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Surfboard Fins

What Are Surfboard Fins?

Surfboard fins attach somewhere near the tail of your surfboard to give you “traction” in the water, akin to the “skeg” of a boat, although the picture of a rudder may be a more helpful visualization. Fins come in many different shapes, sizes, makes and appearances and allow you additional control over the direction and speed of your surfboard based on the distribution of your weight on your board.

Surfboard Fins | A Short History

Fins weren’t introduced onto surfboards until the 1930s, so a long period in the history of surfing was purely finless surfing. Hawaiians, as the pioneers of surfing, generally chose to ride their olos and alais straight into shore. Without fins, carving was darn near impossible as any attempt would result in a tail slide, and the back of your board blowing out. The only real way to effectively control the direction of your board was to stick your foot in the water, like an oar.

Tom Blake gets credit as the father of the surfboard fin. Legend has it that in 1934, after talking to a boat captain about boat keels, he grabbed the keel of an abandoned, old speedboat and modified it to fit his surfboard. Blake wasn’t initially impressed with the results, but he stuck with it and gradually the concept of surfboards with fins took hold. At first, surfboards only implemented single fin setups, but that didn’t last. Around the 1970s the twin fin setup really blew up when Aussie ripper Mark Richards teamed up with Hawaiian shaping legend Dick Brewer to get the twin fin dialed in. MR captured the benefits of the faster, looser “Free Ride Twin Fin” on his way to 4 straight world championships. The twin fin setup was a competitive success in large part because the competitions had no waiting periods and so the majority of events were held in small, sloppy conditions, perfect for the twin fin’s speed and maneuverability.

The dominance of the twin fin didn’t last long, as it gave way to the tri-fin “thruster” setup. Simon Anderson wasn’t the first person to use three fins on a surfboard, but he pioneered the thruster setup in the early 80s - two fins, one near each rail and both the same distance from the tail, and one fin, centered in the board, closer to the tail than the other two fins. The thruster combined the benefits of the single fin and the twin fin - the stability provided by the single back fin, along with the speed generated by the side fins. Today, the three fin thruster setup is the setup utilized by the majority of pros on the World Championship Tour and the majority of surfers the world over.

More recent fin experimentation has led to even more fin setups, and with the variety available for fin shapes, sizes, materials, and setups, the possibilities are limitless.

Fin Setups | Experimentation And Progression

Single Fin: As noted, the first surfboards with fins implemented a single fin. That explains in part why single fins are associated with retro boards. Single fins don’t allow you to pump to generate speed, as thrusters do, because there are no side fins to generate the drive from pumping.

So with a single fin, a surfer has to rely on what the wave provides, trimming and staying in synch with the power of the wave. That’s not to say you can’t get any speed on a single fin. In a straight line, all other things equal, single fins are faster than thrusters because they don’t have the additional drag created by side fins.

Generally, the single fin acts like a boat rudder; without side fins, you can’t make sharp directional turns, and so a single fin board has a much wider turning radius. The result is long, arcing turns with a focus on smooth style that forces you to stay near the wave’s curl. Soul surfers embrace the single fin. As do longboard noseriders. And Hawaiian big gun big wave surfers. If you ride a single fin, that fin typically has greater depth and base width than fins on other board setups.

Twin Fin: The twin fin setup is known as being fast and loose, with two same-size fins, one near each rail, equidistant from the tail. Compared to a single fin, the two fins on a twin fin give you the ability to make sharper turns, pivoting on the inside fin of your turn. And the twin fins also give you the ability to generate speed by pumping, hence twin fins being known as fast boards, with less drag than a thruster because there is no third center fin.

However, the lack of that center stabilizing fin, as seen with a thruster or a single fin, is what gives twin fins their reputation as “loose” surfboards. This looseness is why twin fin setups are not big wave boards - they may slide out or lose traction in bigger surf. Today, the twin fin setup is most common on fishes and other boards designed for down-the-line surfing on smaller, mushy waves. Dave Rastovich is a modern day surfer known to embrace the twin fin setup.

Thruster: The thruster is the fin setup on the majority of all surfboards on the planet, from shortboards to SUPs, and anything in between. The three fin setup of the thruster captures the benefits of both single fins and twin fins because it is effectively a combination of both of those setups. A thruster, just like a single fin, has one center fin situated near the tail of the board. Like a twin fin, the thruster also adds two side fins, one near each rail, slightly farther up the board away from the tail than the single center fin.

With that setup, the thruster provides the stability of a single fin and avoids the looseness of a twin fin, and also gives you the speed - “thrust”er - generated by pumping. Also, the front of the outside fins on a thruster are typically angled slightly to the inside of the board, known as toe-in, to allow you to generate even more speed. Don’t forget those two outside fins allow you to jam tight turns off the tops and bottoms of waves, too. All these benefits of the thruster are why it’s considered an all-wave setup, hence its popularity. Also, the modern trend in surfing is towards super rippability and boosting airs - the thruster gives the speed and maneuverability to do just that.

Quad Fin: The quad fin setup was developed to fit the niche between a twin fin and a thruster, for those surfers who didn’t want to sacrifice the speed of a twin fin but at the same time add slightly more stability than the twinnie, yet not to the point of a thruster’s single center back fin.

The actual setup on a quad is basically a twin times two, with two sets of side fins on each side of the board, with one fin typically set slightly inside the other one, although closer to the tail. This achieves the goal of retaining lots of speed, while defeating some of the looseness that limits the surfability of twin fins, and so generally quads are regarded also as all wave size boards. Be careful though, the no-back-center fin on quads means you’ve still got an opportunity to blow out your tail in a tail slide. Pros have dabbled in quad fin setups, with an all-quad final between Mick Fanning and Joel Parkinson at the 2012 Billabong Pro Tahiti, and Kelly Slater dominating the final of the 2011 U.S. Open of Surfing at Huntington Beach on a quad.

Five Fin: What about those who like the quad fin setup but want even more stability? You throw a back center fin on top like a cherry and you get the five fin setup (no catchy name, unfortunately). Same as the single fin and thruster, having the back center fin adds more stability to your board and shakes some looseness, giving you some more grip and drive. Depending on the size of that fifth fin, the center fin, you’ll still be able to blast your fins loose for fins free maneuvers, if you’re into that sort of thing. Not surprisingly, Kelly Slater has dominated tour stops on a five fin setup as well, scoring second place finishes at the Quik Pro New York and the Rip Curl Pro Portugal in 2011.

Understanding Fin Shapes And Characteristics

Base: the distance from the front point to the back point of your fin, measured where your fin attaches to your board. The length of your base is a tradeoff on drive vs. turning radius. The longer the base you’ve got to work with, the more surface area you’ve got to contact and push against the water, giving you powerful drive and acceleration. The less contact surface area of a shorter base gives your surfboard a smaller, quicker turning radius.

Height or Depth: how “tall” your fin is, i.e. how far it sticks down into the water while you’re riding. Not surprisingly, a fin with more depth gives your board a greater grip on the water, providing you more stability and control. Take down the depth of your fins and you’ll take down your level of contact with the water, increasing the ability for your board to slide out and your fins to release as you’re pulling a huge snap.

Rake or Sweep: Otherwise known as how far backward your fin extends. Picture a line from the center of the base of your fin out to the tip of the fin - what is the angle of that line? The further “back” your fin extends, the greater the sweep. Said another way - does your fin look more like a mountain or a boomerang? Increased boomerang shape - rake, that is - means more contact with the water and a larger turning radius, similar to the impact of having a larger base. The less the rake, the sharper the turning ability, great for spraying that surfer who always seems to be in your way.

Toe: Toe isn’t a characteristic that the actual fin dictates; the fin box dictates toe. Whether you’ve got a visible center stringer, or have to imagine one, you can see how the angle of your fin boxes compare to that stringer. If they’re perfectly parallel, you’ve got no toe. That’s going to be the case for single fins, or center fins on a thruster or quad fin - they’re perfectly parallel and in line with the stringer. But for twin fins, the outside two fins on a thruster, or the outside four fins on quads or five fins, mostly likely they’ll be toe-in, angled inward, with the back of the fin sitting closer to the rail than the front of the fin. Not to be confused with camel toe.

Cant: Another characteristic dictated by the fin box, cant is the angle your fins lean out from being perfectly perpendicular to the bottom of your surfboard. Imagine your fin hitting your board at a perfectly 90 degree angle; that setup has zero cant. Now imagine the tip of your fin leaning out from where your fin hits your board. That’s cant. How do you get cant? Your fins are straight, so your cant is set by how your fin plugs or fin boxes are set into your board, whether they’re angled out. Generally, less (or zero) cant equals more acceleration and stiffness, and increased cant equals increased maneuverability.

Foil: When looking down at your fin from above, you’ll notice the type of foil it has, that is the shape of its outline. Can’t see it? Think of an airplane wing. The bottom of the wing may be flat, but the top rounded, which when it interacts with air, helps create the lift needed to get the plane off the ground. The shape, or foil, of your fin will affect the way it cuts through water, affecting the drag and propulsion generated by your fin. On a thruster, typically the back center fin will have foil that is the same on both sides, while the outside two fins will be flat on the inside face of the fin and foiled on the outside faces of the fin. Hence, the left and right fin!

Flex: The name says it all, how much will your fin flex side to side? A flexy fin - a fin with flex - can be more or less thought of as the equivalent to a fin with cant, so the results are similar. More flex in a fin gives you more maneuverability and looseness, while a stiff fin with little flex provides stability. Here you might say that flex fins aren’t preferable for beginners, who would prefer the stability that comes with stiff fins. You can see flex in other sports equipment, like golf clubs and hockey sticks whose shafts bend when watching swings/shots in slow motion. The same would happen if you watched fins through a big bottom turn, you’d see how much they flex during the maneuver.

 

Fin Systems | How Your Fins Attach To Your Surfboard

What is a Fin System? A fin system is the way in which your surfboard’s fins attach to your surfboard, which is dictated by the fin boxes or fin plugs on your surfboard. When you look at a fin, you’ll see the main part of the fin, that is the part that protrudes from your board and cuts through the water. And you’ll see at the base of your fin, “extensions” on the fin that insert into the fin box or fin plug on your board that, with a small set screw or two, are tightened to secure your fin to your board.

There are two types of fin systems that dominate the bottoms of shortboard surfboards, and which system you have will dictate what your fin “extensions” look like. If you have the FCS fin system, the extensions will generally be two small rectangles hanging off the base of the fin, separated by space in between, almost like two gapped front teeth. These "gapped front teeth" fit into the fin plugs on the bottom of your board. If you have the Futures fin system, the extension will be a long thin partially hollow “rectangle” that runs the length of the base of your fin that fits into a fin box on the bottom of your board. See the FCS system on the left picture below, and the Futures system on the right.

 

FCS, or Fin Control System, was introduced into the surf industry in the early 1990s as the first removable fin system in the world. Prior to removable fins, all fins were permanently glassed on and so couldn’t easily be removed, interchanged, or replaced. This created problems when traveling, adapting to surf conditions, or replacing broken fins. The introduction of the removable fin was definitely a groundbreaking moment in surfing lore.

Since their invention, the FCS fin system has maintained its lead as the dominant fin system utilized in surfboards, claiming to be ridden by every world champion since FCS was released. But Futures has cemented its spot as the next most common fin system, and entered the conversation at the top of the fin system hierarchy. Each side claims advantages and disadvantages, so you'll have to decide which you prefer, or whether you can tell the difference! And of course, there are other fin systems out there: O’Fish’L, Lokbok, and others.

The point is that, when selecting your next set of fins for your surfboard, you need to know whether you're looking for FCS or Futures fin systems, or something else. Just to be clear, FCS and Futures are the types of fin systems, but they also have their own brands of fins. Yet there are tons of labels out there that make their own fins utilizing either the FCS or Futures fin setups. For example, you can find fins by the Rainbow Fin Company that fit surfboards with either FCS or Futures fin systems.

Rainbow Fin Company was started back in 1968 in Santa Cruz, California, by a group of Santa Cruz surfers who were looking for fins to ride for their own boards and to sell to others in the surfing community. Since then, for over four decades and counting, and through the evolution of fin setups, designs and constructions, Rainbow has been relied on by surfers throughout the country and around the globe to provide them with the perfect fins for any conditions. Whether your go-to is a longboard or shortboard (or a SUP), a single, twin, thruster, quad, or five fin setup, or have FCS or Futures, Rainbow has you and your surfboards covered.

Rainbow’s expertise has been honed over the years by working with surfboard manufacturers, team riders, friends and family. Some of these same riders and brands have been the designers or inspiration for Rainbow’s fins, including the “Gerry Lopez,” the “Chuck Patterson Tiger Shark,” or the “Rusty Rear Quad.” And being located in the Santa Cruz-La Selva area, the Rainbow Fin Company family can test designs year-round. In the age of huge, money-grubbing corporations, Rainbow is proud to remain privately held and family owned, allowing it to pursue the perfection of the surfboard fin as it sees fit, without being beholden to public shareholders or private equity capital!