Note: Descriptions are shown in the official language in which they were submitted.
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Description
LIFT CREATING SAIL AND SAIL SYSTEM
Technical Field
This invention relates generally to the field of sails and
sail boats and more particularly to a mainsail that can create
lift and a sail system of a mainsail and a jib sail that together
create lift and increase the speed of a sailboat by 15-25~.
Background Art
A sailboat is propelled by wind impinging on a sail to
create thrust (a forward force vector). A typical sail however,
also creates drag (an aftward force vector) tending to cancel
thrust. In addition, the boat's hull creates considerable drag
as it passes through the water. The magnitude of the total drag
force is proportional to boat's velocity and is related to the
amount of the hull under water, the exact shape of the hull, the
size and shape of the sail, and other factors. If a sail system
can create lift (an upward force vector) as well as thrust and
drag, the hull is pulled more out of the water (called a reduc-
tion in heeling). This effect can considerably reduce drag
caused by the hull. Since hull drag is the major component of
drag, the speed of the boat can be substantially increased.
Also, if airflow over the sail can be optimized, sail drag is
decreased as well resulting in further increases in speed.
Prior art systems for achieving lift on a sailboat have
operated off of a single mainsail attached to a mast that could
be tilted such that the top of the sail moved windward of the
centerline of the boat. The idea was to incline a conventional
sail athwartship so that the top of the sail moves into the wind
producing lift as well as thrust. However, simply tilting the
sail causes an undesirable side effect called "lee helm." This
is a tendency for the boat to try to turn away from the wind
requiring the continuous use of rudder to maintain a heading.
This use of rudder causes extra drag slowing the boat. "Lee
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helm" is actually caused by a resultant force moment created by
the center of pressure in the sail being windward of the center-
line of the boat. In order to counter "lee helm" some prior art
systems tilt the sail aft as well as athwartship to achieve a
35 canceling moment.
Prior art systems all attach the base of the mast to either
a flexible joint on the centerline or to a straight or curved
track running athartship. This has the disadvantage of not being
able to position the sail at an optimum angle with respect to the
40 wind for maximum lift and minimum drag. Prior art systems also
use conventional triangular sails which are also not optimum for
producing maximum lift. Finally, no attempt has been made in
prior art systems to make use of a jib sail that works in harmony
with the mainsail and moves optimally with the mainsail to also
45 produce lift.
Disclosure of the Invention
The invention relates to an improved lift creating sail and
sail system. It contains a mainsail and a jib sail. Both sails
can be tilted to produce lift. The mainsail is an aerodynamical-
50 ly efficient airfoil that can be made from a set of panels. The
mainsail is normally mounted on a pivot that can be located near
the its center. The pivot is normally attached to an A-frame in
such a way that it can move about three degrees of freedom. This
way the mainsail can be tilted athartships (port and starboard);
55 it can be rotated along the yaw axis; and it can be tilted fore
and aft. The mainsail can be of generally rectangular shape, or
any other convenient shape, and can be furled by either rolling
it up or gathering it in. The various. axes of tilt and rotation
are totally general whereby the sail can be tilted or yawed to
60 any angle or orientation with respect to the boat and the wind.
In this manner, the generally rectangular sail can be used so
that its length is generally up and down or it can be tilted so
that its length is substantially horizontal as a square sail. It
can, at the same time, be yawed to any angle and tilted athart-
65 ships to any angle. The mainsail can be mounted so that its
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weight rests on the pivot and A-frame from its center. There is
generally no mast and no weight supported by the base of the
mainsail.
The system also has a jib sail that also tilts into the wind
70 to generate additional lift and to compensate for any lee helm
effect. This jib can track the athartship tilt of the mainsail,
or it can be positioned at a different angle for optimum trim and
efficiency. The total flexibility of tilt angles for both the
mainsail and the job, coupled with the use of a lift creating jib
75 and the ability to furl, yields a sail system that creates
optimum lift (leading to minimum total drag on the boat) for any
wind direction, velocity, or condition.
Brief Description of the Drawinas
Figure 1 shows a perspective view of a type of sailboat
80 equipped with an embodiment of the present invention.
Figure 2 shows a top view and a front view of at type of
sailboat equipped with an embodiment of the present inven-
tion.
Figure 3 shows a perspective view of an embodiment of a
85 mainsail.
Figure 4 shows a side view and a top view of an embodiment of
a mainsail.
Figure 5 shows an embodiment of the mainsail panels creating
an air slot.
90 Figure 6 shows how the present invention is operated in reach
or tack (wind athartships or forward).
Figure 7 shows how the present invention is operated in run
(wind aft).
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Figure 8 shows an optional coupling of the mainsail and jib
95 sail.
Hest Mode of Carrvinc Out the Invention
Figures 1 shows a perspective view of a type of sailboat
with two hulls. The invention is equally suited for use on a
monohull boat or any other combination of hulls. In Figure 1,
100 each of the hulls (1) is elongated with a major axis defining a
fore and aft direction along the boat. The mainsail (2) in this
embodiment is substantially rectangular; however, the mainsail
can have any other convenient shape. The jib sail (3) is sub-
stantially triangular in this embodiment, and can be mounted
105 forward of the mainsail (2). The jib sail can have any other
convenient shape.
The mainsail (2) shown in figure 1 can be made of several
panels (4) of sail material, or it can be a continuous sail. The
panels (4) are held together using spars (5) or trusses, or any
110 other construction means to form a semi-rigid frame.
The mainsail (2) is normally mounted at a pivot (8) that
allows it three degrees of freedom. This means that the mainsail
(2) can be tilted athartships and fore and aft, and it can be
yawed to any angle with respect to the centerline of the boat. A
115 truss or cross spar (9) can be located at the center of the
mainsail (2), and one end of this truss (9) is normally attached
to the pivot point ()8. The pivot (8) is firmly attached to an
A-frame (10) that is normally rigidly attached to the hulls)
(1). The entire weight of the mainsail (2) can rest on this pivot
120 (8). The base of the mainsail is not normally attached to the
hull. The A-frame (10) thus supports the mainsail (2).
An optional track or traveler (6) is located below the pivot
(8) at the level of the top of the hulls) (1). This track is
generally not attached to the base of the mainsail. In fact, the
125 base of the mainsail (2) can move substantially away from this
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track (6) when the mainsail is tilted fore and aft. The optional
track (6) allows the tilt motion or position of the mainsail (2)
to be cross coupled to the jib sail (3). The forward foot of the
jib sail (3) can be attached to a second track (7) that is also
130 part of the cross coupling of motion from the mainsail to the jib
sail. The actual cross coupling of position can be accomplished
with lines or any other means that will couple motion from one of
the sails to the other. The top or head of the jib sail is
normally attached to the pivot point (8). Thus, the fore foot of
135 the jib sail moves in the same direction as the fore foot of the
mainsail. The optional method of coupling the motion of the two
sails in this embodiment can be through cross-rigged lines
between the mainsail track or traveler {6) and fore foot of the
jib sail on its track (7).
140 Figure 2A shows a top view and Figure 2B shows a front view
of the invention of figure 1. In figures 2A and 2B, the hull (1),
mainsail (2), jib sail (3) and the jib sail track (7) can be
seen. The position of the mainsail track (6) is also shown. In
Figures 2A and 2B, the athartship tilt of the mainsail (2) can
145 also be seen.
Figure 3 shows that the mainsail can be made up from a
plurality of panels {4) of sail material on a frame made of
longitudinal spars (5). The horizontal truss (9) can be seen
attached to a cross truss (11) at the center of the mainsail.
150 Either a truss or a cross spar can be used; however, a truss has
been found to be stronger.
Figure 4A is a side view and Figure 4B is a top view of the
mainsail of figure 3. Here the structure of the truss (11) can be
more clearly seen. Also in figures 4A and 4B, two leading edge
155 foils (12) can be seen. These allow the individual panels of the
mainsail to rotate about the longitudinal spar. The sail area
can be varied by furling in and out the sail which can be rolled
around the longitudinal spar. In an alternate embodiment of the
present invention, the sail area can be varied by sliding the
160 sail towards the cross spar. This allows the use of pliable
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battens rather than reinforced seams.
Figure 5 shows an embodiment of the leading edge foil that
would vary the sail area by sliding the sail towards the cross
spar. In figure 5, the vertical spars (5) are seen with the sail
165 panels attached through leading edge foils (12). The leading
edge foils (12) freely rotate about the spars (5) allowing the
panel (4) to take various positions with respect to the wind. An
alternate position is shown by a broken line (14) in figure 5.
Between the fore and aft panels of the mainsail is an air slot
170 (I3). This optional feature allows a tremendous increase in the
efficiency of the mainsail by acting as a boundary layer control
device such as might be found on the wing of a high performance
aircraft. By keeping the boundary layer of the airflow close to
the surface of the panel, drag caused by the sail itself is
175 tremendously reduced.
Figure 6 shows a possible orientation of the mainsail and
jib sail in run (run is a situation where the wind is aft of the
boat). The mainsail can be tilted along three degrees of freedom
to achieve maximum lift and thrust. The forefoot of the jib sail
180 tracks the athartship tilt of the mainsail, and can be trimmed
for the exact heading with respect to the wind and wind and sea
conditions. Of course, the system will be adjusted to different
angles and trim depending on the exact wind direction (directly
astern as opposed to an angle off the beam).
185 Figure 7 shows a possible orientation of the mainsail and
jib sail in reach or tack (reach is when the wind is athartships,
while tack is when the wind is at an angle off the bow - tacking
is the art of taking a sailboat into the wind by alternately
changing heading with respect to the wind from port bow to
190 starboard bow, etc.). Again, the system will be adjusted to
different angles depending on the exact wind direction and on
conditions. The angle will be changed on each tack if an attempt
is being made to keep an average heading into the wind.
Figure 8A and 8B show how the jib is optionally made to
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195 track the athwartship motion of the mainsail. Under the mainsail
is a curved rocker shaped track (6) running athwartship at
approximately halfway fore and aft. On this track (6) is a
carriage (17) that slides alone it. This carriage (17) is
attached through lines to the mainsail (2) at the front spar.
200 These lines are attached to the top and bottom of the mainsail
(2). On the bow is another curved track (7); however this track
(7~ points forward rather than down. On this track is another
carriage (16) that is directly attached to the front of the jib.
The two carriages (16), (17) are coupled by a rigged line (15)
205 that is crossed between a set of forward pulleys (18) and aft
pulleys (19). These pulleys (18), (19) are directly attached to
the hulls (1) adjacent to the forward and aft tracks (7), (6).
In this manner, the mainsail can be coupled to the jib sail in
terms of athwartship motion. When properly rigged, the bottom of
210 the mainsail follows the front or forefoot of the jib. If the
jib moves right or starboard, so does the bottom of the mainsail.
It is important to note that the bottom of the mainsail (2) is
not tightly connected to the carriage (17) on the amidships track
(6), but rather is loosely connected through a series of lines.
215 This allows the mainsail (2) to freely tilt fore and aft and
still maintain the athwartship coupling to the jib. A line on
the aft of the mainsail is used to trim it.
Sailing a boat using the present invention consists of
adjusting the yaw of the mainsail and jib sail, and then adjust
220 ing the amount of sail trim in each sail. The degree of yaw of
the mainsail (which can control the amount of yaw of the jib
sail) can be controlled by adjusting the position of the forefoot
of the mainsail. This can be connected to its track by a travel-
er and fixed with lines an cleats. The top of the mainsail can
225 be simultaneously braced by adjusting lines attached to the head
of the longitudinal spar. Sail trim of the mainsail can be
adjusted by lines attached to the aft of the mainsail at the
center, and bottom cross spars and secured by cleats. Sail trim
of the jib can be adjusted by lines attached to the aft foot of
230 the jib and fastened to the traveler at the fore foot of the
mainsail. To reduce the amount of wind in each sail, one can
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loosen the line affecting sail trim (spill the wind), or turn the
boat into the wind fluff the sails).
Industrial Applicability
235 The present invention is very useful in the sailboat indus-
try. It is a novel way of increasing the speed of a sailboat by
15-25 percent by causing the mainsail and jib sail to product
lift. This allows boats to race or to sail normally much faster
than would otherwise be possible. There is a tremendous demand
240 worldwide for faster, more efficient, sailboats.
