Reefing means making a sail smaller so the boat stays upright, balanced and under control as the wind builds. Every sailor needs to know how to do it, and the best sailors do it early. A well-reefed boat is usually faster, drier and far more comfortable than one carrying too much canvas, because it heels less, steers more easily and stops rounding up in the gusts (a symptom of excessive weather helm).

Quick answer: to reef a mainsail, depower the boat (head up or heave to), ease the vang and mainsheet, lower the halyard to the reef mark, secure the new tack, re-tension the halyard, pull the clew reef line tight, then trim the sail back in. To reef a furling headsail, ease the sheet slightly and roll in the furling line, keeping light tension on the sheet. The rest of this guide explains when to reef and how to do it on each system.

What Reefing Is and Why It Matters

Sail area is power. In light air you want all of it; in a strong breeze the same sail area makes the boat heel excessively, slide sideways and fight the helm. Reefing trades some of that power for control. Reducing the mainsail lowers the center of effort, which cuts heel and weather helm, and a smaller headsail reduces the load on the rig and the crew.

If you are still learning the parts of the rig, our guide to the names of sails on a sailboat covers the luff, leech, tack, clew and other terms used below.

When to Reef: Signs and Wind Thresholds

The old rule still holds: the first time you think about reefing is the time to do it. Reefing is easy in 15 knots and hard work in 25, so don’t wait for the gust that lays the boat over.

Signs you are overpowered

• The boat heels well past 20 degrees and the leeward rail is in the water. Most cruising boats sail fastest at moderate heel.
• You need lots of rudder to hold a straight course and the boat rounds up in gusts (strong heel and weather helm).
• You are constantly easing the mainsheet or traveler and the main is luffing for long periods.
• The crew is uncomfortable, tired or anxious, or the autopilot is struggling.
• The forecast shows the wind building, a front or squall is approaching, or night is coming.

Rough wind guide

Every boat is different, so learn your own numbers and check your sailmaker or builder’s recommendations. As a starting point for a typical 30 to 40 foot cruising sloop sailing upwind:

Apparent wind (upwind)	Typical sail plan
Up to about 15 knots	Full main and full headsail
About 15 to 20 knots	First reef in the main; full or slightly rolled headsail
About 20 to 25 knots	Second reef; headsail partly rolled
About 25 to 30 knots and above	Third reef or storm sails; small headsail or staysail

Downwind, the apparent wind feels much lighter than it really is, so reef earlier than you think you need to. If you bear away in 18 knots of apparent wind and then have to turn back upwind, you may suddenly be in 25 knots or more. Light-displacement boats and boats with large genoas usually reef sooner; heavy cruisers can often carry more sail. Read more about forecasting in our weather tips for boaters.

Reefing Systems: Slab, Single-Line, In-Mast and Furling Headsails

System	How it works	Pros	Cons
Slab (jiffy) reefing	Lower the halyard, hook or pull down the tack cringle, haul the clew down with a reef line	Simple, reliable, good sail shape	Usually needs someone at the mast unless lines are led aft
Single-line reefing	One line pulls down both tack and clew from the cockpit	Done from the cockpit	High friction, line can tangle; best on smaller boats
In-mast furling	Mainsail rolls up inside the mast	Infinitely variable, very easy	Poorer shape, risk of jams if furled wrongly
In-boom furling	Mainsail rolls onto a mandrel in the boom	Keeps battens and good shape	Boom angle must be right or the sail rolls badly
Roller-furling headsail	Jib or genoa rolls around the forestay	Quick and easy from the cockpit	Partly rolled sail loses shape
Hanked-on headsails	Change to a smaller sail	Best shape for the conditions	Foredeck work in rough weather

Many boats combine a slab-reefed main with a furling genoa. If you are unsure which headsail you have, see jib vs genoa.

How to Tuck a Slab Reef Step by Step

Before you leave the dock, check that the reef lines are rove through the correct clew cringles and that you know which line is which. Mark the halyard at the right height for each reef so you can lower it quickly. Then, when it is time:

1. Prepare the crew. Brief everyone, put on lifejackets, and clip on if anyone will go forward to the mast.
2. Depower. Head up to close-hauled with the headsail drawing and ease the mainsheet until the main luffs, or heave to. On a fractional rig you can also sail under headsail alone while you reef.
3. Support the boom. Take up the topping lift if you have one so the boom does not drop when the halyard is eased. A rigid vang does this for you.
4. Ease the vang and mainsheet so the boom can rise and the leech can come down.
5. Lower the halyard to your mark until the reef tack cringle reaches the gooseneck.
6. Secure the tack. Slip the cringle over the reefing hook (ram’s horn) or pull the tack reef line tight.
7. Re-tension the halyard until the horizontal creases along the luff disappear.
8. Pull the clew reef line down and aft until the new foot is tight along the boom. This is what gives a flat, efficient reefed sail.
9. Ease the topping lift, trim the mainsheet and re-tension the vang.
10. Tidy the bunt. Tie the loose fold of sail with reef ties around the foot of the sail only, not around the boom, using a reef knot or slipped reef knot. They keep the sail tidy; they should not carry load.

With practice, a crew of two can tuck a first reef in a couple of minutes. A second reef works the same way using the next set of cringles and reef line.

Single-line reefing

With single-line systems, ease the halyard and haul the reef line alternately, a little at a time. Watch both ends of the boom: the tack and clew should come down together. Friction is the main problem, so keep the blocks clean and the line in good condition.

In-mast and in-boom furling

Furl an in-mast main with the boat on a close reach or beating with the main just luffing, never with the sail pressed hard against the spreaders. Ease the outhaul under control while you wind in the furling line, keeping light tension so the sail rolls tight and smooth. A loose, creased roll is the main cause of jams. In-boom systems need the boom at the angle specified by the manufacturer, usually close to 90 degrees to the mast, so the luff feeds evenly.

How to Reef a Furling Jib or Genoa

1. Ease the sheet until the sail just starts to luff. Don’t let it flog wildly.
2. Pull in the furling line, keeping light tension on the sheet so the sail rolls tightly. Use a winch only if it moves smoothly; if it suddenly gets stiff, stop and find out why.
3. Re-trim the sheet and move the sheet lead (car) forward as the sail gets smaller, so the sheet still pulls down on the leech as well as aft.
4. Make the furling line fast so the sail cannot unroll by itself.

A heavily rolled genoa loses its shape and becomes baggy. If you regularly sail with the genoa more than about a third rolled, consider a smaller headsail, a sail with a foam luff pad, or a separate staysail for strong winds.

Main or headsail first?

Aim to keep the boat balanced. On a masthead rig with a large genoa, rolling some genoa first is often right. On a fractional rig the main provides most of the drive, so reef the main first. If the boat shows too much weather helm, reef the main; if it feels lifeless with lee helm, you may have reduced the main too much. Our guide on sailing without a jib explains how each sail affects balance.

Shaking Out a Reef

When the wind eases, reverse the process carefully:

1. Untie all the reef ties first. Hoisting with a tie still in place can tear the sail.
2. Head up or ease the sheet to depower the main, and ease the vang.
3. Ease the clew reef line, then release the tack.
4. Hoist the halyard to full height and tension the luff.
5. Trim the sail and reset the vang and outhaul.

Shake out reefs one at a time and only once you are sure the wind has really dropped. It is better to be a little under-canvassed than to reef again ten minutes later.

Common Reefing Mistakes

• Waiting too long. Reefing in a building gale is harder and riskier.
• Forgetting the vang or topping lift. A tight vang stops the boom rising; no topping lift lets the boom drop on the crew or into the water.
• Loose halyard or clew. A scalloped luff or baggy foot gives a deep, powerful sail exactly when you want a flat one. Check the result with your sail telltales.
• Reef ties around the boom. If the clew line slips, the ties take the load and tear the sail.
• Reefing on a run. The main is pinned against the spreaders and won’t come down. Head up first.
• Not moving the headsail car after rolling the genoa.
• Never practising. Practise in light air so the routine is automatic when it matters.

Reefing at Night and Offshore

Offshore sailors often reef before dark as a routine, even if the wind is moderate. A short-handed crew working at the mast at night is more at risk than one sailing slightly slower. Lead reefing lines aft where possible, and know how to heave to so you can reef in a calm, stable boat. Our sailing tips for beginners cover more basics of boat handling.

How to Reef a Sail: Summary

Reef early, reef in a controlled way, and practise in calm conditions. For a slab-reefed main the sequence is depower, support the boom, ease the vang, lower the halyard, secure the tack, tension the luff, pull down the clew, then trim. For furling sails, roll under light tension and adjust the sheet lead. A properly reefed boat sails flatter, steers more easily and keeps both crew and rig safe when the wind picks up.