FOIL
The foil’s task is to create lift that lifts the board and the surfer off the water. As the surfer “flies” in the air, the foil carries all the weight. For this reason, the structure of the foil must be extremely stiff and durable, but at the same time as slim as possible, so that the foil slides in the water with minimal resistance.
Parts of the Foil
The hydrofoil consists of four parts. The mast is the vertical shaft that attaches the foil (the lift-generating part resembling an airplane) to the bottom of the surfboard. The airplane-like part consists of a front wing, a fuselage, and a rear wing or stabilizer.
Usually, the front and rear wings and the fuselage are separate parts that are connected to each other with screw joints. There are also foils in which all of the above are one and the same carbon fiber structure.
Materials
The manufacturing materials for the front and back wings are carbon fiber or a mixture of carbon and glass fiber. The fuselage and mast can be made of aluminum or carbon fiber.
Aluminum is a significantly cheaper material than carbon fiber in terms of both material cost and manufacturing techniques. As a result, the masts and fuselages of beginner and freeride foils are often made of aluminum. Aluminum works well for this purpose, and the differences compared to carbon fiber foils are relatively small. Aluminum foils are usually slightly heavier and slower. Carbon fiber masts and fuselages can be designed and manufactured thinner and more streamlined. However, carbon fiber is not a guarantee of better quality, as there have been carbon fiber foils on the market that are heavier and less rigid than those containing aluminum parts.
Types of Foils and Choosing the Right Foil
In theory, foils can be used across various surfing disciplines (windsurfing, kiteboarding, prone surfing, stand-up paddleboarding, wingsurfing, dock start), but it is best to learn and surf with a setup that is tailored to the specific discipline and the surfer’s skill level. In wing surfing, foils can be roughly categorized into beginner, freeride/freestyle, and race foils. This classification is not set in stone, and more precise categories may emerge as the sport develops.
When choosing a foil system, it is important to ensure that different sizes and types of front and rear wings and masts are available for the same system. As skills improve, it is sensible to reduce the size of the foil, but learning with a foil that is too small can be slow or even impossible.
Beginner Foils
Beginner foils are large and stable in flight. The foil is designed to take off easily, meaning that the lift is high even at low speeds (a brisk walk/jogging pace). This means that the wing area, volume, and thickness of the foil are all large. The wing’s shape (aspect ratio) is low, meaning that it is deep in the direction of travel. Such a wing is calm and predictable in its movements, but it is not particularly fast or gliding. However, a beginner should not fear that a beginner foil will be dull – flying on the water at 10-20 km/h for the first time is an exhilarating experience.
The appropriate size for a beginner foil front wing is usually around 20-25 times the rider’s weight in kilograms. For a 75 kg surfer, this would be 1500-1900 cm2. However, initial tests can also be done with a larger front wing. The size of the back wing depends on the rider’s weight and the length of the fuselage. It is important to follow the manufacturer’s guidelines when choosing the size.
Beginner foils usually use a short 65-75 cm mast. A short mast provides better control and more stable falls, but it can also make it easier to lift and ventilate the foil out of the water and cause falls. If more versatility is desired, an 85 cm mast can be used.
The fuselage of the beginner foil can be slightly longer, which provides more stability and smoother changes in flight height. Some manufacturers offer multiple fuse options, while others have a single fuse and adjustments are made by changing the size and shape of the back wing. Some foil systems also offer extension adapters to lengthen the fuse during the beginner phase.
Freeride and freestyle foils
In this context, freeride and freestyle foils refer to general-purpose foils that provide easy and enjoyable basic surfing and maneuvering.
The front and rear wings of these foils, designed for more advanced surfers, have smaller surface areas, volumes, and thicknesses than beginner foils. The aspect ratio is mid/high-aspect.
After learning the basics, it is recommended to gradually reduce the size of the front and rear wings. A small and slender foil is faster and glides better, allowing for more time for different turns and requiring less effort for steering. However, it is not advisable to drop the size too much at once, as a small foil always feels unstable at first.
Small foils (relative to the surfer’s weight) require more takeoff speed than beginner foils and therefore require more wind force and good pumping technique from the surfer to take off. It is convenient to have one larger front wing for light wind conditions of 4-6 m/s and another smaller wing for stronger winds. The rear wing can typically be the same size for both. On the other hand, with a suitable gliding board and a large 7 m2 hand-held wing, an experienced 75 kg surfer can take off in a small 800 cm2 race front wing in a 5 m/s gust.
The size of the foil of an intermediate surfer is determined by a combination of factors: the weight of the surfer, wind conditions, waves, the shape and size of the board, and the size of the hand wing. The style of surfing also plays a role, whether riding waves, pumping with the legs, performing tricks, or cruising calmly. The best foil setup for oneself is found through experimentation. It is recommended to acquire a foil system that has a variety of wings readily available. One does not need to buy everything oneself; they can try borrowing from a friend, attending demo days, or renting various foils or their components.
The agility of the foil is significantly influenced by the length of the fuselage and the size and shape of the rear wing. As the size (lift) of the rear wing decreases or the fuselage shortens, tilting the board in the lengthwise direction (pitch) occurs with smaller weight movement, making the board more agile. The profile of the rear wing also affects the board’s tilting in the widthwise direction (roll). By changing only the rear wing, significant changes can be made to the behavior of the foil.
The length of the mast varies depending on the intended use, ranging from 75-100 cm. A good general size that works in most situations is 85 cm.
As the length of the mast increases, the feel for the foil weakens, but on the other hand, the length of the mast helps keep the foil from coming out of the water easily when jibing or in waves, compared to a shorter mast. Many find it easier to surf with a longer mast than a shorter one. Pumping the foil with the legs becomes slightly more cumbersome with a longer mast, so 75-85 cm masts are often preferred for dock starts and wave riding.
Race foil
Race foils are designed to travel straight and perform stably at high speeds. The foil wings are high aspect (HA) shaped. The front wing surface areas are typically 600-1200 cm2. The optimal wing size is chosen based on wind speed, wave conditions, and riding direction.
To lift off with a thin, small front wing and achieve enough speed and lift, the board needs to accelerate and glide at a significant speed on the water. It is harder to lift off with a short, wide, and small freestyle board compared to well-gliding boards designed for HA foils.
The mast used is typically 85-100 cm long. A longer mast minimizes contact with waves and provides more tolerance for adjusting flight height at high speeds. When sailing upwind, the board can also be tilted more without the foil wing tip coming out of the water.
About foil design
On the market, most foils look very similar. However, a closer inspection reveals that some wings curve downwards or upwards, while others are straight. The wingtips can be thin or thick and have different degrees of rounding. There may also be sharp bends in the wingtips. These design solutions aim to create a foil that is directionally stable, predictable, glides well, is fast and generates enough lift. Characteristics are prioritized according to the type of riding the foil is designed for.
The wingtips that turn steeply up or down are intended to keep the foil stable in its direction of travel. The foil turns to the right or left (known as yaw in English) slowly but steadily in the direction of travel. These are typical characteristics of beginner foil back wings.
The thickness of the wingtips also affects the turning of the wing. Generally, in wide HA wings, the wing is thicker in the center than at the tips. This is intended to make the wide wing easier to tilt to the side (known as roll) and thus also easier to turn. The thick part of the wing creates lift, and lift is not desired at the tips because it would prevent the wing from tilting. Lift is preferably created in the center of the wing below the surfer.
The downward curvature of the wings may not always be intended solely for issues related to maneuverability and directional stability. It is thought that wings with a gentle downward curve ventilate, or draw in air poorly on the wingtip during turns, compared to straight or upward-curved wings. This means that the wingtip dives deeper and surface contact is less likely. Air entering underneath or above the wingtip causes lift to disappear, and the surfer easily falls.
On the other hand, it has been found later that front wings with a gentle downward curve more easily dive or drop sideways down into the water when the surface and lift in the turn decrease. Perhaps for this reason, many wings are omega-shaped or completely straight profiles. It should be noted that the behavior of the foil is, however, the sum of many factors, and driving characteristics cannot be inferred solely based on appearance.
WING BOARD ACCESSORIES
RENTAL
Are you a beginner or considering your next purchases?
Beginners need a large board and a foil. Some, especially those coming from other surfing disciplines, may only need these larger beginner equipment only a few times. Renting can be a good choice.
Surfing is faster with smaller, lighter equipment. Are you considering, for example, how small a front wing you can fly with, or how much more agile a foil becomes with a smaller rear wing?
