How to: A Trouble-free Furling Main - Sail Magazine

How to: A Trouble-free Furling Main

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Both bluewater sailors and coastal cruisers have taken to in-mast furling mains...Both bluewater sailors and coastal cruisers have taken to in-mast furling mains...

Both bluewater sailors and coastal cruisers have taken to in-mast furling mains...Both bluewater sailors and coastal cruisers have taken to in-mast furling mains...

In-mast furling systems have come a long way. Forget the hollow-leeched, baggy triangles we first saw decades ago; a well-specced modern in-mast system can offer more sail area than a traditional slab-reefed mainsail, so the performance gap has narrowed significantly. Nevertheless, just about every sailor has heard a horror story about in-mast furling, and many are swift to condemn these furlers without ever having actually used one.

Yes, in-mast furling can have its issues, but most of these are caused by operator error. We live in an age where we expect everything to just work. Let off one line, pull another and the mainsail should disappear like the money from your wallet when you take kids out for an ice cream. And when it binds or jams, it can’t possibly be your fault.

So what is the best way to furl the mainsail? “Carefully,” replies sailmaker Jeremy White. “It’s a mechanical system, and it must be operated correctly.”

The ability to tailor sail area to the conditions is a major advantage of furling mainsails

The ability to tailor sail area to the conditions is a major advantage of furling mainsails

The right way to furl

Before explaining how to furl the sail, let’s look at how the system works. Inside the mast is a grooved aluminum extrusion into which the luff of the mainsail slides, in much the same way as a furling genoa. The difference is that there is not a lot of room inside the mast for a rolled sail, and most issues are caused by the sail not furling properly so that the furl becomes too bulky, or the sail rubs on the inside of the mast.

Here’s how to get a successful, tight furl every time. Looking down from the top of the mast, the foil usually (or always on Seldén masts) revolves anti-clockwise. Put the boat on a starboard tack, with the wind slightly forward of the beam. That way, the sail will feed in and around the furler; on a port tack the full height of the sail would be dragged over the sail groove in the mast, adding friction.

Next, ease the mainsheet and then ease the outhaul a little and start to roll the sail away. Always look at the sail as you’re furling, so you’ll be able to notice issues as they happen, and not after you’ve, say, wound an inch-thick clump of sail through a half-inch gap. If your sail has full-length vertical battens, make sure the first batten is parallel with the mast when it enters, and if you’re reefing, leave the batten just outside the mast groove. Don’t keep too much tension on the outhaul, as this will drag the foil aft in the mast and bend it, causing the sail to rub against the inside of the mast, again causing 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 causes more—yes, you’ve guessed it—friction. Repeat the ease/furl until only the UV protection strip is showing. 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 using the lines to furl, don’t be afraid to furl the sail at the mast with a winch handle—try it sometime, it is remarkably easy. If you are having to do anything different, like raising the boom or hopping on one leg while praying to the god of furling sails, it’s worth looking at your system in detail for problems.

Both bluewater sailors and coastal cruisers have taken to in-mast furling mains...

Both bluewater sailors and coastal cruisers have taken to in-mast furling mains...

If it’s not working

If you’ve followed this procedure and are still having problems, there are a number of things to check. First, take a look inside your mast to see which way your system should furl. Put a winch handle in the furling mechanism at the mast and turn it the direction indicated to furl and make sure the sail is going into the mast. Clicking over the ratchet at the mast before it’s time to furl will ensure it always rolls in the right direction.

The biggest cause of problems is typically the sail itself. How old is it and what material is it made from? Furling mainsails are cut flatter than conventional slab-reefing sails; stretch in the cloth makes for a baggy sail and all that draft in a baggy sail has to go somewhere. If your Dacron sail is blown out and has a deep belly, think about getting a new one, since you’re fighting a losing battle. As the belly furls it doubles the thickness of the furl and causes an uneven shape to the furled sail.

Excess halyard tension can also cause the fabric to bunch up, as vertical creases at the mast cause the sail to fold over itself—release the halyard until you have horizontal creases at the luff, then add just enough tension to remove them.

...but when foul-ups happen, they can lead to big problems

...but when foul-ups happen, they can lead to big problems

The next thing to look at is friction. If the lines that lead to your furling gear and outhaul make multiple turns through multiple blocks, make sure all the angles they have to go through are as wide as possible and that all blocks and sheaves are running smoothly. A good wash with freshwater and a squirt of McLube SailKote can work wonders. So can replacing tired old blocks with new low-friction items.

Another thing you can do is double-check the backstay tension, as the foil inside a bent mast remains straight and will bind at the apex of the mast’s bend. In practice, it’s best to set up your backstay tension when the rig is tuned and not to mess with it from then on.

Finally, if all the above fails, it’s worth a call to your local rigger to check the foil tension. If the foil has gone slack, then it is bending and rubbing on the mast as you furl.

Screen-Shot-2018-06-21-at-12.04

Think about Sails

If you’ve bought a new-to-you boat, question how good its sails really are. Most production-boat sails are built to a price, not for longevity or performance. A new sail will almost certainly improve your enjoyment of your boat. But what should you be looking for when buying a new sail? There has been much advancement in furling mainsail design—improved materials, vertical battens and increased sail area among them. Elvstrøm’s Fat Furl system, for example, has a larger sail area than that of a comparable slab-reefing sail. The new cruising laminates from lofts like North, Doyle, UK and Quantum are also thinner, stronger and furl tighter than ever before.

Whichever sailmaker you choose, get the best quality material you can afford. 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. The luff of a laminate sail on a 45ft yacht, for example, might only stretch ¾in over its life, whereas a Dacron sail might stretch as much as 6in. That excess sailcloth has to roll up in the same space as when it was new.

If you want maximum sail area and sail support, full-length vertical battens are the way to go. These support the leech and permit a good full roach. They will also support the sail over its full height, providing extra rigidity while it’s being furled. Shorter vertical battens, on the other hand, can leave the sail unsupported, causing “hinging” at their base when furling.

For those without the budget or desire for a battened sail using modern materials, a Dacron sail with a hollow leech still offers many advantages over a slab-reefing system—primary among them ease of reefing and being able to have exactly the right amount of sail area out for any given conditions.

If you are commissioning new sails, consider getting them silicone-coated as this will help the sail slide over itself, making the furl inside the mast tighter.

In-mast furling has got a bad rap in the past but used properly and with a little care, there’s no reason why such a system shouldn’t give you trouble-free sailing for years to come. Increasing numbers of boats are circumnavigating with them, and most boatbuilders now offer them as an option. 

For more on sails and sail trim, click here.

Sailing photojournalist Graham Snook has sailed many boats with furling mainsails, and likes them just fine

September 2018

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