Surfboard Fin Design Basics

Surfboard fins have a huge effect on how your surfboard performs – if you’ve ever broken a fin and continued surfing or swapped the fins on your favorite board, you’ve probably already got a sense for it.

And if you’ve ever walked into a surf shop and have been overwhelmed by a wall of different fins, you definitely know you have some options.

But where do you start when selecting new fins or designing your own? It’s really not as difficult as it may seem.

With a little help from the curious minds here at WAVE ARCADE, you’ll be a surfboard fin master in no time.

Why are your surfboards fins so important?

Think about it, the fins are the one part of your surfboard that are almost always in contact with the water. They have a huge influence on drag, the flow of water over and off of the surfaces of your board, and how you’ll be able to move into, through, and out of turns.

With different fin setups on the same board in the same conditions, it can feel like you’re surfing something completely different.

Certain fin designs are better for speed, some for quick maneuvers, some for solid turns, and still others for drive, stability, and noseriding.

Once you wrap your head around some of the basics of surfboard fin design, you’ll be able to easily choose the best fin for the type of surfing you want to do in the type of wave and conditions you’ve got to work with.

The Characteristics of a Surf Fin

The major characteristics of your surf fins that affect performance are:

  • Fin Foil
  • Fin Flex
  • Fin Base
  • Fin Depth
  • Fin Rake/Sweep
  • Fin Size

Surf Fin Foil

The fin foil is the changes in width of the surf fin from its leading edge to its trailing edge. Fin foils can be described as symmetrical or asymmetrical.

Symmetrical surf fins, also called a 50/50 foil, are often found on the center fin for thrusters, single fins, and sometimes the rear fins on a quad set up.

Asymmetrical surf fins, which can be flat on one side or have a different foil ratio on each side (e.g. 80/20, 70/30, inside foil, etc.), are often found on the side/front fins on thrusters and quads.

A fin’s foil controls the board’s lift and drag forces as water moves over the bottom of the board. The foil has a major influence on how your board turns and how quickly it can move into and out of turns.

The largest or thickest part of a fin foil is often best set towards the front center of the fin. Generally, a thicker fin foil equals more lift, but a thicker foil will also create more drag at higher speeds.

The leading edge of a surf fin’s foil should typically be round rather than sharp. This allows the water to flow over the surface of the fin smoothly and reduces turbulence. Sharp edges or knicks in the surface of the fin can lead to break off points in which the water will break off from its uniform flow over the fin too soon. Just like imperfections on the bottom of your board, that’s no good.

Surf Fin Flex, Twist, and Recoil

A surfboard fin’s flex or twist has a lot of influence over how your board will feel through turns and the speed you’ll be able to generate.

Flex typically is controlled by the shape, foil, and material of the fin.

Stiffer fins will get back into shape quickly, while flexy fins will be slower to recoil.

A more flexible fin is good for long, drawn out carves and turns, while a stiffer fin is generally good for quick maneuvers and speed.

Surf Fin Base Length

The fin base is the portion of your surf fin that is connected to the bottom of the board. In other words, it’s the bottom most portion of the fin that’s in the water.

A longer base gives you more drive, hold, and more drawn out turns. A shorter fin base results in a board that’s easier to pivot quickly, but sacrifices some drive and stability down the line.

Surf Fin Depth

The fin depth refers to how deep the fin is in the water. It’s measured from the fin base to the fin’s tip.

A deeper, or longer, surfboard fin is going to have more hold and stability in the water and through turns. A shorter fin makes it easier to throw out the tail and surf loose.

Surf Fin Rake/Sweep

Fin rake or fin sweep refers to the angle between the base and tip of the fin. It has an influence on how your board will turn. This is what gives your surfboard fin it’s profile or shape.

The smaller the angle (or the further back the tip ends), the more drawn out your turns and carves will be.

A fin with a larger sweep angle (or a more upright looking tip profile) will have more release and allow for quick pivots.

When designing or choosing a surf fin, it’s important to consider the other characteristics of the fin like its foil, flex, base, and depth in conjunction with the shape to get the best idea of how it will perform.

Surf Fin Size/Surface Area

Finally, fin size refers to the overall surface area of your fin. This will have a big effect on how the fin performs depending on the surfer’s weight. Most fins companies categorize their fins by sizes/weight categories to make it easy to choose.

In general though, discounting surfer weight for a moment, a smaller fin will have less hold, and will be easy to pivot and slide, while a larger fin will have much more stability and hold.

Common Surfboard Fin Shapes & Designs

Using the above characteristics, you can create a surf fin in endless combinations of size, rake, depth, base length, and flex.

If you’re not sure where to start, you can always fall back on some common surf fin designs and start from there.

The flex fin, which almost looks like a sickle from the side, will provide you with the most flex and the most drawn out turns.

As you increase the sweep angle, you’ll start to trade turn projection for quicker turns.

Increasing the sweep angle more and adding more surface area results in a fin that’s good for noseriding and down the line drive.

Finally, you end up at the classic D fin shape (which looks like a filled in letter D), which is often found on old-school logs and allows for speed down the line, while sacrificing turn project for more pivot-y turns.

Leave a Reply

Your email address will not be published. Required fields are marked *