A surfboards performance can be tweaked by altering your fin configuration and fin type. Fins have three basic objectives, those being drive, lift and hold.
What is Drive?
Drive refers to acceleration. Put simply, fins help a surfer turn and come out of a turn with speed. How? Well when a surfer is making a turn, in the middle of this move they will apply pressure on the fins. This pressure makes the water surge, catapulting the surfer out of the turn.
What is Lift?
This means the pressure or force on fins that, when applied, it returns lift (vertically).
What is Hold?
This means the ability to prevent the surfboard from sliding during turns or similar manoeuvres.
A single fin is typically seen on longboards and provides speed (in a straight line), hold and stability for nose riding. When engaging in a turn you will typically feel a delay, however the turn is very smooth. The single fin is a great setup for those who want to glide and trim.
The Twin Fin is a two-fin set-up. With two working the board, you will find that it increases speed and maneuverability. One fin placed on each side will give the rider more stability than a single fin set up. A twin fin setup has little drag because there is no center fin. Although there are some advantages of this set up, a weakness usually comes down to the fact that it can loose control easily.
The Thruster Set up
The thruster setup incorporates 3 fins (of equal size). To put it simply, this is a single fin set up and a twin fin all in one. Like the twin fin set up, it provides stability and drive but also give the rider more hold because of the centre fin. This set up is usually preferred in high performance boards specifically for manoeuvrability or doing surf tricks (like aerials or just riding the wave vertically). This fin configuration is the most conventional and functional fin configuration.
The Quad Set up
The Quad setup utilises 4 fins, 2 placed on each side of the board which means more hold. Like the twin fin, it provides speed, hold and manoeuvrability however with those extra 2 fins in place, it gives the rider more control and responsiveness (more fins help the surfer to direct the board). The quad is also quite loose. This is because there is no middle fin (like a thruster).
A 2+1 setup incorporates 3 fins - 1 large centre fin with two smaller side fins. The centre fin will provide maximum stability whilst the two smaller side fins will provide extra control and manoeuvrability. This fin configuration is typically found on mid length boards.
Adjusting a single fin
As a rule of thumb, adjusting your middle fin should be done slightly until you get your desired performance outcome (i.e less slip, more hold). There is really no exact measurements to apply but good practice would be to move the centre fin approximately ¼ of an inch either back (towards the tail) or forwards (towards the nose) until you get the feeling you are looking for.
A good starting point would be to place the centre fin all the way back (towards the tail), test the performance, then move it forward until you are happy. Generally if you feel the board slips too much on turns, then start moving the fin back towards the tail again. I fit is too tight and you would like it to feel looser, then move it forward a touch.
All fins are classified by base, depth, area, sweep and foil. In order to chose the best fin for you, it’s important to understand how these characteristics can change the performance of your surfboard. Each of the following fin characteristics allow you to evaluate the impact that a fin design would have on your surfing.
UNDERSTANDING SURFBOARD FINS
Depth is the distance the fin penetrates into the water. Depth directly relates to hold. The greater the depth the more hold, the shorter the depth the more a board will slide and release.
Base is the length between the leading and trailing edge where the fin meets the board. Base is primarily linked to drive. Fins with a longer base will offer substantially more drive and acceleration.
Sweep is the angle measuring how far the outline of the fin is curved backwards; also referred to as rake. Sweep has a direct influence on pivot. Fins with more sweep produce a longer turning arc while less sweep offers a tighter turning arc.
Flex refers to the bend of the fin caused by lateral pressure during a manoeuvre. Fins with less flex have more response, speed and drive. Fins with more flex are more forgiving and offer a whipping sensation.
Cant refers to the angle of the side fins measured from a vertical line perpendicular to the flat bottom surface of the board. Less cant produces faster acceleration and a stiffer feel. More cant will increase manoeuvrability and gives the board a loose feel.
refers to the shape and geometry of the inside and outside faces of the fin. Foils directly affect the flow of water over the surface of the fin. Different foils create variations in water flow and have a direct link to the overall performance of the fin and the board.
Choosing the right fin size is extremely important considering these are the accessories that provide you with Drive, Hold and Lift. As a starting point, you have large fins and small fins. Each serve a certain purpose.
You would usually decide to use large fins if you:-
- Are a heavier & strong surfer;
- Have a surfboard with a lot of rocker or a wide tail;
- Want to give your board more drive
You would usually decide to use small fins if you:-
- Have a board that has a flat rocker;
- Have a board with thick rails or a narrow tail;
- Want to make your board loose
If your board is feeling too stiff, try using smaller fins or fins with less sweep or more flex. If your board is feeling too loose and lacking drive, try a bigger set of fins, a stiffer flex fin or a fin with more sweep. Generally a lighter person requires less fin area to provide enough hold on a wave. Boards with a lot of rocker may require fins with greater area, more depth or sweep. Boards with deep channels in the tail require less fin area. Boards with wider tails require more fin area than those with narrower tails.If you are using a small board in big or powerful waves use larger or more swept fins.