In-boom furling: looking at the pros and cons
The engineering of in-boom reefing systems has been considerably refined over the years and today’s systems are much better than early iterations. Even though this remains an expensive option, it’s one a growing number of boat owners are adopting.
Key advantages include one person being able to handle the mainsail entirely from the cockpit, especially if powered coachroof winches are available. There are no lazyjacks to snag battens and no messing with the miles of reefing pennants that are needed for slab reefing.
Yet these systems don’t need a sail with the hollow leech and very flat cut that’s necessary for in-mast furling. They therefore have the potential to offer similar sailing performance to boats with conventional slab-reefed mainsails.
Given how neatly the sail is furled, and the absence of highly loaded reef points in the leech, in-boom systems also have potential to increase a sail’s lifespan.
Unlike in-mast furling, all the mechanical elements can be reached from the deck, which facilitates inspection, service and repair, while minimising weight aloft.
If the system does fail, the sail can be dropped and secured around the boom in the same way as a conventional mainsail without lazyjacks. However, the lack of luff slides or cars to keep the front of the sail under control can make this a much more difficult task than for a conventional cruising yacht mainsail.
POTENTIAL PROBLEMS
Despite the obvious advantages there’s still a lot of bar-room discussion about the pros and cons of in-boom furling. Most issues are caused by problems with the initial set up, or by incorrect handling procedures.
It’s critical to have a correct lead for the sail’s luff tape as it transitions from the rolled up position within the boom to the track on the aft face of the mast. To achieve this the boom must be held at exactly the correct vertical angle to the mast when the sail is hoisted, lowered or reefed.
If the angle of the boom is wrong the luff tape walks backwards or forward on the mandrel.
If the outer end of the boom is too low the sail moves forward, whereas if it creeps aft the boom is set too high. At first sight the latter may appear to be a less obvious problem, but it risks ripping the luff tape from the sail. I’ve seen owners blame sailmakers for this, when clearly the issue was one of initial set up.
For most boats this magic angle between mast and boom is in the range of 86-89°. Some systems are set up with a solid vang that holds the boom permanently at the correct angle, but this means twist in the sail can’t be controlled. Others have systems that enable the boom to be reliably, quickly and repeatedly returned to the correct level.
Most manufacturers include a suitable system when supplying their equipment, although oldschool systems, without a gas vang, might simply rely on a mark on the topping lift. If the kicking strap is then pulled on tight the boom will be at the correct angle, although creep and stretch in the lines have the potential to make this solution a little hit and miss.
Boats fitted with a rigid vang that supports the boom may have a Dyneema strop of exactly the right length that stops the boom rising higher when the correct angle is reached as the kicking strap is eased.
“Furling booms are heavier than normal booms so it might be that the existing vang is a bit too weak for the new furling boom, which can lead to it ‘dancing’ while trying to furl the sail,” cautions Johan Mulder, the CEO of Romar Leisure Furl. He also advises using extra thickness in the leech to help the sail furl neatly. “This can be in the form of a sacrificial Uv-strip, which then obviates the need for rigging a boom cover to protect the sail.”
After fitting in-boom furling it’s clearly important to spend time checking and, if necessary, refining the set up. It’s worth getting the sailmaker and rigger who installs the system to collaborate on this aspect and demonstrate how to use the system as configured for your boat on a sea trial.
After this initial set up and handover it’s also worth practicing on your own so that any queries can be dealt with before undertaking a major trip.
REEFING PROCESS
Perfect set up, however, is no guarantee on its own that the system will be trouble free. The process of using in-boom systems is not complex, but the correct procedures must be followed every time.
As already mentioned, for boats with adjustable vangs the boom must be set at the correct height before undertaking any operation. Then when hoisting the sail (or letting out a reef) a little tension must be kept on the furling line to avoid the luff tape sagging in the gap between the mandrel and the bottom of the mast track. Equally, when lowering the sail a little tension must be kept on the main halyard – in effect, the sail is pulled down, rather than dropped.
If the system works well in flat water, but not in a seaway, this may be indicative of the end of the boom moving up and down and therefore not remaining at a constant vertical angle to the mast. The topping lift may therefore need to be tensioned more tightly against the kicking strap, or the vang’s gas spring may need to be replaced, so that the boom is held more solidly in position.
A lot of systems offer control of the draft in the bottom third of the sail, although this is rarely achieved with a conventional clew outhaul. A common method is to rotate the mandrel just enough to wind in some material from the middle of the foot, but not at the tack or clew, thus flattening the middle of the lower part of the sail.
In theory in-boom systems can give an infinitely variable amount of sail area. However, in practice, reefing down to each batten position gives a better shape for a sail with full battens.
DISADVANTAGES
The downsides of a well-set up system appear to generally be fairly small, with the exception that some systems can’t be used to reduce sail when sailing downwind. Rounding up in a big sea to bring the apparent wind forward of the beam is never fun, so in my view the lack of ability to reef a cruising yacht when running downwind is a serious weakness.
In addition, hoisting and lowering sail may take longer than with conventional systems.
This process is best done with a view of the sail, especially the gooseneck area, which may be problematic for single-person operation on boats with fixed sprayhoods.
Batten compression on the mast track can create friction and accelerate wear of the luff tape, although some systems are designed to minimise this problem. Arguably a bigger issue is that in-boom reefing is still produced in small volumes, even by marine industry standards, and is therefore expensive. This is especially true for the best kit that’s engineered to be robust, snag free and look good.
Owners looking at retrofitting in-boom furling will also need to factor in the cost of a new mainsail. This needs to be fitted with a luff tape that fits the internal diameter of the mast track, while a different amount of luff round may be needed compared to a standard mainsail. The foot also needs to be cut to match the precise angle between the boom and mast and battens must lie parallel to the mandrel.
WHAT’S ON THE MARKET? MAINFURL
This newly launched system has a V-shape carbon boom and is available in five sizes for boats of 40-70ft. The Danish company, whose team has 50 years of experience with in-boom systems, says it paid attention to every detail to make the system “both elegant and practical.”
The prototype was tested on an Xc45 using the boat’s electric coachroof winches. When hoisting, one turn of the furling line can be held around a winch to give the necessary resistance and the same can be done with the halyard when lowering the sail.
Following the trial, sales and marketing director Peter Westfal told Yachting World: “We are very happy with the result [and] all features were working like we expected.”
An electric motor can be built into the mandrel to provide a more automated solution, with the endless manual furling line retained as a backup.
A Dyneema strop of exactly the right length is provided to hold the boom against the gas vang at the correct height.
The gooseneck fittings and luff track are designed for easy retrofitting to existing carbon and aluminium masts.
Neat features include grooves for attaching both sail cover and cockpit awnings. The mandrel is raised at the outboard end of the boom, which gives a more appealing aesthetic, as the aft end of the boom doesn’t appear to be raised as high.
On the downside, Westfal tells me the system can’t be used to furl when sailing downwind, but that it is possible on a reach if mainsheet and vang are eased to take the pressure out of the sail.
Price: £33,600 for a 45ft yacht. www.mainfurl.com
SCHAEFER MARINE
Massachusetts-based Schaefer Marine engineers its systems using machined aluminium components, which are sleeker and lighter than castings, but more expensive. A key benefit of this system, which was originally developed in 2001, is that reefing can take place on any point of sail, including with the wind aft. This is achieved with a ‘scoop’ that leads the luff tape into a patented articulating mast track that maintains alignment with the gooseneck.
The furling drum is mounted at the aft end of the boom to free up space for a neat arrangement at the gooseneck. The downside is this furler position adds a little friction, but that’s unlikely to be a problem on a boat with electric winches. To minimise friction elsewhere, oversized dual race Torlon bearings are used at each end of the mandrel.
A heavy duty fixed rigid vang ensures the boom is always at the correct angle for consistently reliable operation at the expense of losing control of mainsail twist.
The system is available in two versions, Beta and Gamma, to suit maximum luff lengths of 13.4m (44ft) and 16.4m (54ft). The UK distributor is Warsash-based Sea Sure.
Prices ex VAT: Beta US$13,800 (approx £11,000); Gamma US$19,900 (approx £16,000). www.schaefermarine.com; www.sea-sure.co.uk
LEISURE FURL
This well established brand is part of Californiabased Forespar and has produced thousands of systems for boats from 9-24m (24-79ft), plus custom units for yachts up to 100ft. The company says furling can be carried out when sailing downwind, with the boom sheeted in to 45° to move the sail away from shrouds and spreaders. The furling drum is on the front of the mast and incorporates a manual override option.
Leisure Furl produces eight models for boats from 27-70ft in aluminium or carbon.
Average price ex VAT for a 45-footer: US$16,000 (approx £13,000). www.leisurefurl.com
ROMAR LEISURE FURL
This Dutch company was a Leisure Furl distributor, but now offers its own product in carbon or aluminium construction, with most being aluminium for yachts in the 45-80ft bracket. These are fabricated from shaped aluminium plates, bonded with epoxy resins using techniques developed in the automotive and aerospace sectors. “This switch was done to get rid of any corrosion and to create a stiffer boom,” says CEO Johan Mulder. It also reduces costs by around 50% compared to a carbon boom, although a carbon fibre mandrel is used for extra stiffness. Manual, electric or hydraulic operation is available.
Prices start from €18,000 for a 45ft yacht. www.romarmarine.com
FURLERBOOM
This is a 20-year-old Danish company whose products have been fitted to a wide range of yachts, from production cruisers to top quality designs. Booms are produced in fibreglass, carbon and composite with a carbon appearance, for yachts from 36-70ft. They incorporate cockpit lights – white for use in port and red for night sailing – on the underside of the boom.
Guide prices ex VAT for a 45ft yacht: fibreglass €27,432; carbon €41,208. www.furlerboom.dk
OTHER BRANDS
Other companies that offer production-made inboom reefing systems include:
Danish spar manufacturer John Mast which produces the Hi-low reefer system in three models to suit boats from approximately 6-12m (20-40ft). This costs €8,292 for a 40ft yacht. www.johnmast.dk
Profurl, part of the French Wichard Group, has a wide range of in-boom systems for boats from 5-18m (17-59ft) with aluminium spars. www.profurl.com
Sailtainer is a long-standing brand, with more than 1,000 units produced, and is sold in the UK by Jeckells. The furling drum is at the aft end of the boom and the system is available in sizes to suit luff lengths from 5-24m (16-79ft). www.jeckells.co.uk
Hall Spars, part of the North Technology Group, produces five all-carbon models, catering for yachts from 40-100ft. The system’s geometry allows the mainsail to be furled or reefed while sailing downwind. Manual, hydraulic and electric drives are available. www.hallspars.com