Heel is the sideways lean of a sailing boat under the pressure of the wind on her sails, measured as the angle between her mast and the vertical. It is different from list, which is a lean caused by uneven weight, and from roll, which is the rhythmic side-to-side motion caused by waves. Beginners experience heel as the moment the boat tips and the lee rail approaches the water. Experienced sailors treat the heel angle as a speedometer of sorts: every boat has a range of heel in which she is fastest, and most of what a crew does upwind is aimed at keeping her there.
What Causes Heel and What Limits It
The wind pushes sideways on the sails high above the water, and the water resists the keel low below it. The two forces form a heeling moment that rotates the boat about her fore-and-aft axis. Resisting it is the righting moment, which comes from two sources: ballast stability, the weight of the keel swinging out to windward as the boat heels, and form stability, the buoyancy of a wide hull shifting to leeward as the lee side immerses. The boat settles at the angle where heeling moment and righting moment are equal. Add wind and she heels more; reduce sail, flatten it, or move crew weight to the rail and she comes back up.
Why Heel Matters for Speed
A little heel does no harm, and on many narrow or older hulls it lengthens the waterline and reduces wetted surface. Beyond that, heel costs speed in several ways at once. The sails present less area to the wind, roughly in proportion to the cosine of the heel angle. The keel and rudder work at an angle and generate less lift, so leeway increases. The hull’s immersed shape becomes asymmetric and tries to turn the boat to windward, producing weather helm and rudder drag. Most keelboats sail fastest upwind somewhere between fifteen and twenty-five degrees of heel; dinghies and many modern planing designs are fastest almost flat; multihulls should barely heel at all and are at risk if they do.
Controlling Heel: The Depowering Sequence
From the sailmaker’s bench, heel control is sail-shape control. The order in which most crews reduce heel as the wind builds runs like this:
- Flatten the sails: tension the outhaul, backstay, halyards and cunningham to pull depth out of both mainsail and headsail.
- Open the leeches: ease the vang and drop the traveller so the mainsail twists off and spills wind at the top, where its heeling effect is greatest; move the genoa car aft to do the same forward.
- Feather: head up a few degrees in the puffs so the front of the sails just lift.
- Reduce area: change to a smaller headsail or reef, mainsail first on most sloops to keep the helm balanced.
Low-stretch sailcloth makes every one of these steps work better. A woven sail that has stretched full and draft-aft will heel the boat no matter how you trim it; a laminate or load-path sail such as Titanium™ or X-Drive® holds its designed flat shape as the load comes on, so the flattening controls do what they are supposed to.
Cruising and Racing Perspectives
The cruising sailor reefs for comfort and for the boat. Most cruising crews are happiest below about twenty degrees, and the boat is usually faster there too: the rail-down cruiser with a dragging rudder and the galley in disarray is not going anywhere quickly. Reef early, flatten the sails, and heel becomes a pleasant lean rather than a struggle. The racing crew treats heel as a number. An inclinometer or a heel readout on the instruments, a target angle for the conditions, and a helmsman and trimmers working together to hold it are standard. Crew weight on the rail is the first and cheapest righting moment, and hiking hard through a puff while the mainsheet trimmer plays the sheet is the racing rhythm upwind.
Frequently Asked Questions about Heel
How much heel is too much?
On most keelboats, more than about twenty to twenty-five degrees is slower, harder on the helm and uncomfortable. If the rudder feels heavy and the boat rounds up in puffs, you are past the point and should depower.
Can a sailing boat capsize from heel?
A ballasted keelboat has a very high limit of positive stability and will usually round up and spill wind long before it is at risk, though breaking waves can roll any boat. Dinghies and multihulls can capsize from heel alone, which is why their crews work so hard to keep them flat.
Why does the boat heel more with an old mainsail?
Stretched cloth lets the draft move aft and the leech close up, both of which increase the heeling force and weather helm. Flattening controls cannot fix cloth that has lost its shape; a recut or a new sail can.
Heel is the boat telling you how much power she is carrying. Learn her happy angle, keep her there with sail shape before you resort to reefing, and you will sail faster, steer less and arrive with the crew and the crockery in better shape.