Let’s talk about fins, baby! Everything you need to knowMartijn Ronday
When talking about fins we’re actually talking about fluid hydrodynamics and thus the Navies-Stokes equations. The Navies-Stokes equations govern the motion of fluids, illustrated by the following formula:
Explanation: In the case of a compressible Newtonian fluid, this yields where (u) is the fluid velocity, (ρ) the fluid pressure, (p) is fluid density, and (μ) is the fluid dynamic viscosity. The different terms correspond to the inertial forces (1), pressure forces (2), viscous forces (3), and the external forces applied to the fluid (4).
Meaning: We have no freaking idea! When talking about fins, the laws of hydrodynamics do apply, but lets dumb it down a bit by sticking to the basics of fin design.
All jokes aside, let’s talk about fins, baby!
Fin design elements
OK, so there are just as many fin elements witch determine the characteristics of the fins then there are surfboard elements. Ultimately, the characteristics of the fins in combination with the characteristics of your surfboard, will determine how the surfboard handles.
The following basic fin design elements, determine the characteristics of the fins. This will give you an idea of what kind of fin works for different types of waves and surfing styles. See below for the explanation of these elements.
- Template : shape of the fins, consisting of the following elements: height, base and rake, resulting in fin area. More finarea (bigger fins) equals more hold, less fin area (smaller fins) results in looser fins. Generally speaking, a larger, heavy footed surfer will look for larger fins and a smaller, light footed surfer will like the feel of smaller fins. Fins come in different sizes to accommodate the surfers weight. X-small= under 55 KG/120 LBS; Small= 55-70 KG/120-155 LBS; Medium= 65-88KG/145-195LBS and Large= 80 KG+/180LBS+. Each manufacturer has their own optimum weight range, but don’t deviate from the ones stated above. Plus, it’s more of a kind of guideline, rather than a rule.
Height: height of the fins (how deep the fin penetrates the water). Fin height in combination with the amount of fin area and base will determine how well the fins will hold while doing turns. The more fin area, the more the fins will hold when powering trough gouging turns. If you like a lot of hold, go for fins with more depth, if you like a looser feel, go for smaller fins.
Base: the width of the fin measured at the base (part of the fin that is attached to the surfboard). The width at the base of the fins determines the amount of hold and drive off the bottom. The width of the tip of the fin determines the amount of release (looseness) at the end of the turn or ‘off the top’. A narrower tip offers more release, then a wider tip. The wider at the tip, usually means the fins are better suited for big and powerful waves or just big and powerful surfers.
Rake: the amount sweep of the fin, determent by the amount of fin measured from the rear of the fins. Are you still with me? (check out the picture below). So the more upright the fin (less raked fins), the more pivoty the fins, resulting in quicker direction change while doing turns. This means you can fit more turns in per wave! More upright fins are better suited for in the pocket surfing on beach break style waves. The more raked the fins, the longer it takes to change direction, resulting in more carvier, drown out turns. Fins with more rake are more suited for surfing point breaks or longer faced waves.
Foil: the thickness distribution of the fins or the way the sides of the fins are shaped, determining how water passes along the fins trough the fin cluster. The inside of the side fins are usually flat or have an inside foil (v-foil), while the outside of the side fins have a curved outside foil (like an airplane wing). A flat foil results in a more stable feel (for controlling speed). An inside foil improves the water flow across the fins, offering a looser, faster and drivier feel. This makes rail to rail surfing a little easier, so you can generate speed more easily. The center fin has a symmetrical foil, shaped like the outside of the side fins on both sides of the fins. The rear fins of a quad setup also have a symmetrical foil, resulting is a stable feel through the back of the fins.
Flex, being the magic word: fins are made using different materials, resulting in stronger, lighter and more flexible (or stif
fer) fins. We’ve seen fins made of wood, plastic, fiberglass, Kevlar, fiberglass fabric covered with an aluminum coating (Texalium), performance core, or a combination of all of the above. Al these materials offer a different flex pattern. Flexier fins generate more speed, stiffer fins offer more control. Again, it’s all about meeting somewhere in the middle. So the properties of flex and stiffness can be combined to offer the best of both worlds.
We are even seeing fins with different finished surfaces, like the Darren Handley DHD Shaper Fin. These side fins have: “Dual surface side fins; the inside face of the side fins are high gloss helping the water to slide off the fin faster, while the foiled outside face has a sanded finish creating grip as the water runs over the foil. Essentially this helps to drive off the bottom faster and bite through a turn”. https://www.youtube.com/watch?v=4-pC7MYtIsQ
We wouldn’t mind giving those a try.
Color: just kidding. Although color is an actual design element, but it wont result in a different fin characteristics. So whatever floats your board;)
Quads or thrusters?
We’ll, this could’ve also been futured in our Find your Magic Board blog, but here it is.
A truster (three fins on your board) is the standard fin configuration an surfboards today. Thrusters add stability, control en maneuverability to a surfboard.
A quad setup generates speed and drive and generally add a looser feel to a surfboard, in smaller waves. In bigger waves a quad will add stability and hold. Positioning of the fins also make a huge difference. If the front fins and the trailing fins (the middle fins) are forward and clustered closer together, the board is going to have a looser feel. If the trailing fins are more back (near the center fin) the board is going to have a litter more drive but, will feel a little stiffer.
Nowadays we’re seeing lots of grovel boards (surfboards for small junky waves) come with the five fin option. This let’s you switch it up and find what works best for you.
Choosing the right fins
Each element ads or cancels out characteristics offered by other design elements.
If you’re a bigger surfer, surfing bigger, better waves and like to do long drown out turns, huge carves, 3 minute barrel rides; look for bigger, stiffer, fins with more rake. Because the waves offer all the speed necessary, flat foiled fins are the way to go. Now, if you’re a bigger surfer, who also likes to do some progressive surfing; look for fins with a thinner tip or a less raked fin, but don’t loose the wide base. You’ll need this driving of the bottom so you can take the top of the wave(BAM!)
If you’re a lighter surfer, just look for similar fins as the fins described above, but just in a smaller version. The same go’s for the more progressive surfing.
When surfing smaller waves and like to surf top to bottom, doesn’t matter if you’re a bigger or lighter surfer; check out less raked fins, with more flex and with the inside foil (v-foil). You might even want to try a smaller size fin.
It’s more of a trial by error kind of thing, so switch it up and try to find the right combination of elements, because when found: pure gold!
Last tips about fins
Check out the future fins website.
Future fins and other manufacturers have these awesome fin generating tools on their websites. You can use this tool to figure out what kind of fins are going to suit your surfing and the waves you’re surfing. Because there is so many information about all kinds of different fins, this might point you in the right direction.
Fin day Fridays on Shred Show
Shred Show (Chris likes to call it: ‘the Internet’s most stoked surfboard show!’) is known for giving enthusiastic, in depth breakdown’s on all kind of different surfboards. On Fin day Fridays Chris breaks down all kinds of fins.
Surfboard fins explained by compare surfboards
Benny from compare surfboards breakdown the basics about fins.
Try different fins and fin setups… on the same board… in different conditions
By testing different fins, on the same board, in different conditions, you get to experience the different feel of the fins. Almost every surf shop has a test center where different fins can be tested. You can also check out Finatic about fins. For a monthly fee you can become a member. Pick and choose from different fin sets on-line, they mail you about fins and you can test the fins for as long as you want.