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The Definitive Surfboard Fin Guide

by Boardcave on April 30, 2015

Choosing the right fins for your surfboard

The fins you put in your favorite surfboard can play a huge role in your performance on that board. Some people even claim that your choice in surfboard fins can impact up to 40% of your performance. With so many different boards and different conditions, it’s important to think about different fins and fin setups that work the way the shaper intended the board to be ridden.

The best thing is, just like surfboards, fin design, templates and experimentation is almost endless.

Before you dive head first into testing, its great to know a little bit about how each characteristic can impact your surfing performance. Lets start with the basics.

john john florence throwing his futures fins
John John showing off his Futures Fins.

Fin Basics

Fin Size | Fin Base | Fin Depth | Fin Rake | Fin Foil | Fin Cant | Fin Toe

Some more advanced stuff…

Fin Shape

Part Two

Fiberglass Fins | Composite Fins | G10 Materials | Performance Core Fins | PC Materials and fin flex

Fin Size

The size of the fin is going to impact your performance… A larger fin generally will have more hold and also provide plenty of control in bigger surf. A smaller fin, on the other hand, is going to be more forgiving and loose but you’re going to sacrifice a lot of drive and control in bigger surf.

Surfboard Fin Size explained with FCS II
Difference between the FCS II MF Performance Core Large (on the left) and the MF Performance Core Medium (on the right) fin sizes.

Fin Base

The part of the fin that is actually attached to the board is called the base of the fin or the fin base. A longer (or wider) fin base is going to help with your drive. This translates into drawn out turns. Compare this with a narrow, or short fin base that is going to let you turn a little easier and sharper but without as much of that drive.

Surfboard Fin Base explained with Futures
On the left – The AM2 Futures Fins (top) have a longer base than the Haydenshapes Futures Fins (middle) that are still longer than the F4 Futures BlackStix Fins (bottom). On the right is the EA BlackStix Futures fins.

Fin Depth

The fin depth or fin height refers to just how far the fin extends away for the bottom of the board. A deeper fin in the water is going to have more hold and stability than a shallow fin. The more shallow a fin, you are going to get more release when you throw that tail around through turns.

Fin Rake

When you’re looking at the arc of the fin and how far back it tilts or sweeps, you’re looking at the fin rake. The larger the degree of rake, the more drawn out your turns will be. This is great for those bigger days with a nice long wall to work with. Less fin rake and a more upright fin template, means that you’re going to get some more pivot out of them – great on junkier, weaker days.

Surfboard Fin rake or surfboard fin sweep explained
The degree of surfboard rake or surfboard sweep determines whether you have a looser feeling in your fins or you get more pivot out of them.

Fin Foil

The fin foil is an aerodynamic shape from front to back of the fin. Much like the wings on an plane, this foil generates lift under the board. A fin is usually going to get thicker through the center of the fin and taper smaller out towards the edges.

There are a couple of types of fin foils with many variations on each. Side fins (on twins, thrusters and quads) are generally flat, sometimes curved inward on the inside and with a foil on the outside. Center fins will mostly have equal foil or double foil on each side. These center fins are found on the back of thrusters, single fins and sometimes the rear fins on quads. Double foil can also be found on some more traditional twin fin fish models.

Surfboard Fin foil explained
Fin foil determines the volume of a fin as well as how the water moves past your fins’ sides.

Fin Cant

Fin Cant is the degree of outward angle a fin has in relation to the bottom of your surfboard. If a fin has zero cant it’s position straight up and down at a right angle to your board. This is going to be fast in a straight line, but it won’t give you as much responsiveness through turns. If the cant of your fin is larger, your going to gain a little more of that responsiveness through your turns. It means you can maintain some more drive when your board is tilted on the rail.

Surfboard Fin cant explained
More Fin Cant means your fins are angled outward in relation to the bottom of your surfboard.

Fin Toe

The toe of your fins set up is relating to the angle that your fins are pointing at towards the stringer. This occurs a lot in side fins with the front of the fins pointing towards the center of your board. This can help create pressure on the outside foil of the fin. This in turn, allows you to again have a little more responsiveness on your board.

Surfboard Fin Toe explained
The Toe of a surfboard fin above shows the side fins angled towards the stringer.

Check out some of Mick Fanning’s thoughts on thruster vs quad setups as well as why he chooses to change up his FCS II fin sizes.

Mick Fanning explains how he uses his FCS II fins in different conditions.

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Fin Shape

Now that you’ve got the basics and all the lingo for fins, you need to understand a little more complicated aspects about how fin shape can contribute to the overall surfing performance.

Your fin’s shape impacts directly on how your surfboard is going to perform. One way to comprehend this is to use a Single Fin for our descriptions.

When you get down to it, thrusters, quads, side fins are more or less variations of these characteristics just in a smaller version.

Flex is one of these characteristics that can directly relate to fin performance.

Flex will contribute to your projection out of turns, which in turn will produce your speed and effect control. More details on flex will follow, but for the purpose of this article, lets look at how flex and shape of fins go hand in hand.

Lets go back to our longboard and check out how it’s going to perform using 4 different fin shapes.

The Flex Fin, the Rake Fin, the Pivot Fin and the D Fin.

Corey Colapinto of canvas surfboards
Corey Colapinto of Canvas Surfboards getting groovy on some waves.

The The Flex Fin (with maximum flex) is a really versatile fin that can be used in just about anything from shorter stubbies to 10 foot nose riders. These flex fins are going to feature a wider base that really tapers down into a narrow tip and doesn’t offer too much drag. When coming off a bottom turn, your flex fin will give you a tonne of projection.

This reflects what we mention earlier where the more rake you have in your fin, the more you can draw out your turns compared with a rigid upright fin template for more pivot in tighter turns.

The Rake Fin (with medium flex) is the next most flexible and sits between the flex fin and the pivot fin along the spectrum. With a wide base like before but with a little more width in the tip of the fin you can see a fairly vertical base that sweeps back towards the end. This combines nicely the projection and maneuverability of the flex fin with some of the hold you get from a Pivot Fin.

The Pivot Fin (with very little flex) is your standard go-to fin-shape for nose riding. You can recognize this fin by it’s full, vertical outline with a wide base. It’s designed to slow you down a little and help keeps the tail further in the water while you’re up on the nose. You can also still step on the tail and pivot (swing) the board around in a relatively tight radius.

The D Fin (with no flex) isn’t going to be the most forgiving fin or the most versatile to surf. Usually you see these on a more classic, heavier log. A little harder to turn and not as stable when you’re on the nose, this fin is more for getting maximum trim straight down the line.

With a super wide base combined with a super wide tip, these fins get their name from generally appearing in the shape of a D. Sometimes you can find them with a straighter, more vertical forward edge with a curved side aft, and sometimes they’re found with curved edge forward and vertical edge aft.

You would usually place these fins as far back of your board as possible for maximum down the line trim.

Surfboard Fin shape vs surfboard fin flex
Flex your fins! The degree of flex from least flex to most from left to right: The Flex Fin, the Rake Fin, the Pivot Fin and the D Fin.

Surfboard Fins 101

So now you know a little more about fins. With literally an infinite number of surfboard and surfboard fins combinations, you’re going to have a good time testing them all out.

Check out Part Two of our Fins Guide below for a better understanding of materials and construction in surfboard fin design.

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Part Two: Construction and Materials in Fin Design

part two construction and materials

The same way surfboard combinations and design are endless, so are surfboard fin combinations and choices. It’s only through experimentation that the best performing fins are going to be found and with so many aspects like materials, construction, cores and design able to be adjusted, it’s no wonder great discoveries are still being made.

However, while experimentation and innovation are great, there are also some proven design aspects that have stood the test of time, and some things we’ve learned to look for when we’re matching our fins with our surfboards…

surfboard fins being put under pressure by steph gilmore
Australian Steph Gilmore showing the pressure that can be put on your fins and why it’s so important to use high-quality materials and design and construction to improve performance.

Recap of Part 1…

In part one, we talked about flex and fin shape and how they are key elements in making a fin act the way it does.

Flexible, raked back fins for sweeping turns and some projection can be used, or a more stiff and upright fins to give you sharper turns and a quick release. With a wide range of varying degrees in between both.

there are plenty of surfboard fins on the market
Just a few surfboard fin models ready to be experimented with in all types of conditions.

Fiberglass Fins

One of the traditional constructions found is the fiberglass fin. The construction of these fins involve laying up multiple layers of fiberglass cloth and resin and then cutting and foiling the fiberglass fin shape by hand. These fins are strong and can basically be made just as stiff or as flexible as you want them to be.

This type of construction is great for traditional surfboard styles like a mid-length or a longboard . You can make any style of fin for anything from a high performence shortboard temolate to a big heavy D-fin using this method. The attributes of these fins will be as good as your attention to detail when foiling the sides.

Due to their flex properties and lightweight nature, fiberglass fins are a great option for shortboards. However, the drawback is how long they can take to produce and just how much time, detail and attention needs to go into making these by hand.

This is one of the reasons why composite fins are generally more popular for short boards.

different fin material constructions
Some of the FCS fin constructions shown above can influence everything from drive, flex, control and release.

Composite Fins

Composite fins are fins that use more than one material within the construction.

Standard fins that come with most boards are generally made of a basic natural composite.

Once you have all the equipment, it becomes extremely easy to produce a large number of these fins.

The technique for making these fins is called Resin Transfer Molding or RTM. This process involves injecting resin with fiberglass into a mold that results in a plastic like fin that’s both lightweight and strong.

While these are great to produce on mass, you definitely can’t quite get the right flex properties that you want in a fin.

Dave Rastovich talking about how quad setups help his style of surfing; how material can affect both the flex and stiffness of a fin; and how his Rasta Quad Fins incorporate bamboo into the base of the fin to promote strength and extra drive.

G10 Materials

The next progression up from the basic Natural Composite fin would be a fin made using G10 material.

The G10 method is widely used through several industries and uses an epoxy and fiberglass laminate. Fins made this way are both flexible and extremely durable. G10 fins are generally a little more stiff and have controlled flex that results in plenty of drive and control.

So how could fins get more hightech? This is where we start to play around with things like cores and high grade materials like carbon and kevlar.

Performance Core Fins

You can make the core of a surfboard fin out of almost any material you want. The most popular core going around high performance fins at the moment is generally a honeycomb/hexagonal design thats made from lightweight and extremely strong materials. This type of design provides a unique stiffness and flex pattern through the fin in a super lightweight construction.

This process generally uses the standard RTM method mentioned above and has standard fiberglass and resin wrapped around the core.

This performance core style of fin has changed fin development forever. However, it doesn’t end there.

It’s the exploration into ultra high tech materials that make this style of fin progress to the next level.

dion atkinson getting aerial in a big way
Getting your fins out Dion Agius style.

PC Materials and fin flex

Carbon, kevlar and texalium can be used either individually or in combination and provide very different flex patterns.

Different “skins” have different strength to weight ratios and need to be placed strategically on a fin. This results in a wide variety of fin flex patterns.

Each different design, construction and type of material is going to store and release energy generated through your turns or when driving down the line in very different ways.

These kinds of constructions and crazy materials experimentation are generally found in ultra high performance fins and – like we’ve said all along – can be combined in as many different configurations as you can think of.

fcs surfboard fins and futures fins with mick and john john
Mick Fanning with his FCS II dual tabs and John John showing his single tab Futures Fins.

In Summary…

Choosing fins, like choosing surfboards, should be an ongoing thing as your surfing progresses and is nearly unlimited in the combinations you can try out.

The constructions and materials mentioned above only touch the surface of what is possible in experimentation and fin design. There are an unlimited amount of combinations that can be used for the cores and skins of fins that all play around with flex patterns, weight and the strength of your fins.

With all of these various materials combined with foils, shapes, design and everything else, you can see why the experimentation of surfboard fins is going to continue on for some time!

So next time you grab your board and throw in your usual fins, try changing them up. Use something different and you may just find the combination that changes the way you surf forever.

Share your thoughts and experiences about surfboard fins in the comments below! To keep up to date with The Surfers Corner latest articles, make sure you follow us on the Boardcave Facebook Page and on our Boardcave Instagram.

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