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Everything You Need To Know About Sailboat Heeling

A sailboat will  heel  or  lean over at an angle when you sail in any direction other than almost straight downwind. The wind pressure on the sails will force the vessel to a sideway angle, while the righting moment of the keel’s weight and lateral resistance in the water counteracts this energy. When a sailboat tilts over like this, it is called  heeling .

For a beginner, heeling over can be intimidating and feel unnatural, and I have seen many white faces on their first sailing trip . I certainly remember my heart beating a bit faster during my first sailing experience.

In this article, I’ll explain everything you need to know about sailboat heeling. I’ll xplain why it happens, and how to control and use it to your advantage. We’ll also cover how to adjust your sails and rigging to reduce or increase heeling, and how to deal with different conditions effectively.

Why do sailboats heel over?

To be able to sail at any angle to the wind, a sailboat needs to take advantage of the wind’s force in the sails to make it move forward.

When air hits the sails at the right angle, it generates lift. Some of the energy will force the boat forward, and the rest will try to push the boat sideways through the water. However, the sailboat’s keel prevents lateral movement sideways to a certain degree, and the remaining energy will make the boat move forward at a sideway angle.

The closer to the wind you sail, the more you heel. As you fall off and start pointing away from the wind, the boat’s heeling angle decreases. Eventually, you will reach a point where you are sailing directly downwind, and the keel doesn’t need to work as hard to provide lateral resistance and move the boat forward because the wind is already blowing in the direction you want to go.

What is the optimal heeling angle?

Some boats like catamarans, trimarans, and planing racing monohulls are designed to be sailed primarily upright. Most cruising monohulls, however, are displacement boats and have to heel to go forward when sailing at an angle to the wind.

Most cruising sailboats generally have an optimal heeling angle of 10-20 degrees. When sailing close-hauled , you might have to push it down to 25 degrees to keep your forward motion, but heeling too far will probably make you slower. 10-15 degrees is a good compromise between performance and comfort.

We have a simple method to find the best heeling angle for our particular boat in the conditions we are sailing. When the boat heels over, it will try to turn itself back up by turning into the wind. This is called  weather helm .

To keep the boat straight on course, we compensate for the weather helm by countersteering with the rudder, which also generates more lift up to a certain point. Compensating too much makes the rudder act like a break, which will slow us down.

Keeping the angle of the rudder between 2 and 7 degrees gives you a nice balance between performance and heeling angle. On many cruising boats with a steering wheel, keeping your center mark between ten and two o’clock is an excellent rule of thumb.

How do you control heeling on a sailboat?

There are several ways to control and reduce the heeling angle when sailing, and there are good reasons why we want to.

A typical scenario is when you are sailing with a good balance on the helm at a decent heeling angle. Then, all of a sudden, the wind increases, and the boat starts to heel excessively. As a result, you get more weather helm as the boat tries harder to round up into the wind, and the wheel gets hard to control.

The boat is now overpowered, and you are heeling too much.

Luckily, we have three easy ways to prevent the boat from heeling too much:

• Adjust sail trim
• Adjust course
• Reduce sail area by reefing

Let us take a look at each of our options.

1. Adjust the sails

De-powering the jib or genoa by easing off the sheets or letting out the mainsail traveler is a quick way to regain control over the boat. If you sail on a reach, easing the sheets will turn the sideway force into forwarding force. When eased far enough, you are actively releasing the wind out of the sail, and the sail will start to luff.

When sailing downwind, easing the sheets is the only viable way to de-power the sails quickly, as you might be unable to turn the boat around and back into the wind. If you get too overpowered, you risk broaching, which can be dangerous.

If the wind increase was just temporary gusts, you might want to either actively work on releasing and pulling the sheets, often referred to as “pumping,” or settle for lower performance and slacker sheets. When you sail upwind, this works as a quick way to de-power the sails, but working with the sheets for every gust means you will lose height and not point well.

This article from Savvy Navvy explains broaching very well and has several videos displaying different broaching situations.

2. Adjust the course

Turning the boat into the wind will take power out of the sails and is easy to do when sailing upwind. When we sail close-hauled, we have a trick we can apply to increase our performance.

A powerful ” feathering ” technique is simple to apply and works well when sailing upwind. Instead of easing the sheets in a gust, you keep the sheet tension and steer the boat higher into the wind. As the apparent wind angle moves aft when the strength increases, we use this to our advantage to keep our height by sailing to the angle of our heel instead of the angle of the wind.

I wrote an article about how high a sailboat can point that you might be interested in :  How High Can A Sailboat Point?

Feathering requires an active and focused helmsman, and as soon as the gust stops, you have to fall off again to keep your heeling angle and not lose power in the sails.

Continuing to fall off and bear away while easing off the sheets will also calm the boat down and make it turn more upright. This technique is helpful if you get tired or feel like you are pushing yourself and the boat too hard. Adjusting the course to a downwind point will also reduce the apparent wind speed and can be a good solution if you need a break.

3. Reduce sail area by reefing

When the wind isn’t just gusting but steadily increasing, it is about time to reduce your sail area by reefing. If the boat is heeling more than 20-25 degrees, you have too much canvas exposed, and reefing at this point will make you sail faster, safer, and more comfortably.

It is advisable to reef earlier rather than later as it can be hard to control the boat when it gets overpowered. Pushing limits while sailing is only for experienced people, and any seasoned cruiser agrees that a conservative approach to increasing weather is smart. If you ask yourself, “Should I take a reef?” the answer is always a big yes.

The reef can easily be shaken out if your hunch was wrong or if it was just some gusts or a short squall. Conservative and safe are the magic keywords. Even if you aren’t anywhere near the maximum heeling angle, less sail area can give you a much more comfortable ride with less heel, even if it means sacrificing a little bit of speed.

How far can a sailboat heel before capsizing?

I get this question a lot, especially from those sailing for their first time. When sailing close hauled, we sometimes push the boat to the point where it may seem like we will tip over and capsize. I often see faces going white when the toe rail dips into the water… Luckily, sailboats are designed very cleverly.

The wind can not heel a sailboat over far enough to capsize. Sailing boats are designed to round up into the wind if they are overpowered   and heeling too much.

It is nearly impossible to fight the helm hard enough for the boat to tip over, even if you want to. And if you could, the rudder will eventually lose grip in the water, and the boat will round up until it points upright into the wind with its sails fluttering.

However, you want to be careful when sailing downwind, especially with a spinnaker. As you are sailing off the wind, your apparent wind is lower than your true wind, and sometimes, it can be hard to notice wind increases. Since the boat doesn’t heel over as much as it does upwind, everything might seem fine until you suddenly are overpowered and going too fast.

Getting overpowered can lead you to a broach, which can knock you over in extreme cases, especially if the waves are big. A keelboat will turn itself around again, but you will probably lose your mast and sails, and we want to avoid that!

Monohull sailboats do heel, and they have to in order to generate forward momentum. How far they heel dramatically depends on the boat. They won’t tip all the way over, even if it may seem so, and will usually round themself up into the wind, where you will be left upright with fluttering sails.

Heeling too much is unsuitable for comfort or speed, and finding a good balance of sail area and weather helm will give you the smoothest ride. Be careful, reef early, and don’t push the limits. Sail your boat conservatively until you gain more experience, and remember to enjoy yourself on the water.

If you want to learn more sailing basics, visit my beginner’s guide here.

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Skipper, Electrician and ROV Pilot

Robin is the founder and owner of Sailing Ellidah and has been living on his sailboat since 2019. He is currently on a journey to sail around the world and is passionate about writing his story and helpful content to inspire others who share his interest in sailing.

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Sailboat Heeling Explained In Simple Terms (For Beginners)

If you are new to sailing, then there are many sailing-related terminologies that you will need to learn.

One of those terms is ‘heeling.’ In this article, we will explain what sailboat heeling is and how to control your sailboat when it heels over.

Here is What “Heeling” in Sailing Means:

Heeling is the term used for when a sailboat leans over to either side (port or starboard) in the water by the excess force of the wind. Heeling is normal and counterbalanced by the sailboat’s keel or the crew’s weight distribution on a dinghy.

Table of Contents

What Exactly Makes A Sailboat Heel?

All sailboats are designed to heel, but a sailboat heels over when there is too much wind in the sails, forcing the boat to lean over and lose the harnessed wind power to move it forward.

As a boat heels, the wind pressure on the sails decreases because the sails present a smaller area and less resistance to the wind. The further the boat heels (or leans over), the less pressure.

In addition, boats with a keel have lots of ballast, or weight, to keep them upright in all but the strongest of wind or hurricane conditions. All sailboats will heel or lean over in strong winds, sometimes so far that the rail will dip into the water, and waves will wash onto the deck.

Heeling is simply a part of sailing, and many sailors enjoy it, especially when racing.

How Do I Keep My Sailboat From Heeling?

While all sailboats are designed to heel, sailors can use various techniques to reduce the amount of the angle of the heeling.

These techniques include the following:

Feathering Upwind – 

One of the quickest and easiest techniques a skipper can do in a strong gust of wind is to steer the boat a bit more into the direction of where the wind is coming.

This is called feathering upwind. Doing this releases or spills the wind out of the sails and decreases the wind’s pressure on the sails. This will cause the sails to flap and make a lot of noise (called luffing).

Luffing the sails too much can cause damage to the sails, so this technique is a temporary quick fix and not a long-term solution.

Easing the Mainsheet or the Traveler – 

Another quick technique is to change the angle of the mainsail so that it releases more wind and eases the pressure on the sail.

You can do this by letting out the main sheet (easing the mainsheet) or releasing or easing the traveler control sheet. Both methods will change the angle of the mainsail, releasing the wind pressure and causing your boat to sail more upright.

After a strong gust of wind has passed, you will be able to pull in the mainsail again quickly, to carry on sailing on course.

Reefing the Sails – 

Reefing the sails is a technique used to see or feel that the wind is building or getting stronger. Reefing entails making your sail area smaller, which will work differently on different boats depending on the boat’s set-up.

Reefing the headsail or jib will depend on whether the sailboat has a roller furler or hank on sails. If the boat has hank on sails, you will need to change the headsail to a smaller sail or even a storm jib. Today, most sailboats are equipped with a roller furling headsail, making the headsail sail area smaller.

You can ease the headsail sheet and pull on the roller furler out hauler to roll in the sail a couple of times. This is the equivalent of changing to a smaller sail.

Reefing the mainsail is a little more complicated. Mainsails generally have 2 – 3 reefing points which are stitched in when the sails are made.

The mainsail will need to be partially dropped to access these reefing points, but first, you will need to turn the boat to face the oncoming wind to take the pressure off the sail.

Once you have partially dropped the mainsail, you will need to hook in the reefing point at the mast, haul in the corresponding reefing line, and then retain the main halyard, which is the rope that holds up the mainsail.

How Much Should A Sailboat Heel?

Every sailboat is different, so the exact heel angle for each sailboat will differ.

However, the answer is probably somewhere between 15 and 25 degrees for a comfortable ride in real terms. Thirty degrees is considered the maximum heel for a keel sailboat, depending on the boat’s specific build, design, and characteristics.

Multihulls or catamarans need to be sailed at minimal heel angles; otherwise, they risk capsizing.

But practically, there is a much simpler way to know when your boat is heeling over too far. If you have to fight the steering, otherwise known as the helm, you are heeling too far, and you will need to adjust your sails or course concerning the wind.

How Much Heel Is Too Much?

Similarly, how much heel is too much will also depend on the type of sailing you do. Long-distance cruising, where your boat is your home, will typically involve less heeling than a racing monohull rounding the cans.

However, the amount a sailboat should heel is not opinion. All sailboats are designed to sail at a specified angle of heel. Each sailboat design is for a specific purpose, whether racing, cruising, or somewhere in between, and at their optimum heel angle, there is a minimum wet surface on the boat.

The sails are at a maximum exposure to the wind. When you are sailing and are not at the desired angle, the sailboat is not performing at its full potential.

In addition, if your boat is heeling too much, the boat will become difficult to steer and will slow down. So it’s better to make the necessary adjustments to make yourself and your crew more comfortable and go that little bit faster!

How Far Can A Sailboat Heel Before Capsizing?

For the sake of this article, when we refer to sailboats, we are referring to sailboats with keels and heeling.

Unlike small sailing dinghies, sailboats are designed to heel over without capsizing.

A sailboat is designed to comfortably heel at a certain angle, usually between 15 – 25 degrees. Heeling over more than this is uncomfortable and slows the boat down.

Generally, sailboats with keels can not tip over or capsize under normal sailing conditions. This is because of the weight in the keel. The weight of the keel has been designed to counterbalance the force of the wind in the sails. Plus, the more a boat heels over, the less pressure there is in the sails, and the keel will bring the boat to face into the wind where there is less pressure on the boat overall.

However, this does not mean a sailboat cannot capsize. There are stories of sailboats being knocked down in big waves and strong winds, but this is often temporary as the sailboat will often self-right or come upright by itself.

Extreme conditions such as gale-force winds combined with big seas, too much sail out, and waves crashing over the boat and flooding the cockpit may all combine to capsize a sailboat.

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What To Do When a Sailboat Is Heeling Too Much (Explained)

Sailing is a fun activity for many people, but it comes with the innate prerequisite of being on the water rather than on stable ground. Aspiring captains must learn how to navigate and operate a boat while it rocks around in the water, which means dealing with things like heeling (i.e., leaning too far to the left or right). What do you do when your boat is heeling more than you can handle?

When a sailboat is heeling too much, you can ease or let out the sails to stop them from catching as much wind. This should greatly reduce heel. You can also redistribute weight on the boat to balance it out or use a boat that naturally heels less.

In this article, I will go into detail on some of the things you can do to mitigate how much a sailboat heels, as well as some other related topics. Read on if you’d like more information on sailboat heeling and how to reduce it.

Table of Contents

How a Sailboat is Made Can Affect Heeling

One of the biggest factors in how much a sailboat can heel is simply how the boat is made. Everything from the shape of the keel to the size of the boat impact how easily and safely it can heel.

If you find that your boat is consistently heeling more than you would like, it may just be how that particular boat is made. Some people actually prefer a sailboat that can heel easily, especially those who compete in boat racing, because it can increase a boat’s speed by allowing the sails to catch more wind.

As such, if you have a choice in the matter, try to look for a sailboat that’s made with stability in mind. Some boats are made specifically to handle heeling better and maintain stability, which will likely be an advertised feature as well as one that’s more in demand for recreational sailors.

The Keel Can Affect a Sailboat’s Propensity to Heel

Even if you don’t have the option of trying a different boat, you should still look yours over, especially the keel , which is the protruding piece at the bottom of the boat. 

The keel can vary greatly in appearance depending on what it’s built for, but some boats have keels specially designed to reduce heeling through means like catching on the water and counterbalancing the vessel.

You might not be able to easily replace or modify a sailboat’s keel, but you can at least check to make sure it’s working as it’s supposed to. If something important is damaged or broken off, this could impact your boat’s ease of control, especially when it comes to heeling.

Adjust the Sails to Reduce Heeling

The sails are the primary cause of heeling in a sailboat. 

A boat heels when its sails catch enough wind to pull it to the side and make it lean. This is usually fine but can put stress on the mast and risk capsizing your vessel in extreme cases.

The easiest way to stop this is by simply lowering the sails. If there’s nothing for the wind to catch on, your boat shouldn’t heel much, if at all. While this is a temporary solution unless the boat has another form of propulsion, it’s effective nonetheless. 

If the wind picks up while you’re out sailing and it starts causing your boat to lean more than you expected, taking down the sails for a while will let you wait it out.

Use a Motor When the Wind is Too Strong to Reduce Heeling

Speaking of alternative forms of propulsion, it’s a good idea to have a backup for when the weather doesn’t agree with sails. This way, any time a heavy wind starts tugging your sailboat around more than you’re comfortable with, you can just pull the sails in and start up the motor.

A boat being propelled mechanically can also go faster than one powered by the wind in its sails under the right circumstances. If you want more options for fast travel, this is another good reason to consider installing a motor on your boat. 

Just keep in mind that using both the sails and motor at once won’t necessarily make you go any faster.

Redistribute Weight to Lessen Excessive Heeling

Lowering the sails may be the best way to stop a boat from heeling, but this also means you will be going nowhere fast until the wind calms down unless you have another form of propulsion. 

If you want to reduce how much your boat is heeling without slowing down your sailing experience, one easy thing you can do is redistribute the weight on the boat so that it counteracts the wind pulling on the sails.

If your boat is being pulled to one side, have all passengers stand or sit on the opposite side to counterbalance it. If you don’t have any other passengers or this isn’t enough, try moving heavy cargo instead. This is unlikely to completely stop a boat from heeling, but it can mitigate the impact and limit how far the boat will heel.

Will a Sailboat Tip Over?

It can be difficult for passengers to deal with a boat heeling a few degrees more than they’re used to. After all, most people are accustomed to being on solid ground where the floor beneath them doesn’t shift and tilt at awkward angles. However, the concerning part for some is the idea that their sailboat could tip over and capsize.

A sailboat will tip over under the right circumstances. However, this is very unlikely unless the boat is in heavy wind or rough water, and many sailboats are designed to prevent heeling too much. Some sailboats are also able to right themselves when capsized.

Because capsizing is a possibility, a lot of sailboats have safety precautions implemented to help deal with excessive heeling. This doesn’t mean you should sail out into storms with reckless abandon, but it might put your mind at ease while sailing to know that your sailboat is probably made to stay balanced and even flip itself back over in the event of being capsized.

Check out the video below to find out more about reducing the heel angle on a sailboat:

What To Do When a Sailboat Is Heeling Too Much – Conclusion

It’s perfectly normal for sailboats to heel, but this can cause problems in more extreme cases. Not only is it difficult to walk around on a deck that’s slanted sideways, but it can also put the sailboat at risk of capsizing if the boat heels too much.

Fortunately, there are several things that can be done to mitigate how much a boat can heel as well as allow it to heel more safely. The suggestions made in this article are the easiest ways to “right the ship” as it were if heeling too much.

Bryan is a Las Vegas resident who loves spending his free time out on the water. Boating on Lake Mohave or Lake Havasu is his favorite way to unwind and escape the hustle and bustle of the city. More about Bryan.

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What is Angle of Heel on a Sailboat

And, what Angle of Heel on a Sailboat is acceptable?

What is heeling over on a sailboat?

Heeling over or “heeling” on a sailboat is when it leans over.

Why does a sailboat heel over and why doesn’t it tip over?

Remember your tommee tippee cup? It had a rounded bottom and a weight loaded into the rounded bottom. No matter how much water you put in the cup, the weight at the bottom made sure the cup stood upright – and the rounded bottom meant that if you pushed it over, it would stand right back up.

Your finger pushing sideways on the top of the cup is just like the wind acting on the sails. The wind acting on the sails puts pressure on the sails. Pressure over the entire area of the sails creates a force. The greater the area, the greater the force, and the stronger the wind, the stronger the force. The distance the force is collectively acting on the sails is about 1/3 of the way up the sails. This point is called the center-of-pressure. This is like your finger pushing all the wind’s force at that center-of-pressure point. The sailboat, like the tommee tippee cup has no choice but to lean (heel) over.

The propensity for the sailboat to heel over depends on the height (distance) of the center of pressure above the water line. The physics formula for this is force x distance which equals a physics term called “moment” (not like a moment in time). The “moment” can be considered as the same as “torque” or even easier – as the “tipping force” or (heeling force). The greater the distance and force – the bigger the tipping force.

In high wind conditions, you can lower the center of pressure by spilling some of the wind out of the top of the sails by twisting out the sail at the top (done by easing the mainsheet which allows the boom aft to rise – thus creating less tension on the leech of the sail and allowing the top to twist out).

Twisting out the top of the sail has a double effect. There is less sail area presented to the wind at the top. This means a lower center-of-pressure (less height) and less area – giving rise to less tipping moment.

Another way to lower the center of pressure is to reef the sail (partially lower it). This also acts to reduce the area of the sail. Less area and less height of the center-of-pressure reduces the tipping force. Here is an image showing reefing and twisting effect on the tipping moment. The image also discusses how twisting and reefing moves the center-of-pressure forward. This has the added benefit of reducing what is known as weather helm – the boat wants to automatically turn up into the wind.

What stops the sailboat from completely tipping over?

A balance between gravity acting on the weighted keel and the wind force on the sail stops the boat from completely tipping or heeling over. As the boat heels over, the sail area is not upright and so less sail area is presented to the wind. Also as the boat heels over, gravity acting on the weighted keel that is rolling upwards with the heel of the boat creates a force to stand the boat back upright. At some point, both forces meet in agreement and compromise with a defined heeling angle.

Imagine the weighted keel is just like how your Tommee Tippee cup uses gravity to force the boat to stand back upright. Thus it becomes a balance between the boat being pushed over by the force on the sails and the weight of the keel trying to stand it back up.

See this animation below of the balance of forces. CLICK on the green Increase Wind button. You will see how the “righting force” increases as the weighted keel lifts outwards off the centerline. You’ll also see how the tipping force decreases because less sail area is presented face-on to the wind. It means that the righting force from the keel will always overpower the wind force at some angle of heel. This is not to say that sailboats never tip over, they do but only usually in cases of a massive unprepared-for gust (60+ knots), giant wave, or if they lose their keel. Dinghies of course do tip over from the improper balance of the crew.

What is an acceptable heel angle?

The acceptable angle of heel on a sailboat depends on various factors, including the design of the boat, its ballast, the boat’s purpose, and the prevailing conditions. Generally, here are some guidelines:

• Dinghies and Small Boats : Dinghies are designed to be agile and may heel significantly, especially when sailed aggressively. Capsizes can happen but are often a part of dinghy sailing.
• Cruising Sailboats : Most cruising sailboats are designed to be stable and comfortable. They typically perform best at an angle of heel between 10° and 20°. Once a cruising boat heels beyond 20°, its weather helm tends to increase, making it more challenging to steer, and the boat might not sail as efficiently.
• Racing Sailboats : Racers might push their boats harder, and some racing designs can handle more heel. Nevertheless, excessive heel can still decrease speed as more wetted surface (hull in the water) causes increased drag.
• Multihulls (Catamarans and Trimarans) : These vessels are designed to sail relatively flat. Heeling angles over 10° can be a cause for concern on a multihull. When a multihull starts to heel significantly, there’s a risk of capsize, especially if a hull lifts entirely out of the water.
• Keel Design : Boats with full keels tend to be more stable and resist heeling more than those with fin keels or lifting keels. However, once they reach a certain heeling point, full keel boats can be more challenging to bring back upright.
• Seaworthiness : Some boats, especially bluewater cruisers, are designed to be very seaworthy and can handle significant heel angles, even beyond 45°, without capsizing. Still, this doesn’t mean it’s comfortable or efficient to sail them at such angles.

Factors like gusty winds, big waves, and the condition of your sails (e.g., having a full mainsail up in strong winds) can also influence heel.

What to do if you are getting excessive heeling angle:

• Reef Early : Reducing sail area can help to decrease heeling and make the boat easier to control.
• Adjust Sail Trim : Flatten your sails by tightening the outhaul, cunningham, and backstay (if adjustable).
• Change Your Point of Sail : Sailing more downwind can reduce heeling, but be cautious about accidental jibes.
• Ease the Sheets : Letting out the mainsheet or headsail sheet can reduce power in the sails.

Lastly, the best way to understand how much heel is acceptable for your specific boat is to gain experience in various conditions and, if possible, consult with more seasoned sailors or trainers familiar with your type of boat.

This information was drawn from the NauticEd Skipper Course (for large keelboats) and the NauticEd Skipper Small Keelboat Course . Sign up now to learn the knowledge you need to know to effectively skipper a sailboat.

My vision for NauticEd is to provide the highest quality sailing and boating education available - and deliver competence wherever sailors live and go.

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Heeling Explained

• Thread starter Don Guillette
• Start date Jul 29, 2012
• Featured Contributors
• Sail Trim with Don Guillette

Don Guillette

One of the sail trim forum listers, Robert Lang, sent me this info, which I thought mates would find interesting -- especially RichH and Joe from San Diego both of whom might be related to Robert (just kidding!!). What do you two guys think of his explanation?? Good day to you and thanks for all the tips you provide to us, including to me in particular in past e-mails. Now, I saw your post where you said "I don't know how heeling effects the speed of all boats but I do know the Catalina 30 and the Catalina 25 and those boats sails the fastest (for me) at about 20 to 25 degrees of heel." I can explain it and do so in a manner that you can see. I assume that you know that a symetric foil will create lift if the angle of attack is not directly and perfectly on its center line. You can show that by drawing a symetrical foil (plan view, not elevation), place a dot near but not on the centerline, and then measure the distance from the dot to the rearmost portion of the foil. One route will be longer than the other. Two particle parting at the point of the dot MUST come back together at the same time at the end of their trip. The longer side will have a greater flow and the greater flow will have less pressure, thus causing lift to that side. Now, ask, what has more force, air at ST&P at 1 MPH or water at 1 MPH? Water being denser has more mass and thus has more force at the same speed. So, given all other things equal, the same foil in water will create MORE lift than the same foil in air. Infact, the difference in lift is INCREDIBLE -- HUGE -- most notable. Becuae the difference in lift is so huge, where a small change in a foil's shape may create a rather insignificant change in lift, a small shange of the foils shape may create a significant change in the lift in water. Now, get some three by five cards and a cup of coffee or hot cocoa. Make yourself a nice foil shape out of a card. Keeping the top, create a foil. Keeping it level, dip it in the coffee. It will leave a stain where the level line is. Cut the foil apart from its centerline fron to centerline rear point. Measure the left and right lines. If it is symetric and level, the lines will be equal. Now, build a similar symetric foil from another card. Dip it into the coffee gain but this time, pretend that you are heeling 15 to 20 degrees. Now, cut apart the foil and measure the left and right lines. The lower line will be, relative to the upper line, shorter. Heeling the boat causes the symetric foil to become an asymtric foil and you need just a bit of change to have a lot of lift. Now, as you continue to heel, at some point you interrupt the flow over the keel. Intterupted flow provides NO lift. And it is as you start to pass 20 or 25 dgrees that you lose lift, and speed, and control. You actually stall the foil. That is why some heeling makes you faster while too much (see my avatar) hurts you even as it thrills the crew). ____________________________________________________________  

While heeling can increase the speed of some sailoat designs.... I would suggest that an increase in waterline length is the major reason...... not an increase in lift from the keel. The fin keel provides lift when the boat doesn't move exactly straight ahead (crabbing, if you will) changing the angle of attack due to side pressure from the sails... the benoulli effect seems plausible here... but... is it a result of heeling the boat????? well, uh, Don... you're article hasn't exactly convinced me after I did some quick research on the subject and couldn't find anything to support the premise. The consensus was that lift from the keel was a result of its angle of attack from the boat's slightly sideways motion through the water.... and that heeling changed a boat's hull from symetric at the waterline, to a more asymetric shape which would induce lift. Also, in an attempt to circumvent class restrictions, some sailboat's designs incorporated large overhanging bow and stern portions that extended waterline length, and thus potential top speed, when the vessel was heeling....Think 12 meter AC boats.  

Sam Salter said: The bit about 2 particles having to arrive at the trailing edge together isn't true! One particle is going to be long gone when the other gets there. There is no physical reason they have to arrive together. While the bit about the heeled keel sounds plausible (It's late at night and I'm having trouble seeing it in my mind) wouldn't that just give you lift to windward. I'm not seeing any force to give you extra speed? sam Click to expand

A never ending argument! But my 2 cents...doesn't the foil created by the sails also lose lift as you get closer and closer to the water, as you are not only trying to make the air flow take a longer path, thereby increasing speed but now you are compressing the air flow against the water? Think of a boat heeled at 88 degrees(theoretically). If you took a very thin piece of wood (think rectangle here) and measured the force it takes to move it thru the water at say speed X, if you "heeled" it 10 degrees I don't think the force needed to move it a speed X would be any different. The next time your boat is out of the water take a string and measure the difference from the normal waterline and a 20 degree heeled waterline, which I think would be longer. I agree with Joe, it's about boat shape. I also agree with weinie!!!!  

anchorclanker

In physics, as well as proven in the wind tunnel by the Wright Brothers, regarding an airfoil in laminar flow, or in our case a hydrofoil or sail, the flow striking the leading edge and separating to follow both sides of the foil WILL arrive at the trailing edge at the same time. It is because of this that true lift exists at all. On a symmetrical or non symmetrical foil, as the angle of attack changes, flow is altered because the leading edge has changed angle of incidence, forcing the fluid over the two surfaces to take longer and shorter tracks. The fluid taking the longer course over the foil creates a lower pressure than the fluid taking the shorter track, and that force acts to pull the foil in the direction of lower pressure. In fact it was the Wright Brothers we owe for discovering those properties, that allow us to fly, have efficient props, and teach us how sails really work. It is not the same as dragging a block of wood with squared off edges through the water or air. A foil will have laminar flow until it reaches the critical angle of attack where flow begins to separate away from the longer surface, eddies begin to form, drag climbs higher, and the foil stalls. It should also be pointed out that propellers work the same way. They dont push air or water like a fan, but rather pull via the properties of a proper foil. When a prop stalls, in water the pressure will drop so low on the face as to cause the water to boil, and then we have Cavitation, which should never be confused with Ventilation (air being drawn down into the prop from the surface) Cavitation can destroy a prop by eroding the face. I believe whats being pointed out in the OP, is that as the boat heels over, a greater angle of attack is taking place along the keel, as well as the rudder, in an attempt to keep the boat pointed. That greater angle of attack is creating greater drag, slowing the boat, while simultaneously the sails lifting force (vector) starts to point downwards rather than forwards. Therefore, as soon as the boat begins to lose forward velocity, the drag has exceeded the forward lifting force. Just as in an airplanes wing, the same four forces are in effect. Force over drag, lift over gravity.  

Scott T-Bird

Theories abound! ... But I have some simpler thoughts. First of all, hull speed is related to the length of the wave that is created. It's a chord length between waves (the longer the wave length, the greater speed potential of the boat). Any increase in speed due to increasing the length between waves is a result of the boat squatting in the water either when heeled or even squatting when reaching or running. It is the squatting that increases the CHORD of the waterline length, not the heeling. I don't think it is related to the increased length due to curvature of the hull. If that were the case, then all beamy boats would be inherently faster, but they aren't (necessarily). I assume we are talking strictly about boat speed and not VMG, because VMG is a separate discussion where the hull shape and heeling probably does have a beneficial effect. I'll get into that later. I was reminded last week (when I was struggling to find a spot on the lake that had some wind), that my boat is faster when reaching. I happened to be on a reach when I finally found a slot that gave me some consistent wind and my boat leaped into a speed that was significantly higher than I can achieve when beating into the wind. With balance and sail trim in good form, I had at most 10 to 15 degrees heel with apparent wind at about 12 knots a little bit aft of beam. At this point of sail, the boat isn't heeling but it is squatting and the sails are standing nice and tall to take full advantage of the wind. Of course I had a full main and a 150 genny pulling with all it had. At this point, I could safely say that my boat was performing at hull speed and probably a little more. If I had turned around to beat into the wind, apparent wind would have been in the neighborhood of 20 and I would have had more than I want to handle with a full main and 150 genny. I would have trimmed sails to try to maintain heel between 20 to 25 degrees and would probably have been making way at half a knot slower in boat speed compared to my reach. If I had trimmed sails for more power (raised the traveller car) I would probably heel excessively (25+) and with frequent round-ups, the boat speed would slow down significantly. IF I was able to reduce sail to the perfect sail plan where I was able to maximize power and maintain the optimum heel for a balanced helm I doubt that I could achieve the same boat speed that I had on a reach. This is where I agree with people who say that flatter is faster. But it is really just a function of maximizing power from the wind at an angle of heel that is managable. It seems obvious to me that the greater power from the wind you can harness (that includes trimming to allow your boat to sail on her feet), the more speed you will achieve until limiting factors such as displacement hull speed, and losing control of the helm with excessive heel, either limit your speed or slow you down. When you are beating into the wind with perfect sail trim, but the boat is heeled only 15 degrees, you are not reaching your potential speed for the simple reason that there isn't enough wind to power your sail plan. It seems obvious to me that with more wind, you would harness more speed and heel more. It has very little to do with increasing your water line length or anything hull-shape related. I agree that hull shape does affect lift, which helps improve VMG to windward. The curvature of the hull shape does cause a boat to climb to windward when heeled to leeward. Windsurfers know that when sailing a board at slow speed (in displacement mode), pressuring the leeward rail makes the board point. The curvature of the board, or the rocker, is the reason for this. A sailboat behaves similarly.  

Re: Theories abound! ... Airplane wing, curve on top. Sailboat wing, curve on bottom more or less. Boat slipping sideways tripping over keel makes mast lean over. It works fine for my understanding level, all I gotta do is make the telltales fly. All U Get  

anchorclanker said: In physics, as well as proven in the wind tunnel by the Wright Brothers, regarding an airfoil in laminar flow, or in our case a hydrofoil or sail, the flow striking the leading edge and separating to follow both sides of the foil WILL arrive at the trailing edge at the same time. Click to expand

simple answer I am assuming that if the boat is not healing to the point where part of the keel is out of the water (much more than 20 degrees) than there is no effect of air foil on the keel. The dominant effect would be the righting moment caused by the sails being more and more off the vertical centerline of the boat. As the center of effort of the sails move away from the vertical centre of effort in the keel, this creats a turning moment to turn the boat to windward. This is what causes weather helm in a boat that is otherwise balanced in its sailplan when the boat is not healing. The more healing there is, the more the rudder has to dig into the water to keep the boat on course and this creats drag in the water. Heal is inevitable as the sail catches the wind but too much heal means too much drag from the rudder. Therefore, it is possible that in heavier winds, a reefed sail can actually give the same or even higher boat speed with less heel. Would this simple answer make more sense than the air foil? Oliver....  

Ross, do you attribute the lifting of a wing (airplane, keel, rudder, sail) to Newton's third law of motion over the more common explanation of the bernoulli effect?  

Oliverhg said: I am assuming that if the boat is not healing to the point where part of the keel is out of the water (much more than 20 degrees) than there is no effect of air foil on the keel. The dominant effect would be the righting moment caused by the sails being more and more off the vertical centerline of the boat. As the center of effort of the sails move away from the vertical centre of effort in the keel, this creats a turning moment to turn the boat to windward. This is what causes weather helm in a boat that is otherwise balanced in its sailplan when the boat is not healing. The more healing there is, the more the rudder has to dig into the water to keep the boat on course and this creats drag in the water. Heal is inevitable as the sail catches the wind but too much heal means too much drag from the rudder. Therefore, it is possible that in heavier winds, a reefed sail can actually give the same or even higher boat speed with less heel. Would this simple answer make more sense than the air foil? Oliver.... Click to expand

Stu Jackson

Ross S said: If this were the case then ask yourself how any plane can fly upside down? In fact, this has nothing to do with how a plane flies at all. Click to expand

Stu Jackson said: Heal - to feel better Heel - the back of your shoe or boat tilt Click to expand

Well, we heard from Joe from San Diego. Now we need RichH to chime in. This discussion is way to deep for a common seaman like me. All I was repeating about the keel and rudder was what Buddy Melges told me in a San Diego bar about 100 years ago.  

Oliverhg said: I am assuming that if the boat is not healing to the point where part of the keel is out of the water (much more than 20 degrees) than there is no effect of air foil on the keel. The more healing there is, the more the rudder has to dig into the water to keep the boat on course and this creats drag in the water. Would this simple answer make more sense than the air foil? Oliver.... Click to expand

LaColla said: Ross, do you attribute the lifting of a wing (airplane, keel, rudder, sail) to Newton's third law of motion over the more common explanation of the bernoulli effect? Click to expand

Ross, thanks for your remarkably understandable explanation. As interesting as the physics are, I think it is equally interesting that there is uncertainty in the explanation of exactly how a foil works, especially given how much they are used in aviation, sailing, wind generators, ect. For instance, those that I have read that use Newton to explain lift use you first example as evidence for it- that you in fact don't need a curved surface of a wing to generate link-think of the balsa wood airplanes with the flat wings by way of example. Anyway, I find the topic fascinating and I'm really amazed to see that not everyone agrees on exactly how a wing works.  

LaColla said: Ross, thanks for your remarkably understandable explanation. As interesting as the physics are, I think it is equally interesting that there is uncertainty in the explanation of exactly how a foil works, especially given how much they are used in aviation, sailing, wind generators, ect. For instance, those that I have read that use Newton to explain lift use you first example as evidence for it- that you in fact don't need a curved surface of a wing to generate link-think of the balsa wood airplanes with the flat wings by way of example. Anyway, I find the topic fascinating and I'm really amazed to see that not everyone agrees on exactly how a wing works. Click to expand

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• Righting Moment

The Righting Moment & Sailboat Stability

Feeling a sailboat heel under him for the first time, a novice sailor may wonder what stops it from going all the way over. The righting moment is,  of course, t he reason why it doesn't .

Many years ago my son James asked me just that.

"It's that lump of lead in the keel" I explained.

"Why put lead in something you expect to float?" said James.

Hmm, perhaps he was onto something - I put him down as a future multihull man...

This piece of nostalgia hints at the two key ingredients to stability - ballast and hull form.

Monohulls have more of the first and less of the second, and multihulls very little of the first and much of the second.

And stability considerations fall under two further headings - static and dynamic. Static being when the boat is at rest; dynamic when underway and subject to the forces of wind and waves.

Righting Moment & Static Stability

Take a look at the sketches below:~

With the boat upright, the Centre of Gravity (G) is in line with the Centre of Buoyancy (B); effectively there is no righting moment.

But as the boat heels, a righting moment develops. The Moment Arm (Z) is the horizontal distance between G and B, and the Righting Moment Gz is the product of the moment arm and the boat's displacement.

But whilst the boat's displacement and the location of its Centre of Gravity remain constant, Z changes as the boat heals more and more. There comes a point at which Z reaches a maximum value, normally at an angle of heel of around 60 degrees or so. As the boat heels past this point it decreases, leading eventually to a capsize.

The relationship between heeling angle and righting moment is different for all boats, and the plotted Gz curve gives an excellent indicator of the boat's static stability.

But the boat's static stability and its righting moment is only part of the story. How will it react to a sudden gust of wind or when clobbered by a large wave?

Dynamic Stability

There's no arguing that heavy displacement helps a boat's stability, but the most important factor affecting dynamic stability is its moment of inertia. This is the measure of the boat's resistance to angular acceleration.

Boats rotate around three axes - rolling around the fore and aft axis; pitching about the transverse axis; yawing around the vertical axis.

It's the Roll Moment of Inertia (RMoI) that should concern us most as it's around the fore and aft axis that a boat is most likely to capsize.

This is calculated by multiplying the weight of all the boat's constituent parts by the square of the distance from the boat's Center of Gravity to the part's Center of Gravity - a tedious but necessary task for the designer. The squared term means that the distance of heavy items from the Center of Gravity greatly affect the RMoI, and the greater RMoI the less the boat will react to a gust of wind, or a large wave.

So boats with their ballast deep in their keels, their fuel and water tanks as far outboard as possible, and long heavy masts will have greater RMoI's and will be more dynamically stable as a result. Such boats will have long roll periods and will be highly resistant to rapid changes in heel angle.

This will be very apparent to a crew unfortunate enough to have lost their rig, as this item is the boat's greatest contributor to the moment of inertia. Without it, the boat's roll period will be very quick and snappy, and the probability of capsize much higher.

Makers of grandfather clocks had cause to be grateful for the effects of the rotational moment of inertia. They used it to govern the rate of gain, or loss, of their creations.

To correct a 'slow' clock, the pendulum would be shortened slightly thereby reducing the distance to the neutral axis. This decreased the period of oscillation - it would swing faster - and speed up the clock's mechanism. Conversely, for a clock that gained, the pendulum would be increased in length to create the opposite effect.

The principal reason for using pendulums in clocks was that for a given length, the period of oscillation remains constant, irrespective of the amplitude.

Artwork by Andrew Simpson

And so it is with a boat; if she's rolling gently at anchor, or from gunwale to gunwale in a seaway, the roll period will be the same.

So clearly there's a lot more to a sailboat's stability than the Righting Moment alone.

Righting Moment & Stability: A Few FAQs...

What are some factors that affect the righting moment curve?

The righting moment curve is a graph that shows how the righting moment changes with different angles of heel. Some factors that affect this curve are:

• The displacement and distribution of weight of the boat, which determine the location and movement of the CG.
• The hull shape and volume of the boat, which determine the location and movement of the CB.
• The freeboard and deck shape of the boat, which affect when and how much water enters or leaves the boat as it heels, changing its buoyancy.
• The rigging and sail plan of the boat, which affect how much wind force and drag are applied to the boat at different angles of heel.

What are some advantages and disadvantages of having a high righting moment in a sailboat?

Some advantages of having a high righting moment are:

• The boat can carry more sail area and generate more speed and power in moderate winds.
• The boat can resist capsizing better in strong winds or waves.
• The boat can have a more comfortable motion and less fatigue for the crew in rough seas.

Some disadvantages of having a high righting moment are:

• The boat may have more wetted surface area and drag, reducing its speed and efficiency in light winds.
• The boat may have more weight and inertia, making it less responsive and manoeuvrable.
• The boat may have more cost and complexity in its design and construction.

What is the difference between righting moment and heeling moment?

The difference between righting moment and heeling moment is that they have opposite effects on the stability of a sailboat. Righting moment is the force that tries to restore the boat to its upright position, while heeling moment is the force that tries to tilt the boat away from its upright position.

The righting moment is determined by the distance between the centre of gravity (CG) and the centre of buoyancy (CB) of the boat, which changes as the boat heels.

The heeling moment is determined by the wind pressure on the sails and the water pressure on the hull, which also change as the boat heels.

A sailboat is stable when the righting moment is equal to or greater than the heeling moment, and unstable when the heeling moment is greater than the righting moment.

A sailboat can increase its righting moment by adding ballast, increasing beam, or reducing sail area, and can reduce its heeling moment by reefing, easing sheets, or changing course.

How does the wind speed affect the righting moment?

The wind speed affects the righting moment by changing the heeling moment, which is the force that tries to tilt the boat away from its upright position. The heeling moment is determined by the wind pressure on the sails and the water pressure on the hull, which also change as the boat heels.

The higher the wind speed, the higher the wind pressure on the sails, and the higher the heeling moment. This means that the boat will heel more for a given sail area and angle of attack. To counteract this, the boat needs to have a higher righting moment, which can be achieved by adding ballast, increasing beam, or reducing sail area.

The ideal wind speed for sailing depends on the type and size of the boat, the skill and preference of the sailor, and the weather and sea conditions. Generally, most sailors prefer a moderate wind speed of 5-12 knots, which allows them to sail comfortably and safely without excessive heeling or capsizing. However, some sailors may enjoy sailing in stronger winds of 15-25 knots, which can provide more speed and power, but also more challenge and risk.

How does the hull shape affect the righting moment?

he hull shape affects the righting moment by changing the position and movement of the centre of buoyancy (B) as the boat heels. The centre of buoyancy is the centroid of the boat's underwater volume, and the force of buoyancy acts upward through this point. The righting moment is the force that resists the heeling of the boat caused by the wind pressure on the sails. It is determined by the distance between the centre of gravity (G) and the centre of buoyancy (B) of the boat, which changes as the boat heels. Different hull shapes have different effects on the righting moment. Some examples are:

• A wide and shallow hull has more form stability, which means that it has a larger displacement of the centre of buoyancy to leeward as it heels. This increases the righting moment and makes the boat more stable, but also more prone to drag and less responsive.
• A narrow and deep hull has less form stability, which means that it has a smaller displacement of the centre of buoyancy to leeward as it heels. This decreases the righting moment and makes the boat less stable, but also more efficient and manoeuvrable.
• A round-bottomed hull has a low metacentric height, which means that it has a small distance between the centre of gravity and the metacentre (the point where a vertical line through the heeled centre of buoyancy intersects the ship's centreline). This makes the boat slow to roll and easy to overturn, but also more comfortable in rough seas.
• A flat-bottomed hull has a high metacentric height, which means that it has a large distance between the centre of gravity and the metacentre. This makes the boat quick to roll and hard to overturn, but also more uncomfortable in rough seas.

The above answers were drafted by sailboat-cruising.com using GPT-4 (OpenAI’s large-scale language-generation model) as a research assistant to develop source material; to the best of our knowledge,  we believe them to be accurate.

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How Heel Affects Speed and Handling

• By Steve Killing And Doug Hunter
• Updated: September 27, 2017

The underwater hull shape of your boat when it heels affects how much sailing length is put to work, how easy it is to steer, and how much horsepower it can carry aloft as the breeze increases. Consequently, some hull shapes must be sailed differently to get the best performance. To explain this concept, let’s compare three of my designs that represent common, but very different, hull shapes: a beamy IOR 40 called Chariot , the long and narrow Canadian 12-Meter True North I with pronounced overhangs, and a 50-foot deep-draft sportboat design, the Daniells 50.

Effective waterline length

A general design rule is that the longer the waterline, the higher the hull’s speed potential. Perhaps the most important change when a boat is heeled is the length of the hull in the water, which is also known as effective waterline length or sailing length. Before the advent of rating rules based on computer performance prediction, designers working with point-measurement rules naturally strove to create hulls with more effective waterline length when heeled than what was measured for ratings purposes when the boat was upright.

The 12-Meter typified this design strategy. The simplest response to outwitting the waterline measurement process was a boat with generous overhangs at the bow and stern, which would stretch the sailing length when the boat heeled. The International Rule, created in 1906, sought to control excessive overhang by measuring a 12-Meter’s sailing length 7 inches above the load waterline (LWL). But there was just too much speed potential in overhangs for designers not to stretch the bow and stern above this point. When these long, narrow, and heavy designs heel to 25 degrees as shown, the deepest part of the hull remains along the centerline near amidships, but locations closer to the bow and stern shift their immersed volume to one side. When this happens, a significant gain in sailing length is achieved, especially at the stern, and a heeled modern 12 develops a particularly noticeable shift in underwater shape outboard of, and behind, the rudder.

It’s a profoundly different shape than that of the sportboat, which was designed without any point-measurement rule to satisfy. This hull is typical of modern sportboat designs, which are either handicapped through computer performance prediction such as the IMS or race in one-design fleets. A clean underwater shape essentially shifts to leeward as the boat heels. Some gain in waterline length results, but not in the dramatic way of a Meter-class boat. It’s not as important, the way it is with designs with pronounced overhangs, to get the sportboat to lay over just to increase hull speed.

Which brings us to Chariot and the issue of how heeling affects a boat’s performance beyond waterline length. Like the 12-Meter, the IOR design is based on a point measurement system. The International Offshore Rule, which was created in 1972, dominated offshore racing design in the 1970s and 1980s. While IOR competition has been superseded by the IMS and one-design offshore classes, the rule lives on in the hulls of many club-based racing keelboats built in an era when racer/cruiser designs routinely took their cue from SORC and Admiral’s Cup winners.

While Chariot isn’t the most extreme product of the IOR, it does show many typical IOR features: a somewhat triangular transom, deep forefoot, large skeg, and a fair amount of beam–emphasized by a designer because the rule assumed that fatter is slower than skinnier. As an IOR design heels, there’s a tendency to pick up sailing length. But because there’s so much volume gathered amidships, if it heels too far, it can begin to rise up, actually shortening the sailing length. As a result, this hull is far less tolerant of heel angle than less beamy designs.

Asymmetry, drag, and control problems

The narrower hull forms of the 12-Meter and the Daniells 50 also encounter far less form drag. This is the kind of parasitic drag an object experiences as it’s being pushed through a fluid, and the narrower a hull is relative to its length, the lower the form drag will be. Because of this, meter-boat hulls can drive comfortably to windward at high degrees of heel with minimum form drag, stretching their sailing length in the process. It’s an advantage enjoyed by other long, narrow hull forms such as Dragons, IODs, and Etchells.

This brings us to another potential consequence of heel. Look at the shapes of the waterline planes in the heeled drawings. (It’s important to consider all the waterline planes, and not just the lightest colored one describing the sailing length.) With Chariot , they’re asymmetric, with long curves on the leeward side and near-straight lines to windward. The heeled 12-Meter displays a less extreme amount of asymmetry, while there’s hardly any with the Daniells 50. Asymmetry encourages the boat to turn to windward, which can lead to control problems. Those problems are compounded by the way a boat settles fore and aft as it rolls to one side.

In most cases, heeled hulls have more volume (read buoyancy) at the stern than the bow, which means that, to different degrees, they want to pitch bow down as they lean over. Even a boat as long and heavy as a 12-Meter benefits from moving crew weight aft as it heels, to counteract the tendency. The effect is most pronounced in Chariot , where it also has the most serious consequences because of things going on at either end of the waterline. IOR boats typically have a deep forefoot with a sharp bow knuckle, and if the bow gets a bite on the passing water as the stern lifts when reaching, a broach is in the making. The control problem is exacerbated by the rudder’s position. As with the 12-Meter, the rudder post is positioned at the end of the design waterline, and as the hull heels, more so in the case of the IOR design, the top of the rudder is in danger of becoming airborne if the stern is allowed to rise. It’s now vulnerable to ventilation down its low-pressure side, reducing efficiency and encouraging a total stall, just when the bow knuckle is digging in, and the heeled hull’s asymmetry is encouraging a sharp turn to windward.

The control problem is less of an issue with the 12-Meter, which lacks the sharp bow knuckle and generally has enough displacement to keep the rudder buried. And it’s least likely to crop up with a modern sportboat, whose shape is noticeably less beamy than that of Chariot , with a wider transom, flatter sections aft, no skeg, and a shallow forefoot. The rudder is positioned well forward of the design waterline’s aft end, and even when the hull is heeled 25 degrees, it’s at minimum risk of inducing ventilation. All that beam aft creates more waterline length when heeled, but at the same time the underwater shape remains symmetrical, which helps maintain a comfortable amount of weather helm. As with the other designs, moving crew weight aft when heeled is a good idea.

Target speed and heel angle

In 20 knots of true wind, our three designs have distinctive optimum performance parameters. Chariot has a target speed of 6.7 knots, but as the beamiest design, to get there the heel angle must be limited to 26 degrees, and sails must be reefed to 80 percent and flattened. The Daniells 50 will make 7.9 knots with the same sail management strategy, but its hull form permits a heel angle of 29 degrees. The 12-Meter True North I , the narrowest and heaviest of the lot, requires no reefing, only flattening of the sails, and can carry 30 degrees of heel as 8.3 knots are achieved.

How much heel your boat can actually tolerate can be investigated by some on-water pacing against an identical or similar design. If you don’t have one already, install a heel gauge and pay attention to it as you draw your observations. An excellent resource to gather hard numbers on how your boat should be handled is US SAILING, which offers valuable performance packages on about 1,500 designs.

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Have you noticed how some sailors stretch out ahead upwind, while others fall back?

Part of making good progress upwind is keeping the boat to an optimal angle of heel. Too little and you give up power, too much and you might feel fast, but are losing height.

The Merit 25 is wide at the waterline, but has little flare from the waterline to the sheerline. If the boat is heeled too far, the buoyancy concentrated close to the waterline lifts the keel and rudder to the surface very easily.

Take a look at the shot below and note the white water exiting from just astern of the keel. This is indicative of an abrupt and uncontrolled release of pressure from behind the keel, showing that at this, excessive heel angle the boat is unable to convert the drive from the sails to forward motion.

So what does that look like from astern? Here we can clearly see that the underside of the boat on the windward side is entirely out of the water.     Note also the pressure wave that flowing from the rudder, indicating that the boat is sliding sideways and making leeway rather than driving to windward.

In their defense, this boat is lightly crewed and is cruising, they’re dealing with gusts by feathering up into the wind rather than actively trimming.   Note also the loose mainsail luff and very full sails.  Neither is conducive to upwind performance.

So what should you be aiming for? A good heel angle for the Merit 25 is 15° – 20°, less than you would heel a J/24. 

When you find your heel angle exceeding this, move crew weight to windward, flatten the sails and keep the main sheet out of the cleat so your trimmer can ease in  the puffs and sheet back in during the lulls.

In gusty conditions, the benefits from active mainsheet trimming typically exceed the benefits of the extra crew member on the rail.    

The bonus of having another crew member in the cockpit is that they can watch the compass while teh skipper concentrates on driving and can glance regularly under the jib for boats and obstacles.

Better Sailing

Why Do Sailboats Lean?

Imagine a calm ocean scene where a sailboat tilts gracefully to one side, its sails billowing with power and grace. This iconic pose isn’t just for show; it’s a fundamental aspect of sailing. Sailboat leaning, a phenomenon often referred to as “heeling,” is a defining characteristic of the sailing experience. The sight of a sailboat gracefully tilting to one side, its sails billowing, is iconic and poetic. But Why Do Sailboats Lean? The answer lies in the intricate interplay between the forces of nature and the design of the sailboat. Let’s delve deeper.

Balancing Forces

At the heart of heeling lies the delicate interplay of multiple forces. Two key players dominate this intricate dance: the wind pushing against the sails and the counteracting forces provided by the sailboat itself, especially its keel.

Wind’s Dual Role

Wind is the primary mover of sailboats. However, it doesn’t merely propel the boat forward. Depending on the boat’s direction relative to the wind, the sails capture and redirect wind energy. This creates both a forward driving force and a sideways push. This sideways component is what first prompts the boat to lean over.

The Keel’s Counteraction

Beneath the waterline of most sailboats is a structure called a keel. The keel is typically heavy, extending deep into the water. As the wind tries to tilt the boat sideways, the keel acts as a counterbalance. It utilizes its weight and the buoyant force from the water it displaces to resist the tipping motion. This results in the boat leaning rather than capsizing.

Also Read: Can Sailboats Tip Over?

The Advantage of the Lean

Though heeling might seem like a challenge to sailing, moderate heeling is often beneficial. When a sailboat leans, the shape of its submerged hull changes. For many boats, this heeled shape cuts through water with reduced resistance, potentially increasing speed. Additionally, the tilted sails might interact with the wind more effectively than when upright, further enhancing propulsion.

Sail Design and Lift

Sail design plays a pivotal role in the leaning dynamic. When wind flows across the curved surface of a sail, it behaves similarly to air flowing over an airplane wing, generating lift. While this lift propels the boat forward, it also exacerbates the heeling force due to the upward motion being translated into a sideways one, depending on the boat’s angle to the wind.

Role of the Sailor

While nature offers the forces, sailors have the reins. Sailors adjust the sails’ trim, change course, or even reef the sails (reducing their surface area) to manage the degree of heeling. Techniques and strategies vary depending on wind strength and the desired direction. For instance, in high winds, a sailor might let out the sails slightly, allowing some wind to spill out, reducing heeling forces. Sailors thus continually negotiate with the wind to balance speed and stability.

Beyond the Tipping Point

All leaning isn’t good. Excessive heeling can be detrimental to the boat’s performance and can also pose safety risks. If a boat tilts too far, it can capsize, turning over completely. Sailboats are designed with heeling thresholds in mind. The boat’s hull shape, the weight and depth of its keel, and sail configuration all contribute to its resilience against excessive heeling. Modern sailboats, especially those designed for racing, may heel dramatically but also have features that prevent full capsizing in most situations.

A Timeless Ballet

To the external observer, sailing can appear as a serene dance across the water. But onboard, there’s a dynamic interaction of wind, water, physics, and skill. The leaning of a sailboat isn’t a random event but a testament to the balancing act sailors have honed over millennia.

Also Read: Is Sailing Hard?

Why Do Sailboats Lean? – Conclusion

In essence, the leaning of sailboats, or heeling, is a dance between the boat and nature. It’s a balance of forces, an art of physics, and a testament to human engineering and skill. Far from being a mere side effect of sailing, it’s integral to the sport and craft. As one delves deeper into the world of sailing, understanding why sailboats lean becomes the gateway to appreciating the nuanced interplay that makes sailing the timeless pursuit it is.

Peter is the editor of Better Sailing. He has sailed for countless hours and has maintained his own boats and sailboats for years. After years of trial and error, he decided to start this website to share the knowledge.

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