Fins are the extrusions on the bottom of the board. They vary in size and composition and there is a wide range available for surfers to choose from, each type having its own benefits and properties when concerned with the handling of a surfboard. In the older days of surfing there was only one type of fin available, the fixed fin. In this situation fins were set with resin when the board was glassed. Now days technology has allowed for fin development, subsequently we now see the use of Clip in Fins. This interchangeable fin system allows surfers to pick and choose fins for the conditions. Also when travelling the fins may be removed to prevent them being damaged in air freight or in the back of the car.

The primary purpose of fins on surfboards is the same as that of a rudder on a boat. It is the steering component of a surfboard and shares the responsibly with all other components in keeping the surfer locked into the zone.

There are three main properties to a surfboard fin:

• Rake
• Depth
• Base Length

The Rake is the the distance from the tip of the fin to the base of the fin relative to the rear end of the board. If that does not make sense to you then see it described on the diagram. Basically the Rake is an angular component, generally speaking the smaller that angle is the faster the surfboard can move. However as this angle becomes smaller the fin essentially looses depth and hence looses turning ability. So Rake is a pretty important concept when selecting a fin to suite your surfing tastes.

The Depth is just that, the depth at which the fin penetrates the water. It is measured from the bottom of the board through to the tip of the fin. The more depth your fins have the more grip you will have in the water. Larger waves will require more grip as you are moving much faster and when you turn sharply it is important that you 'grip' the wave, making fin depth a crucial property when choosing your fins.

The Base Length is the length of the fin a long the bottom of the board. It is basically the section that makes contact with the base of the board. In a generally sense the longer the base length the quicker your are able to move and more power you can generate when riding a wave. The Base Length can confine the other fin properties (Rake and Depth) so be careful when choosing this property.

The choice between fixed and variable fin systems is completely up to the surfer. Most production boards these days come with interchangeable fin systems, however many surfers still go for the fixed fin option.