Any surfer will tell you that fins change the feel and performance of their surf board. Part of the reason surfers are so in tune with their fins is because they are traveling at high speeds (at least when compared to SUP racing) so small changes in fin size and shape are readily appreciated.
At the relatively slow speeds that SUP race boards travel, for the inexperienced observer, it can be more difficult to appreciate the effect that a fin has on the performance of your SUP race board. Once you become a stronger paddler and/or you move up to a narrower/faster board, the importance of your fin selection becomes paramount. As as serious SUP racer, your first order of business is (usually) to trash the fin that came with your board and get something that will complement your size, your board, and the type of racing you do.
Your fin does more than steer you in a straight line
If you try to paddle an SUP race board without fins you will paddle circles. The rails of most SUP race boards are not adequate to guide and/or propel your board in a straight line. A fin is an absolute requirement if you want to move efficiently through the water.
In order for you to maximize the potential of your race board, your fin must be able to counter the forces you apply to your board with your paddle. If the fin is too small, the tail of your board will wiggle and you will lose forward momentum. Conversely, if your fin is sized right, it will offer you 1) more control 2) more side to side stability which will allow you to paddle a narrower, less stable, and, in many cases, faster board. and 3) better tracking which will allow you to go faster because you will get more paddle strokes on each side.
“your fin does more than steer you in a straight line. A properly sized fin gives you more forward drive off each paddle stoke. Increased forward drive off the fin gets you to the finish line faster, fact. Check out the America’s Cup boats. How much forward drive do you think they were getting off their keels? We are no different. Even at the speeds we paddle. It makes a big difference.”
Many flat water SUP racers are riding fins that are too small.
Your first order of business is to get your fin size correct. Remember, if your fin is not large enough to counter the forces applied by your paddle you will lose forward momentum and you will lose speed. If you are paddling the fin that came with your SUP board chances are that it is too small.
In fact, if your goal is to maximize your speed, even if you purchased an aftermarket fin there is still a good chance that your fin is still too small. Many SUP racers are riding fins that are 40-50 in(2) while they should be riding fins that are 50-70 in(2). For reference, we know of at least one very successful female SUP racer, who races and wins on a 58in(2) fin and she weighs less than 130lbs!
According to John Becker, one of the big misconceptions among SUP racers is that a larger fin will increase drag and reduce speed. At the speeds we paddle, the drag created by the fin is minimal. Paddle athletes are, therefore, reminded that the benefits of the larger fin outweigh the minimal increase in drag caused by the larger fin. This is especially true when paddling a modern, narrow, SUP race board.
The trade off with paddling a large fin is that your board will be less nimble in the water. The large surface area, although great for helping you go fast in a straight line, can be difficult to turn. Large fins can be a liability riding the bump, doing buoy turns, or during surf entry.
Unfortunately we know of no good rule of thumb to help you match your weight or board size/width to a fin size. As a general rule, smaller paddlers will require a fin with a smaller volume than a larger paddler but there is no easy conversion/look up table because your ideal fin volume will also vary with ocean conditions (e.g. larger fin with rough conditions to help with stability).
An introduction to the different shapes of SUP race fins.
After you have your fin size dialed in, it is time to pick a fin shape. Whatever fin shape you choose keep in mind that fin shape is always a compromise between speed, stability, and maneuverability. There is no single fin for every application (more on this later). SUP race fins fall broadly into four categories:
Category 1: Built for purpose SUP race fins: these fins are dedicated to do only one thing – maximize your efficiency and speed. If you are even remotely serious about your SUP racing you will need at least one fin in this category. The rake angle on these fins is generally high to help shed kelp and sea grass. The main differences between the individual fins made by the different manufacturers is the flexibility/stiffness of the fins, the foil shape, and the surface area . The two most common shapes in this class that SUP racers are leaning to these days are the keel shape fin (an example is the Keel from Futures Fins) and the more elongated “foil tail” shape (an example is the Triangle Cutaway fin from Futures Fins). The foil is, in theory, designed to shed water and offer more glide. In our experience, different fins of similar size feel different but we are unable to offer you guidance on which shape is the fastest, if a foil offers more glide, or even if one foil design is better than another.
Category 2: Downwind fins: these specialty fins have a very low rake angle which allows you to turn your board from side to side rapidly. An example is the Center Downwind fin from Futures Fins.
Category 3: All around fins: these fins are best described as supersized surf fins. They are the triangular style fin shapes that come with most SUP race boards. They are a compromise design focused on allowing you to paddle in a straight line, surf and turn your board without difficulty. An example is the Laird fin from Futures Fins.
Category 4: Specialty fins: there is a set of fins that are very interesting and are best classified as specialty fins. For example, the Kai Sprint 5 fin from Maui Fin Company and the Jim Terrells sprint fin from Futures Fins fall into this category. These fins will not be your most commonly used fins but in the right race situation they can be worth their weight in gold.
If you are serious about SUP racing, you need three fins – minimum!
In preparing this article, we talked at length with John Becker. John is a veteran windsurfer, kitesurfer, fin designer, and top finisher in pro level SUP racing. Currently he works with Starboard SUP, Quickblade, Futures, and Pro-Lite. His recommendation for all serious SUP racers is that they need to have at least 3 fins on hand to maximize their performance in different conditions.
His recommendation is to have two different size keel shape fins in their arsenal. He recommends his Runner fin from Futures. The John Becker Runner fin (image at left) will be available later this month and be available in two sizes. (link coming soon).
Smaller paddlers should have a smaller keel (approximately 50 in(2) and a larger keel (approximately 60 in(2).
Larger paddlers should have a 60 in(2) keel as their smaller fin and an approximately 70 in(2) as the larger fin.
To round out the fin quiver, John recommends a longer fin shape to use while riding the bump, surfing, or turning such as the Futures Matt Becker Downwind fin.
Editors note: Riding Bumps does not receive compensation from any of the fin manufacturers included in this article.