to, foam cored, injection molded, injection molded with carbon rod or tube structures embedded, resin transfer molded, partially hallow or cavity fins and solid foam or partial cored fin structures.

An objective of this invention is to incorporate one or more subassemblies into the construction of the surfboard which will provide the surfboard designer and builder more degrees of freedom in the design and construction so as to assist him in manufacturing a board that can better match the board characteristics with the rider's preferences. The flexural properties of the claimed suspension sub assemblies include not only the degree of flex as a function of loading, but also the temporal response of the flexed system to intermittent loading and unloading by the surfer and the hydrodynamic pressures on the surface of the board. For example, flexural response can be expected to be most rapid and require the least effort when the frequency of loading and unloading by the rider matches the natural frequency of that mode of vibration of the board (i.e. the loading and response are in, or close to, resonance). Flexural motions affect not only the “feel” of the board, but also its hydrodynamic performance and, in some instances, the structural strength (e.g. structural failure due to buckling). Controlled flexural movements can also provide new hydrodynamic means of controlling the board and increasing its performance, such as the addition of hydrofoils.

In one of the alternative embodiments of this invention the rider's foot (heel or ball) may press down on a rear portion of a protruding element of the foils base. This extended portion of the foils forward base is rotational fixed and the rear portion is exposed to the rider's foot pressing down to create a pitch-up attitude in the leading edge portion of the splay area of the foil. In one example of the surfboard bank turning a foil designed to gain very high lift at high angles of attack (this pitch-up attitude) this configuration would result in a lifted or extended turn. This form of foot control could be independent or coupled from one foil to the other across or in the board's structure to achieve an opposite or coordinated foil movement.

In one of the alternative embodiments larger and potential soft covered foil fins may be used by the novice surfer. The larger foil fin can stabilize the rider for the learning process. This process is vastly accelerated due to the increased ease of learning to balance, stabilize and steer or turn from the wider, forward portion of the surfboard. The increased capability to balance, stabilize and control the board from the wider portion of the board is a part of the reasons for the accelerated learning process. As the surfer progresses his position on the board will move further back on the board there by increasing the turning power of the board.

The movable foil can be used with or without additional fixed foils to fine-tune the board's performance to meet individual surfer's preferences or variable wave characteristics. Controllable foil allows the surfer to turn and control direction and maneuverability on the wave with the pitch or rotational action of the foil or foils by the rear foot, which in turn controls the pitch the board in any maneuver. The more increased the pivot or rotational attitude change of the foil by the foot movement the greater the effect on the surfboard. This control is in sharp contrast to that of traditional fixed foil fin surfboards

One option is for the end of or upper base of the foil to be mounted to the relatively simple rotational plate in the box (fin attach or secures into a receiver box) attachment system. The rotational plate is connected to a rod or plate while the other end of the rod passes across or through the surfboard with the foil base attached to it. Alternatively the foil fin and control system could be mounted and act independently from one another. The whole foil fin system could be in an adjustable thru-board foil fin box system. The foil position could be moved forward and aft depending on wave or user's need. Traditionally a surfer's weight must be centered over the fins at the very rear of the surfboard. The balance required to learn the turn from the extreme rear point is one of the most difficult aspects of the sport to learn. With the foil fin control, the foil fin can be moved forward or more the midpoint of the board for the beginner and more aft for the intermediate. The foil fin can be moved aft for the expert and varying wave conditions.

Claims

1. A personal watercraft board, said watercraft comprising at least two laterally located off center hydrofoil fin members, said hydrofoil fins extending downwardly and outwardly depending from hull, said hydrofoil fins for turning, lifting and planing of the watercraft, said hydrofoil fins capable of two or more of the following states, 1. maneuvering of the hull in the above water foiling state, 2. maneuvering of the hull in the partially lifted hull and planning state, 3. maneuvering of the hull in a low to mid lifted and planning state.

2. A personal watercraft according to claim 1, wherein said watercraft contains a subassembly, said subassembly further comprises covering a portion of at least one of said upper and lower surfaces with an outer layer of thermosetting resin-impregnated fibers.

3. A personal watercraft board according to claim 1, said watercraft comprising: at least one inner structural flex member; comprising a tube like structure; said tube like structure comprising: at least an upper and lower resin impregnated fibrous layer in the upper and lower areas: the watercraft further comprising a least two side mounted combination hydrofoil turning fin structure members.

4. A personal watercraft according to claim 1, wherein: said structural member comprises an upper, lower and sides comprising resin fibrous impregnated structural materials.

5. A personal watercraft according to claim 1, wherein: said inner structural flex member comprises multiple resin-impregnated fiber layers.

6. A personal watercraft according to claim 1, further comprising: a longitudinally extending structural member within said watercraft for further control of the flex and structural properties of said watercraft.

7. A personal watercraft according to claim 1, wherein: said longitudinally structural member extending is in a central position in or on the top surface of the watercraft.

8. A personal watercraft according to claim 1, wherein: said watercraft structure at least some thermoformed extruded polystyrene foam.

9. A personal watercraft according to claim 1, wherein: said watercraft structure contains at least some thermoformed molded and/or extruded polystyrene foam.

10. A personal watercraft according to claim 1, wherein: said watercraft contains at least some thermoformed polystyrene foam.

9. A personal watercraft according to claim 1, wherein: said watercraft contains at least some thermoformed molded polyurethane foam.

10. A personal watercraft according to claim 1, further comprising: one or more structural members comprising honeycombed flexible reinforcement structures.

11. A watercraft board according to claim 1, further comprising: one or more fin and or box receiving assemblies connected to one another with a subassembly.

12. A watercraft board according to claim 1, further comprising: one or more fin box receiving assemblies structurally connected with subassemblies to one another and to the main structural member.

13. A subassembly according to claim 1, further comprising: a plurality of longitudinally structural flex members extending within said personal watercraft.

14. A watercraft board according to claim 1, wherein said inner structural flex member includes a wall having a thickness of 0.1 to 4.0 millimeters.

15. A personal watercraft board according to claim 1, said watercraft comprising at least two laterally off center located combination hydrofoil turning fin members connected to one another with at least one subassembly, said personal watercraft hydrofoil fins extending downwardly and outwardly depending from hull, said hydrofoil fins for turning, lifting and planing of the watercraft, said hydrofoil fins capable of two or more of the following states, 1. maneuvering of the hull in the above water foiling state, 2. maneuvering of the hull in the partially lifted hull and planning state, 3. maneuvering of the hull in a low to mid lifted and planning state.

16. A hydrofin foil for personal watercraft according to claim 1, said hydrofin foil having a hydrodynamically efficient shape designed to facilitate lifting, planing, and turning of the watercraft hull, said foil comprising a smoothly curved surface defined by the locus of chord lines comprising the foil, said surface is smoothly rotationally warped outwardly about at least one of the angular axes of cant, toe-in, and pitch, said warping along the span of the foil having at least a minimum angular variation around at least one of these rotational axes, said hydrofin foil being affixed so as to be vertically downward outwardly depending and positioned laterally to the main longitudinal axis of the hull near the peripheral edge of the watercraft.

17. A hydrofin foil according to claim 1, said hydrofin foil having a hydrodynamically efficient shape designed to facilitate lifting, planing, and turning of the watercraft hull, said foil comprising a smoothly curved surface defined by the locus of chord lines comprising the foil, said surface is smoothly rotationally warped outwardly about at least one of the angular axes of cant, toe-in, and pitch, said warping along the span of the foil having at least a minimum angular variation around at least one of these rotational axes, said hydrofin foil having a wing structure attached to one side, said hydrofin foil being affixed so as to be vertically downward outwardly depending and positioned laterally to the main longitudinal axis of the hull near the peripheral edge of the watercraft.

18. A hydrofin foil for personal watercraft according to claim 1, said hydrofin foil having a hydrodynamically efficient shape designed to facilitate lifting, planing, and turning of the watercraft hull, said foil comprising a smoothly curved surface defined by the locus of chord lines comprising the foil, said surface is smoothly rotationally warped outwardly about at least two of the angular axes of cant, toe-in and pitch, said warping along the span of the foil having at least a minimum angular variation around at least one of these rotational axes, said hydrofin foil being affixed so as to be vertically downward depending and positioned laterally to the main longitudinal axis of the hull near the peripheral edge of the watercraft.

19. A hydrofin foil for personal watercraft according to claim 1, said hydrofin foil having a hydrodynamically efficient shape designed to facilitate lifting, planing, and turning of the watercraft hull, said foil comprising a smoothly curved surface defined by the locus of chord lines comprising the foil, said surface is smoothly rotationally warped outwardly about at least one of the angular axes of cant, toe-in and pitch, said warping along the span of the foil having at least a minimum angular variation around at least one of these rotational axes, said hydrofin foil being affixed so as to be vertically downward outwardly depending and positioned laterally to the main longitudinal axis of the hull near the peripheral edge of the watercraft.

20. A hydrofin foil for personal watercraft having a hull according to claim 1, said hydrofin foil having a hydrodynamically efficient shape designed to facilitate lifting, planing, and turning of the watercraft hull, said foil comprising a smoothly curved and a least one planar surface defined by the locus of chord lines comprising the foil, said surface is smoothly rotationally warped outwardly about at least one of the angular axes of cant, toe-in and pitch, said warping along the span of the foil having at least a minimum angular variation around at least one of these rotational axes, said hydrofin foil being affixed so as to be vertically downward outwardly depending and positioned laterally to the main longitudinal axis of the hull near the peripheral edge of the watercraft.

21. A hydrofin foil for personal watercraft according to claim 1, said hydrofin foil having a hydrodynamically efficient shape designed to facilitate lifting, planing, and turning of the watercraft hull, said watercraft having at least two edge mounted hydrofin foils, said hydrofin foils comprising one least one foil wing attached to each side of a downwardly depending fin, said foil sections defined by the locus of chord lines comprising their foils, said foils may be various planar shapes and/or smoothly rotationally warped outwardly about at least one of the angular axes of cant, toe-in and pitch, said warping along the span of the foil having at least a minimum angular variation around at least one of these rotational axes, said hydrofin foil being affixed so as to be vertically downward outwardly depending and positioned laterally to the main longitudinal axis of the hull near the peripheral edge of the watercraft.

22. A method for manufacturing said hydrofin foil according to claim 1, said hydrofin foil having a hydrodynamically efficient shape designed to facilitate lifting, planing, and turning of the watercraft hull, said foil comprising a smoothly curved surface defined by the locus of chord lines comprising the foil, said surface is smoothly rotationally warped outwardly about at least one of the angular axes of cant, toe-in and pitch, said warping along the span of the foil having at least a minimum angular variation around at least one of these rotational axes, said hydrofin foil having a wing structure attached, said hydrofin foil being affixed so as to be vertically downward depending and positioned laterally to the main axis of the hull near the peripheral edge of the watercraft, said method of manufacturing may include but is not limited to foam cored structures, injection molding, injection molded with carbon rod or tube structures embedded, resin transfer molded, partially hallow or cavity fins, over-molded structures and solid foam or partial cored fin structures.