Surfboard fins: cutting water lines

Fins play a decisive role in surfing and surfboard performance. Surfers tend to believe it's all about shaping and surf skills, but fins have evolved much over the last 10 years. So, how should we choose a new set of fins?

There are nine major elements of a surf fin: material, base, depth, sweep, area, cant, toe, foil and flexibility. Surfers should pick fins carefully by adjusting their surfboard to their experience.

Molded fins are the most common kits available on the market. They often are seen as custom fins and come with the usual surfboards sold in a surf shop. There are also resin transfer molded (RTM) fins, a high tech units designed with aerospace-based concepts. The RTM fin has a layer of honeycomb foam covered in fiberglass. This gives it a stiff base with a certain amount of tip flex.

Surf fins can vary in flexibility. The most resistant fins ensure more drivability, while a softer kit provides more safety. Fins can be inserted into a wider or narrower base (found in the surfboard fin box) depending on your speed/drive preferences.

Shorts fins are great for "slide surfing" because they provide less friction in the water. Longer fins may help a surfer avoid wipe outs, but will also slow his or her rides. If the overall fin area (base plus depth) is rather large, it will be harder to turn and carve.

The sweep of a fin is very relevant, too. If your fins are strongly angled backwards, your bottom turns and cut backs will be more rounded. With the cant angle of a fin you may fine-tune the responsiveness of your surfboard: decreasing the cant will ride you faster in a straight wave line.

The toe angle is the angle in relation to the stringer. It can be angled inward, or not. If the front of the fins is closer to the stringer, making an inverted "V", any slight body balance adjustment will provoke a response from the surfboard.

Finally, look for the importance of the foil. Like on aircraft wings, you can find curved or foiled fins. In hydrodynamics, the more pronounced the foil, the slower you'll surf a wave, and a lift will be created under the surfboard. In the next chapter, we'll learn what are the best surfboard fins in the world for your level of surfing.

Buy surf fins at the online surf shop.