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The Definitive Surfboard Fin Guide

by Boardcave on April 29, 2015


Fin Basics

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

Some more advanced stuff…

Fin Shape | Construction and Materials in Surfboard Design

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

Choosing the right fins for your surfboard

The fins you use in your surfboard play a big role on how the board will perform for you. Some claim that your choice in surfboard fin makes up almost 40% of the boards performance. Different boards or different conditions require different fins and fin set ups to work in the way that the shaper or the rider intends them to.

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

But before you start testing out these options, it’s good to have an understanding of how each characteristic can impact on your performance. So lets start with the basics.

otis doing gnarley cutbacks with his gorilla fins
Otis Carey getting his Gorilla Surf Fins out of the water.

Fin Size

The overall size of the fin will make a big difference in the performance. A larger fin will have more hold and provide more control in bigger surf, where a smaller fin will be loose and somewhat more forgiving, but lack the drive and control needed 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 base is the part of the fin that is attached to the board. A wide, or long fin base will help to produce more drive and will allow you to draw out your turns. A narrow, or short fin base will be a little easier to turn, but will produce less 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 depth of a fin is how tall, or how deep into the water the fin goes from the bottom of the board. A deep fin will have more hold and stability, whereas a shallow fin will provide more release when throwing your tail around in turns.

Surfboard Fin depth or surfboard fin height explained with creatures of leisure
The Mitch Coleborn Large fins (left) obviously have a greater fin height than the Mitch Coleborn Small fins (right).

Fin Rake

The rake of the fin is how far back the fin tilts or sweeps. The more rake you have in your fin, the more drawn out your turns will be, and are preferable on bigger days or when there is a long wall to work with. An upright fin will pivot a little more and will be more useful on weaker or junky 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 foil of a fin is the aerodynamic shape of the fin from front to back (much like an airplane wing), and help to create some lift under the board. Fins are usually thicker around the center and taper out towards the edges. There are a few basic foils and many variations of these. Side fins (found on twins, thrusters and quads) are usually flat, or sometimes curved inward on the inside, with it’s foil on the outside. Center fins usually have equal foil or double foil, on both sides. Usually found on single fins, the center fin on a thruster, or sometimes the rear fins on quads and some keel fins on traditional fishes.

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

The cant of a fin is the outward angle of the fin in relation to the bottom of the board. A fin set up with zero cant (straight up and down) is faster in a straight line, but not very responsive through turns. The more cant the fin has (to a degree) the more responsive through turns. This helps keep drive up when the board is tilted and on 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 fin set up is the angle of the fin pointing towards the center of the board. Common on the majority of side fins, the toe of the fin helps to create pressure on the outside foil of the fin, allowing the surfer to have a more responsive “feel” with the fin or the board.

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

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Fin Shape

Now that you have the basic’s and the lingo down for what you are looking at when choosing fins, let’s cover how the fin shape contributes to the overall performance of your board.

Fin shape has a lot to do with how a board is going to perform. The best way to break down the basics is to use a Single Fin for our descriptions.

When it comes down to it, quads and thrusters are more or less variations of these characteristics but broken down into smaller versions usually with very similar total area when grouped together.

Much of a fins performance is going to be directly related to flex.

Flex contributes to projection, which in turn produces speed and control. We will go more into detail about flex soon, but for the purpose of this section and in particular reference to single fins, flex and the shape of a fin go hand in hand.

Lets take a longboard out as an example and have a look at how it will perform with 4 different fin shapes:

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

noosa longboards surfing image sam crookshanks
Sam Crookshanks of Noosa Longboards reminding us how to enjoy our surfing.

The Flex Fin (maximum flex) is a very versatile fin that can be used in everything from short stubbies and mid length hulls, to 10 foot nose riders. They usually feature a wider base, tapering down to a narrow tip and offer very little drag and a lot of projection when coming off a bottom turn.

The more raked back the fin, the more drawn out your turns will be; whereas the more upright, the tighter you can turn.

The Rake Fin (medium flex) kind of splits the difference between the Pivot and the Flex fins. A wide base but with more tip than the flex fin, and usually starting out fairly vertical then sweeping back a lot towards the end. These provide more projection and maneuverability than a Pivot fin, but still allow you to get the tail to hold when you are up on the nose.

shapers fin series
The Shapers fins brand have had a huge year with some rad single fin options available.

The Pivot Fin (very little flex) is the standard go to template for nose riding. The feature a full vertical outline, wide base and are designed to slow you down and help keep the tail in the water while you are up on the nose, yet still allow you to step on the tail and swing (pivot) the board around in a relatively tight radius.

The D Fin (no flex) is not the most versatile or forgiving fin to surf. Usually found on more classic, heavy logs, they are harder to turn, and a little less stable while up on the nose. If you are looking for maximum trim straight down the line, however, the D Fin is for you.

They feature a super wide base, a super wide tip and are generally the shape of a D. Sometimes they are found with the straight vertical edge forward and curved side aft, and sometimes they’re found with curved edge forward and vertical edge aft.

These fins are generally placed as far back on the board as possible for maximum down the line trim.

Surfboard Fin shape vs surfboard fin flex
Just how flexy is your fin? Most flex to least flex from left to right: The Flex Fin, the Rake Fin, the Pivot Fin and the D Fin.

Surfboard Fins 101

So there you have it. A starting point for understanding fins. Like I mentioned earlier, there are literally an unlimited number of fin and board combinations for you to test out in different conditions.

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 2 – Construction and Materials in Surfboard Fin Design

part two construction and materials

Just like surfboards, there is an unlimited amount of innovation possible when playing around with fin combinations. Materials, construction, cores, designs… there is no wrong way to build a fin and experimentation is what leads us to great discoveries.

There are, however, proven designs that work and have worked for years. There are also, proven elements that we like to look for when it comes to fins and surfboards…

surfboard fins being put under pressure by steph gilmore
Steph Gilmore showing just how much pressure can be put on surfboard fins and why high-quality materials, design and construction are all so important to performance.

Recap of Part 1…

Like we discussed in part one, flex and fin shape are some of those key elements that make a fin act the way it does.

Some people and some set ups prefer or require a more flexible, swept back fin for sweeping turns and projection – others prefer a stiff upright fin for sharp turns and quick release. Not to mention the various degrees between the two that can be used.

there are plenty of surfboard fins on the market
There is no shortage of surfboard fin models ready to be experimented with in different conditions.

Fibreglass Fins

One of the more traditional methods of fin construction is to layup fiberglass panels and cut and foil the fin all by hand. A fiberglass fin is strong, and can essentially be made as stiff or flexible as wanted.

These are still the go to for a more traditional style of surfboard like a mid length to a longboard. You can easily foil yourself a flex fin, rake fin, pivot fin or D fin using this method, and the flex properties will be as true as the quality of your attention to detail when foiling both sides.

Fiberglass fins are a great option for shortboards due to their strength, light weight and great flex properties. However, they can be time consuming to produce and, being hand-foiled, need that extra time and attention to detail.

You will find that as you start moving into fins for shortboards, etc. composite fins become more popular.

different fin material constructions
Fin materials and construction can be used to influence drive, flex, control and release in your surfing. Some of the FCS fin constructions are above.

Composite Fins

Composite fins are essentially any fin that combines two or more different materials within the construction.

The standard fin that comes with most boards is made of a basic natural composite.

It’s easy to produce many consistent fins in a short period of time using this method – once you have the equipment that is!

This style of composite is made using a technique called Resin Transfer Molding (RTM) where resin is injected into a mold with fiberglass. This results in plastic like fin that is lightweight and strong.

The drawback, however, is you can’t quite get the flex properties, you’re going to want in a fin.

G10 Materials

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

G10 is a widely used method in a number of industries, and is essentially a certain grade of epoxy and fiberglass laminate. Fins made with the G10 material are extremely durable and very versatile. They are usually a little more stiff with controlled flex, resulting in a fin that has a lot of drive and control.

Now here is where the fun beings. We start to play around with cores and other materials such as carbon and kevlar.

Performance Core Fins

You can essentially make you core out of any material you want. The most common core you will find in high performance fins is a honeycomb or hexagonal one made from a very lightweight but extremely strong material. This will provide a unique stiffness and flex pattern in a super lightweight construction.

The standard set up for this core is using the RTM process mentioned above, with standard fiberglass and resin wrapped around the core.

While the performance core design has changed fin creation forever, it is the use of some pretty high tech materials that really take this style of fin to the next level.

dion atkinson getting aerial in a big way
Dion Agius showing us how to get your fins out.

PC Materials and fin flex

The use of carbon, kevlar, texalium, individually or all together can result in very different flex patterns.

All of these different “skins” have different strength to weight ratios. This means that when they are placed strategically on the fin, the result is a wide variety of different flex patterns.

Basically, each construction with different materials is going to store and release energy generated in turns and 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.

The combinations are just about endless!

fcs surfboard fins and futures fins with mick and john john
Mick showing off his FCS II dual tabs while John John is a single tab Futures Fins man.

In Summary…

Choosing fins, just like choosing surfboards, provide you with an almost unlimited amount of experimentation and potential.

The materials and constructions touched on above only brush the surface on what is possible. There is essentially an unlimited amount of combinations to use for cores and skins of a fin, that all experiment with the flex, strength and weight of the fin.

Combine all of these element choices with the variety of shapes, foils and designs, and you can only imagine what is to come for the future of surfboard fins.

So next time you go to throw in your usual fins, change it up, try something weird. You may just find that combination that changes your surfing 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 Australia Facebook Page and on our Boardcave Instagram.

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