Trimming: Equipment & Positioning on the wave
Surfers redirect water flow under their board when they trim on the face of the wave. Appart from the initial drop, this is the way most low-intermediates learn to generate speed at first.
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Think about a longboarder riding the shoulder of a wave, gaining speed by simply moving forward on the board and holding his line down the face. He isn’t gaining speed because of gravitational energy, as he practically stays at the same height on the wave. Instead, he engages more of his inside rail by moving forward on the surfboard and applying some weight over his heels. This is often referred to as “trimming” on the wave’s face.
It’s important to consider that your potential to accelerate by using your rails depends on the equipment you use. A longboard will give you the potential to redirect much more water flow as a lot more rail is engaged in the wave. Therefore longboarders don’t necessarily need to go up and down the wave as much to accelerate. If you are riding a longboard, make sure to check out the “how to cross step” course, as it would be very relevant for you to learn more about speed generation.
Shorter surfboards don’t have the same amount of rail engagement and surface area. That’s why often, just trimming down the middle of the wave isn’t sufficient to keep up with the wave’s peeling speed. Where you trim on the face of the wave also greatly affects how much speed you can generate when trimming.
Surfing a bigger board allows for more speed generation potential, helping low-intermediates compensate for an average pumping technique. Later, once their pumping technique gets better, it is possible to accelerate more easily on a smaller board.
Let’s compare how deep each of these surfboard rails are engaged in the water, according to the shape of the wave.
The “Low surfer” trims at the bottom and his rail is only slightly sunk in the water as the wave’s shape is quite soft here.
The “High surfer” focuses on riding higher on the face, where the wave is steep. Because of the wave’s shape towards the top, his board is more engaged, so more water gets channelled under his board, helping him accelerate more.
If you imagine how both of these surfboards sink in the wave and disrupt the water flow, they would be very different from one another. The surfboard riding high on the wave has more engagement, therefore it gets more acceleration from the water getting channelled towards the tail.