SUP Fin Science 101: Terms and Design Fundamentals

Defining a few basic SUP fin terms will help you understand some of the parameters we work with when designing and optimizing fins for a range of uses. No single aspect of a fin should be considered in isolation. For example, we can make a short fin which offers high levels of tracking and stability compared to several bigger fins.


Fin depth is measured by taking the vertical depth of the fin, irrespective of its rake angle. Deeper fins will help with stability but are not ideal for shallow water.


Fin length is calculated by measuring the length of the fin, irrespective of rake angle. Typically, longer fins offer more tracking and stability than shorter fins. Those new to racing will want a longer fin, while experienced and professional paddlers will benefit from shorter fins.


SUP fin rake can be measured in two different ways. The leading-edge rake angle is an important consideration for shedding weeds and seagrass. Meanwhile, the fin rake helps to explain how a fin will turn and perform at speed. More upright fins are great for fast buoy turns, while more laidback fins will help with carving on downwinders or in the surf.


SUP race fin area is the total surface area (projected) of the fin measured in cm² or in². A general rule of thumb is that more surface area increases tracking but also drag. But smaller is not always faster, you may feel fast but go too small and you’ll start ‘wagging’ the tail of your board and find it hard to track straight.


The most important aspect of fin design (and production) is the foil shaping. This determines how the fin interacts with water molecules and how that influences the board in a range of ways. Foils influence tracking, turning, handling and speed.

It’s a common misconception that thick foils are slow and thin foils are fast. Thin foils with little or no shaping are usually the result of a company trying to cut production costs because they require less materials and are easier to manufacture.


Fin cord is the distance between the leading and trailing edge of the fin. Increased cord helps tracking and stability, while narrower cords help to increase pivot ability for fast buoy turns.


SUP race fin construction is a very important aspect of fin performance. SUP fins are made from a range of materials including plastic, fiberglass and carbon. Carbon fins are the lightest, stiffest, most expensive and offer the highest performance, while plastic fins are the cheapest and most flexible, but also very durable.

Black Project SUP fins are made using our Carbon Infused LiteCore Technology which maximizes performance and minimizes weight, while remaining durable for excellent longevity.