U.S. patent application number 17/405971 was filed with the patent office on 2022-02-24 for mast fairing for a sailboat.
The applicant listed for this patent is Donald Butler Curchod. Invention is credited to Donald Butler Curchod.
Application Number | 20220055725 17/405971 |
Document ID | / |
Family ID | |
Filed Date | 2022-02-24 |
United States Patent
Application |
20220055725 |
Kind Code |
A1 |
Curchod; Donald Butler |
February 24, 2022 |
MAST FAIRING FOR A SAILBOAT
Abstract
A mast fairing for a sailboat includes an upper fairing and an
optional lower fairing configured to reduce turbulent airflow over
the upwind and downwind sides of a sail. The upper fairing includes
a fairing wrap includes a central segment configured to wrap around
a mast, a left-side panel, a right-side panel, and a sail track
attached to trailing edges of the left- and right-side panels. One
or more fairing supports are optionally attached to the sail track
between the left- and right-side panels of the fairing wrap. The
optional lower fairing includes a central segment, a left-side
panel, and a right-side panel configured for installation on a mast
and boom below the upper fairing. The upper and lower fairings
reduce turbulent airflow over the surfaces of a sail and increase
regions of laminar airflow to improve the performance of the
sail.
Inventors: |
Curchod; Donald Butler;
(Avalon Beach, AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Curchod; Donald Butler |
Avalon Beach |
|
AU |
|
|
Appl. No.: |
17/405971 |
Filed: |
August 18, 2021 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
63067310 |
Aug 18, 2020 |
|
|
|
International
Class: |
B63H 9/067 20060101
B63H009/067 |
Claims
1. An apparatus, comprising: an upper fairing, comprising: a
fairing wrap, comprising: a central segment sufficiently pliable to
conform to a curved surface of a sailboat mast; a left-side panel
joined to said central segment, said left-side panel comprising a
left-side trailing edge; a right-side panel joined to said central
segment opposite said left-side panel, said right-side panel
comprising a right-side trailing edge; and a sail track positioned
between said left-side trailing edge and said right-side trailing
edge, said sail track configured for coupling to a sail luff; and a
lower fairing, comprising: a lower fairing central segment
sufficiently pliable to conform to the curved surface of the
sailboat mast; a left-side lower fairing panel joined to said lower
fairing central segment; and a right-side lower-fairing panel
joined to said lower fairing central segment opposite said
left-side lower fairing panel.
2. The apparatus of claim 1, wherein said left-side panel is
integrally formed with said central segment, and said left-side
panel is formed with a slot positioned to receive a mast
spreader.
3. The apparatus of claim 1, wherein said right-side panel is
integrally formed with said central segment, and said right-side
panel is formed with a slot positioned to receive a mast
spreader.
4. The apparatus of claim 1, wherein said upper fairing is formed
with an overall length dimension corresponding to at least 70
percent of a separation distance from a gooseneck for a boom to a
top end of the sailboat mast.
5. The apparatus of claim 1, further comprising a fairing support
attached to said sail track.
6. The apparatus of claim 5, wherein said fairing support is
positioned between said sail track and said central segment of said
fairing wrap.
7. The apparatus of claim 5, further comprising an additional
plurality of said fairing support attached to said sail track.
8. The apparatus of claim 5, wherein said fairing support
comprises: a front wall; a first side plate coupled to a left side
of said front wall; and a second side plated coupled to a right
side of said front wall opposite said first side plate, wherein
said left-side trailing edge attaches to said first side plate and
said right-side trailing edge attaches to said second side
plate.
9. The apparatus of claim 8, wherein said front wall is formed with
a radius of curvature greater than or equal to a radius of
curvature of the curved surface of the sailboat mast.
10. The apparatus of claim 1, wherein said left-side lower fairing
panel comprises a length dimension corresponding to a separation
distance from a front side of the sailboat mast to a clew of a sail
coupled to the sailboat mast.
11. The apparatus of claim 10, wherein said right-side lower
fairing panel comprises said length dimension of said left-side
lower fairing panel.
12. The apparatus of claim 1, wherein said left-side lower fairing
panel and said right-side lower fairing panel are integrally formed
with said lower fairing central segment.
13. The apparatus of claim 1, further comprising a control line and
an outhaul block, said control line passing through a tack of said
lower fairing and through said control block, with said control
block configured to be suspended from a sail outhaul line.
14. A fairing configured for sliding contact with a sailboat mast,
said fairing comprising: a fairing wrap, comprising: a central
segment sufficiently pliable to conform to a curved surface of a
sailboat mast; a left-side panel joined to said central segment,
said left-side panel comprising a left-side trailing edge; a
right-side panel joined to said central segment opposite said
left-side panel, said right-side panel comprising a right-side
trailing edge; and a fairing support positioned between said
central segment, said left-side trailing edge, and said right-side
trailing edge, said fairing support comprising: a front wall; a
first side plate coupled to a left side of said front wall; and a
second side plated coupled to a right side of said front wall
opposite said first side plate; and a sail track attached to said
fairing support.
15. The fairing of claim 14, wherein said sail track is attached to
said first side plate of said fairing support.
16. The fairing of claim 14, wherein said sail track is attached to
said front wall of said fairing support.
17. The fairing of claim 16 wherein said fairing support is a first
fairing support, and further comprising: a second of said fairing
support positioned between said central segment, said left-side
trailing edge, and said right-side trailing edge; a first fairing
plate attached to said first side plate of said fairing support and
said first side plate of said second fairing support; and a second
fairing plate attached to said second side plate of said fairing
support and said second side plate of said second fairing
support.
18. The fairing of claim 17, further comprising a roller furler
attached to said faring support.
19. The fairing of claim 14, wherein said sail track is configured
to carry a plurality of sail cars configured to be coupled to a
sail luff.
20. The fairing of claim 14, wherein said sail track is configured
to receive a bolt rope on a sail luff.
Description
FIELD OF THE INVENTION
[0001] Embodiments are related generally to equipment for improving
aerodynamic lift generated by wind flowing over a sailboat sail and
more particularly to equipment for increasing a size of a region of
laminar air flow and reducing a size of a region of turbulent air
flow over sailboat sails.
BACKGROUND
[0002] A sailboat sail made from a pliable material such as
sailcloth, thin polymer sheet, and/or composite materials assumes a
curved surface shape under the influence of wind striking the sail.
Air flowing in smooth layers over the upwind and downwind sides of
the curved sail generates aerodynamic lift, a force which may be
used to propel a sailboat in a forward direction of travel. As wind
velocity increases, aerodynamic lift increases until airflow over
the curved sail transitions from smooth flow with air molecules
moving parallel to sail surfaces, also referred to as laminar flow,
to turbulent flow, a chaotic flow condition with air molecules
moving in many directions. Turbulent airflow at or near the
surfaces of the sail reduces the component of aerodynamic lift
available to propel the sailboat forward and increases mechanical
stresses acting on the mast, rigging, and sails.
[0003] Laminar and turbulent flow may be detected by placing
telltales at different locations on a sail, by making air pressure
measurements at different locations on a sail, by making air
velocity measurements at different locations on a sail, and by
other means. Such measurements show that turbulent flow and laminar
flow are influenced by wind velocity, the radius of curvature of
the sail (the "flatness" of the sail), the location of the deepest
part of the curvature relative to the leading edge of the sail, by
obstructions to airflow near the sail, and by other factors.
[0004] The mast and other parts of the rigging used to hold up a
sail and control the shape of the sail contribute to turbulent flow
over the sail. A widely-used sailing rig couples the leading edge
of a sail (the "luff") to the aft side of a mast. The bottom edge
of the sail (the "foot") is held along one or more spars (on some
boats, the "boom") extending aft from the mast. A hinge structure
(on some boats, the "gooseneck") rotatably couples the boom to the
mast, although other arrangements are known. When a boat sails
upwind, that is, with the apparent wind at an angle less than
ninety degrees to the boat's direction of travel, air flowing
around the mast creates a turbulent flow region along the luff of
the sail. The turbulent flow region may be largest on the downwind
side of the sail, sometimes extending from the luff to about
one-fifth to one-third of the sail's chord length.
[0005] Laminar flow capable of generating aerodynamic lift for
propelling the sailboat is limited to the part of the sail between
the turbulent flow region and the trailing edge of the sail (the
"leach"). Air flowing downward from the foot of the sail toward the
boat hull, rather than along the full chord length of the sail,
further reduces aerodynamic lift for propelling the sailboat.
SUMMARY
[0006] An example apparatus embodiment of a mast fairing includes
an upper fairing and a lower fairing. The upper fairing includes a
fairing wrap. An example fairing wrap includes a central segment
sufficiently pliable to conform to a curved surface of a sailboat
mast; a left-side panel joined to the central segment, with the
left-side panel including a left-side trailing edge; a right-side
panel joined to the central segment opposite the left-side panel,
with the right-side panel including a right-side trailing edge; and
a sail track positioned between the left-side trailing edge and
right-side trailing edge. The sail track is configured for coupling
to a sail luff. The lower fairing includes a lower fairing central
segment sufficiently pliable to conform to the curved surface of
the sailboat mast; a left-side lower fairing panel joined to the
lower fairing central segment; and a right-side lower-fairing panel
joined to the lower fairing central segment opposite the left-side
lower fairing panel.
[0007] The left-side panel and/or the right-side panel of the upper
fairing may optionally be formed separately from the central
segment and attached strongly to the central segment, or may
optionally be integrally formed with the central segment. The
left-side panel and the right-side panel may each be optionally be
formed with a slot positioned to receive a mast spreader. A slot
may optionally extend onto the central segment of the upper
fairing. Additional slots may optionally be provided to enable the
upper fairing to move past other mast attachments such as an
attachment point for a forestay, brackets for lights or antennas,
and the like.
[0008] In some embodiments, the upper fairing may optionally be
formed with an overall length dimension corresponding to at least
70% (seventy percent) of a separation distance from a gooseneck for
a boom to a top end of the sailboat mast.
[0009] An upper fairing may optionally include a fairing support
attached to the sail track. The optional fairing support may be
positioned between the sail track and the central segment of the
fairing wrap. The upper fairing optionally includes more than one,
and optionally many, of the fairing support. An example fairing
support optionally includes a front wall formed with a flat surface
on a side facing the mast or alternatively with a radius of
curvature greater than or equal to a radius of curvature of the
curved surface of the sailboat mast; a first side plate coupled to
a left side of the front wall; and a second side plated coupled to
a right side of the front wall opposite the first side plate. When
connected to the fairing wrap, the left-side trailing edge attaches
to the first side plate and the right-side trailing edge attaches
to the second side plate.
[0010] The left-side lower fairing panel may be formed with a
length dimension corresponding to at least 50% of a separation
distance from a front side of the sailboat mast to a clew of the
sail. The right-side lower fairing panel may be formed with the
same length dimension of the left-side lower fairing panel. The
left-side lower fairing panel and the right-side lower fairing
panel are optionally integrally formed as separate pieces strongly
attached to the lower fairing central segment, or may optionally be
integrally formed with the lower fairing central segment.
[0011] Another example apparatus embodiment includes a fairing
configured for sliding contact with a sailboat mast. The example
fairing includes a fairing wrap, a fairing support, and a sail
track attached to the fairing support. The fairing includes a
fairing wrap having a central segment sufficiently pliable to
conform to a curved surface of a sailboat mast; a left-side panel
joined to the central segment, with the left-side panel having a
left-side trailing edge; and a right-side panel joined to the
central segment opposite the left-side panel, with the right-side
panel having a right-side trailing edge. The fairing support is
preferably positioned between the central segment, the left-side
trailing edge, and the right-side trailing edge, with an example
fairing support including a front wall; a first side plate coupled
to a left side of the front wall; and a second side plated coupled
to a right side of the front wall opposite said first side plate.
The front wall of the fairing support may be flat or may
alternatively be formed with a radius of curvature corresponding to
a radius of curvature of the curved surface of the sailboat
mast.
[0012] The sail track may optionally be attached to the first side
plate of the fairing support. Alternatively, the sail track may
optionally be attached to the front wall of the fairing
support.
[0013] Some embodiments of the fairing optionally include a second
of the fairing support positioned between the central segment, the
left-side trailing edge, and the right-side trailing edge; a first
fairing plate attached to the first side plate of the fairing
support and the first side plate of the second fairing support; and
a second fairing plate attached to the second side plate of the
fairing support and the second side plate of the second fairing
support.
[0014] The sail track may optionally be configured to carry one,
and optionally many, sail cars configured to be coupled to a sail
luff. Alternatively, the sail track may optionally be configured to
receive a bolt rope on a sail luff.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a view toward a left side of an example embodiment
of a mast fairing having an upper fairing and a lower fairing
installed on an example sailboat.
[0016] FIG. 2 is a view toward a left side of an example embodiment
of the upper fairing.
[0017] FIG. 3 is a view toward a left side of an example embodiment
of the upper faring having a tapered width, narrower at the top end
than the bottom end.
[0018] FIG. 4 is a cross-sectional view A-A showing an example of
the upper fairing positioned around an example of a sailboat mast,
with the upper fairing and sail in an example of a position for
sailing a boat on a port tack, and the viewing direction from the
top of the mast toward the sailboat hull, and further illustrating
an example of an upper fairing 102 that omits the optional fairing
supports used in some other embodiments.
[0019] FIG. 5 continues the example of FIG. 4, showing the same
example upper fairing and mast in an example of a position for
sailing a boat on a starboard tack.
[0020] FIG. 6 is an example of a turbulent flow region on the
downwind side of a mast along the luff of a sail for a sailboat
using a sailing rig previously known in the art (PRIOR ART).
[0021] FIG. 7 shows a view toward an end of an example of a fairing
support used in some embodiments of an upper fairing, further
illustrating examples of a fairing support with a flat front wall
and an alternative optional configuration with a radiused front
wall.
[0022] FIG. 8 shows a view into an open side of the example fairing
support of FIG. 7.
[0023] FIG. 9 shows an alternative cross-sectional view A-A with an
example upper fairing having the optional fairing support of FIGS.
7-8.
[0024] FIG. 10 is a view toward a left side of an example sailboat
equipped with an alternative embodiment of a mast fairing including
fairing plates attached along the trailing edges of the fairing
wrap for the upper fairing, and further including the lower fairing
example of FIG. 1.
[0025] FIG. 11 shows cross-sectional view B-B with an example upper
fairing having a fairing support configured for attachment of the
fairing plates of FIG. 10, a sail track attached to the front wall
of the fairing support, and the sail track configured to accept a
bolt rope along the luff of an example sail.
[0026] FIG. 12 shows an alternative cross-sectional view B-B with
an example upper fairing having a fairing support configured for
attachment of the fairing plates of FIG. 10, a sail track attached
to the front wall of the fairing support, and a sail track
configured to accept sail cars coupled by toggles to brackets along
the luff of an example sail, and further illustrating an example of
a fairing support displaced away from the surface of the mast with
an intervening gap between the fairing support and the mast.
[0027] FIG. 13 is a front view of an example tack bridle for
allowing the sail tack to displace laterally relative to the boom
as the mast fairing rotates.
[0028] FIG. 14 is a view toward a left side of the example lower
fairing of FIG. 1 and FIG. 10.
[0029] FIG. 15 is a view toward a top edge of the example lower
fairing of FIG. 15, showing an example of a mast cross-section at
the front of the lower fairing.
[0030] FIG. 16 is a partial enlarged view of the lower fairing,
boom, and sail of FIG. 7, illustrating an example of control lines
and other hardware for adjusting the position of the lower fairing
tack along the boom, and further illustrating an example of the
upper edge of the lower fairing extending above the foot of the
sail.
[0031] FIG. 17 is an alternative cross-sectional view B-B showing a
simplified representation of an example roller furler for a sail
attached to an example fairing support.
DESCRIPTION
[0032] Example apparatus embodiments of a mast fairing slidably
engage with a mast on a sailboat to increase aerodynamic lift from
a sail by increasing laminar flow over the sail and reducing an
area of turbulent flow along the luff of the sail. The mast fairing
rotates about the mast in response to changing wind conditions,
sailboat pointing direction, and changes in sail trim, with the
luff of the sail engaged with a sail track attached to the mast
fairing rather than a sail track in or on the mast. The example
mast fairing includes an upper fairing configured to be installed
on the mast above the gooseneck for the boom and an optional lower
fairing configured to be installed on the mast below the upper
fairing and extending along the boom, preferably to the clew of the
sail, and preferably with a top edge of the lower fairing extending
above the foot of the sail.
[0033] Embodiments of the mast fairing are effective for reducing
loss of aerodynamic lift from turbulent flow induced by wind
flowing around the mast onto the upwind and downwind sides of a
sail. For sailboats not equipped with one of the disclosed mast
fairing embodiments, turbulent flow developing along the luff of a
sail is known to reduce the aerodynamic lift from the sail by at
least 35 percent. An additional 25 percent of the lift
theoretically available from a sail can be lost when air passes
under the boom instead of over a sail surface. The disclosed
embodiments are effective for preventing and/or recapturing a
substantial fraction of these losses. Improvements of aerodynamic
lift from the disclosed embodiments are so substantial that a mast
fairing embodiment added to a previously built sailboat enables the
sailboat to be sailed as efficiently without a headsail as a boat
with a headsail that has not been equipped with the mast fairing
embodiment, where efficiency may be defined as a ratio of boat
speed to wind speed. For a new sailboat constructed with a mast
fairing embodiment as part of the original equipment, the mast and
sail may be made smaller and/or standing and running rigging made
lighter to achieve aerodynamic lift and sailing efficiency
comparable to other boats with taller masts and/or larger sails but
lacking a mast fairing.
[0034] For the discussion to follow, directions are given with
respect t to directions commonly used for a boat in the water. The
port side refers to the left side when facing toward the bow of a
boat from the stern. The front side of a part of an embodiment is
the side closest to the bow of the boat when the mast fairing is
installed on a mast. The back side of an embodiment is the side
closest to the stern of the boat when the mast fairing is installed
on a mast. References to the upwind side and downwind side of the
sail and/or mast are made with respect to the apparent wind
direction, where the apparent wind is the vector sum of the boat
velocity and the velocity of the true wind.
[0035] The disclosed embodiments of a mast fairing are most
effective on sailboats with stayed masts and/or a sail coupled to a
sail track and raised and lowered by a halyard. The illustrated
examples of a sailboat show a mast with a boom attached by a
gooseneck and spreaders attached to the mast. Some standing rigging
has been omitted in the figures to avoid visual clutter, but it
will be appreciated that the disclosed embodiments are effective on
sailboats whether or not the sailboat uses spreaders, a forestay,
and/or a backstay. Furthermore, although the examples to follow use
a mainsail as an example of a sailboat sail, the embodiments are
effective for other types of sails. For example, embodiments are
effective for improving laminar flow over a mizzen set on a
mizzenmast.
[0036] Turning now to the example embodiments of a mast fairing in
the figures, FIG. 1 shows an example of a sailboat 1000 equipped
with an example embodiment of a mast fairing 100 including an upper
fairing 102 and a lower fairing 104. FIGS. 2-3 show some additional
details of examples of the upper fairing 102. The view in FIG. 1 is
toward the port side 1018 of a sailboat hull 1004 having its bow
1014 at the left side of the figure and the stern 1016 at the right
side of the figure. An example forestay 1010 extends from the bow
1014 to a front side of the mast 1002. In the example of FIG. 1,
two spreaders 1070 extend outward toward the viewer from the left
side of the mast 1002. Two more spreaders extending out from the
right side of the mast are not visible in the figure. At least one
shroud 1082 may be present to stabilize the mast 1002. When
installed, an example backstay 1012 extends from the stern 1016 to
the back side of the mast, possibly to a masthead cap or masting
casting 1022. A mainsheet 1042 provides position control of the
boom 1006. An optional yang 1040 coupled to the mast 1002 and the
boom 1006 applies a controllable downward force against the sail
1024. An example sail 1024 has a leading edge or lull 1032 slidably
engaged with the upper fairing 102, a trailing edge or leech 1034
joined to the luff at the head 1026, and a foot 1036 opposite the
head 1026. The sail tack 1028 is near the luff 1032 and the foot
1036 and the sail clew 1030 is near the leech 1034 and the foot
1036. An eyelet 1038 near the head 1026 provides an attachment
point for the halyard 128. The sail optionally includes an eyelet
or other fitting 1078 for attachment of a Cunningham downhaul. The
example sail 1024 optionally includes one or more sail battens
1046. The sail battens 1046 optionally extend all the way from the
leech 1034 to the tack 1032 of the sail 1024.
[0037] The upper fairing has an overall length 178 (ref. FIG. 2)
that preferably extends at least 70% of a distance 1076 from a
gooseneck 1008 joining the boom 1006 and the mast 1002 up to the
masthead cap 1022 at the top of the mast 1020. The upper fairing is
most effective for reducing turbulent flow and improving laminar
flow over the sail when the upper fairing has a length 178
approximately equal to the length of the sail luff. The upper
fairing 102 includes a fairing wrap 106 configured to be wrapped
around a front side of the mast 1002 and extending toward the stern
1016 past the back side of the mast. The fairing wrap 106 includes
a central segment 168 that conforms to a radius of curvature 1072
of the front side of the mast (ref. FIGS. 4-5 for examples), a
left-side panel 170 attached to the central segment 168, and a
right-side panel 172 (not visible in FIG. 1) also attached to the
central segment 168. The left-side panel 170 and right-side panel
172 may be formed separately from the central segment 168 and
strongly joined to the central segment, or may alternatively be
integrally formed with the central segment. In some embodiments, a
sail track 110 joins to the left-side panel 170 along a left-side
trailing edge 174 and to the right-side panel 172 along a
right-side trailing edge 176. As will be seen in later figures, in
some embodiments the sail track is attached to a fairing support
108 rather than the trailing edges of the fairing wrap.
[0038] When a sail is present, the luff 1032 of the sail couples to
the sail track 110 in the upper fairing 102 rather than a sail
track attached to or formed as an integral part of the mast 1002.
When the upper fairing 102 rotates about the mast 1002 in response
to changes in wind direction or sailing direction, the sail track
110 and the head 1026, luff 1032, and tack 1028 of the sail 1024
preferably move with the upper fairing. The upper fairing 102 is
prevented from slipping down the mast, for example when the sail is
being lowered, by a fairing line 124 connected to the mast or mast
cap and is prevented from being pulled up the mast, for example
when raising the sail, by another fairing line attached to the mast
and passing through a grommet 126 near the lower end of the upper
fairing.
[0039] For a mast having spreaders or other projections, the upper
fairing 102 may be formed with slots 152 through the central
segment 168 and parts of the left-side panel 170 and right-side
panel 172. The slots 152 enable the upper fairing 102 to rotate
about the mast 1002 without the spreaders or other hardware
projecting from the mast interfering with the rotation.
[0040] In the example upper fairing 102 of FIG. 1 and FIG. 2, the
width 154 at the top of the upper fairing 102 is approximately
equal to the width 156 at the bottom of the upper fairing.
Alternatively, the upper fairing may be formed with a tapering
width increasing from top toward the bottom, with the width 154 at
the top of the upper fairing 102 less than the width 156 at the
bottom of the upper fairing, as suggested in the example of FIG. 3.
For example, the widths (154, 156) in FIG. 2 may differ from one
another by less than about one inch (2.5 centimeters), while the
widths (154, 156) in FIG. 3 may differ from one another by a
substantial amount, for example at least six inches (15
centimeters).
[0041] FIGS. 4 and 5 show examples of an embodiment 100 of the
upper fairing 102 positioned to provide laminar flow around a mast
and onto a sail and reduce turbulent flow along the luff of the
sail. FIG. 4 and FIG. 5 further illustrate an example embodiment of
an upper fairing 102 with the fairing wrap 106 having a central
segment 168 joined to a right-side panel 172 and a left-side panel
170. The central segment is preferably sufficiently pliable to
readily conform to the radius 1072 of the outer surface 1054 of the
mast 1002. A sail track 110 joins to the right-side panel along the
right-side trailing edge 176 and to the left-side panel along the
left-side trailing edge 174. An optional bolt rope attached to the
right-side trailing edge 176 may engage a corresponding channel
formed in the sail track 110. The left-side trailing edge 174 may
be attached to the sail track by a fastener 122. Alternatively,
either one or both trailing edges of the fairing wrap 106 may
attach to the sail track 110 by a bolt rope or by fasteners.
Examples of a fastener 122 include, but are not limited to, a bolt,
a screw, a rivet, adhesive, a fused area, and stitching.
[0042] The example sail track 110 may be formed with a slot or
channel 118 shaped to accept a bolt rope along the luff of a sail
1024. As will be seen in later figures, the sail track may
alternatively be configured to accept sail cars. FIGS. 4-5 further
illustrate an example of a mast formed with a slot 1050 for a bolt
rope along the back side of the mast. The mast slot 1050, when
present, is not used for attachment of a sail when the mast fairing
100 is in place on the mast.
[0043] An example of a direction of boat travel is marked by an
arrow 1060 in FIGS. 4 and 5. An example of a relative wind
direction is marked by an arrow 1062. The sail 1024 is curved by
the wind 1062 with the sail convex on the upwind side 1056. The
upper fairing is preferably free to rotate about the mast from a
port broad reach to a starboard broad reach, with the fairing wrap
106 and sail 1024 smoothing airflow around the mast to provide
laminar flow 1066 around the mast and across the upwind 1056 and
downwind 1058 sides of the sail and reducing or eliminating the
size of the region of turbulent flow along the sail luff. FIG. 4
shows an example of the fairing wrap 106, sail track 110, and sail
1024 positioned for sailing on a port tack (wind coming over the
port side 1018 of the sailboat 1000). FIG. 5 shows the same
embodiment 100 as FIG. 4, but rotated into position for sailing on
a starboard tack. In the examples of FIGS. 4 and 5, laminar flow
1066 around the mast and along the luff on both sides of the sail
is established and maintained on both tacks and regions of
turbulent flow along the luff are reduced in size or eliminated,
compared to a mast and sails without a mast fairing.
[0044] In contrast to the laminar flow 1066 established by mast
fairing embodiments 100, FIG. 6 shows an example of a region of
turbulent flow 1064 resulting from an apparent wind 1062 flowing
past a mast 1002 for a boat not equipped with an embodiment 100,
with the boat traveling in the direction 1060. The region of
turbulent flow, represented in the figure by a pattern of vortex
symbols along the sail luff on the downwind side of the sail, is in
reality more chaotic than suggested by the regularity of the
symbols in the figure. The region of turbulent flow 1064 reduces
the area of the sail subjected to laminar flow and reduces the
aerodynamic lift from the sail, under some conditions by at least
20%.
[0045] As suggested in the examples of FIGS. 1, 2, 3, and elsewhere
in the figures, some mast fairing embodiments 100 include an upper
fairing 102 having fairing supports 108 positioned to move the sail
track 110 and parts of the fairing wrap 106 away from the mast to
provide laminar flow around a protected space between the mast and
the sail luff. A furling system and/or other equipment attached to
the mast may be placed in the protected space without the equipment
causing turbulent flow over the sail. The fairing supports are not
held firmly to the mast and may move away from the mast for some
installations and some sailing conditions without causing problems
for the sail track and other parts of the upper fairing. The
example fairing support 108 of FIGS. 7-8 includes a front wall 130
with an approximately flat exterior surface. Two support plates 132
are joined to the front wall 130. Each support plate 132 optionally
includes one or more apertures 136 for receiving fasteners 122 to
attach a sail track and/or fairing wrap 106. As suggested by the
phantom lines in FIG. 7, the front wall 130 may alternatively be
formed with a radius of curvature 134 greater than or equal to a
corresponding exterior radius of curvature 1072 on a surface of a
mast. The front wall 130 may have a layer of slippery material
affixed or a layer of slippery material may be applied to the mast
in the vicinity of the contact area for the fairing support,
although some mast surfaces will not need such slippery material
for good response of the mast fairing to changes in wind
conditions, for example because the fairing supports may not be in
contact with the mast during some sailing conditions.
[0046] An example of the fairing support 108 of FIGS. 7-8 is shown
in alternative section A-A in FIG. 9. When installed in an upper
fairing, the optional fairing supports are interposed between the
aft exterior surface of the mast 1002, the left-side panel 170 and
right-side panel 172 of the fairing wrap 106, and the sail track
110. In the example of FIG. 9, the fairing support 108 and the
left-side panel 170 and right-side panel 172 attach to flanges 138
extending forward toward the mast from the sail track 110.
Alternately, the left-side panel 170 and right-side panel 172
attach directly to the support plates 132 of the fairing support
108.
[0047] FIG. 9 shows an example of a mast 1002 omitting an internal
sail track and an external sail track attached to an outer surface
of the mast. FIG. 9 further illustrates an example of an embodiment
100 including a sail track 110 formed with a channel 118 configured
to accept sail cars 140. Each sail car includes a toggle engaging a
corresponding toggle bracket 142 bolted or riveted to the luff of
the sail 1024.
[0048] A fairing support 108 may optionally be configured to hold
fairing plates 116 positioned to cover a gap that may exist between
the mast and the luff of the sail. As suggested in the example of
FIG. 10, each fairing plate 116 is attached to at least one, and
generally at least two, fairing supports 108. The optional fairing
plates 116 provide for smooth laminar flow between the fairing wrap
and sail for embodiments 100 having the sail track attached to the
front wall of the fairing support, as suggested in the examples of
a mast fairing 100 in FIGS. 10-12.
[0049] Another advantage of a mast fairing 100 including fairing
plates is the space provided between the mast and fairing plates
for sail furling equipment along the mast, for example an external
mainsail roller furling system. Roller furling provides a safe and
convenient way to reduce sail area, but the rolled portion of a
partially-furled sail is known to substantially increase turbulent
flow along the sail luff, decrease laminar flow, and therefore
decrease sailing efficiency. When external roller furling is
installed on the mast, the furling drum and possibly other parts of
the furling system may be attached to fairing supports 108, thereby
enabling the furling system and the furled portion of the sail to
rotate around the mast with movement of the upper fairing 102. The
fairing plates 116 cover the furling drum and the partially furled
sail, improving laminar flow around the mast and onto the unfurled
part of the sail, substantially improving sailing performance with
a furled sail compared to a boat without a mast fairing 100. The
fairing plates 116 closest to the gooseneck 1008 may optionally be
cut away as at 184 to make room for a flaked mainsail or a mainsail
rolled around the boom. An example of a simplified representation
of a roller furler 1086 for a sail is shown in FIG. 17, with the
roller furler attached to a fairing support 108 to enable the
roller furler to rotate with the upper fairing 106.
[0050] FIG. 11 shows cross-sectional view B-B of an example fairing
support 108 having a sail track 110 attached to the front wall 130
of the fairing support. In the example of FIG. 11, the sail track
110 is configured to accept a bolt rope 1052 attached to the luff
of the sail 1024. The bolt rope 1052 slidably engages a channel 118
formed in the sail track. Sail slugs or sail slides 1048 may
optionally replace the bolt rope 1052.
[0051] FIG. 12 replaces the sail track configured for a bolt rope
or sail slides of FIG. 11 with a sail track 110 configured to
accept sail cars 120. For the examples of FIGS. 11 and 12, the
right-side panel 172 and a first fairing plate 116 are both
attached to a first support plate 132, and the left-side panel 170
and a second fairing plate 116 are attached to the second support
plate 132 of the fairing support 108. As in FIG. 11, the embodiment
of FIG. 12 has the right-side panel 172 of the fairing wrap 106 and
a first fairing plate 116 attached to a first support plate 132 of
the fairing support 108 and the left-side panel 170 and a second
fairing plate 116 attached to a second support plate 132. FIG. 12
further illustrates that the fairing spacer 108 may become
displaced away from the mast by a gap 196 under some sailing
conditions and the upper fairing 102 will continue to function
properly, for example by rotating freely around the mast with
changes in the direction of the apparent wind. For some optional
installations, the size of the gap 196 may be selected to allow the
fairing spacer 108 to rotate around the mast without damaging an
external sail track affixed to the back side of the mast. An
external sail track attached to the mast, if present, is not used
by the mast fairing 100, and may be removed from the mast when an
embodiment 100 is to be installed.
[0052] For some installations of a mast fairing 100 it may be
advantageous to provide a tack bridle 114 that enables the sail
tack to displace laterally with rotation of the mast fairing 100 to
avoid twisting the sail. An example of a tack bridle 114 configured
for sliding connection of a downhaul to the sail tack is shown in
the example of FIG. 13. A transverse rod 164 passes through the
tack eyelet of the sail. Bridle lines 158 with a fixed attachment
162 to a bridle control line 194 attach with shackles 160, rings,
or the like to opposite ends of the transverse rod 164, passing
around the boom with the fixed attachment 162 below the boom and
the bridle control line 194 led aft to the cockpit through turning
blocks on the mast and deck (not illustrated). The tack of the sail
is free to slide along the transverse rod 164 as the upper fairing
102 rotates about the mast, preventing sail twist along the foot
and luff near the tack.
[0053] FIGS. 14-15 show some features of an example lower fairing
104. The example lower fairing 104 includes a lower fairing central
segment 190 configured to wrap around a front side of the mast
1002. A lower fairing left-side panel 186 and a lower fairing
right-side panel 188 are joined to, or alternately formed as an
integral part of, the lower fairing central segment 190. A lower
fairing length dimension 182 from the front of the mast to the back
edges of the lower fairing right- and left-side panels is
preferably at least as long as a separation distance between the
tack and clew of the sail. A lower fairing clew 180 is provided on
each of the lower fairing right- and left-side panels to engage
with a lower fairing outhaul 148 coupled to the boom, as shown for
example in FIG. 1, FIG. 10, and FIG. 16. The aft end 144 may be
angled to provide clearance around a sailboat cabin, dodger,
winches, or other structures within the area swept by movements of
the lower fairing. The side panels of the lower fairing may
optionally include windows 146 made from a transparent material to
facilitate visibility through the lower fairing. The side panels of
the lower fairing may further optionally include a vertical batten
150 affixed to the lower channel side panel or alternatively held
in a batten pocket. The upper ends of the battens are preferably
displaced away from the top edges 192 of the lower fairing 104 to
enable the top edges 192 to extend smoothly upwards past the foot
of the sail and/or around the sides of the boom.
[0054] FIG. 16 shows a partial enlarged view of parts of an example
lower fairing 104, boom 1106, and sail. A sail outhaul 1084 passes
through an eyelet at the clew 1030 of the sail and around a pulley
in the boom (not visible), with the sail outhaul optionally led
through the boom to the mast and aft to the cockpit in the
conventional manner. In the example embodiment 100 of FIG. 1, the
upper edge 192 of the lower fairing 104 does not extend as high as
the foot of the sail 1036. FIG. 16 illustrates an optional
alternative configuration in which the upper edge 192 of the lower
fairing extends over the foot of the sail. In another alternative
embodiment, the upper edges 192 of the lower fairing reach up to
the bottom of the boom without extending up the sides of the boom.
The lower fairing 104 extends along the boom with the upper edge
192 of the lower faring below the foot of the sail 1036 in the
example. A lower fairing outhaul 148 passes through the clew 180 of
the lower fairing 104 and around an outhaul block 198 suspended
from the sail outhaul 1084, providing for adjustment of the main
clew and lower fairing clew positions with a single line. The lower
fairing outhaul 148 joins to a control line 200 led to the mast and
back to the cockpit. The control line 200 is preferably elastic to
hold the lower fairing in tension while sailing. The lower fairing
may be depowered rapidly by slacking the control line 200.
[0055] Unless expressly stated otherwise herein, ordinary terms
have their corresponding ordinary meanings within the respective
contexts of their presentations, and ordinary terms of art have
their corresponding regular meanings.
* * * * *