Lift creating sail and sail system

An improved lift creating sail and sail system where a substantially rectangular mainsail made up of a plurality of panels forms an aerodynamically efficient airfoil that is supported at approximately its center on a pivot so that it has three degrees of freedom. The mainsail can be tilted athartships, rotated along a yaw axis, and tilted fore and aft to create lift and minimum drag. An optional jib sail that tracks the motion of the mainsail also produces lift. The mainsail and jib sail can be trimmed and positioned along three degrees of freedom to obtain maximum lift and minimum drag as well as a stable system. The effect of this sail system is to increase the speed of the boat by 15-25%.

FIELD OF THE INVENTION 
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%. 
DESCRIPTION OF RELATED 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 coat'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 reduction 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 helm" is actually caused by a resultant 
force moment created by the center of pressure in the sail being windward 
of the centerline of the boat. In order to counter "lee helm" some prior 
art systems tilt the sail aft as well as athwartship to achieve a 
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 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 
produce lift. 
What is badly needed is a lift producing sail and sail system that uses an 
optimally shaped sail that is not attached to the mast at its foot. This 
sail should be attached to the boat in a way that it can be tilted along 
three axes and thus create optimum lift and thrust for any heading with 
respect to the wind. In addition, an optional jib sail should work in 
harmony with the mainsail leading to additional lift. Finally, there 
should be a way to control the size or amount of sail exposed to the wind 
so that an optimum sail can be fashioned for any wind speed. 
SUMMARY OF THE INVENTION 
The present invention relates to an improved lift creating sail and sail 
system. It may contain a mainsail and a jib sail. Both sails can be tilted 
to produce lift. The mainsail is an aerodynamically 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); 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 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 
athartships to any angle. The mainsail can be mounted so that its 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 can also have a jib sail that also tilts into the wind 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 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.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows an embodiment of the present invention in perspective view on 
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 FIG. 1, 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 without deviating from the scope of the present 
invention. The jib sail 3 is substantially triangular in this embodiment, 
and can be mounted forward of the mainsail 2. The jib sail can have any 
other convenient shape without deviating from the scope of the present 
invention. 
The mainsail 2 shown in FIG. 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 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 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 hull(s) 1. The 
entire weight of the mainsail 2 can rest on this pivot 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 normally located below the pivot 8 at 
the level of the top of the hull(s) 1. This track is generally not 
attached to the base of the mainsail. In fact, the base of the mainsail 2 
can move substantially away from this 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 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 the jib sail moves in the same direction as the fore foot 
of the mainsail. The means of coupling the motion of the two sails in this 
embodiment of the present invention can be through cross-rigged lines 
between the mainsail track or traveler 6 and fore foot of the jib sail on 
its track 7. 
FIG. 2 shows a top view and a front view of the embodiment of the present 
invention of FIG. 1. In FIG. 2, the hull 1, mainsail 2, jib sail 3 and the 
jib sail track 7 can be clearly seen. The position of the mainsail track 6 
is also shown for clarity. In FIG. 2, the athartship tilt of the mainsail 
2 can also be clearly seen. 
FIG. 3 shows a slightly different embodiment of the mainsail from that 
shown in FIG. 1. In this embodiment, the mainsail is made up from a 
plurality of panels 4 of sail material on a frame made up of longitudinal 
spars 5. The horizontal truss 9 can be seen attached to a cross truss 11 
at the center of the mainsail. Either a truss or a cross spar can be used; 
however, a truss has been found to be stronger. 
FIG. 4 is a side and top view of the mainsail of FIG. 3. Here the structure 
of the optional truss 11 can be more clearly seen. Also in FIG. 4, two 
leading edge 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 sail towards the cross spar. 
This allows the use of pliable battens rather than reinforced seams. 
FIG. 5 shows an embodiment of the leading edge foil that would vary the 
sail area by sliding the sail towards the cross spar. In FIG. 5, the 
vertical spars 5 are seen with the sail 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 FIG. 5. Between the 
fore and aft panels of the mainsail is an air slot 13. 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 tremendously reduced. 
FIG. 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 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). 
FIG. 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 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. 
Sailing a boat using the present invention consists of adjusting the yaw of 
the mainsail and jib sail, and then adjusting 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 traveler 
and fixed with lines an cleats. The top of the mainsail can 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 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 loosen the line affecting sail trim (spill the wind), or turn the boat 
into the wind (luff the sails). 
It is to be understood that the above-described arrangements are merely 
illustrative of the application of the principles of the invention, and 
that other arrangements may be devised by those skilled in the art without 
departing from the spirit and scope of the invention.