CA2276926A1 - Finboard - Google Patents

Abstract

The finboard is a muscle powered personal water craft, comprising an elongated buoyant body (the board) and two horizontal fins attached to said body by elastically restrained hinges. When the board is in use, the user stands on its deck, balancing and controlling it by the help of a vertical shaft, securely attached to said deck terminating in a horizontal handle bar.
Forward motion is achieved by the user lowering and raising his center of gravity by flexing his knees repeatedly. The board, in reaction to the periodic downward momentum, reacts by alternately sinking deeper into the water then rising higher again. The fins, due to the resulting hydrodynamic pressure against their surfaces, respond to this vertical oscillation by adapting a periodically changing slanted attitude which converts each vertical displacement of the board to a horizontal forward driving momentum.

The fact that the fins offer a continuous drive (as opposed to the intermittent drive of paddling) combined with the fact that oscillating fin drives are known to be more efficient than either paddles or propellers, endow this invention with the potential of becoming the fastest muscle-powered water craft.

Description

Name of the inventor: Thomas E. Tomosy Name of the invention: FINBOARD
SPECIFICATION
This invention relates to fin-driven recreational watercraft and more particularly to watercraft having one or more horizontal flexible fins, and kept in dynamic balance, driven forward and maneuvered entirely by the actions of the user.
Presently proposed fin-driven craft tend to use mechanical devices analogous to either fish or marine mammal anatomy. That is, the driving fin is flexibly suspended on the end of a beam which is pivoted inboard and swept horizontally for vertical fins and vertically for horizontal fins. In designs where the beam is eliminated and the fin is pivoted at or close to its leading edge, the result is gross inefficiency. Fins at the end of a long beam, on the other hand, often need complicated support mechanism and/or stabilizers which add to the hydrodynamic drag and again result in inefficient operation.
The present invention overcomes these difficulties by proposing a simple integrated design, with a minimum of moving parts whereby one or more fins are attached by elastically restrained hinges to a suitably shaped buoyant body (the board). A vertical rhythmic displacement is imparted to the complete apparatus--including the fins--by the user by lowering and raising his center of gravity by flexing his knees. The fins, due to their elastically restrained hinges and the resultant hydrodynamic pressure, assume a slanted attitude that converts each vertical displacement of the board to a horizontal forward driving momentum.
The shape of the buoyant body is such that it is able to move efficiently through water in a vertical direction in addition to the longitudinal direction. Hydrodynamic drag is further reduced by a simple and clean design with no beams, arms, stabilizers or other extraneous components.
The principle object of the invention is to provide a muscle-powered water craft that is fin driven, is fast and has the potential of becoming the fastest muscle-powered water craft.
Another object of the invention is to provide a sports instrument for the water lover that depends entirely on the sportsman's muscles and reflexes for operation.
The finboard lends itself readily to free-style tricks that can be developed by future users of the invention, thus it offers non-ending fun and challenges for those who embrace this proposed new sport.

In drawings which illustrate embodiments of the invention, Fig. 1 is a side elevation of the finboard, Fig. 2 is a top plan view thereof, Fig. 3 is a rear view thereof, Fig. 4 is a fragmentary enlarged section taken on line A-A, and shows details of one elastically restrained hinge with a removeable bottom section, Fig. 5 is a perspective exploded view showing parts of said hinge, Fig. 6 is an enlarged cross section thereof taken on line B-B, Fig. 7 is a fragmentary longitudinal enlarged section of the board showing the detachable handle shaft and reinforcements of the shaft socket, and fig. 8 is a perspective view of the finboard in actual use.
On fig. 1 through 3, the buoyant body (the board) 1 is made from materials and by methods generally adapted for use in building surfboards or sailboards. I.e. the core is made from expanded polystyrene or polyurethane rigid foam.
Laminated glass, graphite, or Kevlar fabric in a synthetic resin matrix forms the skin. Reinforcement in the form of extra layers of said skin materials is required not only on the deck 2, but on both sides of the board where the user stands and exerts extra force thereto. Said deck is rounded off at its edges, padded and lined with non-slip material to offer a strong gripping surface, and at the same time prevent injuries to the user should he lose his balance and fall.
Fig's 1 through 3 show that the shape of the board 1 is narrow and deep with the sides of the board coming to relatively sharp edges all around except on the deck where the user stands. Such shape is necessary for streamlining said board in the vertical direction to offer minimum hydrodynamic drag to the vertical oscillation of said board. Further benefits of the deep and flat shape is that it improves balance as well as allows the fins to be mounted deeper down in the water. The relatively sharp edges are necessary especially at the front as the bow of the board is slicing through the water/air boundary as it oscillates through the water. However, the edges must not be as sharp as to being potentially injurious to the user or others who come in contact with it.
Fig. 2 shows the narrow, streamlined shape of the horizontal section. From Fig. 1, 2 and 3, it is evident that the center of buoyancy is well under water, and the water line falls just under said deck 2 where the cross section is the narrowest. This ensures that the downward momentum exerted by the user is used to flex the fins to drive the board forward rather than used up in counteracting buoyancy or hydrodynamic drag.

The fins 5 and 6 are attached to the bow and stern of the board by elastically restrained hinges shown on fig's 4 through 6. Said hinges pierce the bow and stern of the board 1 at points where said board is just wide enough to provide sufficient leverage without breaking against the twisting forces generated by hydrodynamic pressure during use (about 7cm wide). The forward fin 5 has an essentially zero degree of effective angle of attack with respect to the waterline. When the user imparts driving pulses close to the center of buoyancy, the forward fin 5 as well as the rear fin 6 are both driving the craft forward. When the user steps back toward the stern and applies driving pulses there, the front fin 5 acts as a stabilizer of the bow while the stern together with the rear fin 6 oscillates and drives the craft forward. In this mode of operation, the front fin provides a pivot point. The positive angle of attack of said rear fin 5 together with the buoyancy of the board 1 ensures an easy and fast upward rise of the stern after it has been driven downward by the user.
Depending on the attitude of the board 1, the rear fin 6 has an effective angle of attack of about four degrees.
Fig's 4 and 5 show the elastically restrained hinge parts as well as the removable bottom section 7. The rubber moldings 8 and 9 are pinched in between the spine 10 of said fin and the restraining upper 11 and lower wedges 12 in the hinge cavity. Thus, said rubber mouldings elastically limit the angle changes said fins are capable of achieving. Holes or cavities are provided in said rubber mouldings to allow for bulging under compression. Said rubber mouldings, by different dimensions and rubber composition are able to influence the maximum deflection as well as the effective angle of attack of said fins. In effect, by using different rubber inserts, the operating attributes of the board can be fine-tuned to match the user's weight, strength or preferences. The bearing disks 12 and 13, by riding the outside rims of the bearing cylinder 15, provide the necessary support and hinging action for said fins. Said bearing disks are moulded onto the spine 10 of the fins or glued on by strong adhesive, without structurally altering said spine.
Fig. 4 shows that by unscrewing the captive bolts 16, the lower hinge section 7 can be removed for dismounting the fins or for replacing the rubber mouldings. The hinge mouldings 7 and 18, as shown on fig's 4 and 6, are made of strong reinforced plastic or fiberglass. Said mouldings have sides where the final skin laminate 19 is able to adhere to.
Said fins 5 and 6 are composed from a solid but light core such as softwood laminate or non-compressible plastic foam, covered by glass, Kevlar or carbon fiber composite skin.
The spine 10 of said fins are made of solid and strong material such as solid fiberglass. The lobes 17 of said fins taper toward the tips as well as toward the trailing edges.
The resultant flexing of said fins under hydrodynamic pressure reduces tip vortexes and overall drag.

The handle assembly, comprising the handle shaft 3 and handle bar 4, is solidly attached to the board. The approximate height of said handle bar 4 is that of the user's hip. Said handle assembly aids the user in keeping his balance relative to the board as well as balancing and maneuvering the board relative to the water. Said handle shaft is made from at least 1 and 1/4 inch diameter of good quality aluminum alloy or stainless steel tubing. Said handle bar on top of said handle shaft may be welded onto said shaft. For the sake of transportation, said handle assembly is detachable. Fig. 7 shows the reinforcement of the board for receiving the handle shaft. The board 1 is drilled through from side to side at the level where the bottom end of the shaft is, and a bolt is inserted through said holes in the board and shaft to solidly anchor said shaft. The reinforcement on said deck may be made from laminated wood 20 or from many extra layers of skin material. At the bottom end of the shaft, the reinforcement may be a wooden block 21 wide enough to be bonded directly to the skin material. An epoxy-glass tubing 22 connects the top and bottom reinforcements, and acts as a guide when said handle shaft is inserted as well as a sealant against water seepage.
A beginner starts the finboard by walking into waist-deep water with the broad laying on its side on top of the water.
The user pulls himself up onto the side of the board and kneels up. With one hand he pushes the forward fin down while with the other he pulls the handle shaft up. As the board uprights itself, he pulls himself up on top of the board to sit astride thereof. He then leans forward and hooks one foot over the top of the board behind his back and kneels up on one knee, he then stands up taking care to keep the center of his weight over the center of buoyancy and to keep the handle shaft vertical and close to his body. (For most people, it takes a few hours of practice to learn this maneuver.) An advanced user holds the board upright in shallow water.
Holding the handle bar, he jumps up onto the deck to kneel on one knee, then stands up. Or, in deep water, he can upright the board by standing on its side, passing over the intermediate sitting and kneeling positions.
Forward drive is achieved by the user flexing his knees to cause the board oscillating vertically. As the board picks up speed, he steps further and further back on the deck to impart the driving impulses to the rear fin. In this case the forward fin acts as a stabilizer to keep the bow on a level ride. The craft can also be driven forward by rolling the board from side to side or by rocking it forward and aft. To turn, the user banks the board into the turn, he pushes the bow down deep into the water, then reverses the bank and steps back to load the stern and to bring up the bow. This cycle is repeated about twice for a 90 degree turn. Spectacular free-style turns are possible.

Claims (9)

1. A water sports device comprising a buoyant body equipped with at least one horizontal fin (driving fin), said fin has means for automatic adjustment of its angle of attack and means for vertical periodic displacement for propulsion thereof.

2. A water sports device as in claim 1 whereby said fin is attached at or near to the stern of said buoyant body by hinge means providing a fixed pivoting point for said fin thereby restricting movement thereof with respect to said buoyant body to elastically limited angular displacement, further the bow of said buoyant body has means for vertical stabilization.

3. A water sports device as in claim 1 and 2 where said automatic adjustment of said angle of attack is provided by alternating hydrodynamic pressure against the lower and upper surfaces of said fin, where said hydrodynamic pressure is due to said periodic vertical displacement of said fin and works in cooperation with said elastic restrainment of said hinge means.

4. A water sports device as in claim 1 whereby said buoyant body consists of a main portion which, in use, is effectively under the water line, and a deck portion, for standing thereon, which is above the water line, said deck portion is attached to said main portion by a neck portion of minimum buoyancy, a handle shaft is secured to said deck portion rising vertically therefrom and terminating in a horizontal handle bar at its upper extremity providing handhold means for the user.

5. A water sports device as in claim 3 where the power component of said periodic displacement force is provided by the weight and downward momentum of the user, and where the return component is provided by the combination of buoyancy and a positive effective angle of attack of said driving fin.

6. A water sports device as in claim 2 whereby said hinge means consist of a bearing cylinder solidly and transversely secured to said buoyant body and two bearing disks secured onto said spine of said fin located therewithin and supported by said bearing cylinder, two restraining wedges are secured to the inside wall of said cylinder at opposite sides protruding in between said bearing disks, in each of the cavities defined by the two bearing disks, the spine of fin and one side of one restraining wedge an elastic member is inserted which are being compressed between the spine of said fin and said restraining wedges to bring about said elastic limitation of angular displacement of said fin.

7. A water sports device as in claim 2 and claim 4 whereby said fin and said handle assembly are detachably attached to said buoyant body.

8. A water sports device as in claim 6 whereby said elastic members are replaceable two-component polyurethane rubber mouldings having suitably shaped cavities to accommodate bulging of the rubber under compression thereof.

9. A water sports device as in claim 6 and claim 7 whereby said bearing cylinder is longitudinally split into two halves, one of the halves is secured solidly to said buoyant body, the other half is secured solidly to a detachable section of said bouyant body, whereupon inserting said fin and said rubber mouldings therebetween, the two halves are joined by means of removeable fasteners.