Foil Wings – Why Size Matters.

When buying an eFoil, you may be confused about which foil wing to use, with your board. This article will discuss how wing size, shape and material will impact your performance.

Determining what foil will work best for you depends on your weight, skill, and where you want to use it. Foils mostly differ in price, maneuverability, speed, and ease of use. 

Before we explore these topics lets review the basic components of an eFoil:

Foil Wing Size

There are several important dimensions for foiling. The front wing surface area, rear wing surface area, and fuselage length all play a role. 

The surface area of a wing is a good indication of how much lift it will generate. The larger the surface area, the more lift is generated. Surface area is usually measured in centimeters squared. 

The best foil for beginners often use a large front wing because it will lift rider at lower speeds and provide more stability. Larger foils are good for use on still waters or small waves because they have enough surface area to lift the board with only a limited amount of energy provided by the propeller. However at faster speeds a large wing becomes difficult to prevent from breaching because so much lift is generated.

On the flipside, smaller front wings require more speed to attain lift,so they have a higher minimum speed for foiling. They are also easier to control at higher speeds. Smaller foils are good for use on large waves because the water provides additional power to lift the board.

While most people begin with a larger wing, as they become more skilled, they opt for smaller and smaller wings. Decreasing wing size is a way to unlock higher speeds and more maneuverability. 

The best size foil depends on the size and skill of the rider, and conditions it will be used in.

  • Heavier riders will need a larger wing to lift them out of the water.
  • Beginners will also find a larger wing easier to learn on because they will be slower and more stable.
  • Lighter riders need the wing to generate less lift so a smaller wing should be used.

More advanced riders will find smaller wings more maneuverable and controllable in larger / faster conditions. This is because they create the required amount of lift at higher speeds, but not too much to lose control ability.

Foil Wing Shape

Wings may or may not include a hedral. When viewed from the front, wings are either flat or angled. An angled wing has “hedral” whereas a flat wing does not. If the wing is angled upward, it is called a dihedral, if angled downward it is anhedral. Wings with multiple angles are known as polyhedral.

Flat wings have more roll stability. Though that sounds like a plus, that also means they require more energy and skill to maneuver efficiently. A flat wing’s tips will also breach earlier, preventing them from turning as tightly as down turned (anhedral) wing tips.

Anhedral wings are shaped like an upside down “v”. This gives them roll instability, which makes it easier and more efficient to turn. This shapes is generally best suited for surfing, tighter turns and carving.

The best foils for surfing use anhedral or polyhedral wings because they are designed to be usefully unstable. 

Polyhedral wings can combine the benefits of more than one shape.

Dihedral wings are not found on eFoils. Their “v” shape self-stabilizes in the water, which may seem appealing initially but in practice they are difficult to turn and inefficient. 

Front Foil Wing Aspect Ratio

Aspect ratio is the ratio of the wing span to its mean chord. Long narrow wings have a higher aspect ratio, while short, wider wings have a lower aspect ratio.

Higher aspect ratio wings are more efficient at lifting, they produce more lift for the same drag when compared to a lower aspect wing. This means they require less energy and have a higher top speed than lower aspect wings.

High aspect wings have more roll stability and the wing tips breach before wings with a shorter span. This makes them less maneuverable and less carvy than low aspect wings. Lower aspect wings require less energy to turn.

Section Shape

Section is the shape of the wing when viewed from the side, perpendicular to the fuselage.

The section shape also plays an important role in the amount of lift generated by the wing. In general thicker (taller) section shapes generate more lift, especially at low speeds. This is why the ideal foil for beginners often have a thicker section shape.

Thinner sections will generate less lift but also less drag. Thinner sections have a faster minimum take off speed, but they also have a faster top speed. This is why the fastest foils will have a thinner section shape. Some wings are designed with multiple section shapes at different locations along the wing span.

The ideal section shape is generally determined by the desired range of speed the eFoil will be ridden. A thicker section shape will generate more lift at lower speeds, but then top out more quickly as speed increases.

Fuselage Length

The fuselage length impacts pitch and yaw stability. A longer fuselage will be more stable in pitch and yaw. However a longer fuselage will also add weight and increase turning radius which decreases overall maneuverability.

With a shorter fuselage turns become tighter and more efficient with the trade off of requiring more energy to maintain balance.

Generally a shorter fuselage length is preferred because they are more maneuverable.