Handling Asymmetric Spinnakers & Code Zeros: A Guide to Top-Down Furling

In a Nutshell

Top-down furling is a specific system designed to tame "flying" or free-hoisting sails like asymmetric spinnakers & Code Zeros. It works by rolling the sail from the top downwards, which makes these powerful but unruly sails far easier and safer to handle from the cockpit. For many cruising sailors, this system has transformed how they sail off the wind, offering a convenient alternative to traditional dousing socks or a cumbersome spinnaker pole.

A selection of headsails on this solent cum cutter rigged cruising boat

A top-down furler, two bottom-up furlers and an in-mast furling system on this impressive cruising boat

What's a Top-Down Furler and How Does It Work?

Why Bother with a Code Zero or Asymmetric Spinnaker?

Getting to Grips with the Top-Down Furling System

What Are the Downsides to Top-Down Furling?

Summing Up

Frequently Asked Questions

What's a Top-Down Furler and How Does It Work?

If you're already familiar with the roller furler on your boat's headsail, you've seen a "bottom-up" system in action. The sail's luff is attached to a foil, and when you pull the furling line, the entire sail rolls up from the tack to the head.

A top-down furler is a different beast entirely. It uses a special, high-tech anti-torsion cable. When you turn the furling drum at the bottom, the torque is transferred all the way up the cable to a swivel at the top of the sail. This starts the furling process from the head and works its way down to the tack, much like rolling down a window blind. The tack of the sail is attached to a free-spinning swivel, which allows the sail to roll up cleanly and tightly without bunching. This unique method is essential for a sail like an asymmetric spinnaker, which has a very full, free-flying luff.

Why Bother with a Code Zero or Asymmetric Spinnaker?

If you've ever found yourself with a light breeze and your boat just sitting there, barely moving, you'll appreciate the power of these sails. A Code Zero or an asymmetric spinnaker is designed to fill that gap, helping you maintain speed when it's too light for your main sails.

Code Zeros are light-air reaching sails. They're designed to be used in very light winds and can help you sail a tighter angle to the wind than a traditional spinnaker, often as close as 60-70 degrees. They're basically a giant, lightweight jib, built for speed on those long reaching legs.
Asymmetric Spinnakers (sometimes called gennakers) are true downwind sails. With their round, full shape, they're at their best when the wind is coming from a broad reach or even further aft.

A top-down furler takes the terror out of flying these sails. Instead of having to hoist a big, flapping sail that's trying to get away from you, you just unroll it from a neat sausage shape. And when the wind picks up or you need to get the sail down fast, you simply furl it away again from the cockpit.

Feature	Code Zero	Asymmetric Spinnaker
Primary Use	Light-air reaching	Downwind sailing
Luff	Straight and taught	Free-flying and curved
Ideal Wind Angle	50-90 degrees apparent	90-160 degrees apparent

Getting to Grips with the Top-Down Furling System

Using a top-down furler is pretty straightforward once you've done it a few times. You'll typically hoist the furled sail on its own halyard, attach the tack to a short bowsprit or tack point, and then unfurl it using the continuous line.

For the furl to work properly, you need to sail on a broad reach with the mainsail blanketing the sail. This reduces the wind pressure and allows the sail to roll up neatly. As you furl the sail, the sheet trimmer has to ease the sheet out at a controlled rate. My best advice here is to have a little tension on the furling line and a little tension on the sheet. It's a bit of a balancing act at first, but you'll get the feel for it quickly. You'll know it's working when the sail rolls up into a tight, neat sausage from the top down.

What Are the Downsides to Top-Down Furling?

While top-down furlers are a fantastic bit of kit, they do have a few drawbacks.

Cost: The biggest one is the price. A quality top-down furling system with its anti-torsion cable is significantly more expensive than a traditional dousing sock.
Complexity: The system requires proper rigging and specific handling. You can't just throw it on a boat and expect it to work without practice. Getting the halyard and tack tension right is crucial.
Storage: You can leave the furled sail hoisted for short periods, but for longer passages, it's a good idea to douse it and bag it. The sail's large size means it can be a bit of a pain to get it on deck and ready to go.

It’s important to remember that these systems are for managing downwind sails, not for reefing your mainsail in a blow. For a complete rundown on how to shorten sail safely, you'll want to head over to our pillar page, Reefing a Sail: The Ultimate Guide to Control & Safety at Sea. These systems are designed for light-wind sails, a different purpose from the everyday sail shortening methods like slab reefing or in-mast furling. For a full breakdown of those crucial systems, see our guide on Sail Reefing & Furling Systems.

Summing Up

Top-down furling has opened up a world of sailing to cruisers who might have been intimidated by large downwind sails. While the systems for headsails and mainsails are about safety in heavy weather, this is about unlocking your boat's potential in light air. It's a real game-changer for short-handed crews, offering the performance of an asymmetric spinnaker or a Code Zero with the convenience of a modern furler. Ultimately, it’s about making your sailing life easier, faster and more enjoyable.

Article written by Dick McClary, RYA Yachtmaster & Yachting Journalists Association (YJA) member.

Frequently Asked Questions

Can I use my boat’s headsail furler for a Code Zero or asymmetric spinnaker?

No, you can't. Your headsail furler is a bottom-up system that works because the sail's luff is attached to a rigid foil. A Code Zero or asymmetric needs a top-down system to furl properly because of its free-flying, convex luff.

Do I need a bowsprit for these sails?

Not always, but it's highly recommended. Attaching the sail to a bowsprit gets it out in front of the boat's bow and rig, which gives it a cleaner airflow and better shape.

Is a dousing sock or a furler better?

A furler is generally seen as safer and easier for a short-handed crew, as it allows for sail handling from the cockpit. A dousing sock is a simpler, more affordable option but requires more effort and a crew member on the foredeck.

How do I prevent the sail from twisting during the furl?

The key is to maintain a constant, slight tension on both the furling line and the sheet as you furl the sail. Furl on a broad reach with the mainsail blanketing the sail to keep the wind from distorting it.

What’s the difference between an asymmetric and a symmetric spinnaker?

An asymmetric is a three-cornered sail flown without a pole, while a symmetric spinnaker is a four-cornered sail that requires a spinnaker pole to project it to windward when sailing dead downwind. Asymmetrics are easier to handle but can't sail as deep downwind as a symmetric.