Surfboard Fins And Their Functions

Surfboard fins are very important to surfboard design and surfing. Similar to the rudder of a boat, surf fins work to stabilize and steer a surfboard and prevent surfers from spinning in circles while riding a wave. With them, a surfboard can glide in a controlled path.

Surfboard fins come in a variety of shapes, sizes, and even flexibility, that suits every surfers surfing preferences. However, one thing is common to all of them, they all have a curved appearance. These things may sound simple to you, but in reality, their science and design is quite complex.

Much like surfboards, surf fins have undergone a series of evolutionary changes since their invention. Early surfboards did not even have fins. Surfers used to drag one foot in the water to control their boards.
However, an important breakthrough took place in 1935, when Tom Blake introduced his "Nub Keel Fin". Soon after, almost every surfboard was being shaped with fins fixed to the bottom of the board. Moreover, designs were not given due importance until the 1990s. Today, they have become the number 1 surfboard accessory with many manufacturers, such as FCS and Future Fins, leading the way.

Basically, there are only two types of fins used in surfboards, the glass-on and the removable types. The only difference between the two is that removable types can be taken off the bottom of the surfboard at any time and can be replaced with a different set. Glass-on types on the other hand are fixed and cannot be detached.

An adaptation to these two types is soft fins, most commonly used on rental boards. This is because they are safer for beginners to use as they do not cut or injury the body. Unlike fiberglass glass-on and removable types, soft fins are known not to perform as well with most professional surfers refusing to ride them.
The performance properties of surfboard fins are dependent on their design and specific measurements. Some basic parts of a surfboard fin include its depth, base length and rake.

The depth of a surfboard fin is its measurement from the base of the surfboard to its tip. It determines how deep it goes into the water. This feature is what holds the surfboard to the water when it moves, pivots or turns, known as traction or hold. The more the depth is, the more controllable the surfboard is, most importantly when turning.
Base Length
The base of a surfboard fin is the part that connects with the face of the bottom of a surfboard. It is also the widest part. This part determines how much speed and drive the fin can contribute to the board. The longer the base length is, the more speed and drive the board will have. Thus, if you need more speed, choose fins with long base lengths. They are very effective.

The Rake, also known as "sweep", is the angle created between the back part of the base (the part of the base closest to the tail of your surfboard) and the tip of the fin's offset and has nothing to do with rake we commonly use in our gardens. The smaller the angle of the rake, the more drive will it provide, but the surfboard becomes more difficult to maneuver. Consequently, when the rake angle is greater, the board can make tighter turns with a sacrifice in speed.

The Fin Setups and their Uses
Now let's look at the variety of fin setups you can choose from.

Single fin is the original setup and is commonly used in longboards. Compared to other setups, single fins are usually wider and longer making the board more stable and controllable even with just one fin.

Twin fin setup is composed of two parallel fins attached to the bottom of the surfboard. With this, the board is faster and easier to turn. Twin setup fins are usually identical in all dimensions.

Thruster setup is the most common of all. It is a three-fin setup and is also composed of three identical fins. In this setup, 2 fins are placed parallel to each other while the third one is placed in the middle, slightly further back towards the tail of the board. This is the setup found on most high performance shortboards.

2+1 setup is also composed of 3 fins with two fins positioned parallel to each other, while the third one is adjustable and is larger than the other two.

Quad setup is composed of four fins, with the 2 attached to each side of the surfboard bottom. This setup is commonly used in shortboards meant for surfing small, powerless waves. This is due to the fact that this setup provides more speed as the absence of a middle fin reduces drag.

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