WO2012094731A1

WO2012094731A1 - Microairfoil and method for rigging and control

Info

Publication number: WO2012094731A1
Application number: PCT/CA2011/050749
Authority: WO
Inventors: Peter Reginald DERVILLER
Original assignee: Windward First Marine Technology Development Partnership, British Columbia
Priority date: 2010-12-08
Filing date: 2011-12-06
Publication date: 2012-07-19

Abstract

The present invention relates to ways to construct, rig and operate a headsail as a microairfoil (1) for a sail to its aft, for example a mainsail (M), to amplify upwash ahead of the aft sail and smoothly direct airflow over the mainsail (M).

Description

MICROAIRFOIL AND METHOD FOR RIGGING AND CONTROL

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from United States Provisional Patent Application Serial Number US61/421.201 filed on December 8, 2010, entitled MicroAirfoil, which, where allowed under governing patent law, is expressly incorporated by reference herein.

BACKGROUND

1. Field

The present invention is directed to the field of fore-and-aft rigged sailing craft and a method of headsail design, construction, rigging, operation and control. The invention applies equally to all fore-and-aft rigged sailing craft, whether for traversing land or water or ice for example (generically hereinafter called "yachts"). For the most part, the widely familiar water traversing sailboat will be used to illustrate the invention. 2. Description of Related Art

If a yacht can point higher (i.e. closer to the direction of the wind) than other yachts, its upwind distance travelled toward its destination will be less than that for the other yachts, which must tack crosswind more in order to make progress to windward, following a more zig zag and thus less direct course. The ability of a yacht to point higher is highly prized by yacht racers; cruising sailors also often strive to sail as close to the wind as possible for pleasure, convenience and safety.

However, in over 5000 years of sailing history, sailing vessels that attempted to sail directly into wind would immediately go into irons, that is to say stop dead, or even sail backwards. To this day, sailing directly to windward is widely considered to be impossible. Sails of the conventional, single surface or membrane type are sensitive to angle of attack, which is the angle between the chord of a sail and the local airstream. The local airflow ahead of the sail system, termed in this document "micro-airflow", is the airstream adjacent to the sail that is different in speed and direction from the ambient airflow surrounding the yacht but beyond its influence.

Unlike an aircraft wing that is relatively deep in its mid section and has a bluff nose, a sail that may be no thicker than a sheet of paper has a fine leading edge (luff) over which air will only flow smoothly when it is pointed very closely to the direction of the micro-airflow immediately ahead of it. A given sail will perform at its optimum only within a range of a few degrees of angle out of alignment with the micro-airflow. The double surfaced wingsail is not as sensitive as the single surface sail to angle of attack. However, the wingsail is more complex than a conventional sail and tends to be fragile, which limits its practicality to specialized vessels such as high end racing yachts. Local airflow may differ substantially in speed and direction from the ambient or true wind surrounding the yacht but beyond its influence. A well known example of this difference is the "apparent wind" which is the resultant vector of the true wind and the wind from directly ahead that is generated by the forward motion of the vessel. When the vessel is in motion the sails are only affected by the micro-airflow of the apparent wind. The sails of a yacht sailing at speed will be subjected to an apparent wind that is closer to its bow than the true wind but there is a lower limit to the sails' angle of attack below which the airflow will separate, become turbulent and the sails will deflate or luff.

If the vessel was pointed to zero degrees or head-to-wind, and it was possible to artificially create - for example with a giant fan - a micro-airflow to match the optimum angle of attack of the sail(s), the yacht would indeed sail directly into the true wind, but this is conventionally thought to be impossible in practice. However, local airflow can be naturally deflected. For example, early 20th century exponents of sailing theory, notably Dr. Manfred Curry and contemporary aerodynamicists such as Arvel Gentry, have described and demonstrated the "upwash effect", which is deflection of the oncoming airflow toward a sail's leeward surface.

One practical application of airflow deflection occurs when yacht racers in close proximity and on parallel courses strive for the lee bow advantage, wherein the sail system of the competitor to leeward gains a "lift" from the windward yacht that is upwashing and accelerating the micro-airflow. The leeward yacht further disadvantages the windward yacht by channeling exhaust from its sail system onto the windward yacht's sails. Clearly local airflow around a sail system can be redirected.

Accordingly, what is needed is a better way for a yacht to amplify upwash ahead of its own sail system. SUMMARY

The present invention is directed to this need.

The present invention amplifies upwash ahead of the mainsail by adding to it an airfoil-shaped leading edge - described in this document as a "microairfoil"- that is cambered in the manner of the leading edge of an aircraft wing. One objective of the present microairfoil invention is to amplify upwash of the local airflow ahead of the microairfoil / mainsail combination sail system, thus sustaining smooth airflow over the sail system with the yacht pointed close to the wind at an angle that would normally luff the sails and put the yacht into irons.

One embodiment of a microairfoil is similar to a conventional triangularly shaped headsail, except that its method of rigging is reversed. In other words, instead of the luff of the sail being secured to a headstay with the leech free to swing from port to starboard in the conventional manner, the microairfoil's luff is free and its leech is secured at the mast. Such a microairfoil combined with the mainsail creates a single large airfoil extending from close to the bow of the yacht all the way back to the tip of the main boom. And as established by Arvel Gentry, an effective mainsail augments the performance of the headsail and boosts the overall performance of the sail system, the mainsail in effect being the main driver of airflow circulation around the sail system.

In addition to the objective of causing the yacht to point higher, are the microairfoil's benefits of: (1 ) providing additional sail area to increase thrust and (2) opening the slot between the headsail and the microairfoil to reduce the restriction of airflow between them.

The driving force of a sail system depends, among other factors, upon the surface area of the sails. Flexibility in the regulations governing allowable sail area for racing yachts permits additional sail area, in general with a handicap penalty. Embodiments of the present invention can add 50% or more to the area of the mainsail.

Many yachts are equipped with a second headsail, usually called a staysail or cutter rig. The second sail adds area and enhances airflow - up to a point. However, when sailing upwind, too large a staysail will block airflow on the windward side of the sail ahead of it. The microairfoil of the present invention eliminates this problem by being swung clear of the headsail on a close hauled point of sail.

The microairfoil is practical, being inexpensive to manufacture, quick to rig, raise and lower, easy to control and robust in adverse weather conditions. A microairfoil can be built without special manufacturing technology and current materials and methods of sail fabrication and architecture may be utilized, including wingsail technology. In a single surface microairfoil, battens are used to control draft. Battens may be adjustable in compression to modify their camber. Tapered battens vary the profile of the microairfoil to match the camber in the forward part of the mainsail by smoothly blending the two surfaces into a larger airfoil. The microairfoil may incorporate a special mast whose cross section is shaped to blend or "fair" the leech area of the microairfoil into the luff area of the mainsail.

Thus, according to one aspect of the present invention, there is provided an apparatus for affecting airflow adjacent an aft sail mounted on an aft side of a mast on a yacht, the mast also having a top and a base and a forward side opposite the aft side and the yacht having a deck, having: means for amplifying upwash of a micro-airflow component of the airflow and means for mounting the amplifying means on the yacht to direct the amplified upwash to the aft sail. The mounting means may further include means for trimming the amplifying means. The amplifying means may be a microairfoil, for example formed from a headsail having a leech, a luff, a foot, a clew, a head and a tack. The luff may have a bluff edge.

In such an arrangement, the mounting means might include means for connecting the clew of the headsail to the forward side of the mast near its base and means for connecting the head of the headsail to the forward side of the mast near its top. The trimming means might include means for applying tension to the foot of the headsail between the tack and the clew and means for tacking the luff of the headsail laterally through an arc about an axis along its leech.

The trimming means could be implemented with a starboard sheet and a port sheet connectable to the tack and operable as tension means and/or tacking means. In this regard, the trimming means might further include a starboard turning block and a port turning block positionable on the yacht to respectively route the starboard sheet and the port sheet to operate as tension means and/or tacking means.

Furthermore, the tension means might include a pole, perhaps telescopic, having a forward end adapted for connection to the tack and an aft end adapted for connection to the mast. The pole may include a yoke towards its forward end, as the adaptation for connection to the tack. In such case, the starboard sheet and the port sheet may be connectable to the tack via the yoke.

The tension means may further include a downhaul adapted to connect the tack to the deck. The downhaul may be adapted to connect to the tack via the pole or via the yoke. The tension means may further include a track adapted to connect the downhaul to the deck, the track perhaps having a geometric center close to the axis of the leech.

The tension means may further include an outhaul adapted to connect the tack to the forward end of the pole. The outhaul may be adapted to connect the tack to the forward end of the pole via the yoke.

To smooth airflow, the amplifying means may include fairing on the surface of the mast between the microairfoil and the aft sail and may include sealing between the microairfoil and the mast.

According to another aspect of the present invention, there is provided a yacht having the apparatus as variously described just above.

According to another aspect of the present invention, there is provided a method for affecting airflow adjacent an aft sail mounted on an aft side of a mast on a yacht, the mast also having a top and a base and a forward side opposite the aft side and the yacht having a deck, including: amplifying upwash of a micro-airflow component of the airflow and directing the amplified upwash to the aft sail. In this regard, directing may include at least one of mounting and trimming a microairfoil, for example a headsail having a leech, a luff, a foot, a clew, a head and a tack. More precisely, mounting a headsail may include connecting the clew of the headsail to the forward side of the mast near its base and connecting the head of the headsail to the forward side of the mast near its top. Trimming a headsail may include applying tension to the foot of the headsail between the tack and the clew and tacking the luff of the headsail laterally through an arc about an axis along its leech.

Furthermore, mounting a headsail may include connecting an aft end of a pole to the mast and connecting a forward end of the pole to the tack. In this case, mounting a headsail may also include yoking the forward end of the pole with a yoke and connecting the forward end of the pole to the tack via the yoke. Additionally, trimming a headsail might include connecting an outhaul between the yoke and the pole and connecting a downhaul between the yoke and the deck. To smooth airflow, directing may also include blending a surface of the mast between the microairfoil and the aft sail and sealing between the microairfoil and the mast.

According to another aspect of the invention there is provided a new use for a headsail as a microairfoil for an aft sail. In this regard, the head sail may be used as a bluff leading edge for an aft sail, for example to amplify upwash and/or deflect airflow to the aft sail. In this way, the head sail may be used to form an airfoil in combination with the aft sail.

Further aspects and advantages of the present invention will become apparent upon considering the following drawings, description, and claims. DESCRIPTION

The invention will be more fully illustrated by the following detailed description of non-limiting specific embodiments in conjunction with the accompanying drawing figures. In the figures, similar elements and/or features may have the same reference label.

1. Brief Description of the Drawings

Figure 1 is a front view of a conventional, prior art wind indicator, showing a "no-go zone" from starboard 20 degrees to port 20 degrees.

Figure 2 is an oblique drawing of a yacht with a microairfoil in accordance with an embodiment of the present invention.

Figure 3 is a side view of the microairfoil of Figure 2, in isolation.

Figure 4 is a plan view of the yacht and microairfoil of Figure 2.

Figure 5 is a side view of the microairfoil of Figure 2 in relation to a mast on the yacht of Figure 2 and a pole extending forwardly from the mast.

Figure 6 is a side view of a lower portion of the microairfoil of Figure 2 in relation to the mast and the pole of Figure 5, detailing a second rigging arrangement.

Figure 7 is a front elevational view of the pole of Figure 5, detailing a third rigging arrangement for the microairfoil of Figure 2, including a control yoke.

Figure 8 is side view of a lower portion of the microairfoil of Figure 2, detailing a fourth rigging arrangement, including a curved track.

2. Detailed Description of Specific Embodiments

The structure, construction, rigging and operation of the invention will now be illustrated by explanation of specific, non-limiting, exemplary embodiments shown in the drawing figures and described in greater detail herein. (a) Terminology

(i) In General

In this document, the terms such as sailboat, craft, vessel and yacht are interchangeable.

The term fore-and-aft rig applies to all craft on which a sail is secured along its forward edge to a stay or mast that forms its axis of rotation. Fore and aft sail types include, but are not limited to: Bermuda jib, genoa and mainsail, staysail, gaff, gunther, and spanker.

Fore-and-aft rigs include rigs with one mast such as the sloop, cat and cutter and rigs with two or more masts include the ketch, yawl, schooner, barque and barquentine.

Other sailing craft with fore-and-aft rigs to which the present invention applies are land yachts and ice yachts.

(ii) Specifically Defined Terms

Athwartship Across the yacht

AWA Apparent Wind Angle

Wire, line or rod that provides support to the mast from

Backstay

the stern

Square rigged yacht with three or more masts, fore-and-

Barque aft rigged at the aftermast and also at the headstay and forestays

Three-masted yacht square rigged only on the foremast;

Barquentine

remainder of sails fore-and-aft rigged.

Thin, flexible strip of wood or plastic to support a sail's

Batten

horizontal curvature

Side of yacht or the dimension from one side of yacht to

Beam

the other

Belay Make fast a line

Also known as Marconi Rig; comprises a triangular

Bermuda Rig headsail before the mast and a triangular mainsail aft of it

Pulley or sheave for force multiplication and to change

Block

direction of a line or halyard Rope sewn into the edge of sail that engages in a slot or

Bolt Rope

track in a spar or mast

Boom Spar attached to the mast to support one edge of a sail

Bow The front of the yacht

Bowsprit Spar extending forward of the bow to secure headstay

Camber Curved profile of an airfoil above its chord

Fitting that travels smoothly on a track or in a slot for

Car positioning and restraining the edge of a sail; also for positioning and restraining jib/mainsheet blocks

Yacht with one sail - the mainsail; mast stepped well

Cat Rig

forward

An imaginary line joining two ends of an arc, in the case

Chord

of a sail, joining it's luff to its leech

Post, jaw or clutch for securing a line and maintaining its

Cleat

tension

Clew Aft lower corner of sail

Close Hauled Sailing as close to the wind as efficiency permits

Single masted yacht with mast stepped more amidships

Cutter Rig

than on a sloop; usually with two headsails Deflate Sail collapse

Loop shaped fixture typically mounted on the front of a

D Ring

mast for attachment of a spinnaker pole's jaw

Control line for exerting downward force on a spar, pole

Downhaul

or boom

Ratio of length of a sail's inflated depth to its chord

Draft

expressed as a percentage

Eye of the Wind Direction from which the wind is blowing

Fin A rigid or resilient airfoil

Foot Bottom edge of a sail

Conventionally, sails secured along their forward edge or

Fore-And-Aft Rig luff to vertically oriented mast(s) or stay(s); uniquely, microairfoil is secured on its aft edge or leech

Wire, rod or line that provides aft support to the mast on

Forestay

which headsails and staysails are often set

Foretriangle The zone bounded by the mast, foredeck and forestay

Quadrilateral fore-and-aft mainsail with mast mounted

Gaff Rig

gaff spar or boom at its head

Genoa Large jib that overlaps the mast Quadrilateral fore-and-aft mainsail with sliding or

Gunther

telescopic gaff spar at its head.

Top edge of the side of the yacht where it meets the

Gunwale

deck

Halyard Line for raising and securing a sail

Hank Clip or ring on edge of a sail for attaching it to a stay

Head Corner of triangular sail closest to masthead

Any of several sails set forward of the mast in the

Headsail

foretriangle

A wire or rod that provides support to the mast attached

Headstay

at the bow or forward of the forestay(s) on a bowsprit

In Irons Yacht head to wind with sails deflated

Sail stretched into its design shape by aerodynamic

Inflate

forces

Quick release fitting on a pole for capturing a line or a

Jaw

fixture such as a D ring

Jib Triangular sail set on the headstay

Ketch Two masted yacht with rudder post aft of both masts

Leading Edge The forward or nose section of an airplane's wing Leech The aft edge of a sail

Leeward Away from the wind

Component of airfoil's aerodynamic force perpendicular

Lift to apparent wind. Also describes a change of apparent wind direction toward the beam

Line Rope used as a halyard or sheet

Luff The forward edge of a sail

Mainsail Fore and aft sail set on the aft side of the mainmast

Mast Vertical spar to support rigging, booms and sails

Single surface sail as opposed to a double surface or

Membrane Sail

wingsail

The local airstream that an airfoil is subjected to (e.g.

Micro-airflow apparent wind), in the case of a sail, just forward of its luff

Control line for exerting tension on the foot of a sail along

Outhaul

the axis of a spar, pole or boom.

Point of Sail Yacht's course relative to the direction of the wind

Port Left-hand side of a yacht when facing toward the bow Yacht configured with its mainsail swung to starboard of

Port Tack

the yacht's centerline

Reaching The point of sail with wind from toward the beam

Running The point of sail with wind from toward the stern

Sag Deflection of sail or stay under aerodynamic forces

Unless otherwise indicated explicitly or by context, a fabric or otherwise flexible airfoil, the fullness or direction

Sail

of which depends at least partially on the oncoming airstream in which it is immersed

Sail System A combination of sails rigged on a yacht

Yacht with two or more masts, usually the foremast is

Schooner smaller than the mainmast; lower masts are often gaff- rigged

General purpose detachable fitting - usually metal - for

Shackle many uses such as attaching halyards and sheets to sails.

Sheet Line for trimming a sail's shape and position

Low friction shoe or slug that moves along a slot or track

Slide

for positioning and restraining the edge of a sail Typically a Bermuda/Marconi configuration with single

Sloop Rig

mast and triangular sails

On a square rigged yacht, the spanker is a gaff rigged

Spanker

fore-and-aft sail set from the aftmost mast.

Flying sail that is only attached to halyard and sheets at

Spinnaker

its corners for the running and reaching points of sail

Spar for controlling the clew of a headsail, notably the

Spinnaker Pole

spinnaker

Sails set on horizontally oriented spars or yards slung

Square Rig

athwartship from the forward side of mast(s)

Starboard Right-hand side of a yacht when facing toward the bow

Yacht configured with its mainsail swung to port of the

Starboard Tack

yacht's centerline

Stay Wire, rod or line that provides support to the mast

Staysail Triangular sail set on a forestay or between masts

Stern The back of a yacht

Tack Forward lower corner of a sail

Component of an airfoil's total aerodynamic force that

Thrust

drives a vessel forward Deflation of a sail usually caused by pointing the vessel

To luff

too closely to the eye of the wind

Turning the yacht toward the direction from which the

To Point

wind is blowing

Turn a yacht by sail and rudder through the eye-of-the-

To Tack

wind

Control the position and shape of a sail and in general,

To Trim

adjust, alter, modify or fine tune a yacht

Slotted metal extrusion along the gunwale that reinforces

Toe Rail the hull structure and provides mounting points for blocks, stanchions etc.

Trailing Edge The aft edge of an airplane wing

The actual wind the vessel would be subjected to if it

True Wind

was motionless

Phenomenon of upward deflection of an airstream

Upwash flowing toward an airfoil; angular difference between the apparent wind and the micro-airflow

Manual or mechanically powered drum or sheave geared

Winch

to multiply tensile force on a line or halyard

Windward Toward the wind A double surface airfoil; an airfoil having a significant

Wing

cross-section

An airfoil having at least one double surface portion,

Wingsail

including a rigid, resilient or flexible airfoil

Two masted yacht with after mast stepped behind rudder

Yawl

post

(b) Structure, Construction and Rigging of Specific Embodiments

13 outhaul

13A outhaul cleat

14 downhaul

14A track

15 mast

16 groove

17 control yoke

18 shackle

19 halyard

Figure 1 is a sketch of a face of a conventional wind indicator, for example a model ST60 Plus offered by Raymarine Inc. of 21 Manchester Street, Merrimack, NH 03054, United States of America. Such conventional wind indicators confirm the orthodox expectation that a yacht cannot sail at closer than a 20 degree apparent wind angle, as illustrated by the fact that the measurement scale ends at 20 degrees and there are no graduations below that value.

Figure 2 shows a microairfoil according to one embodiment of the present invention, generally illustrated (in heavy outline) at 1 as rigged on a yacht Y. The microairfoil 1 is rigged in close combination with a sail immediately aft of it, in this case a mainsail M. In this way, the microairfoil 1 forms a leading edge of a larger airfoil in combination with the mainsail M. The yacht Y may also have a conventional headsail H, for example a jib or genoa, forward of the microairfoil 1.

In Figure 3 it can be seen that the microairfoil 1 can be embodied much like a conventional headsail having a leech 2, a luff 3, a foot 4, a clew 5, a head 6, and a tack 7. The clew 5, head 6, and tack 7 each may have a respective reinforcement ring 10 for better attachment to sheets, control lines and halyards, as described further below. The microairfoil 1 can be constructed as a single surface or membrane in the manner of a conventional headsail with a high-tensile-strength leech 2 and luff 3. In some embodiments, the headsail can be constructed such that the luff 3 presents a bluff leading edge, for example as a result of the luff 3 comprising material that is thicker than the material at other portions of the microairfoil 1. As still a further alternative, the headsail can be constructed as a flexible double surface wingsail or a rigid double surface wingsail, for example. So configured, and once mounted in position with respect to the mainsail M and trimmed with regard to the wind and the movement of the yacht Y, all as described more fully below, the headsail microairfoil 1 functions as a means for amplifying upwash to the mainsail M.

(1) Basic Rigging Arrangement

A starboard sheet 8 and a port sheet 9 attach to the tack 7 of the microairfoil 1 at its reinforcement ring 10. Notably, the microairfoil 1 is configured differently from a conventional headsail, inasmuch as the sheets 8, 9 are attached at the tack 7 instead of the clew 5.

As shown in Figure 1 , the yacht Y is on a starboard tack requiring the microairfoil 1 to be trimmed to starboard and aimed toward the direction from which the wind is blowing. The angular rotation of the microairfoil 1 from the centerline of the yacht is shown by dashed lines. The sheets 8, 9 facilitate tacking the microairfoil 1 laterally through an arc about the axis of its leech 2 so that its luff 3 is trimmed to windward on either the port or starboard tack.

Figure 4 more fully illustrates this reversed rigging of the microairfoil 1 on the yacht y, wherein the luff 3 is free to tack and the leech 2 is captured at a mast 15 to form an axis of rotation for the microairfoil 1. The clew 5 of microairfoil 1 is secured toward the base of the mast 15 and the head 6 of the microairfoil 1 is rigged forward of the mast 15 toward the top of the mast 15 so that the leech 2 of the microairfoil 1 is substantially fixed in alignment with the luff of the mainsail M. In some embodiments, the mast 15 may be fabricated with cross section shaped to blend or fair the leech 2 portion of the microairfoil 1 into the luff portion of the mainsail Mto encourage smoother flow of the airflow.

It can also be seen how the basic controls - the starboard sheet 8 and the port sheet 9 - are configured to tack the microairfoil 1 and trim its lateral position to achieve the optimum angle of attack. The tack 7 is free to swing athwartship in an arc about the axis of the leech 2 so that the luff 3 may be trimmed to windward on either the port or starboard tack. The luff 3 can be tensioned between a halyard 19 at the head 6 and the sheets 8, 9 and control lines attached either directly or indirectly at the tack 7. The leech 2 can be tensioned between the halyard 19 at the head 6 and the attachment point of the clew 5 close to the base of the mast 15. The foot 4 can thus be tensioned between the tack 7 and the clew 5, to span a portion of the distance from the mast 15 to the tack 7. In essence, the starboard and port sheets 8, 9 and control lines (described further below), tied or shackled directly or indirectly to the microairfoil 1 provide a control system to facilitate trimming and control of the microairfoil 1.

The microairfoil 1 sheets 8, 9 may be run through respective turning blocks 8A, 9A (or fairleads) abeam the microairfoil 1 attached to a toe rail of the yacht Y, which routing has the advantage of providing downward tension in addition to the necessary lateral force to tack the microairfoil 1. From the turning blocks 8A, 9A, the sheets 8, 9 may be run aft to the cockpit or cabin top of the yacht Y, to a respective cleat 8B, 9B or clutch, where the sheets 8, 9 may be winched and cleated.

Figure 5 illustrates additional elements that may be used to enhance the functionality and control of the microairfoil 1. Battens 11 support the camber of the microairfoil 1, having a curvature that desirably flows smoothly into the camber of the mainsail M. The battens 11 may be flexible, inflatable or a combination of the two, and may be adjustable in compression and tapered for variable flexibility. In front of the mast 15, a groove 16 can be configured to retain a bolt rope on the leech 2 of the microairfoil 1 or alternatively a sail track can be secured to the front of the mast 15 to slidably engage hanks, slides or cars installed along the leach 2 of the microairfoil 1, thereby removably and slidably mounting the microairfoil 1 on the mast 15, such that the microairfoil 1 may be hoisted with the halyard 19 for use. This arrangement helps to restrict air flow between the leech 2 and mast 15.

(2) Second Rigging Arrangement

Figure 6 illustrates a second arrangement for rigging the microairfoil 1. The clew 5 attaches to the yacht Y close to the base of mast 15. The tack 7 and starboard and port sheets 8 and 9 attach to a pole 12 that extends forward from the mast 15. The pole 12 (or boom or spar or more generally a rigid member, similar to a spinnaker or jib boom) tensions the foot 4 of the microairfoil 1 and provides convenient connection points. The pole 12 may be telescopic to facilitate its rapid conversion to a spinnaker pole when the yacht's heading is altered from an upwind to a downwind course and vice versa.

The pole 12 can be rotatably secured to a D ring 12A or similar fixture on the mast 15 (for example a spinnaker D ring) via a first jaw 12B, to provide a means to secure the tack 7, sheets 8, 9 and other control lines of the microairfoil 1. Such other control lines might include an outhaul 13 at the tack 7 to facilitate adjustment of the draft in the microairfoil 1 and a downhaul 14 secured at one end close to the forward end of the pole 12 and at the other end close to the base of the mast 15 in line with the axis of the leech 2, to counteract upward force in the microairfoil 1 when the sheets 8, 9 are eased during trimming and tacking. In some embodiments, the downhaul 14 may be downwardly diagonally rigged to a point close to the base of the mast 15 to counteract upward force in the luff 3. In some embodiments, the pole 12 might be constructed into or otherwise retained within the foot 4 of the microairfoil 1, for example in a sleeve or pocket, much in the manner of a batten 11.

(3) Third Rigging Arrangement

Figure 7 illustrates a third rigging arrangement that includes a control yoke

17 that yokes the pole 12. The tack 7, sheets 8, 9 and control lines, such as the downhaul 14, can be connected to the yoke 17, for example by respective shackles 18

Focusing loads into the control yoke 17 relieves the pole 12 of bending loads. The yoke 17 concentrates the force from the halyard 19 tensioned luff 3 and the working loads of the microairfoil 1 and the tensile forces in the sheets 8, 9 and downhaul 14.

The yoke 17 also provides a means for adjusting the position of the tack 7 along the pole 12 for draft adjustment.

(4) Fourth Rigging Arrangement

Figure 8 illustrates a fourth rigging arrangement in which the control yoke 17 slides on the pole 12 under control of the outhaul 13 secured by an outhaul cleat 13A

The outhaul 13 can thus be tied or shackled to the tack 7 and/or clew 5 and routed along and cleated to the pole 12 to adjust the position of the tack 7 and/or clew 5 and thereby trim the draft of the microairfoil 1. In this regard, the outhaul 13 is routed along and cleated to the pole 12 in the manner of an outhaul typically fitted to the foot of a mainsail and run along a main boom.

The downhaul 14 is terminated with a slide or car on a curved track 14A to maintain downward tension on the microairfoil 1 during tacking and trimming maneuvers. In some embodiments, the downhaul 14, whether configured as a control line or control arm and whether tied or shackled directly to the tack 7 or the pole 12, may be downwardly rigged to counteract upward force in the luff 3, connected to a car or slide travelling on the curved or semi-circular track 14A, with its geometric center close to the axis of the leech 2.

In some embodiments, the pole 12 might include a second jaw 12B' opposite the first jaw 12B to engage directly or indirectly, for example, the tack 7, or in some embodiments sheets 8, 9 and control lines of the microairfoil 1.

(c) Operation of Specific Embodiments

In a single surface embodiment, the microairfoil 1 is hoisted and tensioned with a conventional jib or spinnaker halyard 19 such as is found on virtually all yachts Y attached to the head 6. The clew 5 of the microairfoil 1 is secured close to the base of the mast 15, either by shackling it to the D ring 12A or belaying it to another convenient point, such as a collar that is fitted around the base of the mast 15 of many yachts Y for the purpose of anchoring blocks and stowing the shackle ends of idle lines. When the leech 2 of the microairfoil 1 is free flying between its clew 5 and head 6 attachments, under pressure the leech 2 will sag to leeward, which permits air to leak from the high pressure windward surface to the low pressure leeward side. By sealing the gap between the microairfoil 1 leech 2 and the forward side of the mast 15 with a boltrope-in-groove or sail track system, pressure is sustained on the windward side of the microairfoil 1 and the mainsail M.

Starboard and port sheets 8, 9 are attached at the tack 7 of the microairfoil 1 and run to turning blocks 8A, 9A at the gunwale, typically shackled to the toe rail. The force in the downwardly angled sheets 8, 9 counteracts the tension in the microairfoil 1 luff 3 created by the halyard 19 and the forces resulting from working loads. A forward angle of the sheets 8, 9 also creates tension in the foot 4 of the microairfoil 1 between the tack 7 and the clew 5. The sheets 8, 9 are typically run from the turning blocks 8A, 9A at the toe rail toward the cockpit where they are tensioned with the aid of winches and locked with clutches or cleats 8B, 9B.

An alternative arrangement for rigging the microairfoil 1 is to attach a rigid member, as illustrated the pole 12, between a point close to the clew 5 and a point close to the tack 7. The first jaw 12B at the aft end of the pole 12 is engaged with the D ring 12A on the mast 15. The second jaw 12B' (or equivalents such as eyes) at the forward end of the pole 12 engage the microairfoil 1 tack 7, sheets 8, 9 and control lines 13, 14, for example either by tying or shackling.

The pole 12 offers an additional benefit by providing the means to attach the outhaul 13 to the tack 7 and/or the clew 5. By adjusting the position of the tack 7 relative to the clew 5 or vice versa, tension in the foot 4 is adjusted with a resultant change in draft that modifies the microairfoil 1 aerodynamic properties to match wind and wave conditions.

A further enhancement is the addition of the downhaul 14 attached to the pole 12 and run to a point close to the base of the mast 12 or to a car or slide travelling on a track 16 on the deck. The sheets 8, 9 can also be terminated on the aforementioned car which concentrates all of the sheets 8, 9 and control lines in a small space and at deck level. The advantage of the downhaul 14 is that it maintains tension in the microairfoil 1 while the crew is easing sheets 8, 9 during trimming or when swinging the microairfoil 1 across the yacht Y in a tacking maneuver.

Additionally, the control yoke 17 or sleeve on the forward end of the pole 12 can be used to cluster all of the sheet 8, 9 and control line 13, 14 attachment points and used to provide a means to slide the tack 7 fore and aft relative to the clew 5 to adjust tension in the foot 4, with a resultant change in draft that modifies the microairfoil 1 aerodynamic properties to match wind and wave conditions. The yacht Y, so rigged with the microairfoil 1 in addition to its conventional rigging, can be sailed as normal, except now having the ability to point higher without going into irons, through operation of the microairfoil 1 to amplify upwash ahead of the mainsail M, deflecting or more generally directing micro-airflow as an airfoil-shaped leading edge for the mainsail M to sustain smooth airflow over the sail system, while also providing additional sail area to increase thrust and opening the slot between the headsail H and the microairfoil 1 to reduce the restriction of airflow between them.

In this regard, when the yacht Y is placed, for example, on a starboard tack, the microairfoil 1 is trimmed to starboard and aimed toward the direction from which the wind is blowing through release of the port sheet 9 and retraction of the starboard sheet 8, thereby tacking the microairfoil 1 laterally through an arc about the axis of its leech 2 so that its luff 3 is trimmed to windward on the starboard tack. The outhaul 13 and the downhaul 14 can be partly or fully released or retracted to additionally trim the microairfoil 1 to the particular conditions to improve upwash amplification and smooth micro-airflow deflection (direction).

(c) Description Summary

Thus, it will be seen from the foregoing embodiments and examples that there has been described ways to construct, rig and operate a headsail as a microairfoil 1 for a sail to its aft, for example a mainsail M, to amplify upwash ahead of the aft sail and smoothly direct airflow over the mainsail M.

While specific embodiments of the invention have been described and illustrated, such embodiments should be considered illustrative of the invention only and not as limiting the invention as construed in accordance with the accompanying claims. In particular, all quantities described have been determined empirically and those skilled in the art might well expect a wide range of values surrounding those described to provide similarly beneficial results. It will be understood by those skilled in the art that various changes, modifications and substitutions can be made to the foregoing embodiments without departing from the principle and scope of the invention expressed in the claims made herein. For example, for the purposes of teaching aspects of the invention, specific combinations and arrangements of common sailing tackle have been assembled to illustrate exemplary ways to rig a headsail as a microairfoil 1, such tackle including sheets 8, 9, control lines such as outhauls 13 and downhauls 14, blocks 8A, 9 A, cleats 8B, 9B, 13A, battens 11, poles 12, tracks 14A, masts 15, grooves 16 and yokes 17. Those skilled in the art will recognize that these and other items of sailing tackle can be arranged in many ways to position, draft and operate a headsail as a microairfoil 1 for an aft sail.

Those skilled in the art will recognize that the microairfoil 1 and the aft sail, for example a mainsail M, in combination present a single combined airfoil. In this regard, the microairfoil and the aft sail may be constructed as two portions of a single, whole, integrated or unitary body.

Those skilled in the art will further recognize that a microairfoil 1 may be constructed as an integrated or unitary portion of a mast 15, such that the microairfoil 1 presents a leading surface of the mast 15 that is operable to be trimmed to windward on port and starboard tacks, such that the microairfoil 1 blends or fairs into the luff area of an aft mainsail thereby amplifying upwash ahead of the aft sail.

Those skilled in the art will also recognize that although a reverse rigged headsail is well-suited for inclusion in a microairfoil 1, a functionally similar microairfoil 1 can be constructed otherwise than with a conventional headsail. For example, a microairfoil 1 may include a resiliently bendable fin that extends forwardly from the mast 15, the fin for example being tangent with the sides of the mast 15 adjacent the mast 15 and tapering narrower forward from the mast 15, the microairfoil 1 having mechanical linkages to bend the tapered end of the fin windward.

Those skilled in the art will further recognize that a microairfoil 1 might include a rigid fin that extends forwardly from the mast 15, the fin for example being tangent with the sides of the mast 15 adjacent the mast 15 and tapering narrower forward from the mast 15, the microairfoil 1 having mechanical linkages to turn the fin, much like a forward-facing rudder, windward.

Those skilled in the art will appreciate that in all of the embodiments and examples provided, there is taught a microairfoil 1 that includes:

(a) means for amplifying upwash, for example a headsail or more generally a sail, fin, wing or wingsail, singly or in combination with a mast 15, and

(b) means for mounting the amplifying means to direct the amplified upwash to an aft sail, for example tackle such as halyards 19, shackles 18, reinforcement rings 10, a pole 12 with one or more jaws 12B, and mast 15 with a groove 16 and a D ring 12A, a control yoke 17 in combinations such as described above or otherwise, and further including means for trimming the amplifying means, for example tackle such as sheets 8, 9, turning blocks 8A, 9A, starboard and port cleats 8B, 9B, battens 11, and control lines such as an outhaul 13 with an outhaul cleat 13A and a downhaul 14 with a track 14A in combinations such as described above or otherwise.

Those skilled in the art will also recognize that a yacht Y may be rigged with more than one microairfoil 1 in accordance with the present invention.

Claims

CLAIMS WHAT IS CLAIMED IS:

1 . An apparatus for affecting airflow adjacent an aft sail mounted on an aft side of a mast on a yacht, the mast also having a top and a base and a forward side opposite the aft side and the yacht having a deck,

comprising:

(a) means for amplifying upwash of a micro-airflow component of the airflow; and

(b) means for mounting the amplifying means on the yacht to direct the amplified upwash to the aft sail.

2. An apparatus as claimed in claim 1 , wherein the mounting means includes means for trimming the amplifying means.

3. An apparatus as claimed in claim 2, wherein the amplifying means is a microairfoil.

4. An apparatus as claimed in claim 3, wherein the microairfoil includes a headsail having a leech, a luff, a foot, a clew, a head and a tack.

5. An apparatus as claimed in claim 4, wherein the mounting means includes means for connecting the clew of the headsail to the forward side of the mast near its base.

An apparatus as claimed in claim 5, wherein the mounting means includes means for connecting the head of the headsail to the forward side of the mast near its top.

An apparatus as claimed in claim 6, wherein the trimming means includes at least one of:

(a) means for applying tension to the foot of the headsail between the tack and the clew; and

(b) means for tacking the luff of the headsail laterally through an arc about an axis along its leech.

An apparatus as claimed in claim 7, wherein the trimming means includes a starboard sheet and a port sheet connectable to the tack and operable as at least one of tension means and tacking means.

An apparatus as claimed in claim 8, wherein the trimming means further includes a starboard turning block and a port turning block positionable on the yacht to respectively route the starboard sheet and the port sheet to operate as at least one of tension means and tacking means.

An apparatus as claimed in claim 8, wherein the tension means includes a pole having a forward end adapted for connection to the tack and an aft end adapted for connection to the mast.

1 1 . An apparatus as claimed in claim 10, wherein the pole is telescopic.

12. An apparatus as claimed in claim 10, wherein the pole includes a yoke towards its forward end, as the adaptation for connection to the tack.

13. An apparatus as claimed in claim 12, wherein the starboard sheet and the port sheet are connectable to the tack via the yoke.

14. An apparatus as claimed in claim 13, wherein the tension means further includes a downhaul adapted to connect the tack to the deck.

15. An apparatus as claimed in claim 14, wherein the downhaul is adapted to connect to the tack via the pole.

16. An apparatus as claimed in claim 15, wherein the downhaul is adapted to connect to the tack via the yoke.

17. An apparatus as claimed in claim 16, further including a track adapted to connect the downhaul to the deck.

18. An apparatus as claimed in claim 17, wherein the track has a geometric center close to the axis of the leech.

19. An apparatus as claimed in claim 13, wherein the tension means further includes an outhaul adapted to connect the tack to the forward end of the pole.

20. An apparatus as claimed in claim 19, wherein the outhaul is adapted to connect the tack to the forward end of the pole via the yoke.

21 . An apparatus as claimed in claim 4, wherein the luff has a bluff edge.

22. An apparatus as claimed in claim 4, wherein the amplifying means

includes fairing on the surface of the mast between the microairfoil and the aft sail.

23. An apparatus as claimed in claim 21 , wherein the amplifying means

includes sealing between the microairfoil and the mast.

24. A yacht having the apparatus of claim 4.

25. A method for affecting airflow adjacent an aft sail mounted on an aft side of a mast on a yacht, the mast also having a top and a base and a forward side opposite the aft side and the yacht having a deck, comprising:

(a) amplifying upwash of a micro-airflow component of the airflow; and

(b) directing the amplified upwash to the aft sail.

26. A method as claimed in claim 25, wherein directing includes at least one of mounting and trimming a microairfoil.

27. A method as claimed in claim 26, wherein directing includes at least one of mounting and trimming a headsail having a leech, a luff, a foot, a clew, a head and a tack.

28. A method as claimed in claim 27, wherein mounting a headsail includes at least one of:

(a) connecting the clew of the headsail to the forward side of the mast near its base; and

(b) connecting the head of the headsail to the forward side of the mast near its top.

29. A method as claimed in claim 28, wherein trimming a headsail includes at least one of:

(a) applying tension to the foot of the headsail between the tack and the clew; and

(b) tacking the luff of the headsail laterally through an arc about an axis along its leech.

30. A method as claimed in claim 29, wherein mounting a headsail includes connecting an aft end of a pole to the mast and connecting a forward end of the pole to the tack.

31 . A method as claimed in claim 30, wherein mounting a headsail includes yoking the forward end of the pole with a yoke and connecting the forward end of the pole to the tack via the yoke.

32. A method as claimed in claim 31 , wherein trimming a headsail includes connecting an outhaul between the yoke and the pole.

33. A method as claimed in claim 32, wherein trimming a headsail includes connecting a downhaul between the yoke and the deck.

34. A method as claimed in claim 26, wherein directing includes blending a surface of the mast between the microairfoil and the aft sail.

35. A method as claimed in claim 26, wherein directing includes sealing

between the microairfoil and the mast.

36. A new use for a headsail as a microairfoil for an aft sail.

37. A new use as in claim 36, wherein the head sail is used as a bluff leading edge for an aft sail.

38. A new use as claimed in claim 37, wherein the head sail is used to at least one of amplify upwash and deflect airflow to the aft sail.

39. A new use as claimed in claim 37, wherein the head sail is used to form an airfoil in combination with the aft sail.