U.S. patent number 3,763,703 [Application Number 05/233,608] was granted by the patent office on 1973-10-09 for apparatus for trimming sails.
Invention is credited to Jerome V. Man.
United States Patent |
3,763,703 |
Man |
October 9, 1973 |
APPARATUS FOR TRIMMING SAILS
Abstract
A pressure-sensitive device is provided for aiding a sail-boat
skipper in trimming a sail for maximum efficiency and speed. The
device includes air-pressure sensors located on opposite sides of
the sail and means for comparing the pressures so that the sail may
be trimmed to provide a maximum pressure differential. In one
embodiment the sensors are a pair of static tubes, each having one
end operatively associated with one side of the sail and the other
end in communication with a housing having a flexible diaphragm
which moves in response to change in the difference in air pressure
on opposite sides of the sail. The diaphragm is coupled to a
dial-type indicator for indicating these changes.
Inventors: |
Man; Jerome V. (Highland Park,
IL) |
Family
ID: |
22877958 |
Appl.
No.: |
05/233,608 |
Filed: |
March 10, 1972 |
Current U.S.
Class: |
73/182;
114/102.16; 114/144R; 114/144A; 73/170.03 |
Current CPC
Class: |
B63H
9/067 (20200201); B63H 9/10 (20130101); G01P
5/14 (20130101); B63B 49/00 (20130101) |
Current International
Class: |
B63H
9/10 (20060101); B63H 9/00 (20060101); G01c
021/00 () |
Field of
Search: |
;73/47R,212,182,188,180,189 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Queisser; Richard C.
Assistant Examiner: Yasich; Daniel M.
Claims
What is claimed and desired to be secured by Letters Patent of the
United States is:
1. In combination with the main sail of a sail-boat the improvement
which comprises a first static port means positioned on one face of
the sail at substantially the center of pressure thereof, a second
static port means positioned on the other opposite face of the
sail, the said port means being substantially opposite one another
to sense the respective static air pressures existing on both sides
of the center of pressure, a device for translating the respective
pressures into intelligence representing the respective air
pressures, differential means responsive to said difference in air
pressures and presenting the same as a measure of the trim of the
sail and means providing communication between said port means and
differential means.
2. The combination in accordance with claim 1 wherein the port
means open downwardly to preclude entry of water.
Description
BACKGROUND OF THE INVENTION
This invention relates to a device for aiding a sailboat skipper in
trimming his sails for maximum speed and efficiency. A laminar flow
of air over the sail's curved surface creates a negative pressure
on the forward or leeward side of the sail, producing a suction
effect which the boat's hull in turn transforms into forward
motion.
Proper trim of the main sail and other sails produces maximum
efficiency and speed. Oftentimes the skill of a skipper is measured
by his ability to maintain the sails trimmed so as to produce
maximum speed. The skipper trims a sail by letting the sail out
until it luffs and then bringing the sail back until the luff is
cancelled. Luffing, efficiency and speed are related to the air
foil effect achieved by the shape of the sail which is, in turn,
related to the air pressures on opposite sides of the sail.
Indicators are presently available for measuring boat speed
relative to the water so that the sails can be trimmed to achieve
maximum indicated speed; see U.S. Pat. No. 3,349,615. Indicators
are also available for measuring the strain of the mast which is
caused by the sail driving forces. By trimming the sail the driving
force can be maximized as determined by maximizing the strain on
the mast. Devices for measuring the mast strain are disclosed in
U.S. Pat. No. 3,157,148.
None of these prior art devices measure or compare the air pressure
on opposite sides of a sail which pressure determines the shape of
the sail and its orientation, and thus its efficiency and the speed
of the boat. Maximum efficiency and speed are achieved by
maximizing the difference in pressure on opposite sides of a sail
for any given heading.
Therefore, it is an object of this invention to provide means for
sensing the air pressures on opposite sides of a sail.
It is another object to provide means associated with the air
pressure sensors for indicating the difference in air pressure on
opposite sides of a sail.
It is a further object to provide means for indicating when the
sails have been trimmed to produce a maximum difference in the air
pressures.
These and other objects of this invention will be apparent from the
following description and appended claims.
SUMMARY OF THE INVENTION
By virtue of this invention there is provided means for measuring
the air pressures on opposite sides of a sail and comparing and
displaying these pressures. In one embodiment static tubes sense
the air pressures on opposite sides of a sail and an aneroid
barometer may be provided for measuring the respective pressures.
In another embodiment, comparator means are provided for comparing
the pressures on opposite sides of the sail and displaying the
differential so that a ready determination may be made of the
maximum difference.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is an elevational view of a sailboat having a main sail and
showing the location of one sensor forward of the sail;
FIG. 2 is a top plan view showing the location of the sensors on
opposite sides of the sail;
FIG. 3 is a diagrammatic view showing a pair of aneroid-type
barometers, each adapted to be coupled to one sensor;
FIG. 4 is a diagrammatic sectional view of an apparatus adapted to
be coupled to both sensors to display pressure differences;
FIG. 5 is a diagrammatic sectional view showing another apparatus
for displaying pressure differences in which the pressure
differential causes the movement of a flexible diaphragm which is
coupled to an electrical-type indicator; and
FIG. 6 is a sectional view taken along line 6--6 of FIG. 1 showing
the sensors positioned on opposite sides of the sail.
BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawing, the sailboat 10 includes a hull 12,
mast 14 and sail 16 with the wind direction as shown by arrow
18.
The air pressure sensors 20 and 22 are mounted to the sail in
positions for sensing the pressure on opposite sides of the sail at
approximately th center of pressure thereof. With the sail in the
position as shown in FIG. 2, the sensor 20 senses the air pressure
on the forward or leeward side of the sail while the sensor 22
senses the air pressure on the rearward or aft side of the sail.
The sensors 20 and 22 are substantially identical hollow tubes,
viz. static tubes having open sensing ends 24 and 25, respectively,
which are bent downwardly so as to prevent the inflow of water. The
sensing ends are positioned so as to open generally downstream with
respect to the air flow over the sail and thereby substantially
eliminate momentary fluctuations in pressure. The other end of each
sensor extends downwardly from its position on the sail and
terminates at a point near the hull 12, where it is connected to
instruments as described hereinafter. The connection between the
sensors and instruments may be flexible to accommodate movement of
the sail, such as reefing, raising and lowering.
In a first embodiment, a pair of dial indicator aneroid barometers
26 and 28 are provided, each of which is connected to one of the
sensors. For example, the barometer 26 is connected to the forward
sensor 20 via tube 26a to measure the air pressure sensed thereby,
while the barometer 28 is connected to the aft sensor 22 via tube
28a for measuring the air pressure sensed by it. The skipper, after
determining his heading, trims the sail by adjusting it so that the
readings on the barometers 26 and 28 provide a maximum difference.
This maximum difference indicates that the difference in air
pressure on opposite sides of the sail has been maximized so that
maximum efficiency and speed have been obtained.
In an alternative embodiment, in order to provide a single
instrument for the skipper to read, rather than two separate
barometers, the forward sensor 20 is connected to an expansible
air-tight bellows 30 via tube 30a. The bellows 30 is enclosed
within and supported by an air-tight housing or pressure chamber 32
which communicates with the aft sensor 22 via tube 32a. Through a
series of linkages and gears, as are well known in the art and
indicated by line 34, the expansion or contraction of the bellows
30 is indicated by a mechanical pointer 36. The indicator is
calibrated so that the center of the scale 38 represents zero
pressure differential and the maximum pressure differentials,
positive or negative, are indicated by opposite ends of the scale.
When the pressure on both sides of the sail is the same, the
bellows 30 is in an initial position and the indicator 36 points
toward the zero setting. If, as in FIG. 2 the sensor 20 senses a
low pressure and the sensor 22 senses a higher pressure, the
bellows contracts. If the pressure conditions are reversed so that
the sensor 20 senses a high pressure and the sensor 22 a low
pressure, the bellows 30 will expand. Thus the indication provided
by the pointer 36 represents the difference in pressure sensed at
the sensors 20 and 22. Therefore, the skipper need only adjust his
sail until he achieves the maximum difference which is indicated by
the greatest swing of the pointer 36 to either side of the scale 38
from the center.
In yet another embodiment, the sensors 20 and 22 are connected to
an air-tight housing 39 or enclosure which includes a flexible
dividing wall or diaphragm 40 that divides the housing into a pair
of air-tight chambers 42 and 44. The chamber 42 is connected to the
sensor 20 via tube 42a and the chamber 44 is connected to the
sensor 22 via tube 44a. The pressures within the chambers 42 and 44
are related to the pressures sensed by the sensors 20 and 22 and if
the pressures are approximately equal, the flexible dividing wall
or diaphragm 40 assumes a center position. However, if the
pressures change so that the pressure in chamber 42 is greater than
that in chamber 44, the diaphragm will move toward chamber 44,
while if the pressures are reversed, the diaphragm 40 would move
toward and into the chamber 42. Thus the movement of the diaphragm
40 is related to the differences in pressures in the chambers and
thus the difference in pressures is sensed by the sensors 20 and
22.
Mechanical display means similar to that shown in FIG. 4 can be
connected to the diaphragm so as to display the difference in
pressures. Electrical means 46, generally, can also be used. The
means 46 include a pair of piezoelectric crystals 48 and 50 which
respond electrically to variations in the respective varying forces
applied thereto and are positioned on opposite sides of the
diaphragm 40 and in contact therewith. The crystals are
electrically connected to a translator 52, as is well known in the
art, and the translator's output then becomes the input to display
means 54 which can include pointer 54a and scale 54b. Movement of
the diaphragm 40 which is related to variations in the pressure
conditions at the sail, causes variations in the forces applied to
each of the crystals 48 and 50. This variation in forces is sensed
by the translator 52. The skipper, as before, trims his sails to
obtain a maximum difference as shown by the display 54.
It will be appreciated that numerous changes and modifications can
be made to the embodiments shown herein without departing from the
spirit and scope of this invention.
* * * * *