Fluid Dynamics in Surfing

An ancient fluid displacement theorem applies to vessels moving through water: "to move in water you must move water". The principle applies to vessels such as boats, ships and schooners, which are speed restricted and cannot move fast enough to pass their bow wave.

When higher speed can be attained, water cannot move out of a vessel's path, as demonstrated in the photo above. Water needs time to move, and speed does not allow fluid time to flow. Water becomes somewhat stationary to speeding vessels and supports them on its surface. With speed, the bow wave dissipates and disappears, only a trailing wake is visible. This is referred to as hydrodynamic lift.

Surfers are supported by their speed on water. Water takes on an impermeable characteristic with speed.

Video Tahiti from Below

This impermeable characteristic of water may also cause a surfboard to stop in a high speed poke or pearl dive. A slow or gradual nose poke can be ridden through successfully. A high speed nose poke on a flat bottom nose with high nose rocker, can stop movement and catapult a surfer. This is consistent with the ancient theorem: water is impermeable and unmovable rendering the the surfboard unmovable. The results can be devastating as seen in the clip below.

Video from SurfCityHawaii

We can learn from surfing's history, below is a board from our past.

A surfboard with a boat-like bow can reduce catapulting. In review, one must move water to move in water. A flat bottom pushes water forward in the rider's path, diminishing efficiency and performance. Round and Veed bows push water aside out of the rider's way, increasing performance. Greg Noll, in a clip from Riding Giants, successfully rides out of a pearl.

This was not an isolated incident. These boards recovered from shallow pokes, where modern boards fail. The difference is the amount of rocker and bottom shapes.

Designs from the past can be integrated with designs of the future. The prototype below rides out of a shallow nose poke. The board continues to move where flat bows stop, making it faster and more efficient, when the nose impacts water with speed. A deep pearl dive however; is still fatal.

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