Mark Twain Marveled at a Surfer's Speed / In the 2019 WSL Bells Beach Pro Nose Rocker Kills Speed

May 4, 2019

Mark Twain described a lightning fast surfer:  "at the right moment he would fling his board upon its foamy crest and himself upon the board, and here he would come whizzing by like a bombshell! It did not seem that a lightning express-train could shoot along at a more hair-lifting speed."

 

Surfers speed like lightning on water due to hydrodynamic resistance.  When a surfboard moves fast, water beneath the surfer cannot part to allow sinking.  Speed prevents a large enough volume of water from moving or displacing under the surfboard.  Water cannot move out from under a surfer fast enough, therefore it supports him  Water provides lift by preventing a surfboard from penetrating its surface.  Unlike buoyancy which supports objects by displacement, hydrodynamic lift supports speeding objects with pressure.  Water cannot compress.  Water provides upward pressure or lift with speed.  A speeding surfboard, like a wing, is supported on the surface because it cannot penetrate water very deeply.  The surfboard is a wing on water and through the air.  In both cases upward pressure under the board supports the surfer.

 

Flight has changed surfing.  Hard flat landings push surfboard performance to its limits.  Nose rocker which keeps the board from diving under, can put an unnatural bend in the bottom of the board.  The bottom bend known as a bow in boats, acts as a landing pad for most nose first landings.  When a landing on this bend is flat and hard, hydrodynamic force can push a surfboard back.  Lift transfers to backward force when the rocker bend hits water with speed.  The bottom bend section, where the nose curves upward, can push against the wave.  A flat underside cannot move water out of the surfboard's path and creates a resisting force that can disrupt balance or stop a surfboard.

 

In the Rip Curl Bells Beach Pro Malia hits the lip and free falls down the wave.

 

 

 

 

 

 

Malia lands on the nose rocker bend.  The board immediately decelerates.

 

 

The board stops moving and pitches Malia.

 

 Malia did well and finished runner up.

 

 

 

 

 

 

 

 

 

 

 

John john won the event despite a slow start.  He risks everything and almost completes this ride.  He launches airborne off the lip and falls with the breaking wave.

 

 

 

 

In landing, the tip is visible and above water, but; the rocker bend blocks movement.

 

 

Ryan Callinan almost made the finals with an outstanding performance. 

 

 

Ryan breaks his fins out the back and free falls into the wave face The nose buries on reentry. 

 

 

 

When a nose goes underwater, the board stops due to the same hydrodynamic force on the bottom.  Pressure on top, comes from the rider's weight not water.  Water spills over the top in an eddy, which sprays above the board.  Pictured below, is an enlargement from Malia's ride.  Water eventually covers the board, but it stops before it is engulfed.

 

 

 

 

Ryan's wipeout has similarities to Malia's

 

 

 

A surfboard can transition through a shallow nose poke with less rocker and less flatness in the bow.  A flat bow will do what it is designed to do, produce lift.  Lift pushes the flat surfboard back at high speed.  At low speed a flat bow will displace water.  Surfing has evolved with flight and equipment must also evolve.  Flight produces high speed landings.

 

 

 

 

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