Stowable semi-rigid wing sail system
Kind Code:

A wing sail for wind powered craft and of the type having semi rigid panels (10) which communicate at their base with an airfoil shaped boom (21). The semi rigid panels (10) of the wing sail can be bent along folding grooves (20) that are parallel to the boom (21). In addition, the semi rigid panels (10), and boom (21) of the wing sail are made of flexible materials so that they can be repeatedly bent without fracturing, perpendicular to the boom.

Abshier, Charles Allen (Edmonds, WA, US)
Application Number:
Publication Date:
Filing Date:
Primary Class:
International Classes:
B63H9/06; B63H9/10; (IPC1-7): B63H9/04
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Primary Examiner:
Attorney, Agent or Firm:
Charles, Allen Abshier (534 4Th Ave. So., Edmonds, WA, 98020, US)

I claim:

1. In a wing sail of the type comprising multiple flat bodies of material adjacent to and communicating with each other, the improvement wherein said bodies have a plurality of thinner sections.

2. The wing sail of claim 1 wherein said bodies of materials are composed of a noncrosslinked polyvinylchloride foam core that is sandwiched between sailcloth.

3. The wing sail of claim 2 wherein said sailcloth is composed of mylar.

4. The wing sail of claim 2 wherein said sailcloth is composed of dacron.

5. The wing sail of claim 2 wherein said sailcloth is composed of spectra.

6. The wing sail of claim 2 wherein said sailcloth is composed of nylon.

7. The wing sail of claim 2 wherein said sailcloth is composed of kevlar.

8. The wing sail of claim 1 wherein said bodies of material are elongated, and said foam cores have multiple parallel grooves that are perpendicular to the elongation.

9. The wing sail of claim 1 wherein said multiple parallel grooves extend from one edge to the other edge of each of the bodies of material.

10. The wing sail of claim 1 wherein said bodies are joined together at one end of every other one of said grooves.

11. The wing sail of claim 1 wherein said bodies fold in where said grooves are joined.

12. The wing sail of claim 1 wherein said bodies fold out where said grooves are not joined.

13. The wing sail of claim 1 wherein said bodies whereby said grooves fold to substantially smaller bodies.

14. The wing sail of claim 1 wherein the bottom of said bodies are attached to a boom.

15. The wing sail of claim 1 wherein said boom is parallel to said grooves.

16. The wing sail of claim 1 wherein said boom is composed of wood.

17. The wing sail of claim 1 wherein said boom is composed of fiber reinforced plastic.

18. The wing sail of claim 1 wherein said boom is composed of aluminum.

19. The wing sail of claim 1 wherein said boom is composed of carbon fiber.

20. The wing sail of claim 1 wherein said boom is composed of epoxy laminated material.



[0001] This application is entitled to the benefit of Provisional Patent Application Ser. No. 60/191,854, filed Mar. 24, 2000.


[0002] 1. Field of the Invention

[0003] The invention herein referred to by its trademark name a “Sto-Wing”, relates to sails, specifically wing sails for wind powered craft.

[0004] 1. Description of the Prior Art

[0005] Designers and manufacturers of wind powered craft, supply consumers with a number of custom sails for a specific sailing craft. Sail designers and sailmakers provide the most efficient designs possible for the current technology. Racing and cruising sailors are the impetus for product development, toward more power, simplicity of use, and safety.

[0006] Sails with the most power are not easy to use, and are not safe to use with possible

[0007] Designers and manufacturers of wind powered craft, supply consumers with a number of custom sails for specific sailing craft. Sail designers and sailmakers provide the most efficient designs possible for the current technology. Racing and cruising sailors are the impetus for product development, toward more power, simplicity of use, and safety.

[0008] Sails with the most power are not easy to use, and are not safe to use with possible high winds. The most common sails are not easy to use, and suffer a loss of efficient use of the winds power of up to thirty seven percent. Even in the hands of professionals, sail trim requires a lot of attention, and handling to keep the power of the wind working for the craft.

[0009] (a) Rigid Wings;

[0010] For the wind powered craft, it has been a long held claim, that the solid wing with flaps and headsail twist, is the one hundred percent efficient use of the winds power. An example is “Patient Lady” by Dave Hubbard and Tony DiMauro in 1974, reference; Faster Faster The Quest For Sailing Speed, page 61, by David Pelly, 1984 Hearst Marine Books. However, solid wings come short of this claim. For airfoil shape control, solid wings have huge flaps. These wings require a substantial amount of adjustment. An airfoils efficiency is in direct proportion to its' draft to chord ratio, which must change with increased, or decreased wind speeds automatically. Solid wings are not flexible enough to change draft, or flatten the windward panel automatically. Rigid wings have a substantial reduction of useful efficiency, as they cannot be stowed, and the whole wing must be hauled out for possible high wind speeds. Additional sails are required for all useable wind conditions, and the craft cannot stow away a spare wing.

[0011] (b) Wing Masts with Sails;

[0012] Compromises between solid wing, and standard sail have been made, in efforts to improve efficiency and safety for everyday use. An example is the “Lady Helmsman” by Austin Farrar in 1965, reference; Faster Faster The Quest For Sailing Speed, page 56, by David Pelly, 1984, Hearst Marine Books. The rotating partial solid wing mast, with a fully battened mainsail improves efficiency over that of standard sails. However, safety for the craft is compromised by storm winds, and by the increased weight affecting the righting moment.

[0013] Also, as with standard sails, the airfoil shape is not automatic, and is complex to adjust. Additional sails are required for all useable wind conditions.

[0014] (c) Bluey Rig, 1975, by George Chapman, reference; Faster Faster The Quest For Sailing Speed, 1984, Hearst Marine Books A collapsible wing mast of framed panels that slide up or down the mast, with a soft sleeve sail sewn over these frames. The rig has a single trailing edge sail panel for tacking. With wind applied to the soft sail, the sail jams the sail between the frames when reefing. Also, this soft sail is not an efficient rigid wing sail.

[0015] (d) Ljundstrom Rig, Swedish, patented in 1938, reference; Singlehanded Sailing 2nd Edition, by Richard Henderson, 1988, International Marine Publishing Company. A boomless, battenless, soft twin sail that stows wound up around a rotating mast, and can be spread apart for following winds. On the wind, the mast forms the leading edge inside the twin sails. When reefed, the rolled up dual panels become the same as a standard single sail panel, which is an inefficient airfoil shape.

[0016] (e) Lapwing Rig, by H.G. Hasler, around 1960, reference; Singlehanded Sailing 2nd Edition, 1988 International Marine Publishing Company. A “Modified Ljundstrom rig”, added twin booms. For following winds, the clew of the twin booms can be separated, allowing the sail panels to wing out, and form a following wind sail. The boom is an improvement, but the airfoil remains as inefficient as standard soft sails.

[0017] (f) Gallant Rig, by Jack Manners Spencer, of England, reference; Singlehanded Sailing 2nd Edition, 1988, International Marine Publishing Company. A fully battened soft twin sail, enveloping the mast. Stows horizontally. Like the “Bluey Rig” above, this sail is also soft, and inefficient. The battens make it difficult to adjust the airfoil shape from head to foot.

[0018] (g) N.A.C.A. 653-418 wing section, by John H. Quinn Jr., 1944, wing section with boundary layer control by suction through a spanwise slot at the point of separated flow in the leeward surface. Reference; Theory Of Wing Sections, Abbott and Doenhoff, 1959, Dover Publications. Suction is provided by a mechanical pump. The solid wing section as described is a one direction lifting airfoil. Intended for, and suitable only for “heavy displacement aircraft”.

[0019] (h) Standard Sails;

[0020] Airfoils of single panel sailcloth suffer a substantial loss of efficient use of the winds power. Which can be as much as a 17 to 37% loss of efficiency. Many changes of sails are required for different wind conditions. Also they require constant adjusting to control their airfoil shape. With a shaped mast there is only a slight increase in efficiency. This efficiency is increased slightly more with the masts ability to rotate its leading edge toward the wind.

[0021] Standard sails are the most widely used, whether for working, sport, or pleasure craft. These sails are inefficient, and are not safe to use, because they are not easy to change. Rapidly degrading weather can ruin the sails, and inflict serious injury to persons handling them. To reduce the danger of handling sails away from the safety of the cockpit, roller reefing systems were introduced, reference; Ted Hoods' patented swivel. However, the sails made for roller reefing systems are soft, and do not hold their airfoil shape sufficiently.


[0022] In accordance with the present invention a Sto-Wing comprises “dual semi-rigid sail panels” that furl (unfold) or reef (fold down), has an automatic draft (thickness of wing) adjusting boom that bends to the shape of a wing or opens as a spinnaker sail. Wing sail shape is comprised of “smooth laminated lightweight cored” sail panels, with shape control springlines, twin booms, and spare sail pockets.

Objects and Advantages

[0023] Accordingly, several objects and advantages of the present invention are:

[0024] (a) to provide a rigid wing sail for a multitude of different wind powered craft.

[0025] (b) to provide a rigid wing sail that is one hundred percent efficient in its use of the winds power.

[0026] (c) to provide a rigid wing sail that folds up or down to a desired setting.

[0027] (d) to provide a rigid wing that is flexible enough to bend to a desired shape.

[0028] (e) to provide a rigid wing sail that easily adjusts its shape to the optimum setting for deriving the most power from the wind.

[0029] (f) to provide a rigid wing sail that stows its spare panels, freeing up space normally taken by spare bags of sails.

[0030] (g) to provide a rigid wing sail that automatically adjusts wing chord draft.

[0031] (h) to provide a rigid wing sail that automatically sets as a wing sail, or spinnaker sail to the direction of the wind.

[0032] (i) to provide a rigid wing sail that is lightweight enough to replace existing sail systems.

[0033] (j) to provide a rigid wing sail that is lower in cost than other standard sail systems' entire suits of sails.

[0034] (k) to provide a rigid wing sail that is safer for everyday use.

[0035] (l) to provide a rigid wing sail that as a single system, can be used as a source of power for sailing craft, in all but the most intolerable wind strengths.

[0036] (m) to provide a rigid wing sail that has a higher lift to drag ratio for sailing closer to the upwind direction.

[0037] (n) to provide a rigid wing sail that balances the sail across the mast for easier operation, and less strain on the sail handling gear.

[0038] (o) to provide a rigid wing sail with a center of effort that is placed forward to be compatible with existing mast locations of sailing craft.

[0039] Further objects and advantages are to provide a rigid wing sail that with its improved efficiency, has a lowered designed height, which lowers the centers of both effort and gravity. Thereby, providing the wind powered craft with a higher righting moment. Additionally, causing less heeling of the craft, which further improves efficiency by standing the sail up for less airflow to spill off.

[0040] Still further objects and advantages will become apparent from a consideration of the ensuing description and drawings.


[0041] In the drawings, closely related figures have the same number but different alphabetic suffixes. Extra drawings without lead lines are supplied to delineate details.

[0042] FIG. 1 shows a side view of a laminated panel with peeled back layers.

[0043] FIGS. 1A and 1B show side views of sail panels with foam core sections.

[0044] Detail FIG. 1C shows detail view of FIG. 1B leach with sailcloth peeled back.

[0045] FIG. 2 shows a forward perspective view of a Sto-Wing.

[0046] FIG. 2A shows side view of a gaff rigged wing sail.

[0047] FIG. 2B shows side view of a square rigged wing sail opened as a spinnaker sail.

[0048] FIG. 2C shows a side view of a Chinese lug rigged wing sail.

[0049] FIG. 2D shows a side view of a Bermudan rigged wing sail.

[0050] FIG. 3 shows a cross sectional view of an outside fold at full draft with slots.

[0051] FIG. 3A shows a view of FIG. 3 in an alternate movement with airflow applied to the forward left.

[0052] FIG. 3B shows a view of FIG. 3 in an alternate movement with airflow applied from behind.

[0053] FIG. 4 shows a vertical cross section view through a downhaul position of a panel.

[0054] Detail FIG. 4A shows detail view of FIG. 4 with a jammed downhaul line at an inside fold.

[0055] Detail FIG. 4B shows detail view of FIG. 4 with a jammed downhaul line at a reef position.

[0056] Detail FIG. 4C shows detail view of FIG. 4 with a freed downhaul line at the boom.

[0057] FIG. 5 shows a cross sectional view of wing sail inside fold with shape control springlines.

[0058] FIG. 5A shows a cross sectional view of spinnaker sail as an alternate movement of FIG. 5.

[0059] FIG. 6 shows a perspective view of a mast section with attached foreboom, foreboom brace, and extending boom with eyebolt.

[0060] FIG. 6A shows FIG. 6 with addition of spinnaker and draft arms attached with pins.

[0061] FIG. 6B shows FIG. 6A with addition of full draft booms attached by pins and coil springs.

[0062] FIG. 6C shows a top view of full draft boom of FIG. 6B.

[0063] FIG. 6D shows a top view of minimum draft boom, alternate movement of FIG. 6C.

[0064] FIG. 6E shows a top view of spinnaker sail boom, alternate movement of FIG. 6C.

[0065] FIG. 6F shows a view of FIG. 6F with alternate foreboom and brace goosenecks fitted to bands.

[0066] FIG. 7 shows a side view of interior of port panel.

[0067] FIGS. 7A through 7I show cross sectional views of wing interior.

[0068] FIG. 8 shows a side view of starboard side of wing.

[0069] FIG. 8A shows an end view from back of wing.

[0070] FIG. 8B shows an end view from front of wing.

[0071] FIG. 8C shows a view from back of opened wing.

[0072] FIG. 8D shows a side view from starboard of opened wing.

[0073] Detail FIG. 8E shows detail of headboard roller.

[0074] FIG. 9 shows an end view from front of wing beginning to fold first panel

[0075] FIG. 9A shows an end view from front of wing with first panel halfway folded.

[0076] FIG. 9B shows an end view from front of wing with second panels beginning to fold.

[0077] FIG. 9C shows a view from front of wing with second panels halfway folded.

[0078] FIG. 9D shows a view of cross section of 9A.

[0079] FIG. 9E shows a view of cross section of 9C.

[0080] FIG. 9F shows a side view of a stowed wing sail. 1

Reference Numerals In Drawings
10 sail panel
11 foam core
12 sailcloth
13 panel section
14 core fold gap
15 full roach
16 inside fold
17 mast
18 clew
19 spinnaker sail
20 fold core cut
21 airfoil shaped boom
22 outside fold
23 low stall core cutout
24 concave depression
25 spanwise slot
26 slot overlap
27 luff
28 windward slot
29 leach
30 leeward slot
31 downhaul line
32 downhaul jam
33 grommet
34 shape control springline
35 extended leach tab
36 midchord reef ring
37 tack reef ring
38 tack grommet
39 reef hook
40 clew reef ring
41 halyard
42 sheave
43 spread luff
44 batten in sleeve
45 foreboom
46 boom
47 foreboom brace
48 extending boom
49 spinnaker arm
50 draft control arm
51 coil spring
52 boom eyebolt
53 tack
54 tack springline
55 boom padeye
56 guide hole
57 sail panel foot
58 screw
59 sheet
60 boom cap bail
61 reefhook release line
62 spare sail pocket
63 spare sail access flap
64 pocket clew loop
65 sail cover
66 sail cover lanyard
67 bolt pin
68 sailcloth peeled back
69 shackle
70 headboard roller
71 boom vang
72 forward padeye hole
73 foreboom slot
74 clear window
75 leeward surface
76 sprit boom
77 fixed foreboom band
78 fixed brace band
79 foreboom gooseneck
80 brace gooseneck
81 backer strip end
82 partial wing shape
83 headboard
84 sailcloth tabs


Drawing Sheets 1 thru 15—Preferred Embodiment

[0081] The Sto-Wings' semi rigid sail panels (FIG. 1) are produced with a thin foam core 11. The closed cell foam cores' material is a “noncrosslinked polyvinyl chloride foam”. The PVC foam core is known by its trademarked name as Airex, and is available from Torin Inc., 9 Industrial Park, Waldwick, N..J. 07463. The core has a memory shape characteristic, after bending it returns to its original shape. These sail panels' interior and exterior surfaces are laminates of “lightweight sailmakers' materials” 12. The laminated sailcloth provides a smooth, durable surface, that is ultraviolet protection for the core. The strength of the individual panel materials is increased substantially by lamination. This allows the decrease in the thickness and weight of the materials, required for the strength of this wing sail panel. The manufacture (lofting) of the sail panels is accomplished with the use of laminating adhesive. The major change in the process of lofting the Sto-Wing panels, from standard sail lofting, is the addition of foam core.

[0082] Major sail rigging manufacturers such as Hood StoWay Yachtspars, Portsmouth, R.I., or sail manufacturers such as North Sails, San Diego, Calif., can supply the materials, and specific technical expertise required for lofting these sails.

[0083] The Sto-Wings' whole sail panels 10 are lofted with the core being, “multiple horizontal panel sections” 13. The core panel sections are spaced with a small gap, or groove between their top and bottom edges 14. This is for the sail panels to fold where they are gapped. The sail panels are made of two vertical sections (FIGS. 1A and 1B). The vertical trailing section (FIG. 1B) overlaps the exterior of the verticle leading edge section (FIG. 1A), and they are stitched together at their inside folds 16.

[0084] The Sto-Wing, is formed of “inversely twin sail panels”. The best outline shape of the Sto-Wing, would be “round headed full roach” (FIG. 2) 15. However, it can be designed aesthetically, to replace any of the more traditional outline shapes. Such as, the Gaff rig (FIG. 2A), the Square sail rig (FIG. 2B), the Chinese lug rig (FIG. 2C), and the Bermudan rig (FIG. 2D). This would increase the efficient use of the winds power for those shapes.

[0085] The Sto-Wing is assembled, by attaching the foot of the sail panels 57 with a backer strip 47, and screws 58 to their respective sides of the boom 46. The backer strip extends from the clew of the booms, to a point close to the tack of the booms 81. The backer strips not continuing to the tack, is to facilitate the folding of the foot panels at the tack, as the panels need to unbend and rebend, to fold down. Next, the leading edges of the sail panels are joined together, with the shape control springlines 34, (FIG. 5) at the inside folds' 16 leading edge grommets 33. Then by hoisting the sail panels with the halyard 41 from the “airfoil shaped boom” 21, a wing sail is formed surrounding the mast 17 as a backbone. The boom parts the sail panels at the clews 18 (FIG. 6E), forming a spinnaker sail 19 in front of the mast (FIG. 8D). The “rounded head shape” of the wing sail panels, have an additional advantage for its selection in the preferred embodiment. The “rounded full roach” forms a “spinnaker sail shape”, with the dual panels parted (FIG. 8C).

[0086] A significant improvement over other wing sails, is the Sto-Wings' ability to reef (fold down) its panels easily. To facilitate this, the foam core, is cut, thinned or voided at the bottom of each panel section (Figs. 1A, 1B,) 20, that folds down. Which is the upper panel of two panel sections making an inside fold 16. The shape of this cut is an upward cambered curve close to the shape of the full draft boom 82 (FIGS. 9D, 9E). This softer panel area eases the folding of the “cambered rigid panels”, over the booms' airfoil shape 21.

[0087] Another softer panel section also aids in the folding down of the rigid panels, the foam core is cutout, or thinned 23 (FIGS. 1B, 1C) in half elliptical shapes.

[0088] The soft panel side section is along the outside fold 22 cross section area, beginning at the midchord section of the wing sail panel area, to the trailing edge.

[0089] An additional purpose for this core thinning, is to form a windward concave depression 24 (FIG. 3A). This speeds up the flow of wind leaving the windward side of the wing sail. Which essentially, creates a wing with a lower stall speed.

[0090] Each of the Sto-Wings' sail panels have a spanwise slot 25 (FIG. 2) at forty five percent abaft the leading edge. The trailing part of the sail panel, overlaps the leading part of the sail panel at these slots (FIGS. 3, 3A, 3B) 26. The slots are joined together at every inside fold (FIG. 5). The outside fold is allowed to expand the slot by the force of the airflow on it (FIGS. 3, 3A). The slots remove an amount of air equal to the disturbed boundary layer, at the same rate of speed as the air is flowing. On either tack, the wing sail panels' slots function alike. In aerodynamic terms, the slots are referred to as a “high lift device”. (In reference to the NACA 653-418 wing section with boundary layer control by suction slot, “Theory Of Wing Sections”, page 236, Abbott, and Doenhoff, Dover Publications, 1959).

[0091] The port and starboard sail panels fold simultaneously. The Sto-Wing remains an airfoil in use when raising or stowing the panels (FIGS. 9, 9A). This is for optimum performance while changing the amount of sail area exposed to the wind. The Sto-Wings downhaul lines (FIG. 4) 31, extend from their attachment at the headboard 83, through downhaul jams 32 and the boom padeye 55 guidehole 56, to the cockpit of the craft. The downhaul line material is a low stretch polyester (rope). The downhaul jams keep the upper panels in flat sections by being clutched in downhaul jams 32 (FIG. 4A). The downhaul jams are sailcloth tabs 84, with two grommets 33, and are located at each inside folds' midsection (FIGS. 5A, and 7A thru 7G). The grommets 33 of the jam are misaligned to grip the downhaul line (FIG. 4B). The grommets release the downhaul line upon reaching the boom, by becoming aligned (FIG. 4C). The two part sail panel section above the freed line is then allowed to fold down. The grommets' material can be brass, stainless steel, neoprene rubber, or nylon.

[0092] Shape control springlines 34 (FIGS. 5, 5A, and FIGS. 7A thru 7G) are located horizontally along each of the inside fold sections of the sail panels. They bend the sail panels' draft outward, and the leading edges (luff) in an elliptical shape, and are the adjustment for camber of the sail panels. The shape control springline is attached to the “foam cored extended leach tab” 35, and led through the midchord reef ring 36. From the midchord ring the line is led through the tack reef ring 37, and threaded through a grommet 38 at the luff of both sail panels (FIG. 2). The line is then led through the reef rings of the other panel, to its extended leach tab. The springline keeps the dual panels leading edges in line with, and close to each other. The cambered tack 53 at the foot of the sail panel, which needs to straighten out for reefing, is secured with a shorter springline 54 from the boom midsection padeye 72. The downhaul jams are held out in tension by these springlines. At reefing positions, the springlines are run through the reef rings, for their alignment with reef hooks 39. The reef rings hold their downhaul jams out in tension (FIG. 7G). The extended leach tab is for tensioning the clew reef rings 40 for alignment with their reef hooks, and to keep from bending too much camber in the flexible trailing area of wing sail panel.

[0093] The head of both Sto-Wing sail panels are joined together abaft the mast by a shackle 69 to dual halyards 41. Between the sail panels heads, there is a headboard roller 70 (Detail FIG. 8E), which reduces the friction of the shackle against the mast. The shackle 69, attaches the head of the panels on each side of the roller. The halyards are led about the mast port and starboard, from sheaves 42 in the fore of the mast.

[0094] The head of the sail panels are battened 44 (FIG. 1A) to hold the rounded roach shape out fore, and aft of the mast to extend the catenary lines (lines of force between the boom and head of sail) . This places the foreward catenary line of force close to the leading edge of the wing sail. Which makes the luff (leading edge) more rigid, in its hoisted tension from the boom.

[0095] The Sto-Wing requires a freestanding spar (mast) 17 for its operation. This is to eliminate the complexity of the design, that would be needed to work around standing rigging and spreaders.

[0096] The Sto-Wing panels enclose the mast as a backbone, and their alignment across the mast is balanced for easier, and safer handling of the wing sail system.

[0097] At full draft, the mast is situated abaft the leading edge, at forty percent of the wing sails' chord. Which, for light winds, the leverage of the sail panels' trailing section to the forward section is, one and a half times (FIGS. 6C, and 7I). At minimum draft, the mast is situated abaft the leading edge, at thirty percent of the wing sails' chord (FIG. 6D). Which, for higher winds, the leverage of the sail panels' trailing section to the forward section is, two and a third times.

[0098] Additionally, the wing sails' forward position places its' center of effort closer to the location for which an existing mast, was designed for on most sailing craft.

[0099] The Sto-Wing has a foreboom 45 (FIG. 6), that swings about in front of the mast. For the foreboom to be installed on a sailing craft with a fully rotating mast, the foreboom is attached with screws 58, as shown in (FIG. 6). For the foreboom to be installed on a craft with a nonrotating mast, the fixed foreboom band 77, and brace band 78 (FIGS. 6F) are attached with screws 58 to the mast. The foreboom and foreboom brace gooseneck fittings 79 and 80, are attached to the fixed foreboom bands with pins 67.

[0100] The twin flexible booms 46 (FIG. 6B ) are jointed to swing backward in the form a wing, or open as the shape of the foot of a spinnaker (FIG. 6E). The booms' jointed forward ends are mounted with a pin 67, to the end of an extending boom 48 that slides fore and aft in the foreboom 45. The extension boom has a lengthwise slot 73 (FIG. 6) in its top surface, that, in communication with an eyebolt 52 in the top of the foreboom, keeps the extension boom from sliding out of the foreboom. The booms form the sail panels into an elliptical leading edge when bent backward into an airfoil shape. At the wing sails widest draft, the booms are supported off of the foreboom, port and starboard, by articulated control arms (FIG. 6A), which consist of the spinnaker extension arms 49 that are jointed off of each side of the forebooms' forward end, and the draft control arms 50 that are jointed off of the spinnaker extension arms. The draft control arms ends are jointed to the booms' 46 (FIG. 6B) padeyes 55, and all the joints are secured with pins 67.

[0101] Coil springs 51 are connected between the booms' padeyes 55, and the forebooms' eyebolt 52. The coil springs are the tension for joining the booms together in a wing shape, and for keeping the extending boom, and draft control booms forward. The spinnaker setting is the strongest tension on the springs (FIG. 6E), and the least tension is the full draft wing shape (FIG. 6C). Additionally, the booms are formed in the full draft shape, to provide springability against the minimum draft shape (FIG. 6D). Therefore, less airflow is required to open the spinnaker, than to reduce the draft of the wing. Because the airfoil presents less area to the airflow, when used in a wing shape, than it does as a spinnaker shape.

[0102] The materials for the moving parts of the boom can be aluminum, steel, carbon fiber, or fiber reinforced plastic. Materials for parts change with the size of the sail, and mounting structure, for a particular size of sailing craft. The coil springs are steel, and the booms are wood, laminated wood, carbon fiber, or fiber reinforced plastic. The springlines are bungee cords.

[0103] A padeye 55 (FIG. 6B) is mounted on the inside of each boom, port and starboard, at forty percent abaft the leading edge. The padeyes are for jointed attachment of the draft adjust control arms. A guide hole 56 in each padeye, is for the downhaul lines to correctly align the sail panels as they are folded down. The padeye has a hole 72 at its forward end, and is for the connection of the tack springline 54 (FIG. 7H), and for hooking of the coil spring. Also, the midsection reef hooks are attached to the after end of these padeyes, to align them with the reef rings.

[0104] The possibility of breaking one of the booms when in the spinnaker sail setting, is eliminated with boom vang lines 71 (FIG. 6E), which limit the boom ends from lifting, or bending too far. Each vang line is attached from its respective boom cap bail 60, to the foreboom bottom brace (FIG. 6) 47. Thereby, making it possible to use the spinnaker sail without sheets at the clews.

[0105] Located along the inside of the booms are reef hooks 39 that, hook on reef rings attached to the sail panels midsection downhaul jams 36, and on reef rings at the tack 37, and clew 40. A spring loaded line (FIG. 8C) 61 keeps all reef hooks fastened, the opposite end of that line is led to the cockpit for releasing the hooks.

[0106] Attached below each boom, a pocket of sailcloth 62 (FIGS. 2, 4) is for stowage of spare folded sail panels. The folded rigid panels would not be handily stowed elsewhere. The twin stowage pockets are joined together at their leading edges. The spare sail stowage pockets increase the total sail area, and the booms uni-lateral strength.

[0107] A dual panel sail cover (FIGS. 2, 4) 65, when not protecting the stowed sail folds down. The cover closes the opening at the foot of the wing sail, to prevent over ventilating the interior of the wing sail. The lashed panels of the cover 66 round the foot of the wing sails' leading and trailing edges, for a decrease of induced drag. The cover has a batten 44 in each of its fabric panels at their leading and trailing edges, which keeps the covers shaped.

[0108] Different sized wing sails require different strengths of materials, which translates to different weights of materials. The following is an example of the lightweight characteristics of a medium aspect ratio (span to chord ratio), eight meter high Sto-Wing;

[0109] The foam core at the head of the sail panels for this example, is a nine pound per cubic foot density, the midsection sail panels are six pound density, and half of the total sail area; toward the foot sections are four pound density. The softer sections are not cored thinner, they are voided of core material. Because of the core voids, this sail panels area is fifty five percent cored, at 3.25 mm. thick. The spanwise slots, luff (leading edge), and leach (trailing edge) of the sail panels have extra reinforcing with a highly oriented fiber material, such as trademarked spectra or kevlar.

[0110] With 9 pounds per cubic foot foam density, at the sail head sections, and laminates of 1.5 ounces of sailcloth on each side, these panel sections' weight is 8.87 ounces per sailmakers yard.

[0111] With 6 pounds per cubic foot foam density, at the mid-sail sections, and laminates of one ounce sailcloth on each side, this panel sections' weight is 5.91 ounces per sailmakers yard.

[0112] With 4 pounds per cubic foot foam density, at the lower sail panel sections, and laminates of half ounce sailcloth on each side, these panel sections' weight is 3.6 ounces per sailmakers yard.

[0113] Considering the reduced area of the head of the sail, the fold core reduction, and the three differently weighted sections, the average overall weight of the entire sail panel per square sailmakers yard is 3.98 ounces. Thus, the average overall weight of the Sto-Wing by multiplying the dual sail panels is, 7.96 ounces per square sailmakers yard.

[0114] The dual paneled Sto-Wing that replaces the main, jib, and spinnaker sails, is comparable in weight aloft to a regular single panel eight ounce mainsail. Therefore, with similar weight considerations, the Sto-Wing significantly increases power from the wind, for sailing craft. This includes the weight of dual panels having a fully rigid leading section, and fully battened trailing section with foam core.

[0115] The following is an industry rating of sails including the Sto-Wing, which is why it was not included in the “background—prior art” section of this application. The rated sails are of the same square meter area, and are battened.

[0116] Rating reference; The Cruising Catamaran Advantage, page 165, by Rod Gibbons, 1988, Island Educational Publishing. 2

Percent of Efficiency in Wind Power Use of Airfoils
Old RatingNew Rating
Of Sto-WingOf Sto-Wing
100% Rigid airfoil with flaps83%
94%Wing mast 40% of area.78%
83%Foresail without jib.69%
83%Shaped mast, rotating with jib.69%
82%Shaped mast, rotating without jib.68%
78%Round mast, rotating with, or w/out jib.64%
73%Shaped mast, non-rotating with jib.59%
71%Round mast, non-rotating with jib.57%
65%Shaped mast, non-rotating without jib.51%
63%Round mast, non rotating without jib.49%

[0117] The Sto-Wing is a significant improvement over all other airfoils for wind powered craft, with its reefing ability, multiple sail shape settings, automatic draft adjustment, drag reductions, and high lift devices. Thus, all useable wind conditions can be utilized for one hundred percent efficient use of the winds power.

[0118] Although other airfoils for wind powered craft have an increased efficiency over standard sails by 17 to 37%, the Sto-Wing is 31 to 51% more efficient than standard sails.

[0119] Additional embodiments are shown in (FIGS. 2A, 2B, 2C, and 2D); in each case the slots, panel folding, downhauls, shape control lines, and boom arrangement with its automatic draft adjustment, and parting into a spinnaker sail, are typical of the preffered embodiment.

[0120] A gaff rig (FIG. 2A) wing sail is shown in its wing sail shape by the use of dual sprit booms 76 at the head of the sail.

[0121] A square rig (FIG. 2B) wing sail is shown in its spinnaker sail shape by the use of dual sprit booms 76 at the head of the sail. The foam cores are omitted in a cambered shape 74, representing the space between square sails. Clear MYLAR is laminated on each side of a SPECTRA webbing, in these core omission sections.

[0122] A Chinese lug rig (FIG. 2C) wing sail is shown in its wing sail shape by use of dual sprit booms 76 at the head of the sail.

[0123] A Burmudan rig (FIG. 2D) wing sail is shown in its wing sail shape with the foot boom arrangement angled over the stowage pockets, to facilitate easier folding of the panels.

[0124] The Sto-Wing is a significant improvement over all other wings and sails, in its abilities for easy, and safe operation;

[0125] (a) the dual wing panels fold down easily for reefing, or stowing.

[0126] (b) all sail trimming can be handled from the safety of the cockpit.

[0127] (c) when tacking, the booms movement is controlled by the mast brake.

[0128] (d) the spinnaker set sail has a five point hitch at its foot, keeping the sail under control.

[0129] (e) increased efficiency has less sail area exposed to the wind, which reduces the risk of knockdown by sudden strong bursts of wind.

[0130] (f) the efficiency of design, increases the righting arm, and lowers the centers of both gravity and effort, for less heeling of the craft.

[0131] (g) the foam cored panels float, in case of heavy weather knockdown, which will help prevent rollover on sailboats.

[0132] (h) the wing sail setting can point closer to the upwind direction, thus making fewer tacks with the wing sail, for the sailing craft to arrive at a desired location.

[0133] The Sto-Wing reduces a higher percentage of drag vortices than other airfoils, and increases lifting power of the wing sail system by several measures;

[0134] (a) the fair cambered, and smooth semi rigid panels, improve boundary layer flow at all sail shape settings.

[0135] (b) the spanwise midchord slots, combined with the wing sail settings luff and leach slots, further improve boundary layer flow by suction through the leeward slot.

[0136] (c) the vertical drag vortice downwind of the wing sail is reduced by the flow out the leach.

[0137] (d) the slots also improve airflow for the spinnaker set sail.

[0138] (e) the softer trailing section of the wing sail, speeds up the windward trailing edge flow of wind, thereby, reducing vertical drag vortice, making the wing sail a “low stall speed” wing.

[0139] (f) the boom automatically adjusts the draft of the wing sail set semi rigid panels to changing wind speeds.

[0140] (g) the rounded full roach head of the sail reduces induced drag at the head of the sail.

[0141] (h) the continuous flexible trailing edge without flaps, which reduce induced drag.

[0142] (i) the boomed spare panel stowage, and sail cover configuration, of less induced drag around the foot of the wing sail.

[0143] (j) the bottom panels fold one at a time, while the remaining airfoil exposed to the wind retains a desired airfoil shape.

[0144] From the description above, a number of advantages of my stowable semi rigid wing sail system become evident.


[0145] The manner of using the Sto-Wing as a sail for wind powered craft, is similar to the operation of other sail powered systems.

[0146] All Sto-Wing sail system settings can be easily, and safely singlehanded from the cockpit. For the Sto-Wing to be one airfoil for all useable wind conditions, there are half as many running rigging lines as other sail powered configurations.

[0147] The Sto-Wings' running rigging consists of two halyards 41 for raising sail, which also control headsail twist. There is one line that releases the spring loaded reef hooks 61. There are two downhaul lines 31, one for each sail panel. There are two sheets 59, which are control lines for the dual clews 18.

[0148] Sheets (FIG. 6E) 59 port and starboard, are attached to their respective sail panels clew 18 at their boom cap bail 60, and are then led through deck blocks to the cockpit. (The sheets, deck blocks, and rotating mast brake would come as existing hardware with the sailing craft of this preferred embodiment). The sheets are used to haul the Sto-Wing around for selecting the attack angle of the wind. Attack angles of both the wing, and spinnaker sail are set by the rotating mast brake, with an operating line to the cockpit.

[0149] To ready the Sto-Wing for sailing, (FIG. 9F) the sail cover 65 is untied and dropped down over the spare sail pockets 62. Then retying the lanyards 66 of the sail covers edge in front of the mast, and leaving the lanyards untied behind the mast (FIG. 2), adds a rounded shape to the bottom of the sail.

[0150] To raise the Sto-Wing, one simply hauls the sail up the mast by one or both halyards 41.

[0151] With the boom in a wing sail configuration, and the attack angle set. Tightening the leeward sheet, with the aid of airflow upon the windward panel (FIG. 3A), a desired camber is bent into the panels due to the flexibility of the booms and sail panels.

[0152] By the coil springs 51 (FIG. 6C) pulling the booms together into a wing shape 21, the stowed sail will remain in that position, with up to moderate airflow applied from any direction. To fully stow the wing sail, the sail cover 65 must be lashed across the top of the sail (FIG. 9F). With the wing sail raised, airflow from behind will part the panels, and open the sail to a spinnaker shape (FIG. 3B, 5A, 6E). With airflow removed from behind the spinnaker, the panels will fold back into a wing sail (FIG. 2). As one sail panel 10 is moved by the airflow in a direction, the other sail panel will follow suit, because of the booms 46 connection to the extending boom 48, and articulating arms 49 and 50.

[0153] As the Sto-Wing automatically adjusts draft, the sheeted camber of the airfoil remains the same, with the sheet led close to a ninety degree angle to the boom.

[0154] The Sto-Wings boom adjusts the draft of the wing sail setting automatically to the incedence of the winds speed. Automatic draft adjustment occurs by the booms' springability forcing the draft control arms outward (FIG. 6C), and with increased wind and drag on the wing sail, the sail panels and booms move the extending boom backward, forcing the hinged draft control arms to swing the booms' draft inward (FIG. 6D). Thereby decreasing the wing sails draft to a flatter wing sail. As the wind decreases, the coil springs, and springability of the boom, pull the draft arms forward returning the wing sail to full draft. The head of the sail panels remain flatter for their higher wind speeds, and the other sections of sail panel follow the shape of the boom.

[0155] To change the Sto-Wing from a wing sail to a spinnaker sail from the cockpit. Haul the windward panel over with its sheet, while turning the craft to catch the wind from behind, and trim the attack angle, and sheets for a well shaped spinnaker sail.

[0156] The foot of the spinnaker sail setting, is at the full extension of the forebooms' extending boom. Along with the fully extended articulated control arms, and the sheeted spinnaker clews. Thus, the foot of the spinnaker is under full control by a five point hitch. Which is important to avoid broaching the sailing craft.

[0157] To change the Sto-Wing from a spinnaker sail to a wing sail from the cockpit. Head the craft into the wind, and the separated panels will swing back together. Select the attack angle with the rotating mast brake. Trim the desired camber into the wing sail, with the sheet. Headsail twist is controlled by tensioning one, or the other halyard.

[0158] To reef the Sto-Wing, whether in the wing sail configuration, or as a spinnaker sail, haul in the downhauls, and slack off the halyards. When the desired reef position has reached the boom, pull the reef hook release line, and pull the last panel down tight. Release the reef line, and tighten the windward halyard for proper headsail twist, and panel rigidity. The last reef is the stiff cored, heavily reinforced head of the Sto-Wing sail.

[0159] The spare sail pockets are accessed by opening flaps 63 (FIG. 8C) at the clew. The hanked on sails in use, fold down over the stowage pockets when reefing. The sheets running through the pockets bottom clew corners 64, bend the stowage pockets toward the wind. Thus preventing air from flowing down past the foot of the sail.

[0160] Air flows into the Sto-Wing at the luff 27 (FIGS. 3A, 8B) and windward vertical slot 28 (FIGS. 3A, 8B), then exits between the dual panels' leach 29 (FIGS. 3A, 8A). The venturi effect causes air to suck into the wing sail at the leeward vertical slot 30. While I believe the venturi effect occurs because of the action of airflow within the Sto-Wing, I do not wish to be bound by this. The action of air entering at this area 30 of the wing sail, is the point of separated flow, which improves the boundary layer airflow along the leeward surface 75 of the wing sail. Thereby reducing turbulent boundary layer flow toward the trailing edge, which substantially improves lift. An additional improvement of the Sto-Wings efficiency, comes from the slots airflow, by the way of a medium airflow, exiting the airfoil between the trailing edges of the dual panels. Which reduces direct flow of higher pressure windward air, into the lower pressure of the leeward side. The three zones of airflow, combine further from the trailing edge than standard airfoils. Thus, substantially reducing the vertical drag vortice behind the wings trailing edge. This airfoil with slots has a maximum lift coeficient of 4.0, the same wing section without suction slots has a maximum lift coeficient of 1.5. Additionally, the spinnaker set Sto-Wing has substantially improved air flow, because of the slots (FIG. 3B) 25.

[0161] In moderate winds, with the mast brake setting the wing sail fore, and aft in line with the center of the craft, and with the sheets running loose, any point of sail will automatically set an efficient airfoil, with the exception of steering the craft directly into the wind.

[0162] For sailing up narrow passages against the wind, the wing sail will perform well enough without bending the boom, by simply heading the craft more toward the wind. With the mast brake loose, and allowing the wind to turn the wing sail toward an attack angle of the wind. Then setting the mast brake, and turning the craft away from the wind slightly. The windward panel will flatten, and the resulting shape of the wing sail will be effective for short tacks.

[0163] With a drastic change in the attack angle of the wind, the spinnaker set Sto-Wing, would reset as a wing sail, or become a reaching sail by loosening the mast brake.

[0164] For storm survival, when it is necessary to remove the Sto-Wing, and stow it on the deck, four pins need to be removed; first two draft control arm pins, and then two tack pins. To remove the Sto-Wing entirely, it is also necessary to remove the halyards and sheets.

[0165] For heavy weather knockdown, or loss of a sail panel, the closed cell foam cored sail panels float, when used for a water craft.

[0166] Accordingly, the reader will see that the stowable rigid wing sail system of this invention, can be used safely for wind powered craft, with increased speed of the craft, and that it adds convenience to a challenging task. Furthermore, the Sto-Wing sail panel has the additional advantages in that

[0167] it permits production for several different kinds of wind powered craft;

[0168] it provides a lower cost wing sail system for wind powered craft;

[0169] it provides the ability for stowing, or reefing of the rigid panels;

[0170] it provides a wing sail with automatic airfoil shape adjustment;

[0171] it provides a dual panel wing sail that does not substantially increase weight; and

[0172] it provides one hundred percent efficient use of the winds power.

[0173] In addition, the increased efficiency of this wing sail substantially lowers its designed height, and aspect ratio, to equal the same power achieved by standard wings or sails. Therefore, the Sto-Wing has lower centers of both gravity, and effort. Which translates to less heeling, and further improved efficiency by the wing sail standing up to the wind, for less airflow to spill off.

[0174] Although the description above contains many specifities, these should not be construed as limiting the scope of the invention, but as merely providing illustrations of some of the presently preferred embodiments of this invention. For example, there are various possibilities with regard to the relative disposition of sail panel construction, the boom arrangement, and the suspension of the sail;

[0175] The foam cores can be constructed with a different material, which would not have the qualities preferred. Also, the sail panels can be laminations of sailcloth, with no foam core.

[0176] The wing sail can be efficient without the high lift devices made into its panels.

[0177] The wing sail can fold all at once as accordian folds, by not having the downhauls with jams. Also, the sail panels can fold down without the core cutouts.

[0178] The foreboom can be attached to a nonrotating mast with a fixed gooseneck fitting, or a stay wire can replace the mast as the backbone of the wing, both would have extra sheets taking the place of the mast brake.

[0179] The mast or a stay can form the leading edge within the wing, and loose the automatic draft reduction, to be manual draft reduction.

[0180] The boom can be a single part that functions as a wraparound leaf spring etc.

[0181] Thus the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.