sailboats in the wind

How Do Sailboats Sail into the Wind?

It seems intuitive that sailboats, powered only by the wind, can travel easily with the wind at their backs, but it may seem impossible that they turn around and come home again, with the wind blowing straight against them.

But this reverse movement is possible because a moving boat's sail is shaped as an airfoil like the wing of a plane. When air moves over a plane's wing, from front to back, wind flowing over the top of the wing has to travel farther than wind flowing under the wing's bottom surface. This creates a pressure difference that lifts the plane.

On a sailboat, wind blowing against the boat at an angle inflates the sail, and it forms a similar foil shape, creating a difference in pressure that pushes the sail perpendicular to the wind direction.

According to "The Physics of Sailing Explained" (Sheridan House Inc, 2003), by Kent State University physics professor Bryon D. Anderson, this force from the sail's foil shape is combined with and balanced by other forces, including those of the boat's keel (the long thin piece that juts down from the bottom of the boat).

Together, the forces of drag, from the water, and the pressure from the wind against the sail itself push the craft forward. It moves at an angle opposite the direction of the wind, called windward in sailing terminology.

According to the American Institute of Physics' Physics Today magazine, the keel is especially important because without its balancing action, a boat would simply drift downwind.

Windward sailing also does not work if a boat is pointed directly opposite the wind direction, according to The Physics of Sailing. Wind has to be moving against the boat at an angle of at least 40 degrees for most vessels. Angling too sharply into the wind causes the forces on the boat to become unbalanced, and moves the boat sideways in the water.

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A sailor intending to travel windward toward a point exactly in line with the direction of the wind will have to zig zag back and forth to reach its target. Using this "tacking" technique, and traveling at an angle as close to the wind's direction as possible, sailors can reach a point in any direction, regardless of the direction of wind.

Got a question? Email it to Life's Little Mysteries and we'll try to answer it. Due to the volume of questions, we unfortunately can't reply individually, but we will publish answers to the most intriguing questions, so check back soon.

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How To Sail Into the Wind (in 7 Simple Steps)

Sailing into the wind seems like Poseidon's magic, but once you learn how to set up your sails and hold the correct course, you can do it. This article explains the technique in 7 simple steps.

How to sail into the wind?

• Make sure your sails are close-hauled and tight
• Set your direction approximately 22 degrees from the direction of the apparent wind
• If you sail left from the direction of the apparent wind, your front sail should be on the left side and vice versa
• Your mainsail should be centered
• You can not sail directly into the wind, as there is an approximately 44 degree 'no go' zone' - 22 degrees from each side of the wind direction
• Because of that, if your destination is directly into the wind, zig-zag (tack) your way towards it, going 22 degrees left and then 22 degrees right
• During this zig-zag maneuver, you need to simultaneously change the boat's course and switch the front sail from one side to another

If you’re unsure what it all means, don’t worry. I will explain all the technical terms in the steps below.

It really isn't all that difficult once you remember these few steps. Plus it is a fun way to sail: the boat leans elegantly, the wind blows against you and you feel like the king of the seas.

So let's go through the steps in a bit more detail and make sure that next time you are out sailing, you can go wherever you set your mind to. Because that's what sailing is about - the freedom to do whatever you want.

On this page:

Make sure your sails are tight, determining the right course, headsail position should be dead center, center your mainsail, avoid the no-go zone, zig zag (tack) to stay on course, how to tack to change direction.

When I was on a sailboat for the first time and the skipper said ‘we’ll now sail against the wind’, I thought he’d gone crazy. It’s a sailboat. It uses the wind to move. Things don’t go against the wind. They go with it. Look at the leaves on the ground when it gets windy.

But soon I was proven wrong. Because when sailing into the wind, your sail doesn't work like a sheet that is simply pushed by the wind. Rather, it works like an airplane wing. That is why sails of boats going against the wind have approximately the shape of a wing - and that's what step 1 is all about - making sure the sails are tight and hold their form. No flapping around, no loose ropes.

The sails should also be close-hauled. Close-hauled means they are pointing almost straight back. Their direction is mostly determined by how you set them, not by the wind.

I have a confession to make - you can't sail directly into the wind. That's just physically impossible. At least until somebody comes up with some new revolutionary sail system.

But here is the good news - you can have the next best thing - sailing almost into the wind. Precisely 22 degrees left or right from the direction of the apparent wind. Once you cross this imaginary line and steer your boat closer into the direction of the wind, your sails will start to flap around, lose their form and your boat will slow down.

Plus the boat will start shaking as the sails flap, it will all get noisy, simply put, you want to stick to those 22 degrees.

Don't worry, you don't have to bring a pen and paper to the helm and measure everything. The little V on the top of your mast along with the arrow that points into the wind, that's your best friend in determining the right direction. The angle of the V is precisely these 22 degrees times two.

So if the tail of the moving arrow overlaps one of the legs of the V, you are hitting the sweet spot.

If the tail is inside of the V, you are headed too much into the wind.

If the tail is too much outside of the V, you are still moving, but you aren't sailing as much into the wind as your boat allows.

The correct position of your mainsail is pretty clear. Have it tightly set right in the middle.

But what about your headsail? Your headsail is your front sail. This is mostly a jib. Even if it is as close-hauled as possible, you still have two places to put it - the left side and the right one. So what to do?

Well, the answer is pretty easy. If your sailing direction is left of the wind direction, you put the sail on the left. If you are sailing on the right side of the wind direction, you put the sail on the right.

Not much else to explain here. The tricky part comes when you need to switch sides. But more on that later.

As mentioned, the mainsail should rest in the middle. While sailing upwind, you don't need to manipulate it at all. That is unless you need to reef it during a storm. The important thing is to have it firmly set in one place. No wiggle room like would be the case if the wind was in your back. Remember, you are not being pushed, you are using your sails like wings.

All that needs to be said was covered in the second step. As already said, you can't go directly into the wind and some 22 degrees from its left or right side.

By the way, this number 22 is not exactly set in stone. It differs slightly for different boats. Racers can go more into the wind whereas cruisers have to keep the angle wider.

But you can find out what your boat's angle is quite easily. Close haul your sails, make them tight and start turning into the wind. As long as they hold the wing-shaped form, all is well. As soon as they start to flap, your angle became too narrow. You've entered the no go zone.

So right before the flapping starts, that's the sweet spot.

Obviously we have to address the important question here. What if your destination lies somewhere in the no go zone? Let's say the marina you want to rest at for the night is exactly where the wind is coming from. Dead center.

Well, since 22 degrees is the closest we can get to the wind direction, that's what we will do. Head left of your destination, sail for a bit, then turn and head right of your destination. Then left again, then right again. Dance around the center line and eventually you will get to your spot. If it sounds a bit abstract, see the picture below. This is called tacking.

How often you turn is entirely up to you. Whether you decide to turn just once (the red line), making your passage wide but with less effort, or whether you turn every two minutes, making the passage narrow (the blue line), won't influence the total distance covered.

As portrayed in the picture, going all the way to the right corner, turning and going straight towards the finish, or turning every time you reach the end of a single field has no effect on how far your boat will have to go in total. You pass the same amount of chess fields.

But know that each turn slows your boat down a bit and it takes time before it gathers speed again. So as far as time and energy goes, better keep it simple.

This means that the route you take will mostly be dictated by how wide you can afford your passage to be. If you find yourself in a narrow channel, you will have to switch directions often, if on the other hand you have nothing but open seas ahead, you are in luck.

When planning your zig-zag route, keep in mind that the wind will make you drift. Your boat will not travel in a straight line ahead, it will be pushed by the wind wherever it will blow from. Even though you are travelling upwind, since you are going 22 degrees off the wind's course, the wind is still pushing you from one side.

This zig-zagging means you will have to change directions. Especially for beginners, this is a potentially challenging maneuver and oftentimes has to be done with at least two people.

The reason it is a bit tricky is that you have to change the boat's course and switch the front sail from one side to another simultaneously within the shortest time you can. Why the rush? You don't want to hesitate because, during the turn, the boat goes through the 'no go zone', the dead angle where it won't be propelled by the wind. You will rapidly start losing speed. So you want to make sure you are on the right course as soon as you can.

Also, in this dead angle, the sails will flap and you don't want to expose them to this much, especially if the winds are too rough.

The best way to go about this is to have one person at the helm and two more at winches. Once the helmsman starts changing the course, the winch holding the front sail on one side should be released and the front sail should be winched in onto the other side. There will be a lot of sail flapping, especially if it is windy, but don't worry and just keep winching the sail in until it is nice and tight again.

A Leaning Boat

Don't worry, no more steps. Just a quick heads up. If you travel upwind, your boat will lean to one side. The windier it is the more it will lean. This is completely normal. Don't correct the course just because the boat's belly starts peeking out of the waves. The wind itself can't tip the boat over. I won't go into the physics of why that is, just know you are safe.

But be sure to have all your cabinets closed and keep the number of things that can freely move around to a minimum. Many teacups have been broken like this. It is also nice to inform those onboard that the boat will lean, especially if they don't expect it.

Feel like a Poseidon

It is precisely the boat leaned to one side, oftentimes so much that you can touch the water while standing behind the helm, and the feeling of speed, that makes this type of sailing so fantastic. As both the wind and the waves will be coming towards you, the boat's speed will feel much higher than it is. This makes sailing exciting as you feel like you are flying through the waves.

As opposed to downwind sailing where you hardly feel any wind, since you are traveling with it.

Lift Explained (Ok, but how is all this possible?)

Right. I still haven't explained that. Well, as said in the beginning, you aren't being pushed by the wind, you are, as it were, being sucked into it. I know intuitively this makes little sense but if you bear with me through this little physics lesson, you'll understand it.

As mentioned, a tight sail on a boat going upwind has approximately the shape of an airplane wing. See the picture for illustration.

Because of this shape, the wind on the shorter side has to travel slightly slower speed than wind on the other side. This results in high pressure on one side and low pressure on the other. And as with anything, where there is low wind pressure, things are being sucked in. That's why the tight close-hauled sail is so important.

The reason why your boat doesn't just go sideways is your keel. It compensates for the suction by pushing the boat and the powers combined result in the boat going more or less forwards.

So there you go. The whole thing really is not that complicated. As with everything, go out there and practice a bit. The main things to get a feel for are keeping the correct angle so that you take advantage of the wind as much as possible and mastering the direction change. It is easier to practice in slower winds before you give it a full go.

Related questions

How to sail downwind? If the wind is in your back, you just open up the sails as much as you can and let yourself be pushed. Sometimes a spinnaker is used, which is a special balloon-like sail used in back winds. Sailing downwind is easier for many sailors as the whole thing is a bit more intuitive. So it is easier to set up the sails correctly.

How was this done in the olden days? The Chinese were able to sail upwind very early on. Some medieval European designs on the other hands were only able to take advantage of downwind. This then really depends on the particular designs. Just as with any technology, some cultures got the hang of it sooner than the others. One thing is for certain though, the ability to sail upwind is not a modern matter.

So take advantage of the ancient wisdom, get out there and enjoy!

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You may also like, how much do sailing lessons cost.

If you're new to sailing and want to learn the old-fashioned way, you need to take sailing lessons. But are they as expensive as people say? And what's a good deal?

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Better Sailing

How Does Sailing Work? The Physics of Sailing

Sailing, with its graceful boats skimming across the water powered solely by the wind, is a captivating and ancient mode of transportation and recreation. While it might seem like magic, the principles behind sailing are firmly grounded in physics. The interplay between the wind, the water, and the structure of the sailboat creates an intricate dance of forces that propels the vessel forward. In this article, we will delve into the physics of sailing to uncover the mechanics behind this age-old practice.

The Role of the Wind: Lift and Drag

At the heart of sailing lies the wind – a dynamic force that fills the sails and provides the energy needed to move the boat. The interaction between the wind and the sail is based on the principles of lift and drag, which are also fundamental to aviation and other fluid dynamics.

When wind flows over the curved surface of a sail, it creates an area of lower pressure on the windward side and an area of higher pressure on the leeward side. This pressure difference generates lift, much like an airplane wing. The sail’s shape and angle in relation to the wind determine the amount of lift generated. By adjusting the sail’s angle, sailors can control the lift and subsequently the boat’s direction.

Drag, on the other hand, is the resistance the sail experiences due to the friction between the air molecules and the sail’s surface. While drag can’t be entirely eliminated, modern sail designs aim to minimize it to ensure the boat moves efficiently through the water.

>>Also Read: How Fast Can a Sailboat Go?

The Concept of Apparent Wind

In a straightforward scenario, a sailboat would travel directly downwind with the wind pushing the sails from behind. However, sailing often involves moving at angles to the wind, a concept that introduces the notion of apparent wind.

Apparent wind is the combination of the true wind – the wind blowing over the Earth’s surface – and the wind generated by the boat’s motion through the water. As the boat sails at an angle to the true wind, the wind experienced by the boat appears to come from a different direction and at a higher speed than the true wind. This apparent wind is crucial for maintaining lift on the sails, even when sailing against the true wind direction.

Points of Sail: Navigating the Wind Angles

To understand how sailboats maneuver, it’s essential to grasp the concept of points of sail. These are specific angles at which a boat can sail relative to the wind direction. The main points of sail are:

• Close-hauled:  Sailing as closely as possible into the wind. This requires the sails to be trimmed in tightly, and the boat moves forward at an angle against the wind.
• Close reach:  Sailing diagonally to the wind, between close-hauled and a beam reach.
• Beam reach:  Sailing perpendicular to the wind. This is often the fastest point of sail as the boat can fully capture the wind’s energy.
• Broad reach:  Sailing diagonally away from the wind, between a beam reach and running.
• Running:  Sailing directly downwind, with the wind coming from behind the boat.

By adjusting the angle of the sails and the boat’s course, sailors can optimize their speed and direction according to the prevailing wind conditions.

>>Also Read: Points of Sail Explained

Balancing Forces: The Keel and Centerboard

While the wind provides the forward propulsion, the boat’s stability and ability to maintain a straight course are maintained through the use of a keel or centerboard, depending on the type of sailboat.

The keel is a heavy, fin-like structure located beneath the boat’s hull. It serves two main purposes: counteracting the force of the wind pushing the boat sideways (referred to as leeway) and providing ballast to keep the boat upright. The keel’s shape generates lift in the water that counters the lateral force of the wind, allowing the boat to sail closer to the wind without being pushed sideways.

For boats with a centerboard, which is a retractable fin located in the center of the boat, the principle is similar. By adjusting the centerboard’s depth, sailors can control the boat’s lateral resistance and stability.

>>Also Read: How do Sailboats Move Without Wind?

Tacking and Jibing: Changing Course with the Wind

Sailing isn’t just about going in a straight line – sailboats can change direction by tacking and jibing.

Tacking involves turning the boat’s bow through the wind so that the wind changes from one side of the boat to the other. This maneuver allows the boat to change direction while maintaining forward momentum. During a tack, the sails are let out to spill the wind’s energy, the bow crosses through the wind, and then the sails are trimmed in again on the new tack.

Jibing, on the other hand, is a maneuver where the stern of the boat crosses through the wind. This is often used when sailing downwind. Jibing requires careful coordination, as the sails can swing abruptly from one side to the other, potentially causing powerful forces.

Sail Shape and Rigging: Aerodynamics of Sailing

The shape of the sail and the configuration of the rigging also play a vital role in the physics of sailing. Modern sail designs use a combination of materials and engineering to create sails that are both efficient and durable.

The angle at which the sail is set, known as the angle of attack, determines the amount of lift and drag produced. Sails are typically designed with a curved shape, known as camber, which allows for better lift generation and minimizes drag. Adjustable controls such as the cunningham, outhaul, and boom vang enable sailors to modify the shape of the sail according to wind conditions.

The mast, rigging, and other structural elements of the sailboat are designed to distribute forces evenly and provide stability. The tension in the rigging affects the shape of the mast, which, in turn, affects the shape of the sail. Balancing these factors ensures optimal sail performance and boat stability.

>>Also Read: Most Common Sailing Terms

How Does Sailing Work? The Physics of Sailing – In Conclusion

Sailing is a captivating interplay of physics and nature, where the wind’s energy is harnessed to propel a boat gracefully across the water. By understanding the principles of lift, drag, apparent wind, and the mechanics of sail shape and rigging, sailors can navigate the seas with precision and finesse. From the ancient mariners who first ventured out onto the open waters to the modern sailors competing in high-tech races, the physics of sailing remains a timeless and essential art.

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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How do sailboats sail upwind?

Yachts aren’t blown along – they are ‘sucked along’.

The sail creates a low pressure zone in front of the sail and a high pressure zone behind the sail.

The boat moves into the low pressure zone and is sucked forward.

This is very like the idea of an  aeroplane wing , which is curved in a similar way to a sailboat’s sail as you can see below.

In airplane wings, the pressure on the top of the wing is less than the pressure on the bottom of the wing, because  the air moves faster on the top , so this difference in pressure creates a force on the wing that lifts the wing up into the air.

The curve on the sail makes the air travel a longer distance over the top of the wing and a shorter distance behind it.

The longer distance the air flows, the lower the pressure, and this is why the aircraft climbs into the sky.

Below the level of the water on the boat, the sailboat’s shape helps force the boat to go straight forward as opposed to in the direction of the wind.

In addition you have the keel that is shaped like a wing, and has a lot of weight to stop the yacht from falling over when pushed sideways by the wind.

With the sails being unable to push the boat sideways or onto its side, the sails drive the boat forward.

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Resistive forces

Predicting speed, the physics of sailing.

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Bryon D. Anderson; The physics of sailing. Physics Today 1 February 2008; 61 (2): 38–43. https://doi.org/10.1063/1.2883908

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In addition to the recreational pleasure sailing affords, it involves some interesting physics. Sailing starts with the force of the wind on the sails. Analyzing that interaction yields some results not commonly known to non-sailors. It turns out, for example, that downwind is not the fastest direction for sailing. And there are aerodynamic issues. Sails and keels work by providing “lift” from the fluid passing around them. So optimizing keel and wing shapes involves wing theory.

The resistance experienced by a moving sailboat includes the effects of waves, eddies, and turbulence in the water, and of the vortices produced in air by the sails. To reduce resistance effectively by optimizing hulls, keels, and sails, one has to understand its various components.

Moving air has kinetic energy that can, through its interaction with the sails, be used to propel a sailboat. Like airplane wings, sails exploit Bernoulli’s principle. An airplane wing is designed to cause the air moving over its top to move faster than the air moving along its undersurface. That results in lower pressure above the wing than below it. The pressure difference generates the lift provided by the wing.

There is much discussion of whether the pressure difference arises entirely from the Bernoulli effect or partly from the wing’s impact and redirection of the air. Classic wing theory attributes all the lift to the Bernoulli effect and ascribes the difference in wind speeds above and below the wing to the wing’s asymmetric cross-sectional shape, which caused the path on top to be longer. But it’s well known that an up–down symmetrical wing can provide lift simply by moving through the air with an upward tilt, called the angle of attack. Then, despite the wing’s symmetry, the wind still experiences a longer path and thus greater speed over the top of the wing than under its bottom. A NASA website has an excellent discussion of the various contributions to lift by an airplane wing. 1 It disputes the conventional simple version of wing theory and emphasizes that lift is produced by the turning of the fluid flow.

The case is similar for sailboats. A sail is almost always curved and presented to the wind at an angle of attack. The situation is shown schematically in figure 1(a) . The wind moving around the “upper,” or downwind, side of the sail is forced to take the longer path. So the presence of the surrounding moving air makes it move faster than the air passing along the “lower,” or upwind, side of the sail. Measurements confirm that relative to the air pressure far from the sail, the pressure is higher on the upwind side and lower on the downwind side.

Figure 1. Forces on a moving sailboat. (a) Sail and keel produce horizontal “lift” forces due to pressure differences from different wind and water speeds, respectively, on opposite surfaces. (b) The vector sum of lift forces from sail and keel forces determines the boat’s direction of motion (assuming there’s no rudder). When boat speed and course are constant, the net lift force is precisely balanced by the velocity-dependent drag force on the boat as it plows through water and air.

For downwind sailing, with the sail oriented perpendicular to the wind direction, the pressure increase on the upwind side is greater than the pressure decrease on the downwind side. As one turns the boat more and more into the direction from which the wind is coming, those differences reverse, so that with the wind perpendicular to the motion of the boat, the pressure decrease on the downwind side is greater than the pressure increase on the upwind side. For a boat sailing almost directly into the wind, the pressure decrease on the downwind side is much greater than the increase on the upwind side.

Experimenting with what can be done, a beginner finds some surprising results. Sailors know well that the fastest point of sail (the boat’s direction of motion with respect to the wind direction) is not directly downwind. Sailboats move fastest when the boat is moving with the wind coming “abeam” (from the side). That’s easily understood: When a sailboat is moving directly downwind, it can never move faster than the wind because, at the wind speed, the sails would feel no wind. In fact, a boat going downwind can never attain the wind speed because there’s always some resistance to its motion through the water.

But when the boat is moving perpendicular to the wind, the boat’s speed doesn’t decrease the force of the wind on the sails. One sets the sails at about 45° to the direction of motion—and to the wind. The boat’s equilibrium speed is determined by the roughly constant force of the wind in the sails and the resistance against the boat’s motion through the water. If the resistance can be made small, the velocity can be large. That’s seen most dramatically for sail iceboats, which skate on the ice with very little resistance. They can glide along at speeds in excess of 150 km/h with the wind abeam at speeds of only 50 km/h! Of course sailboats plowing through the water experience much more resistance. Nonetheless, some specially constructed sailboats have attained speeds of more than twice the wind speed.

It was recognized centuries ago that a sailboat needs something to help it move in the direction in which it’s pointed rather than just drifting downwind. The answer was the keel. Until the development of modern wing theory, it was thought that one needed a long, deep keel to prevent side-slipping. But now it’s understood that a keel, like a sail, works by providing sideways lift as the water flows around it, as shown in figure 1(a) . A keel must be symmetrical for the sailboat to move to either side of the wind.

A keel works only if the motion of the boat is not exactly in the direction in which it’s pointed. The boat must be moving somewhat sideways. In that “crabbing” motion, the keel moves through the water with an angle of attack. Just as for the sails in the wind, that causes the water on the “high” (more downstream) side of the keel to move faster and create a lower pressure. Again, the net lift force on the keel is due to the combination of that decreased pressure on the high side and increased pressure on the other (low) side.

In figure 1(b) , the keel lift thus generated points almost in the opposite direction from the lift provided by the sails. The two vectors can be resolved into components along and perpendicular to the boat’s direction of motion. For a sailboat moving in equilibrium—that is, at constant speed in a fixed direction—the transverse lift components from sail and keel cancel each other. The component of the driving force from the sails in the direction of motion is the force that is actually moving the boat forward. For equilibrium motion, that force is balanced by the opposing component of the keel lift plus the total resistive force.

Wing theory, developed over the past 100 years for flight, indicates that the most efficient wing is long and narrow. Vortices produced at the wing tip cost energy. A long, narrow wing maximizes the ratio of lift to vortex dissipation, thus providing the best performance for a given wing surface area. That also applies to sailboat sails and keels.

It is now recognized that the most efficient keels are narrow from front to back and deep. Such a keel can have much less surface area than the old long keels. Less area means less resistance. Most modern racing sailboats, such as those used in the America’s Cup races, have deep, narrow keels that are very efficient at providing the lift necessary to prevent side-slipping. Of course, such keels are a problem for recreational sailors in shallow waters.

A sailboat experiences several kinds of resistance. The first is simply the resistance of the hull moving through water. As the boat moves, it shears the water. Water molecules adhere to the hull’s surface. So there must be a shear—that is, a velocity gradient—between the adhering molecular layer at rest with respect to the hull and the bulk of water farther away. The shear means that van der Waals couplings between water molecules are being broken. That costs energy and creates the resistive force, which becomes stronger as the boat’s speed increases. The energy dissipation also increases with the total area of wetted surface.

Although the effect is called frictional resistance, it’s important to realize that the resistive force in water is basically different from the frictional force between solid surfaces rubbed together. To reduce ordinary friction, one can polish or lubricate the sliding surfaces. That makes surface bumps smaller, and it substitutes the shearing of fluid lubricant molecules for shearing of the more tightly bound molecules on the solid surfaces.

For a boat moving through water, however, polishing the hull doesn’t eliminate the shearing of the molecules of water, which is already a fluid. The resistive force cannot be reduced significantly except by reducing the wetted surface. It does help to have a smooth surface, but that’s primarily to reduce turbulence.

The generation of turbulence is a general phenomenon in the flow of fluids. At sufficiently low speeds, fluid flow is laminar. At higher speeds, turbulence begins. Its onset has to do with the shearing of the molecules in the fluid. When the shearing reaches a critical rate, the fluid can no longer respond with a continuous dynamic equilibrium in the flow, and the result is turbulence. Its onset is quantified in terms of the Reynolds number

where ν is the velocity of the flowing fluid, μ is its viscosity, ρ is its density, and L is the relevant length scale of the system. Rearranging factors in equation (1) , one can think of R as the ratio of inertial forces ( ρν ) to viscous forces ( μ /L). In the late 19th century, English engineer Osborne Reynolds found that, with surprising universality, turbulence begins when that dimensionless parameter exceeds about a million.

For a boat of length L moving through water at velocity ν to see when turbulence begins in the flow along the hull, R is about 10 6   Lν (in SI units). A typical speed for a sailboat is 5 knots (2.4 m/s). At that speed, then, one should expect turbulence for any boat longer than half a meter. (Used worldwide as a measure of boat speed, a knot is one nautical mile per hour. A nautical mile is one arcminute of latitude, or 1.85 km.)

Because turbulence dissipates energy, it increases the resistance to motion through the water. With turbulence, a sailboat’s resistance is typically four or five times greater than it is when the flow along the hull is laminar. A rough surface will cause turbulence to be greater and begin sooner. That’s the main reason to have a smooth hull surface.

Turbulence also occurs in the air flowing along the surface of the sail. Water is a thousand times denser than air and 50 times more viscous. So for the air–sail system one gets

For a typical wind speed of 5 m/s, then, one gets turbulence if the sail is wider than about 3 meters. When turbulence forms in the air flow along the sail, the desired pressure difference between the two sides of the sail—its lift—is diminished.

Another important resistive force comes from vortex generation at the bottom of the keel and at the top of the sails. When the air or water moves around the longer-path side of the sail or keel, its speed increases and therefore its pressure falls. As the air or water moves along the sail or keel, it will respond to the resulting pressure difference by trying to migrate from the high-pressure side to the low-pressure side. Figure 2 sketches that effect for a keel. What actually happens, as shown in the figure’s side view, is that the flow angles a bit up on one side and down on the other. When those flows meet at the back of the sail or keel, the difference in their arrival angles has a twisting effect on the fluid flow that can cause a vortex to come off the top of the sail or the bottom of the keel.

Figure 2. Vortex formation by the keel. Unless the boat is sailing straight ahead, there’s a pressure difference between the two sides of the keel. As a result, the water flow angles down on the high-pressure (lower water-speed) side and up on the low-pressure side, creating a twist in the flow that generates vortices behind the bottom rear of the keel.

The effect is well known for airplane wings. Called induced drag, vortex formation costs energy. Figure 3 shows vortices generated at the tops of sails by racing sailboats moving through a fog. A long keel will generate very large vortices. By making the keel short and deep, one can increase the ratio of lift to energy dissipated by vortices. The same is accomplished—especially for sailboats racing upwind—by having tall, narrow sails. It’s also why gliders have long, narrow wings.

Figure 3. Sailtops form vortices visible in fog. The boats were participating in the 2001–02 Volvo Ocean Race off Cape Town, South Africa.

Because it’s often impractical to have a short, deep keel or a narrow, long wing, one can install a vane at the tip to reduce the flow from the high-pressure to the low-pressure side. On planes they’re called winglets, and on keels they’re simply called wings. A modern recreational or cruising sailboat will have a keel that’s a compromise between the old-fashioned long keels and the modern deep, narrow keels—with a wing at the bottom rear end to reduce induced drag. Such keel wings were first used by the victorious sailboat Australia II in the 1983 America’s Cup race. Modern wing theory also suggests that to minimize induced drag, keels and sails should have elliptic or tapered trailing edges. 2 Such shaped edges are now common.

A sailboat also has a resistance component due simply to its deflection of water sideways as it advances. That’s called form resistance, and it obviously depends on hull geometry. It’s easy to see that narrow hulls provide less resistance than do wider hulls. Any boat will always be a compromise between providing low form resistance and providing passenger and cargo space. Seeking to minimize form resistance for a given hull volume, shipbuilders have tried many basic hull shapes over the centuries. Even Isaac Newton weighed in on the question. He concluded that the best hull shape is an ellipsoid of revolution with a truncated cone at the bow.

Extensive computer modeling and tank testing have resulted in a modern hull design that widens slowly back from the bow and then remains fairly wide near the stern. Even with a wide stern, designers try to provide enough taper toward the back to allow smooth flow there. That taper is often accomplished by having the stern rise smoothly from the water rather than by narrowing the beam. If the flow from the stern is not smooth, large eddies will form and contribute to resistance.

As a boat moves through water, it creates a bow wave that moves with the speed of the boat. Water waves are dispersive; long waves propagate faster than short ones. Therefore the length of the full wave generated by the bow is determined by the boat’s speed. As a boat starts to move slowly through the water, one sees at first a number of wave crests and troughs moving down the side of the hull. As the boat speeds up, the wavelength gets longer and one sees fewer waves down the side. Eventually at some speed, the wave will be long enough so that there’s just one wave down the side of the boat, with its crest at the bow, a trough in the middle, and another crest at the stern (see figure 4 ). That’s called the hull speed.

Figure 4. Moving at hull speed, a sailboat generates a bow wave whose wavelength just equals the length of the boat’s water line. The wave crests at bow and stern, with a single well-formed trough in between.

If the boat speed increases further, the wavelength increases so that the second crest moves back behind the boat and the stern begins to descend into the trough. At that point, the boat is literally sailing uphill and the resistance increases dramatically. That’s called wave resistance. Of course, if one has a powerboat with a large engine and a flat-bottomed hull, one can “gun” the engine and cause the boat to jump up on the bow wave and start to plane on the water’s surface. Most sailboats don’t have either the power or the hull geometry to plane. So they’re ultimately limited by wave resistance.

The wave-resistance limit also applies to all other so-called displacement boats: freighters, tankers, tugs, and most naval vessels bigger than PT boats—that is, any boat that can’t rise to plane on the surface. The functional dependence of water-wave speed ν on wavelength λ is well known. From the limiting case for deep-water waves for the solution of the two-dimensional Laplace wave equation, 3 or from a simple derivation due originally to Lord Rayleigh, 4 one gets ν = g λ / 2 π ⁠ , where g is the acceleration of gravity. In the form commonly used by sailors in the US,

where the λ is in feet and ν is in knots.

If one equates the wavelength to the waterline length of a boat, equation (3) gives the boat’s hull speed. For a sailboat with a waterline length of 20 feet (6 m), the hull speed is 6 knots. For a large cruising sailboat with a waterline of 40 feet (12 m), it’s about 8 knots. And for a 300-foot-long naval vessel, it’s 23 knots. In practice, it’s very difficult to make a displacement boat go faster than about 1.5 times its hull speed.

Combining all the components of resistance for a sailboat moving at close to its hull speed, one finds that the frictional resistance contributes about a third of the total, and the wave resistance another third. Form resistance accounts for about 10%, as does the induced drag from vortex generation at the bottom of the keel. The assorted remaining contributions, including eddy formation behind the boat and aerial vortex generation by the sails, provide the remaining 10 to 15%. Of course the fractional contributions vary with boat speed, wave conditions, and the direction of motion relative to the wind.

One can exploit the physics of sailing to calculate boat speeds for a given sailboat for different wind speeds and points of sail. Such calculations are usually performed iteratively by computer programs that start from two basic vector equations to be solved simultaneously:

Here F drive is the total driving force in the direction of motion provided by the wind in the sails, and F resistance is the sum of all the resistive forces. The torques M heel and M righting are the heeling and righting moments caused by the wind in the sails and the weight of the hull and keel.

The force of the wind on the sail is calculated as a lifting force perpendicular to the apparent wind direction and a drag force in the direction of the apparent wind. (The apparent wind is the wind as perceived by an observer aboard the moving vessel.) These lift and drag forces are then resolved into components along and perpendicular to the direction of motion. The net force in the direction of motion is then F drive ⁠ , and the net force perpendicular to the boat’s motion is what produces the heeling moment. The two equations in ( (4) ) must be solved simultaneously because the angle of heel affects the total driving force.

Following Bernoulli’s principle, one takes the force of the wind in the sails to be proportional to the total sail area times the square of the apparent wind speed. The actual forces are then obtained with empirical lift and drag coefficients, given as functions of sail geometry and angle of attack. Frictional resistance is proportional to the hull’s wetted surface area and increases as the square of the boat’s speed. All the various contributions to total resistance involve empirical coefficients. Wave and form resistance are expressed as functions of the hull’s “prismatic coefficient,” which is an inverse measure of the tapered slimness of its ends.

There are simple and complex speed-prediction computer programs. Some that have been refined over decades for racing applications are kept private and closely guarded. Figure 5 shows the results of calculations I performed for a 30-foot (10-m) cruising sailboat using a publicly available program. 5 The figure shows the calculated boat speed as a function of wind speed and point of sail. The predicted boat speeds are greatest when one is sailing about 90° away from the wind direction. Sailors call that beam reaching. It yields a boat speed of about half the wind speed.

Figure 5. Speeds predicted by a computer model 5 for a 10-meter-long cruising sailboat, plotted for three different wind speeds from 6 to 20 knots as a function of the angle of the boat’s motion relative to the wind direction. (10 knots = 18.5 km/h.) An angle of 180° means the boat is “running” with the wind directly at its back. The fastest speeds are predicted when the boat is “beam reaching,” that is, moving at about 90° to the wind. The boat even makes some progress when it’s “close hauling” almost directly into the wind.

Such calculations are confirmed experimentally, with a degree of accuracy that depends on the sophistication of the model and on how much the program has been tuned for a specific kind of sailboat. Broadly speaking, a sailboat is faster if it is longer and narrower, with bigger sails and a smaller wetted surface. Such general rules can, of course, yield a boat that’s longer than one wants, or tips over too easily, or has too little room inside.

So every design feature is a compromise between competing needs. For sailing downwind, one wants fairly square sails, which are best at catching the wind. But for sailing upwind, taller, narrower sails are best, because they maximize the ratio of lift to energy lost by generating vortices. The most efficient keel is deep and narrow, to maximize lift with minimal surface area. But a deep keel is problematic in shallow waters. Shorter keels with wings or bulbs at the bottom usually represent the best compromise for overall sailing.

What’s the highest speed a sailboat can reach? The trick is to reduce resistance. An iceboat can outrun the wind because it has so little resistance. For a sailboat, the resistance comes primarily from having to plow through the water. The best way to reduce that resistance is to move less and less of the boat through the water. One answer is hydrofoils. They are vanes placed below the hull that raise it out of the water as the boat speeds up.

Sailboats with hydrofoils have reached speeds of more than 40 knots when the wind speed was barely half that. One such craft is shown in figure 6 . These vessels are not usually practical for cruising and other normal recreational activities. They’re sometimes dismissed as low-flying aircraft. A more practical alternative is the catamaran—a double-hulled sailboat. Catamarans are being developed to provide relatively stable, fast sailing. Although they are more expensive than traditional single-hull sailboats for a given amount of living space, catamarans are becoming increasingly popular.

Figure 6. A hydrofoil sailboat with solid, winglike sails, moving at about twice the wind speed with the wind abeam—that is, blowing from the side.

Bryon Anderson is an experimental nuclear physicist and chairman of the physics department at Kent State University in Kent, Ohio. He is also an avocational sailor who lectures and writes about the intersection between physics and sailing.

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• The Ultimate Guide to Sailing with the Wind: Mastering the Art of Wind Sailing

Sailing enthusiasts, both novice and experienced, understand the sheer thrill of harnessing the power of the wind to glide gracefully across the water. Wind sailing is a unique and exhilarating sport that requires skill, knowledge, and a deep connection with nature. In this comprehensive guide, we will delve into the intricacies of winds for sailing, sailboat wind dynamics, and strategies for sailing faster than the wind itself. So, hoist your sails and let's embark on this exciting journey! 

Understanding the Basics of Wind Sailing

What is wind sailing.

Wind sailing, often referred to as sailing or yachting, is a thrilling water sport that involves using the wind to propel a sailboat across the water's surface. Unlike motorized boating, wind sailing relies solely on the power of the wind to move the vessel, making it an eco-friendly and serene way to navigate the waters.

The Essentials of Wind and Sailing

To become a proficient wind sailor, it's crucial to grasp the fundamentals of wind and its interaction with a sailboat. Wind is the primary driving force behind sailing, and understanding its behavior is essential for safe and enjoyable sailing.

The Connection Between Wind and Sailboats

Sailboats are meticulously designed to harness the energy of the wind. This intricate dance between wind and sailboat is what makes wind sailing a captivating and challenging endeavor.

Choosing the Right Wind Conditions

Optimal wind speed for sailing.

One of the most critical factors in wind sailing is wind speed. Discover the ideal wind speeds for different types of sailing and how to make the most of your sailing experience.

Interpreting the Sailing Wind Chart

The sailing wind chart is a sailor's best friend. Learn how to read and interpret this valuable tool to plan your wind sailing adventures effectively.

Sailing Away from the Wind: Points of Sail

Exploring different points of sail, including upwind and downwind sailing, will expand your wind sailing horizons and open up new possibilities for exploration.

Sailboat Wind Dynamics

How sailboats harness the wind.

Unlock the secrets behind how sailboats capture and utilize the power of the wind. Understanding sailboat wind dynamics is the key to becoming a skilled wind sailor.

The Anatomy of a Sail

Delve into the components of a sail and learn how subtle adjustments can significantly impact your sailing performance and speed.

Adjusting Sail Trim for Optimal Performance

Discover the art of sail trim, where precision adjustments to your sail's position and shape can make your sailboat sail faster and more efficiently.

Sailing Faster than the Wind

The physics behind sailing faster.

Sailing faster than the wind may seem counterintuitive, but it's a reality for experienced sailors. Explore the physics that make this feat possible.

Strategies and Techniques

Master the strategies and techniques that will allow you to outpace the wind, leaving you with a sense of exhilaration and accomplishment.

The Role of Sailboat Design

Sailboat design plays a crucial role in achieving higher speeds. Learn how to choose or optimize your sailboat for the ultimate wind sailing experience.

Read our top notch articles on topics such as sailing, sailing tips and destinations in our Magazine .

Check out our latest sailing content:

Safety precautions and wind sailing etiquette, staying safe on the water.

Safety should always be a priority when wind sailing. Discover essential safety precautions to ensure you have a secure and enjoyable sailing adventure.

Respecting Other Sailors

Sailing is a communal activity, and adhering to wind sailing etiquette is essential for a harmonious experience on the water.

Environmental Responsibility

As a wind sailor, it's your duty to protect the environment. Learn how to minimize your ecological footprint while enjoying the beauty of the water.

Mastering Wind Sailing: Tips and Tricks

Perfecting your tacking and jibing.

Tacking and jibing are essential maneuvers in wind sailing. Master these techniques to navigate efficiently and enjoy a smoother sailing experience.

Reading the Wind

The ability to read the wind is a skill that separates novice sailors from experts. Learn how to interpret wind patterns and adjust your sails accordingly.

Enhancing Your Sailing Skills

Continuous improvement is the key to becoming a proficient wind sailor. Explore tips and tricks to enhance your skills and take your sailing to the next level.

Common Challenges in Wind Sailing

Dealing with unpredictable wind shifts.

Wind shifts can be challenging to navigate. Discover strategies for handling unexpected changes in wind direction and strength.

Navigating Strong Winds

Sailing in strong winds can be both exhilarating and daunting. Learn how to manage high winds safely and effectively.

Handling Gusts and Lulls

Gusty winds and lulls can pose challenges to even the most experienced sailors. Explore techniques for maintaining control in varying wind conditions.

Sailing Wind Speed Chart: Your Ultimate Reference

Decoding the sailing wind speed chart.

The sailing wind speed chart is a comprehensive reference tool for wind sailors. Learn how to decode and utilize this valuable resource.

Wind Speed and Your Sailboat

Understand the relationship between wind speed and your sailboat's performance to optimize your sailing experience.

Conclusion: Embrace the Wind, Master the Waves

Celebrating the beauty of wind sailing.

Wind sailing offers a unique connection with nature and a sense of freedom that few other activities can match. Embrace the wind, and let it guide you on unforgettable journeys.

Unleash Your Inner Sailor

With the knowledge and skills acquired from this guide, you're well on your way to becoming a proficient wind sailor. Unleash your inner sailor and embark on adventures that will leave you breathless.

Set Sail for New Adventures

The world of wind sailing is vast and varied, with endless opportunities for exploration. It's time to set sail for new adventures and create memories that will last a lifetime.

So what are you waiting for? Take a look at our range of charter boats and head to some of our favourite  sailing destinations.

I am ready to help you with booking a boat for your dream vacation. Contact me.

Denisa Kliner Nguyenová

MAIN FUNCTIONAL REQUIREMENT:   Propel a boat with or against the wind

DESIGN PARAMETER: Airfoil (the sail)

A BIT OF HISTORY:

Square Sails 3000 BC - 900 AD

• Wind Force + Drag Force = Boat Mass * Acceleration. The wind force overcomes the drag force of the boat.
• Drag Force = Water Pressure * Keel Area + Air Pressure* Exposed Boat Area Most of the drag is due to the keel moving through the water. The sails, lines, mast, crew and cargo also add wind resistance.
• Wind Force = Wind Pressure* Sail Area. The greater the wind pressure and the greater the area of the sail, the greater the wind force.

Lanteen/Triangle Sails 900 AD

DOMINANT PHYSICS:

BERNOULLI'S EQUATION

Edmund Bernoulli theorized in 1738 that under certain conditions , one can the energy in a fluid system is constant.

P + 1/ 2r V^2 + gh = C

P = Fluid Pressure [N/m^2] r = Fluid Density [kg/m^3] V = Fluid Velocity [m/s] g = Gravitational Acceleration Constant [N/m^2] h = Height [m]

Bernoulli's principle may be applied to when a fluid flows outside the boundary layer. The flow must furthermore be modeled as incompressible, steady, and frictionless.

(Put Bernoulli airfoil picture in here)

Usually, one can assume the gravitational effects are negligible compared to the magnitude of the increase in VELOCITY which results in a DECREASE in PRESSURE. The streamlines separate at the leading edge of the airfoil and meet again at the trailing edge. The pressure above is LOWER than the pressure below, creating a LIFTING FORCE.

The other lift theory for is based on EULER'S EQUATION.

EULER'S EQUATION

    dP/dn = r V^2/R

P = Fluid Pressure [N/m^2][psi] n = Normal Vector to Curved Streamline r = Fluid Density [kg/m^3] V = Fluid Velocity [m/s] R = Radius of Curvature of Streamline [m]

The air pressure above the airfoil along a NORMAL VECTOR from the wing surface is inversely proportional to the distance from the RADIUS OF CURVATURE. At a certain distance above the airfoil is AMBIENT air pressure. The pressure INCREASES from the center of curvature along the normal vector until it reaches ambient pressure. The air pressure closer to the airfoil thus must be LOWER than the ambient pressure. Again, the pressure above is lower than the pressure below and a LIFTING FORCE is created.

For more on airfoils and lift, see How An Airfoil Works by Mealani Nakamura and How Hydrofoils Work by Tina Rosado.

HOW DOES LIFT SAILBOATS USE LIFT?

When the boat sails "into the wind", the bow is pointed into the APPARENT WIND, which is the vector resolution of the TRUE WIND and the BOAT COURSE.

The SAIL in the wind acts as an AIRFOIL and the HULL in the water acts as a HYDROFOIL, so there are two sets of forces acting on a sailboat: AERODYNAMIC and HYDRODYNAMIC

AERODYNAMIC FORCES

(insert aerodyn forces )

There are two ways to examine the aerodynamic forces acting on the boat.

• The DRIVING FORCE is the thrust that moves the boat along its course.
• The HEELING FORCE is perpendicular to the course. It spills wind, decreases speed, and tips the boat.

The goal is to maximize the driving force. However, as the driving force increases, so does the heeling force. The sailor makes a compromise between speed and stability.

• The low pressure over the curved sail creates a crosswind LIFT force.
• Viscous and pressure effects result in DRAG opposite the motion of the boat
• The LIFT and DRAG may be resolved into a TOTAL AERODYNAMIC FORCE (AF).
• The angle e a between the LIFT and the AF is the AERODYNAMIC EFFICIENCY, a measure of speed.

  Cot e a = L/D.

HYDRODYNAMIC FORCES

• The curved surface of the hull creates a HYDRODYNAMIC SIDE FORCE (SF), which balances the aerodynamic HEELING FORCE.
• The water pressure over the cross-sectional area of the keel creates a RESISTANCE (R).

A large SF increases STABILITY, but is proportional to the resistance, which reduces SPEED.

• These two may be resolved into a TOTAL HYDRODYNAMIC FORCE (HF).
• The angle e h between the SF and HF is the HYDRODYNAMIC EFFICIENCY, a measure of stability.

Cot e a = SF/R

HOW DO SAILORS MAXIMIZE BOAT EFFICIENCY?

The angle between the boat course and the apparent wind direction, b, is the boat's ANGLE OF ATTACK.

b = e a + e h.

The angle between the sail CHORD LINE and the wind direction, a is the sail's ANGLE OF ATTACK. If the sail points straight into the wind, there will be no airfoil shape, and no lift. The sail must be slightly angled The largest speeds are obtained while sailing as close to the wind as possible, while the sail chord is approximately co-linear with the boat's centerline. The sailor must turn the boat to follow the course, but alters the sail position (lets the sail out) to maintain the sail's optimum angle of attack.

The sailor may also change the sail's shape for changing wind speeds.

A thick airfoil generates more lift, but also more drag. If you subscribe to Bernoulli's theory, the increases are due to the higher velocity and lower pressure. If you prefer Euler, the lower pressure is due to the smaller radius of curvature . For the same reasons, a thin airfoil generates less drag, but also less lift.

The sail is "kept tight" in the shape of the thin airfoil at moderate to high wind velocities. Large lift is coupled with large heeling and the boat may tip over. When the wind speed is low, the sail is "let out" a bit to generate more lift, and thus more driving force. However, if the sail is let out too much, it will luff and force the boat away from the wind.

LIMITING PHYSICS:

None Submitted

PLOTS/GRAPHS/TABLES:

WHERE TO FIND SAIL BOAT:

On the water!

REFERENCES/MORE INFORMATION: Airfoil and Hydrofoils

Marchaj, C.A. Aero-Hydrodynamics of Sailing . Dodd, Mead & Company, 1979.

Evans, Michael E. MSME. Email from January 13, 1998.

Perdichizi , Richard. Senior Technical Instructor, Massachusetts Institute of Technology Aerodynamics and Astronomics Department. Conversation on January 14, 1998.

The 6 Points of Sail: Diagram of Wind Direction and Sail Trim

Points of sail are the different angles at which a sailboat can sail in relation to the wind. Understanding these points is crucial for anyone who wants to learn how to sail, and it’s usually taught in sailing schools. Each point has its own characteristics that determine the boat’s speed and direction.

The main points of sail are:

• Into the wind: The no-sail zone
• Close-hauled: Sailing as close to the wind direction as possible.
• Close reach: Sailing between a beam reach and close-hauled, at an angle to the wind.
• Beam reach: Sailing perpendicular to the wind, with the wind hitting the side of the sail.
• Broad reach: Sailing with the wind coming from behind at an angle.
• Running: Sailing directly downwind, with the wind coming from behind.

Understanding how to navigate through each point of sail effectively takes practice and patience. It’s important to know your boat’s capabilities and limitations so you can adjust your technique accordingly.

Points of Sail

To comprehend the points of sail, it is essential to grasp the relationship between a sailboat’s trajectory and the direction of the true wind. The points of sail encompass a full 360-degree circle, each segment representing a distinct sailing direction.

1. In Irons (Into the Wind)

Embarking on our journey, we encounter the point of sail known as “into the wind” or “in irons.” This position aligns your sailboat directly into the wind, within a range of plus or minus 45 degrees from 0 degrees. While this point of sail hinders forward progress, it serves as a pivotal moment for executing various sailing maneuvers, such as tacking and mast adjustments.

Tacking involves transitioning from one side of the wind to the other, crossing the into the wind point of sail. It is crucial to navigate this maneuver swiftly, as prolonged exposure in this “no-go zone” can impede momentum. Should you fail to traverse this point expediently and become stuck, it is referred to as being “taken aback.”

2. Close Hauled

Advancing beyond the into the wind point of sail, we arrive at the close hauled position. Sailing close hauled refers to navigating upwind, moving toward the wind’s direction. This point of sail, often referred to as “beating” or “working windward,” offers an intimate connection with the wind, enriching your experience as both captain and crew member.

During close hauled sailing, your sail assumes the role of an airplane wing, cutting through the wind head-on and generating optimal lift. Precise sail trim is paramount in this configuration, with tighter adjustments maximizing the sailboat’s ability to “point” towards the wind and optimize performance.

3. Close Reach

Continuing our voyage, we transition from close hauled to the close reach point of sail. Positioned between close hauled and beam reach, this segment represents a thrilling and rapid sailing direction. Sailors often revel in the exhilaration offered by the close reach point of sail.

Close reach resides closest to the “no-go zone” compared to other points of sail. It’s important to pay close attention to the wind and how the sails are set when sailing close reach. The sail needs to be tight, like when sailing close hauled, but loose enough so it’s just not luffing . This will help the boat sail efficiently when sailing upwind.

4. Beam Reach

As our sailboat maneuvers further away from the wind’s direction, we arrive at the beam reach point of sail. In this configuration, the sailboat is perpendicular to the wind, either on the starboard or port side. Notably, the beam reach point of sail boasts both speed and comfort, making it a preferred choice among sailors.

At beam reach, your sails are partially let out, the wind’s interaction with the sails in this position optimizes energy transfer from the lateral force to forward propulsion. The result is a harmonious conversion of wind power into the sailboat’s forward motion, ensuring an exhilarating and controlled sailing experience.

5. Broad Reach

Progressing from the beam reach, we venture into the realm of the broad reach point of sail. As we veer further downwind, the sails are let out approximately two-thirds of their capacity. At this stage, the wind doesn’t approache directly from astern but at an angle. As a consequence, the sail begins to function more like a parachute, relying on air resistance to maintain momentum.

While sailing on a broad reach, you will experience a less intense sensation of wind, yet your sailboat will continue to make steady progress. The sailboat’s orientation during this point of sail evokes a sense of descending down a slope. The serenity of the wind’s speed, coupled with the reliable forward movement, makes the broad reach a personal favorite among many sailors.

Our final point of sail brings us to the running point—a sailboat’s true downwind trajectory. In this configuration, the sails are fully let out, allowing the wind to propel the sailboat directly from behind. The experience of sailing on a running point is akin to running downhill, with the force of the wind acting as a powerful propeller.

Also known as a “dead run,” the running point of sail demands minimal attention to sail trim but requires careful attention to prevent an accidental jibe. Depending on wind conditions, this point presents an opportunity to hoist a gennaker or spinnaker sail, optimizing the sailboat’s performance when sailing directly downwind. The consistent wind direction and intensity make it an ideal moment to embrace the vibrant colors and expansive sails.

Conclusion for Points of Sail

In conclusion, understanding the fundamentals of sailing directions is crucial for any sailor. Knowing how to navigate each point of sail can make the difference between a successful voyage and a disastrous one. From sailing into the wind to running downwind with ease, each direction presents its own set of challenges and rewards.

Close hauled and close reach requires precision and skill, while beam reach provides a comfortable ride, and broad reach allows for thrilling surfing. Running downwind requires careful attention to prevent an accidental jibe.

As with any skill, practice makes perfect. Take time to familiarize yourself with each point of sail and experiment with different techniques. With patience and perseverance, you will soon become proficient in navigating all directions.

Remember that safety should always come first when out on the water. Always wear appropriate gear and follow proper procedures to ensure a safe journey.

How do I determine the point of sail I’m on?

To determine your point of sail, observe the angle of the wind relative to your boat. Look at the direction the wind is coming from and compare it to the direction your boat is heading. Adjust your sails accordingly to optimize your performance and balance.

What constitutes the best point of sail?

Determining the best point of sail is subjective and varies based on personal preference. However, the beam reach point of sail stands out as the fastest and most comfortable configuration. The optimal balance between lateral wind force and resisting keel force facilitates unparalleled forward movement on a sailboat.

How does the point of sail affect the boat’s heel?

The point of sail has a significant impact on a boat’s heel or stability. When sailing upwind, the boat tends to heel more due to the higher force generated by the sails. As you bear away and sail downwind, the boat’s heel decreases, and it becomes more stable. Proper sail trim can help maintain a balanced heel and overall stability throughout different points of sail.

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How to Sail Into the Wind – Tacking a Sailboat

One of the first sailing fundamentals you learn with you’re new to the world of sailing is the idea of sailing a boat into the wind. Sailboats can sail in the direction of the wind, but they do so by making a zig zag course made up of a series of maneuvers called tacks.

Table of Contents

Why does a sailboat tack, what is a tack of a sail, what are the points of sail depending on the wind direction, what’s the difference between a port or starboard tack, what’s the difference between a tack and a jibe (gybe), how to tack a sailboat – step by step, how to tack in sailing kept simple, faqs (frequently asked questions).

Tack is a confusing word because it’s used in various ways on a sailboat. Depending on its usage, it can be either a noun or a verb.

First, as a noun, a tack is a maneuver that a sailboat makes when it turns in the direction of the wind blows. For example, a boat may be sailing on a port tack, with the wind coming from the left side of the boat. After the boat tacks—which in this case would be a turn to the left—the boat will be on a starboard tack, with the wind coming from the right-hand side.

As a verb, a skipper might yell, “Ready to tack!” to their crew to let them know that the boat is about to tack. An alternative command is “Ready about!”

Since a sailboat cannot sail directly into the wind, a boat makes a zig-zag course over the water to go in that direction. The zig-zag course is made up of a series of tacks.

The word “tack” has a second, entirely different definition on a sailboat, too. When discussing the parts of a sail, the tack is the lower rear corner of a triangular sail. So, the tack of a mainsail is the end attached at the back of the boom. The tack of a foresail, like a jib, is the one that you attach the jib sheets to.

The other two corners of sail are the head (at the top) and the clew (at the forward edge). The edges of sail are called the leech, luff, and foot. So more specifically, the tack is the corner where the leech and the foot meet.

Sailboats can sail in nearly any direction except directly into the wind. Each direction has a different name and is known as a point of sail .

Sailors measure their angle to the wind based on the apparent wind angle (AWA). The AWA is simply the number of degrees from the bow that the wind is located. If a boat is headed dead into the wind, the AWA is 0 degrees. If the boat is headed dead downwind, the AWA is 180 degrees. Neither of these directions is optimal, so normal sailing occurs between 45 and 160 degrees AWA.

• Close Hauled — A boat that is as close to sailing upwind as it can is said to be “close-hauled.” In this scenario, the sails are tightly sheeted, and monohulls will be healed over. The AWA that a boat can sail depends on its design. Most boats cannot sail closer than 45 degrees to the wind. Colloquially sailors call sailing close-hauled “beating.”
• Close Reaching — A bit “farther off the wind,” and the boat will be close reaching. This is usually between 60 and 90 degrees AWA. 
• Reaching — A boat is reaching when it is precisely 90 degrees AWA. This is actually the fastest point of sail for most boats.
• Broad Reaching — If a boat is reaching, but the wind is behind the beam, it is on a broad reach. This occurs between 90 and 120 degrees AWA.
• Running — When a boat is on a run, it is sailing downwind. In this situation, the sails act less like airplane wings generating lift and more like leaves blowing over the water. 
• Wing-on-Wing — Wing-on-wing is a sailing maneuver, not a point of sail. But it occurs when a boat is more or less sailing dead downwind (180 degrees AWA). When a boat is wing-on-wing, one sail is on a starboard tack, and the other is on a port tack.

How Does a Sailboat Sail Into the Wind?

Contrary to what many people think, modern sailboats can sail in the direction of the wind . In fact, they can sail in nearly every direction relative to the wind except one. But they cannot sail directly into the wind. So if the wind blowing on the water today is out of the direction of your desired course, you’ll have to tack back and forth to get there.

For the sail to work, it needs to have air pushing on one side of it. If the boat is pointed directly into the wind, the sails will flap like flags on a pole. When this happens, the boat is said to be “in irons” and will eventually come to a stop.

How close to the wind a boat can sail depends on its design. Racing sailboats can do the best and generally sail within 30 degrees of the wind. However, cruising boats usually fall somewhere in the 45 to 60-degree range due to their wider beams and shallower keels.

The boat’s direction is always described in terms of the wind for a sailor. As such, one of the most fundamental terms in sailing is which tack a sailboat might be on. A port tack describes a boat with the wind coming over the port railing, so the sails are on the boat’s starboard side. Conversely, a boat on a starboard tack has the wind over that rail and the sails on the port side.

Describing which tack a boat is on is vital in racing and right of way rules. Rule 12 of the COLREGs , the internationally agreed-upon rules that govern shipping, says that when two sailing vessels meet, the vessel on the starboard tack has the right of way.

If a tack has an opposite maneuver, it is likely a jibe, which is sometimes spelled “gybe.”

A jibe occurs when sailing downwind. For example, if a boat is running on a port tack and wants to switch to the opposite tack, they could go the long way around and tack through the wind, or they could sail through dead downwind. Passing dead downwind so that the sails switch is called a jibe.

Jibes are more dangerous maneuvers that tacks for a few reasons. A planned jibe that is well executed is perfectly safe, but the force of the boom passing over the boat can be significant. All crew should know that the jibe is occurring and duck down to avoid getting smacked by the boom.

An accidental jibe, which isn’t planned, can be catastrophic. The force of the boom crashing over the boat can be immense if the winds are strong. It can easily tear the sail, and brake lines or damage the boom or gooseneck fittings.

You should always take jibes slowly and carefully. The stronger the winds, the more careful you should be. When tacking, the crew’s attention is focused on the jib sheets, but in a jibe, the crew must pay close attention to the mainsail and boom. The jib will usually be blanketed by the wind and easy to control when sailing so deeply downwind, so the jib sheet will be easy to manage.

Anytime a jibe is imminent, be it purposeful or accidentally, the skipper shouts, “Jibe ho!” This is to let everyone know to be ready for the maneuver—or at least to get out of the way of the boom. In light wind, it is usually a nonevent, but care should be taken regardless.

How to tack a boat depends on the boat and how it’s set up. First, the boat is sailed close-hauled on the standard modern sloop with both sails sheeted in tight. With the mainsail brought in, it will be self-tending on its boom.

So besides turning the wheel, the crew needs to only worry about the jib. The crew will watch the jib as the skipper turns the boat and brings the helm about. When the sail begins to luff or flap, the crew will release the working sheet from its winch and start to bring in the lazy jib sheet on the other side of the boat.

The slacker you can take out of the line, the tighter the tack. Once the slack is out and the line secured on the drum, you can bring the sail in with the help of the winch handle.

The boat speed at which the crew works to switch the sheet depends greatly on the sort of sailing you’re doing. If it’s a solo skipping working alone with only the help of the sailboat autopilot , the emphasis is on making the tacking maneuver easy and safe. This means taking it slow and not rushing anything.

On the other hand, if the crew is prepping for a race, boat speed is of the essence. So they’ll want to pull off the tacking maneuver perfectly in sync. A sloppy tack means that the boat will slow down unnecessarily, and recovering from it may mean losing a little ground by sailing on a reach while the boat builds up boat speed again.

A good skipper will work out how to tack with their crew in advance. Tacking involves good communication and teamwork on a boat with more than one person. Cruising boats may care little if their tack is a little sloppy, but on a racing boat, a clean tack means no wasted time and competitive advantage.

How to tack sailing boats might sound complicated, but it isn’t. It’s one of the simplest maneuvers to do in the sailing world, and it’s safe to do it in most conditions. Basic sailboat training begins with tacks because it requires understanding how a boat sails into the wind and how to handle it in different situations.

What is a tack on a sailboat?

The word “tack” has a few meanings on a sailboat. The most common definition involves how a sailboat sails into the wind. A sailboat cannot steer directly into the wind and instead must follow a zig-zag course over the ground to make progress in that direction. To tack the sailboat is the action of turning its bow through the wind. This maneuver also called “a tack” (noun), is used to sail into the direction of the wind. Also, a sailboat can be on a port tack or starboard tack, depending on which side of the sails the wind is coming from. Finally, the tack of a sail is the bottom rear corner of a triangular sail. 

What is the difference between a tack and a jibe?

Both a tack and jibe (sometimes spelled “gybe”) are used to describe maneuvers in which the boat is steered onto a new heading relative to the wind. In a tack, the boat is steered through the wind so that the wind is blowing from the opposite side of the boat. A jibe is done downwind but accomplishes the same thing. The boat is steered through a 180-degree apparent wind angle (AWA) during a jibe. The sails will switch in much the same way they do during a tack, but it is a very different maneuver.

What does tack mean for a ship?

A tack is a maneuver on a sailing ship where the ship’s bow is steered through the wind. After a ship tacks, the wind will be coming over the opposite rail. A ship’s sails will not work when pointed directly into the wind, so a ship must complete a series of tacks and make a zig-zag course over the ground to sail windward. 

Matt has been boating around Florida for over 25 years in everything from small powerboats to large cruising catamarans. He currently lives aboard a 38-foot Cabo Rico sailboat with his wife Lucy and adventure dog Chelsea. Together, they cruise between winters in The Bahamas and summers in the Chesapeake Bay.

How To Sail Against The Wind

Sailing against the wind, also known as "beating" or "tacking," can be challenging but it is an important skill for sailors to master.

Being able to sail against the wind means a sailor can sail their boat in most locations in the world.

To sail a sailboat against the wind:

• Check the wind direction
• Tack the boat
• Use the tiller/steering
• Adjust the sails continuously

Following these steps will allow a sailboat to sail windward.

1. Check The Wind Direction

The first step of sailing against the wind direction is the check the exact direction in which the wind is blowing.

To check the direction of the wind:

• Use a wind indicator : Use a wind indicator like an anemometer to measure the exact wind direction
• Check the onboard flag or sails : Look at the sails or flags onboard to get the exact wind direction
• Check the weather forecast : Sailors can check the local weather forecast to get the exact direction the wind is blowing

Sailing against the wind requires a sailor to sail at an angle to the wind so a sailor will need to know the exact direction the wind is coming from to set this angle.

The benefits of checking the wind direction are it will inform the sailor of the exact wind direction so a tacking angle can be set and it will inform the sailor of the wind speed so they will know the force on the sails and keel.

2. Tack The Sailboat

The second step of sailing into the wind is to tack the sailboat, also known as "tacking".

Tacking is a sailing maneuver used to change the direction of a sailboat by turning the bow of the boat through the wind. This is also known as "coming about" or "beating."

When sailing, tacking is used to sail against the wind or to change the direction of the boat when sailing at an angle to the wind.

The tacking sailing maneuver means a sailboat will sail in a zig-zag direction against the wind rather than sailing at a 90-degree angle windward. The zig-zag direction change means the wind will alternate between blowing on the starboard side and blowing on the port side.

For example, if the wind is blowing from the north, tacking would mean sailing the sailboat in the direction between northeast and northwest rather than directly north.

To tack a sailboat:

• Alert the crew : Alert the crew that you're about to tack the sailboat to prepare them to go to a close haul. Close hauled is a sailing term used to describe the point of sail where the boat is sailing as close to the wind as possible. This means that the boat is heading upwind with the sails trimmed in tight and the wind coming from the side of the boat
• Tighten the mainsheet : Tightening the mainsheet is used to adjust the angle of the mainsail in relation to the wind. The mainsheet is the rope that controls the mainsail and it runs from the sail to the aft end of the boat
• Adjust the angle of the sails : Adjust the angle of the sails until the sailboat is sailing at a 45-degree angle against the wind. Sailing at a 45-degree angle to the wind direction will allow the sailboat to sail close-hauled and help it to travel in the direction of the wind without being stopped by the wind forces

The keel of the sailboat will provide stability and prevent the sailboat from capsizing or being blown sideways by the wind. The keel is a heavy, vertical fin-like structure that extends down into the water from the bottom of the sailboat's hull.

As the sailboat moves against the wind through the water at a 45-degree angle, the keel acts as a counterbalance to the force of the wind on the sails, helping to keep the boat upright and on course.

3. Use The Tiller/Steering

The third step of sailing against the wind is to continuously use the tiller/steering on the sailboat. When sailing against the wind, the tiller or steering is an essential tool that the sailor uses to maintain the boat's course and angle to the wind.

Using the tiller/steering system when sailing against the wind will:

• Keep the boat close-hauled : When sailing against the wind, the boat needs to be pointed as close to the wind as possible. This is known as close-hauled sailing. To achieve this, the sailor must use the tiller or steering to keep the boat pointed upwind which helps the boat maintain its course and speed at a 45-degree angle to the wind direction
• Balance the boat : When sailing against the wind, the boat is heeled over to one side as the force of the wind pushes against the sails. The sailor should use the tiller or steering to balance the boat and prevent it from tipping over. This involves making small adjustments to the boat's angle and direction to maintain a stable and controlled sailing posture. The keel will also help with the balance of the boat in the wind
• Maintain forward momentum : Sailing against the wind requires a delicate balance between pointing the boat upwind and maintaining forward momentum. The sailor should use the tiller or steering to maintain the boat's speed and ensure that it is moving steadily forward even when sailing directly into the wind. Getting the right balance between sailing in a zig-zag pattern and maintaining boat speed is crucial

With practice and experience, sailors can become skilled at using the tiller/steering to navigate against the wind and enjoy the unique challenges and rewards of sailing upwind.

When steering the boat against the wind, a sailor should avoid:

• Turning the boat too slowly : When steering the boat against the wind, avoid turning too slowly when tacking as this can cause the sailboat to get caught in irons which can halt any progress when sailing against the wind
• Oversteering : When steering the boat against the wind, avoid steering it too much (oversteering) as this can result in the sailboat not pointing at a 45-degree angle against the wind and instead have the point of sail close reach or broad reach which will halt progress when sailing against the wind
• Tangling the jib sheet : Jib sheets might tangle with some fixtures on the fore deck and will need to be unwrapped. To prevent this from happening, close all fore deck hatches, keep some tension on both jib sheets before and during the tack and clear off any item that may snag the sheets

4. Adjust The Sails Continuously

The fourth step of sailing against the wind is to continuously adjust the sails as the sailboat progresses upwind.

To adjust the sails when sailing against the wind:

• Trim the sails : To sail efficiently upwind, the sails need to be trimmed in tight. This means pulling the mainsail in close to the centerline of the boat and tightening the jib sail to bring it as close to the wind as possible. This will help the boat maintain its course and speed and reduce the amount of sideways drift.
• Watch the telltales : The telltales are small strips of ribbon or yarn that are attached to the sails and help the sailor gauge the airflow across the sail. When sailing against the wind, the telltales on the jib sail should be flowing straight back indicating that the sail is at the proper angle to the wind. If the telltales are fluttering or streaming forward, the sail may need to be adjusted
• Use the boom vang : The boom vang is a line that runs from the bottom of the mast to the boom and helps control the shape of the mainsail. When sailing upwind, the boom vang can be tightened to flatten the mainsail and reduce its draft. This can help the boat sail more efficiently and maintain forward momentum
• Adjust the traveler : The traveler is a device that runs across the cockpit or deck and allows the mainsail to be adjusted from side to side. When sailing upwind, the traveler can be moved windward to help keep the boat on course and maintain a balanced sail plan

Overall, adjusting the sails when sailing against the wind is a delicate balance between maximizing efficiency and maintaining control.

With practice and experience, sailors can learn to adjust the sails to suit the prevailing wind conditions and sail upwind with confidence and skill.

Frequently Asked Questions

Below are the most commonly asked questions about sailing against the wind.

How Long Does It Take To Learn How To Sail Against The Wind?

It will take a beginner sailor 3 to 5 attempts to properly sail a sailboat against the wind without any supervision. The timeframe of this is typically within 1 week of practicing 3 to 5 times. However, some sailors may take longer.

What Are The Forces When Sailing Against The Wind?

When sailing against the wind, there are four forces at play:

• Wind Force : The wind is the primary force that is opposing the motion of the sailboat. As the boat sails into the wind, the wind exerts a force on the sails that resists the forward motion of the boat
• Lift Force : The sails generate lift which is a force that propels the boat forward. When sailing against the wind, the lift force is reduced as the sails are not able to generate as much lift as when sailing with the wind
• Resistance Force : As the boat moves through the water, it creates a resistance force which is the force that opposes the forward motion of the boat. This force is influenced by the shape of the hull, the size of the boat, and the speed of the boat
• Friction Force : The friction between the water and the hull of the boat generates a force that opposes the forward motion of the boat. This force increases as the speed of the boat increases

When sailing against the wind, the opposing forces of wind and resistance become more dominant making it more difficult for the boat to move forward.

Sailors use the tacking technique which involves zigzagging back and forth across the wind to make progress against the wind. This allows the boat to use the lift force of the sails more effectively while minimizing the resistance force.

What Are The Benefits Of Sailing Against The Wind?

The benefits of sailing against the wind are:

• Improved sailing skills : Sailing against the wind requires more skill and technique than sailing with the wind. It can be a great way to improve your sailing skills as you learn how to adjust the sails, steer the boat, and navigate more effectively
• Access to more destinations : When sailing with the wind, a sailor's options for destinations may be limited by the wind direction. However, when sailing against the wind, a sailor can access more destinations that may have been previously out of reach
• Greater control : Sailing against the wind requires more attention and focus but it gives a sailor greater control over the boat. A sailor can fine-tune the sails and the boat's position to optimize the speed and direction without issues or limitations
• Challenge and adventure : Sailing against the wind can be a thrilling and adventurous experience. It requires mental and physical toughness and the satisfaction of successfully navigating against the wind can be very rewarding

Overall, while sailing against the wind may require more effort and skill, it can also provide a unique and exciting sailing experience with its own set of rewards.

What Are The Risks Of Sailing Against The Wind?

The risks of sailing against the wind are:

• Increased risk of capsizing : When sailing against the wind, the boat may be more prone to capsizing due to the combination of wind and waves. The boat may be more difficult to control in these conditions and sailors will need to be prepared for any issues with the sailboat capsizing
• Fatigue and physical strain : Sailing against the wind requires more physical effort and can be more tiring than sailing with the wind. This can lead to fatigue and physical strain which can affect a sailor's ability to navigate safely
• Navigation challenges : Sailing against the wind may require more careful navigation and planning as sailor may need to navigate around obstacles and adjust their course more frequently. This can be challenging especially in unfamiliar waters or adverse weather conditions
• Increased wear and tear on equipment : Sailing against the wind can be more taxing on the sailboat equipment as the sails and rigging are subject to greater stress, force, and strain. This can increase the risk of equipment failure or damage

To mitigate these risks, it is important to be prepared and to have the proper training and experience to handle sailing against the wind. This includes ensuring that the sailboat and equipment are in good condition, understanding the weather and navigation conditions, and taking appropriate safety precautions. It is also important to stay alert and attentive while sailing and to make adjustments as needed to ensure safe navigation.

What Should Be Avoided When Sailing Against The Wind?

When sailing against the wind, sailors should avoid:

• Pinching : Pinching is a term used in sailing to describe the act of sailing too close to the wind. When sailing against the wind, the boat needs to sail at a 45-degree angle to the wind to maintain forward momentum and speed. Sailors should avoid pinching when sailing against the wind
• Sailing in irons : Sailing in irons is when a sailboat is sailing directly against the wind. This will prevent the boat from moving forward against the wind and instead the sail angle will need to be adjusted to close haul to progress further
• Turning too slowly or oversteering : When sailing upwind, avoid turning the sailboat too slow or oversteering it as this can affect the ability of the boat to travel against the wind effectively

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How A Boat Sails Upwind

By: Zeke Quezada, ASA Learn To Sail , Sailing Tips

 A sailor’s life revolves around the wind. Its direction and its strength govern where he can sail, with what degree of difficulty or comfort, and how quickly. Naturally, the language of sailing reflects how sailors orient themselves and everything around them with reference to the wind.

Upwind and Downwind  

The sailor’s world is roughly divided into two hemispheres: upwind and downwind. anywhere or anything in the direction from which the wind is blowing is upwind; anywhere or anything in the direction toward which it’s blowing is downwind. 

When sailing, you trim the sails according to the wind direction relative to the boat. As you learn to sail, the all-important “points of sail” become second nature. When you are out on the water, you’ll be constantly aware of them as the wind changes and as your course changes. You will continually fine-tune the trim of your sails to suit the degree to which you are sailing upwind or downwind. 

By understanding the points of sail and their implications on crew comfort and sail trim, the helmsman and the crew will be able to work together to move the boat efficiently to any destination they choose. 

Sailing Close-hauled  

You sail close-hauled on the very edge of the no-sail-zone — making your best speed toward a destination to windward. This involves a balancing act between boat speed and your course, or angle to the wind. For most boats, that angle is about 45 degrees to the true-wind direction, but it varies with the design of the boat, the shape of the sails (both their geometry and physical condition), and the strength of the wind. 

If you attempt to sail a course above close-hauled, or closer to the wind, the sails will no longer deliver full power and the boat will slow down. Sailing a course below close-hauled (or footing off), would be faster but, if your destination is upwind, you would not be making as much progress toward it. Close-hauled is that happy confluence of speed and course that brings the boat upwind with maximum efficiency. Many sailors find close-hauled the most enjoyable point of sail. The wind (this is the apparent wind, remember) will feel the strongest in the crews faces, while the boat bounces along merrily over the waves (maybe sending a bit of spray-on deck) heeling more than on any other point of sail. All of this adds to the exhilaration and fun of sailing. 

Start on a beam reach and head up about 45 degrees. Concurrently trim the jib sheet tightly (but not rock hard). Trim the mainsail to the point that its luff just stops bubbling. The boom will lie a little off centerline. experiment with small changes to the trim of both sails — it’s a fine art!

Steering is especially important when sailing close-hauled because with the sails pulled in tight there’s no more to trim in. The driver must be constantly adjusting course to any shifts of wind.

Telltales, short dark yarns or nylon strips streaming on the jib a foot or two back from the luff are an excellent closehauled steering aid.

Except in very light winds, when the boat is barely moving, the helmsman, whether using a tiller or a wheel, should always sit on the windward side for visibility and control. When you’re steering just a little too close to the wind, or pinching, the warning signs are obvious: The jib begins to luff at its leading edge, signaling your entry into the no-sail zone. 

When you steer just slightly lower than your optimum close-hauled course, the sails will look full but you are no longer making your best speed to windward. Get in the groove! Concentrate on steering as close to the wind as possible without causing that small luff in the front of the jib with its associated loss of speed.

So now you’re in the groove, but don’t get too comfortable. You’re trying to get to windward, and there’s only one way to get there and that’s by a series of changes in course.

Tacking — Getting From Zig to Zag and Back  

A sailboat cannot make any forward progress directly into the wind. When you tried to sail too close to the wind, the sails simply flapped and you lost headway. You may even have put the boat in irons. To reach a destination directly upwind, you have to sail a zigzag course. each leg of the zigzag will be approximately 45 degrees away from the direct line between your starting point and your destination. Think of climbing up a mountain on a trail with a series of switchbacks. This means at some point, you have to get from your zig course to your zag course, which is on the other side of the no-sail zone.

Tacking Defined

When you turn the boat so that its bow passes entirely through the wind — that is, through the no-sail zone — that’s called tacking. The word tack gets a bit of a workout here, just as you will when you tack the boat. 

When the boat is sailing with the wind blowing on the starboard side, it’s on starboard tack, and when the wind is blowing on the port side, the moving sailboat is on port tack. To reach a destination directly toward the wind, you have to sail, using the steering skills you just learned, part of the way close-hauled on starboard tack and part of the way close-hauled on port tack. To bring the boat from close-hauled on starboard tack to close-hauled on port tack, you must pass through the no-sail zone — you have to tack. 

Tack, Tacking, And Tacks 

Where do the apparently multiple meanings of “tack” come from? An old-time square sail was supported along its top by a horizontal spar, or yard, and had control lines on the bottom two corners. When sailing closehauled, one of those corners was hauled forward and down, and was therefore the tack of the sail, and the other was hauled aft. If the wind was on the starboard side, the starboard corner was the tack — starboard tack. To go from sailing with the wind on the ship’s starboard side to sailing with it on the port side, the crew had to literally change tacks. 

Of course, we also use the term coming about to mean tacking. 

Sailing Upwind

The ability of a modern sailboat to sail close-hauled, sometimes even closer than 40 degrees to the wind’s direction, is due to the boat’s design and the shape of its sails and the forces they generate.

Lift, Drag, and Leeway  

The net sum of the forces in play (sail, keel, and rudder) is the forward motion we enjoy. the wind blowing over the airfoil-shaped sails creates a forward force in the form of aerodynamic lift arising from the pressure difference between the windward and leeward sides of the sails. It also creates the sideways force that causes heeling and, even when the forces are in balance and the boat is steering “straight,” a small amount of leeway. 

The hull and keel resist motion, both forward and sideways, because of their inherent drag, but once moving forward, the keel, because of the leeway, is at an angle to the water flow. In just the same way as the rudder generates lift when turned, the keel generates an additional forward force from its hydrodynamic lift. 

When the forces are balanced, the boat sails in a straight line but with a few degrees of leeway. however, because of the frequent variations in the wind’s strength and the effect of waves on the hull and keel, this balance is hard to achieve simply with sail trim. the rudder provides the turning force that corrects for changes in the balance. 

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How Do Sailboats Work? (The Complete Guide)

Ever wondered how a sailboat moves through the water? If so, you’re in the right place! In this article, we’ll explore the science behind sailboats, from what they are to the parts they use to move.

We’ll uncover the basics of how to angle the sails, the role of the rudder, and safety tips that every sailor should know.

Finally, we’ll dive into the many benefits of sailing, from the joy of exploring the open waters to the feeling of accomplishment when you reach your destination.

So, if you’re ready to discover the wonders of sailboats, let’s get started!

Table of Contents

Short Answer

Sailboats use the power of the wind to propel them forward.

The sails are designed to catch the wind, and as the wind passes through the sails, it creates lift which moves the boat forward.

The sails can be adjusted to different angles to maximize the lift and the direction of the boat.

The rudder is used to steer the boat and the keel helps to keep the boat stable in the water.

What is a Sailboat?

A sailboat is a type of boat that uses sails to propel itself through the water.

The sails are usually made of lightweight, durable fabric, such as nylon or polyester, and are attached to a mast which is mounted on the boat.

The sails are designed to catch the wind, which pushes the boat forward.

The sails can be adjusted and angled in order to capture more or less of the wind, allowing for more efficient movement.

The rudder of the boat is a large fin-like structure located at the back of the boat which is used to steer the boat in the desired direction.

With the right skills and understanding of how sailboats work , anyone can enjoy the thrill of sailing.

How Does a Sailboat Work?

Sailboats use the power of the wind to move through the water, allowing them to be an efficient and eco-friendly way to explore the open seas.

In order to understand how sailboats work, its important to understand the parts that make up a sailboat and how they interact with the wind.

The most important part of a sailboat is the sail, which is typically made of lightweight and durable fabric.

The sail is held up by a mast attached to the boat, and it is designed to capture the wind and use it to push the boat forward.

The sail is able to capture more wind when it is angled in a certain direction, allowing it to move faster and more efficiently.

In addition to the sail, sailboats also have a rudder that helps steer the boat in a desired direction.

The rudder works in conjunction with the sail to allow for precise maneuvering of the boat in any direction.

The rudder is typically located behind the boat and is made of a solid material like wood or metal.

Another important part of a sailboat is the keel, which is a fin-like structure that is attached to the bottom of the boat.

The keel helps stabilize the boat and keep it upright in the water.

It also helps the boat stay in a straight line when sailing in a straight direction.

Finally, the sailboat must have a rigging system, which is made up of ropes and lines that are used to control the sails.

The rigging system is used to adjust the angle of the sail to capture the most amount of wind and move the boat forward.

With the right knowledge and understanding of how sailboats work, anyone can enjoy the thrill of sailing.

Understanding how to use the sails, the keel, the rudder, and the rigging system together will help you become an expert sailboat captain in no time.

The Parts of the Sailboat

Sailboats are propelled by the force of wind on their sails, and the most important part of the sailboat is the sail itself.

The sails are typically made of lightweight, durable fabric and are held up by a mast attached to the boat.

The angle of the sail is what captures the wind, allowing for more efficient movement.

The rudder of the boat helps steer it in the desired direction, working in conjunction with the sails to allow for precise maneuvering.

In addition to the sail and mast, the sailboat also contains a boom, which helps hold the sail out when the wind is blowing.

The boom is connected to the mast and can be adjusted to control the angle of the sail.

Additionally, the sailboat features a keel, which is a fin-like structure that helps keep the boat stable and upright in the water.

The keel also helps the boat move in a straight line when the wind is blowing.

Lastly, the sailboat features a tiller, which is the handle used to steer the rudder.

These are the key parts of a sailboat that allow it to move through the water.

How to Angle the Sails

Angling the sails is an essential part of sailing a boat effectively.

By adjusting the angle of the sails in relation to the wind, you can capture more of the winds power to propel the boat forward.

To angle the sails correctly, the sailor must first identify the direction of the wind.

This can be done by feeling the air on their face, or by looking for telltale signs like rippling water or flags flapping in the wind.

Once the wind direction is known, the sailor must adjust the angle of the sails so that they will catch more of the winds power and propel the boat forward.

The most efficient angle for the sails depends on the type of boat and the strength of the wind, but in general, the sails should be angled so they are at a 45-degree angle to the wind.

This allows the sails to catch the most wind and propel the boat forward with the most efficiency.

It is also important to make sure that the sails are not too close to the boat, as this can cause them to lose their shape and be less effective.

In addition to angling the sails correctly, the sailor must also be aware of the wind speed and direction.

As the wind speed and direction change, the sailor must adjust the angle of the sails in order to stay on course and maintain the most efficient angle for catching the wind.

By making small adjustments to the sails angle, the sailor can keep the boat moving in the desired direction and maintain the most efficient speed.

Sailors must also be aware of how their body weight can affect the angle of the sails.

If the sailor leans too far to one side of the boat, the angle of the sails will be affected.

This can result in the boat veering off course or the sails not catching the wind efficiently.

To prevent this, the sailor must be aware of their body weight and be mindful of how it affects the sails.

By understanding and being aware of how to angle the sails correctly, sailors can ensure that they are using the power of the wind to propel their boat forward efficiently.

With practice and experience, anyone can become a skilled sailor and enjoy the thrill of sailing.

The Role of the Rudder

The role of the rudder on a sailboat is essential for steering and maneuvering the boat in the desired direction.

The rudder is typically located at the stern of the boat and is a flat piece of metal or wood that is connected to the hull and runs along the bottom of the boat.

By changing the angle of the rudder relative to the hull, the boat can be steered in the desired direction.

When the rudder is angled to the left, the boat will turn to the left and when the rudder is angled to the right, the boat will turn to the right.

The rudder is also used to keep the boat on a straight course when sailing in strong winds.

By angling the rudder slightly, it helps to create a drag on one side of the boat and a lift on the other side, allowing for greater control and stability in high winds.

In addition to the rudder, sails can also be angled to help turn the boat in the desired direction.

Together, the sails and the rudder work together to help the sailor steer and maneuver the boat in the desired direction.

Safety Tips for Sailing

Sailing is a popular recreational activity, but it can also be dangerous if not practiced safely.

Before setting sail, it is important to be aware of some key safety tips that will help you enjoy your sailing experience without any hiccups.

First, make sure you have the proper safety equipment onboard.

This includes life jackets, flares, a first-aid kit, and a fire extinguisher.

It is also a good idea to carry a radio or GPS device onboard in case of emergency.

Additionally, make sure that the boat has been inspected and is in good working condition before leaving the dock.

It is also important to check the weather before setting sail.

Make sure you are aware of any storms or other hazardous conditions that may be in the forecast.

Make sure to also check the tide and wind conditions before leaving, as these can greatly affect your course and speed.

It is important to wear the proper clothing when sailing.

Choose clothing that is lightweight, breathable, and waterproof.

Make sure to also bring a hat or visor and sunscreen to protect yourself from the sun’s rays.

Additionally, make sure you have plenty of food and water onboard in case of emergency.

Finally, make sure you have a good understanding of the sailing basics, such as sailing terms, the parts of the boat, and how to properly sail.

Knowing these basics, as well as the local rules and regulations, will help ensure a safe and enjoyable sailing experience.

By following these safety tips, you can ensure that your sailing experience is a safe and enjoyable one.

Be sure to always practice good safety habits and use common sense when out on the water.

With the proper preparation and knowledge, sailing can be a fun and enjoyable experience.

The Benefits of Sailing

Sailing is an activity that can provide countless benefits to those who take part in it.

Not only can it be great fun, but it can also be a great way to relax and get away from the hustle and bustle of everyday life.

Sailing can also increase physical and mental wellbeing, as it provides an opportunity to be out in nature and enjoy the fresh air.

Additionally, sailing can help improve coordination, balance, and focus, as well as provide a unique way to explore the world.

It can also be a great way to build self-confidence, as mastering the art of sailing requires skill and determination.

Finally, sailing can be a great form of exercise, as it can help improve endurance, strength, and flexibility.

All these benefits make sailing a great activity for anyone looking to enjoy the outdoors and have a memorable experience.

Final Thoughts

Sailboats are a fantastic way to enjoy the outdoors and even take part in competitive sailing events.

With the right knowledge of how sailboats work, anyone can get out on the water and enjoy the thrill of sailing.

From understanding the parts of a sailboat to how the sails and rudder work together, sailing is a skill that can be easily learned.

With all the benefits of sailing, it’s an activity that’s sure to bring plenty of fun and memories.

So, what are you waiting for? Get out on the water and experience the magic of sailing!

James Frami

At the age of 15, he and four other friends from his neighborhood constructed their first boat. He has been sailing for almost 30 years and has a wealth of knowledge that he wants to share with others.

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The 6 Points of Sail: An Illustrated Guide

Depending on the direction of the wind and where you’d like to take your sailboat, you’ll need to consider which point of sail to be in. Whether you’re sailing upwind (windward) or sailing downwind (leeward), your sails will either take on the characteristics of an airplane wing or a parachute.

So what are the points of sail on a sailboat? The points of sail include into the wind (in irons), close hauled, close reach, beam reach, broad reach, and running, which go from windward to leeward and are all symmetric from port to starboard.

Knowing the points of sail on a sailboat is important in terms of being knowledgeable about how your sailboat generates wind power while also being able to properly communicate with your crew.

It’s also important to understand the difference between upwind sailing and downwind sailing.

There’s a lot of sailing terminology to hash out here as well, so let’s dive into all the different points of sail and learn what they all really mean.

Points of Sail

A point of sail is the direction of a sailboat’s journey while taking into consideration the direction of the true wind as opposed to apparent wind.

The difference between true wind and apparent wind is that true wind is the wind that’s felt by something or someone in one place (like on land) while apparent wind is the wind felt when on the move (like on a sailboat).

The points of sail, when combined, complete a full 360 degrees. Starting from the top (0 degrees) all the way to the bottom (180 degrees), we’ll now explore the different points of sails.

1. Into the Wind (In Irons)

Being into the wind or in irons means your sailboat is going straight into the wind (plus or minus 45 degrees from 0), which will prevent your sailboat from… sailing!

Being into the wind can’t be 100% avoided, and it shouldn’t be, but it’s generally not where you want to be if you plan on moving.

The into the wind point of sail is more often a pivot point for when performing other sailing actions including tacking as well as raising and lowering the mast.

When tacking, your point of sail will change from one side of the sailboat to another while crossing the into the wind point of sail. If you’re not able to cross this point of sail fast enough and get stuck, this is called being “taken aback”.

This is also considered the “no-go zone” or “no sail zone” because, you guessed it, you won’t be going anywhere fast when in this space for too long.

If your sailboat’s in the into the wind point of sail for a long enough time, your sailboat will lose all forward momentum and end up sitting around.

2. Close Hauled

The close hauled point of sail is a tad bit greater than the 45-degree mark on either side of the sailboat.

When at this point of sail, you’ll sail upwind and is often called “beating” as well as “working windward” since your boat is moving toward the wind. Sailing close hauled means you’ll be feeling the wind much more as a captain and crew member!

While sailing close hauled, your sail will be functioning as similar as it can to a wing on an airplane due to it cutting the wind dead on resulting in generating a lot of life.

As a matter of fact, this is when you’ll have the tightest sail trim. The closer you are to the wind (or the “no-go zone”), the more to “point” your sailboat will be.

3. Close Reach

As your sailboat “bears away” (moves away from the wind), it’ll enter the close reach point of sail. This point of sail sits right in between the close hauled and beam reach points of sail on either the port or starboard side of a sailboat. Close reach is a fun and fast point of sail for many sailors!

Close reach is the closest point of sail to the “no-go zone” as any other point of sail, so it’s important to pay attention to the wind and your boat sails.

Since sail trim is so important when it comes to your sailboats speed, it’s important in a close haul to keep your sail tight (similar to a close hauled point of sail) but loose enough so it’s just on the verge of luffing.

4. Beam Reach

When entering a beam reach point of sail, your sailboat will be perpendicular to the wind either on the starboard or port side.

Being in beam reach means you’ll be letting your sails halfway out and you’ll be moving relatively faster than other points of sail. As a matter of fact, it’s known to be the fastest point of sail when on a sailboat!

Not only is beam reach the fastest point of sail on a sailboat, but it’s also the most comfortable due to having more control.

The way in which the wind hits your sails at this point of sail means your boat will be transferring energy more efficiently from the sideways force of the wind to the propelling motion forward.

5. Broad Reach

Moving away from a beam reach and into a broad reach point of sail results in letting your sails out about 2/3 of the way.

At this point of sail, the wind is not coming astern from your sailboat and your sail will act more like a parachute than a wing. Now that you’re sailboat’s heading downwind, you’ll also feel a little less of a windy feel but still should be chugging right along.

Since a sail will be out almost the entire way when in a broad reach point of sail, it’ll start to feel like you’re going downhill when it comes to the wind.

While your sailboat won’t yet be truly going entirely downwind, you’ll be on the verge of entering it.

While not the fastest point of sail, I’m a personal fan of broad reach since we’re going at a decent speed and it feels much calmer (in terms of the wind speed) than more windward points of sail.

When you let your sails out the most they can go and the wind is coming directly behind your sailboat, you’ll sail downwind and you’re definitely on a running point of sail.

This point of sail can truly feel like you’re running downhill since you have the force of the wind directly propelling you and your sailboat forward. As a matter of fact, it acts a lot like a parachute and really feels great!

Also known as a “dead run”, the running point of sail doesn’t require critical attention to be made on the sail trim.

Depending on the strength of the wind speed, this means you can consider putting up a genoa or spinnaker sail to really get your sailboat moving when sailing directly downwind.

If you feel that the wind is fairly constant in terms of direction and intensity, this is a great time to put those massive colorful sails up!

How a Sail Works

When I first learned how to sail, I thought the sail was always acting kind of like a kite and simply floating across the water. Well, it turns out that it’s a little more complicated and interesting than that!

As I mentioned before, the sail can act in two different ways: as a wing and as a parachute.

When in the close hauled, close reach, and partially the beam reach points of sail your sailboat’s sail is acting a lot like a wing .

Based on the magnitude and angle at which the true wind and sailboat are traveling, the combination of the two will produce an apparent wind force.

The transfer of energy to produce a forward moving force is mainly due to the sail, keel, and hull .

Essentially, the sail catches the wind’s energy forcing the sailboat to tilt to the side followed by resistance to this tilting from the keel allowing the hull to effectively cut through the water with the remaining force.

When in the broad reach and running points of sail, these forces are still at play resulting in a wing-like action, however, in these points of sail the true wind and sailboat forces are much more aligned.

Essentially, this produces more of a parachute effect as opposed to a wing since the apparent wind force is indistinguishable from the other forces.

Related Questions

What is the best point of sail? The best point of sail is based on personal preference, but the fastest and most comfortable point of sail is beam reach. The combination of the lateral force from the wind onto the sail and the resisting force from the keel produces the strongest forward-moving force on a sailboat.

What is the difference between a jib and genoa sail? Both a jib and genoa sail are sails hoisted at the fore of a sailboat with the genoa being larger in size. The genoa sail oftentimes overlaps the mast due to its size and is mainly used when in a running point of sail.

How do you turn a sailboat? Turning a sailboat occurs when performing a tack or jibe (gybe). Tacking happens when a sailboat is turning into the wind, which requires a traversal through the “no-go zone”. Conversely, jibing happens when traversing through the running point of sail.

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Sailing Explained: How to Sail Against the Wind

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Last Updated on September 18, 2023 by Boatsetter Team

Sailing is a beautiful and majestic sport. It’s pretty clear how a boat sails downwind with the breeze pushing against the sails, but have you ever wondered: how do you sail against the wind?

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Sailing is about aerodynamics & hydrodynamics

The aerodynamics is how wind acts on the sails, and the hydrodynamics is how forward motion is created with the help of underwater lateral resistance. Sails are basically airplane wings set on end. As the wind comes in contact with the forward end of the curved foil (the luff of the sail) it splits, passing on both the downwind (leeward) and upwind (windward) sides.

The wind on the leeward side travels a longer distance due to the curvature of the sail and creates a low-pressure area, while the wind on the windward side travels a shorter distance and reaches the aft end faster. The combination creates an aerodynamic lift that “pulls” or “sucks” the boat forward.

That’s only half the equation: pressure in the sails will still push the boat more sideways than pull it forward. That’s where the keel or centerboard below the waterline comes into play by transferring sideways pressure into forward momentum.

With the lift of the sails and the lateral push or hydrodynamics of the keel, upwind sailing is achieved. Where the wind concentrates its force in the sails is called the center of effort while the keel below is called the center of lateral resistance.

READ MORE: 7 Best Sailboat Accessories

No, boats cannot sail directly into the wind

Instead, they make progress toward an upwind mark by sailing at angles, which are called “points of sail.” Close hauled is roughly 45 degrees off the true breeze, a close reach is 60 degrees, and a beam reach is at 90 degrees. When sailing lower (greater degrees) than a beam reach, you’re no longer sailing upwind.

If the bow faces directly into the wind, the boat cannot make forward progress and is said to be “in irons.” When sailing very close to the wind direction, a boat is said to be “pinching” or “beating” which isn’t a very efficient way to sail.

Changing direction when sailing upwind is called “tacking” and it’s when the bow of the boat is brought through the eye of the wind. Turning upwind is called “heading up” and turning downwind is “falling off.” When the wind first passes over the starboard rail, you’re on a starboard tack and vice versa.

Boats sail in true wind, which is the breeze that’s actually blowing at a given speed and angle. However, the boat is actually responding to the apparent wind, which is the angle and speed of the breeze that is felt on a moving vessel.

Upwind sailing is a craft

While the basics of upwind sailing are simple, it can take years to master the nuances of sail trim (moving sails in and out) and sail shape (making other adjustments to change the way the wind affects the sail). The sails are sheeted in (made flatter) by pulling in the sheeting lines or loosened to create a “belly” or depth in the sail.

Pro tip: At age 16, Jessica Watson became the youngest person to sail around the world without stopping and without assistance. Talk about inspiration!

Sheeting in (bringing the sails closer to the centerline) enables the boat to point higher (sail closer to the true wind) while easing out (loosening the aft end of the sail) creates more power. If a sail begins to luff or flutter when sailing upwind, it needs to either be trimmed in or the boat must change direction and fall off the wind to get more efficient airflow over the foils.

Learning on a small sailboat is ideal as they react immediately to changing conditions, so you learn the cause and effect of your actions on sail trim. The theory is easy. The actual practice takes years to perfect, and it’s what separates good sailors from newbies.

Once you have it down, you can (eventually) sail or zig-zag your way to just about anywhere. Perhaps then you can charter a larger boat from a peer-to-peer rental service like Boatsetter and explore new watery horizons.

Sailor, there’s more where that came from:

• 10 Best Beginner Sailboats  
• Types of Sailboats  
• Do Sailboats Have Motors?
• Sailing, Destinations, & Boating Basics: Explore the Boatsetter blog

Boatsetter is a unique boat-sharing platform that gives everyone— whether you own a boat or you’re just renting — the chance to experience life on the water. You can list a boat , book a boat , or make money as a captain .

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Zuzana Prochazka is an award-winning freelance journalist and photographer with regular contributions to more than a dozen sailing and powerboating magazines and online publications including Southern Boating, SEA, Latitudes & Attitudes and SAIL. She is SAIL magazines Charter Editor and the Executive Director of Boating Writers International. Zuzana serves as judge for SAIL’s Best Boats awards and for Europe’s Best of Boats in Berlin. 

A USCG 100 Ton Master, Zuzana founded and manages a flotilla charter organization called Zescapes that takes guests adventure sailing at destinations worldwide. 

Zuzana has lived in Europe, Africa and the United States and has traveled extensively in South America, the islands of the South Pacific and Mexico. 

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How To Sail Against The Wind

Efficiently being able to sail against the wind takes more practice and skill than any other sailing endeavor. Doing this well will enable you to sail anywhere.

Powered only by the wind, it seems intuitive that sailboats can easily travel with the wind behind them. However, when it is time to turn the other way and go home, it may seem impossible to sail home with the wind blowing straight against your boat.

Table of contents

But it is possible for this movement to become reversed because the sail of a moving sailboat is shaped like an airfoil like an airplane's wing.

When the air moves over the wing of a plane from the front and going backward, the wind that flows over the wing's top has to travel farther than the wind that flows beneath the bottom surface of the wing. This creates a difference in pressure to lift the airplane.

On sailboats, the wind that blows at an angle against the boat inflates the sail. It forms a foil shape similar to the airplane. It creates a pressure difference pushing the sail perpendicular to the direction of the wind.

Sailing Windward

The force from the foil shape of the sail is balanced and combined with other forces including the keep of the boat. The keel is the thin, long piece jutting down from the boat bottom.

From the water, the forces of drag simultaneous with wind pressure against the sail pushes the craft onwards. It moves at angles opposite the wind direction. in sailing terminology, this is called windward.

The keel is of particular importance because without its balance action. boats would drift simply downwind. Sailing windward won't work either if boats are directly pointed opposite the direction of the wind. Instead, the wind has to move against the boat at angles of about forty degrees for many sailboats.

When you angle your sailboat too sharply into the wind will cause the forces on the craft to become imbalanced. When this happens, the boat will then move sidewards into the water.

It is possible to sail against the wind when your sailboat's sail is slightly angled in a direction that is more forward than the force of the sail. The boat can then move forward in this aspect because the centerline or the keel of the boat does to the water what the sail is doing to the wind.

The sail's force keeps its balance by the keel's force. This keeps the boat from moving into the sail force's direction. A proper angle of attack moves the boat forward even if the total force of the sail is to the side when the boat sails into the wind.

In other words, when the sail is angled away from the hull's centerline, the more the force is pointing forward rather than pointing to the side. When you combine the forward force's slight adjustment with the water's opposition to the air, the boat can then shoot windward because you have found a way to sail a course of least resistance against the wind.

A sailboat sailing against the wind will turn through the point on each tack. This is the point in which the boat is neither on the starboard tack or the port tack and is directly headed against the wind.

On the other hand, boats are not able to sail directly against the wind. Thus, f a boat heads into the wind it is said to be "in irons" when it loses steerage. For this reason, a boat sailing against the wind is sailing with the sails trimmed tightly, also known as sailing "close-hauled."

When it comes to how to sail against the wind, keep in mind that when a sailboat sails too close to the wind, or with an angle too small to the wind, the term is called "pinching." This is also a phrase used in colloquial expression that means "recklessness."

To reach its target, sailors that intend to travel windward to a point in line with the exact wind direction will need to zig-zag in order to reach its destination. This technique is tacking. Sailors can reach a point in any direction using the technique of tacking and traveling at angles closest to the wind direction.

Sailing against the wind in practice is usually achieved at a course of and angle of around forty-five degrees to the oncoming wind. To reach specific points, alternating the wind's direction between the starboard and the port is sometimes necessary. The term for this is "tacking."

Tacking is when a yacht or a sailboat sail against the wind. Counterintuitively, this means that compared to having a weak wind behind you, it is always better to have the strong wind in the direction opposite your craft. Having no wind is the worst-case scenario. Think of vectors.

The wind generates forces against the boat's hull through the momentum change that the sails cause. The force goes both towards the direction of where you are going and perpendicular to the motion. The keel takes up the perpendicular force and leans the yacht. Motion is then created by the remaining forward vector.

If your destination is located upwind, how are you going to sail there? Because of the lift created by wind blowing across and not against them, the sails propel the boat forward. This happens unless the wind blows from directly over the back of the boat (astern).

As you begin steering in the direction of the wind, you trim the sails tighter in and keep them full, so that lift is continuously generated. However, sailing too close to the sail and wind will "luff."

This means the edge of the forward sail begins to flutter inwards and outwards and the boat slows down. If you begin turning more into the wind, the whole sail will soon be flapping like a king-sized bedsheet you hung out to dry.

However, don't stop turning into the wind and you will soon see the sail filling on the other side of the boat. This is called tacking and the scientific reasons are explained as you read further down.

Sailboats made today can sail up to around a forty-five-degree angle against the wind. For example, if the north wind is blowing into your sail, the boat can sail on a port tack about the northeast.

The boat can sail all the way through to northwest, west, south, and east on the starboard tack, or wind coming from the boat's right side. Port tack means that the wind comes over the left side of the port. Tack means which side of the boat the wind blows from.

Even if you can't sail your boat literally directly into the wind, sailors call this tacking or beating to windward. You will find that on the newer tack, you sail in the direction that's at about right angles to the old tack. This occurs with the wind still at about forty-five degrees but this time on the other side. The zig-zagging and the repeated tack will move the boat upwind.

You can learn more about tacking a sailboat here .

Four Forces

Four forces act on a sailboat trying to sail against the wind. The two that directly affect the boat are the viscosity force of the water and the force of the wind, which propels the boat.

The water's viscosity slows down the boat and helps her keep on-course. The remaining two forces are buoyancy and gravity. Buoyancy pulls up the sailboat and gravity pulls her down. All of these forces keep the boat afloat as it sails against the wind.

The combined effect of the water and the wind is a net force pushing the boat diagonally against the wind. The resistance of the water combined with the force of the wind determines the direction in which a sailboat sails. On the sail, the force exerted by the wind has two components:

• The lift component pushing the sail into the wind perpendicularly.
• The drag component pushing the sail into the direction of the wind.

Because of the lift, the direction of the wind-force varies from the direction in which the wind blows. The angle between the wind and the sail shape of the sail will determine what direction the wind force goes.

The forward motion of the boat and her slippage sidewise slows down due to water resistance. For boats to sail against the wind diagonally, the sidewise slippage needs to be minimal compared to the motion forward. Sidewise slippage is significantly reduced with the keel.

If a keel somewhat eliminates the sidewise slippage, sailboats can only move in the keel's direction. This is also the direction of the sailboat's centerline. Whenever the wind-force total diagonally points forward in relation to the keel, the boat will then move forward in the keel's direction.

If the keel is pointing diagonally into the wind, and the wind-force diagonally points forwards, the boat will then diagonally sail into the wind.

On the other hand, the boat won't be able to diagonally sail into the wind if the sidewise slippage is too big. Just like everything else, sailing against the wind takes practice. Master this and you can sail yourself anywhere in the world and through anything.

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Daniel Wade

I've personally had thousands of questions about sailing and sailboats over the years. As I learn and experience sailing, and the community, I share the answers that work and make sense to me, here on Life of Sailing.

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Sailing (Directly) Into The Wind

Humans have been sailing various seas and oceans for thousands of years, and using boats for potentially even longer than that. But as a species we wouldn’t have made it very far if it was only possible to sail in the same direction the wind is blowing. There are a number of methods for sailing upwind, but generally only up to a certain angle. [rctestflight] wondered if there was some way of sailing straight upwind instead and built this rotary sail craft to test the idea .

Normally a boat sailing upwind will sail approximately 45° into it, then “tack” 90 ° across the wind until they’re at another 45° angle from the wind, this time facing the opposite direction. This back-and-forth nature is not the most efficient path, so this vessel uses a few propellers to bypass the traditional sail. The first iteration, built on a sleek catamaran hull, uses a large propeller to catch the wind’s energy, then transfers it mechanically through a set of shafts to an underwater prop.

It took a few tries to get the size and pitch of both propellers narrowed down to where the boat would move forward into the wind, but move it does. A second major iteration of the build uses a single shaft with no gears, with the trade-off that neither propeller is facing an ideal direction, but this has the added benefit of the boat naturally pointing itself upwind.

While none of the designs are speed demons, the concept is sound enough. It’s just that, in most cases, performing multiple tacks to get upwind is acceptable compared to the extreme efficiency losses and drag from propeller-driven sailing crafts like these. A more effective way of propelling a boat upwind, at least using modern technology, might be to trade sails for solar panels .

22 thoughts on “ Sailing (Directly) Into The Wind ”

This has been done on full sized sailing boats since the early 1970s.

Also there is an international student competition every year for over a decade driving races with this principle. On street and wheels, but physics are the same …

https://www.racingaeolus.org/History.html

>> On street and wheels, but physics are the same …

Sort of. the street doesn’t slip away sideways when you press against it, and you won’t usually drift with the wind unless your tires are *really* slick.

I told him…hehehe… we already got one

Yes, My friend Jim Bates did exactly that.

https://youtu.be/_YZO5i6DysM?si=ke-SLiS78VbismCh

I was also featured on the boat in WaterWorld.

The rudder works by bending the water flowing past it. If you put the rudder right behind the propeller instead of 50 cm behind it, the rudder would work on the speedy water from the propeller.

Also, a longer rudder (as in, horizontally) works better at low speeds.

So, it’s not sailing, really, it’s using the wind to power a propeller instead of an engine.

Eh. Using solely wind power to drive the craft (by whatever means) works w ought for me to call it sailing. I mean. Some America’s Cup type foiling cats don’t even have a “sail” as much as a rigid moveable wing. Still counts imo

All sails are wings.

The that makes sailing SAILING is using the air to directly provide impulse.

If the sail itself isn’t pushing the boat, it isn’t sailing.

Not a new concept I think? Fairly sure I’ve seen a full size (30ft yacht) using wind vane. But while being hit on the head by the boom in a conventional boat is bad enough – the hazard from spinning rotor blades seems considerably worse!

Previously patented? https://www.change-climate.com/Transport_Land_Sea_Sustainable/Assisted_Ships_Sails_Solar_Projects_Marine_Pollution/Rotary_Sails_Powered_Sailing_Boats_Ships_Turbines_Wind_Cars.htm

Even earlier patent from 1992, originally applied in 1989.

https://patentimages.storage.googleapis.com/c8/b1/a2/0799c75948ab7a/FI86831B.pdf

Apparently the turbine could swivel around 360 degrees and the boat would go in every direction regardless of wind direction.

https://sndp.mediadelivery.fi/img/1920/200597500.jpg

What’s missing is the pure joy of sailing!

Easily replicated by burning $100 bills while taking ice cold shower.

We have been keepiing a mini-cruising sailboat at a club, and sailing lots, for several years now, at a total cost of about 2 takeout coffees a day. No ascot required.

2 takeout coffees? So $30-$50?

>might be to trade sails for solar panels

Or trade sails for an internal combustion engine.

That’s crazy talk. They’d need huge amounts of fuel, where is going to come from? The distribution network isn’t ready for it. It’ll never have the range needed for long trips. And what about the fire risk? So dangerous.

It will never catch on.

(caution: may contain traces of sarcasm)

Reminded me of a similar kind of question, sailing faster than the wind. The guy basically set up three rotating sails (a propeller) which were angled so they were permanently “tacked into” the wind, then set up a cart and off it went! https://www.youtube.com/watch?v=jyQwgBAaBag

RCtest flight produced an interesting youtube video having been inspired by the work of Peter Worsley (who he mentions) at http://www.sailwings.net/rotaryhome.html – it would have been better if he had followed more closely the designs shown on that page and he would have got a much better performance of the upwind boat. He took onboard the point about the angle of the windblades being best at 45 degrees. But if that angle is used you need to cover the rotor disk with more blades (minimum 6) – this should have been pointed out on the Peter Worsley website but unfortunately was not made clear. So the areas of his blades are woefully small and that accounts for the poor performance, in fact it is surprising that his design worked at all. He assumes that that addition of mechanical complexity on these craft would amount to reduced performance over a traditional style sailboat. His conclusions are wrong because the direct upwind rotary sailing boat has several advantages. Firstly it can sail directly to a direct upwind destination but the sailing yacht needs to sail a further distance. Secondly, you need to take into account the effect of leverage. If one of the wind rotor blades moves a certain distance, it can be geared to the boat in such a way that the boat would move a smaller distance, and then the effect of leverage comes into play and you get more force. Lastly, there seems to be some confusion over the word “propeller” – this word (as is evident) is for something that “propels” not something that collects energy which is the opposite. So just to make it clear a “propeller” propels and and a “turbine” or “Windmill” collects energy. To refer to the wind rotor as a “propeller” is wrong.

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An up-close look at Vineyard Wind, the nation's largest offshore wind project

The nation’s largest offshore wind energy project is not easy to get a good look at. Vineyard Wind is 15 miles off Martha’s Vineyard and Nantucket. The project is still under construction, but began delivering power in January.

GBH’s Craig LeMoult managed to get on a boat and see the project up close on Monday, and joined All Things Considered guest host Judie Yuill to describe what he saw. What follows is a lightly edited transcript.

Judie Yuill: First of all, how is it that you made it out to the Vineyard Wind site yesterday?

Craig LeMoult: I was one of about 15 journalists from public media stations that got to be on a boat that was chartered by a partnership the stations are involved in called the New England News Collaborative . There were also several experts on board to offer their insights on what we were seeing. We left from Falmouth yesterday morning and it took about 2 hours to motor out to the Vineyard Wind project, which is 35 miles off the mainland.

Yuill: And you were able to get up close to the turbines?

LeMoult: Yeah, the boat was able to go in between the turbines, some of which are done, some are still under construction. When it’s all done, this project will have 62 turbines, and the foundations have all been put in, but about half of them are completed at this point.

Yuill: So what was it like?

LeMoult: The thing that’s really just striking is the size of these things. One of the experts on board was Sanjay Arwade , who teaches about wind turbines like this as a Civil Engineering professor at UMass Amherst’s Wind Energy Center. But he’d never seen a project like this in person until yesterday.

Sanjay Arwade [prerecorded]: “So, I mean, by far the word that is in my mind is scale. It just — it’s just so giant.”

LeMoult: The turbines are 853 feet tall, nearly 3 Statues of Liberty. And that’s just what you see above the water. Of course they continue underwater and are hammered down into the sea bed below. And the three blades are over 350 feet long. They’re arranged neatly in rows, with about a nautical mile between them. When you’re out there on the water, a mile doesn’t actually feel all that far.

Yuill: And this is the project where a turbine blade collapsed in July.

LeMoult: That’s right, one of those huge blades failed, sending debris washing ashore on Nantucket and the Cape. The blades are made by the company GE Vernova and the cause of the incident is being investigated. They’ve resumed some construction of turbines, but for now, they’ve suspended power generation at the project, which means the turbines weren’t spinning when we were out there yesterday.

Yuill: Despite that setback, there’s a lot of hope about the promise of this project, right?

LeMoult: For sure. One of the experts on the boat yesterday was Amber Hewett , who is senior director for offshore wind energy at the National Wildlife Federation. She was seeing the turbines for the first time, too, and said she was emotional.

Amber Hewett [prerecorded]: I’m from Massachusetts, so I think that’s probably where the emotion comes from. A little bit of pride, a little bit of 'finally.’ Massachusetts has been trying to make offshore wind happen for over 20 years. We’ve endured setback after setback after setback. The developers of this project had to persist through the Trump administration, through almost not getting their federal permits, and really just stuck to it relentlessly, until we could be here in this moment.

Yuill: At the same time, there are some real concerns about the potential environmental impacts of projects like this, right?

LeMoult: That’s true. One concern is whether there could be an impact on species like the North Atlantic Right Whale . There are only about 360 known right whales still alive, so any impact on them could be significant. One of the people on board yesterday was Michael Moore of the Woods Hole Oceanographic Institute, who’s a real expert on right whales. He said one thing they don’t know is to what extent harvesting energy from the wind might change conditions in the water for copepods - which are the tiny crustaceans that right whales feed on.

Michael Moore [prerecorded]: We don’t know. But the suspicion is that the changes that it could be bringing about are of a much smaller scale than the current dynamic changes that are going on through climate change. And so every year these systems look differently. And in so doing, it’s hard to get a sense of how that could be an impact.

LeMoult: Moore said a bigger concern than the operation of wind farms is the impact of their construction - especially the vessel traffic and the sound of driving those pylons into the sea floor. He said there are precautions being taken to do that kind of work when right whales are not believed to be nearby. But he acknowledged there are a lot of open questions.

Yuill: This is just one wind farm. What’s the expectation looking into the future about how much more we can expect offshore?

LeMoult: Yeah, the expectation is this is really just the beginning. You know, Amber Hewett noted earlier that Vineyard Wind persisted through the Trump presidency and Trump has been famously hostile to wind energy. So the outcome of the current presidential election could dictate the pace at which wind power moves forward. But the UMass civil engineer, Sanjay Arwade seemed confident wind power will continue to progress, regardless of that election’s outcome. At one point, he offered his vision of what he expects to see by 2050.

Arwade: What I would expect to see at that point is dozens of individual projects, dozens of wind farms and thousands of individual turbines along the coast, let’s say from Virginia to Maine, all of which are generating power and sending it to the onshore grid and powering homes with no emissions.

LeMoult: Just yesterday, the federal department of the interior announced it will hold an offshore wind energy lease sale in October for eight areas on the Outer Continental Shelf in the Gulf of Maine, including off Massachusetts.

And it’s going to be interesting to see if this burgeoning industry grows the economy here in the state. Last month , there was a groundbreaking in Salem for a new offshore wind terminal . Notably, that new terminal will be at former the site of the Brayton Point coal-fired power plant.

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