MAST FAIRING FOR A SAILBOAT
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.
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.
BACKGROUNDA 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.
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.
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.
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.
SUMMARYAn 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Turning now to the example embodiments of a mast fairing in the figures,
The upper fairing has an overall length 178 (ref.
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.
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.
In the example upper fairing 102 of
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.
An example of a direction of boat travel is marked by an arrow 1060 in
In contrast to the laminar flow 1066 established by mast fairing embodiments 100,
As suggested in the examples of
An example of the fairing support 108 of
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
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
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
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.
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.
Type: Application
Filed: Aug 18, 2021
Publication Date: Feb 24, 2022
Inventor: Donald Butler Curchod (Avalon Beach)
Application Number: 17/405,971