Note: Descriptions are shown in the official language in which they were submitted.
CA 02620314 2007-12-12
Title of the Invention
A Sailing Craft Comprising a Tilting Rigid Sail System
Cross-references to Other Applicatians
N/A
Field af the Invention
This invention pertains to sailing craft and tilting sail systems and more
parricularly to a
sailing craft comprising a tilting rigid sail system.
Background of the Invention
Sailing craft and sail systems are well known. The idea of putting a rigid
aer4foil-type
sail on a sailing craft is discussed in U.S. Patent 2,170,914 issued to
Rurnrnler and I.T.S.
Patent 1,670,936 issued to M. McIntyre et al. The primary problem associated
with these
craft and sail systems pertains to "stayine' the sails and rigging using
cables and rope
while allowing active portions to move freely in order to operate properly. As
illustrated
by U.S. Patent 4,068,607 the cable-based rigging and stay controls are very
complicated
and difficult for a small crew or single operator to operate.
What is therefore required is a rigid sail system that can be operated with a
minimum of
stays and rigging by one operator or a small crew.
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Ub eetfves and Advantages of my Invention
My invention is a novel and ingenious improvement to the present rigid sail
systems with
the following objectives and advantages:
"t. The sail shape does not depend on the wind and it maintains a constant
curvature regardless of wind speed or direction for maximum generation of
thrust;
2. The constant sail shape allows the sail craft to be sailed "close to the
wind"
resulting in quicker tacks, fewer stalls and optimized forward thrust;
3. The sail system operates without a boom that swings low amidships;
} 0 4. The sail system is self-weather cocking to the mast and will turn into
the
wiiid automatically;
5. The sail system controls are simple and may be confined to a single winch
operable by a single operator;
6. The sail system permits more sail area than traditional soft sails because
the
] 5 rigid sail system can be angled to reduce heel and has a low centre of
effort;
7. The control of the heel of the sail craft is accomplished in three ways:
through
the manipulation of sail tilt, the mainsheet and the rudder;
8. The rigid sail system permits the craft to lift from the water and
therefore
increases speed of the craft by reducing hull drag;
20 9. The rigid sail system offers a simplified control for one operator or a
small
crew;
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10. The rigid sail system exemplified herein can be applied to craft of all
sizes
from toy vessels to large cargo vessels with a varying configuration of hulls,
such as, mono and multi hulls;
11. The rigid sail system exemplified herein can be operated by computers with
wind speed and direction sensors to automatically adjust the sails for
optimized thrust. This can save significant fuel costs for commercial vessels;
and,
12. The large surface area of the rigid sail is adaptable to coverage by
flexible
photo-voltaic cells perrmitting power generation for the electrical needs of
the
craft.
Summarv of the Invention
To overcome the deficiencies in prior art rigid sail systems and accomplish
the objectives
set out herein, my invention is a sail craft comprising a tilting rigid
sailing system. The
sail craft has a hull having a bow and a stern, a port side and a starboard
side. The tilting
sail system comprises a sail comprising an aerofoil member capable of omni-
directional
attitude for wind propulsion. The aerofoil member is supported by support
means for
fixing the aerofoil member to the sailing craft and permitting omni-
directional attitude.
The aerofoil member is controlled by control means for placing the aerofoil
member in a
forward propulsion attitude relative to wind direction.
The aerofoil member is rigid and. has an asymmetric shape and is self weather
cocking to
the mast.
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The aerofoil member compiises a leading edge, a trailing edge, an upper
camber, a chord,
a span, a centre line, a port side, a starboard side and a chord line. The
span is generally
greater than the chord. In one example of the invention, the aerofoil member
has a first
chord at the leading edge and a second chord at the trailing edge. The second
chord is
larger than the first chord.
In one example of the rigid sail system described herein, the aerofoil member
further
includes framing means adapted to maintain the asymmetric shape of the
aerofoil
member. The covering of the aerofoil member may be hard or soft. The aerofoil
member
support means comprises a vertical mast having a bottom end fixed to the hull
of the craft
and top end for mounting the aerofoil niember. Tliere is also at least one
stay member
fixed between the vertical mast and the hull to provide stability to the
vertical Ynast.
] 5 Aerofoil member control means for placing the aerofoil member in a forward
propulsion
attitude relative to wind direction comprises means for controlling the
attitude of the
aerofoil member for optimizing aerofoil inclination and surface area to Nvi.nd
direction.
Means for controlling the attitude of the aerofoil member comprises: Swivel
and pivot
means connecting the second end of the vertical mast to the aerofoil member
permitting
the aerofoil member to adopt a pluta.lity of desired inclination angles; and,
control means
for placing and maintaining the aerofoil member to adopt one of the plurality
of desired
inclination angles.
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In one example of my invention. described herein the swivel and pivot means
comprises:
a mounting member fixed to the framing means for mounting the swivel and pivot
means
to the aerofoil member; damping means fixed to the swivel and pivot means and
disposed
within the second end of the verdcal mast for damping forces induced into the
swivel and
pivot means by wind; swivel means for permitting the aerofoil member to swivel
around
the vertical mast; and, pivot means for permitting rotation of the aerofoil
member about
the chord line.
In another example of my invention described herein the damping means
comprises: a
first member disposed within the verfical mast proximate to the second end; a
damping
spring disposed within the vertical mast, wherein the damping spring member
has a first
end and a second end, and wherein the first end rests upon the base member; a
second
member disposed within a third meniber, wherein the second fnember rests upon
the
second end of the damping spring member and is adapted to transfer the forces
from the
swivel and pivot means to the damping spring; and, the third member having a
first end
adapted to receive the second end of the damping spring and a second end fixed
to an
axle, wherein the third member is further adapted for telescopic placement
within the
second end of the vertical mast thereby permitting reciprocating movement of
the third
member relative to the vemcal mast in reaction to the forces.
In another example of the invention described herein, the swivel means
comprises the
axle attached by the pivot means to the aerofoil member. The axle is fixed at
its midpoint.
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to the third member second end and the third member is disposed telescopically
within.
the vertical mast second end so that it is permitted free rotation about the
vertical mast.
In one example of the invention described herein, the pivot means comprises
the axle
mounted in a rotational relationship with a first and second yoke. The first
and second
yoke are mounted to the mounting member and the pivot means permits rotation
of the
aerofoil member about the chord line.
Tn another example of the invention described herein the aerofoil control.
means
] 0 comprises a first control line having a first end fixed to the leading
edge and a second end
anchored to the veitical mast at a point proximate to the first end. The first
control line is
tensioned to control pitch of the aerofoil member. The control means further
comprises
aerofoil member tilt cotrtrol comprising a second control line having a first
end fixed to
the aerofoil member between the port side of the craft and the vertical mast
and a second
end fixed to the aerofoil member between the starboard side of the craft and
the vertical
mast. This creates the second control line port length and starboard length.
The second
control line travels down-mast to a set of pulleys mounted on the mast and to
a two-way
winch adapted to tension alternately the port length and the starboard length
of the second
control line, thereby tilting the aerofoil member port and starboard as
desired. The spring
tension on the winch is to keep the tilt control line tight to help stabilize
the sail and to
keep the rope tight enough to provide friction for the rope on the winch drum.
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In another example of the invention described herein, the control means
further
comprises a third control line having a first end fixed to the aerofoil member
between the
trailing edge and the vertical mast, and a second end fixed to port-starboard
traveling
means fixed across the stern of the water craft. The traveling means is
adapted to move
from port to starboard so that the aerofoil member can be rotated about the
vertical mast
and secured in a desired position.
These and other objects, features, and characteristics of my invention will be
more
apparent upon consideration of the following detailed description and appended
claims
with reference to the accompanying drawings, wherein like reference numerals
designate
corresponding parts in the various figures.
Brief Descriutivn of the Drawinas
Figure 1 is a side view of one example of my invention.
Figure 2 is a side view of the aerofoil member and mast of another example of
my
invention,
Figure 3 is a side view of another example of my invention showing the sail in
a tilted
configuration.
Figure 3a is another embodiment of my invention showing floatation means in
the sail.
Figure 4 is a view of the swivel and pivot means of one example of my
invention.
Figure 5 is a front view of another example of my invention.
Figure 6 is a top view of one example ofmy invention.
Figure 7 is another top view of one embodiment of my invention.
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Figure 8 is a perspective view of another embodiment of my invention.
Figure 8a is a perspective view of an embodiment of my invention showing
floatation
means in the sail.
Figure 9 is a view of my inventi on mounted to a catamaran hull.
Figure 10 is a view of my invention mounted to a large cargo vessel.
Detailed Descrintion
Referring to Figure l there is shown in side view my invention, a sailing
craft 10
comprising atilting sail system 12. The sailing craft 10 has a hull 14 having
a bow 16
and a stern 18, a starboard side 20 and a port side 22. Also illustrated are
rudder 23, tiller
arm 25 and kee12']. The tilting sail system 12 comprises a sail 24 comprising
an aerofoil
member 26 capable of an omni-directional attitude for wind propulsion. The
aerofoil
member 26 is supported by support means 28 for fixing the aerofoil member 26
to the
sailing craft 10 and permitting an omni-directional attitude of the aerofoil
member. The
tilting sail system further comprises aerofoil member control means 30 for
placing the
aerofoil member 26 in a forward propulsion attitude relative to wind
direction. The
aerofoil member is rigid and has an asymmetric shape. The aerofoil member is
self
weather cocking, that is, it will always turn itself into the wind.
Referring to Figures 2 and 3, the aerofoil member 26 comprises a leading edge
32, a
trailing edge 34, an upper camber 36, a chord 38, a span 40, a centre line 42,
a starboard
side 44, a port side 46 and a chord line 48. The span 40 is greater than the
chord 38. The
aerofoil member has a top covering or skin the bottom surface of which is show
at circle
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37. The aerofoil member also has a bottom skin, which is shown partially as
the lines at
arrow 33. The bottom skin improves performance of the aerofoil by up to 30 o
in terms
of thrust generated and has been removed in Figure 3 to show the in.ternal
consmuction of
the aerofoil member.
In one embodiment of the invention, the chord 38 at the leading edge 32 (first
chord) is
the same as the chord (second chord) at the trailing edge 34. In another
embodiment of
the invention the aerofoil member has a trailing edge (second) chord 39 that
is larger than
the leading edge (first) chord.
The aerofoil member 26 further includes framing means 50 adapted to maintain
an
asymmetric shape.
In a conventional sailing system, to stop the craft with soft sail the
operator must either
turn the craft into the wind or let the sail out with the main sheet to let it
luff in the wind.
This has the effect of aerodynamically braking the craft. In a high wind
situation the soft
sail will thrash about severely and needs to be taken down or furled in. With
the rigid
sail of the present invention the operator can let out the main sheet and let
the rigid sail
turn with the wind. It will not thrash about because it is rigid. The other
option for the
operator isjust to tilt the rigid sail to a more horizontal position which
will lessen the
forward drive force and make the rigid sail more vertical. The aerodynamic
flow over the
sail remains smooth without the sail thrashing. There is no need to furl the
rigid sail.
To level the craft into a more horizontal pla.ne, the rigid sail can be tilted
to a more
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horizontal attitude which results in less forward drive but more vertical lift
on the hull.
This has the effect to reducing the heeling of the craft. In a conventional
sail system, the
operator has to steer the craft more windward or let the main sai{ off and
spill wind. This
reduces the forward momentum of the craft. With my invention, the operator has
merely
to tilt the sail less, that is, bring it to a more horizontal attitude, and
the craft heel will
lessen without reducing forward momentum of the craft because the air flow
will remain
constant across the sail surface.
Referring to Figures 1, 2 and 3, the aerofoil member 26 support means 28
comprises a
vertical mast 52 having a bottom end 54 fixed to the hull 14 and top end 56
for mounting
the aerofoil member 26. There are stay members 58 and 59 fixed between the
vertical
mast 52 and the hull 14 to provide stability to the vertical mast.
The sailing craft 10 further comprises aerofoil member 26 control means 30 for
placing
the aerofoil member in a forward propulsion attitude relative to wind
direction. Control
means 30 includes means for controlling the attitude of the aerofoil member
for
optimizing aerofoil inclination and surface area to wind direction. Means for
controlling
the attitude of the aerofoil member comprises swivel and pivot means 50
connecting the
second end 56 of the vertical mast 52 to the aerofoil member 26 permitting the
aerofoil
member to adopt a plurality of desired inclination angles.
Referrmng to Figure 3a and Figure 8a, floatation material or air bags can be
incorporated
inside the aerofoil member. Figure 3a illustrates floatation blocks (41) which
may be
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made of StyrofoamTM and Figure 8a illustrates floatation bags 261 filled with
air or some
other light gas useful in this application. With floatation means, the
aerofoil will never
be completely submerged or inverted below the water craft. If the craft is
just on its side
in a capsize event, the floatation in the aerofoil will permit easy righting
of the craft.
Swivel and pivot means 60 comprises a mounting member 64 fixed to the framing
means
50 for mounting the swivel and pivot means to the aerofoil member 26.
Referring to Figures 1, 2, 3 and 4 swivel and pivot means 60 also include
damping means
66 fxed to the swivel and pivot means and disposed within the second end 56 of
the
verdcal mast 52 for damping forces induced into the swivel and pivot means by
wind.
Swivel and pivot means comprises swivel means for permitting the aerofoil
mernber to
swivel 70 around the vertical mast; and, pivot means 72 for permitting
rotation 74 of the
aerofoil member 26 about the chord line 48.
Damping means 66 comprises a first member 76 disposed within the vertical mast
52
proximate to the second end 56. There is a damping spring 78 disposed within
the
verdcal mast 52. The damping spring has arjrst end 80 and a second end 82, The
first
end of the spring 80 rests upon the first member 76. There is also a second
member 84
disposed within a third member 86. The second member 84 rests upon the second
end 82
of the damping spring 78 and is adapted to transfer forces from the swivel and
pivot
means to the damping spring. The third member 86 has a first end 88 adapted to
receive
the second end 82 of the damping spring and a second end 90 fixed to an axle
92. The
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third member is further adapted for telescopic placement within the second end
56 of the
vertical mast 52 thereby permitting reciprocating movement 85 of the third
member 86
relative to the vertical mast 52 in reaction to wind forces.
Swivel means comprises axle 92 attached by pivot means 72 to the aerofoil
member 26_
The axle 92 is fixed at its midpoint 94 to the third member 86 second end 90.
The third
member 86 is disposed telescopically within the vertical mast second end 56 so
that it is
permitted free rotation about the vertical mast.
Pivot means comprises the axle 92 mounted in a rotational relationship with a
first 96 and
second yoke 98. The first and second yokes are mounted to the mounting rnember
64
through mounting holes 101 using mounting means such as rivets or screws.
Pivot means
permits rotation of the aerofoil meniber about the chord liYie.
Referring to Figure 3, aerofoil member attitude control means comprises a
first control
line 100 having a first end 1.02 fixed to the leading edge 32 of the aerofoil
member 26 and
a second end 104 anchored to the vertical mast 52 at a point 106 proximate to
the first
end 54 thereof The first control line is tensioned to control pitch of the
aerofoil member
and bias it towards a horizontal orientation.
The control means further comprises aerofoil member tilt control means
comprising a
second control line 11U having a first end 112 fixed to the aerofoil member 26
between
the starboard side 44 and the vertical mast 52 and a second end 114 fixed to
the aerofoil
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member 26 between the port side 46 and the vertical mast 52. This creates a
second
control line port length and starboard length even though the line is a
continuous line
with no breaks. The port and starboard lengths travel down the vertical mast
52 to a set
of pulleys 120 mounted on the mast and then to a two-way winch 122 adapted to
tension
alternately the port length and the starboard length of the second continuous
control line
l 10. Tensioning either side of the control line will have the result of
tilting the aerofoil
member port or starboard as desired. The two-way winch 122 can be either hand
operated, foot operated or motor operated. The spring tension on the winch is
to keep the
tilt control line tight to help stabilize the sail and to keep the rope tight
enough to provide
friction for the rope on the winch drum.
Control means further comprises a tliird control line 124 or haul line having
a first end
126 fixed to the aerofoil member 26 between the trailing edge 34 and the
vertical mast 52
and a second end 128 fixed to port-starboard traveling means (illustrated in
Figure 6)
fixed across the stern 18 of the water craft. The traveling means is adapted
to move from
port to starboard so that the aerofoil member can be rotated about the
vertical mast and
secured in a desired position.
Referring now to Figure 5, there is shown a front view of another embodiment
of the
invention 139. The aerofoil member 140 is shown in a horizontal position such
as
depicted in Figure 2. In this position the aerofoil member is in a neutral
position or non-
propulsive pasition. However, wind across the surface of the aerofoil will
have the effect
of liffing the hull 134 of the vessel out of the water due to aerodynamic
lift. This would
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be an optimal position of the sail for motoring as water resi.stance along the
hull would be
reduced. Figure 5 illustrates the top camber 136, the leading edge 138, the
chord 143, the
starboard side 141 and the port side 142 of the aerofoil member. The span of
the aerofoil
member can be varied to suit the vessel to which it is attached. Some vessels
will have
aerofoil members with short spans and others with longer spans. In some cases
the span
will be less than the chord 143. As illustrated by arrows 146 and 148 the
aerofoil
member is adapted for tilting to either port or starboard to take advantage of
wind
direction for optimal propulsion. To tip the aerofoil member to starboard the
starboard
tilt control line 1.50 is tensioned by the two-way winch (illustrated in
Figure 1). To tip
the aerofoil member to port the port tilt line 152 is tensioned by the two-way
winch. '1'he
port and starboard tilt control lines are fed to and froin the two-way winch
by a respective
starboard 154 and port 156 pulley blocks fixed opposite each other on the mast
158. The
port and starboard tilt control lines are actually a single line have its
first 160 and second
1.62 ends respectively fixed to framing members of the aerofoi.l member. The
tilt control
lines remain parallel to the mast and are fixed to the aerofoil member about
midway
between the mast and the respective port and starboard side of the aerofoil
member.
Figure 5 illustrates a first 164 and second 166 rigid stay members fixed
between the mast
and the hull of the vessel for mast stability. F'urtrthermore, Figure 5
illustrates a port 168
and starboard 170 forward tension lines fixed between the leading edge of the
aerofoil
member and the mast to bias the aerofoil member towards a horizontal position.
Referting to Figure 6, there is shown a top view of an embodiment of the
invention 180
illustrating the top surface of the vessel hull 182 and the aerofoil member
184 in a
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perpendicular relationship to the hull. This position would optimize wind
propulsion
from a wind blowing from the stern 186 to the bow 188 of the vessel as
indicated by
arrow 190.
Referring to Figure 4 and Figure 6, arrow 192 indicates that the aerofoil
member is able
to pivot around mast 194 using the swivel and pivot means 195 to take
advantage of wind
direction. In Figure 6, the aerofoil member is tilted full to the starboard
side of the vessel
by pivot means and then swiveled so that it is perpendicular to the hull of
the vessel.
Also illustrated in Figure 6 are the port 196 and starboard 198 tilt control
lines, which in
this embodiment, travel down the mast 194 and down the centre-line of the hull
to the
two-way winch 202. In this embodiment the two-way is activated using a foot
spinner
204 so that the operator can use both hands and feet to control the vessel.
The tiller bar
206 is shown in close proxiniity to the two-way winch. The traveler 208 which
is placed
on a traveler-rod 210 across the stern 186 of the vessel is attached to the
haul line 214
first end 216 and used to pull the aerofoil member trailing edge 218 towards
the st.ern
during tacking operations. The haul line second end 218 is fixed to the
aerofoil member
about midway between the trailing edge 220 and the mast. The port 222 and
starboard
224 stays are shown fixed between the mast and the hull for mast stability.
Figure 7 illustrates one embodiment of the invention showing one advantage of
the
inventian. The aerofoil member 230 is tilted full to starboard and swiveled to
the
positic,n illustrated using the haul line 232. Note that the traveler 234 has
moved along
the traveler rod 236 ta a centre pnsition. The wind direction 239 is almost
bow-on being
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about 10 degrees to port and co-linear with the chord line 241. The aerofoil
member is
able to propel the vessel through the aerodynamics of lift since movement over
the
camber 240 of the aerofoil member will create a lift force vector 242 that can
be resolved
to a propulsion force 244.
Figure 8 illustrates another embodiment of the invention 250 in a plan-
perspective view.
The aerofoil member 252 is mounted by mast 254 to the hull 256 of the vessel
258. The
aerofoil member has a top camber 260 and maintains its shape by way of rigid
framing
members 262. The aerofoil member has a chord 263, a span 265, a leading edge
264, a
trailing edge 266, a starboard side 268 and a port side 270. A first control
line 272 first
end 274 is attached mid-way along the leading edge 264 of the aerofoil member
and the
first control line second end 276 is attached to the mast 254. The first
control line is
elastic and tensioned to bias the aerofoil member to the horizontal position.
Swivel and
pivot means 280 of the embodiment illustrated in Figure 4 are attached to
mounting
member 282 between two framing members 262. The swivel and pivot means 280 is
attached in a swiveling relationship to the top end 284 of the mast. A port
tilt control line
286 and a starboard tilt control line 288 have their respective first ends 290
and 292
attached to the aerofoil member framing members 262 mid-way between the mast
and the
port and starboard sides of the aerofoil member. The port and starboard tilt
control lines
are in fact a single line and engage a two-way winch 294 located in the stern
of the vessel
for operator tilt control. The port and starboard filt control. lines
communicate with the
two-way winch through port and starboard pulleys 296 and 298 respectively. The
two-
way winch is operable by hand or by foot using control wheel 300. The tiller
bar 302 is
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attached to the rudder 304 and is in close proximity to the control wheel 300
so that a
single operator can control and maneuver the vessel. The haul line 306 has a
first end
attached to traveler 31.0 and second end 312 attached in the rearward-middle
314 of the
aerofoil member. The traveler is adapted to move port-starboard along a
traveler rod 316.
5Port stay 318 and starboard stay 320 are illustrated fixed between the mast
and the hull
for mast stability.
Figure 9 illustrates another embodiment of the sailing system 340 comprising a
catamaran hull 342 comprising a port 344 and starboard 346 hull members fixed
together
by framing rneatis 348. Framing means is covered by a sheet 350 to support the
operator,
The aerofoil member 352 is partially illustrated to show the associated
controls. The
swivel and pivot means 354 is illustrated mounted between a first 356 and
second 358
inboard framing menibers. There would be two or more a.dditionat fi-arning
niembers (not
illustrated) depending on the size of the aerofoil member. The swivel and
pivot means
comprises a first 360 and second 362 mounting members to which are mounted a
first
364 and second 366 cambered members. Bridging the first and second cambered
members is a member 368 comprising a ball and soclCet joint where the ball
portion is
mounted to the top end of the mast and the socket is integral to the bridge
member 368.
This arrangement permits port and starboard tilting of the aerofoil member for
maximum
maneuverability and only allows a limited amount of tilting bow-ward and stern-
ward to
avoid inducing aerodynamic wind forces that might lift the vessel out of the
water. The
port tilt control line 380 and the starboard tilt control line 382 is a single
line fixed at a
first end 384 to a framing member between the mast and starboard side of the
aerofoil
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member and a fixed at a second end 386 to a framing member between the mast
and the
port side of the aerofoil member. The tilt control lines are bound at 388 to a
tilt control
rod 390 which has a first end fixed in a pivoting relationship with catamaran
framing
member 392 and a second free end that is engaged with a serra.ted catamaran
framing
member 396. The control rod 390 is illustrated engaged with a central
serration 398 on
member 396 to maintain the aerofoil member horizontal. To induce a port-side
tilt to the
aerofoil member the operator disengages the rod 390 from the middle serration
and
moves the rod to starboard to engage another of the serrations. A similar
operation is
used to induce a starboard tilt by moving the control rod to the port and
engaging another
serration. The tilt control line communicates with the control rod through a
first set of
pulleys 400 and 402 mounted at the base of the mast and a second set of
pulleys 404 and
406 mounted at each of the stern corners 408 and 410 of the catamaran frame. A
forward
tensioning control line 412 is mounted between the centre leading edge 414 of
the
aerofoil member and the mast to bias the aerofoil to the horizontal position..
The haul line
416 is illustrated as engaging pulley 418 fixed to the trailing edge 420 of
the aerofoil
member and having a first end fixed to traveler 422 on traveler rod 424 for
port-starboard
motion. The second end 426 of the haul line is free for control by the
operator so that
pulling on the second end will pull the aerofoil trailing edge toward the
centerline of the
vessel. A port 428 and starboard 430 stays are illustrated fixed between the
mast and the
catamaran frame. The tiller arm 432 is illustrated in mechanical communication
with the
port 434 and starboard 436 rudders.
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Figure 10 illustrates another embodiment of the invention 450 wherein the
vessel 452 is a
large cargo vessel displacing thousands of tons. The sail system 454 can be a
double
aerofoil 456 and 458 as illustrated or the sail system can be a plurality of
aerofoils. The
sail system on the larger vessels is the same as on the smaller vessels. Each
aerofoil is
supported by a mast 460 and 462 and each mast is stabilized by at least one
stay 464 and
466. The control lines some of which are visible in this figure would be
configured
substantially the same as in the smaller vessels with port and starboard tilt
control lines
(468 to 474) and haul lines (476 and 478) linked to a winch mechanism (not
shown) so
that the aerofoils could be controlled in unison. Computer means (not shown)
including
wind sensing means can be installed to control the sails in order to optimize
wind
propulsion and save fuel.
This description contains niuch specificity that should not be constiued as
liinitiiig the
scope of the invention but merely provides illustrations of some of its
embodiments.
Thus the scope of the invention should be determined by the appended claims
and their
legal equivalents rather than by the examples given.
19
