Luff pad for roller reefing and furling sails

A luff roller reefing and roller furling sail is provided with a luff pad (6) made up of a laminate of a sail fabric (1) adhesively bonded to a polyurethane elastomeric foam (3). The pad is then adhesively bonded and/or stitched to the length of the luff of a sail (5), tapered from mid-luff to the tack and head. A luff tape is preferably adhesively bonded and stitched over each face of the laminate. When the sail is furled, the tapered luff pad provides bulk to cause more fabric to be drawn from the central portion of the sail, reducing draft and controlling position of the draft in partially furled conditions, and maintaining aerodynamically sound shape in the sail for windward performance.

BACKGROUND 
Roller furling and roller reefing (partial furling) of sails has come to be 
common and popular on a substantial variety of sailing vessels, and 
permits effective sail handling with reduced crew requirements and a host 
of other advantages. 
In such systems, the sail is supported on and fixed to a stay which is 
adapted to rotate. When the sail is in place, it will be furled by being 
rolled around the outside of the rotatable stay. When fully rolled up, or 
furled, the sail may be left in place, ready for immediate use, not 
requiring stowage below decks, or crew handling to get it there. Unfurling 
is rapid and undemanding, so that making sail and getting under weigh is 
facilitated. 
A wide variety of roller furling systems are known in the art, and do not 
per se form a part of the present invention, which is suitable for use 
with any such system. 
Roller furling systems are also frequently employed in partially furled 
condition to reef the sail. In increased winds, where the sail area is 
greater than desirable, roller reefing is effective to reduce sail area, 
heeling moment, leeway, and to preserve control, particularly steering 
control, of the vessel. Roller reefing is progressive, and adaptable to 
wind and wave conditions as they occur. The alternative to reefing is to 
change to a smaller sail, which is demanding of crew and in some 
conditions working on the bow is hazardous. Other reefing techniques for 
headsails are not generally desirable, and represent little or no 
improvement on changing sails. 
It is characteristic of such roller furling systems that as the luff of the 
sail is rolled on its stay, luff tension on the sail is decreased, and to 
a degree the bulk of material in the structure of the foot and leach of 
the sail cause the volume of material rolled around the stay to be 
greatest at the tack and the head. As a consequence, the sail develops 
excessive sag and draft in the center, and the location of the maximum 
draft moves aft. The problem is exacerbated by bias stretch of the sail 
fabric, which is ordinarily least controllable in the central portions of 
the sail structure. These aspects of roller furling are counter 
productive, as the shape of the sail is less effective, particularly for 
sailing to windward. Heeling moments remain higher than desirable, and 
boat performance is lost. 
It has long been recognized that increasing the bulk of the roll in the 
mid-region of the luff of the sail as it is partially furled can alleviate 
much of the problem, and make roller reefing a far more effective 
technique. It is also known that the increased bulk of the furled sail on 
the stay is aerodynamically superior to the sag and stretch of the sail. 
Such expedients as enlarging the central, mid-luff portion of the stay, or 
hoisting an elongated member along the luff to become rolled into the sail 
as the furling takes place have been tried. The enlarged stay is 
aerodynamically undesirable. The hoisting of a luff "partner" is a 
backward step, since it puts the crew back on the bow of the vessel in 
dangerous conditions and circumstances. 
PRIOR ART 
U.S. Pat. No. 4,196,687, of Richard C. Newick, issued Apr. 8, 1990, 
discloses a luff roller reefing and roller furling system which provides a 
pocket built into the luff region of the sail, into which a foam pad is 
inserted. While the Newick system is generally effective, construction of 
the pocket in the sail is intricate and labor intensive. Insertion of the 
foam into the pocket is difficult. Most significantly, the Newick foam pad 
is confined inside the pocket, but is not fixed or bonded in place, and is 
vulnerable to deterioration of the foam, the sail fabric, and the 
stitching around the boundary of the pocket and seams of the sail panels 
across one face of the pocket, due to friction between the foam pad and 
the sail and pocket structure. The structure is also prone to the 
formation of wrinkles in partially furled or reefed conditions, which are 
aerodynamically undesirable. 
SUMMARY OF THE INVENTION 
A luff roller reefing and roller furling sail is provided with a luff pad 
made up of a laminate of a sail fabric adhesively bonded to one or both 
faces of a polyurethane elastomeric foam. The pad is adhesively bonded 
and/or stitched to the length of the luff, tapered from mid-luff to the 
tack and head. A luff tape is preferably adhesively bonded and stitched 
over each face of the laminate. When the sail is furled, the tapered luff 
pad provides bulk to cause more fabric to be drawn from the central 
portion of the sail, reducing draft and controlling position of the draft 
in partially furled or reefed conditions, and maintaining aerodynamically 
sound shape in the sail for windward performance.

DETAILED DESCRIPTION 
In the present invention, a sail luff pad is provided for use in the 
construction of roller furling and roller reefing sails. It is simple and 
facile to use, economical of materials and labor, and highly effective and 
durable in use. 
The luff pad is a deformable laminate of an elastomeric polyurethane foam 
core, faced on at least one side with an adhesively bonded layer of fabric 
or film, preferably of sail cloth. Both faces may be faced with sail cloth 
when desired. 
In FIG. 1, the arrangement of parts in the luff pad laminate is shown. The 
foam core (3), is bonded to sail fabric (1) through the use of adhesive 
(2). 
The laminate is generally from about 0.1 to 2.5 cm thick, in a width of 
from about 10 to 90 cm, and made in running lengths suitable to be cut to 
about the length of the luff of the sail to which the pad is to be 
applied. As those of ordinary skill in the art will recognize, thicker and 
wider laminates will often be desirable in larger sails, while thinner and 
narrower laminates will be more appropriate in smaller sails. A suitable 
all-round product will have a thickness of about 3 to 5 mm, and a width of 
about 20 to 40 cm. As will become apparent, the length may be "spliced" at 
the time of application if required. 
The polyurethane core material may be generally any elastomeric 
polyurethane foam. A number of such materials are known and available. As 
a general rule, a relative firm foam is often desirable to avoid excessive 
compression when rolled on the stay on which the sail is set, but such 
considerations are not narrowly critical or significant to the invention. 
The foam must afford sufficient elasticity to accommodate the deformation 
required when the sail is furled and unfurled without cracking, breaking, 
or taking an excessive degree of set. Most elastomeric polyurethane foams 
will satisfy these criteria. It is generally preferred to select a 
suitable material among those commercially available in suitable 
dimensions, or which can readily be cut to suitable dimensions without 
substantial waste. 
The facing on the foam may be any flexible and durable film or fabric. Film 
materials may be polyvinyl chloride, polyethylene terephthalate and the 
like, which may conveniently be plasticized to enhance their durability to 
flexural stress, and compounded with u.v. stabilizers to resist exposure 
to sunlight. In addition, any suitable fabric may also be employed, with 
polyesters, and particularly polyester sailcloth being most preferred. 
The sail cloth fabric employed in the facing can be any available sail 
cloth, most often a square weave Dacron.RTM. polyester or the like for 
economy, ready availability, and convenience. The more specialized sail 
cloth materials, such as special weaves or exotic materials, are not 
required and the greater expense is generally not warranted, although such 
materials may be employed if desired. If such materials are employed, the 
sailmaker may be able to take advantages of specific properties in the 
design and construction of the sail. Such materials as Kevlar.RTM., 
Spectra.RTM., and the like, and such weaving techniques as triaxial, 
unbalanced, axial, and the like may be used, for example, although not 
required. 
Sail cloth weights in the range of from as little as 1 ounce per yard and 
up to as much as 24 ounce per yard are available, and may be employed, 
although in most circumstances, extremes are neither required nor 
desirable. A conveniently and widely available, relatively light weight 
balanced weave fabric is most often preferred, such as a 2.5 ounce square 
weave Dacron.RTM. polyester. A heavier fabric may be preferred for larger 
sails. 
It is preferred, but not required, that the fabric be uncoated, unsized, 
and scoured before use in forming the laminate of the present invention to 
maximize wetting and bonding of the laminating adhesive to the fibers of 
the cloth. 
The weight of a fabric, including sail cloth, is usually specified in 
ounces per yard. This measurement is based on the weight of a running 
length of one yard of a fabric a standard 28 inches wide, and is a common 
industrial standard of measurement for fabric materials employed 
world-wide. 
The laminating adhesive may be any of the elastomeric adhesives available 
which will effectively bond both the polyurethane foam and the polyester 
fabric. Elastomeric polyurethane adhesives are greatly preferred for their 
excellent bond strength, durability under stress, and their resistance to 
environmental degradation, from water, particularly sea water, heat, 
humidity, and sun. These are generally the same characteristics which make 
polyurethane elastomer foams the preferred materials for the laminate 
core. Other materials, particularly other synthetic polymer adhesives, and 
even foams, may be employed, but ordinarily only with some compromise in 
the properties of the laminate. 
The greatest performance properties are, as a general rule, attained with 
polyurethane elastomer adhesives which cure at elevated temperature, with 
or without the application of moisture or other cure accelerators. 
When the foam and facing materials permit, hot melt bonding may also be 
employed. As those of ordinary skill in the art will readily understand, 
the foam or the facing or both must be thermoplastic in order to employ 
thermal bonding. In such circumstances, the laminate of foam and facing 
may be conveniently formed on heated calendar rolls 
The laminating process to be employed is not narrowly significant to the 
invention, and may suitably be selected from any convenient technique 
known to those of ordinary skill in the art. Typically, the fabric and 
foam will be roll coated with the adhesive in separate operations, and the 
parts then brought together with the application of pressure and, if 
appropriate to the specific adhesive, heat, moisture, or other cure 
accelerators are applied. Passing the mated fabric and foam through the 
nip of a pair of rolls, with the nip set to a gap about half the thickness 
of the laminate, will generally be sufficient to attain a good wetting out 
of the fabric and foam with the adhesive, and assure freedom from air 
bubbles and the like. 
As those of ordinary skill in the art will recognize, the cure reaction 
will continue at ambient conditions for some time. After about one week, 
the cure will ordinarily be in excess of ninety percent, and in many 
systems in excess of ninety eight percent, of full cure properties. It is 
accordingly preferred to store the laminate for at least about one week 
prior to use. 
The cured laminate will be applied to the sail during construction in most 
circumstances. FIG. 2 shows a side view of the rough sail blank (5) 
showing the laminate in a configuration suited to serve as luff pad (6). 
It is generally preferable to apply the foam pad to the sail blank, after 
the sail fabric panels are cut and seamed, by stitching or glueing and 
stitching, and application of reinforcing patches usually applied to head, 
tack and clew, but before final finishing operations, such as taping the 
luff, leach and foot, or the application of cringles, reinforcing straps, 
reef grommets, or the like. 
In most circumstances, the luff pad is laid over the rough sail blank, and 
pinned in place on the loft floor. The pad is cut to a length 
substantially the length of the luff, generally within 5 to 15 cm from the 
tack and head. A suitable taper is formed, as by marking a smooth, fair 
curve on the laminate, which is then cut to shape with scissors or shears. 
It is convenient to mark the sail fabric with the layout of the laminate 
as an aid to registration when it is installed. The pad is then coated on 
the mating face, which is the foam face if the laminate is covered with 
fabric on only one side, and laid in registration with the marked position 
on the sail blank, and smoothed and pressed in place. A roller may help to 
remove entrained air bubbles, if needed. If the bonding adhesive is cured 
at elevated temperature, an iron may be employed to raise the temperature 
to a suitable point. 
It is preferred that the pad be adhesively bonded to the sail blank, but if 
desired it may be temporarily fixed in place, by staples or pins or the 
like, and then stitched to the sail cloth. 
The sail cloth will often bear a finish or sizing, and must be used in 
unscoured form. This will be significant in the selection of the adhesive 
to be employed in the bonding operation. It will generally be preferable 
to employ the adhesive recommended by the sail cloth manufacturer for 
glueing seams, particularly since the nature of sizings and finishes on 
sail cloth are often proprietary. 
Once the pad is bonded in place and the adhesive has cured sufficiently to 
permit handling, it is generally preferable to also stitch the pad and 
sail together at the edges, in the usual form for seaming between panels 
in sail construction. 
If a sufficient length of the foam laminate is not available for a single 
piece application, plural pieces may be applied in a "spliced" 
arrangement, by simply butting the joints between adjacent pieces. The 
joints, once bonded to the sail, should be stitched, and preferably double 
stitched along the joint. Other stitching across the width of the laminate 
pad is generally not preferred, although it may be appropriate in large 
sails. 
After the laminate pad is in place, the sail may be finished in the usual 
fashion. When a luff tape is applied, it is desirable, and in most cases 
necessary, that it be bonded over the foam pad as well as the sail 
structure, where it is normally glued and stitched in place. 
The finished sail can be handled like any other roller furling sail without 
regard to the laminate pad. When the sail if flaked in preparation for 
setting, it may be found that the luff bulk makes the sail a bit less 
handy, but significant problems are not created. Once the sail is hoisted 
on its stay, the luff is tensioned in the usual fashion. Sail handling 
under weigh is normal in every respect. When the stay is rotated to reef 
or furl the sail, there are no differences in the handling of the gear or 
its operation, but there will be a substantial improvement in the set of 
the sail in the partially furled or reefed condition. 
As the stay rotates, the bulk of the laminate pad is greatest in the 
mid-luff region, and causes more material to be rolled onto the stay in 
that region. The sail thus does not increase in the depth of draft, and 
the draft is retained well forward, and very near the designed location 
(forward of mid-chord, and most often about 40% aft of the luff). 
The details of the associated furling gear, the design of the sail, and 
other related parameters are not themselves a part of the present 
invention. They will vary from boat to boat. In general, however, usage of 
such a system may be described as follows: 
When under sail to windward, in an increasing breeze, the vessel will heel 
to leeward in proportion to the wind strength. At some wind speed, which 
varies from boat to boat, the helmsman will be able to detect an increase 
in heel or weather helm or, most often, both which is excessive. The limit 
in weather helm is the most usual indicator of the point at which reefing 
is desirable (assuming the rig and sails are in proper tune and trim). 
When the decision is made to reef the roller furling sail, the sheet is 
eased, the roller furling gear is actuated for several rotations of the 
stay, and the sheet is then retrimmed to the newly reduced sail 
configuration. If weather helm or angle of heel are still excessive, 
further reefing rolls are taken. If boat speed drops, and heel and weather 
helm are modest, the sail may be partially or wholly unreefed, by a 
reversal of the reefing procedure. 
BEST MODE 
A Dacron.RTM. polyester sail cloth of square weave and a weight of 2.5 
ounces per yard was cut to a width of 20 cm and a running length was roll 
coated on one surface with a polyurethane elastomer adhesive. 
A 0.2 cm thick polyurethane elastomer foam was cut to a width of 20 cm and 
a running length was roll coated on one surface with the polyurethane 
elastomer adhesive. 
The adhesive coated faces of the fabric and the foam were mated and passed 
through the nip of a pair of heated calendar rolls set to a gap of 0.1 cm 
and a temperature of 140.degree. C., and passed through a hot air oven 
maintained at a temperature of 120.degree. C. with a residence time of 12 
minutes. 
The laminate was cooled by ambient air for five minutes after exiting the 
oven and then taken up on a roll and stored at ambient conditions for one 
week before use. 
A roller reefing and roller furling Genoa jib was laid out on a sail loft 
floor, and the panels were cut, glued and stitched. A length of the luff 
pad laminate equal to the luff length was cut from the roll and laid over 
the luff of the roughed out sail and pinned to the floor. A batten was 
used to develop a fair taper marked on the pad, ranging from full width of 
20 cm in the mid luff portions to 2 cm adjacent the tack and head. The 
taper was cut with shears, and the edges were marked on the sail for 
subsequent registration. 
The foam face of the laminate was coated with thin layer of an ambient 
curing polyurethane elastomer adhesive. The adhesive coated face of the 
pad was applied to the roughed out sail, in registration with the 
previously applied markings, and the adhesive was allowed to cure for 
about two hours. After the cure, the edges of the luff pad were stitched 
to the sail panels. The sail was then finished in the usual fashion. When 
the luff tape was applied, it was glued over and stitched through the pad 
as well as the sail fabric. The construction is illustrated in stylized 
form in FIG. 3, where the sandwich foam laminate (7), having facing (1), 
and adhesive bond (2) is applied over luff pad (3), and adhesively bonded 
in place. The assembly is stitched in place (8 a, 8b, 8c, 8d) including 
stitching through the luff tape (9) and luff pad (8b, 8c, 8d). Fabric 
elements (10a, 10b) of luff tape (9), of conventional form, overlie the 
front of the sail. Luff tape (9) is applied after the laminate is in 
place. 
The sail was tested on a sail boat. Roller reefing and roller furling of 
the sail was normal in all respects, as was operation and performance in 
fully unfurled condition. When partially furled, i.e., reefed, the pad was 
observed to maintain a suitable aerodynamic shape for windward 
performance, without excessive draft in the center of the sail. The 
maximum depth of draft remained in substantially the same position as the 
fully unfurled sail, at about 45% of chord aft of the luff. 
Repeated furling and unfurling in a variety of conditions, including wind 
strengths up to 30 knots, revealed no unusual behavior. The pad and sail 
remained in excellent condition over the course of trials.