The Science Behind FinSciences WG2 SUP Fin

I have a sailing background with an interest in performance / racing. As such, I was familiar with the idea of the end plate effect in keeping the wind from spilling out from the bottom of the sail (e.g. deck sweeping foresails, etc.). So when commercial airliners began adding the winglets at the tips it immediately made sense. Fast forward to late last fall when my wife and I were flying back from visiting my in-laws. I had started SUP paddling earlier in the year and quickly gotten hooked. Looking out at the wing of the plane I found myself wondering if adding winglets (an end-plate) to a SUP fin would be beneficial. A few months later I had the thought again, so I began looking online to see if such a fin would be legal in racing. My Google searching lead me to discover that Doug at FinSciences has researched the heck out of surf and SUP fin design, including the use of finlets. The science all made sense, and I was very intrigued. So although I was a little skeptical that a 9.25” fiber reinforced plastic (Lexan) fin could perform as well as my Black Project Tiger fin, I decided to go ahead and buy one. I figured if the science was as good as it sounded that I’d play around with adding finlets to an old solid-carbon carbon fin I had been thinking of cutting shorter. And having a very durable fin for longer, more remote paddles wouldn’t be a bad thing either.

I used Dr. Dyer’s fin testing protocol (Bryce Dyer Looks at SUP Race Fins). Test conditions were completely flat calm on a 290 meter straight line course with a running start of about 15 meters to get up close to test speed before hitting the first mark. Testing was done using a test speed of 5 miles/hour (8 kph) as this is a speed that is reasonably representative of a recreational racer. Strokes per side were adjusted as needed to maintain a straight course. Due to time constraints I was only able to complete 6 trials with the FinSciences fin and 5 trials with the Black Project Tiger. The trials for the FinSciences fin were split, making up the first three and last three test runs to decrease any bias from excitement about a new fin, as well as to minimize the affect of conditions changing over time, fatigue, etc. Speed was reported visually using a Garmin Fenix 2 mounted on the deck of the board. Time, speed, stroke rate, and heart rate (HR) data were recorded using the same device and a chest strap to monitor HR. Number of strokes was counted in my head as the Garmin cycling cadence sensor mounted on my paddle often misses a few strokes. The board used was a 2017 Naish Maliko 14’ X 24”. Foot and hand positions were taped to ensure consistency. Fin location was kept the same for both fins (marked position at the middle of the fin box).

Average speed for each trial was calculated by dividing the distance by the recorded time. Distance per stroke was calculated by dividing the distance by the number of strokes for each trial. Stroke Index (SI) for each trial was then calculated by multiplying the average speed (meters/second) for that trial by the average distance per stroke (meters) for that trial. As I was curious to see if paddling effort (measured as heart rate since I don’t have a paddle power meter) could be factored into the results, I also calculated SI/HR, where HR was the average HR for that trial run.

The Black Project Tiger fin had an average SI that was 1.2% higher than for the FinSciences fin. And when SI was divided by HR and then averaged, the difference was reduced, with the Tiger fin now 0.9% better than the FinSciences fin. A higher SI means that fin was more efficient.

I averaged between 15-20 strokes per side with the Tiger fin compared to 25-30 strokes per side with the FinSciences fin. As I began to feel a little fatigue late in the testing, strokes per side dropped to 10-15 with the Tiger and 15-20 with the FinSciences fin. To paddle at 5.0 mile/hr, I was paddling at 55-58 strokes/min (as recorded on my Garmin watch).

I was surprised that a plastic fin, which is less than half the price of a top end carbon race fin, could be within 1% as efficient. With the FinSciences fin not being as stiff as the Tiger, and with there being a little bit of vibration (buzzing) from the FinSciences fin, it makes me think that if this fin was stiffened up and refined a little bit, it could probably beat the Tiger, one of the winningest fins of the past few years.

Although I just questioned the materials choice by FinSciences, there is a lot to be said for having a durable fin, especially for touring or for long, adventure-type SUP races (Yukon River Quest, etc.). I don’t know of any other plastic fin that comes close to being as efficient as the top end carbon race fins.

The improved tracking was what was most notable about the FinSciences fin. During easy paddling it felt like I could paddle indefinitely on one side just by making subtle course adjustments with my paddle stroke and/or through minor rail steering. I can’t help but wonder if being able to take more strokes per side would be an advantage in a longer race, an ultra- event, or on a long tour where decreasing the frequency of paddle switches might be a real benefit. And since the fin tracks so well at lower speeds vs. many racing fins that are optimized for the faster speeds of competition, the FinSciences WG2 fin will likely be more efficient than the race-specific fins when used for longer distance / slower speed paddling (e.g. around 4-5 mph vs. the 5-6+mph speeds of racing).

I’ve also paddled the FinSciences fin in some gentle-to-moderate current (approx. 2 miles/hr current with some swirling condition) where other fins that track super well (like the SUP Gladiator Fury) have so much surface area that the water pushes the board around a lot. The low surface area of the FinSciences fin means that I could still make course adjustments without changing sides with my paddle. I’ve never been able to do that before when paddling in current with a fin that tracks very well – usually the current overpowers me.