The In’s and Out’s of In-Mast Furling

By Captain Jack Dusendschon

“What? Your mainsail doesn’t go up and down… it goes in and out?”
Yes, In-Mast Furling can definitely cause seasoned sailors new to the system to gaze in wonderment. In-Mast Furling has some new aspects for a sailor to get acquainted with but we at Sailing Florida Charters & Sailing School feel the positives strongly outweigh the negatives. That’s why all of our monohull keelboats in the Sailing Florida fleet have In-Mast Furling mainsails.
As a side note, the catamarans in our fleet still use traditional mainsail hoist halyard systems due to their fully-battened mainsails, which don’t allow the sail to be wrapped inside the mast. However, this process is greatly enhanced with the use of motorized winches on all of our catamarans. The American Sailing Association Cruising Catamaran class (ASA 114) is a great way to learn how to effectively raise and lower a catamaran’s mainsail with minimal use of your crew.
One of the most important benefits of In-Mast Furling is the minimal amount of times that you send a crew member up on the deck. No more struggling with the waves to keep your balance as you collect up and lash the mainsail to the boom after you drop it. No halyard shackle to connect and disconnect. Also, you won’t have to constantly tighten the mainsheet to keep the boom from swinging into your crew up on the cabin top as they zip up the sail cover. Another plus with In-Mast Furling is the ease of handling – gone is the strenuous cranking of the winch as you slowly pull the halyard and raise the heavy mainsail to the top of the mast.
Many of our keelboats have a system inside the mast that looks and works much like a corkscrew, which doesn’t require any trips to the mast. (This is generally true of the Jeaneaus and Beneteaus in our fleet.) The rest of our monohulls, including the Hunters, Catalalinas, and a few Jeaneaus, have a winch located on the mast, under the boom, which requires a switch to be easily flipped before you pull out the sail. This switch on the winch also needs to be flipped back to lock the winch after the sail has been fully extended, which readies the winch when it’s time to roll the sail into the mast at the end of the day. Just two quick trips to the mast, with the first time easily done at the dock.
In-Mast Furling is much like using your jib furler in that you pull the inhaul/furling line to wrap the sail around itself, although the mainsail gets wrapped inside the mast. With your jib, when it’s time to use the sail, you release the furling line and unwrap the sail by pulling on the jib sheets. The concepts are all the same with In-Mast Furling, yet there are some different lines with different names and perhaps the use of a winch located on the mast below the boom.
The first step is to ready your lines by uncoiling them and checking that they all have figure-8 stopper knots tied on the free end of the line – the mainsail sheet, the outhaul line, the inhaul line, as well as the jib/genoa sheets and the jib/genoa furling line. The outhaul should be wrapped once or twice around the winch, ready to pull the mainsail out of the mast.
The inhaul cleat/rope clutch should also be released to allow the sail to come out when you pull on the outhaul. I’m reminded of the great tale of Dr. Doolittle and his two-headed llama, Pushmi-Pullyu… When Pushmi wanted to go one way, Pullyu had to go backwards, and vice-versa, much to the llama’s consternation! To reduce you and your crew’s stress, remember to release one line to pull on the other, during both the roll-out and the roll-in process, with both the mainsail and the jib sail.
If your boat has a winch on the mast, be sure to switch it to ‘Out’ – sometimes labeled as ‘Free’. Disengaging the gears of the winch allows the main to come out nicely with no friction from the mast winch.
This is a good time to communicate with your crew… “We’re going to pull out our main first, by releasing the inhaul line and pulling on the outhaul line… when I say so. And then we’ll turn the boat, get it sailing on the main alone, and pull out the jib.”
You’ve waited until now to release the main sheet line, so you don’t have the boom swinging around during the planning process. You should now release the main sheet by 6 inches or so to allow the sail to come out of the mast without tension on the leach, or back edge, of the mainsail, which could cause bunching of the sail along the mast track – this step alone will make everything easier.
You’ve also kept your diesel running in forward gear, yet backed down to idle forward, so your helmsman still has comfortable control of the boat, steadied at a slower speed. Your helmsman should now be instructed to turn the boat towards the wind.
The mainsail should get unwrapped first… remember, it is called the main sail. I always feel sympathy for the helmsman when the jib is pulled out first in a fresh breeze… as the boat steers rapidly away from the wind, you’ll hear the faint cries of, “I can’t steer!” A boat heading upwind needs the energy over the keel to be in control, not at the front of the boat pushing the bow away from the wind.
The mainsail wraps into the mast at a slight angle to starboard; thus, to allow the sail to come out of the mast fully luffing, the boat should be turned so the wind is hitting the boat at 10 degrees to starboard. An excellent way to explain this is to turn the boat directly into the wind, referring to the wind indicator at the top of the mast or on the instruments, and then turn the boat to port until the wind just starts to hit the right cheek of your face.
The crew should start pulling the outhaul, and the mainsail will begin unrolling out of the mast. It’s important to realize that if the bow of the boat drifts off from the wind direction, the crew should stop pulling the sail out until the helmsman puts the boat back on course. Keeping the sail luffing is key! Having the boat sailing and heeling while pulling the sail out puts a lot of stress on the sail… and the helmsman. Ha!
One of the most asked questions is how far to pull the sail out. The easy answer is, “light wind, curvy sails… heavy wind, flat sails.” This is due to the principle best explained by the mid-1700’s mathematician, Daniel Bernoulli. In light wind, more curve, also known as depth or draft, in our sail increases the energy created by the high pressure on the windward side of the sail moving toward the low pressure on the leeward, or downwind, side of the sail.
In heavy wind, to reduce the energy in the sail that is trying to push the boat sideways, and to reduce heel, a flatter sail will make sailing more comfortable, especially while sailing upwind. In lighter wind, more curve will make you feel like you’re actually moving; once again, the sympathy I feel for the crew on a boat in light wind moving sideways due to the skipper cranking the main’s outhaul as tight as possible.
Now it’s time to reduce the noise of your luffing mainsail and get this boat moving! Have your helmsman turn the boat downwind to about 45 degrees from the wind… roughly the angle of your thumb and forefinger when making a ‘V-shape’. This is a good time to have a crew member move forward safely on the cabin top, windward side, please… and move the switch on the winch to ‘In’ – sometimes labeled as ‘Ratchet’. Now the gears inside the winch are engaged and you’re ready to pull the sail in on a moment’s notice. Another crew member can coil up your inhaul, outhaul, and main sheet, keeping things tidy for the next step.
Many sailors will keep the boat pointed into the wind while pulling out the jib, but you’ll find that it’s easier if the boat is actually moving close-hauled… the headsail will roll out like butter! As a side note, this is much kinder to your sail cloth – every time the sail smacks into the mast reduces the lifespan of your sail.
Turning the engine off is an option at this point, but I like to leave it on. If the helmsman gets distracted and swings the boat up into the wind, the engine still allows the helmsman to have control of the boat and get it back to a close-hauled point-of-sail.
Just like the main, release the inhaul/furling line and pull the jib out using the jib sheet on the same side as the sail – releasing the other jib sheet will also facilitate things and keep everyone on the boat smiling! Once again, ‘lighter wind, curvy sails… heavy wind, flatter sails’. And yes, you will notice that with this guideline, the boat will not point as close to the wind in lighter wind conditions… but as one of my sailing mentors told me early on, “Only three things matter with sail trim… boat speed, boat speed… and boat speed.” Ha! Keep the boat moving and in maximum control… everyone will be happier.
This is a good time to discuss reefing, or reducing the size of the sail, when the wind speeds increase. Most monohulls will benefit from reefing by increased handling upwind, reducing heel, and keeping everyone onboard confident and smiling. Depending on the length of your boat and the amount of ballast on its keel, when the wind approaches 16 to 18 knots, a reef is usually in order.
If your boat carries a genoa (a larger headsail that extends aft of the mast), the first step is generally to remove the overlap of the genoa with the mainsail by rolling the genoa up so the clew is forward of the mast. This reduces the amount of wind flowing past the leeward side of the main, reducing the low pressure, with the end result of less heeling and reduced weather helm, or the tendency of the boat to turn towards the wind. This is easily done while close-hauled, with one crew member easing off the working jib sheet, and another member pulling on the furling line.
If the wind is already blowing hard, most sailors will put a reef in their jib as they roll it out the first time, keeping tension on the furling line and cleating it when the sail is only 60% to 70% unfurled.
It’s important to note that this is not how you should reef a mainsail with In-Mast Furling. The key difference is that it’s necessary to pull the sail all the way out of the mast, and then reef the sail by pulling the inhaul and rolling the sail evenly into the mast. Sure, there’s quite a bit of noise, and the crew member’s trip to the mast to switch the winch to ‘In’ or ‘Ratchet’, but the possible damage to the sail if you don’t pull it all the way out first can be drastic. I have seen many mainsails where the sail was reefed at the time it was rolled out of the mast, which caused an uneven amount of sail coming out of the track and ripped the sail along the leach. The larger amount of sail cloth at the foot of the sail gets pulled out quicker by the strong wind, which causes tension along the leach and the fabric near the head to bunch up and catch in the mast track. A severely-ripped leach at the beginning of your sailing day is obviously a huge headache.
You’ve had a great day on the water… and now it’s time to roll up the sails and head in. Everything just simply gets done in reverse. Turn the boat close-hauled – 45 degrees to the wind – making sure you have plenty of water in front of you! Be sure to start the engine and push the throttle to idle forward so you overlap your power sources.
Ease off the main sheet one to two feet, reducing heel and taking tension off the leach, or back edge, of the sail. Put your jib furling line around the winch and start winching the sail in, wrapping it around the forestay. An additional crew member applying tension to the leeward jib sheet will assure the sail wraps nicely. A quick coiling of the furling line and jib sheets and then on to the main.
If your boat has a winch on the mast, if you have not already done so, make sure the switch is on ‘In’ or ‘Ratchet’. Now your inhaul line has control of the sail. Once again, point your boat towards the wind, with the wind slightly hitting the starboard bow. Release your outhaul, maintaining slight tension, and pull the sail into the mast with the inhaul.
And now, what I fondly call “The Captain Jack Method’… once the clew of the sail is roughly one or two feet from the mast, stop and cleat your inhaul. Pull on your outhaul and you’ll see the sail move a small amount into the mast, but your objective is to make the sail tighter inside the mast, like a tightly-wrapped burrito. You’ll then release the inhaul and bring it the rest of the way in. This quick procedure will definitely make everyone happier when you easily pull the mainsail out the next day you sail.
An important note – most sails have a thicker triangle of woven cloth with high UV and abrasion protection at the clew… don’t pull this into the track on the mast or you will most surely wish you hadn’t when it’s time to pull the sail out again! Stop just short of this thicker canvas; it’s designed to be left out of the mast.
Another consideration when pulling the mainsail into the mast is the tension on the leach cord, or ‘pucker cord’, which runs the entire length of the leach, or back edge of the sail. In-Mast Furling mainsails can’t have battens in them to add shape to the sail because they won’t roll into the mast. Thus, sail manufacturers have reduced the amount of roach, the area of sail aft of a line between the head and the clew. However, in higher wind strengths, the leach will still tend to luff, causing noise and disrupted air flow off the back of the sail. If you pulled on your leach line slightly to reduce this turbulence, make sure you release it before you pull the sail in. If you don’t, you’ll inevitably spend some quality time trying to get the sail back out again as the leach will have bunched up deep inside the mast.
There you have it, the in’s and out’s of In-Mast Furling. Although it may at first glance seem more difficult than just pointing the boat into the wind and yanking on the halyard, the safety benefits and ease of handling outweigh the added considerations. You and your crew will definitely benefit from the increased communication and knowledge that you will gain in learning this system. All of the first three monohull class/certifications at Sailing Florida Charters & Sailing School – ASA 101: Basic Keelboat Sailing, ASA 103: Basic Coastal Cruising, and ASA 104: Bareboat Chartering – will instruct you as to how to properly and confidently use the In-Mast Furling system. Happy sailing!