Comparing WWF and Wing Foiling
(Written October 2023)
It's been four years since I started windsurf wave foiling (WWF). It has been one of the best decisions I've made. Lisa and I got into WWF to get more time on the waves with better conditions. The sport has greatly exceeded those expectations as we consistently catch wave and wave after wave. Many athletes are having the same experience with wing foiling. There is always a lot of discussion about the differences and similarities between WWF and wing foiling. Much of the nuance is lost when talking about it while at the beach as we are all focused on getting in the water, so I thought I would put it in writing to make it more clear. Let's break down the discussion into parts and take a look at how these two sports compare.
1. Sail versus Wing - This is where the conversation must start. The most dynamic difference between the two sports is largely due to the use of a sail compared to the use of a hand-wing. This difference doesn't make one sport better than the other. However, it makes the two sports separate and unequal. A quick glance at both kits and one will immediately notice that the sail is attached to the WWF board, while a hand-wing is flying free within the grasp of the wing foil rider. There are two major implications as a result of having the sail attached to the board compared to a wing flying free. First, the WWF sail imparts force on the foil every time it rotates. This force induces roll in the foil. The magnitude of roll that is induced in the foil is related to the number of degrees the sail is tipped from its perpendicular starting point on the board. The more the sail is tipped the more it induces roll on the foil when it rotates. On flatwater, rotation of the sail typically only occurs when jibing. But when wave riding the sail rotates hard on every single cutback. The rider must account for this by countering the roll in the foil with pressure in the heels and toes of the feet and by learning to tip the sail in the correct direction with proper magnitude. Second, the WWF sail is attached to the board near the nose of the board which results in considerable downward pressure. This is contrary to wing foiling (and kite foiling) where the wing (or kite) creates upward lift. This downward pressure of the sail on the nose of the board requires more stab angle in the rear foil wing to compensate. It also requires a front foil wing with enough lift to push back against the downward sail pressure without losing grip. Wing foiling, on the other hand, does not have this downward pressure. In fact, the wing does the exact opposite and provides upward lift when engaged. As a result, one can use a front foil wing with less lift and grip, along with a tail foil wing that is mostly flat.
2. Board - The boards used for both sports initially stemmed from modified SUP foil boards. These boards generally have a tail behind the foil and are fairly thick. While WWF boards kept the modified SUP foil board approach, wing foil boards quickly evolved into smaller versions with no tail. The tail gives the board designer a location to add float without affecting swing weight in the nose or stability in the thickness. It also adds length to the board to provide more glide when increasing speed to get up on foil. Many wing foilers are willing to sacrifice added float and glide for the sensation of riding a smaller and highly snappy board while accepting that they will need a larger hand-wing to compensate for the reduced glide. WWF riders, on the other hand, have generally leaned toward accepting the extended tail of the board so that they can use the smallest sail possible which allows them more maneuverability in the sail with a small sacrifice in board snappiness. The smaller sail induces less force on the foil. This is a major difference between the two sports. Wing foilers generally (but not always) prefer a smaller board and larger hand wing while WWF riders generally prefer a smaller sail and larger board. When at the beach, you will notice that WWF riders are generally on sails that are a half meter to one full meter smaller than the hand wings being used in the same wind strengths, while wing foilers are generally on boards that are 20-50 liters smaller that the WWF boards being used. For very light wind, however, some wing foilers have gone to the other extreme by using a long narrow board with a long tail for extra glide on top of a large hand-wing. This approach requires a two board quiver.
3. Foil - There are many characters traits of foil wings. The most commonly discussed traits are surface area, foil thickness, aspect ratio, and camber. These four traits combined help to define lift, glide, and maneuverability of the foil. In general, the less lift that the foil provides, the larger sail or hand wing the rider will need, all other things being constant. Wing foilers generally prefer smaller surface area, thinner profiles, and higher aspect foil wings, while WWF riders generally prefer lower aspect, slightly thicker profiles, and larger surface area foil wings. This allows the WWF rider to use the smallest sail possible for the greatest maneuverability above the water, and it allows the wing foiler greater maneuverability under the water with the sacrifice of using a larger hand-wing. Wing foilers generally have their feet positioned much closer to the centerline of the board which requires them to use more sensitive foils that don't push back much. WWF riders on the other hand generally position their feet at the rails of the board which gives them considerable leverage to push back against the larger/thicker foils required to accommodate the sail attached to the board.
4. Fuselage - While a minor difference, the length of the fuselage in front of the foil mast matters and differs between the two sports because it positions the front foil wing differently. When the front foil wing is positioned closer to the foil mast it makes the kit more turny. When the front foil is positioned farther in front of the foil mast it allows the foil to pump slightly better. In general, wing foilers prefer to have the front foil wing farther forward of the foil mast to allow them to pump better because they can find added maneuverability by using smaller boards. WWF riders, on the other hand, prefer a larger board to accommodate the forces of the attached sail, so they prefer to accept loss of pumping ability and added maneuverability with the fuselage shorter in front of the mast. While this may not be true for every rider in each respective discipline, it is what is most frequently observed.
As you can see, both sports use a foil but they have very different approaches. The industry has selected wing foiling as its new baby. There are lots of companies designing wing boards, wings, foils, and gear. WWF on the other hand has barely any companies serving it. Boards must be custom built by small local designers. The sails the really work well for WWF are kid sails not specifically designed for WWF. There are very few companies that build functional versions of these kid sails. The larger low aspects foils that work well for WWF are being phased out by many companies as they shift their focus toward wing foiling. Since both sports have advantages and disadvantages I suspect that WWF will grow more quickly once a larger number of professional athletes discover the advantages. Until then, those of us performing WWF will continue to develop the sport on our own.