Handling the mainJan 1, 2003
Handling the mainsail can be a challenge for a short-handed crew. Because the main is such an important part of the sail plan, the right system for hoisting, reefing, and furling it should make things easier for voyagers.
There are several approaches to solving this problem. The hardware solution includes various types of furling apparatus that 1) roll the sail inside the mast; 2) are contained within a housing that is retrofitted to the aft portion of the mast; and 3) roll the sail on or in the boom. The design and engineering details of the products offered by various manufacturers concentrate on solving the inherent problems of chafe, strength, weight, corrosion resistance, and aerodynamic efficiency. Making the proper choice from among these options involves a careful analysis of the type and size of boat, as well as its intended use while under sail. It is important also to remember that installation of any furling system is usually best left to a rigging professional, as there may be significant modifications to the spar, rigging systems, and deck layout necessary to ensure its effective use.
If a furling system does not seem affordable or appropriate, there are a few non-furling solutions that assist the short-handed crew in manually reefing or flaking the sail. These are considerably less expensive than furling systems and are simpler to install and maintain. This approach includes the Dutchman system and the various styles of lazy jacks.
It is important to recognize that any choice of mainsail handling hardware, whether as sophisticated as a furler or as simple as a set of lazy jacks, is just one component of an integrated system that must combine proper installation, sail choice, and technique.
In-mast furling systems
The virtues of having a furling system that resides within the spar seem obvious: the apparatus is contained within the section walls and is thus aerodynamically clean and presents an aesthetically uncluttered appearance. The sail completely retracts within the spar and is therefore protected when furled from exposure to the damaging elements of sun, salt, or wind chafe. Upon exiting from the furler, the luff of the sail is in continuous contact with the mast, and thus doesn't rattle or vibrate as luff slides often do, nor does it create excessive luff wrinkles due to loose halyard tension. Reducing sail is a relatively simple matter of slackening the tension of the outhaul and furling in the sail, with no alteration of halyard tension required. And, if properly installed, it may even be possible to furl the sail without having to go head-to-wind.
A typical in-mast furler is shown on page 72. These systems will often have ports cut through the mast sidewall to allow for access to the sail feeder and the tensioner for the furling extrusion. The choice of drive mechanism, which is positioned below the gooseneck, is often a distinguishing characteristic of mainsail furler systems, with manually operated line and screw-type drives common on boats less than 50 feet long, while electric or hydraulically powered systems are necessary to handle the loads seen on larger yachts.
To ease furling of the sail, the mains for these systems will have zero or even negative roach, unless supported by vertical battens.
While they do ease sailhandling, there can be drawbacks to in-mast systems. The first and perhaps foremost is their expense: in opting for an in-mast system, the customer is often faced with purchasing an entire spar package, which may include spreaders, standing rigging, and electrical wiring and attachments in addition to the spar and furler itself. This may become a significant total expenditure, ranging from $5,000 for the smallest systems to more than 40 times that figure for customized systems aboard megayachts. Because of this, it's more common to see in-mast systems fitted to newly constructed yachts rather than retrofits.
Another common objection to the in-mast furlers is the potential for them to jam while either furling or unfurling the sail. A sail that is jammed in position, extending partially out of the mast and resisting attempts to raise or lower it, could be disastrous for the short-handed crew. The sail, the spar, and even the crew risk injury when having to sort out such a mess during extreme conditions, especially when maneuverability may be hampered in confined waters. Most systems on the market today, however, represent third- and even fourth-generation design and engineering, so that, with proper maintenance
and prudent use, jams are becoming relatively rare
Besides troubleshooting, maintenance on mast furlers can also involve some time in the bosun chair to examine the luff extrusion's bearings at the top of the mast. On larger yachts that must handle considerable loads on the sail, the bearing design becomes important for smooth operation, especially while reefing. Some systems have sealed bearings, while others have open designs that allow for flushing with fresh water.
There are also concerns over possible negative effects mast furlers have on boat performance, with an increase in pitching moment and a decrease in righting moment suspected due to the added weight aloft. The reduced righting moment will mean greater keel weight and/or depth necessary to achieve the same stability, which in turn reduces cruising options in shallow waters. And Scott Alexander of Sail Systems
points out another consequence of pitching not often considered: "When at anchor or at a mooring, this enhanced pitching may be noticeable and especially annoying when the added boat motion is from passing vessels' wakes or swells."
For the ocean voyager who chooses to adopt an economical main furling system without changing to a new spar, there are several options available in hardware that fits on the aft portion of the mast section. These retrofitted furlers perform in a fashion similar to the in-mast varieties. Note that the apparatus is attached to the mast by rivets through the thin aluminum housing material that encloses the furling unit. For additional strength, some designs rely on attachment to the mast section's luff groove.
While it may be attractive to acquire the easy handling characteristics of a mast furling system using an existing non-furling spar, it is important to realize that its installation could be as expensive and complicated as rigging and stepping a new mast. "Many people are surprised at the all-up cost of installing a mast furler," said Tom Wohlgemuth of Chesapeake Rigging in Annapolis. "Not because of the equipment cost, but the additional expense of customizing the new system to the boat." Typically, the procedure involves several steps: removing the old mast and rigging; replacing any unusable parts from the old standing rigging, halyards, and mast accessories; fitting and assembling the furler unit and rigging on the new spar and stepping it in the boat; modifying the deck layout; attaching any wiring and reassembling the boat's interior; and tuning the spar and adjusting the furler system. Wohlgemuth continues: "We usually advise customers that the all-up cost of installation can be as much as the price of the furler. But it's still significantly less than a new in-mast system." Moreover, because of the loads associated with the main halyard, outhaul, and vang on large yachts, the upper effective height limit for this type of external system is about 55 feet. "We installed a behind-mast unit on a customer's Swan 57, and that was definitely pushing the limit," said Wohlgemuth.
Other factors to consider with both retrofitted and in-mast furlers are whether or not there is a groove in the extrusion and an additional sheave at the top of the unit for use with a storm trysail or spare mainsail. This could be a valuable asset for situations in which the mainsail furler is inoperable, allowing you to hoist a spare main or even headsail in the available groove. The spare halyard sheave could also be put to use as a topping lift, if there is no solid vang available to hold the boom up.
And, finally, though it has no bearing on the operation of the furler, in many cases the color of the mast will not be the same as that of the furler housing. So, for aesthetic reasons, painting the housing, the mast, or both will be necessary for an acceptable match.
The problems with performance loss described earlier due to the added weight and windage of mast furlers prompted a search for yet another furling method. According to Jacques Swart of Hall Spars, boom furling "is actually an old concept that started with roller-reefing booms of a generation ago." Boom furlers have since been developed over the past several years that furl or flake the mainsail into a hollow boom when the main halyard is lowered. The unused portion of the sail remains encased within the boom and is thus protected from wear and weather in the same manner as a mast-based system. To furl, the halyard is lowered and the sail is brought down with a drive unit that is powered electrically, by hydraulic drive, or manually. Most remotely powered systems have a manual override feature. Manufacturers of some systems claim that furling can be accomplished at any point of sail, although procedures will vary.
Besides the lower center of gravity on the sail plan, another attraction of boom-based furlers centers primarily on the mechanism's position closer to the deck and thus greater access to the user than with a mast-based system. While modification to the gooseneck is often necessary, installation does not involve unstepping the mast, and maintenance and troubleshooting can be performed without a bosun chair. Some models allow for continuous reefing capability, while others have a system that resembles slab reefing: an adjustable outhaul mechanism is hooked into a reef point at the leech while a similar jaw apparatus is used at the luff. Besides taking the loads off the system and extending the life of its bearings, this helps keep the sail's full-length battens properly aligned and tensioned for optimal sail shape.
While not as common as with mast furlers, there are retrofit kits available to convert an existing boom to accommodate a furler. This approach may be more economical than purchasing an entirely new unit, but considerable modification may be necessary, and most non-furling booms will not have the proper dimensions to house a furled sail.
The main drawback to boom furlers is that every one must rely on the main halyard to raise and lower the sailusually three or four times the amount of line and many times the load compared with using the outhaul on a mast-based system. Not only does this increase the opportunity for chafe on the sail and the halyard, but, if the halyard is not accessible from the cockpit, then an agile, knowledgeable, and often physically robust crewmember must go forward to operate it. Unfortunately, this can negate some of the furling system's basic tenets for simplicity, safety, and ease of use, at least for manually powered systems. (For larger vessels and megayachts, on which most lines are electrically or hydraulically powered anyway, this may be less of a concern, since the controls can be positioned anywhere.) In addition, the user will have to be as attentive to halyard tension as to sheet tension against the furler line load during furling. Boom angle can also be critical for both feeding into the luff groove during hoisting and rolling onto the mandrel while furling or reefing. Some manufacturers provide with their boom unit a vang system pre-set for this proper angle.
Sails and performance
There is considerable debate among ocean sailors, sailmakers, and spar and furling manufacturers about the relative merits and deficiencies of furling systems' effect on boat performance. The principal arguments center on the trade-off of a mast furler's ease of use against its sail's smaller area and the weight aloft added to the spar. The effects of both have been regarded as significant enough to drive the advent and development of boom-based furlers, which feature more conventionally shaped sails contained within a hardware package that has little effect on a boat's righting moment. The ferocity of this debate makes it worthwhile to take time to critically examine each effect.
There can be no argument that the mast furler's mainsail is not optimally shaped to drive a performance-oriented boat. The zero or even negative roach deprives the sail of its driving force on the leech, and upwind performance is, therefore, seriously compromised. The standard mainsail area of a CandC 40, for example, is 381 square feet, while a mast-furled sail for the same boat is 317 square feet, or 17% less, with six square feet of negative roach. Vertical battens have been devised to allow for a minimal amount of positive roach, but the added area is not significant and often compromises the operation of the furler with bulkiness added to the rolled sail. With a loose foot and adjustable outhaul, however, an in-mast furled sail can often be readily shaped even when reefed.
In contrast, boom-furled mains can be designed and built as more efficient and powerful sails, with their full battens and positive roaches giving more sail area. In either case, it should be noted that mainsail shape can also be controlled to some degree with mast bendmore bend flattens the sail. Most furlers will, however, require the mast to be straightened during hoisting or furling operations.
It's also important to remember that the performance effects of the two sail types must be considered within the context of other aspects of the boat's design. In particular, a boat that has a short keel, heavy displacement, and small sail plan probably will see little difference in upwind performance. However, particularly among the larger custom yachts, the current trend in design is toward performance. "Our clients don't even consider mast furlers, not so much because of the weight aloft, but because they want the more efficiently shaped mainsail," said Bill Tripp, Jr. of Tripp Design. "For boats with a displacement-to-length ratio that approaches those of race boat valuesaround 110 to 120this is significant. But for the boats that are in the 200 range, it probably isn't."
"Design and construction is fairly simple for furling mains, with use of a tightly woven, flexible cloth [either Spectra or Dacron] which doesn't rely on finish resins for its strength," said Jonathan Bartlett of North Sails. Shapes are fairly flat, and some additional reinforcement is added to the leech and foot panels for strength while the sail is reefed in the mast. "All the panel seams are treated with Tuff-Seam, a liquid plastic which helps protect against chafe," said Bartlett.
The argument for rejecting mast furlers due to the added weight aloft may also be a strong one for the performance-conscious ocean sailor, but according to Tripp the difference in weight "is about the same as that between a carbon and aluminum spar." While this effect can be important for larger sloops and cutter-rigged yachts, where the dimensions of the mast must be quite voluminous in order to house the sail and furler, it may have little effect on smaller craft. Seldon Mast AB of Sweden, builders of the Furlex main furling and reefing system, calculated that there is only an 8% decrease in righting moment, which translates to 1.6° at 20° of heel, for a Moody 36 auxiliary sloop.
Marginal for small vessels
This minimal difference for smaller yachts was supported by a Swedish study published five years ago by Pa Kryss and Till Rors. Two identical Comfortina 32 sloops were sailed against one another to evaluate the performance difference between a boat with a mast-furled main and a standard main. The boat with the furler had a mainsail fitted with vertical battens and 5% less area than the standard. Over two series of trials, one in winds of 18 to 22 knots and another in seven to nine knots, the two boats were sailed upwind four times for 0.75 and 0.82 miles, respectively, and elapsed times recorded for each. The average time difference between the boats worked out to be only 15 to 20 seconds, or about 1.45%, with the furler main being slower in all but one race.
Nonetheless, these differences may not be so unnoticeable on larger boats, according to Goetz Marine Technologies (GMT), which has built the largest number of carbon mast furling systems to date. "When upgrading the aluminum spars on Bob Pirie's 1982 Hinckley Sou'wester 50 ketch Irene to carbon with furlers, we saved 346 lbs. in the mainmast, and 61 lbs. in the mizzen," said Ben Sprague of GMT. "Bob has said that he has noticeably less heel under sail and can carry the full main into much higher wind speeds than he could before." GMT is also a regular supplier of carbon spars for many new Hinckleys.
The offshore sailor must ultimately define what type of sailing he or she plans to do before choosing the appropriate sailhandling system. In situations where the boat will be sailed by a minimal core of experienced crew, a main furler may not be a suitable option, and lazy jacks or a Dutchman system could well be the best choice. This may also be the case for the world voyager who is concerned about troubleshooting complex mechanical systems far away from adequate service support.
However, for the shorthanded ocean or coastal sailor who must be operable under sail in all conditions, a mainsail furler may greatly increase his or her efficiency and safety. If the trade-off of extra weight can be justified against performance, such as with heavier vessels, then a mast furler may be the right choice. If this compromise cannot be made, then a boom-furled system (or no furler system at all) may be the best decision.
Regardless of choice, Paul Boyce of Hood Spars points to mainsail furlers' widespread acceptance 10 years ago within the ocean cruising fraternity following Dodge Morgan's successful solo circumnavigation aboard his Little Harbor 60 American Promise. Since then Hood and many others have nurtured development with the underlying goal of making mainsail furlers as easy and reliable to use as jib furlers. n
Dobbs Davis is the production manager at J. Hamilton Yacht Co. in Annapolis, Md., and the U.S. correspondent of the British racing magazine Seahorse.