Ships – Sail or control means therefor – Reefing and furling
Reexamination Certificate
2000-12-26
2002-04-16
Sotelo, Jesus D. (Department: 3617)
Ships
Sail or control means therefor
Reefing and furling
C114S108000
Reexamination Certificate
active
06371037
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a mainsail furling system containing a boom-mounted furler, intended for use in yachts.
2. Description of the Prior Art
Roller furlers and reefers for use in sail boats are well known, especially in the case of yachts
1
. These devices provide convenience and ease of use, as they can generally be handled by a single person, usually from the cockpit of the sail boat, and often by the helnsman. This is true even on yachts whose length is in excess of 40 feet, whereas, before the advent of roller furlers is was necessary to have two or more people to handle the hoisting and lowering of sails. However, the convenience of prior art furling systems has often been offset by a diminution in the performance of the sails.
The traditional usage of the word “yacht” is used here: a sailing boat used for pleasure.
Furling and reefing a separate, but related, activities: furling denotes the complete retirement of the sail from use, wherein the furled sail no longer presents any cross section to the wind for the purpose of driving the boat. Reefing, on the other hand, refers to the shortening of sail by reducing the sail area so as to provide less cross section to the wind, reducing the driving force of the wind on the sail. Since most furlers are also used as reefers, the terms will be used interchangeably herein.
Some furlers are designed to be used with sails normally mounted on the stays of a vessel, more particularly on the jibs of sailboats. Others, generally referred to as mainsail furlers, operate on sails which are affixed to two spars at right angles to each other, usually the mast and boom. So-called mainsail furlers are also used on the mizzen sails of ketches or yawls, on the sails mounted on the foremasts of schooners, and so forth. They will all be referred to herein as mainsail furlers for the purpose of this description, and the sails they control will be referred to as mainsails.
Mainsail furlers present a much more difficult design problem than jib furlers, since the jib furler is attached along its luff to a stay, and may be simply wound around the stay like a window shade. The mainsail furler, on the other hand, having two long lines of attachments to two spars perpendicular to each other, has problems unique to its geometry.
Many of the first mainsail furler designs furled the mainsail within the mast (“mast furlers”), allowing the foot of the sail to slide along the boom toward the mast when the sail is furled. These system have certain disadvantages over the systems in which the sail is furled on or within the boom (“boom furlers”). First of all, the mast furlers require a main part of the apparatus within the mast itself, thereby increasing the weight aloft, and affecting the stability of the vessel under sail. Furthermore, the mast furlers present a nasty maintenance problem, in the case of malfunction or damage to the system. Often, someone is required to go aloft to repair even simple malfunctions, such as jams, which is an unhappy situation for many amateur sailors.
Boom furlers, on the other hand, present their own unique problems. The preferred boom furler at present contains a rotating mandrel mounted within the boom, with a drum at the mast end of the boom. In some embodiments of the prior art the foot rope of the mainsail is affixed to the mandrel along its length. In others, the mainsail is attached only at the tack and clew, that is, the ends of the foot. A winding cord is wound around the drum, and exits through the mast end of the boom. When the sail is hoisted, the winding cord winds itself about the drum; when furled, the user pulls on the winding cord, causing the mandrel to rotate, winding the sail about the mandrel. The drum has large side plates, to keep the winding cord from wandering off the drum and jamming the mechanism. Furthermore, the drum must be rather elongated, since it must fit within the boom, and must provide room for a length of winding cord equivalent to the height of the mainsail, wound about the drum.
A prior art furling system is shown in FIG.
1
. Referring now to
FIG. 1
(prior art), it is seen that in the luff
2
of the mainsail must be set back at least as far from the mast as the length
1
of the drum in this type of system, plus the width of bearing
4
, and distance g of the gooseneck. As a result, the luff
2
is too far removed from the mast
6
to allow a direct connection by sliding a rope sewn into the luff (luff rope) into a slot in the mast, as is commonly done in non-furling mainsail rigging. Instead, a luff extrusion
8
is provided in these prior art systems, to which the luff is attached. Typically, the luff extrusion contains slots to allow insertion of the luff rope, similar to the way the mainsail luff is attached to the mast in non-furler systems. The luff extrusion
8
is affixed to the mast by supports
10
, and are affixed non-rotatably to the mast.
Thus, when the boom begins to rotate with respect to the mast, it does so along axis a, which passes through the pin
12
of the gooseneck. The sail, on the other hand rotates about axis b, which, in some prior art implementations, is at some distance from axis a. In such systems, the set of the sail is impaired, and the luff extrusion is subjected to a twisting, with the top of the sail not parallel to the bottom along the luff line. This type of twist diminishes said sail performance.
Furthermore, the large slot is created between the mast and the luff of the sail. Although this so-called “slot effect” has been extolled by purveyors of this particular design, it should be noted that no manufacturer to date has introduced this slot in the absence of the need to do so because of the furler design. It is generally believed that such a large slot diminishes sail performance, rather than enhancing it.
Placing the drum at the after end of the boom, and in the current invention, presents a number of improvements over the prior art. Most noticeably, the luff of the sail is in close proximity to the mast, as shown in FIG.
2
. The supports have been reduced in size, thereby reducing the torsional stress on the supports caused by the misalignment of the center of rotation of the gooseneck and that of the luff of the mainsail. In some designs, the luff may be attached directly to the mast by means of a mast slot, thus doing away with the supports altogether.
The present design further incorporates a guide which facilitates entry of the lower portion of the mainsail into the opening in the boom through which the mainsail enters. This guide is especially important in the case of the luff end of battens entering the boom opening.
An additional feature of the present invention is the use of a luff-extrusion, which has a U-shaped cross section, with the arms of the U long enough to support the leading edge of the sail battens, and create a compression of the sail batten, thus maintaining the sail shape properly. The reason for this feature may be understood by referring first to
FIG. 2
a
, which shows a prior art system for attaching the mainsail to the mast.
Referring now to this figure, it is seen that the mainsail
110
is attached to the mast
6
by means of a luff rope
112
which slides in a slot in a luff extrusion
8
which is attached to the mast. The boat in this figure is “in irons”, or “heaved to”—that is the boat direction
120
is faced directly into the wind
100
, and the sail in this figure is accordingly limp, and there are no forces exerted on the luff rope or sail luff. The boat will not advance under this point of sail, but lies motionless in the water, except for the effects of the tide, or the wind blowing on the hull.
When the boat falls off the wind a bit and comes onto close-hauled position, as depicted in
FIG. 2
b
, where the wind
100
is now at an acute angle with respect to the boat direction
120
, the situation changes significantly. The sail is attached at its after end, or clew
118
, at the after end of the boom. As a result, the pressure of the wind caus
Cook Fred C.
Dion David R
Sotelo Jesus D.
White Mark P.
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