Dynamic fin alignment system

Abstract

A watercraft fin that dynamically keep a neutral alignment within the range of angles a user chooses to have and/or change in respond to the flow conditions so reducing drag. Hence, this invention is such to enable a fin to rotate within a range of angles via a rotary bearing and bearing housing which are to receive a fin having a journal base. The housing is to be fitted to a watercraft such as a surfboard, the housing having a changeable circular keyway to loosely receive a shear key at the underside of the journal base as to allow free circular motion of the shear key and correspondingly the journal base and the fin within the limits of the selected circular length of the keyway. In one form the fin is fitted with a root portion adapted to be inserted into a receiving portion extending radially in the journal base and trapped within the bore of the bearing.

Claims

1. A dynamic fin alignment system comprising: a bearing housing for attachment to a watercraft, the bearing housing having a housing bore with means for releasably securing a rotary bearing, the bearing housing having an interior base surface with a recessed slot defined therein, the recessed slot configured to releasably secure a correspondingly shaped changeable insert; a rotary bearing for being releasably secured into said bearing housing and having at least one race and a bearing bore coaxial with said housing bore when the dynamic fin alignment system is in an assembled condition; an axially symmetric body having a journal for cooperating with the at least one race to support rotation of the axially symmetric body relative to the rotary bearing; a fin extending from a first side of the axially symmetric body when the dynamic fin alignment system is in the assembled condition; a shear key extending from a second side of the axially symmetric body that is opposite the first side; and a plurality of said changeable inserts for being disposed, one at a time, within the recessed slot of the bearing housing, each changeable insert having a keyway for receiving the shear key when the dynamic fin alignment system is in the assembled condition.

2. The dynamic fin alignment system of claim 1 wherein the rotary bearing is a rotary two-piece bearing.

3. The dynamic fin alignment system of claim 2 wherein said rotary two piece bearing has an outer rim and an exterior side face that extends radially inward from the outer rim to a central opening defining the bearing bore, the exterior side face for being flush mounted with a finished underside of the watercraft, and wherein the at least one race is provided along an underside face that is opposite the exterior side face and that is adjacent to the bearing bore.

4. The dynamic fin alignment system as defined in claim 1 wherein the keyway of each changeable insert of the plurality of said changeable inserts has a length that extends along a circle that is concentric with said housing bore when inserted in the recessed slot, such that the shear key moves along a curved path within the keyway upon rotation of the axially symmetric body relative to the rotary bearing.

5. The dynamic fin alignment system of claim 4 wherein each changeable insert has a different keyway length relative to the other changeable inserts of the plurality of said changeable inserts.

6. The dynamic fin alignment system of claim 4 wherein the length of the keyway of at least one changeable insert of the plurality of said changeable inserts is asymmetric relative to a central plane of the at least one changeable insert, the central plane normal to the curved path.

7. The dynamic fin alignment system as defined in claim 1 wherein a side surface of the fin, which is defined between a leading edge of the fin, a trailing edge of the fin, a top edge of the fin, and a bottom edge of the fin, forms a hydrodynamic foil.

8. The dynamic fin alignment system as defined in claim 7 wherein the axially symmetric body and the fin are formed as a single, monolithic component.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For a more complete understanding of the invention, reference is made to the following description and accompanying drawings, in which:

(2) FIG. 1 is an exploded-view drawing of a fin having a journal base, a two piece bearing, a bearing housing and an insert having a selected keyway length accordingly to meet the objects of this invention;

(3) FIG. 2 is an exemplary set of inserts to enable numerous degrees of freedom of fin engagement in support of the embodiment in FIG. 1 to meet the objects of this invention;

(4) FIG. 3 is an exemplary exploded-view of a fin having a root body to be inserted into a fin base which are to be secured within the confines of the bore of a bearing; and

(5) FIG. 4 illustrates how the embodiment in FIG. 3 is assembled for deployment into the bore of a bearing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(6) The exploded-view drawing in FIG. 1 shows an exemplary arrangement of a preferred embodiment of this invention for crafts that are laminated with fiber glass. In FIG. 1 one sees an axis of rotation [1] oriented top to bottom located near the foremost portion of the leading edge [2] of the fin [3] around which the fin [3] is to rotate.

(7) The bottom front end [4] of the fin is in material connection with a body having the geometry of a stack of two coaxial disks which are in turn coaxial with the axis of rotation [1], a disk base [5] with a disk journal [6] at its underside which are to bear in a bearing comprising a first piece [7] and a second piece [8] fitted with alignment pins [9] and receiver holes [10] or the like to accurately align its first piece [7] and its second piece [8] together, the trailing portion of the fin's bottom end [11] extending closely and parallel to the under-side of the watercraft (not shown). The view of the entire fin [3] and its disk base [5] are also shown in smaller scale on the top left side of FIG. 1.

(8) The bearing ([7] and [8]), has an exterior side face [13] and an underside face [14] that extend radially from its bore [15] to an outer rim [16] dimensionally fit to meet the bore [17] of a bearing housing [18], the bearing's underside face [14] having means to be releasably secured to the bore [17] of the bearing housing [18] which in this embodiment consists of a thread connection [19] drivable with a hard edge on notches [20], the exterior side face [13] of the bearing flush with the lami-nation finish (not shown).

(9) The bearing housing [18] forms a coaxial cylindrical hull at the underside of the lamination (not shown) of the watercraft with its bore [17] facing upward to receive the bearing ([7] and [8]) and having exterior side faces [21] and interior side faces [22], the exterior side [21] may have a framework to facilitate interlocking engagement thereof with an adhesive material for affixing the fin box to the watercraft, which in this embodiment consists on its exterior side faces [21], the bearing housing's [18] interior side face facing upward [22] having a cir-cular protrusion [23] dimensionally fit to meet the underside of the disk journal [24] and having an elongated circular slot [25] between its axis [1] and its rim [26] shaped to receive a correspondingly shaped insert [27], the slot being axisymmetric about a circular axis [28] at its center which is concentric with the axis of rotation [1], the slot extending circularly along the circular axis [28] a finite distance and having means to releasably secure the correspondingly shaped insert [27], which in this embodiment consists of a protrusion [29] along the slot's side walls to engage a correspondingly shaped cavity [30] when the insert [27] is pressed into the circular slot [25] which may extend into means to facilitate removal, which in this embodiment consists of notches [31] to manually exert a prying force to a slanted undercut [32] on the insert [27] for removal.

(10) The insert [27] having an elongated circular keyway [33] axisymmetric about the circular axis [28] of the circular slot [25], the keyway [33] being dimen-sionally fit to radially and circularly loosely receive a shear key [34] correspondingly protruding from the underside of the disk journal [24] into the center of the keyway [33].

(11) The shear key [34] being preferably in cross section of a circular segment [35] shape to withstand the lateral force induced by rotational forces acting upon the fin and when moving side to side and allowing the movement of water from side to side to prevent the build up of pressure. Another preferred embodiment of the shear key may radially fit tight within the keyway allowing the build up of pressure for a slow transition between the initial time of the turn and the final position of the fin at the stop point in the insert.

(12) The arrangement in FIG. 1 is dimensionally and structurally fitted to bear loads allowing free rotation within the limits of the difference in length between the keyway [33] and the shear key [34]. Axially outward loads are bear along the race [36] at the underside of the bearing normally adjacent to the bore [15] of the bearing, the journal being the upper side [37] of the disk journal adjacent to the rim [38] of the disk base [5]. Radial loads are bear along the bore [15] of the bearing, the journal being the rim [38] of the disk base [5]. Axially inward loads are preferably bear along the circular protrusion [23] in the bearing housing [18], along the edge normally adjacent [39] to its rim [26].

(13) The exemplary embodiment in FIG. 1 also includes an in-lamination pro tractor [40] image preferably in the trailing side of the bearing housing to obtain information visually about the current alignment and range.

(14) FIG. 2 shows an exemplary set of inserts for different degrees of freedom of fin engagement and their effect on fin alignment. In FIG. 2 one sees the underside [41] rear portion of a surfboard, its center line [42] and its nowadays preferred arrangement of three fins, free to rotate symmetrically the angle of freedom [43] enabled by three identical inserts [27] from a first position [44] to a second position [45].

(15) The angle of freedom [43] of fins enabled on the surfboard by other sets of three inserts is shown above, below and to the right in the figure. It can be seen on the right side of FIG. 2 that the inserts can enable asymmetric [46] alignment which may be preferred to enable stalls for tube riding or to cut back into preferred sections for waves that are exclusively to the right or to the left. FIG. 2 also shows the slanted undercut [32] for prying out the insert [27], for the ease of reference a dotted perimeter of the circular segment [35] cross section of the shear key [34] as it sits in the keyway [33] when deployed is also seen along with the circular axis [28] in which the keyway [33] extends and the shear key [34] moves.

(16) The set of inserts in FIG. 2 includes a labeling scheme to refer to the angles set by the insert, in said scheme the water craft is referred to as having a deck, an underside, a center line, a frond end and a rear end in a conventional manner and a user refers to the alignment of the fins and the craft as standing on its deck looking towards the front. Said scheme consists on letters and numbers as described below and not shown in FIG. 2.

(17) The alignment or range of alignments of one fin set by an insert is given on the trailing side in reference to a line parallel to the center line, further referred to as center line, passing through the center of rotation of the fin. The scheme can be applied to fixed fins or for fins having a degree of freedom, further referred to as freedom, for which the center line is within the range of the angles swept by the fin. The fin can be Fixed or have Symmetric or Asymmetric sweep, Left or Right correspondingly denoted in the scheme using the letters F, S, A, L and R. The term Simon Anderson (SA) is applicable for fixed alignments defined with a single toe angle in its nowadays preferred range of 3 to 5 degrees. A slash/is used as a separator and a prefix in the form of yx denoting the number of fins y on the surfboard when required.

(18) The order of the letters and numbers in the following order: 3A20L/10R for 3 fins having 20+10=30 degrees freedom, asymmetric sweep, 20 degrees left and 10 to the right. Correspondingly, a symmetric 30 degrees freedom insert is labeled S30, a 30 degrees fixed to the left fin is labeled F 30L as examples. SA4 in the scheme denotes intrinsically 3 inserts to fix 3 fins with angles correspondingly to meet the known arrangement of fins having a 4 degrees toe angle.

(19) FIG. 3 shows an alternative embodiment in which the fin [3] has a root section [47] meant to slide into a mating slot [48] extending radially within the substantial extent of a rotating disk base [49] which is to bear in a bearing [50]. In FIG. 3 one sees the fin's axis of rotation [1] and a leading-trailing axis [51] perpendicularly intersecting the axis of rotation [1] at the bottom front end [4] of the fin. The root section [47] is an elongated prism parallel to the leading-trailing axis [51] having cross section in the shape of a symmetric trapezoid [52] which is to be received within a correspondingly shaped mating slot [48] extending radially between an open end [53] on the rim [38] of the disk base [49] and a stop [54] surface near the opposite side of the rim as to have the wider side [55] of the trapezoidal cross section [52] of the root section [47] engage the material between the narrower and wider sides [56] of the trapezoidal mating slot [48]. The disk base [49] has at its underside the disk journal [6], both coaxial with the axis of rotation [1] which are to bear in the bearing [50], the bearing [50] having an exterior side face [13] and an underside face [14] that extend radially from its bore [15] to an outer rim [16] dimensionally fit to meet the bore [17] of a bearing housing [18], the bearing's underside face having means [57] to be releasably secured to the bore [17] of the bearing housing [18], the exterior side face [13] of the bearing flush with the lamination finish (not shown).

(20) In Figure FIG. 4 one sees how the root section [47] is inserted into the top of the bearing's bore [15] which is held inclined to clear the path for the sliding motion [58] to insert the root section [47] into the mating slot [48] to the stop surface [54] at the end of the slot, the root section [47] dimensionally suited to allow a fit matching the geometry of the disk base [49] so that its leading end [59] meet the stop surface [54] and the trailing end [60] of the root section [47] closes the arc [61] of the rim of the base at its open end [53] to then insert the disk base [49] with the root section [47] into the bearing's bore [15] enabling entrapment of the fin with the disk base [49], yet allowing rotation and bearing. Then attaching the bearing [50] into the housing which is fitted correspondingly with means to attach the bearing.

(21) It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, because certain changes may be made in carrying out the above method and in the construction(s) set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

(22) It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall there between.