Abstract:
A sail boat boom control system provides braking forces for restraining movement of the boom during down wind sailing or sailing with a quartering breeze. The system comprises a boom restrainer loop attached to the boom and resiliently tensioned, pivotally mounted friction device which is adjustable to apply friction forces restraining movement of the boom loop, thereby providing the braking force on the boom. The friction device is adjustably controlled by a control line extending to a position where it is easily operated by the helmsman or other crew. A quick-release device releases the control line when required to allow the friction device to move to a position in which the boom is free from restraint. Deck-mounted and mast-mounted friction control devices are disclosed.

Description:
FIELD OF THE INVENTION 
     This invention relates to a boom control system for a sail boat and, more particularly, for a system for controlling the position of the boom of the boat, particularly when the boat is being sailed down wind or with a quartering breeze. 
     BACKGROUND OF THE INVENTION 
     A number of devices have been available for locking or stabilizing the position of a boom of a sail boat when sailing with a following or quartering breeze. The importance of some control will be recognized by those skilled in the art who have experienced the effects of an accidental jibe due to a shift in wind direction or when the helmsman accidently changes course so that the wind is on the opposite side of the main sail and the boom suddenly swings across the deck. Such accidental jibes are hazardous to the crew, can cause serious damage to the rigging and may even cause a knockdown of the vessel. Even controlled jibes can be hazardous if not done with care. 
     Short of lashing the boom or through use of a preventer or similar boom locking device, a number of sail boat boom brakes utilizing the frictional resistance applied by a friction device to a line which restrains movement of a boom have become available and are a part of the prior art. One of these systems known as the Heinson boom control system produced by the Heinson Co., Moraga, Calif. works on the principle disclosed in U.S. Pat. No. 4,138,962. In this type of system, a friction device in the form of a single friction drum is carried by a hanger attached to the boom of the boat. A line attached to one or more cleats accessible from the cockpit extends forwardly to a swivel block mounted on the deck. The line extends from the swivel block to the drum, is wrapped around the drum several times and then extends downwardly to a second cleat or another swivel block on the opposite side of the boat from which it is extended aft to a second cleat accessible from the cockpit. When the line is cleated, frictional resistance with the drum locks the boom in place. Tension may be released from the cockpit entirely or may be gradually released as a jibe occurs, thereby easing the boom to the desired position. 
     More recently issued U.S. Pat. No. 5,390,617 illustrates another type of boom brake mounted on a hanger attached to the boom. In this patent, the hanger carries three spools or sheaves. A line secured adjacent one side of the deck extends to the boom and in a serpentine path is in contact with the friction surfaces of the three spools. Two of the spools are fixed against rotation and the third, offset between the first two, is rotatable and is provided with a manually adjustable brake so that a variable frictional resistance to motion can be applied. In a further embodiment of the patent, where adjustable braking is not required, the three spools are all non-rotatable. 
     Many sailors object to devices of the kind described due to the fact that they are relatively difficult to control by the helmsman while he is in the act of steering the boat and also because the relatively heavy braking device is located where it can strike the head of a crew member, creating the kind of hazard that such devices are intended to eliminate. 
     SUMMARY AND OBJECTS OF THE INVENTION 
     In summary, the invention comprises a sail boat boom control system which consists of a single loop line extending across the boat and through two or more swivel blocks to locations on the boom spaced away from the mast. A section of the line passes through a pivotally-mounted friction device for application of friction resistance to the loop, thereby restraining movement of the boom. The friction device can be set from the cockpit by the helmsman to provide the degree of frictional resistance deemed necessary to control the swinging motion of the boom. 
     In accordance with the invention, first resiliently operable means act on the loop to take up slack and provide a degree of resilience to the restraint of the boom. An adjustable tension control device is operable to regulate the friction device to apply the desired tension on the loop, thereby causing the necessary frictional resistance to movement of the line, thereby providing the braking force. The device allows for return to a release position in which no frictional resistance is imparted to the loop, and the boom is free to swing without restraint. 
     Objects of the invention include the provision of a sail boat jibe control system which is easy to set up and use with minimal interference with the use of cockpit space. 
     Another object of the invention is the provision of a jibe control system which is easily and quickly adjustable so as to accommodate changes in said conditions. 
     A further objective of the invention is the provision of features allowing for instantaneous release of restraining forces on the boom. 
     Other objects and advantages will become apparent from the following description and drawings illustrating presently preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a first preferred form of the invention in which a deck-mounted boom control system is provided; 
     FIG. 2 is an elevational front view of a sail boat showing an embodiment of the invention wherein the control device is mounted on the forwardly facing surface of the mast of the sail boat; 
     FIG. 3 is a sectional view of the control device used in the embodiments of FIGS. 1 and 2, the device being an enlarged scale with respect to FIGS. 1 and 2; and 
     FIG. 4 is a plan sectional view taken along lines 4--4 of FIG. 3. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference first to FIGS. 1, 3 and 4, a sail boat 10 has a mast 11 to which a boom 12 is pivotally mounted for movement between positions substantially as shown by broken lines 12a and 12b. As is known in the art, a main sail (not illustrated) is attached to the mast and the boom. 
     According to the embodiment of the invention illustrated in FIG. 1, a boom restrainer line 14 is resiliently tensioned and affixed to the boom 12 by means such as first spring 15 having a hook at one end which is attachable to eye 16 or other suitable attachment device, such as a bail projecting downwardly beneath the boom. A first section of line 14 extends from spring 15 to a swivel block 17 of conventional construction which, in FIG. 1, is located along the starboard rail of the boat. Restrainer line 14 then extends forwardly along the deck through a second swivel block 18, crosses the deck to a swivel block 19 adjacent the port rail, then aft to a fourth swivel block 20 and then diagonally upwardly from block 20 to the boom where it is resiliently attached by a spring 21 having a hook-shaped end which is hooked through a second eye 22 secured to the boom 12 adjacent to eye 16. The points of attachment to the boom should be equidistantly spaced from mast 11 and may be a single bail hanging from the boom. As shown, the springs yieldably tension line 14 for reasons to be explained hereinafter. The restrainer line 14 provides a loop which moves with the boom and serves as a means for restraining boom movement. 
     In the embodiment of FIG. 1, the side-to-side motion of the boom 12 is controlled by a control device 24 which provides friction resistance to movement of boom restrainer line 14. Control device 24 is pivotally mounted on the deck of the sail boat 10 in a position located forwardly of the mast, although other mounting positions may be used and are considered to be within the scope of the invention. 
     With reference to FIGS. 3 and 4, control device 24 preferably includes a base 25 bolted or otherwise firmly secured to the deck of the boat and a pair of elongated members 26 and 27 between which a pair of sheaves 28 and 29 having oppositely facing friction surfaces 28a and 29a respectively are positioned for interengagement with the surface of the boom restrainer line. Sheaves 28 and 29 are non-rotatably secured between members 26 and 27 by any suitable means such as bolts 30 and 31. A bolt 32 extending through sleeve 33 and threaded into base plate 25 comprises a pivotal mounting means for pivotally mounting members 26 and 27 for rotary movement with respect to the base 25. A coil spring 34 having one end connected to member 26 and the opposite end to base 25 fits over sleeve 33 and biases the members 26 and 27 to the full line position shown in FIG. 1. As best seen in FIGS. 1 and 4, the sheaves are laterally offset from the pivotal axis so that there is no interference between sleeve 33 and the boom restrainer axis. Additional bolts 35a and 35b are provided to secure the plates together and act as retainers for the control line. 
     For adjusting the position of control device 24, an adjusting means such as control line 39 is secured at one end of members 26 and 27 by means such as bolt or bail 36. Line 39 extends through a swivel block 37, an eye 38 and is fastened by means such of a jam cleat 40 which may be located near the cockpit for access by a crew member. Preferably, cleat 40 is fastened where it can be easily reached by the helmsman. 
     According to the invention, no resistance to shifting movement of boom 12 is offered when the control device 24 is as shown in the full line position of FIG. 1. In order to provide resistance to movement of the boom restrainer line 14, the control device is pivoted in a counterclockwise direction from the position in which it is illustrated in FIG. 1 in full lines. Rotation of the control device from the full line position to the broken line position increasingly tensions the boom restrainer line and increases frictional resistance to movement of the line which accordingly increases restraining forces on the boom. In the fully rotated position, which is typically substantially at 90° from the full line position illustrated, the boom may be substantially locked in any selected position. In intermediate positions of adjustment of the control device, such as that shown in broken lines in FIG. 1, sufficient resistance to movement of the restrainer line is provided, so that in the event of a jibe, the boom will move slowly and in controlled fashion from one side of the boat to the other. The degree of tension being selectively controlled by the helmsman or other member of the crew can be accomplished without the need to leave the cockpit. 
     Turning now to FIG. 2, an embodiment of the invention is illustrated in which the control device 24 is mounted on the forward surface of the mast 11. In the description of FIG. 2, like numbers will be used to identify like parts. As in FIG. 1, one end of boom restrainer line 14 is connected to boom 12. Although the line may be attached by means of a coil spring as in the embodiment of FIG. 1, the necessary tension is supplied in FIG. 2 by a block 44 which is resiliently attached to the boom by a spring 15a. The restrainer line extends from boom 12 to swivel block 17 adjacent the starboard side of the boat and then extends across the deck to a second swivel block 42 secured to the base of the mast 11. From the base of the mast, restrainer line 14 extends upwardly between sheaves 28 and 29, passing around upwardly biased swivel block 44 fixed on the mast 11 above control device 24. The restrainer line then extends vertically downwardly to a sheave 45 affixed to the mast and/or other suitable surface proximal to the swivel block 42. The restrainer line then extends laterally to a swivel block 47 located adjacent the port side of the boat and then extends diagonally rearwardly to a fastener such as eye 22. As indicated above, the restrainer line in FIG. 2 is resiliently tensioned by spring 15a. 
     As in the embodiment of FIG. 1, tension control means is preferably provided by control line 39 which is affixed to a bracket or bail 48 on an upper surface of control device 24. Control line 39 extends downwardly to a guide or block 49 mounted on the deck and from there to cleat 40 attached in or adjacent to the cockpit for accessability by the crew or the helmsman. 
     Similarly to the embodiment of FIG. 1, rotation of the control device 24 from the vertical position in which no resistance to movement of the line and the boom is provided to positions of increasing resistance as shown, for example, in the broken line position, is provided. Thus, either embodiment of the invention allows for the application of the required amount of frictional resistance to swinging motion of the boom from any selected boom position. 
     In the implementation of the invention, it should be understood that other mounting locations for control device 24 may be provided so long as the device is pivotally movable from a position in which no frictional resistance is offered to movement of the line to a position in which motion is prevented, except under the most adverse wind conditions. In addition, the portions of the restrainer line extending from the boom may pass through swivel blocks attached to the shrouds so as to keep them clear of the deck if desired. The resilient tensioning of boom restrainer line 14 provided by springs 15 and 21 of FIG. 1 or spring 15a in FIG. 2 may be provided at other positions along the line, as by spring-mounted blocks. 
     In use, the sheaves provide arcuate contact paths with the boom restrainer line which provide increased resistance to movement of the line as the control device is rotated. If needed, further increase in frictional resistance to line movement can be provided by increasing line diameter. Release of control line 39 can be accomplished quickly and immediately causes return of the control device to the position in which the boom is unrestrained.