Surf foil appeared in the 2000s. Among the pioneers were big names like Laird Hamilton, Dave Kalama and Paolo Rista. Originally, it was just a way to fly above the water in tow-in surfing, in large swells. In 2016, Kai Lenny caused an explosion in the number of practitioners. The discipline immediately conquered Hawaiian, Australian, Californian and Brazilian surfers. The level skyrocketed. Progressively, Surf foil arrived in Europe, and in France. Understanding how a foil works, and what differentiates one front wing from another, is the first step before choosing your equipment and starting to learn.
Looking directly for which board and foil to buy? Our guide to choosing your Surf foil provides complete configurations by size and level, with board sizes, front wing, mast and stabilizer. This article explains how the foil works, which is the basis for understanding these choices.
Surf foil, an accessible sport in full expansion
The principle of Surf foil is simple: a submerged wing, fixed under the board, lifts the rider above the water as soon as the speed is sufficient. This mechanic concretely changes the practice of gliding.
The advantages of Surf foil most sought after by riders:
- More sessions possible: a small soft swell, insufficient for classic surfing, is enough to fly
- More spots available: no need for a wave that breaks sharply
- Extended gliding: the foil eliminates friction from the board on the water, allowing you to chain sections of a wave without losing speed
- New sensations: the sensation of flying above the water, very different from traditional surfing
What is a Surf foil made of?
The Foil is composed of the following elements: Mast, Fuselage, Front wing and Back wing (Stabilizer).
| Part | Role | Position |
| Mast | Connects the board to the fuselage and determines flight height |
Perpendicular to the board |
| Fuselage |
Connects the mast to the wings and influences longitudinal stability |
Horizontal, under the mast |
| Front wing |
Generates lift through its shape (curved upper surface, flat lower surface) |
At the front of the fuselage |
| Stabilizer |
Counteracts the lift of the front wing to stabilize the whole |
At the rear of the fuselage |
The front wing has a rounded leading edge that quickly gains thickness, then tapers to a thinner trailing edge. The "chord" is the width of the wing (from the center of the leading edge to the center of the trailing edge) and "wingspan" is its length, from one end to the other. The stabilizer takes on a shape similar to that of the front wing, with reduced surface area and a different profile.
How does a foil work? The physical principle of lift
The operating principle of a Surf foil is based on fluid dynamics. The front wing is pulled upward as it moves forward, because water molecules passing over the upper surface of the front wing accelerate to catch up with water molecules passing over the lower surface (which is shorter because it's flat). The acceleration of molecules on the upper part of the wing creates a depression and the slowing of those on the lower part creates overpressure. The consequence is a suction effect upward. The higher the speed of the Foil and the more the foil is "pulled" upward (at equal profile and angle).
You can easily compare how a Foil works to how an airplane works, which has a similar shape if you forget the mast and board. The speed of movement creates lift and allows takeoff. The difference in angle given to an airplane's wings allows it to stabilize in the air. The decrease in movement speed allows the lift to decrease and thus land an airplane (at constant angle of attack). Finally, to change the angles of attack of the foil, the rider can use alternating pressure on the front or rear foot to make the foil go up or down or stabilize. It's all about dosing pressure on the supports.
To take off, the speed must be high enough to create a lift force on the front wing. Combined with a high angle of attack (thanks to pressure on the rear foot) the board takes off. To stabilize, pressure on the front leg allows you to decrease the angle of attack, thus the lift and accelerate.
Swell as a source of energy
If the airplane uses the suction force of air molecules, the foil uses the suction of water molecules which have a much higher density than air molecules. This density will increase the lift (the upward suction effect) of the foil with speed.
In this article we talk about Surf foil, so the use of water movements (wave, swell, troughs, boat wakes) to fly. In contrast to wind which allows in kite or Windfoil the use of a constant external force to water, water movements of waves such as waves are variable forces with lift zones precisely located on the water surface.
As the diagram shows, only the wave movement zone actually carries you. On either side, the lift is neutral: this is where Pumping takes over to reach the next active zone.
What characteristics of the foil influence lift, speed, stability and maneuverability?
When dealing with fluid dynamics, the slightest detail or change made to the Foil is important and affects its characteristics. We focused on 4 major characteristics of a Surf Foil to explain which parameters influence them (there are many others but we won't cover them in this article).
Lift
The lift of the Foil, or the upward suction effect, varies mainly according to the size of the front wing, its thickness, its profile shape and the angle of attack. The larger the surface of a wing with thickness and the more lift it generates. The higher the angle of attack and the more it generates lift but slows the foil. Conversely, the lower these parameters, the less lift is generated. At equal surfaces, angles, thicknesses, two different profiles will result in different lifts and speeds. Surface alone as a reference parameter is not sufficient to determine if a foil carries a lot or not.
Indeed, the specificities of the front wing profile will play on the overall lift of the Foil. This can be the curve of the upper surface or the lateral curve, namely the one that goes from one side to the other in the length direction.
Finally, other external elements affect the overall lift of the Foil such as the weight of the practitioner, the weight and size of the board or obviously the power of the waves.
Speed
Parallel to the lift of the Foil, its speed depends on the surface and angle of attack of the front wing. A front wing with a small surface and/or little thickness will offer more speed, and a front wing with less angle of attack will also be faster.
Next, the specificities of the wing shape for the same surface play on the speed of the Foil. A wing with less chord and therefore more wingspan will be faster. Furthermore, the profile of the wing (parameters mentioned previously) is very influential on speed and the ability to accelerate.
Finally, as mentioned previously: the weight of the practitioner, the size and weight of the board but also the power and speed of the swell are external factors that strongly condition the speed of the Foil.
Stability
A relatively slow Foil with lots of lift (so large surface, wing thickness and some angle of attack) will be more stable than a less lifting and faster foil.
The main elements allowing the Foil to gain stability are the length (chord) of the front wing, its thickness and the surface and wingspan of the back wing, also called the stabilizer.
The back wing (stabilizer) fully plays its role in stabilizing the Foil. Its lift is opposite to that of the front wing and thus allows it to slightly counter the lift of the front wing by creating opposite forces to stabilize the entire foil.
External factors affecting the stability of the Foil are necessarily the weight of the practitioner and their technical abilities but also the type of water surface on which the Surf Foil is practiced. A rough water surface with current, eddies (backwash) and breaking waves will be more unstable because these elements disturb the depressions and overpressures that generate the upward attraction of the Foil (like air turbulence when you're in an airplane).
Maneuverability & gliding
If a Foil with little lift (so little surface, angle of attack and thickness) is faster and indirectly more maneuverable, it's not the only parameter that affects its maneuverability.
The major element concerning maneuverability remains the shape of the front wing, namely the lateral curve, which when accentuated allows you to turn more easily with the Foil. A high lateral curve will give a more maneuverable foil but slower because for the same lift surface (shadow cast on the ground) the total surface will be larger and will slow it down. Conversely a flatter lateral curve will turn less but will be faster.
Wingspan also influences maneuverability. The greater the wingspan and the longer the foil will glide but the tighter the curves will be. It's a bit like a longboard and a shortboard.
Summary
The general shape and dimensions of the Foil vary these four characteristics:
- The larger, thicker a wing with angle of attack = the more it carries and the slower it goes
- The smaller a wing, with little thickness, little angle and little chord relative to its wingspan = the faster it is
- The more wingspan a wing has and the longer it will glide and therefore it will be effective at Pumping.
- The larger and thicker a wing with chord length = the more stable it is
- The smaller, thinner a wing with curve = the more maneuverable it is
- The more wingspan a wing has and the less maneuverable it will be.
What equipment to choose to start Surf foil?
Equipment choice comes down to two axes: the surface of the front wing, to be adapted to the swell and level, and the volume of the board, to be adapted to size and experience. The heavier the board, the more the foil's lift will be countered (opposing force). Conversely, a gain in volume allows you to better catch waves to take off.
| Rider profile | Reference foil | Why |
| Starting Surf foil | HA range, around 1190 cm² | Generous lift, easy takeoff, foil tolerant to errors |
| Progress, more organized swell | HA or UHA range, around 1000 to 1200 cm² | Good compromise between lift and speed |
|
Confirmed rider, powerful swell |
UHA range, reduced surface |
Speed, control and Pumping efficiency |
On the board side, our SW range covers all sizes, from 4'4 in 32 L to 5'6 in 50 L, at the same price of 649 € regardless of size. This is where the choice of a Surf foil board is made, the volume and length following the same progression logic:
| Board | Volume | Recommended profile |
| SW 4'4 (Elite range) | 32 L | Small sizes or confirmed riders looking for maneuverability |
| SW 5'0 (Elite range) | 40 L | Average sizes, the choice that suits the most people |
| SW 5'6 (Elite range) | 50 L | Heavier sizes or looking for easy gliding |
| DW 7'2 (Elite range) | 110 L | For light or demanding riders |
| DW 8'3 V2 (Elite range) | 115 and 125 L | Suitable for all riders, from beginner to confirmed |
In Surf foil, the most common mast length is between 70 and 80 cm, a compromise that handles chop well without harming maneuverability. A wider stabilizer makes it easier to balance when learning, at the cost of a little speed.
SROKA Company developed its S-Foil around three priorities: accessibility, with a wing profile tolerant to errors to support learning; versatility, to navigate as well in Wing foil as in Surf foil with the same quiver; and performance, with a fuselage and stabilizer adjusted to Pump easily while remaining maneuverable.
For a detailed comparison according to your level, your size and your spot, our complete article to choose your Surf foil well details all configurations, including the choice between Carbon and Aluminum.
How to start Surf foil? Exercises to progress step by step
Learning Surf foil follows a logical progression, from flat to wave.
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Get your bearings on flat water: lie down on the board to find the balance point before even trying to take off.
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Practice Pumping in Dockstart: Pumping on a flat water surface, from a dock or pump foil spot, allows you to understand how the foil reacts without depending on the swell.
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Choose an adapted spot : a soft and regular swell is much better suited to the first sessions than a wave that breaks hard.
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Stand up progressively, keeping your gaze far ahead rather than on your feet.
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Dose the front/rear pressure to control the angle of attack and stabilize the flight.
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Extend the glide by Pumping once the basics are acquired, to chain climbs and stay in flight without coming back down between two sections of wave. Our article on Pumping in Surf foil details the technique step by step.
The most common mistakes in Surf foil
Here are the mistakes that come up most often with riders starting out in Surf foil, and how to avoid them.
- Mistake #1: choosing a foil that's too small to start. A low-lift front wing makes takeoff difficult and quickly discourages. It's better to favor a generous surface at the beginning of learning, even if you reduce it later.
- Mistake #2: pushing too hard on the rear foot at takeoff. The angle of attack climbs too quickly, the foil comes out of the water abruptly and the rider loses balance. Progressive pressure works better than a firm push.
- Mistake #3 : keeping your gaze on your feet. Loss of visual reference almost always leads to loss of stability, regardless of the rider's level.
- Mistake #4: neglecting safety. The foil is sharp: wearing a leash, keeping sufficient distance from other riders and checking water depth before launching greatly reduce the risk of injury.
- Mistake #5 : wanting to progress on a spot that's too demanding. A wave that breaks near the shore complicates getting back in the water and slows learning. A spot with a gentle slope, even on a wave of less than 60 cm, is plenty for the first sessions.
- Mistake #6: ignoring foil adjustment. The position of your feet on the board and the stabilizer adjustment directly influence the available lift and stability. Poor adjustment accentuates the flaws of a foil that's already demanding for the rider's level.
A foil transforms speed into lift through the shape of its front wing: the larger and thicker it is, the more it carries; the thinner and more elongated it is, the faster it goes. Understanding this principle allows you to choose equipment suited to your size and build a progressive learning path, from flat to wave, without skipping steps.
