Design Forum

A Lesson In Fins

Here's a quick study in modern hydrodynamic technology. Y'Know, Fins.

Key Terms

Rake (a)

How far the front edge of a fin arcs backward.

  • More = Longer, sweeping wraps.

  • Less = Tighter, pivotal turns.

Base (b)

The distance from the front to the back of the fin, measured on the bottom.

  • Longer = More drive, acceleration, and hold.

  • Shorter = More release and sharper turns.

Height (c)

How deep the fin sticks into the water, measured from the board to the tip of the fin.

  • Taller = More hold and control.

  • Shorter = More speed and release.

Flex

How far a fin distorts from its original position during a maneuver.

  • More = Increased feel, for sharper turns.

  • Less = Increased stability, for longer carves.



Foil (d)

Varied thickness throughout the base of the fin controls its hydrodynamics.

  • 50/50: An equal curve on both sides, as found in most center fins. Even distribution, for smooth stability and control.

  • FLAT: Inner-side of fin is an even level. Most side fins have a flat foil, which creates a balance for most all surf conditions.

  • INSIDE: Curve on the inner face and the leading tip for a tighter and faster turning arc.

Cant (e)

The fin’s outward angle, in relation to the surfboard.

  • More than 90° = Increased response in turns.

  • 90° = Increased speed.

Toe/Splay (f)

The angle of the side fins in relation to the stringer. An inward angle (toe-in) increases responsiveness.

Fin Setups

Oversimplified descriptions of how many to put under your feet.

Single

Call it old school or call it retro, but don’t call it hipster. Increases stability and control, at the sacrifice of performance. Good for sweeping turns and down-the-line speed. à la: Gerry Lopez circa ’76.

Twin-Fin

Everybody loves twins. Having one fin on each side increases speed and maneuverability, especially in the small stuff. à la: Dave Rastovich in Byron Bay.

Thruster

Two foiled fins on the side for drive and a center spike for stability. The go-to, the shortboard standard, the breadwinner in the fin family. à la: Simon Anderson, and every pro surfer since.

Quad

Gives you the speed of a twin-fin, but adds the ability to hold in the pocket. Like a Corvette with 4WD. The side fins work as extensions of the rail, keeping things smooth like butter. à la: Nathan Fletcher, anywhere.