SAILBOARD FIN RETAINING MEMBER

Abstract: The invention pertains to attachment of a fin (4) to a sailboard or surfboard such that upon being hit by an aftward blow its damage is avoided. Fin holder (5), which is fixed to the sailboard or surfboard, has two longitudinal grooves (6) which receive a pin (3) of the fin and a flat member (1). The fin (4) is attached to the sailboard or surfboard after the pin (3) has been placed in the grooves (6) by a bolt (2) which passes through a portion of the fin (4) and through the flat member (1) while the flat member (1) is retained in the grooves (6). Tightening the bolt (2) clamps the fin (4) to the fin holder (7). The flat member (1) is made no stronger than necessary such that an aftward blow to the fin (4) will either break, or pull the flat member (1) out of the fin holder (5), allowing the fin (4) to pivot around the pin (3) to avoid damage.

Description: SAILBOARD FIN RETAINING MEMBER The present invention pertains to sailboards and surfboards. It improves the usual means for holding fins to the bottoms thereof. 5 PRIOR ART The adjustable fin holder to which the present inven¬ tion applies, which is used in most sail and surfboards, differs only in detail from that of U.S. Patent No. 3, 564, 63£, by W. L. Bahne, Jr. , for ADJUSTABLE SURFBOARD 10 FIN HOLDER, which is incorporated by reference herein. This patent explains why arx adjustable holder is desirable. Present practice differs from Bahne in only two respects: The interior sidewalls of Eiahne' s elongated chan- 15 nel, which converge, and the mating surfaces of Bahne' s fin positioning tongue, which form a matching wedge, have both become parallel-sided. As a result, when the fin is drawn into the channel by a bolt, it is lamped against the bot¬ tom of the channel, instead of being wedged against the £0 sides. In present practice, the sides of the channel con¬ tinue to give the fin lateral support. The clamping means is as shown by Bahne, but today there is only one of them, on the forward end of the fin base. (The rear end is not clamped, but is retained in the £5 channel as described below.) The present invention has to do with this clamping means, especially with Bahne' s "retaining plate". U.S. Patent No. 4, 39β, 485 by Bernard Diziere for DEVICE FOR DETACHABLY SECURING A CENTERBOARD TO A SAILBOARD 30 OR THE LIKE has the same main object as the present inven¬ tion, to protect the fin and sailboard from damage when the fin hits something. Diziere is cited as evidence of long- felt need for this type of protection. Dizi-.re completely replaces the standard Bahne— like adjustable fin holder witπ an incompatible and non-ad¬ justable fin holder. Unlike Diziere, the present invention has the advantages that it can be readily applied to the 5 very many existing surf and sail—boards, and that it retains the advantage of adjustability. BACKGROUND OF THE INVENTION Sailboarding since its introduction in the 1370' ε has 10 become an interna ional sport of major proportions and is considered to be the fastest growing water sport in the world. Sailboards are used in conditions ranging from a slight breeze on a cal lake to gale force winds in rough ocean surf. 15 A sailboard usually consists of a substan ially flat, elongated board, a sail system, an optional ce terboard system, and fixed fin mounted aft. (The fixed fin replaces the rudder of a conventional sailboat. ) Much of the design of the sailboard has been borrowed directly from surf— £0 boards, including the fixed fin. A component originaly designed for surfing that is used almost universally on sailboards is the adjustable fin holder. The adjustable fin holder allows longitudinal adjustment of the fixed fin's position while the board is £5 out of water, as well as easy installation and removal of the fin. Because of the versatility and shallow drafts of sail¬ boards, these craft are often sailed in areas where the aft mounted fin will come into contact with sin underwater ob— 30 struction, such as rock, reef, underwater debris, or the bottom of the sailing area. Damage due to the fin striking an underwater object may result in the following: 1. Breaking of the fin 2. Breaking of the fin holder box 3. Dela ination of the fin holder from the board structure 4. Any combination of the above 5 Replacement or repair of the damage described above is in most cases very costly. It is therefore highly desirable to fasten the fin to the fin holder in such a manner as to protect the fin and more expensive fin fastening components from damaging overloads. 10 SUMMARY OF THE INVENTION The present invention provides a method of securely mounting a fin to an adjustable fin holder while also providing a means of stress relief to the fin, fin holder, 15 and board structure in the event that the fin experiences physical impact from striking an underwater obstruc ion. The invention can be used on any sail or surfboard which has the conventional adjustable finholder, described below. The fin holder used with the invention consists of a £0 rectangular shaped channel which opens flush with the bottom surface of the sailboard. A fin having a lon¬ gitudinal base member fits into the open channel of the fin holder. The fit is laterally snug, so that the parallel sides £5 of the fin holder's channel support the parallel sides of the fin base against sidewise loads, which sire the prin¬ cipal water loads on the fin. In the fore—and—aft direc¬ tion, the channel is commonly more than twice as long as the base of the fin, allowing the fin to take a range of 30 longitudinal positions. The fin holder has two longitudinal grooves running its length, between the bottom of the channel and the open top. ("Top" and "bottom" refer here to the board when upside down for storage or to be worked on. When the board is in use, the closed bottom of the channel is above its open top. ) The fin is secured against being pulled out of the channel at the front and rear of its base member by use 5 of the longitudinal grooves in the fin holder. The secur¬ ing means, described below, serve also to resist the rela¬ tively small water drag on the fin. The rear of the longitudinal base member of the fin contains a permanently fixed pin mounted perpendicularly to 10 the plane of the fin and base member. This pin is inserted upon initial installation of the fin to the fin holder into the longitudinal grooves of the fin holder, thus securing the rear section of the fin against being pulled vertically out of the channel. 15 The longitudinal grooves in the fin holder also house a threaded sliding member into which a bolt passing through the forward end of the base member of the fin is screwed. This secures the forward section of the fin against being pulled out, at the same time resisting longitudinal loads £0 by a clamping ac ion. The slide member which secures the forward section of the fin to the fin holder is to be made of materials which will suffer catastrophic breakage in the event that these components experience sudden severe loads, as would be the £5 case in the event that the fin of the sailboard strikes an underwater obstruction at high speed. Upon the breaking of the slide member, the forward end of the fin base will re¬ lease from the fin holder while pivoting on the pin at the rear of the fin base, the latter still being held within 30 the longitudinal grooves of the fin holder. The release mechanism described will greatly reduce the risk of fin breakage, fin holder breakage, and delamin¬ ation of the fin holder from the board structure. Only a small part will have been broken, one for which replace— 35 merits are easily kept ready and installed. An event which with present equipment would have ended sailing for the da or week is thus reduced to a brief and inexpensiv interruption. 5 BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view of the fin holder with fi inserted and secured. Fin and holder are shown inverted, as they would be upon installation of the fin in a sail board which is ashore and upside down. 10 Fig. £ is a plan view of the fin holder assembl with the breakable threaded slide member installed into th longitudinal grooves of the fin box, looking down at th bottom of the board. Figs. 3 and 4 are side and plan views of th 15 breakable slide member used for fastening the fin to th fin holder. Fig. 5 shows the bolt used for fastening the fin to the slidable member. Figs. 6 and 7 show modified forms of the breakable £0 slide member. Fig. & is sn isometric view of a slide mem¬ ber weakened by scoring. Fig. 7 is a cross section through the center of a slide member to which a threaded metal nut is fixed. £5 DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Fig.l the fin 4 shown inserted into a grooved finbox 5 is of typical confi uration for a surf¬ board or sailboard. 30 The fin holder 5 Fig.1,£ has two longitudinal grooves 6 running its length, between the bottom of its channel and the open top 7. The grooves serve to retain flat member 1, Fig. 1,2,3,4 so that it can slide forward and aft, but cannot escape from the fin holder except by way of vertical grooves 8. Grooves 6 also retain pin 3 Fig.1 by its ends, which project from the sides of the after end of the base of fin 5 4. The ends of pin 3 likewise enter grooves 6 by way of grooves 8 as fin 4 is inserted into fin holder 5. Pin 3 thus secures the after end of fin 4 to fin holder 5, while still allowing fin 4 to slide longitudinally and to rotate about pin 3. lO Bolt £ Fig.1,£, 5, when passed through the vertical hole in the forward end of fin 4, screwed into threaded flat member 1 and tightened, pulls flat member 1 up against the upper surfaces of grooves 6 and cla ps fin 4 down against the bottom of channel 7, thus holding fin 4 to fin 15 holder 5 rigidly and in whatever longitudinal position is desired. My invention provides that flat member 1 be the weak¬ est part of the fin holding system, and that it preferably be brittle as well, so that when overloaded by impact of £0 fin 4 with an underwater obstruction it will fail suddenly and completely. Then it can be replaced easily and at small cost in money and time. Flat member 1 could also be made of a flexible material, thus allowing the flat member to become deformed £5 and allowing its release from the longitudinal grooves of the fin holder in the event that the fin 4 is overloaded by impact. The breaking of flat member 1 allows fin 4 to pivot on pin 3, pin 3 still being retained by grooves 6, thus al— 30 lowing fin 4 to move in an arc—like manner rearward. The release of the fin from the fin holder as ust described will greatly reduce the chance of damage to the fin, fin holder, and delamination of the finholder from the board structure in the event that the fin suffers physical impact 35 from the strikinπ of an underwater obstruction. It should be noted that rny invention is the op¬ posite of present practice, in which flat member 1 is a stainless steel plate and appears to be, judging by the results of repeated accidents, the strongest and most tenacious part of the fin-holding system. As a rule, either the forward end of the fin breaks at bolt £, or fin holder 5 is damaged or pulled loose from the board. That is, the most expensive parts fail, not the cheapest.

Claims: AMENDED CLAIMS [received by the International Bureau on 3 July 1989 (03.07.89) original claims 1-8 amended; claim 9 replaced by claims 10 and 11 (3 pages)] Having described my inven ion I now claims 5 1. Means for securing a fin to the bottom of a sail¬ board in a range of longitudinal positions so as to allow release of the fin upon impact with an underwater obstruc¬ tion for preventing damage to the fin, sailboard, and 10 integral parts thereof, cornprisings a fin having a rectangular longitudinal base member, said base member having a vertical hole in the forward end thereof for accepting a bolt, and a pin mounted therethrou- 15 gh near the rear end thereof a d perpendicular to the plane of said fin and said base member, a fin holder built into said sailboard and comprising a rectangular channel member having parallel opposing £0 longitudinal sides for recieving said ba.se member of said fin for being secured to the bottom of the sailboard, a pair of opposing longitudinal grooves, one in each said opposing side of said rectangular channel member, said grooves being of such dimensions as to .accept the ends of £5 said pin which project from the sides of said base member, thereby retaining said rear end of said b_.se member in said channel member but leaving said base of said fin free to rotate about said pin, 30 and a slide member of such dimensions as to fit slida— bly within and be retained by said grooves, said slide member being adapted to being pulled by said bolt, said bolt being first passed through said ver ical hole in said fin base, thereby securing said fin base member to said 35 channel member by clamping said slide member against the upper surfaces of said grooves in the sides of said channel member, wherein said slide member is of inferior strength compared to the other said members, such that an aftward 5 blow to said fin will cause said slide member to fail first, without damage to other said members. £. The fin securing means recited in claim 1, wherein said slide member is a substan ially flat plate made of 10 brittle material with vertical threaded hole therethrough, adapted to engage said bolt. 3. The fin securing means recited in claim 1, wherein said slide member is a substan ially fϊ.at plate made of ■ flexible material with vertical threaded hole therethrough, 15 such that said slide member will deform and release from said longitudinal grooves o-f said adjustable fin holder in the event of an overload condition. 4. The fin securing means recited in claim £, wherein said slide plate is scored with a sharp groove to cause £0 it to break along said score. 5. The fin securing means recited in claim 1, wherein said slide member is a substan ially flat plate with a nut attached thereto with the threaded hole of said nut verti— £5 cal and adapted to engage said bolt. β. The fin securing means recited in claim 5, wherein the weakest part of said slide member is the attachment of said nut to said substan ially flat plate. 30 7. The fin securing means recited in claim 5, wherein the said nut forms a knife—like edge on which said substan¬ tially flat plate will break under overload. 8. In an adjustable fin holder for securing a fin to a sailboard or surfboard by clamping said fin to said board by pulling on a slide member, said slide member being re¬ tained in said board by a pair of grooves in the sides of a 5 slot in the bottom of said board, the improvement which comprises making said slide member no stronger than necessary to sustain the ordinary loads to which it is subjected, while leaving all parts of said fin and said board somewhat stronger than necessary to 10 sustain ordinary loads, so that overloads resulting from an aftward blow to said fin will break said slide member, while leaving said fin and said board undamaged. 10. fin adjustable fin holder for securing a fin to a 15 sailboard or surfboard by clamping said fin to said board by pulling on a flexible member, said flexible member being retained in said board by a pair of grooves in the sides of a slot in the bottom of said board, said flexible member being no stronger than necessary to sustain the ordinary £0 loads to which it is subjected, while leaving all parts of said fin and said board somewhat stronger than necessary to sustain ordinary loads, so that overloads resulting from art aftward blow to said fin will deform said flexible member, while leaving said fin and said board undamaged, and permit £5 the release of said flexible member from said grooves. 11. The fin holder of claim 10 wherein said flexible member includes a hole therethrough, a bolt extending through said hole, and threaded means associated with said hole for threadably receiving said bolt.

Inventors: LOBE HENRY JOHN, LOBE, HENRY, JOHN
Applicants: LOBE HENRY JOHN, LOBE, HENRY, JOHN
Application year: 1989
Main classification: A63C15
IPC codes: B63B35