Abstract:
A sail system for a sailboat having a stayed, non-rotatable mast includes first and second booms, a single sail suspended from said masthead, the sail having a shape such that, with the vertical midline of the sail positioned along the mast, a generally triangular sail portion is formed on the port side of the sailboat and a second, symmetrical, sail portion is formed on the starboard side, both said starboard and port sail portions having substantial roach areas; and backstay means connected between said masthead and the stern portion of the sailboat to bend the masthead aft.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sail system for a sailing craft and, more particularly, to a sail system for a sailboat having a non-rotatable mast. 
     2. State of the Art 
     It is well known that the optimum size and shape of a sail for downwind sailing (i.e., sailing before the wind) is substantially different than the optimum sail shape for upward sailing (i.e., sailing against the wind). For downwind sailing, especially in light wind conditions, a craft of a given size can usually carry more sail area than in upwind sailing conditions. Accordingly, for downwind sailing in light wind conditions, many sailing craft utilize a headsail, some types which are referred to as spinnakers, which are attached in front of the mainsail. 
     One variation to the above-described prior art has been proposed in U.S. Pat. No. 2,107,303 to Ljungstrom. In that patent, the patentee suggests attaching two sails to a single mast so that, when sailing before the wind, the two sails stand out like a parachute sail and, when sailing upwind, the two sails can be doubled against one another to form an ordinary triangular sail. According to the patentee, the mast should be rotatable so that the sails can be rolled about the mast to selectively change the effective sail area depending upon wind conditions. (Sail adjustment of the effective sail area is often referred to as reefing.) Further, the patentee suggests that several generally vertical laths be mounted in the sail; the vertical orientation of the laths is critical to the ability to roll the sail upon the mast for reefing. 
     Another variation on the prior art attempting to obviate the need for headsails is proposed in U.S. Pat. No. 4,230,060 to McCoy. Similarly to Ljungstrom, the McCoy patent suggests attaching two sails to a mast and providing the mast with a rotation mechanism so that the two sails can be selectively reefed by rotating the mast. In the McCoy patent, the sails are without laths or battens which, apparently, would interfere with rotation of the mast for reefing. 
     Yet another sailing system utilizing two sails attached to a rotatable mast has been proposed in U.S. Pat. No. 4,367,688 to Godfrey. Godfrey suggests that a sailboat can be provided with twin booms, a doubled triangular sail and a rotatable mast to permit conventional sailing with both booms and sail sections on the same tack or with the booms spread, wind-like, to permit running before the wind or reaching. The rotatable mast suggested by Godfrey permits the sails to be reefed or furled by rotation of the mast. In the Godfrey patent, the sails are also without laths or battens. 
     In an article appearing in Cruising World in August 1984, pages 98 and 99, there is a report of a sailboat designed by Thomas Godfrey. According to the article, the sail system for the sailboat basically consists of an unstayed spar of tapered elliptical section and a two-ply, wrap-around sail that can be reefed or furled by rotating the spar i.e., the mast). A sailing craft is pictured in the article including the so-called two-ply, wrap-around sail. The pictured sail does not include laths or battens, and that the mast is unstayed. 
     In U.S. Pat. No. 4,474,126 to King, there is proposed a sailing rig for use on a sailboat comprising a sail formed in the shape of two approximately ellipsoidal portions mounted upon a mast rotatable about its vertical axis. The rotatable mast in the King patent is unstayed but is permanently curved near its top. According to the patentee, the sail system oprates such that, when the sailboat is close-hauled, the sail folds around the mast and when the sailboat runs before the wind, the sail unfolds and opens to fly free of the mast. Further, the patentee suggests that the roach curve can be supported by battens arranged in a suitable configuration. Still further, the patentee suggests that, when the sail is folded around the mast, the foot of the sail at its centerline can be attached to a down-haul line for tensioning the luff of the sail. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     A primary object of the present invention is to provide an improved sail system for a sailboat having a stayed, non-rotatable mast. 
     Another object of the present invention is to provide an improved sail system for a sailboat having a stayed, non-rotatable mast wherein the sail system provides substantially increased sail area for downwind sailing and reduced sail area with a generally elliptic planform for upwind sailing. 
     Yet another object of the present invention is to provide an improved sail system for a sailboat having a stayed, non-rotatable mast wherein the sail system provides substantially increased sail area for downwind sailing or reaching, and reducible sail area with a fully-battened, generally elliptic shape in planform for upwind sailing. 
     In accordance with the preceding objects, the present invention provides a sail system for a sailboat having a stayed mast, with one end non-rotatably mounted to the sailboat and tapering thereafter to a narrow masthead. The sail system comprises a pair of booms pivotably secured to the mast; a single sail suspended from the masthead and having a shape such that, with the midline of the sail positioned about the mast, a sail portion with a generally elliptic planform is formed on the port side of the sailboat and a symmetrical sail portion is formed on the starboard side, a plurality of battens mounted at spaced-apart locations in the starboard and port sail portions to provide curved shape to the sail portions; first outhaul means to attach the clew of the port sail portion to one of the booms and second outhaul means to attach the clew of the starboard sail portion to the other boom such that said midline of the sail can be held toward the mast; and means to independently control movement of the two booms; and backstay means connected between said masthead and the stern portion of the sailboat to bend the masthead aft. 
     In accordance with the preceding, an advantage of the present invention is the provision of an improved sail system for a sailboat having a stayed, non-rotatable mast. 
     Another advantage of the present invention is the provision of a sail system for a sailboat having a stayed, non-rotatable mast to provide substantially increased sail area for downwind sailing or reaching, and reduced sail area with a generally elliptic planform for upwind sailing. 
     Still another advantage of the present invention is the provision of an improved sail system for a sailboat having a stayed, non-rotatable mast wherein the sail system provides substantially increased sail area for downwind sailing and reducible sail area with a fully-battened, generally elliptic shape in planform for upwind sailing. 
    
    
     These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment which is illustrated in the various drawing figures. 
     IN THE DRAWINGS 
     FIG. 1 is a side view of a sailboat in an upwind sailing position and employing a sail system, shown in planform, according to the present invention. 
     FIG. 2 is a plan view taken in section along the line 2--2 in FIG. 1 for viewing in the direction of the arrows. 
     FIG. 3 is a plan view of the sailboat of FIG. 1 with the sail system of the present invention in a position for downwind sailing. 
     FIG. 4 is a pictorial view of a section of the mast and booms utilized with the sail system of the preceding drawings. 
     FIG. 5 is a pictorial view of the distal ends of the booms and an associated mechanism utilized with the sail system of the preceding drawings. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the embodiment shown in FIG. 1, a sailboat includes a hull 13, a single mast 15 fixedly secured to the hull 13, and a sail system generally designated by the number 17 fitted to the mast 15 and including a sail 19. The mast 15 is non-rotatably fixed to the hull 13 and tapers to a narrow masthead 16. In practice, a conventional halyard 18 is provided at the masthead 16 to hoist the sail 19 for securement at the masthead 16. The sail system 17 includes a backstay line 21 connected between the masthead 16 and the stern portion of the hull 13. An adjustment means, such as a block 22, is connected to selectively shorten the backstay 21 thereby to force the masthead 16 to bend aftward; in practice, the aftward arc of the mast is about ten percent of the total luff length. 
     The portion of the sail 19 shown in FIG. 1 has, generally speaking, an elliptic shape in planform. The foot 24 of the sail 19 is defined as the portion which extends from the mast 15 to the clew 27s. FIG. 1 further shows a main sheet 29 whose function is essentially conventional, as will be further described hereinafter. Still further, FIG. 1 shows a dashed straight line 24 drawn from the masthead of the sail 19 to the clew 27; this line represents the hypotenuse of the generally triangular sail shape. The portion 31 of the sail which extends aftward beyond the hypotenuse line is known as the roach, and the edge of the roach portion of the sail is known as the leech. 
     FIG. 1 further shows a plurality of battens 33a, 33b, 33c, etc., mounted to the sail 19 at spaced-apart locations to extend generally toward the mast 15. Because the battens 33a-f extend from the leech to the mast, the sail 19 is said to be fully battened. The battens are ordinarily fitted in narrow pockets (not shown), sewn to the surface of the sail 19. In practice, the battens 33a-f are placed under compression along their length so that, as shown in FIG. 2, the leading edge of the sail 19 (i.e., the luff portion) has a generally curved shape providing draft even in the absence of wind pressure. Such compression of the battens 33a-f is accomplished by means, for example, of conventional straps and buckles arranged at the roach ends of the batten pockets such that, when a strap is secured to a buckle, the associated batten is forced toward the mast 15 and takes on a curved shape. In practice, the draft can be enhanced by tapering the portion of the batten adjacent to the mast 15. 
     FIG. 1 also shows a boom 37s which is connected to the mast 15 to extend to a distal end near the clew 27p. The boom 37s is additionally supported near the mast 15 by a linkage 47s, commonly referred to as a vang. Also, FIG. 1 shows a downhaul system 39, comprising a pair of pulleys and interconnecting lines, to connect the foot or tack of the sail 19 to the base of the mast 15. 
     Only the starboard portion of the sail 19 is shown in FIG. 1; the port portion, which is symmetrical with the starboard portion and likewise fully battened, extends aftward from the port side of the mast 15 as shown in FIG. 2. FIG. 2 also shows a boom 37p which extends from the mast 15 to a clew 27p on the port portion of the sail 19. (Components on the port side of the sailboat are designated by the subscripts &#34;p&#34; and components that are associated with the starboard side are designated with the subscripts &#34;s&#34;.) Thus, as shown in FIG. 2, the spaced-apart port and starboard portions of the fully battened sail 19 provide a windlike shape when the sail is positioned for upwind sailing. 
     FIG. 3 shows the sail system 17 in a position for downwind sailing. In this condition, the booms 37p and 37s are pivoted apart to form a reflex angle relative to one another, and the sail 19 is entirely forward of the mast 15. FIG. 3 also shows a pivot means, generally designated by the number 50, which pivotly connects the booms 37p and 37s and vangs 47s and 47p to the mast 15; in practice, the mast 15 is stationary and non-rotating relative to the pivot means 50. Further, FIG. 3 shows sheets 43p and 43s connected between the stern portion of the hull 13 and the respective distal ends of the booms 37p and 37s. The sheet 43p is referred to as the port trimmer sheet, and the sheet 43s is referred to as the starboard trimmer sheet. The port and starboard trimmer sheets 43p and 43s are connected at a splitter mechanism 45. Also shown in FIG. 3 are starboard and port foreguys 46s and 46p, respectively, which are connected between the bow of the sailboat 13 and the respective starboard and port boom 37s and 37p. The purpose of the foreguys 46s and 46p is to allow respective booms 37s and 37p to be hauled forward to place the sail 19 in the open, downwind condition. 
     FIG. 4 shows details of the boom and vang pivot means 50, the vangs 47p and 47s. The boom pivot means 50 includes a collar-like member 51 having upper and lower spaced-apart tang plates 49a and 49b fixed about the collar 51 to extend horizontally outward to the port and starboard sides of the non-rotatable mast 15. In practice, the collar-like member 51 is mounted to the mast 15 at a location slightly below the foot of the sail 19 and is free to rotate about the mast. On the starboard side, a clevis 55s is pivotably fixed between the tang plates 49a and 49b by a generally vertical pivot pin 57s; likewise, on the port side, a clevis 55p is pivotally fixed between the tang plates 49a and 49b by a generally vertical pivot pin (not shown). The starboard boom 37s is pivotably connected between the legs of the clevis 55s by a generally horizontal pivot pin 59p and, likewise, the port boom 37p is pivotably connected between the ends of the clevis 55p by a generally horizontal pivot pin 59p. As so mounted, the booms 37p and 37s are free to rotate in both horizontal and vertical planes relative to the mast 15 and, in addition, the booms 37p and 37s are free to rotate about the mast with the collar-like member 51. 
     Referring still to FIG. 4, the vangs 47p and 47s are pivotably connected to the collar 51 by vang pivot means 48 located below boom pivot means generally designated 41. The vang pivot means 48 has upper and lower spaced-apart tang plates 63a and 63b, respectively, fixed to the collar-like member 51 to extend horizontally outward to the port and starboard sides of the mast 15. On the starboard side, a clevis 65s is pivotably fixed between the upper and lower tang members 63a and 63b by a generally vertical pivot pin 64s. The starboard vang 47s is pivotably mounted between the legs of the clevis 65s by a generally horizontal pivot pin 66s so that the vang is free to pivot in a vertical plane relative to the legs of the clevis. Likewise, on the port side, the port vang 47p is pivotably mounted between the legs of a pivotable clevis (not shown). As so mounted, the vangs 47p and 47s are free to pivot in horizontal and vertical planes, and are free to rotate about the mast 15 with the collar-like member 51. The opposite ends of the vangs 47s and 47p are connected to the respective boom 37s  and 37p by universal joints comprised, for example, of interconnected shackles 72s and 73s. 
     FIG. 5 shows one manner of attachment of the end of the boom 37s to the clew 27s. More particularly, FIG. 5 shows trimmer sheet 43s extending from a bail 84s through a block 85s fixed to the clew 27s. Further, trimmer sheet 43s extends through a block 86s mounted to a car 87s slidably mounted on a track 88s fixed to the boom 37s. As so attached, the clew 27s can move lengthwise of the boom 37s as the car 87s slides along the track 88s. Conventional means, not shown, can be provided to selectively position the cars 87s and 87p on respective tracks 88s and 88p on respective booms 37s and 37p. The trimmer sheet 43s is fitted through sheaves 89s and 91s so that the trimmer sheet 43s can be controlled from the cockpit of the sailboat hull 13. Together, the splitter sheets 43s and 43p determine the extent to which the starboard and port booms 37s and 37p are angularly separated from one another when foreguys 46s and 46p are in tension. 
     Further, FIG. 5 shows means to connect the starboard and port splitter sheets 43s and 43p, respectively, to the main sheet 29. In the illustrated embodiment, such means comprises a pair of double blocks 93 and 94 through which the main sheet 29 is trained, with the double block 93 being connected by an appropriate shackle to both the starboard sheave 91 and the corresponding port sheave (not shown). To provide further mechanical advantage, a third block 95 can be included in the main sheet control system. 
     The function and operation of the improved sail system of the present invention can now be readily understood. To fit the sailboat with the sail 19, the mast 15 is non-rotatably fixed to the hull 13 and the sail 19 is hoisted to the masthead 16 by the halyard 18. To further fit the sail 19, the downhaul system 39 (FIG. 1) is attached to secure the tack of the sail 19 to the base of the mast 15, and the clews 27s and 27p (FIG. 5) are attached to the respective cars 87s and 87p at the free ends of the booms 37s and 37p, respectively. To complete the fitting of the sail 19, the backstay line 21 is tensioned to bend the mast 15 aftward, the trimmer lines 43s and 43p are tensioned to outhaul the clews 27s and 27p, respectively, and the battens 33a-f are compressibly placed in the starboard and port sail portions. With the battens so placed, the luff portions of the sail take on a wind-like shape as shown in FIG. 2, even in the absence of wind pressure. 
     At this juncture, it may be appreciated that the sail 19 is attached to the mast 15 at the masthead 16, and at the base of the mast by the downhaul system 39, and at the respective starboard and port clews 27s and 27p via the cars 87s and 87p. Accordingly, with a windload when sailing upwind (FIG. 2), the sail 19 is free to move about the mast 15 to self-adjust to a position at which the sail configuration is optimum for the wind conditions. During such self-adjusting action, the curved cross-sectional shape of the luff of the sail 19 is maintained by the battens 33a-33f. Further, the starboard and port sail shapes and leech tensions can be independently refined and adjusted by selective starboard and port movement of the cars 87s and 87p and by tensioning the respective starboard and port trimmer sheets 43s and 43p. 
     For ordinary upwind sailing, the booms 37s and 37p are arranged generally parallel to one another as shown in FIG. 2. The vertical angle of the booms 37s and 37p is determined by the vangs 47s and 47p, respectively. The free ends of the booms 37s and 37p are maintained together by the splitter mechanism 45. In the upwind sailing condition, the sail system is maintained in relatively high tension, especially along the leech. Such tension is accomplished by the aftward biasing of the mast 15, to provide a preload, and by the battens 33a, 33b, etc., and by the action of the mainsheet 29. It should be noted that leech tension in the above-described sail system can be preset and maintained independent of the draft (i.e., curvature as shown in FIG. 2) of the sail. In fact, the draft of the sail system is primarily determined by the positions of the cars 87s and 87p on the respective tracks 88s and 88p, and by the positions of the associated boom 43s and 43p. 
     For downwind sailing, as shown in FIG. 3, the trimmer sheets 43s and 43p and payed out and the respective foreguys 46s and 46p are tensioned so that the respective booms 37s and 37p move apart from one another to a reflex angle position. Under such conditions, the sail 19 floats forward of the mast 15 and takes the shape of a large, fully battened spinnaker sail. Also under such conditions, the downhaul system 39 may be payed out to let the tack of the sail 19 move toward the bow of the sailboat, with the vangs 47s and 47p continuing to support the respective booms 37s and 37p. Also in the downwind or reaching sailing condition, the distances between the clew 27s and the boom 37s, as well as the distance between the clew 27p and the boom 37p are maintained constant, but the sail shapes can be tuned by moving the travelling cars 87s and 87p on the respective booms 37s and 37 p. 
     It can be appreciated that reefing of the sail 19 for upwind sailing can be accomplished with the booms 37s and 37p in the close position by lowering the masthead halyard 18. 
     Although the present invention has been described with particular reference to the illustrated preferred embodiments, it is to be understood that such disclosure is not to be interpreted as limiting. Various other alterations, modifications and embodiments will no doubt become apparent to those skilled in the art after having read the preceding disclosure. Accordingly, it is intended that the appended claims be interpreted as covering all such alterations, modifications and embodiments as fall within the true spirit and scope of the present invention.