Heels and Heeling: The Physics of Looking Good While Going Bad

Anyone who has ever attempted a cobblestone street in 10-centimetre heels already understands, intuitively, that maintaining a steep angle requires disproportionate effort, causes disproportionate damage, and impresses only people who don’t understand the physics involved. Sailing at 45 degrees of heel is the nautical equivalent — except the cobblestones are liquid, the street can swallow you whole, and the heels cost considerably more to replace. Both best enjoyed briefly, and ideally with an audience.

I arrived at this comparison after watching No Going Back — the Clipper Race documentary on Amazon Prime — over a weekend. Twice. It’s a genuinely wonderful piece of television — raw, honest, and occasionally terrifying in the way only the Southern Ocean can deliver. If you haven’t seen it, stop reading this and go watch it. I’ll wait.

What stuck with me wasn’t the storms, or the sleep deprivation, or the moments of quiet beauty at dawn. It was the heeling.

Shot after shot — from drones, from mastheads, from chase boats — showed these 70-foot yachts buried at what looked like 45 degrees, rails under, crew scrambling along the high side. And these boats are skippered by professional captains. People with tens of thousands of ocean miles. People who have done this not once but repeatedly, voluntarily, for a living.

So I sat on my sofa and asked myself the uncomfortable question: Am I wrong?

I’ve spent years telling crew to reef earlier, sail flatter, keep the heel under 20 degrees. I own a Hanse 588. I preach the gospel of the cosine function to anyone unfortunate enough to ask about sail trim. And here were expert skippers — people who could sail circles around me before breakfast — apparently choosing to sail at 45 degrees, race after race, in front of cameras and GPS trackers that would record every decision.

Either they knew something I didn’t, or the drone footage was lying.

With a little shame, I asked someone who would know. A friend — an American captain who races classic yachts in the Mediterranean, the kind of person who has forgotten more about sailing than I will ever learn. I braced myself. I expected a nuanced lecture on apparent wind angles and displacement-mode hull dynamics that would expose my flat-sailing dogma as the oversimplification of a weekend sailor.

Her answer was four words: “Oops — not my thing.”

A professional racing captain — someone who pushes boats hard for a living, on classics with no canting keels, no foils, no CFD-optimised appendages — and 45-degree sailing was simply not in her vocabulary. This encouraged me. If the experts who actually race weren’t sailing at 45 degrees by choice, then the footage was showing something other than optimal technique. I decided to find out what. With maths.

A Brief History of Leaning Over

Sailors have been romanticising heel since long before cameras existed to capture it. The 19th-century tea clippers — Cutty Sark, Thermopylae, Ariel — raced from China to London with every square inch of canvas flying, and contemporary accounts describe them heeled to alarming angles in the trades [1]. The Great Tea Race of 1866 saw Taeping beat Ariel by 28 minutes after 14,000 miles of sailing [2]. What the breathless newspaper accounts failed to mention was that the fastest passages were made in moderate conditions, with the hull relatively upright and the narrow waterline doing what it was designed to do.

The pattern repeats throughout sailing history: the dramatic moments get remembered, the fast moments get forgotten.

But maybe I was the one remembering selectively. Maybe the Clipper skippers understood something about heavy displacement downwind sailing that the textbooks gloss over. So I kept digging.

By the late 20th century, the IMOCA Open 60 class had become the laboratory for pushing monohull performance to its limits. The first boats, appearing in the 1986 BOC Challenge, were aluminium tanks weighing up to 15 tonnes [3]. They heeled. A lot. And they were slow by modern standards.

Then came the canting keel.

The Canting Keel: Engineering’s Answer to “Stop Leaning Over”

Isabelle Autissier’s Écureuil Poitou-Charentes was the first 60-footer to race with a canting keel, in the 1995 BOC Challenge [4]. The concept was elegant: instead of a fixed fin dangling beneath the hull, the keel could swing to windward, shifting the lead ballast bulb laterally and generating massive righting moment without relying on hull form alone.

Michel Desjoyeaux won the 2000 Vendée Globe aboard PRB with a canting keel [5]. The message was unambiguous: the boat that heels less, wins.

By the mid-2000s, canting keels were universal in the IMOCA fleet. The class rules reflected the shift — the old ’10-degree rule’ specified that an Open 60 should heel no more than 10° with movable ballast deployed [6]. The entire engineering trajectory of offshore racing was aimed at one goal: keep the boat flat.

Not encouraging for my “maybe the Clipper skippers are right” hypothesis. But the IMOCA fleet are purpose-built racing machines. The Clipper 70s are heavy displacement cruiser-racers sailed by amateur crews. Different beast entirely. I kept an open mind.

Then came the foils.

The Foiling Revolution: 5 Degrees Is the New 45

In 2013, the IMOCA class introduced hydrofoils [7]. The effect on heel angle was transformative. Modern foiling IMOCA 60s are designed to be sailed as flat as physically possible. As boat speed increases, the foils generate dynamic lift that stabilises the platform, actively reducing heel [8].

Era	Technology	Target Heel	Speed (20 kt TWS)
1986–1995	Fixed keel, water ballast	25–35°	10–14 knots
1995–2012	Canting keel	10–15°	15–20 knots
2013–present	Canting keel + foils	3–8°	26–28 knots

The fastest ocean-racing monohulls on the planet sail at less than 8 degrees of heel. A foiling IMOCA 60 in 20 knots of true wind will do 26–28 knots [9]. A non-foiling boat in the same conditions does 21 [9]. The foiling boat is flatter and faster.

The current IMOCA class rules require that righting moment at 25° of heel must not exceed 25.5 tonne-metres [10] — not because they want less stability, but because the boats shouldn’t need to operate at that angle in the first place.

Fifty years of offshore racing development can be summarised in five words: the faster you go, the flatter you sail.

My hypothesis was not doing well.

But That’s Formula 1. What About the Rest of Us?

Canting keels, hydrofoils, carbon fibre everything, shore teams with CFD simulations and weather routers. These are Formula 1 machines crewed by professional athletes who eat freeze-dried food and sleep in 20-minute cycles. The average weekend sailor watches the Vendée Globe the same way the average commuter watches a Grand Prix — with admiration, awe, and absolutely no relevance to what happens on Monday morning.

So let’s ask the question that actually matters to the 99.9% of us who sail production boats, anchor in crowded bays, and have a partner aboard who did not sign up for the Southern Ocean.

Should we heel?

Don’t ask your partner. I already know the answer. And they’re right.

I own a Hanse 588. It’s 17.2 metres of Judel/Vrolijk-designed cruising yacht, 22,800 kg displacement, 7,500 kg of lead in a bulb fin keel, with a beam of 5.2 metres [11]. It was not designed by people trying to win the Vendée Globe. It was designed by people who understand that the person you love needs to be able to walk to the galley without a harness, that a glass of wine should remain in its glass, and that “adventure” is not a synonym for “structural failure.”

But the same physics that told IMOCA designers to keep their boats flat applies to a Hanse 588 with exactly the same mathematical rigour. The cosine function does not offer a recreational discount.

The Forces Your Rig Is Carrying (And Wishes It Wasn’t)

When a yacht heels in equilibrium, the righting moment — the torque generated by the keel’s ballast pulling down while the hull’s buoyancy pushes outward — exactly balances the heeling moment created by wind on the sails. To calculate what’s happening inside the rig, we start with the righting moment and work backwards to the forces the shrouds must carry.

The righting moment at heel angle θ: RM(θ) = Δ × g × GZ(θ), where GZ is the righting lever. At small angles, GZ ≈ GM × sin(θ). At larger angles, deck edge immersion modifies this — for the Hanse 588’s wide 5.2m beam, the deck edge goes under at roughly 40°, after which form stability diminishes [12].

In equilibrium: F_heeling × heeling arm × cos(θ) = RM(θ)

The cap shroud — through the geometry of a fractional rig where the attachment is ~20m high and the chainplate ~2.5m outboard — must carry approximately 4.4 times the total heeling force [13]. The shroud’s small angle to the vertical gives it poor mechanical advantage, so it compensates with enormous tension.

Parameter	At 15° heel	At 45° heel	Factor
GZ (righting lever)	0.36 m	~1.0 m	2.8×
Righting moment	81 kN·m	224 kN·m	2.8×
Required heeling force	6.8 kN (694 kg)	25.7 kN (2,621 kg)	3.8×
Cap shroud tension	30 kN (3.1 tonnes)	113 kN (11.5 tonnes)	3.8×
Safety factor (12mm rod, BS ~120 kN)	~4.0	~1.05

At 15 degrees, the cap shroud is loaded to about a quarter of its breaking strength. The rig has comfortable margin.

At 45 degrees, the cap shroud is carrying 11.5 tonnes — approaching the breaking strength of typical 12mm rod rigging. The safety factor has collapsed from 4.0 to barely above 1.0. Every component in the load path — chainplate bolts, tang welds, clevis pins, the mast wall itself — is at or near its design limit. One shock load from a wave, one moment of dynamic amplification, and something gives.

At 15 degrees, you have margin. At 45 degrees, you have a prayer.

The Drag Tax: What the Hull Pays for Your Heroism

While the rig is fighting for its life, the hull is paying its own penalty. The Hanse 588’s underwater lines — carefully shaped by Judel/Vrolijk for a moderate upright attitude — don’t take kindly to being rotated 45 degrees.

1. Form drag from waterline distortion. When the hull heels, the immersed shape becomes asymmetric. The leeward side presents more volume, the windward side less. The transom, designed to exit the water cleanly at low heel, begins to drag. Research from the Delft Systematic Yacht Hull Series shows measurable resistance increases even at moderate heel angles [14], and the penalty grows non-linearly.

2. Induced drag from leeway. At 15° of heel, a well-trimmed cruising yacht makes approximately 3–5° of leeway [15]. At 45°, with the keel canted over and operating at reduced efficiency, leeway increases to 8–12°. Induced drag is proportional to the square of the leeway angle — tripling the leeway means roughly nine times the induced drag from the keel alone.

3. Wetted surface and appendage drag. The rudder finds itself partially ventilated. The keel root-hull junction creates turbulent flow separations. Even the prop aperture adds parasitic drag it wouldn’t otherwise contribute.

Heel angle	Form drag	Induced drag (leeway)	Total drag increase
15°	+5–8%	+10–15% (leeway ~4°)	+15–20%
30°	+15–25%	+30–45% (leeway ~7°)	+45–70%
45°	+35–50%	+60–90% (leeway ~10°)	+100–140%

At 45 degrees of heel, total hull resistance roughly doubles. And the driving force? At 15°, you retain 96.6% of your drive. At 45°, you retain 70.7% — a 27% reduction [17]. So: 27% less drive and 100% more drag.

The Force You Forgot: Drag Loads Back Into the Rig

The 11.5 tonnes on the cap shroud was already alarming. But those were only the sideways forces — the athwartship loads from heeling. There is a second axis of loading that gets dramatically worse with heel, and most sailors never think about it.

The sails don’t just push the boat sideways. They also push it forward — that’s the whole point. The driving force acts on the sail plan, attached to the mast, at the centre of effort some 11 metres above the waterline. Meanwhile, the hull’s hydrodynamic drag acts at the centre of lateral resistance, roughly 1.3 metres below the waterline. This creates a fore-aft bending couple: the sails push the top of the mast forward, while the water holds the bottom of the hull back.

The backstay resists this longitudinal moment. The mast itself absorbs it as axial compression — the rig is, structurally, a column being squeezed between the sails pulling the top forward and the hull holding the bottom back.

At 45 degrees of heel, hull drag has doubled. That means the longitudinal bending moment on the mast — the force trying to bow it forward — also increases dramatically. The backstay must carry more tension. The forestay gets dangerously loose, losing its function of keeping the mast on-axis. And the mast, already under 3.8× more lateral load from the shrouds, is simultaneously under significantly more axial compression.

VMG: Where the Argument Ends

Velocity Made Good — the component of boat speed in the desired direction — is the only number that matters. On a cruising yacht like the Hanse 588, upwind VMG peaks at a heel angle between 15° and 22° [18]. Beyond 25°, VMG drops off a cliff. At 45°, the boat is:

• Slower through the water (less drive force, more drag)
• Making more leeway (keel efficiency halved)
• Pointing worse (distorted hull, excessive weather helm)
• Losing VMG in every dimension

The boat feels fast at 45 degrees — the noise, the spray, the adrenaline — but it is haemorrhaging performance in every measurable way.

Your partner, incidentally, has been saying this for years. They didn’t need the cosine function. They had common sense.

The Magnificence of Reefing

Here is where the physics becomes genuinely beautiful.

Reefing is the most misunderstood manoeuvre in cruising. Many sailors treat it as surrender. This is precisely backwards. Reefing is the single most effective performance optimisation available to a cruising sailor.

Consider the Hanse 588 beating to windward in 25 knots of true wind.

	Full sail, 30°	Reefed, 15°	Change
Sail area	157 m²	110 m²	−30%
Cap shroud tension	6.6 tonnes	3.1 tonnes	−53%
Hull drag increase	+55%	+18%	−37 pp
Leeway	~7°	~4°	−43%
Drive per m² of sail	cos(30°) = 0.87	cos(15°) = 0.97	+11%
Mast compression	High	Moderate	Significant reduction
Weather helm	Heavy	Balanced

You reduced sail area by 30%. But shroud loads dropped by 53%. Hull drag dropped by more than a third. Leeway nearly halved. Each remaining square metre of sail is 11% more efficient. And the mast compression from drag forces dropped in proportion, restoring the buckling margin that was haemorrhaging under full sail.

This is the non-linearity that makes reefing magnificent. Heel angle depends on the square of wind force for a given righting moment curve. Rig loads depend on the righting moment at equilibrium, which grows with the sine of the angle. Drag depends on the square of leeway. Every one of these relationships compounds in the wrong direction when you’re overpowered — and compounds in the right direction when you reef.

The result: a reefed boat that is often faster to windward than the same boat with full sail. You are doing more with less — less area, less load, less leeway, less drama — and arriving sooner.

And your crew can walk to the galley. Your partner will confirm: this matters.

What To Do When the Heel Won’t Stop

Theory is beautiful. But when the gust hits at 0300, the boat lurches to 35 degrees, and the lee rail disappears beneath a wall of black water — nobody reaches for a trigonometry textbook. So here is the practical version, in order.

Step 1: Ease the mainsheet. This is embarrassingly simple and yet most sailors skip it in favour of Step 6: hold on and hope. Easing the main is instant. It requires no crew movement, no one going forward on a heeled deck, no coordination. The boom swings out, the leech opens, the heeling force drops. You can do it from the cockpit with one hand. Do it first. Do it now. Think later.

Step 2: Reef the main. This is the real solution. Everything else is a band-aid. A first reef at 15 knots apparent, a second at 20+. As we saw above, a 30% reduction in sail area buys you a 53% reduction in shroud load. That is not a compromise — it is an upgrade. If you’re wondering whether it’s time to reef, it was time ten minutes ago. Every experienced sailor will tell you this. None of them learned it from a book.

Step 3: Reduce the headsail. Furl the genoa to 80%, or change down to a working jib. A partially furled genoa has a poor shape — baggy, with the draft too far aft — but a badly shaped small sail beats a perfectly shaped sail that’s drowning your bow.

Step 4: Flatten what remains. Outhaul hard on. Backstay tension. Cunningham down. These controls move the draft forward and open the leech, depowering the sails without reducing area. It’s the fine-tuning that separates a reefed boat that still sails well from a reefed boat that wallows.

Step 5: Only now — consider a course change. And here, intuition misleads. The instinct is to bear away — turn downwind, escape the pressure. But bearing away when overpowered trades a heel problem for a control problem. On a reach, it puts you into a broad reach or run where an accidental gybe, a broach, or a death roll are real possibilities. Running before heavy weather, with following seas, is often more dangerous than beating into it. If anything, a gentle luff — heading a few degrees into the wind — unloads the sails immediately without changing which side the boom is on. Course changes are tactical decisions that depend on sea state, what’s downwind, and where you need to be. They are not a depowering reflex.

The sequence matters. Ease, reef, reduce, flatten, then — and only then — consider where to point the bow. The boat was designed to be depowered with its sails, not with its rudder.

So Were the Clipper Skippers Wrong?

No. They probably weren’t.

The Clipper 70s are heavy displacement boats sailed by largely amateur crews in conditions that don’t allow for fine-trimmed, flat-and-fast sailing. When you’re running before 40 knots in the Southern Ocean on a 33-tonne yacht with a crew still learning to gybe — sometimes 45 degrees of heel isn’t a choice. It’s what happens between the gust hitting and the reef going in. The skippers know this. They’ve made the calculation: push hard in the gusts, accept the heel spikes, claw back the seconds that matter over 40,000 miles.

What they are not doing is sailing at 45 degrees because they think it’s fast. They’re sailing at 45 degrees because the Southern Ocean has opinions of its own, and the Clipper 70 doesn’t have a canting keel, hydrofoils, or a magic button that makes physics optional.

And here’s the detail no sailor watching No Going Back will have missed: at every port of call, the repair crews were waiting. Shipping containers full of spare parts — rigging, sails, winch components, hydraulic rams — lined up on the dock before the boats had even tied up. The Clipper Race doesn’t pretend the boats arrive unscathed. It budgets for breakage. The skippers can push their boats to structural limits because there is an industrial repair operation standing by to put everything back together before the next leg.

This is the critical difference between the Clipper Race and your summer cruise to Sardinia. A Clipper skipper who pushes a shroud to 90% of its breaking strength knows that a rigger with a container of Navtec rod is waiting in Cape Town. When your shroud fails in the Strait of Bonifacio, your repair crew is you, a Leatherman, and whatever you can improvise from the lazarette. The economics of breakage are fundamentally different when someone else does the fixing.

The Healing Power of Heeling

And yet — and I mean this sincerely — perhaps 45 degrees of heel serves a purpose that has nothing to do with boat speed.

Many of the Clipper Race crew are not career sailors. They are teachers, engineers, accountants, office workers — people who woke up one morning and decided that their lives needed something that a spreadsheet could not provide. They signed up, often at considerable personal cost — and I do mean cost, the Clipper Race is not a cheap ticket — for the specific purpose of being terrified, exhausted, and pushed beyond every limit they thought they had. The heel — pun genuinely not intended — might be less about the boat and more about healing.

There is something real and valuable in that. The ocean doesn’t care about your job title or your mortgage. At 45 degrees of heel in the Southern Ocean, the only thing that matters is the rope in your hands and the person next to you. For people escaping years of fluorescent lighting and quarterly reviews, that rawness is the whole point. The heel is not a performance metric — it’s a measure of how far they’ve come from the life they wanted to leave behind.

And maybe — just maybe — 45 degrees of heel is exactly what they paid for. Not the optimal VMG, not the fastest elapsed time, not the gentlest passage. The experience. The story they’ll tell at every dinner party for the rest of their lives. The moment the drone caught them rail-down in the Southern Ocean and they felt, for the first time in decades, completely alive. Try putting a cosine function on that.

I respect it enormously. The Clipper Race gives people an experience that transforms them, and no amount of trigonometry diminishes its worth.

But — and this is the point for the rest of us — it’s an experience, not a technique. The 45-degree moments are the emotional highlight reel. They are not the sailing lesson.

The Physics Don’t Negotiate

At 45 degrees of heel, you have lost 29% of your driving force, your hull drag has doubled, your keel is generating half its designed lateral resistance, your cap shroud is loaded to 11.5 tonnes laterally while your mast is being compressed by doubled drag forces — and your rig’s safety factor has dropped from a comfortable 4.0 to a theological 1.05.

At 15 degrees — that boring, visually unimpressive, film-crew-disappointing angle — you are within the design envelope, making good speed, pointing well, carrying 3 tonnes on the cap shroud with a safety factor of 4, and your crew can move around the boat without three points of contact.

The entire history of competitive sailing — from the tea clippers to foiling IMOCAs — points in one direction: flatter is faster. The underlying physics has been the same since Newton.

A boat heeled at 45 degrees is not sailing hard. It’s sailing through a moment that will pass — and if it doesn’t pass, you’ve made a mistake. The right response isn’t to brace and endure. It’s to ease the sheet, put in a reef, and let the boat accelerate back to the angle it was designed for.

Less sail. Less heel. Less load. More speed.

Whether it’s 10 centimetres or 45 degrees, the lesson of the heel is always the same: just because you can hold the angle doesn’t mean you should. The cobblestones always win eventually. So does the sea.

I thoroughly enjoyed No Going Back. Those skippers are better sailors than I will ever be. And the crew who sailed with them came home changed — healed, perhaps, by the heeling. But the next time you see that glorious aerial shot — rail buried, spray flying, crew braced against the angle — remember: the skipper didn’t choose that moment. The Southern Ocean did. And somewhere in the hours the drone wasn’t flying, and the daring cameraman had earned his bonus, that same boat was doing 9 knots at 15 degrees of heel, perfectly trimmed, utterly uncinematic, with a container of spare parts waiting at the next port.

That’s where the race was won. And the wine glasses were still upright.