Fins ain't what they use to be!
A long, long, long time ago in a lifestyle far removed, the waves were surfed by stub toed Polynesians on big heavy boards made out of trees (I know, trees? Hilarious!) And the only method for guiding/ steering the logs shoreward was hanging your trailing foot over the edge of the board to act as a rudder! Blooming heck!!!
A good example of this technique can be viewed in the cult classic, hardcore surf movie 'North Shore'. Imagine catching your "fin" on a submerged reef pinnacle or rock?!!!
These days, however, we are much more fortunate than those historical pioneers and no longer need to smash our toes to bits by guiding our surfboards with our feet (for all the beginners out there, that's what fins are for) and we no longer ride trees.
For the modern day surfer, we are faced with a variety of choice which often seems infinite and mind bogglingly confusing! This is especially so, when it comes to considering what type of fin/ fins are best and where to place them on which type of board...
Being an idiot, I consider myself appropriately qualified to put together this morons guide to all things 'fin', just so I can remember what's what and why's why!
When considering the way fins work there are many variables that account for differences in performance including:
Fin Placement -
Fins are generally marked from the tail of the board to the back trailing edge of the fins.
Toe - (Possible historical reference to above mentioned submerged reef pinnacles)
The side fins are slightly facing towards the nose.
Cant - (Possible historical reference to our surfing forebears exclamations of pain when colliding with above mentioned submerged reef pinnacles)
The tip of the fins point out.
Foil -
The actual hydrodynamic shape that allows the fin to move smoothly through the water similar to a plane wing through air. (Only much wetter)
All of the above are technical details and hold more meaning in the mystical realms of the board shaper and designer and are of little concern to the idiot, more importantly for us the following can guide our decisions to fin purchases and fin use.
The majority of the following description is based on longboard fins but the theory is pretty much generic. There are basically four things to think about...
1. Base length of the Fins: In general larger fins provide more stable forward drive. This is especially true for the base length, where the fin attaches to the board.
2. Flex: For beginner/intermediates, going for more flex fins will provide forgiving turns. More rigid ones tend to give quicker turns.
3. Height or Depth: Fin makers measure the fin using the length perpendicular to the bottom of the board. The longer the fins, the more contact they make with the water under more conditions, but you trade that in by needing to work harder to make turns.
4. The placement: Where the fins go, has a lot to do with the idea of finding the 'sweet spot', like on a tennis racquet. There will be a spot where you place your back foot that gives you the best turning responses. A big spot is best because you don't have to be in the perfect spot to get the responsiveness you want to have.
Which Fin?
If you weigh 80kgs or more, you would want to go a notch higher in the fin size. Conversely, smaller people do not need to have bigger fins. Also if you are attacking larger waves then you want to maximize the fin contact and that's when you tend to choose longer fins.
Longboards have traditionally been single finned, but many modern boards have tri-fin setups with a large middle fin and two small side fins.
When buying a board, the most versatile setup is two side boxes for the small fins and a large box in the middle. This way you can switch around, if the fancy takes you, to a smaller or larger middle fin with or without side fins.
A long fin helps keep the board from spinning out or side slipping but it will also effect the looseness during turns. 8-10" will probably do fine for a single fin and tri-fin can go from 4-8" centre fins with 3-4" side fins. A lot of fin area will stabilize the board, but it will limit the looseness of the turns.
Cutaway fins are relatively narrow at the base compared to the tip of the fin and are far looser than full fins. The shorter the fin, the less drag in turns, as well but at some point you risk spinouts especially when nose riding.
High turns on a steep wave will cause the fin to pop out of the water resulting in a spin out too. Though if you can hold on and save a spin out, you'll look like a pro surfer and can eventually work these into 360's or helicopters (oops sorry dreaming again!)
Subtle changes (1/4") in fin position can make a big difference. Moving the middle fin forward in the box will help with trim speed and help loosen up the board. Unless you put it so far forward that you must do more rail turns (on the softer part of the rail) than fin turns and the board may also spin out more often. Moving the fin back will increase stability to help with nose riding.
Most single fins are placed a little farther back than the middle fin on a tri-fin setup. The reason being it's the only fin you've got and if it is spinning out on turns or while you're on the nose you generally lose control.
On three finned longboards, the more you move the fin towards the side fins, the looser the board will be (for small waves), towards the back the more it will hold in and draw out your turn (for bigger waves).
Using a big retro fin with side fins may be counter productive, as you would have too much total fin area, more than you need, and thus causing needless drag.
If you're into nose-riding, go with a big middle fin only. Side fins create wobble when you're up on the nose, and this is even more the case when you have a smaller centre fin like in a standard thruster setup with three fins of equal size. The bigger and farther back in the box your centre fin is, the more it will anchor the tail of your board in the curl of the wave.
The side fins work because they are toed-in which causes drag, which causes tail lift getting you into the wave earlier. They also loosen up a board by putting higher pressure on the outside edge of the fin and helps keep the board from tracking (heading straight in), and makes boards react quickly and appropriately to direction changes. All this lift and drag causes the board to be slower and more difficult to nose ride as the tail will want to release from the wave.
The side fins on many longboards are angled very little, which means they act just like increased area on the centre fin would. In fact, many longboard side fins seem to be a fashion accessory, and do nothing to improve the performance of the board that a larger centre fin wouldn't do. Also side fins on big guns are nearly parallel to the centre fin-they're strictly for straight ahead stability, not accelerating in turns.
So there you go, all fins being equal I fin(k) I have managed to (re)fin(e) a whole lot of fin(gs) I have thought about, looked up, scribbled down over the years into (some)fin you fin(d) fin(e). BaaBoom!
Words by Kev Child
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