PLANCHE A DERIVES

FINBOARD

Abrégé anglais

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.

Revendications

The embodiment of the invention in which an exclusive
property or privilege is claimed are defined as follows:
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.

Description

CA 02276926 1999-07-09
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.

CA 02276926 1999-07-09
2
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.

CA 02276926 1999-07-09
3
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.

CA 02276926 1999-07-09
4
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.

Dessin représentatif