This is a hard question to answer, so I prefer to answer it by explaining the design principles of the fins to help you make your decision. The fact is, it is a very personal decision, since what works for one person won't necessarily work for someone else.
In my opinion there are three important aspects to keep in mind when choosing your SUP fins:
- Base: The base of the fin is the longest part and the part that attaches to the board. The thing to know is that the longer the base, the more speed and acceleration. Likewise, the wider the base, the more stability you will feel in a given direction and the easier it will be to move the board from side to side.
- Depth: The depth is basically the size of the fin, and it relates to how much surface area penetrates into the water. Depth primarily affects control. The more size or depth a fin has, the more control it provides. The smaller the fin, the looser the board.
- Sweep: Sweep is the angle of the fin in relation to the base, and it primarily affects how the board turns and pivots. Fins with more sweep produce a longer turning arc, less sweep offers a tighter turning arc and better response on a wave.
I am a lightweight person, but an a SUPer weighing 80 kg needs more control to maintain the direction of his or her board, which incidentally would not be small. For this reason, such a paddler could use a set of fins with wide bases for speed, and longer depth so as to have more control on the face of the wave. For small waves, such a paddler could use a set of fins with less sweep, so as to make tighter turns.
Another important question is: Quad (4 fins) or Thruster (3 fins)? I can tell you that four fins, which have more surface area in the water, will give you a lot more acceleration, especially at take off. However, you will probably feel like you are slipping in the bottom turns. I like to use quad on fast, tubular waves. What you can't get with a quad is the loose feel when attacking the lip of the wave that you can get with a thruster, which is a lot more vertical. The quad set is good for large waves too.
When you have three fins and want to maintain direction and reduce instability as much as possible, try moving the center fin toward the tail. If you want the board to have a looser feel, move the center fin toward the nose. Larger center fins help you maintain direction when paddling and give you more control on the wave. Having 3 fins of the same size is better for running waves and performing more radical maneuvers, but when you are paddling, the board won't maintain direction as well.
Choosing a set of fins isn't easy. I've talked about fin characteristics and configurations, but it isn't just about design: a lot depends on the size and quality of the wave, the shape of the SUP board and weight of the rider. The best advice I can give you is to try different fin designs so you can compare how they respond to your style, and remember that what works for one person might not necessarily work for someone else.
If you are a beginning SUP surfer, conventional fiber or plastic fins will be fine. As you become more experienced you will start to notice a difference. The more time you spend in the water, the faster you will progress, and it will be easier for you to tell the difference between fins. See you out back!!!