sailboats with in mast furling

Yachting Monthly

• Digital edition

Mainsail furling systems: an expert guide

• Graham Snook
• December 21, 2020

Some sailors swear by mainsail furling systems, others swear at them. Graham Snook looks at way to keep your furling mainsail in check

In-mast furling mainsails (left) have evolved significantly, and vertical battens allow more roach and better sail shape. Credit: Graham Snook

Mainsail furling systems have come on a long way.

Sails no longer need to be wrapped around a boom, nor does an in-mast mainsail need to be the hollow-leached, baggy triangle we first saw decades ago.

Furling mainsail systems can now offer more sail area than a traditional slab-reefed mainsail.

Be that as it may, every slab-reefed sailor knows a horror story about in-mast or in-boom furling that is enough to make them steer well clear, while those that have furling mains wouldn’t put to sea without one.

There is little doubt that furling mainsails are gaining in popularity, even for serious offshore cruising boats.

Get mainsail furling wrong and it can lead to costly and potentially dangerous problems. Credit: Graham Snook

In 2018, 38% of boats sailing round the world in the World ARC had furling mainsail.

Hallberg Rassy reports that almost all new owners buying boats over 40ft opt for furling mainsail systems, with Discovery reporting a similar trend.

So has the reputation of furling mainsails been unfairly tainted, and are they more prone to user error, or have the systems ironed out the glitches?

Whether you’ve got a furling main on your own boat, or if you’ll be using one when you charter, it’s worth knowing how to avoid the pitfalls of furling mainsails.

How do furling mainsail systems work?

In an age where we expect everything just to be simple and to work, letting off one line, and pulling another to make the mainsail appear or disappear sounds appealing, but what is the best way to furl the mainsail?

Is there a correct way to do it?

‘Carefully,’ replies Jeremy White,of Elvstrøm Sails UK. ‘They’re mechanical systems and they need to be operated correctly.’

Whether you have in-boom or in-mast, they both work on a similar principle which anyone with a furling genoa will be familiar with.

Inside the mast is an aluminium foil that takes the luff of the mainsail, and in a boom a mandrel takes the foot of the mainsail; both the foil and the mandrel revolve to roll up the sail.

A lot of issues with in-mast furling are caused by the sail not furling properly inside the mast and the furl being too bulky or the sail rubbing on the inside of the mast.

Many in-boom problems are caused by an uneven furl with the sail bunching at one end or the other.

There are a number of issues to look out for with each system to ensure stress-free furling.

Different options

If you’ve bought a new boat that was ‘good value’ and it came with sails, question how good those sails really are.

Many original Dacron sails are built to a price that will get you on the water and get you sailing, but they may not be built for longevity or performance unless you’ve specified them and know what you’re getting.

There has been much advancement in furling mainsail design, improved materials, vertical battens, and increased sail area.

Many new furling mainsail systems present a larger sail area than that of a conventional slab reefing sail.

But what should you be looking for when buying a new sail?

‘Whichever sailmaker you choose, get the highest quality material you can afford,’ advises Jeremy.

It’s a false economy to buy cheaper sailcloth as it will stretch and you’ll be left with a baggy sail after a few seasons.

For example, the luff of laminate sail (on a 45ft yacht) might only stretch 15mm over its lifetime, but on a polyester sail that might be as much as 15 cm.

That excess sail has to roll up in the same space as did when it was new.

For those wanting maximum sail area, and sail support, full-length vertical battens are the way forward.

These support the leech giving a good full roach, and importantly, they support the sail over its full height which gives it rigidity while it’s being furled, whereas shorter, vertical roach battens can leave the sail unsupported at their base causing furling problems.

For those without the budget or desire for a battened sail using modern materials, a sail with a hollow leech still offers many advantages over a slab reefing system, namely ease of reefing, the ability to set exactly the right amount of sail, and the simplicity of stowing, even if you do lose some power from a smaller sail area and a less perfect aerofoil sail shape.

If you’re having new sails made consider getting them silicone-coated.

This helps the sail slide over itself making the furl inside the mast tighter.

In-mast furling

It may be a simple system, but how you unfurl and furl the main will help avoid problems.

If you were to look down from the top of the mast, the foil usually rolls onto the foil in anti-clockwise direction, that is, the unfurled sail comes off the starboard side of the foil, though it’s worth checking on yours.

This is the key to getting in-mast furling to work correctly; trying to furl on a port tack drags the full height of the sail over the side of the mast slot, adding friction where there shouldn’t be any.

Furling on starboard tack obviates most of this friction while you furl.

Full-height battens support a larger roach, but make the furled sail more bulky. Credit: Graham Snook

Whether letting the sail in or out, the first thing is to release the backstay (to straighten the mast so the foil doesn’t rub) and put the boat on a starboard tack – with the wind slightly forward of the beam – this is so the sail feeds cleanly into the mast and around the furler inside.

Unfurling the sail is usually pain-free if the sail was furled correctly.

With the yacht on a starboard tack and the wind forward of the beam, release the mainsheet and vang.

Ensure the furling line is released then pull out the sail using the outhaul.

Ease the outhaul as your furl so the sail doesn’t flog but isn’t loaded up either. Credit: Theo Stocker

You shouldn’t need to control the furling line as there should be no pressure on the sail, even on a windy day.

If you intend to be reefed, however, don’t let it run unchecked. When the right amount of sail is out, make off the furling line. If you’re reefed, tension the outhaul to give the sail the correct shape (flatter in stronger winds and when close-hauled) then set the mainsheet and vang and away you sail.

• Release the backstay (if you have one)
• Put the boat on a starboard tack – with the wind slightly forward of the beam
• Release the mainsheet and vang
• When the right amount of sail is out, make off the furling line
• Tension the outhaul to give the sail a correct shape, then sheet in

To furl the sail, after letting off the backstay and putting her on a starboard tack with the wind slightly forward of the beam, let off the mainsheet and then ease the outhaul a little and start to furl.

Always look at the sail as you’re furling – you’ll be able to notice issues as they happen and not after you’ve wound an inch-thick clump of sail through a half-inch gap.

Having different coloured lines can make things simpler for your crew. Credit: Theo Stocker

If your sail has full-length vertical battens ensure the first batten is parallel with the mast when it enters, and if reefing, leave a batten just outside the mast groove.

Keeping too much tension on the outhaul will drag the foil aft in the mast, bending it and causing the sail to rub against the inside of the mast, creating friction.

Once you’ve taken the slack out of the sail, ease the outhaul and take in on the furling line again.

Try not to let the sail flog as this also bends the foil and causes more friction.

Repeat the ease-furl process until only the UV protection strip is showing.

Sail on starboard with wind forward of the beam for easy furling. Credit: Theo Stocker

If you have laminate sails, and they have been furled away wet, try to dry them at the first opportunity.

If you’re having problems furling using the lines, don’t be afraid to go to the mast with a winch handle and furl the sail at the mast.

Try it one day, it is remarkably easy.

If you’re having to do anything different, such as raising the boom or chanting a prayer to the god of furling fails, it’s worth looking at your system in detail for problems.

• Release the backstay
• Ease the outhaul a little
• Take in on the furling line
• Keep easing the outhaul and taking in on the furling line
• Furl the sail until the UV strip is showing at the mast

Problem solving

If furling the right way still isn’t working for you, there are a number of things to consider…, 1. understand your system.

First to check is to have a look inside your mast at which way your system should furl.

If your furling system has the option, put a winch handle in the furling mechanism at the mast and turn it the direction indicated to make sure the sail is going into the mast in the correct direction.

Clicking over the ratchet at the mast before it’s time to furl will ensure it always rolls in the right direction.

2. Assess your sails

The biggest cause of problems is the sail itself – how old it is and the material it is made from.

Stretch in the cloth makes baggy sails, which furling systems will happily munch on.

Furling mainsails are cut flatter than conventional slab-reefing sails as accommodating the belly of the sail is problematic.

An old or baggy sail may cause jams, as will creases from not enough halyard tension. Credit: Theo Stocker

Some older furling mains may have be made with an inappropriate, fully-bellied shape.

If your polyester sails have a deep belly, think about getting new ones as you’ll be fighting a losing battle.

As the belly folds, it doubles the thickness of the furl, causing unsightly and inefficient creases at best, and hideous sail jams or rips at worst.

3. Adjust halyard tension

Excess halyard tension can also cause the fabric to bunch up; vertical creases at the luff cause the sail to fold over itself.

Vertical creases at the luff reveal too much halyard tension, and potential for more snags. Credit: Theo Stocker

To resolve this, release the halyard until you have horizontal creases at the luff, then add just enough tension to remove them, though you may need to adjust this when underway.

4. Check the backstay

While the mast is bending, the foil inside it remains straight; the furled sail will bind at the apex of the mast’s bend.

If all of this fails, it’s worth calling a rigger to check the foil tension.

If this has gone slack, as you furl the foil will bend and rub against the mast.

5. Smooth it out

The next thing to look at is reducing friction.

As is often the case, the lines to your furling gear and outhaul are led through various fairleads and blocks across the deck and up the mast.

Move deck organisers to give slacker turning angles. Credit: Theo Stocker

Make sure all the angles they have to go through are a wide as possible – consider moving them if not – and all blocks and sheaves are running smoothly.

A good wash with fresh water and a squirt of dry lubricant can work wonders.

In-boom furling

Not a new concept, in-boom furling is an elegant solution, but brings its own challenges.

Unlike in-mast furling, in-boom systems can be retrofitted in place of conventional slab reefing.

For an in-boom furling system to work efficiently, however, it has to overcome a number of problems.

To start with, have a crew on deck to watch the sail as it furls to spot any issues. Credit: Advanced Rigging and Hydraulics

First of all, the sail has to be led from the boom to the mast, but there needs to be space for the bearings for the central mandrel and the boom’s gooseneck fitting, so the whole sail has to move aft along the boom.

To combat this, many in-boom systems have a protruding track on the trailing edge of the mast, while other units have the reefing mechanism at the aft end of the boom, or sometimes you’ll find a combination of both.

Whatever the system, there is usually a flexible feeder to guide the sail from the boom and feed it into the mast track.

The furling drum at the outboard end of the boom brings the main closer to the mast. Credit: Advanced Rigging and Hydraulics

Another issue with in-boom furling is the bolt rope, as Andy Cross from Crusader sails explains.

‘The sail has to use a bolt rope, and with it comes friction. Unlike a furling genoa that may only be raised and lowered once a season, the mainsail is nearly always used so the luff tape has to be reinforced.’

Any wear or damage to the bolt rope also requires a new bolt rope along the full luff of the sail, as any repairs would soon wear through and increase the friction.

The necessary extra reinforcement at the luff brings with it another problem: extra cloth thickness at the front end of the sail.

When reefing, stop when a batten is just above the mandrel, then take in on the furling line. Credit: Graham Snook/Yachting Monthly

As the sail rolls around the mandrel there is more sail material at the luff than across the rest of the sail.

The solution?

To slightly raise the aft end of the boom, allowing the extra sailcloth at the luff to roll at a rate that matches the leech.

The angle from the mast to the top of the boom has to be 87° to the mast, 3° above perpendicular.

The full-length battens in the mainsail help stabilise the sail as it furls and the batten pockets have been attached to the sail to match the mandrel angle.

It’s the thickness of cloth at the luff and the battens that make the correct boom angle the most important part of the system.

The necessary bulk of the boltrope makes the boom angle critical.

Get that right and your life suddenly becomes a whole lot easier.

It’s essential to mark the vang when the boom angle is correct.

Some owners choose to make a strop, running next to the vang, out of a low-stretch material like Dyneema, so the topping lift can be pulled taught and the strop prevents the boom raising higher than it should.

When marking or limiting the boom angle, it must be easy for any crew to see, by day or night.

How to get it right

1. prepare to set sail.

‘Before raising, lowering, or reefing the mainsail,’ explains Kim Petersen, Elvstrøm Denmark’s in-boom sail specialist, ‘get into the habit of always releasing the backstay tension – this will successfully straighten the mast and takes any flattening tension out of the sail – and then making sure the boom is at the correct angle – this is extremely important.’

Be careful with electric winches not to over-tighten halyards. Credit: Graham Snook

To raise the sail, after slackening the back stay and adjusting the boom level, point the boat into the wind, release the mainsheet and take up on the mainsail halyard, making sure that the furling line can run free as you hoist the mainsail.

Once set, increase the halyard tension until the horizontal creases at the luff have just gone.

2. Reducing sail power

If you don’t need full sail, only raise the sail until the nearest batten is at the mandrel.

Rather than being able to reef at any point, where the lower battens are fitted, the sailmaker will have reinforced the sail to take the clew loads.

Not reefing at these points means an area of unreinforced leech could be required to take a load it was not designed for.

Each batten represents a reefing point. Credit: Graham Snook

You’ll end up with fullness at the foot of the sail and a stretched leech, or a damaged sail.

If you need to flatten the sail, for better pointing or in stronger winds, take in on the furling line without adjusting the halyard tension.

This will give the same result as using a cunningham to tighten the luff.

Furling the main

When lowering the sail, release the backstay and set the boom at the correct angle.

It’s then best to take all the pressure off the sail by heading into the wind.

It doesn’t matter if the sail is flogging; the battens keep the sail rigid and support it as it furls.

If there is any pressure on the sail, this will cause it to furl unevenly.

With in-boom reefing you should still have a good sail shape even when deeply reefed. Credit: Graham Snook/Yachting Monthly

Unlike an in-mast furling system, where the sail is visible, on an in-boom system everything is happening on top of the boom, overhead and out of sight.

If you have a crew member spare and it’s safe, sending them to the mast to keep an eye on the sail as it furls can prevent damage, at least for the first few times using the system.

Pull in on the furling line, slowly and smoothly releasing the mainsail halyard, but keep a bit of tension on it.

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If you have too much tension the sail will want to roll away from the mast; if you’re seeing creases running from the bottom of the track to the boom at 45°, release the halyard a little more.

If the sail is rolling up toward the mast, you’ll need to increase the tension a little.

As the sail furls, the luff tape will naturally first roll aft, then move forward and repeat this – it’s all perfectly normal.

Once the sail is fully down, tuck the head into the boom if your system allows it, and add the sail cover.

Reefing underway

To reef when sailing, release the backstay and set the boom angle.

In rough weather, or when there are big seas, it’s best to take up on the boom’s topping lift to secure the boom and stop it rising and falling as the yacht goes over the wave crest.

Cover the sail once stowed to protect from UV. Credit: Advanced Rigging and Hydraulics

You’ll find it easier if you can bring the boat onto the wind and release the mainsheet to remove all drive from the mainsail; if the sail is flogging it’s depowered and can still be furled.

Next, take in on the furling line while slowly and smoothly easing the halyard as the sail furls.

Graham Snook is a marine photographer and journalist who has been involved in testing yachts and equipment for over 20 years. Credit: Graham Snook

Once you’ve reached a point where the batten is at the mandrel on top of the boom, make off the halyard and then furl the sail until the batten is under the mandrel.

Without reefing pennants to hold and support the clew of the sail, the loads are transferred to the batten and the cloth around it.

Because of this, it’s recommended that for in-boom reefing mainsails, a stronger stretch-resistant cloth like Dacron reinforced with Vectran or Dyneema or a tough cruising laminate cloth be used.

Whichever mainsail furling system you have or choose, spending a bit of time practising what works and what doesn’t on your system, at a time when it’s convenient to you, will pay dividends when you find you do need to reef.

Mainsail furling has had a bad reputation in the past, but used properly and with a little care, there’s no reason why it shouldn’t give you trouble-free sailing for years to come.

To raise the sail

• Release the backstay tension
• Make sure the boom is at the correct angle – use a strop or mark the vang if necessary
• Head up into the wind – it doesn’t matter if the main flogs as it goes up
• Release the mainsheet
• Take up on the mainsail halyard, but do not overtighten

To lower the sail

• Make sure the boom is at the correct angle
• Point the yacht into the wind
• Take in on the furling line as you ease the halyard at a steady rate

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The ins and outs of in-mast furling mainsails.

What is an in-mast furling mainsail?

Unlike a traditional mainsail that is hoisted and doused vertically with a halyard, an in-mast furling mainsail wraps around a tube inside a hollow mast. It is unfurled by an outhaul line and furled back in with a line labelled as the "inhaul."

Five yachts in the Modern Sailing School & Club fleet have in-mast furling mainsails:

• Andiamo (Catalina 36)
• Grey Goose (Beneteau Oceanis 37)
• Survivor (Beneteau Oceanis 38)
• Liberty (Beneteau Oceanis 38.1)
• Attitude Adjustment (Beneteau Oceanis 41)

Furling Mainsail Advantages 

• A furling mainsail is easy to reef and un-reef from the cockpit while underway - a great advantage in San Francisco Bay where winds can be highly variable.
• There's no need to flake and cover the mainsail when done sailing. Roll it up, close the line clutches, and you're done!
• Furling mains are easy to handle with short-handed crews.
• An in-mast furling mainsail cannot have horizontal battens, which means less control over sail shape, especially as the sail ages.
• In-mast furling units consist of many moving parts, which require routine service and can fail. Modern Sailing performs preventative maintenance and inspects in-mast furling units every two weeks.
• If not handled properly while furling and unfurling, the sail may bunch up and jam inside the mast.

It's important to know how to properly handle an in-mast furling mainsail in order to prevent problems later on.

How To Unfurl The Mainsail

Your goal is for the crew to work together to unfurl the sail in a controlled manner. The trick is to maintain slight tension on the inhaul line as the sail comes out. 

• If the dodger obscures the view of the sail, have a crew member stand where he or she can monitor the sail as it comes out.

• Open the mainsheet clutch and loosen the mainsheet. This will prevent the sail from accidentally powering up while being pulled out. (Note: always leave the mainsheet clutch open while the sail is unfurled or being furled.)
• Open the boom vang line clutch and loosen the line. This allows the boom to rise as the sail comes out.
• Wrap the outhaul line once or twice around a cabin top winch.
• Open the inhaul line clutch. Hold onto the inhaul line in one hand and ensure the rest of its tail is free to run.
• Pull the outhaul line while maintaining hand-tension on the inhaul line as the sail comes out. This is easier if one crew member pulls the outhaul while another keeps some tension on the inhaul.  Without tension on the inhaul line, you run the risk of the mainsail unfurling too quickly, which can cause the sail to luff violently and tangle up the outhaul.
• Tuck the outhaul into the winch's self-tailing line jaw and if necessary, grind  the winch handle until the sail is all the way out.
• Once the mainsail is fully unfurled (or unfurled to a desired reef point), close the outhaul and inhaul line clutches. Wrap the mainsheet on a cabin top winch and be sure to leave the mainsheet clutch open . Steer away from the wind to a close haul or reach and let the wind fill the sail.
• If necessary, you may adjust tension on the outhaul to trim and shape the sail.

How To Clear Furling Mainsail Jams

A common cause of a jammed furling mainsail is that the sail was wrapped too loosely around the tube inside the mast last time it was furled. To unjam it, your goal is to tighten the sail's wrap. Try the following steps:

• Close the inhaul line clutch.
• Wrap the inhaul line on a cabin top winch and tuck it into the line jaw.
• Wrap the outhaul line once or twice around on the other cabin top winch hold onto the tail firmly. Do not tuck the line into the line jaw.
• Open the outhaul line clutch.
• Grind the winch holding the inhaul line to bring the sail back in a foot or two. Maintain firm hand-tension on the outhaul line while furling.
• Close the outhaul clutch and tuck the outhaul line back in the winch's line jaw.
• Remove the inhaul line from the winch and open the inhaul clutch. 
• Try again to unfurl the sail. As before, maintain hand-tension on the inhaul line as you pull on the outhaul. Grind the outhaul winch with caution - do not use excessive force.
• If the sail is still jammed, if conditions permit, send two crew members forward on deck. Repeat the above steps again, with one sailor tugging downward on the foot of the sail, and the other sailor tugging outward on the clew as the sail comes out.

Never force a stuck sail by grinding hard on a winch. Excessive force could damage the sail or other components. If you still cannot get the sail unfurled after a few attempts, head back to base and call the office. A technician will meet you at the dock to troubleshoot the problem.

Trimming a Furling Mainsail

• In high winds (>15 knots), flatten the sail to de-power it. Tighten the outhaul to increase horizontal tension. Tighten up the boom vang to increase vertical tension.
• If the foot of the sail is still too baggy after the clew has reached the end of the boom, you can tighten the foot of the sail a little more by tightening the inhaul.   Keep the outhaul clutch closed and tighten the inhaul with caution - if you overtighten, you risk tearing the sail.
• In light winds, (<10 knots) a rounded shape in the sail will add more driving power. Loosen the outhaul and/or boom vang to give the sail a deeper curve or "belly."
• Main halyard tension is set by the MSC fleet technicians. Do not adjust the halyard. If the main halyard seems slack, report it when you fill out your electronic Boat Check-In Form.

Reefing the Mainsail

Reefing a furling mainsail is simple! Follow the steps below to furl the sail in part-way to shorten the sail. Some mainsails have marks on the foot of the sail to indicate suggested reef points, but you can customize your sail area to make it any size you like.

How To Furl Properly and Prevent Future Jams

Your goal is to wrap the mainsail tightly around the tube inside the mast. The trick is to tighten up the boom vang and maintain tension on the outhaul as the sail is being furled in.

• Steer into the wind and fall off to the left a couple of degrees.  - A slight starboard tack is acceptable if your mainsail wraps around the furler in a counter-clockwise direction. (A slight port tack will force the sail against the opening in the mast, making it difficult to furl the sail in.)  - A slight port tack is okay if a mainsail wraps around the furler in a clockwise direction. (A slight starboard tack will force the sail against the opening in the mast, making it difficult to furl the sail in.)
• Wrap the boom vang line around a winch and tighten it up a bit. This will lower the boom and flatten the sail, which helps it to wrap smoothly.
• Carefully unwrap the mainsheet from the winch and loosen the mainsheet.
• Wrap the outhaul once or twice on a cabin top winch. Keep a firm grip on the tail, but do not tuck it in the winch's line jaw. 
• Wrap the inhaul line on the other cabin top winch and tuck it in the line jaw.
• Open the outhaul clutch.
• Grind the winch holding the inhaul line to furl in the mainsail. Maintain some tension on the outhaul while furling to ensure the sail wraps tightly.
• Once the mainsail is fully furled, tighten up the mainsheet and close all clutches.

Want to learn more seamanship and safety tips? Check out the Member Resources section of our website. New articles are added frequently!

Article by Mary Elkins on January 17, 2020 Special thanks to Jim Haussener for his contributions to this article.

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In-mast furling mainsail: Pros and cons

In-mast furling has become more and more popular on modern sailing yachts. Some sailors love it and some hate it - as it happens with most technologies when it comes to boating, after all.

In this article, we look at the advantages and disadvantages of this system, so you can decide if a boat with an in-mast furling mainsail is right for you or not. But first, as always, let’s answer some common questions on the subject.

WHAT IS IN-MAST FURLING? 

In-mast furling is a furling system which allows you to furl your mainsail inside the mast of your boat. The mast is hollow and contains a tube around which the mainsail wraps. To wrap it and unwrap it, you pull on an outhaul line or an inhaul line. 

Can you reef an in-mast furling main?

Yes, in fact you can furl as much of the sail as you like, which gives you greater control over how much canvas you put out.

In-mast furling mainsail pros

Some sailors and cruisers find in-mast furling extremely handy. Here are the reasons why:

You can easily reef the mainsail from the cockpit

Reefing can be done quickly by solo sailors

You don’t need to fold and store the sail in a cover.

Being able to reef from the cockpit gives you a great advantage, as you don’t need to step on deck or onto the flybridge in order to reef. That’s great especially for solo sailors. The ease of the maneuvre is also a plus when hugging the coast in variable winds. While in-mast furling can be expensive, you won’t need to create and install a mainsail cover, which increases windage on deck. 

Finally, you won’t need to fight with the sail to fold it and push it into its cover at the end of a sail. This means you will never leave it out in the sun, even for a few hours after a long passage.

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In-mast furling mainsail cons

Some sailors are completely against in-mast furling because:

The system can jam or fail

You have less control over the shape of the sail while underway

In-mast furling needs to be carefully maintained.

Newer furlers tend to be more reliable than older models, so they jam and break less often. However, if you don’t handle the sail properly, you could end up bunching it up and jamming the furler. When this happens, a portion of the sail usually flaps in the wind uncontrollably. It’s also worth noting that mainsails that furl away don’t have battens, so you can’t control their shape as much, especially when reefing them. 

Finally, you’ll need to maintain the furler regularly and to replace your mainsail before it becomes baggy in order to prevent any issues. 

In-mast furling vs. in-boom furling

There’s an alternative to in-mast furling: in-boom furling. This is when the mainsail reefs inside the boom. While the two systems are very similar on all aspects, boom furling offers an advantage: if the furler jams, you can drop the sail onto the deck or into the cockpit and remove it. This is an excellent safety feature.

Another benefit of in-boom furling is that it can be added to an older sailboat, as many companies produce furling booms, which you can fit to your boat. If your boom sits very high or is above a flybridge, a furling boom will allow you to raise and lower the mainsail from the comfort of the cockpit. 

Finally, in-boom furling systems are reefed to a full-length batten, which means they allow you to pull the foot of the mainsail straight and flat. This means you can achieve a better shape.

As you probably know, sailors have strong opinions about everything to do with sailboats. You’ll find both cruisers who love their in-mast furling mainsail and racers who would only ever buy a yacht with a traditional mainsail.

PLANNING A REMOTE KAYAK TRIP

Night fishing tips from two pros.

Mainsail Furling Systems – Which one is right for you?

With the variety of options of mainsail furling systems available, including slab, in-boom, and in-mast systems, it can be challenging to determine which one best suits your needs. In this comprehensive guide, we will explore the pros and cons of each system, enabling you to make an informed decision that aligns with your sailing requirements.

The majority of yachts, specifically over 75%, utilize the slab-reefing technique as their preferred method for reefing the mainsail. However, as the size of the boat increases, there is a noticeable trend towards adopting systems that allow the sail to be furled within the spar itself. In-mast furling systems, in particular, are more prevalent in larger yachts with a length overall (LOA) of 50 feet and above. For craft measuring 65 feet and beyond, in-boom furling becomes the more commonly employed method.

In essence, as yacht size grows, there is a shift towards the use of in-mast or in-boom furling systems instead of the traditional slab-reefing method. This transition is influenced by factors such as ease of use, convenience, and the desire for improved sail control. Larger yachts often opt for in-mast furling due to its ability to reef the sail at any point of sail, while in-boom furling offers advantages in terms of sail shape and incremental reefing positions.

Slab (AKA ‘Jiffy’ Reefing) System

The slab-reefing method has stood the test of time and remains the most prevalent choice, with over 75% of yachts utilizing this system. Over the years, jiffy reefing lines have replaced the traditional reefing points stitched into the sail, offering a more convenient and efficient solution. There are variations of the jiffy system, including single lines and continuous lines, each with its advantages.

When it’s time to reef the mainsail, the crew releases the halyard tension to allow the sail to be lowered. Reefing lines, which are pre-attached to the sail, are then pulled through reefing cringles (sturdy metal rings) along the luff of the sail. These lines are used to gather and secure the excess sail material in a folded position. By pulling the reefing lines, the sail is gradually reduced in size, creating a smaller and more manageable sail area.

Once the desired amount of sail area is reefed, the reefing lines are secured, typically by tying them off to designated reefing points or reefing hooks on the boom. This ensures that the reefed portion of the sail remains securely in place. After the reefing lines are secured, the halyard tension is adjusted to raise the sail back up, taking into account the reduced size of the reefed area.

Advantages of Slab System

• Best Sail Shape: When sailing upwind, the bellied shape of a slab-reefed mainsail optimizes its wing-like performance both at the luff and on the foot. This design ensures enhanced aerodynamics and improved overall sail efficiency.
• Bigger Sail Area When Fully Set: The slab-reefing system allows for considerable roach in the mainsail, adding valuable sail area. However, it’s important to note that this advantage diminishes when the sail is reefed.
• Adjustable Back Stays: Unlike in-mast systems, the slab configuration enables better sail shape through the ability to tension the back stays and bend the top of the mast head back. This adjustability contributes to improved performance and control.
• Simplicity: The slab system boasts minimal complexities, reducing the likelihood of mechanical failures and simplifying maintenance requirements.
• Lowest Cost: In comparison to in-spar furling systems like in-boom and in-mast, the slab system proves to be the most cost-effective solution. The absence of additional mechanisms such as mandrels, motors, and gearing significantly reduces overall expenses.
• Better Stability: When the sail is furled using the slab system, the weight is concentrated on the boom, resulting in improved yacht stability. In contrast, in-mast systems carry the weight aloft, affecting stability in certain conditions.
• Less Windage: The slab system incorporates a smaller mast section, reducing both cost and windage when compared to in-mast systems. Additionally, the boom’s smaller and lighter profile ensures easier control and eliminates the need for a preventer on all points of sail, as required with in-boom systems.

Disadvantages of Slab System:

• Must Come Head to Wind: To set and reef the sail using the slab system, the yacht needs to be rounded up into the wind. This maneuver can be challenging, particularly in open ocean conditions with 40 knots or more of wind and waves reaching heights of 5 meters or more. Rounding up the yacht in these extreme conditions requires skill and experience.
• Crew Required on Deck: When the mainsail needs to be fully dropped, it will require crew members to go on deck to lash down the main halyard, preventing the sail from snaking up again. This additional crew involvement adds complexity and potential risks, especially in adverse weather conditions.
• More Sail Maintenance: Slab-reefed sails require more maintenance compared to in-boom or in-mast systems. The reefing point cringles, which take all the load when the sail is reefed, need to be regularly inspected and maintained to ensure they do not break down. This additional maintenance requirement adds to the overall workload of sail care.
• More Crew Needed: Setting a reef using the slab system typically requires a minimum of two crew members. This means that, depending on the size of the yacht and the sailing conditions, additional crew members may be required to put a reef in the mainsail. This can limit the sailing options for those who prefer to sail single-handed or with a smaller crew.
• High Sail Stack: On larger yachts (45ft and above), the mainsail stack on the mast can become quite high when using the slab system. To fully secure the mainsail to the gooseneck, crew members will need to go on deck and climb two or three steps up the mast. However, it’s worth noting that the Harken T-Track Switch system can significantly reduce the height of the stack, offering a potential solution to this challenge.
• Less Reef Points: Slab-reefed sails are generally limited to two or three reef points. In comparison, in-boom or in-mast systems offer a greater range of incremental reefing options. Having more reef points allows for more flexibility in adjusting the sail area to match various wind conditions, enhancing sailing performance and safety.
• More Lines in the Cockpit: When the sail is reefed using the slab system, there are more ropes present in the cockpit, requiring proper stowage to prevent tangling and ensure a clear working area. Managing the additional lines can be challenging, especially in fast-paced or demanding sailing situations.
• Needs Lazy Jack Bag: A stack-pack bag, also known as a lazy jack bag, is required on the boom to contain the mainsail when it is furled using the slab system. While this bag facilitates sail stowage, it adds windage and potentially affects the aesthetics of the yacht. The impact on aesthetics may vary depending on personal preferences and the design of the lazy jack bag.

In-Boom Furling System

In-boom furling is a method used to reef the mainsail on a yacht by rolling the sail inside the boom. When it’s time to reef the mainsail with an in-boom furling system, the process begins by activating the mainsail furling mechanism. This mechanism is typically located inside the boom and is connected to a mandrel, which acts as a spindle for rolling the sail. By operating the mainsail furling control, the mandrel rotates, causing the mainsail to be gradually rolled up inside the boom.

As the sail is rolled up, the excess material is neatly stowed within the boom. In-boom furling systems often feature full-length battens that help maintain the shape and stability of the reefed sail. The mainsail furling process continues until the desired amount of sail area is reefed, adjusting to the prevailing wind conditions.

Once the sail is fully rolled up inside the boom, it is securely held in place. In-boom furling systems usually incorporate a locking mechanism to prevent any unintended unfurling of the sail. This ensures that the reefed sail remains tightly furled and ready for use when needed.

Advantages of In-Boom:

• Good Sail Shape: The in-boom system allows for a better wing-style sail shape compared to the in-mast system, though not as versatile as the slab system. It enables the sail to maintain a more efficient aerodynamic profile, enhancing overall performance. It’s important to note that while some claim the sail shape can be the same as that of a slab system, this is not entirely accurate. The sail and its full-length battens must be rolled around a straight mandrel (the in-boom spindle), and excessive belly built into the sail can cause it to stack forward onto the gooseneck, leading to undesirable consequences.
• More Reef Positions: With the in-boom furling system, there are typically more reef positions available. The furling process finishes at a point well between the battens, allowing for smaller increments of reef compared to the slab system. This finer control over reefing enables sailors to adjust the sail area more precisely to match varying wind conditions, optimizing performance and maintaining a comfortable sailing experience.
• Less Weight Aloft: When the sail is furled, it rests on the boom rather than being positioned aloft, resulting in a better righting moment compared to the in-mast system. The reduced weight aloft contributes to enhanced stability and maneuverability of the yacht, particularly in challenging weather conditions.
• No Reefing Lines in the Cockpit: Unlike the slab system, the in-boom system eliminates the need for reefing lines in the cockpit. This simplifies the setup and reduces clutter, providing a cleaner and more organized cockpit layout. It allows for better movement and minimizes the risk of tripping or entanglement during critical maneuvers.
• Less Windage on the Mast: The mast section required for the in-boom system is generally smaller compared to the in-mast system. This reduction in mast size, similar to the slab system, leads to lower windage. The reduced wind resistance contributes to improved performance and maneuverability, particularly when sailing upwind.
• Bigger Sail Area: With the in-boom system, the mainsail can have a substantial roach, similar to the slab system. The roach refers to the extended area of the sail beyond a straight line connecting the head and clew. A larger sail area allows for increased power and potential speed, benefiting both performance-oriented sailors and those seeking exhilarating sailing experiences.

Disadvantages of In-Boom:

While the in-boom system offers several advantages, it’s important to consider its limitations and potential drawbacks before making a decision. Here are some disadvantages associated with the in-boom mainsail furling system:

• Must Come Head to Wind: Similar to the slab system, the in-boom system requires the yacht to be rounded up into the wind to furl and set the sail. This maneuver can be challenging, particularly in open ocean conditions with strong winds and large waves. Rounding up the yacht in adverse weather or rough sea conditions may pose difficulties and require skilled seamanship.
• Longer Furling Process: When furling the sail using the in-boom system, the sail takes longer to drop compared to the slab system. The mandrel, which the sail is rolled around, requires more time to take up the lowering sail. As a result, the helmsman must hold the yacht into the wind for a longer duration, extending the mainsail furling process. This prolonged time spent maneuvering into the wind can impact overall sailing efficiency and require additional attention from the crew.
• Two-Man Operation: To ensure the sail is not stacking forward excessively during the mainsail furling process, crew members must be stationed on deck to monitor the furl. This means that the in-boom system typically requires a minimum of two crew members or more. The need for additional crew members may limit the flexibility and ease of handling for single-handed sailors or those operating with a smaller crew.
• High Cost: Among the three mainsail furling systems discussed, the in-boom system tends to be the most expensive option. In addition to the furling system itself, the installation often requires additional components, such as a powered vang to assist with lifting the boom. The higher cost of the in-boom system should be taken into account when considering budget constraints or cost-effectiveness.
• Propensity to Stack Forward: If the helmsman allows the boat to fall off the wind while the sail is being furled and wind fills the sail, even at the leech, there is a risk of the sail stacking forward. When this happens, the sail must be re-hoisted and the mainsail furling process restarted. This potential for the sail to stack forward adds complexity to the furling procedure and requires vigilance from the crew to prevent such situations.
• Needs a Preventer: The in-boom system, due to its larger boom size and the inclusion of furling mechanics, requires the use of a preventer on all points of sail. A preventer is a line used to secure the boom and prevent unintended jibes or sudden movements. The presence of a preventer adds complexity to sail handling and requires careful attention to prevent accidents or damage to the rigging.

In-Mast Furling System

When utilizing an in-mast furling system, reefing the mainsail is a straightforward process. The mainsail furling mechanism, typically located inside the mast, is engaged to initiate the mainsail furling operation. As the furling control is activated, the sail is rolled up around a mandrel positioned within the mast.

As the mainsail is furled, it is neatly stored inside the mast, reducing the exposed sail area. The mainsail furling process continues until the desired amount of reefed sail area is achieved, providing better control and stability in stronger winds. In-mast furling systems often allow for infinite reefing points, enabling precise adjustments to match the prevailing conditions.

In-mast furling provides sailors with a reliable and user-friendly solution for reefing the mainsail. Its versatility, ease of operation, and streamlined cockpit contribute to a more enjoyable and efficient sailing experience, particularly for cruisers and those seeking simplicity in sail handling.

Advantages of In-Mast:

The in-mast mainsail furling system is widely favored among larger offshore cruising boats for its convenience and ease of handling. It offers several advantages that make it a popular choice for many sailors. Here are some advantages associated with the in-mast mainsail furling system:

• Doesn’t Need to Come Head to Wind: One of the significant advantages of the in-mast system is that it allows the mainsail to be furled at almost any point of sail. Unlike other systems, which require the yacht to be rounded up into the wind, the in-mast system enables reefing or furling without altering the yacht’s course significantly. Even when running downwind , a simple change of course by around 20 degrees can lift the sail off the shrouds and spreaders, facilitating easy reefing.
• One-Man Operation: Depending on the chosen system, the in-mast furling can be operated by a single crew member. Electric or hydraulic systems, in particular, offer the convenience of effortless furling with minimal physical exertion. This feature is advantageous for short-handed sailing or when there’s a lack of crew members available to assist with sail handling.
• Less Rope in the Cockpit: Compared to the slab system, the in-mast system reduces the amount of rope and lines in the cockpit. If equipped with an electric or hydraulic motor, the sail furling can be controlled from the cockpit, minimizing the need for crew members to go on the deck during sail maneuvers. This contributes to a clutter-free and safer working environment onboard.
• More Reef Points: The in-mast system allows for infinite reef points, offering more flexibility in adjusting the sail area to suit various wind conditions. Sailors have the freedom to reef the sail incrementally, tailoring it to the prevailing winds and maintaining optimal control over the yacht’s performance. This versatility is particularly beneficial for long-distance cruising or when encountering unpredictable weather conditions.
• Medium Cost: Compared to the in-boom system, the in-mast system generally falls into a more moderate cost range. While specific prices may vary depending on the chosen manufacturer and additional features, the overall cost is often more affordable, making it an attractive option for sailors seeking a balance between performance and budget.

Disadvantages of In-Mast:

The in-mast mainsail furling system is widely popular, particularly among larger offshore cruising boats. It offers several advantages, but it’s also important to be aware of its limitations and potential drawbacks. Here are some disadvantages associated with the in-mast mainsail furling system:

• Flatter Sail Shape: One of the drawbacks of the in-mast system is that it doesn’t provide as good a sail shape as the slab or in-boom systems. The need to wrap the sail around the mandrel inside the mast restricts the ability to achieve an optimal wing-style sail shape. This limitation can impact overall performance, especially when sailing upwind.
• Bigger Mast Profile: The in-mast system requires a larger mast section to accommodate the mandrel and the furled sail. The increased size of the mast profile can lead to additional weight aloft, affecting the yacht’s stability and righting moment. It’s important to consider the impact of a larger mast profile on the overall sailing characteristics and performance of the yacht.
• Smaller Sail Area: With the in-mast system, the sail area is generally smaller compared to the slab or in-boom systems. To accommodate the furling mechanism, the sail cannot have battens and instead relies on a hollow shape (the reverse of roach) to minimize leech flapping. This reduction in sail area can limit the yacht’s performance, particularly in light winds or when maximizing sail power is crucial.
• Greater Weight Aloft: Due to the inclusion of the mandrel and the furled sail within the mast, there is increased weight aloft with the in-mast system. This additional weight affects the yacht’s center of gravity and can have a slight impact on the righting moment. It’s important to assess the implications of increased weight aloft on the yacht’s stability and overall sailing performance.
• Possible Sail Jam: One concern with the in-mast system is the potential for the sail to jam within the mast. Although this is a concern for many sailors, it can be mitigated by adopting proper furling procedures. Releasing the outhaul line gradually, followed by tensioning the sail through the in-mast motor, can help prevent jamming. Some manufacturers have also developed automatic outhaul systems to further reduce the chances of sail jam. However, it’s crucial to be aware of this potential issue and take the necessary precautions.
• No Mast Bend: Unlike other systems, the in-mast system requires the mast to remain straight. Bending the masthead back, which is possible with other systems, can cause the sail to jam. The inability to adjust mast bend restricts the ability to fine-tune sail shape and performance, especially when sailing in varying wind conditions.

When considering the various mainsail furling systems available for yachts, it’s important to evaluate the advantages and disadvantages of each option to determine which system best suits your sailing needs. Here’s a summary of the main points discussed for the three common mainsail furling systems: slab, in-boom, and in-mast.

Slab System: The slab system is widely used and offers several advantages. It provides excellent sail shape and a larger sail area when fully set. It is relatively simple, cost-effective, and lightweight compared to other systems. However, it requires the yacht to come head to wind for reefing or setting the sail, which can be challenging in adverse weather conditions. Additionally, it requires more crew members for sail maneuvers and has a higher sail stack on larger yachts.

In-Boom System: The in-boom system keeps the furled sail low down and allows for good sail shape. It offers more reef positions and reduces weight aloft, contributing to a better righting moment. However, it also requires the yacht to come head to wind for furling and setting the sail, which can be time-consuming. The system tends to be more expensive, often requiring a powered vang for boom lifting. There is a propensity for the sail to stack forward, necessitating the use of a preventer on all points of sail.

In-Mast System: The in-mast system is favored for larger offshore cruising boats due to its convenience. It eliminates the need to come head to wind for reefing or furling, allowing for easier sail handling at any point of sail. It can often be operated by a single crew member and has fewer ropes in the cockpit, enhancing safety and reducing clutter. The system offers more reef points, allowing for incremental adjustments to the sail area. However, it compromises on sail shape, has a larger mast profile, and results in a smaller sail area when fully set. Sail jamming is a potential concern, but can be mitigated with proper sail tensioning techniques.

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Just Furl It: The Case for Furling Mainsails

June 21, 2024

The sailing challenges that make us feel alive and accomplished are not found muscling a mainsail to the top of the mast or trying to wrestle a giant cover on a massive sail — and don't even get us started on reefing. So, we say, save your energy and just furl it. Whether you sail with a full crew, with your partner, or solo, a furling mainsail might just be the answer to smoother sailing.

There are many mainsail handling systems on the market–lazy jacks, self-flaking, V-booms–and they all have valid qualities and use cases. However, the ease of a furling system paired with advancements in both the systems and sail design has moved them to the top of our list.

You can furl your mainsail into your mast or your boom. Here's a deep dive on the options:

IN-MAST FURLING

In-mast furling systems are loved by cruisers for their ease, safety, and reliability. Instead of going up and down, the sail goes in and out–think of a headsail furler inside the mast. They're usually controlled from the cockpit using a powered winch and can be easily "reefed" or furled to a desired size for the conditions.

So, what's the catch? Furling mainsails are difficult sails to build. They don't have a traditional batten structure, and they have to be able to fit inside the limited space in the mast cavity, so compromises in both size and shape must be made. You will trade some performance for easier and safer operation.

SAIL DESIGN

For a traditional track system, you can expect an in-mast furling mainsail to be around 20-25% smaller than a mainsail. The sail's shape also must be quite flat, with minimal luff curve, so it can fit into the small mast cavity. "Control of sail shape via mast bend is not possible. Without battens, there is no structure to resist compression and keep the leech from moving toward the luff under load," Quantum's Dave Flynn explains. "This causes the sail to get fuller when one wants to see it flatter. The leech will never be as straight and clean as a batten mainsail, and there will typically be some curl at the edge."

To compensate for the lack of battens, which support the sail's area outside the straight line between head and clew (the roach), the sails are built as head sails with leech hollow. Vertical battens are an option for better shape and performance but can create other problems. First, battens add thickness to the sail and can make it difficult to roll in and out of the cavity, so there are size and space requirements on the mast. The batten pockets are built into the sail and will chafe, requiring more maintenance over time.

Dave advises: "Even though vertical battens can reduce leech curl and allow for a small increase in area, they can't address the compression loads that cause a sail to get fuller under load. At the end of the day, if you are going to add vertical battens, be aware they can potentially compromise the best asset of in-mast systems: the simplicity and reliability."

IN-BOOM FURLING

Want the ease of handling of a furling mainsail without sacrificing sail performance? Enter the in-boom furling system. They are purposely designed, not just a headsail furler on its side. A rigid mandrel sits inside a hollow boom with the foot of the sail attached along a portion of the mandrel, and the tack and clew are secured at either end. When it's time to hoist, a special feeder guides the luff into a track on the mast. A powerful drum controls the mandrel, and the control line for the drum is normally run on the deck alongside the mainsail halyard. Electric or hydraulic winches make raising the halyard or furling the control line a breeze.

SAIL SHAPE AND BATTENS

"The beauty of in-boom furling is not just in never-leave-the-cockpit ease of handling, but in the sail itself," says Dave. "A full batten structure is used which allows the designer to create a full-sized sail, with as much roach (area outside the straight line between head and clew), as the sail needs." This means that even though you have to tailor the sail shape to the system's demands, it's as good as a traditional mainsail, and you can control the shape with a mast bend and partially furling the sail.

ATTENTION TO DETAIL

The in-boom systems require more attention to detail when using, especially when lowering. "The trick is to get a relatively uniform roll of the luff underneath the feeder," advises Dave. "This is a combination of setup (boom angle, tack position) but also relies on the operator. The rate at which the mainsail halyard is eased is critical. To help make sure everything goes smoothly, you need to watch what you are pulling on, keeping the forward end of the roll in sight as you furl so you know how much drag to put on the halyard." You need to set the control lines up with a clear line of sight to the forward end of the boom.

The process and mechanism for raising and lowering these sails means you will have more wear and tear on the luff tape and the forward end of the battens. This just means you will need to pay closer attention to wear and make sure you're getting the prescribed annual inspections and regular maintenance. "If you are willing to accept these limitations, in-boom furling provides the ultimate balance between no-compromise performance and ease of use," says Dave.

Whether you're ready to make the jump to a mainsail furling system, have questions, or want to explore different options, we're here to help ! There are pros and cons to any sail handling system, and our team of experts can help guide you to the right solution for your needs and build you the perfect sail to match your needs.

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Mainsail Furlers Lighten the Load

• By Ralph Naranjo
• December 21, 2021

The late Ted Hood, one of sailing’s most accomplished practitioners, mainstreamed roller-furling mainsails. He acknowledged that a sail being wound into one of his Stowaway Masts had to be cut flatter, devoid of horizontal battens, and lack a big roach. But despite these performance-sapping attributes, he saw the upside it would offer shorthanded sailors: The system demonstrated that performance is also linked to having the right amount of sail area set. And over time, making the mainsail behave like a zoom lens has proved to be as appealing to sailors as the latter has been to photographers. 

Initially, a few innovators attempted to retrofit older rigs with external, behind-the-mast roller-furling systems. In essence, these units were akin to a roller-furling headstay stretched between a beefed-up masthead fitting and the gooseneck. Unfortunately, as the tension between the masthead and gooseneck increased, the spar tended to bow and the luff of the mainsail curved to leeward. This made reefing and furling difficult, and placed excess stress on the spar itself.

Seldén and Schaefer solved the problem by adding evenly spaced track connections that linked the mainsail furler to the mast track. Today, Facnor also offers a refined version of this concept for those interested in converting a standard spar into one that hosts a roller-furling mainsail.

Meanwhile, spar-makers soon recognized that a specially extruded, open-trailing-edge spar could house a furled mainsail. A central mandrel, or furling rod with a luff-tape slot, rotates and retracts or releases the mainsail from within the mast. The design requires a way to support and tension the luff rod and a bearing system to handle rotation under load. The geometry of the sail slot and cavity is vital, as is the cut and construction of the mainsail. 

Hood’s sailmaking ­background and yacht-design ­business put him at the head of the fleet, and Stowaway Masts, with their mechanical, electric or hydraulic roller reefing systems, showed up on vessels from 35 to 100-plus feet.

The furling concept might seem fairly simple, but the devil is in the details. Hood, Seldén and many others eventually worked out most of the kinks, including maintaining proper furling-rod tension. But even so, care needs to be taken when furling and outhauling the mainsail, and that’s especially true when an electric or hydraulic winch does the pulling. The big danger lies in overloading the outhaul due to a hockle, or kink, in the furling line. Too hard a pull by a power winch can wedge the partially furled sail in the exit slot, or damage the drive system or the sail itself. Units with narrower exit slots avoid this “herniated” mainsail condition but add increased chafe concerns. Hood’s furling designs have continued to evolve and are now being produced by Formula Spars.

Just as monohulls and multihulls have their advocates, there’s plenty of partisanship when it comes to in-mast or in-boom furling systems, the latter being another option for those seeking ease of sailhandling. Both approaches succeed at sail-area reduction, and both act as a “force multiplier”—allowing a shorthanded crew to cope with a much larger mainsail. But there are also a few not-so-subtle differences between the two. 

Advocates of in-boom furling call the ability to have a deeper-draft, horizontal-batten-equipped, roach-sporting mainsail an important value-added feature. This means that when comparing equal sail areas, the in-boom option will outperform the in-mast alternative. The boom-­furling mainsail comes closer to matching the performance of a conventionally hoisted mainsail. Another big plus is that if the boom-furler function fails, you can still lower the mainsail conventionally.

As with most good things, there are also a couple of downsides that need to be recognized. The first is the size and weight of the boom, which is typically at least double or more the diameter and weight of a conventional boom. The weight issue raises some tactical and safety concerns. The heavier boom will more actively respond in light air and a rolling seaway, creating trimming issues. It also presents a greater risk to the crew during an unanticipated jibe, so more attention needs to be paid to the preventer or the boom brake. 

Ultimately, there’s a vulnerability to the short portion of track that leads the sail’s luff from the mast to the boom mandrel. The angle that the boom makes with the mast is very important, as is following the manufacturer’s furling guidelines. A heavy-duty mechanical or hydraulic boom vang will help ensure that the correct angle is maintained while reefing. 

Ted Hood was correct: Furling is the future. But a few of us still cling to the simplicity, sail-shaping advantage, and lessened chafe found in conventional slab reefing.

Ralph Naranjo is a circumnavigator, technical writer, former Vanderstar Chair at the US Naval Academy, and author of The Art of Seamanship , among other books.

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• In-mast Furling

Should We Be Wary of Using In-Mast Furling Systems?

No, says brian mistrot - and explains why....

Questions and issues surrounding in-mast furling mainsails and their potential to jam or cause problems have come up multiple times with many owners I have spoken to.  Inevitably, I have both current and potential owners asking me if I like it and (predictably) does it jam?

There are many horror stories out there about jams.

Most of these stories have been blown out of proportion and I find many perpetuated by those who have never even had in-mast mains. 

Some of the concerns are viable. The two biggest are that you will lose some performance with an in-mast.

For racers, unless appropriately handicapped, this probably is not the best option.

Another major concern is that if it does jam in a storm, you cannot blow the halyard to drop the main. Nightmare scenarios and reports of cutting down mains in a storm have surfaced.

I have not heard of a Catalina C400 (my current boat) having to do this, but have heard others report it from other manufacturers that perpetuates the concerns of this system.

For the record, I have thousands of miles on both traditional slab (or jiffy) reefing mainsails and in-mast furling systems . I've been offshore more times than I can count with my in-mast and been stuck in some pretty nasty storms and squalls – one lasting three days.

With my knowledge of both systems, I will heartily say that I would never go back to slab reefing unless I was racing. And I also believe the performance lost is minimal between the two - and most of us not doing distance races would never know.

The issue with in-mast jams is that the vast majority of the sailors using the system are not using it correctly...

Most of us were never instructed on it or because we are seasoned sailors, use it as we would a traditional main.

Therein is the problem and why in-mast furling systems often get a bad name. For the record, I have never, not in many thousands of miles, had one single jam. 

The Following Steps will Help You Keep From Jamming Your In-Mast Furling/Reefing Gear...

Note the location of the clew in the pic below. It does not go horizontally into the mast. It travels up at an angle into the mast. This is critical to understand.

Why? Because as a traditional (slab) reefer, you would point into the wind, tighten down the mainsheet to keep the boom centered - some even tighten down on the boom vang to help - haul up the main halyard until you have reached the top, then fall off and begin adjusting the vang, sheet, outhaul and halyard to the appropriate point of sail and conditions.

We effectively reverse these to drop the main, again keeping dead to wind or close to, and keeping the sheets and typically the vang taunt. If you do that with an in-mast system, sooner or later it will jam.

On In-mast, you MUST allow room for the car to travel down the boom and for the clew/sail to enter and exit at its proper point.

If you cinch down on the main sheet and vang and then begin to haul in the reefing line, you will see that you cause tension down the leech of the sail. This often results in crinkles forming as you reef. These crinkles are what cause jams.

So, when reefing your in-mast, you must release the tension on the main sheet and vang. Take the tension off so the sail can roll into the slot as designed. Also, keep some tension on the outhaul as you reef it to prevent any unwanted crinkles and a smooth roll.

Lastly, you will notice the mast is slotted more to one side than the other. Depending on where your sail rolls, one point of sail may be easier to reef than others. For us, ours is a starboard tack. This is because the sail rolls out away from the mast and does not rub against it while reefing.

Don’t forget to put some McLube Sailkote Dry Lubricant on the mainsheet track to reduce the friction on the car. I do this about once a month.

One Final Point...

We almost never use the winch to reef our sail in normal conditions… and NEVER use the electric winch.

If you reef the sail by hand, you can feel any potential jams before they happen and can pull them back out. If you gorilla-arm that sail in with the winch or the electric winch, you can create a jam that will be very difficult (if not impossible) to get back out.

If you find yourself in a situation where you have to winch in the main, at least go slowly and keep staring up the slot for crinkles going in. 

I am a fan of in-mast furling mainsails for most sailors. It keeps the crew safe and in the cockpit instead of tidying up sails on deck. It also gets a lot more use than traditional mainsail reefing systems because it is so easy to use and reef.

Keep in mind what I said above when operating the sail, and you too should get thousands of trouble-free miles.

Brian Mistrot

S/V 'Sea Mist IV', Catalina C400 #289

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FURLING SYSTEMS

BOOM FURLING SYSTEMS

Boom Furling Units are becoming more and more popular on mid-size and larger cruising yachts, where they offer the opportunity to have a fully automated furling system without compromising the sail area or performance of the mainsail. This is because we can build a sail with full-length battens and the same roach profile as we would on a standard mainsail. These sails perform as well as standard mainsails and are reefed by partially rolling the sail.

STANDARD FEATURES

Full Battens Stiffening Battens Bolt Rope Leech Tabling 2 Reefs Soft Tack and Clew Leech Line Telltales Sail Bag

Sail Numbers Insignia Additional Reefs Shape Stripes

GENOA FURLING SYSTEMS

Doyle's Genoa Furling System is an ideal, value priced solution for coastal cruisers. Roller furling makes handling larger genoas easier, and give sailors a wider wind range with the option of roller-reefing.

Our design team’s understanding of loads, strain and chafe allow Doyle to deliver a durable, cost-efficient sail. There are various options available, depending on requirements and budget.

CODE 0 FURLING SYSTEMS

A furling unit means that using a Code 0 is as simple as hauling on the sheet to deploy the sail, then pulling on the furling line to furl it away when finished.

IN-MAST FURLING SYSTEMS

In-mast furling units are a very popular choice for the cruising and offshore market. They offer a very convenient way to furl the sail and offer a user friendly shorthanded solution to the cruising sailor.

Traditionally the in-mast furling mainsail was viewed as an inefficient sail for windward performance but with the solution of vertical battens performance is greatly improved.

For more information on the Selden in mast furling - see here 

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More than 3000 Monohulls and Catamarans Sailing with Leisure Furl ®

Hoist, reef, and stow your mainsail from the safety of your cockpit.

Leisure Furl in-boom furling is the world’s most popular and well-tested mainsail furling and reefing system. With thousands installed, and millions of offshore miles sailed, it has become the boom furler of choice for experienced performance cruisers around the world. Decades of real life experience tells them they can trust Leisure Furl for smooth reliable operation in even the roughest conditions.

Don’t just take out work for it, let veteran sailing Journalist, Tom Cunliffe tell you his story:

Safe and Easy Mainsail Furling Control from the Safety of Your Cockpit

With a Leisure Furl boom furler, one person can quickly and easily raise, reef, or furl your mainsail without leaving the safety of the cockpit. Just unroll the mainsail from inside the boom furler and go sailing. If the wind comes up, simply reef the mainsail by rolling it back into the boom furler to the desired height. With Leisure Furl, each batten becomes a reef point, so there are virtually unlimited mainsail reefing options. When you’re done sailing, there is also no need to get up on a rocking and dangerous cabin top to flake and sail tie your mainsail, or to stuff it into a large and unsightly lazy jack pack. With Leisure Furl you simply roll the mainsail back into the boom furler and pull the integrated sail cover closed. It’s that easy!

Boom Furling is Far Safer than In-Mast Furling Alternatives

Boom furling also allows for safer troubleshooting because everything is within reach at deck level. With in-mast systems, jams and problems can happen high above the deck, possibly requiring a dangerous trip up the mast to affect any repairs. With Leisure Furl, should a problem occur, our exclusive ratcheting mandrel design allows you to quickly release the system with the pull of a pin so the mainsail be manually rolled back into the boom using a winch handle.

Superior Sail Performance

Unlike in-mast furling systems that require a flat, inefficient battenless mainsail to avoid jamming, Leisure Furl’s elegant in-boom furling design allows the sailmaker to build in a deeper mainsail draft with full length battens. This significantly improves light wind sailing performance so you can do less motoring, and enjoy far more sailing.

Boom Furling Designed to Fit Your Sailboat

Whether you enjoy day sailing, coastal cruising, or true offshore bluewater passagemaking, each new Leisure Furl boom furler is custom engineered to fit. We use a proprietary multi-factor design program to spec your boom, and then build it to exactly fit your boat’s dimensions and sail plan. Available for boats ranging from 27’ to 70’, we offer three base models designed to fit your sailing type, including the Offshore, the Passagemaker, and the Coastal. All three Leisure Furl models can be made of aluminum or carbon and customized with a variety of finishes to match your aesthetic needs. With proper installation and a quick training session, a new Leisure Furl in-boom furling system is the safest and easiest way to set your mainsail, especially with a shorthanded sailing crew.

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Testimonials

Our Leisure Furl Coastal, in boom, mainsail-furling system has been installed on our Catalina 30 for approximately six months now. We could not be more pleased. The system has worked flawlessly from the day it was installed. It has given us the confidence to sail short-handed in conditions where we would have hesitated with a conventional reefing system. My wife especially likes not having to deal with the sail ties and the dirty mainsail cover. The design, engineering and production quality of the Leisure Furl Coastal™ system is better than other systems that we looked at.

Sincerely. William E. Garrett, Jr., CPM President Inter-Pacific Asset Management Westminster, California

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Is in-boom furling the next big thing in sail handling technology?

• August 24, 2020

The engineering of in-boom furling systems has been considerably refined over the years and today’s systems are much better than early iterations, writes Rupert Holmes

Easy reefing on the Kraken 66 White Dragon during our heavy airs test, with an in-boom system by Southern Spars. Photo: Kraken Yachts

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.

This Furlerboom installation shows how neatly a mainsail can be furled

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.

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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.

Gooseneck of a Hall Spars Oceanfurl system

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 old-school 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.”

Sail attachment on a Mainfurl boom

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.

A composite Furlerboom system on an Eagle 54 daysailer

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.

Forespar Leisure Furl system on a Tartan 5300. Photo: Onne van der Wal

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.

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• Sails, Rigging & Deck Gear

In-Boom Furling: Five Systems

Our last good look at in-boom furling systems was in the August 1, 1998 issue, when we liked both ProFurl and Leisure Furl, giving the edge to the latter despite its greater cost. The recent introduction of Schaefer’s new in-boom system gives us an excuse to revisit the subject and the systems in the field.

From the outset we’d acknowledge that with each passing year, sailhandling systems get more and more refined and efficient—never mind the days of footropes and gaskets, of one hand for the headsail and one for yourself during routine jib changes.

Even so, the mainsail remains a challenge. Stacking systems, lazy jacks, the Dutchman, in-mast furlers… all contribute their share of convenience and control, but none has proven to be the answer. Stowing, furling, and reefing the main is still a sizable chore, especially as the size of your boat increases. And, as always when we attempt to conquer the considerable forces of wind and wave by mechanical means, we tread a fine line between convenience and chaos.

Background In the late ’80s, Hood Systems introduced the Stoboom, and rolling the sail inside the boom became an option. More affordable and less risky than furling the main inside the mast, these boom furlers were a big hit. However, the newly-engineered hardware proved to be more complicated and ultimately less convenient than it looked. It was, according to one owner who sailed a Hunter 42, “the costliest consumer mistake I ever made.” 

The sail entered and exited the Hood boom through a narrow slot in the top of the tube. For that and several other reasons Stobooms proved  jammable. They were also  fickle in terms of boom angle, and costly in terms of luff chafe. Hood tried education (a special aftermarket owner’s manual) and hand-holding (extensive customer service) before eventually pulling the Stoboom off the market. “However,” says Paul Boyce of Hood Yacht Systems, “we’re still involved in in-boom furling with hydraulic systems fitted to larger boats, most of which are in Europe.”

The advantages of in-boom furling that prompted Hood’s “noble experiment” have not disappeared with Stoboom. Compared with in-mast furling, the boom-based systems weigh less and keep weight lower. Probably the most significant selling point of a sail that lives in the boom, however,  is its shape. In-mast furlers require roachless, high-aspect triangles, thus reducing mainsail area, distorting ideal shape, and lessening draft control. We’ve talked with sailmakers, and most peg the overall performance loss that you’ll pay for the convenience of in-mast furling at 20% or worse. With a boom-furling system you can assure yourself of a powerful modern sailplan with plenty of roach, with the additional bonus of being able to use full-length battens to help control sail shape and reduce flogging.

There are other plusses—freedom from reefing-line clutter, variable sizing potential, automatic sail-covering, and the ability to retain your original spar, to name a few—but to us the most telling difference is safety: If an in-mast furler jams it’s probable that someone will need to go aloft to free it. Until then, you’ll be stuck with a hoisted mainsail in what may be exactly the wrong conditions. A jam in the boom can be addressed from on deck. If all else fails, just drop the sail as you would a normal main and furl it on the boom instead of inside.

But boom furling has plenty of detractors. Butch Ulmer, veteran sailmaker from City Island, NY, feels cautious about it: “The geometry still needs to be worked out. Big roaches drive battens forward. Overcoming that friction isn’t easy and it’s certainly not automatic.”

We asked the owner of a 73-footer who undertook a complete and costly refit why he hadn’t put a boom furler aboard. “I don’t need a $20,000 sailcover,” he replied.

Peter Harken, whose company makes headsail furling systems, said “We haven’t gotten into in-boom furlers because we think there’s a better way. We may be a bit prejudiced, but we feel that the batt-car system we’ve devised is the safest, surest, easiest way for getting a sail up and down easily and when you really need it. I  can just about guarantee those cars won’t jam, and you can’t say that about anybody’s boom-furler. Most of these systems work most of the time, but when you really need it, give me something that’s simple and foolproof.”

The In-Boom Furling Field Today there are five in-boom systems on the market. We’ve sailed them all, noting design, construction, and performance. Given the conditions, we did our best to see how each delivers on the promise of boom furling. And at what price?

One overall conclusion is that, while Stoboom may have spoiled the boom-furling parade for lots of sailors, today’s systems really work. We put the gear through paces that occasionally created problems, but those snags never kept us from executing our set/reef/reset/douse evolution.

Schaefer and John Mast have relatively narrow openings in the top of their booms, but among the others there’s a trend toward open-topped extrusions.

You can still hold the boom up with a topping lift while rolling the main in, but all the systems we saw used a fixed, solid vang to do the job.

While you can get by without power winches, the whole process of setting and reefing, especially singlehanded, is easier if your winches have power. This is not to say that there isn’t a certain swashbuckling appeal in rolling the sail with one hand cranking the self-tailer and the other easing the halyard (keeping good tension for a nice tight roll).

Though they share the same basic idea, the five systems are significantly different. So are the companies that produce them. Leisure Furl has been around since the early ’90s, and its track record and testimonials are impressive. Schaefer Marine, a well-established hardware company, on the other hand offers a new system born of three years of design and development, but without much time in service. ProFurl engaged in extensive aerodynamic testing and material analysis before introducing a boom-furler just over three years ago. The big French company with dealers in 52 countries has since been energetic in promoting boom-furling to both the general public and among sailmakers.

Furlboom (“designed and built in Australia by Aussie yachtsmen to suit our rugged sailing conditions”) has had a varied career and is now built and  sold by the recently-formed Yachting Systems of America in Costa Mesa, CA. Like Leisure Furl, the company has concentrated efforts on centralizing manufacture and now offers a system that is entirely American-made.

The John Mast (JM) Hi-Low Reefer is imported from Denmark by Lars Pedersen of Bente Trading Company, Mercer Island, WA. Pedersen has long been a boom-furling zealot; he worked with the Danish mastmaker to develop the system. Over 1,500 boom-furlers have been  sold in Europe since 1990.

Leisure Furl Over a decade ago New Zealand sparmaker Don Baverstock first came out with his roll-up system. Today KZ Marine, for whom Baverstock is a consultant, claims that “over 85 % of the new boats launched in New Zealand have our booms.” Says Bill Hanna at Forespar, US manufacturer of Leisure Furl, “Our system began with bigger boats and has evolved into boats closer to the everyday as it has gone along. The point is, we’ve been dealing with loads that are very significant right from the outset.”

Click here to view Leisure Furl images .

The first thing you notice about the Leisure Furl system is that the boom is virtually topless, with a wide “gutter” covered by a clever sliding sail cover. It has an attractively tapered silhouette and affords the convenience of letting you see and service the innards. The two key elements in the furler, however, are its “through-the-mast” drive shaft and the universal joint that joins it to the mandrel at the gooseneck. The “free-floating” universal means maximum power can be applied to rolling the sail. (Leisure Furl is the only manufacturer to use a universal; the other four systems rely on drum drives).

“We found it incredible that we could furl downwind in 50 knots in Bass Strait in the Sydney-Hobart Race,” reports one user.

Chuck Poindexter (Sound Rigging, Essex, CT) has installed 14 Leisure Furl units. “I was surprised to learn when we had a naval architect do the calculations that the drive shaft actually strengthens the mast…by 11% to be exact. When I first got involved it was because a customer wanted me to survey the gear on a boat that had made one and a half circumnavigations. It had a Leisure Furl. I ‘dissected’ the universal and it was perfect.”

Other components include a foot groove halfway from tack to clew. It captures a short bolt rope on the middle third of the sail, holding it to the mandrel. With a loose-floating tack and two-part clew pendant you can roll the sail (similar to the first rolls of a custom-luff headsail) so that the middle rolls in while tack and clew stay loose. What this gives you, we soon realized, was a flattening reef that offers an elegant range of draft control by adjusting the furling line while keeping the halyard tight.

A significant difference between systems is how they attach to the mast. Leisure Furl uses a conventional luff tape, captive in a “self-aligning” feeder that leads to a fixed luff groove. Dr. Robert Leaf, one of the first Americans to put Leisure Furl on his boat, had a big problem “chewing up luff tapes to the tune of three or four a season.” Cutting sails to minimize “pullback” and new, tougher luff tapes seem to have solved the problem.

“It’s how the sail drops at the tack,” Poindexter says. “If it drops right onto the mandrel you’re fine. I’ve been impressed that Leisure Furl has continued to evolve and improve.”

With halyard tension and boom angle you can control how your sail rolls onto the mandrel to a large degree.

Leisure Furl’s chafe problems at the tack seem to be its biggest Achilles Heel, and one to which sailors can address themselves as they learn their systems.

Leisure Furl is moderately encouraging about retrofitting your old mainsail to suit the system, but we wonder if it isn’t something of a false economy to marry top-of-the-line furling gear with a recycled sail, given the critical nature of how the sail fits and is reinforced. Because of the number of components, relationships, and variables, we think Leisure Furl’s “riggers only” installation scheme makes sense, too.

John Mast Hi-Low Reefer This reefer is the departure point from which the others have developed. The main idea at its inception was to make boom furling easy and accessible. Judging by the more than 1,000 boom furlers now afloat in Europe, it worked. The Hi-Lo gooseneck bracket is adjustable, and job one is mounting it to your mast.  The boom is open at its forward end for sail access and transfer. The sail’s bolt rope is inserted in a flexible PVC luff track, which can be fitted to the mast in different ways. The system is simple and works well, but it does not appear as solid as its rivals. (Even the furling drum looked somewhat undersized to us.) When we rolled in a reef (using a handheld electric winch grinder) a pleat formed along the boom. Rolling the sail out to re-reef did the trick, but the full-length battens pushed forward of the mast track and created more friction than we thought reasonable.

Click here to view John Mast Hi-Low images .

With the John Mast and the other in-boom reefers it’s best to reef down to a full-length batten, which can then help support the foot of the sail. Being incompressible, it acts like an outhaul to keep the cloth stretched well aft. “Infinite” reefing between battens is discouraged.

Schaefer Marine Fred Cook at Schaefer says, “We’ve studied some of the problems associated with boom furlers for quite some time and tried to come up with answers.”

To reduce friction the company’s new design incorporates four bearing races, two at either end of the boom. Made of Torlon, the bearings require no lubrication and are meant only to be flushed occasionally with fresh water. Hoisting the sail by hand felt significantly easier than with any of the other systems.

Click here to view Schaefer Marine images .

To handle the transition between the mandrel and the mast groove Schaefer developed a unique and practical  “sugar scoop” guidepiece. While we tested only in medium (12-15 knot) air, it seemed superb at sliding the sail back and forth from mandrel to luff groove.

The drum is mounted on the after end of the boom and worked via a single control line. The gooseneck pivot pin is hefty and made from 316-stainless bar stock. We wondered if the luff groove, a UV-resistant polymer, was as sturdy as the rest of the unit, but from the flogging that we put it through on our test sail it seems ready to withstand realistic abuse.

The track articulates with the boom, and this makes power-reefing (without completely depowering the sail) possible.

It’s good seamanship to take the strain off sail and gear by luffing the sail and/or bringing the boat into the wind when it’s time to reef or douse your mainsail. In a race, or due to navigational needs, however, this isn’t always possible. With the Schaefer system (and all others except ProFurl) you can reef without totally depowering the sail if you must. We think that adds to a system’s versatility and tolerance for error.

ProFurl ProFurl puts its furling drum (very similar to a headsail furler) at the forward end of its open-topped boom. ProFurl’s other salient feature is its  articulating luff track mounted aft of the mast. Positioned to pick up and deliver the luff tape directly from the boom, this set-up has proven chafe-free. According to tests  conducted at France’s Research Center for Nautical Architecture and Industry, the structure actually increases mainsail efficiency by energizing the airflow over the sail.

Click here to view ProFurl images .

As with all of the mainsail furlers, the angle between mast and boom (or tack angle) is critical. Like most of its competitors, ProFurl specifies an angle of “about 87 degrees.” We found that this precision wasn’t absolutely necessary. If the boom is cocked up a bit more than perpendicular it pulls the sail aft and helps it lie smoothly in the boom. Lower the boom end, however, and the sail will bunch at the forward end of the boom, leading it to jam.

ProFurl provides a mechanical vang with a limiting wire: Release the vang and it sets the boom at the right height for furling. Reef the sail, then trim on to adjust vang tension for shape control.

We did all of that, and were rolling a reef in when, in an effort to stop some of the sail’s considerable flogging, we took just the slightest tension on the mainsheet. The sail immediately bulged larger at the forward end of the mandrel until it would no longer roll. We reset and re-reefed with no problem, but the incident made us mindful of  the delicate balance involved in boom furling.

Retrofitting your old sail is possible. One sailmaker advises, however, to “throw out the ProFurl formula for dealing with luff curve. Anything greater than two inches of luff round is too much, period.”

ProFurl USA in Fort Lauderdale says installation of its unit is “relatively simple.” Their elaboration: “An owner with some mechanical savvy and a rivet gun can do it himself, but it takes 16 man-hours and some work aloft.”

ProFurl has recently gone to ball-bearing sheaves, and wire halyards can now be used with the systems, which come with a three-year warranty.

Furlboom One of the secrets of this furler is the way it’s built. “We have gusseted corners that make our entire extrusion structural,” says Dougal Johnson at YSA. “That lets us build a lighter, smaller boom that is still more than strong enough to do the job.”

The Furlboom drive mechanism is mounted on the after side of the mast and connected via a drive chain to the mandrel. We’ve heard of one of these chains failing, and think that provision for a manual backup would improve the system. An excellent feature, and one shared with Leisure Furl, is a locking mechanism that takes the strain of holding the sail in place once the sail is set (or reefed). This ratchet engages under spring tension and is released by a trip line controlled from the cockpit.

Click here to view Furlboom images .

Like most of the other systems, Furlboom employs a claw inside the boom. This guides the sail, both coming and going, and helps to assure a uniform roll. This is one of the several design features that enables Furlboom to handle rigs with considerable pre-bend (up to 8 inches, according to Johnson).

Like many of the systems we looked at, this one has had success on the race course. Johnson points to a Catalina 470 that came in fourth in class in the recent Ensenada Race. Toby Ritter, who took us for a demo sail aboard Tiger Too in Long Island Sound, raced  his Furlboom to Bermuda. However, when you see the slick “automatic” sail cover that you can slide into place once the sail is put to bed, it underscores the fact that you can’t knock boom furlers for cruisability.

Conclusions The thing we liked least about in-boom furlers is the intimidating welter of controls, prohibitions, and caveats that go with them. There are plenty of reports of furlers gone bad, despite the reasonable efforts of their owners. In any case, sailors should be free to explore their limits and develop mastery of them without undue fear of expensive failures.

The thing we liked most was the amount of research and development talent that this rolling target has attracted. Chart the progress from Stoboom to the present and you’ve got a record of innovation and clever design that makes the marine industry look pretty smart.

It’s hard to assign ratings to systems we’ve only evaluated short-term, and not in conditions that might demonstrate the survival of the fittest. But here are some basic assessments:

The John Mast reefer is an older design, and the company has yet to establish an aggressive sales presence in North America. Its unit for a maximum P (mainsail hoist) of 42 feet is $6,850. This includes a boom vang, but not a sail.

ProFurl gets high marks for convenience and quality. A 42-foot P unit retails for $7,920, including a solid vang and boom brake.

Schaefer’s promising unit looks like it will fill the need for a simpler system that people with small to mid-sized boats can use and afford. A reefer to accommodate up to a 44-foot P retails for $7,500. The boom vang is not included.

We think that Furlboom is an excellent value at $7,250 for a 42.6 P length sail, despite the fact that the boom vang is no longer included.

Leisure Furl still strikes us as the most-rugged, best-proven unit. To match up to a 50-foot luff length you will need to pay $9,300. Installation, boom vang, and a new sail will boost that price a lot. If you’re willing to pay the freight, that reefer will render good service and excellent convenience, but our feeling is that Leisure Furl’s competitors have closed the gap and make attractive alternatives.

Contacts— John Mast Hi-Lo, Bente Trading Co., P.O. Box 1621, Mercer Island WA 98040; 206/232-6156; www.johnmast.com . Leisure Furl, Forespar Products Corp., 22322 Gilberto, Rancho Santa Margarita, CA 92688; 949/858-8820; www.forespar.com/catalog/systems/LeisureFurl/leisurefurl.htm . FurlBoom, Yachting Systems of America, 350 Kalmus Drive, Costa Mesa, CA 92626; 714/437-9600; www.furlboom.com . ProFurl, 401 N.E. 8th St., Ft. Lauderdale, FL 33304; 954/760-9511; www.profurlusa.com . Schaefer Marine, 158 Duchaine Blvd. New Bedford, MA 02745; 508/995-9511; www.schaefermarine.com .

RELATED ARTICLES MORE FROM AUTHOR

I have a 1982 sailboat (Classis 35, based in Rome, Italy) with an equally old Hood Stoboom. Except that it’s different from the one you describe: the sail does not furl inside the boom but around it. Were there different models. Incidentally, it works fine, you just insert the handle in the endless furler and roll the sail down while slowing the hailyard with your other hand to maintain some tension in the sail. With the autopilot you can furl the sail single-handed in a couple of minutes or less. I suppose there are some disadvantages with ’round the boom’ furlers since they are so uncommon and would like to hear about them.

Ooops, just realized the article is from 20 years ago. Who am I talking to?

Well, you’re talking to a guy in Maine…..but I didn’t write this article. I was referred to it by friends in the Cape Dory Association because I asked about their experiences with either in-mast or in-boom furlers. I’m thinking of putting some such rig on my Cape Dory 36.

I can make a comment, however, about your own experience. The Pierson Vanguard 33 had a mechanical boom furler rig available as far back as 1963. The current owner, who inherited the boat from her father and has sailed it all those years, said her father never used it….not has she. They both preferred to wrestle the sail down in the traditional manner. Great for the young folks….but I’m 76, and hoping to sail, sometimes singlehanded, for 15 more years.

Hi Jim, and thanks for replying. You don’t say what their problem was, perhaps it depends on the model. As I said, the Stoboom, or at least my Stoboom, contrary to what the article says, does not roll inside the boom but around it making it much less likely to jam. At least mine never does and reefing or pulling down a snap, you just turn the handle and it’s done, no need to pack the sail as the boom moves back and forth under you. I’m sure they must have some modern equivalent but I don’t know about it. Congrats on sailing single-handed.

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In mast 'piece of crap' furling system

• Thread starter Perfect Excuse
• Start date Nov 22, 2015
• Hunter Owner Forums

Perfect Excuse

I have tried everything suggestion in forums except to buy a new sail which I hesitate to do unless I am a guaranteed that it would solve the unfurling problems. Quite frankly, I think the design is crap and I am thinking that the only solution is to sell the GD boat and buy a power boat because that is to which this system reduces me. I am sick of sailing with a 1/4 main and jib. Is there anyone out there that has successfully stopped the main from binding when unfurling? It normally takes two or three hours to get the main out of the mast. I am personally challenging the designer of this crap system or someone from Hunter to provide a solution. Go ahead prove me wrong! Major problem is that the sail binds trying to get it out of the mast. I usually unfurl the main by hand pulling on the sail. Yes, we keep tension on the outhaul when furling and do so very slowly. Yes, I have tried, in desperation, spraying the sail with WD40 as a suggestion from the forum. Yes, I have experimented with different boom angles. Yes, I have taken all bend out of the mast. Yes, I keep tension on the furling line when applying tension to the outhaul. Second, the furling jumps or misses the groves on the furling post. I had just minor problem unfurling until I had the boat re-rigged supposedly to Hunter specs. I have had nothing but problems ever since. It is total BS to have to go up the mast and push the bulge back into the track then pull out another wrap and repeat. Tonight, I am crossing the Sea of Cortez likely under diesel power because a 1/4 main just won't do. Please help save a polite, mild mannered Canadian from creating random acts of power boating!  

Sounds like big problems for sure and don't know where to start but you did say it all started when having it re rigged and why was that done. Yes if and when a sail gets old or worn out or baggy it will cause jamming for sure and you said you add tension when furling in to the mast and that is when most problems cause jamming if you see the sail is not going in nice and flat than yes it will bunch up and will not unfurl out of the mast easy as suppose to. I have 2007 H-36 and only had maybe 2 times jamming because my bad not furling into mast properly but love my inmast and never go any other way. I am not expert and before wasting more $$$$ you need some one who knows inmast to see what is wrong either with the rigging setup or the sail and if the sail is wrinkling than it's not going in properly and is the boom down on the arch properly and the proper bend in the mast specks. Wish I could help more and what year and model Hunter do you have and who made your sail UK or ??????. Jumping do mean the continuous furling line jumps and that line maybe worn out but need a good sailmaker help you find the problem and let the sailmaker come to the boat and see what is going on.  

The good thing is that tonight you are crossing the Sea of Cortez. I had jamming problems with my in mast furling. I had vertical battens which were a problem. I had them re-done at the suggestion of my sailmaker. That helped a lot. But after many cases of jamming I never regained confidence in the system. It seemed to me that the system just didn't roll up the sail evenly leaving too thick a roll in the middle which would jam in unfurling. Furling in a breeze left me as winded as any other task on the boat except for hauling someone up the mast. It also seem to me that the boat was all about the furling. The sail is cut flat so it will furl. I couldn't have the full roach main because of the furling. The boom kicker is set to help the furler. The topping lift? Set for the furler. Luff tension? The Furler. The furling system was soooooo needy. Many others love their's. I feel like something must be different. I never could understand what. There was a post recently about adjustment of the furler tension. I never got to try that.  

Sounds like whom ever did the rigging got something incorrect some time one has to go back to sq 1 and start over forgetting everything in the past you know like getting a divorce only what you left behind will not leave it alone  

Just out of curiosity how's the main halyard. If their is any slack in it,your sail will jam.  

As said above could be anyone of many thinks maybe over looked and start over and check everything over,should not be having that much trouble but if something was done wrong than nothing but problems. Most love Inmast but some times it can be a problem and than I would hate it if I was having problems that you are having and hope you find the fix and fall back in love with it like most of us do. Nick  

Can only guess what might be the problem. We rarely have problems with our sail on our 410. Maybe the sail is stretched and needs replacing? Maybe halyard tension not right? Would it be possible send pics at different staging of furling or unfurling then main?  

Ralph Johnstone

Not familiar with "Piece of Crap" furling systems as mine is a Selden. Obvious question I know, but is the sail furling in the correct rotation for your make of mast ?  

Attachments

This is the way mine was set up. We would leave the boom off to the port side a little to make the feed more fair. Still not easy and in a breeze a two person job. And often as not a source of marital discord. Occasionally frostiness in August.  

Perfect Excuse said: I had just minor problem unfurling until I had the boat re-rigged supposedly to Hunter specs. I have had nothing but problems ever since. Click to expand

charliegrau

I had trouble with my system too...did all the stuff folks recommended...luff tension, halyard tension, etc. What seemed to make the most difference was two things. 1: I lubricated the gears on the furling winch on the mast, and cleaned all the blocks the sheet, outhaul, and furling lines went through. 2: bought a new sail. Works fine now. I can furl/unfurl without winches, and the boom angle and topping lift setting don't seem so critical. A couple of weeks ago I had a "new" issue come up...the outhaul came off the sheave in the end of the boom near the mast..that introduced a huge amount of friction and I couldn't get the sail furled until I discovered and resolved it.  

There are ALOT of things that will effect a successful furl but if a Selden in mast furling system is setup per the directions the sail should go in and out with little issue. I have a very thin triradial laminate main and it is silly how easy it furls and unfurls. It has no battens and the sail holds a beautiful shape. I had the the clew cut three inches shorter than the original, which makes adjustment a bit easier as the boom height position isn't as critical. The sail maker, Z Sails in Ct., also increased the size of the clew roller over the original Doyle. Halyard tension is important. If it is slack you will definetly have a bunching issue and if it is too tight it puts tension on the furling rod. You mention it became more of a problem after someone tuned the rig. I hate to sound this jaded but I would say from MY experiences that only one in five people that work on sailboats in any capacity are actually competent to do so. Find a local sailmaker that racers use and have him or her come take a look. They will tell you what the problem is if they are worth their salt and might even show you a trick or two to get that sail furled and unfurled. Good luck. BTW two one hundred pound neices can furl my main, one tailing the outhaul and one pulling the furling line and it only takes one to unfurl it.  

Sorry you are having such a difficult time with your in-mast furling. I have a 2004 H-36 and I have never experienced the problem you are having. Good luck finding a solution.  

SBO Weather and Forecasting Forum Jim & John

Perfect Excuse said: I have tried everything suggestion in forums except to buy a new sail which I hesitate to do unless I am a guaranteed that it would solve the unfurling problems. Click to expand

Have you adjusted the tension on the furling spindle in the mast as suggested in the Selden In mast Furling instructions ??  

Slab resting is so KISS and reliable I wonder why any one would consider any alternative. Used on boats up to 61ft with no issues (benneteau 61, Dufour 52.5) last boat I sailed on, Auckland to Fiji , we had trouble with the In-mast. It finally completely jammed during a period of 50 -60kn. I had to go up the mast to the spreader. Spent an hour pulling the sail out of the slot. Dangerous and painful. Why not strip out the in mast and go for slab?  

I had the same problem with my '03 Hunter 44 and it took a couple of seasons of trying different fixes before I solved the problem. I assume that your sail is not blown out as this would cause furling/unfurling issues. Here are all the things I did knowing that you accomplished some of them based on your post. 1) Re-tuned the mast to be straight. It was rigged incorrectly by the PO (Selden and rigger recommendation) 2) Maintained outhaul tension when furling as per basic furling technique - with no improvement. 3) Applied waterproof grease to the lower bearing accessible by two round plastic plugs on port side of mast - this helped somewhat (Selden recommendation) 4) Applied dry lube to all sheaves and clutches. Also helped somewhat. 5) THE NUMBER 1 RESOLUTION!!!! For some reason, if you look at all Hunters with furling mains, the outhaul is attached to the boom way too close to the mast on an adjustable slide fitting on top of the boom. The overall result is that when you unfurl the sail it is being pulled down instead of back. This also effects the furling process. I moved that fitting further aft - by about 4 feet to roughly a foot beyond the point where the boom vang attaches. The problem went totally bye bye ever since. It is now a real pleasure to use the system. 6) Some other considerations: a) Everyone is aware of problems caused by a loose halyard, however it is possible to over-tighten the halyard which would cause furling issues. b) The extrusions can be tensioned and relaxed also. If they are too loose or tight it will cause furling issues. The Selden manual covers or you can contact Selden CS directly.  

captainpat said: 5) THE NUMBER 1 RESOLUTION!!!! For some reason, if you look at all Hunters with furling mains, the outhaul is attached to the boom way too close to the mast on an adjustable slide fitting on top of the boom. The overall result is that when you unfurl the sail it is being pulled down instead of back. This also effects the furling process. I moved that fitting further aft - by about 4 feet to roughly a foot beyond the point where the boom vang attaches. The problem went totally bye bye ever since. It is now a real pleasure to use the system.. Click to expand

captainpat said: 5) THE NUMBER 1 RESOLUTION!!!! For some reason, if you look at all Hunters with furling mains, the outhaul is attached to the boom way too close to the mast on an adjustable slide fitting on top of the boom. The overall result is that when you unfurl the sail it is being pulled down instead of back. This also effects the furling process. Click to expand

captainpat said: 1) Re-tuned the mast to be straight. It was rigged incorrectly by the PO (Selden and rigger recommendation) Click to expand

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