Abstract:
A teardrop shaped boom has an open interior and is rotatable about a fixed, freestanding cylindrical mast. The stays and spreaders rotate and are based on the boom. The stays provide side and back support balancing the forestay. A sail track assembly is also rotatable about the mast in conjunction with the boom to improve the airflow to the leeward face of the sail.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application is a continuation in part of my prior application Ser. No. 09/950176 filed Sep. 10, 2001. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The invention concerns a design of a boom for a sailboat where the boom is self-supporting and self-vanging and is supported by a round mast by sleeves. The luff of the sail is preferably fastened to a round mast by a sail track assembly that rotates about the mast.  
           [0003]    In the past, it has been customary to use conventional booms that are essentially straight tubes that run substantially parallel to the waterline of a boat and employ a topping lift or hydraulic vang to hold the boom in position. In the prior art there are also complete sailing rigs rotating about a step as in U.S. Pat. No. 3,968,765. In addition in U.S. Pat. No. 4,911,093 and in the “Aero Rig” by Carbospars an unstayed mast and integral boom rotate together in deck bearings and keel bearings. This solution creates bearing loads in larger sailboats that require substantial bracing.  
           [0004]    One of the dilemmas facing all modern sloop rigs is that to make the jib effective to windward there must be a backstay to tighten the jib stay. Usually the tensioned backstay is fastened at the stern that creates great loads on the hull. This arrangement prevents the use of a full roach, full length battened mainsail. One solution is to use running backstays. There is therefore a need for a different approach for the attachment of shrouds or stays in sailing vessels.  
         SUMMARY OF THE INVENTION  
         [0005]    The principal object of the invention is to provide a lightweight self-supporting boom structure that rotates about a fixed non-rotating round mast.  
           [0006]    Another object of this invention is to improve upon aerodynamic performance of a sailboat.  
           [0007]    The solution obtained is to provide a self-supporting boom structure that rotates about a cylindrical mast fixed to the hull, together with a sail track coextensive with the mast fastened to a plurality of cylinders that rotate about the mast. The boom structure serves as an attachment point for twin backstays that provide the rearward support for the jib stay and other stays. All stays are fastened aloft on a sleeve that is suitably retained in a vertical position on the mast. This arrangement allows the use of a full roach, fully battened sail plan close to ideal, as the turbulence is virtually eliminated at all angles of sail trim. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a side elevational view of a sailboat with the rig of the invention;  
         [0009]    [0009]FIG. 2 is a more detailed partial perspective view of the tripod boom and shrouds;  
         [0010]    [0010]FIG. 2A is a partial perspective of the forward portion of the boom of one version;  
         [0011]    [0011]FIG. 3 is a more detailed rear perspective view of the basic tripod boom and sliders;  
         [0012]    [0012]FIG. 4 is a basic boom structure with the sliders in accordance with the invention;  
         [0013]    [0013]FIG. 5 is a cross section of the sliders and cylinder taken on line  5 - 5  of FIG. 3;  
         [0014]    [0014]FIG. 5A is a similar cross section of a grooved track embodiment;  
         [0015]    [0015]FIG. 5B is a partial elevational view showing the mast, hoop and slider; and  
         [0016]    [0016]FIG. 6 is a side elevation view on a reduced scale illustrating a sail stowed in the boom of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]    Referring first to FIG. 1 there is illustrated a sailboat  10  having a fixed cylindrical or round spar or mast  12  fastened to the hull so as to be non-rotatable. As best seen in FIG. 2, there is provided a tripod boom generally indicated at  14  constructed as a frame in a “tear drop” shape with curved side elements  16 ,  17  that lie in a single plane, and a transverse braces  18 ,  18 ′ that joins the side elements to a mast sleeve  20 . The sleeve  20  rotates freely about the fixed mast  12 , which as noted does not rotate. Supporting the boom frame are a plurality of bracing members or trusses  22  that terminate in a base sleeve  24  that has bearings to absorb the axial loads. Shrouds or stays such as side stays  26 ,  26 ′ back stays  28 ,  28 ′ and a jib stay  30  may be provided. All stays are secured aloft to a sleeve  35  that rotates about the mast and has bearings (not shown) that secure the sleeve in a vertical position. Ideally a spreader  34  is provided that is fastened to a sleeve  36  axially secured in bearings (not shown). Each stay terminates on the boom and permits the use of a full roach, fully battened sail. It should be noted that the backstays  28 ,  28 ′ are affixed to the boom  14  slightly aft of the mast. Indeed, this arrangement allows not only a tensioned jib stay  30 , but also will allow the leech of the sail to open up going off the wind. This is particularly helpful for a full-length battened sail. The generous width of the boom structure  14  permits this result. There is no necessity for running backstays that have to be carefully released and re-tensioned on each tack. The sail may be stowed in the boom as seen in FIG. 6. Ideally, as seen in FIG. 2A, the forward portion of the boom has a transverse frame element  19  that joins elements  16  and  17 . A track  21  with a sliding car  21 a is fitted on element  19  and the jib stay  30  is fastened to the car. It will be apparent from the foregoing that the boom is supported by the truss configuration affixed to the two sleeves  20 ,  24  in suitable bearings that permit the boom to rotate as needed for sail trim about the fixed mast. Ideally the elements  16 ,  17 ,  18 ,  19 ,  22  may be fabricated from carbon fiber or aluminum tubing. The boom frame thus is the base for the stays and member  18  can be considered a lower spreader acting in conjunction with upper spreader  34 .  
         [0018]    As illustrated in FIG. 2, the boom is arranged for a balanced rig, i.e. one with a mainsail and jib, and in some cases can be fitted with a retractable bowsprit. The retractable bowsprit provides an attachment for one corner of an off-wind sail that may conveniently be stowed in the forward portion of the boom frame. The version illustrated in FIG. 2A has a sliding car  21  a that permits the tack of the jib to move to leeward. This is advantageous as there will be less backwind created on the mainsail.  
         [0019]    Ideally, the sail track should rotate with the sail. To achieve this a plurality of hoops or sleeves  40  surround the mast  12  at spaced intervals. On the inner surface of the sleeves or hoops antifriction means will be provided such as a fluorocarbon plastic (polytetrafluorochloroethylene for example). Fastened to and extending between the hoops is a sail track  42  illustrated as a “T” shape in cross section onto which conventional sail sliders  44  may be engaged. The luff of a sail  46  is fastened to the sliders such as illustrated in FIG. 5A. As seen in FIG. 5B, the track element  42   a  may be a groove into which a boltrope luff may readily slide. The track elements are preferably formed by extrusion or machining while the sliders are generally machined castings. The mainsail  46 , in either case, will be supported in a vertical position by a conventional halyard (not shown). The tack is fastened near the base of the mast and the clew to the end of the boom as at  38 . Since the mast is fixed, the structure allows the track to rotate as a unit about the mast as the trim of the sail is altered.  
         [0020]    In FIG. 1 the sailboat is fitted with a jib  50  that essentially forms a balanced rig. However the invention will work equally well with a catboat rig as seen in FIG. 4. In FIG. 4, there is illustrated the tripod boom for an unbalanced rig as for a catboat where the teardrop framework  16 ,  17  of the boom extends only from the mast and is fastened to sleeves or hoops  20   a  and  24   a.  Like reference numerals in FIG. 4 have the suffix “a”. In this arrangement the nose of the teardrop shaped boom is affixed to the mast with a collar  20   a  and is further supported by element  22   a  affixed to a spaced collar  24   a.  The sleeve  24  will rest on bearings (not shown) to absorb the axial forces. Regardless of the physical arrangement of the boom, the use of a round spar or mast is essential to the invention as it created little turbulence to windward and off the wind. The use of the rotating sail track achieves a clean airflow.