Stand up paddle board fins are an essential part of your paddle board rig. Without your fin your board would start to turn radically with every stroke, making the whole paddling experience pointless. The fin allows you to move forward in a relatively straight line, or “track”. It does this by preventing the tail of the board from slipping sideways as you put pressure on either side of the board as you go through your stroke. The design of the fin also affects speed, stability and how easily you can turn and your board. A fin can be broken down into the following sections:
- Base and Tip: The base is the top section of the fin, closest to the board when installed. It is usually the widest part of the fin and it helps to stabilize the board and affects tracking. The Tip is the other end of the fin that extends down into the water. The tip also affects tracking and speed.
- Leading Edge: The leading edge is the front part of the fin and the angle is the called rake or sweep. The leading edge will affect how the board turns and pivots and also how fast it releases water. The rake also allows the fin to release any weeds that may get hung up on it.
- Trailing Edge: The trailing edge is the back of the fin and it also affects how easily, or not, a board turns and pivots. Trailing edges aid in releasing water to greater or lesser extent, which affects speed.
As a basic rule you want to look at your fin in terms of surface area. Here are the pros and cons for each type of fin.
- A larger fin that has a wider base and a longer leading edge will track better (go straighter) and help stabilize the board making it feel less tippy side-to-side and more predictable in choppy water and swell. On the other hand, a larger fin can feel sluggish because it will not cut through the water as easily. It will also take more effort to turn and pivot the board since there will be more resistance to the flow of water around the fin.
- A smaller fin with less surface area that has a narrower base and shorter leading edge will turn and pivot easier and will allow the board to move more quickly through the water. But, a smaller fin will not track as well as a larger fin and it will be harder maintain stability in choppy water.
A strong paddler, or someone who likes to use a stiff paddle with a larger blade, may benefit from a fin that has a wider base and reaches deeper into the water. This type of fin will offer good resistance to the extra force exacted by the paddler, which will result in the board tracking better. A person who has a more fluid and slower stroke will benefit from a lower-profile fin as it will compensate for the lack of force by allowing the board to move more quickly through the water.
Keep in mind, there are a many different designs out in the real world and not just larger and smaller fins. Fins, like the paddle boards themselves, come in various shapes and sizes aimed at performing in specific ways. Racing fins tend to be larger for tracking purposes, where as surfing fins tend to be smaller for improved turning and tight maneuvering. A lot of fins are designed to track well and be fast. Or, turn easily and be stable. Of course, there is always a compromise and it is up to rider to decide which fin works best for him/her in any given situation.
Paddleboard fins that are used for surf-specific SUPs will have a different shape than the fins used on touring, racing and all-around paddleboards. A surf paddle board can have a two plus one set-up where the center fin is larger and there are two smaller fins, called sidebites, on either side and located a few inches forward of it. This setup can be run with or without the sidebites. The two plus one setup is the most common surf configuration for medium to larger sized SUS (stand up surf boards) boards. Other SUS boards can have a thruster set-up where all three fins are of equal size. And then there is the quad set up that is configured with four sidebites- two of which are located behind the other two and spaced closer together.
The purpose of the sidebites is to channel water through the configuration thereby compressing it and speeding up the flow. This gives the board more power which is essential for riding waves where you need speed to power through your bottom turn and hold the rail in tight against the face of the wave as you move across it. On the other hand, extra fins create more drag in the water, which will decrease your speed if you are not travelling on a wave, which is supplying you with power. This is why you almost never see paddle boards meant solely for flat water use with more than one fin.
If you are looking to get more performance out of your board, then experimenting with different fins is good place to start. You can have several fins that you use for different applications, or you can find one that does a couple of things well, but may not be the best for any one situation. Either way, there are plenty of options to choose from and it will never hurt to try something new.