Windsurf Fins Introduction
Finn's profile:
If you saw your fin over and look into the surface that has emerged, you are looking at the profile of the fin. All fins are based on the same profile – namely the aerodynamic profiles from NASA, where the thickest point in the profile is approx. one third remaining in the length of the profile. Airplane wings, wind turbine blades, downforce on Formula 1 racers and windsurfing sails are all based on the profiles from NASA. These profiles create optimal lift when the water flows over the fin. The profile can be varied in the profile length, i.e. the width of the fin in the longitudinal direction of the board, it can be varied in the profile thickness, i.e. the thickness of the fin, and then it can be varied in the location of the deepest point. A long profile length provides a stable fin. It takes a lot for it to release its hold in the water and go into spinout. If it goes into spinout, it is easy to get back on track. A short profile length provides a fast fin that goes well. On the other hand, it is a very hysterical fin that easily spins out if it is angled incorrectly and is difficult to get hold of again. A thick profile gives lots of lift at low speed and gets you planing quickly. However, the thick profile will quickly reach a speed limit where it cannot slide faster through the water. The thin profile is the fastest profile. The water flows quickly over it and there is no upper speed limit. On the other hand, you have to work harder to get into planning – e.g. by pumping actively with the rig. The profile's deepest point is approximately one third back in the profile's length. If the deepest point is moved forward a little, the properties for climbing height are increased. If the deepest point is moved back, the fin can become faster in half wind and sail.
Finn's Outline:
Materials:
The choice of material is very important for the properties of the fin. At the soft end there is plastic. Slightly stiffer are fiberglass fins with a foam core or in solid fiberglass. Even stiffer is G10, which is many layers of fiberglass laminated together and hardened under many tons of pressure. The stiffest material in which fins are built is carbon fiber with a foam core. The softer materials are the cheapest materials, but they are also materials that make it most difficult to control finn's shape when it is loaded. In order to achieve stability and torsional stiffness, the shaper has to choose a relatively thick profile. With the stiffer materials, the shaper can more precisely control the shape of the fin when it is loaded and often a thinner profile will be able to create the same stability and control with the torsion. A slalom fin in G10 can be made a few millimeters thinner in carbon fiber. The thinner profile is faster and there is still control over the shape of the fin.
The fin is a very important part of the whole windsurfer. Much more important than many people think
- Søren Christensen, Windsurf specialist
The various windsurfboard fin boxes
Windsurf fin boxes
Overall, there are 5 different fin systems:
WIND SURF: SLALOM/RACE/FREERIDE
There are 4 setups for these board types:
Freeride Fins:
In general, freeride fins are long and the outline is more vertical. On the small freeride boards that are sailed in waves or chop, the fins are oriented towards wave fins with more curvature and longer profiles. It provides control and indulgence. On the big boards that are sailed on flatter water, they are oriented towards racing fins with a vertical outline and short profiles. It provides early planing, speed and good height. It is a very broad category, which extends from low-cost plastic fins to high-end carbon fins.
Pincer fins:
The seaweed fin is a necessary compromise. Just a piece of eelgrass can cause a high-performance racing fin to lose all its good qualities and go into spinout. If you sail in waters with seaweed, the solution is a seaweed fin. The backward outline gives a very long profile which is very stable but slow. The pressure point on the board is moved backwards, and the mast foot must be moved backwards to compensate for this.
Breed Finder:
Uncompromising fins with a very straight outline and short and thin profiles. The planing is done by active pumping with the rig. The Finns can sail very fast and go a really good height. On the other hand, they must be managed precisely so as not to go into spin-out. The materials are at least G10 and most often carbon.Delta fins:
A completely different way of thinking about fin shape. To ensure a short fin for areas with shallow water, a very chubby outline is created, where every square centimeter of the fin is right up under the board. The fin is pulled forward in the box, which ensures that the pressure point does not migrate backwards. The large delta fins are excellent for seaweed. The shortest delta fins have sailed close to 80 kilometers per hour at the northern end of Ringkøbing Fjord.
WIND SURF: WAVE
There are 4 different fin setups for wave windsurfing:
WAVE FINS are short and curved to ensure good maneuverability. The curvature ensures that the fin can flex and e.g. grab again after a jump. The fin is super stable and does not spin out when there are many air bubbles in the water, e.g. in the surf.
Thruster:
The thruster has 3 fins: a larger center fin and two smaller side fins. That combination provides good stability and speed, and is used a lot in onshore conditions. Center fins are most often from 17–21 cm and the side fins are from 8–11 cm. It is a combination that can be adapted according to board, conditions and weight.
Quads:
The Quadden's 4 fins make it ideal for down-the-line waveriding. The two rear fins are slightly larger than the two front fins. Typically, the rear ones are from 15–17cm and the front ones from 10–12cm. You want to use larger fins in conditions of light wind and with a heavier sailor, and smaller fins if you are a light sailor or there is a strong wind. Again, the best advice is: Experiment to find the best combination for you.
Twin fin:
The twin-fin setup is not used that much anymore, but can be a fun setup if you are on a big waveboard and want it to turn a little better and be looser. It's a setup that surprises many - try it yourself!
Single fine:
Singlefins are by now an old school thing that was used in the 80s and 90s. A single fin setup provides high speed and stability, but does not turn as well as the new setups, with multiple fins. The size of wave single fins is anywhere from 17–25cm. The more wind, the less fin, e.g. an approx. 17–19cm fin when sailing with your 3.7m2 sail (depending on the sailor's weight). The further forward you place the fin, the better maneuverability your board will have. If you move the fin further back in the finbox, it will, on the other hand, give more speed.
