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Shortboard Fin Guide

From Simon Anderson's initial development of, and competitive success with, the thruster in the

early eighties through to its complete dominance in professional shortboard surfing today it's easy to imagine that any debate over the best competition setup has long since been put to bed. But in the water and on the beach there's seems to be more interest

than ever in the 'next big thing'.

Perhaps it's simply that after twenty years something new feels a long

time coming, but talk of quads and other variations on three, four, five

or more fins seems to be igniting increasing debate, interest and occasional hostility amongst a

great range of surfers. Couple this

with an ever increasing amount of money spent on fin research, design

and marketing and add in the ease

with which surfers with a modern fin system can swap their setup around and we thought it might be worth putting together a few words aimed

at cutting through the hype and delivering a little of the facts you need

to choose your next set of fins.

Some Basics

What are your fins doing? How do they do it and why should you care?

The very first thing you want from your fin is a bit of direction, something to keep the nose of the board pointing towards the beach or down the line, rather than spinning round under you. To achieve this the shortboard fin works exactly like the feather flights on the back of an arrow, providing drag to keep the back of the board running slower and particularly to massively increase that drag if the board starts slipping sideways. To do this you really only need one big old keel fin slapped in the middle of your board.

The second purpose of the fin is to give you 'drive'. This terms gets shrouded in mystery and described in reverent tones but basically it's the simple business of changing your slip slide down the face straight towards the beach into down the line energy that can put you where you want to be on a wave and keep your board travelling forward. Generated during and out of a turn and in even the most basic situation, as you sit in trim heading straight down the line, water isn't just rushing under your board straight along it's length, it's also flowing up the face of the wave. Allowing you to tap into this energy and translate it to forward motion is a vital part of the fins role.

As well as keeping the board running straight your fins give something to pivot against on your back foot during a turn. The subtleties of rake and cant (see below) can change this experience, alter the ease with which the board can be moved from rail to rail and alter the speed and projection that can be generated out of a turn. The size of the fins and their setup also alters the moment of release that allows a powerful turn to break the back of the board out and slide it sideways when that's what you want, or keep them locked in when you don't.

Grab your shortboard now and check out the fins. The centre fin in the back should be curved slightly on both sides. This fin is 'symmetrical', now check out one of the outer fins and you'll see one curved side and one almost flat. The third purpose of your shortboard fins is to use these 'asymmetrical' outer fins to create 'lift'. Lift kind of implies something floating the tail of the board up out of the water, it'll make more sense when you realise that these rear fins, curved on one side, are working exactly like an aeroplanes wing. The 'lift' here isn't up in the air, it's pulling the board towards the rail, locking the rail in and ensuring that the faster the board is travelling the stronger the bond. In practise this means your thruster should be able to take a higher, more critical line in steeper sections of the wave.

Fin Terminology
To understand what you're buying or read more about how fins work you need some basic terminology, the following diagrams run through the terms used to describe the difference from fin to fin and how these effect your ride:

Designing for the Future

If being able to throw together a bit of physics and some terminology and diagrams kind of makes it sound like the scientists have it sown up it's never that simple. No surfer is interested in just running straight down the line everytime, and we rarely surf perfect, machine like laboratory waves so your fins are doing all the above and more as you turn the board through the wave. It'd be easy to assume in an age where computers control everything that a few facts and figures could be keyed in, a model run and the perfect fin design spat out the other end. In fact the complexities of what's going on under your board as you put it through a turn are impossible to predict properly. Although water tanks and computer design are increasingly used, fin design, like most surfboard design and like mother nature itself relies principally on an evolutionary approach. From George Greenoughs first inspired designs based losely around a tuna fin to the latest FCS creation the basic principle is make something new, give it to a great surfer, get some feedback, tweak the design and keep going. Modern fins are tested like this time and time again by top surfers to refine their performance.

Fins and the average surfer

A set of fins might not change your life, but the right set of fins on the right board will help you to surf your local waves to the best of your ability. The choices are endless and, like fin design itself, the best method is trial and error. Swap out your fins with a mate for a sesh, borrow a test set and see how it works for you. If you want to try something completely different as an experiment in smaller surf try riding your thruster with just the side fins, or with just the centre fin: it's not going to give you a competitive edge (!!!) but it will give you an idea of just what a difference the three little bits of fibreglass on the back of the board can make.

Just check out this clip of Jamie O'Brien surfing without fins:

Jamie O'Brien Clip

Some Basic Guidelines

So what should you look for in a new set of fins. The following basic rules are direct from the guys at FCS:

• Generally a heavier person requires more fin area to provide enough hold in a wave, a basic guide is; smaller surfer = M3, medium sized surfer = M5, larger surfer = M7.
• A particularly strong or powerful surfer should use a bigger fin that others in his/her weight range
• A smaller fin, or one with less sweep (more upright) or more flex, will loosen a stiff board.
• Conversely, to give a loose board more drive, a bigger, more swept or stiffer fin selection will work.
• To make a board more forgiving, select a fin with a high amount of flex (K-Flex), for a more responsive choose a stiffer fin (PC or PG)
• A board with a lot of rocker may require greater area, more depth or sweep than a surfer would usually ride in flatter rockers.
• Boards with a lot of rail (eg guns or long short-boards) require less fin area.
• Boards with deep channels in the tail also require less fin area.
• Boards with wider tails require more fin area than those with narrower tails.
• If you are feeling a little under-gunned, and want a small board to work in waves that are too big or powerful for it use a larger more raked set of fins.
• Changing fins can change the way your board feels, and can freshen or improve your surfing.

Conclusion

No real conclusion here. An understanding of some of the facts should leave you able to cut through the hype and enough to realise that changing your fins will change your ride. Experiment to find out what works best for you...

Thanks to FCS Fins for the images, 'terminology' and 'basic guidelines' sections of this article.