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United States Patent |
5,622,134
|
Kelsey
|
April 22, 1997
|
Lifting fin
Abstract
A sloped hydrofoil (22) is mounted to the bottom of a sailboard or
surfboard vertical strut (26) using a hinge joint (24). Hinge joint (24)
allows reversal of sloped hydrofoil (22) slope in response to a hull (30)
side slip. Efficient sloped hydrofoil (22) supports a portion of craft
weight to reduce hull (30) drag.
Inventors:
|
Kelsey; Kevin (11538 Riviera PI NE, Seattle, WA 98125-5921)
|
Appl. No.:
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501414 |
Filed:
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July 12, 1995 |
Intern'l Class: |
B63B 001/24 |
Field of Search: |
114/274,280,39.2
441/74,75,79
|
References Cited
U.S. Patent Documents
3459146 | Aug., 1969 | Prior | 114/66.
|
3747138 | Jul., 1973 | Morgan | 9/310.
|
4320546 | Mar., 1982 | Knox | 441/74.
|
4508046 | Apr., 1985 | Coulter et al. | 114/39.
|
4686922 | Aug., 1987 | Burroughs | 114/124.
|
4715304 | Dec., 1987 | Steinberg | 114/39.
|
4811674 | Mar., 1989 | Stewart | 114/39.
|
5062378 | Nov., 1991 | Bateman | 114/274.
|
5309859 | May., 1994 | Miller | 114/274.
|
Foreign Patent Documents |
2563177 | Oct., 1985 | FR | 114/274.
|
Other References
Morwood, John "Hydrofoil Craft" AYRS #19, Amatuer Yacht Research Society,
Jun. 1958, pp. 24-25.
Grogono, James "Icarus, The Boat that Flies" Adlard Coles Ltd, London 1987
pp. 111-112.
"Now Your Sailboard Can Fly" Popular Mechanics Magazine, Jun. 1983, pp.
72-74.
Garrett, R "Sulu-Mosquito Trimarau MKII" Letter in book by Amatuer Yacht
Research Society Members Sailing Hydrofoils AYRS #74 Hermitage-Berks,
1970, pp. 197-202.
|
Primary Examiner: Sotelo; Jesus D.
Claims
I claim:
1. A hydrofoil assembly mounted on a hull comprising:
(a) a substantially vertical hydrofoil
(b) a single sloped hydrofoil
(c) a hydrofoil hinging means for joining an upper end of said sloped
hydrofoil to the bottom end of said vertical hydrofoil, said hinging means
having a center line substantially parallel to the longitudinal axis of
said vertical hydrofoil
(d) a hinging stop means for limiting said hydrofoil hinging means so that
said sloped hydrofoil assumes a maximum angle of 90 degrees to both sides
of the vertical.
2. The hydrofoil assembly mounted on a hull of claim 1 further including:
(a) a hull in contact with the water
(b) hull attachment means for mounting an upper end of said vertical
hydrofoil to the bottom of said hull
(c) a second substantially vertical hydrofoil
(d) a second single sloped hydrofoil
(e) a second hull attachment means for mounting an upper end of said second
vertical hydrofoil to the bottom of said hull at a different location than
said first hull attachment means
(f) a second hydrofoil hinging means joining an upper end of said second
sloped hydrofoil to the bottom end of said second vertical hydrofoil, said
second hinging means having a center line substantially parallel to the
longitudinal axis of said second vertical hydrofoil
(g) a second hinging stop means for limiting said second hydrofoil hinging
means so that said second sloped hydrofoil assumes a maximum angle of 90
degrees to both side of the vertical.
3. The hydrofoil assembly mounted on a hull of claim 1 further including:
(a) a hull in contact with the water
(b) hull attachment means for mounting an upper end of said vertical
hydrofoil to the bottom of said hull
(c) a substantially horizontal projection from said hull outline, on both
sides of said hull center line, said horizontal projection having an upper
surface on which a plurality of foot strap are mounted.
4. The hydrofoil assembly mounted on a hull of claim 1 further including:
(a) a hull in contact with the water
(b) hull attachment means for mounting an upper end of said vertical
hydrofoil to the bottom of said hull
(c) retraction means for said hull attachment means to allow said vertical
hydrofoil and said sloped hydrofoil to be retracted into a recess in the
bottom of said hull.
5. The hydrofoil assembly mounted on a hull of claim 1 further including:
(a) a hull in contact with the water
(b) hull attachment means for mounting an upper end of said vertical
hydrofoil to the bottom of said hull.
6. The hydrofoil assembly mounted on a hull of claim 1 further including:
(a) a hull in contact with the water
(b) hull attachment means for mounting an upper end of said vertical
hydrofoil to the bottom of said hull
(c) a second substantially vertical hydrofoil
(d) a second hull attachment means for mounting an upper end of said second
vertical hydrofoil to the bottom of said hull at a different location than
said first hull attachment means.
7. A hydrofoil assembly mounted on a hull comprising:
(a) a single sloped hydrofoil
(b) a hydrofoil hinging means for joining an upper end of said sloped
hydrofoil to the hull, said hinging means having a center line
substantially parallel to the longitudinal axis of said sloped hydrofoil
(c) a hinging stop means for limiting said hydrofoil hinging means so that
said sloped hydrofoil assumes a maximum angle of 90 degrees to both sides
of the vertical.
8. The hydrofoil assembly mounted on a hull of claim 7 further including:
(a) a hull in contact with the water
(b) a second single sloped hydrofoil
(c) a second hinging means joining an upper end of said second sloped
hydrofoil to the bottom of said hull at a different location than said
first said hinging means, said second hinging means having a center line
substantially parallel to the longitudinal axis of said second sloped
hydrofoil
(d) a second hinging stop means for limiting said second hydrofoil hinging
means so that said second sloped hydrofoil assumes a maximum angle of 90
degrees to both side of the vertical.
9. The hydrofoil assembly mounted on a hull of claim 7 further including:
(a) a hull in contact with the water
(b) a substantially horizontal projection from said hull outline, on both
sides of said hull center line, said horizontal projection having an upper
surface on which a plurality of foot strap are mounted.
10. The hydrofoil assembly mounted on a hull of claim 7 further including:
(a) a hull in contact with the water
(b) retraction means for said hinging means to allow said sloped hydrofoil
to be retracted into a recess in the bottom of said hull.
11. The hydrofoil assembly mounted on a hull of claim 7 further including a
hull in contact with the water.
12. The hydrofoil assembly mounted on a hull of claim 7 further including:
(a) a hull in contact with the water
(b) a substantially vertical hydrofoil
(c) hull attachment means for mounting an upper end of said vertical
hydrofoil to the bottom of said hull at a different location than said
hinging means.
13. A hydrofoil assembly mounted on a hull comprising:
(a) a surfboard or sailboard fin
(b) a single sloped hydrofoil
(c) a hydrofoil hinging means for joining an upper end of said sloped
hydrofoil to the bottom end of said fin, said hinging means having a
center line substantially parallel to the longitudinal axis of said fin
(d) a hinging stop means for limiting said hydrofoil hinging means so that
said sloped hydrofoil assumes a maximum angle of 90 degrees to both sides
of the vertical.
14. The hydrofoil assembly mounted on a hull of claim 13 further including:
(a) a surfboard or sailboard hull
(b) a finbox, in the bottom of said hull attaching to said fin
(c) a second surfboard or sailboard fin
(d) a second single sloped hydrofoil
(e) a second finbox, in the bottom of said hull at different location than
said first said finbox, attaching to said second fin
(f) a second hydrofoil hinging means joining an upper end of said second
sloped hydrofoil to the bottom end of said second fin, said second hinging
means having a center line substantially parallel to the longitudinal axis
of said second fin
(g) a second hinging stop means for limiting said second hydrofoil hinging
means so that said second sloped hydrofoil assumes a maximum angle of 90
degrees to both side of the vertical.
15. The hydrofoil assembly mounted on a hull of claim 13 further including:
(a) a surfboard or sailboard hull
(b) a finbox, in the bottom of said hull attaching to said fin
(c) a substantially horizontal projection from said hull outline, on both
sides of said hull center line, said horizontal projection having an upper
surface on which a plurality of foot strap are mounted.
16. The hydrofoil assembly mounted on a hull of claim 13 further including:
(a) a surfboard or sailboard hull
(b) a finbox, in the bottom of said hull attaching to said fin.
17. The hydrofoil assembly mounted on a hull of claim 13 further including:
(a) a hull in contact with the water
(b) a finbox, in the bottom of said hull attaching to said fin
(c) a substantially vertical hydrofoil
(d) a hull attachment means for mounting an upper end of said vertical
hydrofoil to the bottom of said hull at different location than said
finbox.
Description
BACKGROUND--FIELD OF INVENTION
This invention relates to sailboats, to sailboards, to surfboards, and to
hydrofoil arrangements which can be used to improve the efficiency and
speed.
BACKGROUND--DESCRIPTION OF PRIOR ART
Nearly all prior art for hydrofoil equipped sailboats, sailboards and
surfboards have sought to raise the hull from the water. This approach
suffers a number of disadvantages:
(a) Close proximity of the hydrofoil to the waters surface and piercing of
the waters surface increases the occurrence of ventilation.
(b) Close proximity of the hydrofoil to the waters surface increases the
occurrence of the foil broaching the surface in waves which may cause
instability.
(c) Close proximity of the hydrofoil to the waters surface reduces the
efficiency of the hydrofoil.
(d) The number of hydrofoil elements required for pitch and roll stability
once the hull is removed from the water increases the complexity of the
design.
(e) The number of hydrofoil elements required for stability increases the
weight of the design.
(f) The number of hydrofoil elements required for stability make retrofit
of a existing hull more complex.
U.S. Pat. No. 4,811,674 to Stewart (1989) utilized hydrofoils to provide
lift without raising a sailboard hull from the water. The hydrofoil
elements were attached to the rail of the hull and were vulnerable to
ventilation and low efficiency due to surface proximity. The hydrofoils
required custom attachment points on the hull or used two thruster finbox
present only on a specialized wave riding sailboard hull or specialized
surfboard.
OBJECTS AND ADVANTAGES
Several objects of the lifting fin are:
(a) simplicity of hydrofoil configuration by using only a single unit;
(b) allow quick and easy mounting and detachment of hydrofoils by having
only one attachment point;
(c) allow retrofit to standard sailboard and surfboard hulls by using the
finbox as the attachment point;
(d) reduce ventilation of the hydrofoil by deep submergence;
(e) give excellent rough water stability by using an immersed hull;
(f) maximize hydrofoil efficiency by deep submergence;
(g) minimize interference drag by separation of hull and hydrofoil;
(h) provide automatic lift control to avoid hydrofoil broaching by use of
sloped hydrofoil;
(i) reduce hull drag by reducing hull planing lift.
Taken together, the above objects lead to the prime object to increase
sailboard and surfboard speed.
Still further objects and advantages will become apparent from a
consideration of the ensuing description and drawings.
DRAWING FIGURES
FIG. 1A shows a perspective view of the bottom or a sailboard or surfboard
hull with a lifting fin.
FIG. 1B shows a perspective view of the top of a sailboard or surfboard
hull with a lifting fin.
FIG. 2 shows an end view of a sailboard or surfboard hull with a lifting
fin.
FIG. 3 shows a side view of a sailboard or surfboard hull with a lifting
fin.
FIG. 4 shows an end view of a sailboard or surfboard hull with an alternate
embodiment of the lifting fin.
FIG. 5 shows a side view of a sailboard or surfboard hull with an alternate
embodiment of the lifting fin.
FIG. 6 shows an end view of a sailboard or surfboard hull with an alternate
embodiment of the lifting fin without a vertical strut.
FIG. 7 shows a side view of a sailboard or surfboard hull with an alternate
embodiment of the lifting fin without a vertical strut.
FIG. 8 shows an end view of a sailboard or surfboard hull with an alternate
embodiment of the lifting fin with two hinge joint.
FIG. 9 shows a side view of a sailboard or surfboard hull with an alternate
embodiment of the lifting fin with two hinge joint.
FIG. 10 shows a perspective view of a sailboard hull with a lifting fin and
a standard retracting centerboard.
FIG. 11 shows a perspective view of a sailboard hull with two lifting fin
spaced fore and aft.
FIG. 12 shows a perspective view of a standard dinghy hull with a lifting
fin daggerboard.
REFERENCE NUMERALS IN DRAWINGS
______________________________________
20 lifting fin
22 sloped hydrofoil
24 hinge joint
26 vertical strut
28 standard fin box
30 standard slalom style sailboard or surfboard hull
32 hinge bulb on sloped hydrofoil
34 hinge bulb on vertical strut
36 hinge pin
40 cross pin
42 bolt
44 cross piece slider
46 hinge stop
48 finbox hinge piece
50 standard sailboard retracting centerboard
60 foot strap
62 foot strap extension platform
64 standard foot strap attachment screws
66 platform foot strap
68 fiberglass cloth
70 lifting fin daggerboard
72 conventional dinghy hull
74 daggerboard trunk
76 hold-down line
______________________________________
Description--FIGS. 1 to 12
In FIGS. 1A and 1B, a standard slalom style sailboard or surfboard hull 30
has a standard finbox 28 and a trio of foot strap 60. A lifting fin 20 has
a vertical strut 26 which is inserted into finbox 28. A hinge joint 24
connects vertical strut 26 to a sloped hydrofoil 22.
FIGS. 2 and 3 show end and side view of hull 30 and lifting fin 20, A hinge
bulb 32 on sloped hydrofoil 22 and a hinge bulb 34 on vertical strut 26
are connected by a hinge pin 36. Vertical strut 26 is attached to finbox
28 using the common methods with a crosspin 40, a bolt 42, and a cross
piece slider 44, Sloped hydrofoil 22 is free to hinge side-to-side
relative to vertical strut 26. Hinge bulb 32 and 34 can be cast or molded
as part of vertical strut 26 and sloped hydrofoil 22, A hole is drilled
through hinge bulb 32 and 34 for hinge pin 36. The swing of hinge joint 24
is limited by the contact on the inside edges of vertical strut 26 and a
hinge stop 45 projecting from hinge bulb 32. Hinge stop 46 can be cast or
molded as part of hinge bulb Rear foot strap 60 is connected to hull 30 by
a pair of standard foot strap attachment screws 64.
FIGS. 4 and 5 show end and side view of hull 30 and an alternate embodiment
of lifting fin 20 to allow fiberglass construction. Vertical strut 26 and
sloped hydrofoil 22 are constructed of fiberglass to reduce weight. Hinge
bulb 32 and 34 and short lengths of hydrofoil are cast or molded of metal
to withstand the high stress in hinge joint 24. Hinge bulb 32 is joined to
vertical strut 26 by several layers of fiberglass cloth 68 wrapped around
the outside of vertical strut 26 and the short length of hydrofoil that is
part of hinge bulb 32, Epoxy resin is used to ensure a good bond to the
metal. Hinge bulb 34 is joined to sloped hydrofoil 22 by the same method.
FIG. 5 also shows vertical strut 26 and sloped hydrofoil 22 with a sweep
forward angle, This sweep angle increases the angle of attack of sloped
hydrofoil 22 while not hanging the angle of attack of vertical strut 26.
FIGS. 4 and 5 also show end and side views of hull 30 and an additional
element in place of rear foot strap 60. A root strap extension platform 62
is mounted to hull 30 using two standard foot strap screws 64 which
normally attach rear root strap 60. Platform 62 is angled up out of the
water and has three foot strap 66 on its upper surface.
FIGS. 6 and 7 shows end and side view of hull 30 and an alternate
embodiment of hinge joint 24. Hinge joint 24 is located at finbox 28 and
vertical strut 26 is eliminated. A finbox hinge piece 48 is connected to
finbox 28 in the usual manner instead of vertical strut 26. Hinge stop 46
now hits against the bottom of finbox 28.
FIGS. 8 and 9 show end and side view of hull 30 and an alternate embodiment
with two hinge joint 24. A second hinge joint 24 at finbox 28 is added to
the top of vertical strut 26.
In FIG. 10, hull 30 has finbox 28 and lifting fin 20 and a standard
sailboard retracting centerboard 50. Centerboard 50 is located in the
standard position on hull 30.
In FIG. 11, hull 30 has two finbox 28 and two lifting fin 20 mounted fore
and aft on hull 30 centerline.
FIG. 12 shows an alternate embodiment with a lifting fin daggerboard 70
retrofit to a conventional dinghy hull 72. Hinge joint 24 can be made
small enough, with the much larger size of a daggerboard, to be retracted
up through a daggerboard trunk 74 in dinghy hull 72. A hold-down line 76
is used to hold lifting fin daggerboard 70 from rising in daggerboard
trunk 74.
Operation--FIGS. 1 to 12
FIGS. 1A and 1B shows slalom style sailboard or conventional surfboard hull
30 with one lifting fin 20 providing all directional stability and side
force generation. The sideslip of hull 30 when propelled by a sail (not
shown), or sliding down a wave, causes hinge joint 24 to swing to
windward, or upward to the crest of the wave. Vertical strut 25 then
generates sideforce and sloped hydrofoil 22 then generates both sideforce
and upward lift.
When the sailboarder tacks or jibes, the new sideslip direction swings
hinge joint 24 to the opposite side. When the surfboarder cuts back to
reverse direction, the new sideslip direction also swings hinge joint 24
to the opposite side.
FIGS. 2 and 3 show hinge stop 46 which limits the swing of hinge joint 24.
In practice, an angle from vertical of 45 degrees has given best
performance. The angle of attack of sloped hydrofoil 22 is set by a
combination or hull side slip and hull pitch trim. Thus the angle of
attack is less dependent upon either sideslip or hull trim and reduces the
occurrence of stalling from excessive hull pitch trim.
The upward lift generated by lifting fin 20 is far aft. Upward lift is also
far aft when the crew uses the sailing method called riding the fin which
is used in strong winds to increase performance. When riding the fin, the
standard fin and the tail of hull 30 are the only contact with the water.
The crew maintains control when the upward lift is far aft. Sailboard and
surfboard riders will move further aft without sinking the tail of hull
30.
In FIGS. 3 and 4, foot strap extension platform 62 can be used for the rear
crew foot to give the crew leverage to prevent hull capsize. The increased
span of lifting fin 20 increases the hull capsize moment that rolls hull
30 to lee when sailing or surfing at high speed. The crew weight to
windward on platform 62 creates a moment to counter the capsize moment of
lifting fin 20.
FIG. 5 shows the use of sweep forward angle to increase the angle of attack
of sloped hydrofoil 22. The increased angle of attack makes sloped
hydrofoil 22 generate a larger portion of the side force and increases the
vertical force generated. The angle of attack of sloped hydrofoil 22 can
be set so sloped hydrofoil 22 can generate nearly all the side force, with
the lift of vertical strut 26 near zero, and the vertical lift generated
by sloped hydrofoil 22 is maximized. Vertical strut 26 still provides
directional stability in this situation.
FIGS. 6 and 7 show an alternate embodiment of lifting fin 20 with vertical
strut 26 replaced by finbox hinge piece 48. Due to the close proximity of
hull 30 and sloped hydrofoil 22, small slope angles are used to reduce
interference draft. The design gives some vertical lift, a normal hull
capsize moment, and less fin area. The design is specialized for higher
wind speed when added vertical lift isn't necessary to encourage planing
of hull 30.
FIGS. 8 and 9 shows an alternate embodiment of lifting fin 20 with two
hinge joint 24. This allows both vertical strut 26 and sloped hydrofoil 22
to generate vertical lift.
FIG. 10 adds centerboard 50 to increase side slip resistance in light
winds. This improves windward performance in light wind and centerboard 50
can be retracted in strong wind when no longer required.
FIG. 11 shows an alternate embodiment with two lifting fin 20 mounted on
hull 30. Forward finbox 28 is mounted at the standard location of
centerboard 50. The forward lifting fin 20 gives upward lift and sideslip
resistance instead of just the sideslip resistance of centerboard 50 to
reduce light wind planing speed. This configuration allows use of two
smaller lifting fin 20 rather than a very large area lifting fin 20 for
light wind planing.
Generally, sloped hydrofoil 22 is equal in size and area as vertical strut
26. Using sloped hydrofoil 22 much larger than vertical strut 26 greatly
reduces directional stability.
Generally, the best lifting fin 20 size for a given sailing or surfing
condition has vertical strut 26 area equal to that of the standard fin
that would be used for the conditions.
Summary, Ramifications, and Scope
Lifting fin 20 design in FIGS. 1A and 1B is very simple and practical.
Using the stability of immersed hull 30, the hydrofoil configuration can
be reduced to a single element rather than require multiple elements.
Lifting fin 20 is quick and easy to mount and detach as it is small in size
and it is a single unit, It is no more inconvenient to mount than the
standard fin (not shown) it replaces. Quick mounting allows interchange of
hydrofoil sizes or use of a standard in (not shown) to suit the changing
sailing or surfing conditions for maximum performance.
Lifting fin 20 completely retrofits to standard sailboard and surf board
hulls 30 using finbox 28 present on all hulls. This allows all
sailboarders and surfboarders to inexpensively take advantage of hydrofoil
performance increase using their existing hull 30.
Lifting fin 20 reduces ventilation by deep submergence of sloped hydrofoil
22 by its attachment to the bottom of vertical strut 26. Ventilation of
vertical strut 26 is reduced as it is not surface piercing as it is
mounted to the bottom of hull 30 which remains immersed in the water. In
practice, when ventilation of vertical strut 26 does occur, the ensuing
spin-out is less severe and easter to recover from. Hull 30 is easier to
turn downwind, or towards the bottom of the wave being surfed, for spin
out recovery as the deeply submerged sloped hydrofoil 22 retains some lift
that maintains some directional stability of hull 30.
Lifting fin 20 gives excellent rough water stability by taking advantage of
hull 30 excellent rough water stability.
Lifting fin 20 maximizes hydrofoil efficiency by deep submergence of sloped
hydrofoil 22 by its attachment to the bottom of vertical strut 26. Also,
sloped hydrofoil 22 adds span length to vertical strut 26 to increase the
aspect ratio and thus the lift to drag ratio.
Lifting fin 20 minimizes interference drag by using only one hull
attachment point; finbox 28. Also, vertical strut 26 attaches to hull 30
at right angles for lower interference drag. In addition, sloped hydrofoil
22 is spaced away from hull 30 by vertical strut 26 to minimize the
interference drag between hull 30 and sloped hydrofoil 22.
Lifting fin 20 gives automatic lift control to avoid hydrofoil broaching.
The slope angle of sloped hydrofoil 22 makes the upward force generated a
fixed percentage of the sideforce generated by sloped hydrofoil 22. As the
total sideforce generated by lifting fin 20 is always less than total
craft weight, the upward lift of sloped hydrofoil 22 is always less than
total craft weight. Thus, lifting fin 20 avoids hydrofoil broaching by not
lifting hull 30 off the water.
Lifting fin 20 reduces hull 30 drag. The vertical dynamic lift of the
deeply submerged sloped hydrofoil 22 has a higher lift to drag ratio than
planing hull 30. Sloped hydrofoil 22 vertical lift reduces required hull
30 planing lift and thus reduces hull 30 drag.
As a result of the advantages above, sailboard and surfboard speed is
increased.
The vertical lift of lifting fin 20 reduces the water speed required for
planing, thus adding low speed performance to a given size of hull 30. The
optimum wind speed range, or surfing wave size, for a given hull 30 design
is extended by use of lifting fin 20. This makes a single hull 30 more
versatile, possibly eliminating the need for a second hull 30 size to
cover the lower speed range.
The lower planing speed makes it easier for the crew to pump the sail (not
shown) in order to propel hull 30 onto a plane.
The use of a very large sloped hydrofoil 22 allows planing of small hull 30
in very light winds. Instead of using a Larger more buoyant hull 30 in
light winds, the crew maybe just as fast by using a small hull 30 and
switching to lifting fin 20 with a very large sloped hydrofoil 22.
In practice, lifting fin 20 adds excellent sailboard windward performance
pointing ability when planing and subplaning. The lower speed that planing
occurs with lifting fin 20 allows the crew to sail a higher course to the
wind while maintaining a plane. In very light winds, lifting fin 20
greatly improves windward sailing ability when hull 30 is rolled to
windward about 20 degrees to increase lifting fin 20 depth to its maximum.
The improved windward ability allows the crew to more easily return to
shore when the wind drops, thus making the use of a small hull 30 more
practical in gusty winds.
In practice, lifting fin 20 improves control by increasing directional
stability. It is much easier to prevent hull 30 from rounding up into the
wind. At subplaning speeds, the crew can remain aft on hull 30 in foot
straps 60 and lean forward with the sail (not shown) to steer hull 30 out
of the wind. The crew can thus be in foot strap 60 ready to sail at high
speed in the next gust of wind. This increases the ease or sailing. The
crew no longer needs to leave foot strap 60 and move forward on hull 30
every time hull 30 stops planing. The crew can remain in root strap 60
without sinking the tail of hull 30 or having hull 30 turn into the wind.
The crew can remain in foot strap 60 while not planing, while pumping the
sail to help start planing and to remain in a position to prevent the sail
from pulling the crew over the bow in the next gust of wind.
Although the description above contains many specificities, these should
not be construed as limiting the scope of the invention, but as merely
providing illustrations of some of the presently preferred embodiments of
this invention. For example, mechanisms can be used to adjust the sweep
forward angle of lifting fin 20 shown in FIG. 5 for different sailing or
surfing conditions. Thus the scope of the invention should be determined
by the appended claims and their legal equivalents, rather than by the
examples given.
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