This invention relates generally to mechanisms and structures employed in sailing yachts. More particularly, this invention relates to mechanisms and structures for attachment of a jib.
In conventional sailing vessels a forestay is employed for attachment of the jib. The forestay is typically attached at one end to the head or part way up the head of the mast and attached at an opposite end to a location proximate the bow of the vessel.
Briefly stated, a spar, herein also called a forespar, for a sailing vessel comprises an elongated member having opposite first and second ends and defining a longitudinal axis of rotation. The elongated member has a longitudinal slot. The elongated member further has a longitudinally extending aerodynamic surface defined by a quasi-elliptical shape with identical starboard tack and port tack leading edges symmetric about a plane through the rotational axis and the slot.
A mechanism, which may be a spool and a line engaged with the spool for selectively producing a rotation of the spool, is employed to rotate the spar about the axis of rotation. The quasi-elliptical shape has a minor axis which intersects the plane. The elongated member may taper from the first end to the second end.
The elongated member may be manufactured from carbon fiber material. The elongated member has a surface portion opposite the slot which is substantially planar in one embodiment. In a second embodiment the elongated member has a second portion opposite the slot which is concave.
The spar projects upwardly at an oblique angle from a centerline of the deck. A jib is attached to the spar via one or more sliders disposed in the slot.
A wire or rod may be disposed along the axis of rotation for rotatably mounting the spar.
With reference to the drawings wherein like numerals represent like parts throughout the several figures, a forespar for a sailing vessel is generally designated by the numeral 10. The forespar 10 comprises an elongated member which has a surface configuration adapted to improve the performance of sailing vessels by incorporating an airfoil technology to the structure which is provided for the attachment of the jib.
As further illustrated in
The forespar 10 is preferably manufactured from carbon fiber, fiberglass or other suitable material. The forespar structure is best appreciated by reference to various representative cross sections as illustrated in
The forespar is provided with a longitudinal groove or slot 60 which retains the conventional slides 42 (only one illustrated) employed to attach a jib. The slot 60 is located at one end of the minor axis M of the ellipse so that the forespar is symmetrical about this location and will have the same surface shape for the leading edges 56 and 58 on the port tack and on the starboard tack. The port tack and starboard tack positions are respectively designated PT and ST in
The cross section of the forespar 10 may be tapered from the root to the tip to conform to the change in chord of the jib. 40. The forespar can retain the same shape as the size is tapered. Alternatively, the shape of the forespar may be changed as the forespar is tapered. However, the forespar must retain a cross sectional surface shape which is symmetrical about the minor axis M.
With reference to
The forespar 10 presents a smooth aerodynamic surface at the top or suction side of the jib, but also presents a blunt end at the low or pressure side of the jib. This blunt end does not cause a significant loss in performance as the low pressure side has a negative pressure gradient and the flow will not separate or cause a stall.
The forespar 10 is designed to rotate about a fixed axis A as shown in
With reference to
When the vessel tack comes about, the skipper must rotate the spar through an angle of approximately 220 degrees as illustrated in
For smaller vessels the forespar 10 can be attached to a conventional rod or wire forestay. A simple drum lever (not illustrated) can be attached to base to accomplish the rotation. Since the forespar 10 is a rigid structure, it will not lose its shape as the jib luffs when coming about. The sail will luff later and fill sooner than with a conventional rig and the upwind performance will improve.
It is believed that the forespar 10, as illustrated, will provide an increase of 10% or more in the force or lift generated by the jib and also a comparable increase in the efficiency or lift to drag ratio of the sail plane. Consequently, an increase in the speed of the boat and in the upward sailing angle would result.
Number | Name | Date | Kind |
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3112725 | Malrose | Dec 1963 | A |
3194202 | Saunders | Jul 1965 | A |
Number | Date | Country | |
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20080053357 A1 | Mar 2008 | US |