Basic Science of Surfboard Fins: Turning, Drive & Hold when Surfing

At some point in the progression of your surfing, you’ll inevitably find yourself questioning the performance of your equipment. Of course, initial inquires will be directed at your board. Once you’ve developed a preference in the length, width, thickness and rocker of your stick, you’re certain to shift attention to the fins. So you’ll want to understand the basic science of surfboard fins.

While it’s difficult to conceptualize how much of a difference fins can make, just remember that without them your ride would hinge completely on the will of the wave behind you. It stands to reason, therefore, that fins bridge the gap between simply being pushed by a wave and actively riding a wave.

Fins are to the surfer what tyres are to the driver: without them there is no point in getting behind the wheel. And, of course, the type of driving you’re planning to do heavily influences the type of tyres you’ll need. Such is the case with choosing the best surfboard fins for your surfing style.

The Basic Science of Surfboard Fins

The following is a short overview of their function and corresponding shape. It can be applied to surfing, SUP and bodyboarding.

Fin Function for Turning when Surfing

Perhaps the most basic function of fins is to keep your board pointed in the direction of your desire – to help you turn. Turning is directly related to the sweep, or backward angle of the fins.

The further back they appear to lean, the bigger the sweep and the larger the turning radius of the board. And the opposite holds true: the straighter up they stand, the smaller the sweep and the smaller the turning radius.

Science of Surfboard Fins: Straighter fins cause tighter turns.

How Find Affect Drive when Surfing

Besides the shape of your board, fins dictate how much speed you’ll gain by pumping down the face of a wave. Drive is affected by how much water is in contact with your fins. So, the longer the base of the fins where they meet the board, the more water is being pushed with each pump, and the faster you’ll accelerate.

Science of Surfboard Fins: Longer fin bases give you more speed.

Surfing Hold and your Fins

Hold is defined as the board’s ability to adhere to the face of the wave, especially the rear of the board where most of your weight is centered. More hold translates to more stability through turns and less slide across the face of the wave.

Fins with more depth, more length from the board to the tip of the fin, will stick tighter to the wave.  Short fins provide a looser feel and the potential to skim across a wave while turning.

Science of Surfboard Fins: Long fins keep your board pinned to the wave.

Turning, Drive & Hold when Surfing

Naturally, these basic functions are all relative to the board you ride and number of fins beneath it. SUPs and longboards won’t give you much of an opportunity for variation. Twin fin systems provide a looser ride than tri, or quad fin set-ups. But, no matter your circumstance, be sure to experiment and discover what the optimal equipment is for you. And as always, happy wave-sliding.

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