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Just Furl It: The Case for Furling Mainsails

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 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.


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."


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.


"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.


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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