Theory and Physiology of the keels

Being familiar with the basic theory of fins is the basis for understanding their importance and how they work when surfing. Understanding the following concepts will help you decide which fin is best suited to improve your surfing style.

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Model (template)

The template or model is the outline of the keel. Each Patience Fins fin model is based on a template that has been designed for different surfboards and surfing styles.

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Keel size or area

The size or area of ​​the keel is one of the easiest aspects to perceive and that most impacts the development of your surfing. The area of ​​a keel can be described as the amount of area within the outline, or template, of a keel. Additionally, the size of the keel can be determined by the weight of the surfer.

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  • Larger fins or more area = more grip and greater control, ideal for big wave conditions or waves that allow you to draw long lines.

  • Smaller fins or less area = faster riding (looser board) and maneuverability, perfect for medium and small wave conditions with a wall.

Here is a table to choose the size of the fins (Future Fins) according to your weight.

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Keel Bow or 'Rake'


An easy way to identify the arc or rake of the keel is to look at how inclined or swept back the projection of its apex is. The more "swept back" the more tilt it has.

A more technical definition is the angle of inclination or distance that exists in relation to the curvature of the keel to its base.

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  • More arc = less pivot on the tail , that is, the turning angles are greater but we have a lot of stability, perfect for big days with long walls to make wider bottom turns.

  • Less arc = more pivot on the tail (more 'loose') , ideal for less powerful days when we need shorter, faster turns with more aggressive bottom turns.

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Keel flex

In basic terms, the flex of a keel is how much it bends from side to side and how it reacts when subjected to pressure from the force of the water when we move or want to turn.

When we talk about flex we are dealing with two main qualities: 1) how much force is needed to flex the keel (that is, how stiff the bend is) and 2) how quickly and reliably the keel returns to the center or its original position (i.e. its recovery capacity and speed)

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A stiffer keel will have a more responsive and quicker response, while a keel with a lot of flex will often provide a slightly delayed but increased projection.

At Patience Fins, our craftsmanship and materials produce fins with a consistent flex that return to center quickly and reliably, and with this as our starting point, we make each fin design with the optimal amount of stiffness.

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The F oil of the keels

The foil can be described as the contours of the keel when viewed from an "edge" perspective and by looking at it from the front, you can determine how the water flows through it and how the speed and velocity are affected. acceleration when moving through water.

Surely you have noticed how the central fins are symmetrical and convex on both sides, you can also see this in some rear fins of the quads. This shape offers us a uniform distribution on both sides.

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  • F oil flat = balance between speed control and the time it takes for the tail to release between maneuvers.

  • Concave foil (curved inwards) = less drag and therefore more speed and momentum, but it keeps the tail gripped longer.

  • Convex oil (curved outward) = lower speed but the tail is looser between each maneuver, since it is the one that offers the greatest drag.

    Within our collection of fins you can find different foils, 50/50 foil that have symmetrical contours on both sides as is the case with individual fins (single fin) or central fins, or 50/0 foil for twin fins - twinfins where The outer edge is convex and the inner edge is flat to generate greater speed control and more grip in each maneuver.

    However, whatever the proportion of the blade, all Patience Fins are normally not uniform, neither from the base to the tip nor from the front to the back, but rather have a hydrodynamic shape where the center is usually thicker, tapering to size. that we approach the songs.

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    The 'Toe' direction of the keels

    The Toe is the angle of direction at which the side fins point with respect to the center of the surfboard. Depending on the angle, more or less pressure will be exerted on the outside of the keel. A more angled keel results in greater control and maneuverability, while non-toeing fins maximize speed by causing the least amount of drag. water flow.

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    Surf Keel Pitch, 'Cant'

    The Cant is the angle of inclination of the keel towards the edge of the board. Or more precisely, how many degrees from the perpendicular to the bottom of the board the fin is. No camber on the side keels maximizes speed by causing the least amount of resistance to water flow, while some camber on the side keels will give you more control especially during turns.