The advent and refinement of roller furling has so revolutionized the problems of sail stowage and reefing that furling devices are now standard equipment on nearly all modern voyaging yachts. The reliability and efficiency of these systems has advanced to where their popularity has extended beyond the voyaging community, which has traditionally been most concerned about cost and durability, and onto racing yachts, for which performance is of paramount importance. Many manufacturers’ products are now refined after having been tested on numerous global offshore contests as the Vendee Globe and the BOC Challenge.
Nonetheless, the bulk of furlers are installed and used on board voyaging yachts. Like numerous other components found on the modern voyaging yacht, the challenge for furling manufacturers is therefore to produce reliable products that require minimal skill in operation, installation, or maintenance.
The foredeck ranks second only to being aloft as the scariest place to work on a vessel offshore, especially for the inexperienced and physically limited. Avoiding the inherent hassle and potential danger of working on the foredeck to set or retrieve headsails that are either hanked on or run up a luff-grooved headstay has been the driving force for the development of jib-furling systems. Like anything else in sailing, there is a trade-off. The drawbacks of furling systems and furled sails are accepted by the user in return for the assumed simplicity, speed, and safety of remotely dousing all or part of the headsail.
The same logic applies to mainsail-furling systems, more for reasons of easy sail handling than the necessity for safety (although the two can obviously be related in many situations). Their cost-benefit trade-off is often harder to justify in all but the larger voyaging yachts in which the sail cannot be easily doused, reefed, or flaked by one or two crew-members. While their features and limitations are discussed below, it is significant to note that mainsail-furler development is still a generation or two behind jib-furlers.
For the performance sailor, any installed furling system will adversely affect boat speed by the additional windage and weight aloft from the hardware. This is in addition to significant limitations on sail size and shape, particularly in the mainsail. Therefore, among race boats, furling systems are found only on offshore, short-handed craft where the trade-off of easier handling and greater safety is acceptably offset by a loss in performance. Another important exception is in some lightweight, high-performance sport boats, such as the Melges 24 and the Ultimate 20 racers, for which the ease of sail handling is of primary importance.
Headsail furling systems I. Furlers. There are currently more than a dozen different manufacturers of jib-furling systems, each offering specific designs suited for different-sized yachts. Some provide the market with a low-cost system that is simple in its installation and use, but usually at the expense of enhanced performance and durability. Others offer more sophisticated designs which use high-tech materials to produce units which will last and perform longer, but for a substantially higher price. Like most marine equipment, the best choice for the offshore sailor comes only after an informed assessment of how each available option strikes several balances.
Despite all the options, most furler designs have evolved similar features: pieced aluminum alloy extrusions of double aft-grooved shape that fit over a new or existing headstay; some type of spacer or bearing to center the headstay inside the extrusion; except on internal halyard designs, some kind of upper swivel assembly that links the sail to the halyard and rides up the extrusion when hoisted; and a drum assembly at deck level that holds the furling line when the sail is fully or partially extended.
The differences among manufacturers’ designs are principally in their solutions on how to prevent halyard wraps; whether and what type of bearings are used in the swivel assemblies; how the extrusions and spacers are attached to each other; and the design and materials used in the furler drum assembly and how easy it is to disassemble for racing. These differences may have a profound effect on the operative performance of the unit, depending on how well-matched it’s design is for its use in the offshore environment.
For example, the choice of sealed vs. open bearings will depend on how much the user intends to properly maintain the system. Torlon or Delrin ball bearings require periodic flushing with fresh water to retain their self-lubricating qualities. In contrast, carbon steel bearings are stronger, and thus the head swivel assembly may be made lighter and lower profile to overcome the same frictional resistance under static-load conditions. Their drawback is they must be lubricated and sealed from corrosion, so their effectiveness will be critically dependent on the quality of their seals.
Likewise, the performance and longevity of a unit may depend on the choice of materials used in its fabrication. While 316 stainless is most often used for the high-load axial parts of the system, it should be isolated from direct contact with any aluminum alloy, even if anodized. One manufacturer uses titanium for the ultimate in light weight, strength, and corrosion resistance, though these added capabilities are reflected in a higher price. Furler drum designs also vary, some opting for alloy to save weight, some choosing stainless steel for strength. Others opt for an open cage to provide accessibility to line snarls.
While many earlier-generation headstay extrusions were foil-shaped in an attempt to attract dual use by cruisers and racers, their shape in current models has become nearly round. This reflects a realization among manufacturers that only 25% or less of furler owners even occasionally race, and only a quarter of those actually disassemble and remove their furling drums and head swivels to use conventional jibs with luff tapes. Thus, the rounded shape has prevailed due to its easier motion while rolling. One manufacturer has attempted to attract performance-conscious users by incorporating small rib-like “turbulence generators” as part of their rounded extrusion designthese are said to help in reattaching laminar flow closer to the foil.
Besides design and fabrication, a system’s performance may also be critically dependent on the user’s choice of professional versus personal installation. Many systems are provided with detailed instructions and even specialty tools for owner-installation, but the procedure and outcome may depend on the owner’s ability to improvise a non-standard solution to a problem full of nuances only an experienced professional can appreciate. This problem is complicated by the fact that many manufacturers market their products via discount marine retailers. These outlets often have little or no familiarity with installation and use of furling products, leaving the customer with no service resources. While most manufacturers provide generous warranties, and are generally responsive to warranty claims, they are rarely adept at solving individual installation and operation problems.
The chief argument for professional installation, especially for those intending hard use over long offshore passages, is that the furling system has to be viewed as an integral part of the entire rig continuum, according to Tom Wohlgemuth of Chesapeake Rigging, Ltd. “Many of our furling system customers have either tried or have considered trying the installation on their own, but discovered other parts of their rig package that needed attention they felt was beyond their capabilities,” he said. Some product literature makes bold claims on how easy it is to install a furling system (and in some cases it really is easy). However, some professional riggers disagree. “Our experience has shown there are many other rigging factors involved in a proper installation which would escape most of the do-it-yourselfers,” said Wohlgemuth.
II. Sails. In concept, if not in practice, the roller-furled headsail can replace two or more conventionally attached sails of different sizes and cloth weights by simply assuming the desired size through degree of furling. For light air or downwind sailing where maximum sail area is desired, the furler line is released completely to reveal the entire headsail, which is usually a 135% to 150% all-purpose genoa. As windspeed increases and reefing becomes necessary, the furling line is tensioned to reef/roll up successively more of the sail and cleated to prevent unrolling. Unlike when changing headsails of a different luff-perpendicular (LP), the clew angle of the roller-furled headsail remains relatively constant and usually does not require a significant repositioning of the fairlead block. The optimal lead position will change, however, with apparent wind angle, and if moved accordingly can vastly improve performance.
Despite the convenience of furling, a headsail’s effectiveness becomes drastically reduced once it is reefed to about 70% of its area. This is due to the disturbed air flow over the rolled portion at the luff of the sail. The shape of the reefed sail may also be unacceptably deep in the middle due to the highly tensioned foot and leach, although padded luffs can significantly reduce this problem. Most users also report being uncomfortable with the increased chance of jamming a highly loaded furler line in the drum, producing a potentially disastrous situation to resolve in breezy conditions. Thus, in order further reduce sail, the headsail is usually furled completely and a storm jib or staysail set on an inner forestay. In fact, the better-equipped offshore cruisers and singlehanded racers will often have a separate headstay with its own heavy-weather furled jib positioned a little further aft of the primary headstay. Not only will this sail be designed and built flatter for heavier conditions, but its position closer to the center of gravity of the boat reduces lee helm problems, particularly important when sailing under reefed main.
Another feature that reduces the efficiency of furled headsails is their smaller luff length due to the space necessary to accommodate both the furler assembly at deck level and the head swivel at the top of the foretriangle. In order to preserve the proper aspect ratio of the design, this in turn reduces the available size of the sail along the LP.
Given that most voyaging sailors utilize the furling headsail’s convenience of having a jib used in nearly all conditions, the challenge for sailmakers is to design and build a sail that will work well reefed or unreefed, will roll up without excessive effort or binding, and will live in a furled posture for weeks or months at a time without being degraded from overexposure to heat and sunlight. To achieve all this, as well as having the sail last through several seasons and be available at an affordable price, is no small task!
Given the considerable market in voyaging sails, however, sailmakers have been aggressively pursuing new ways to achieve the proper combination of design and materials to meet this challenge. According to Will Keyworth of North Sails, just as with sail development for racing, there has been a considerable effort put into cloth development for furling headsails to optimize the balance between durability, strength, low stretch, UV resistance, and cost. “Cloth types in current use range from traditional woven polyester fabrics that are heavy, stretchy, and have only moderate UV resistance, but are easy to handle and inexpensive, to woven or laminated Spectra fabrics that are lightweight, low stretch, and have excellent flexural and UV resistance but are available at over twice the cost,” said Keyworth. “Aramid fibers such as Kevlar and Technora, which are used commonly in racing sails for their light weight and low stretch, are not desirable for offshore cruisers due to their lower flexural resistance and UV stability relative to equivalently priced Spectra or Dyneema. We try to match the right type of sail for how the customer intends to use it.”
And, according to Bill O’Malley of Quantum Sail Design Group, the design of panels, corner attachments, and reinforcement patches has also become specific for furlers, with features not found on other headsails. “While radial panel layouts are common on most sails, furling sails require a slightly different orientation in the tack panels for load alignment while reefed,” said O’Malley. “Webbed loops for head and tack attachments are better than pressed rings, as they allow the first roll to be tighter without distorting. Patches that are elongated parallel to the luff, leech, and foot align better with the stress vectors, producing longer cloth life and sail shape, especially when reefed.”
Mainsail furling systems I. Mast stowage type. The most common type of mainsail-furling system stows the sail along its luff aft of the mast on a furler similar to those used with headsails. An extrusion that holds the luff of the sail is mounted vertically so that it can rotate close to, yet free of, the aft portion of the mast. The rolled sail is stored either inside the mast itself or mounted aft of the mast and stored in a faired housing which is attached to the mast. The sail is unrolled by its attachment to the outhaul on the boom, and a drive mechanism, be it mechanical, electric, or hydraulic, is used to furl or reef the sail.
While current-generation mainsail furlers have solved early mechanical problems with jammed drives, bunched sails, and difficult installation, they still suffer problems inherent to their design that render them unsuitable for some applications. The additional weight and windage of this type of furling system, while perhaps acceptable on voyaging yachts under 60 feet, becomes unacceptable on larger yachts, as performance can also be greatly reduced by the additional ballast necessary to compensate for the loss of righting moment. Maxi- and mega-class yachts of unprecedented size and performance are now possible due in part to the great strides made in carbon fiber spar development, so adding a furler could negate many of these gains.
Finally, vertical main furlers require a rollable sail that is significantly compromised in its shape efficiency due to its lack of battens, its hollow leach, and its negative luff curve. Shape control of a reefed sail can also be a problem for the same reasons furled headsails are limited when reefed.
Nevertheless, this style of furler remains popular on mid-sized voyaging yachts where the size of the sails is large enough to require assistance in short-handed sail control.
II. Boom stowage types. Probably the greatest recent advances in furling systems have been made in boom-stowed mainsails, in which a furling device is installed in a custom-built boom. The sail is rolled up along its foot, and the halyard controls reefing. While there are potential problems associated with inserting the luff of the sail into the groove track (this approach requires constant precise angular alignment of the boom while furling or hoisting) the overriding advantage over mast-stowed systems is the lower windage and weight associated with hardware being mounted on the boom and not the mast. For this reason, this type of furler is preferred on large voyaging yachts where excess weight aloft can have a considerable effect on performance. Another distinct advantage is that mainsails can assume more conventional and efficient shapes, supported by round, full-length battens which furl with the sail.
The location of the furling hardware on the boom is also attractive to those fearful of jams or other malfunctions which require direct attention because there is no need to go aloft. However, with the full length of the luff to be fed into the mast track when hoisting, there certainly exists a possibility for for the sail to jam. Also, the amount of line handling required when hoisting or reefing the sail using a halyard is far more than that used when reefing is controlled via the outhaul, as in mast-stowed systems. This could be a significant factor at the mega-yacht scale, where mast heights approach 150 feet. Variations on the basic design include different types of luff-feed mechanisms, support for the luff using either a bolt rope or by cars, and the fitting of an outhaul and leech jaw system that transfers the load to the boom when reefed.
Problems associated with luff jams and twisted or bent furling rods still plague some systems, due in part to the greater load compared with luff furlers. And, unlike jib furlers, manufacturers recommend professional rather than owner installation due to the additional complication and critical adjustments necessary for smooth operation of these systems.
In summary, many problems have been overcome in furling-system designs, which makes this method an attractive and safe alternative to traditional methods of sail handling. There are thousands of relatively trouble-free jib and main furling systems in use today that span the gamut from casual daysailing to serious offshore passages.
Continued development in jib furlers will no doubt concentrate on installation ease, while mainsail systems will seek improvement in nearly all aspects of design, fabrication, installation, and operation.
Dobbs Davis is the production manager at J. Hamilton Yacht Co. in Annapolis, Md.
