This episode breaks down the physics of surfing, focusing on how the surfboard interacts with the flow of water to generate both speed and grip. It explains that the surfboard acts as a hydrodynamic foil to create lift and forward thrust, a concept essential for efficient surfing.
Key Takeaways & Tips
Grip and the Rail
The surfboard grips the wave because water flows along the curved surface of the rail, following the curve (water is “sticky”). This attraction holds your board into the wave, not your fins as most people think.
Rail Thickness and Hold
Thicker, softer rails riding on smaller, slower waves will have much more hold in the wave face than a thin rail at high speeds. This is predicted by the Reynolds Number, a calculation used to predict flow patterns in fluid mechanics.
Generating Speed
Speed is generated because the majority of water flowing up the wave hits the bottom of your board and is redirected out through the tail. The board acts as a hydrodynamic foil to create lift and forwards thrust, following Newton’s third law of motion.
The High Line
Taking a Highline (riding across the top of the wave) is an important habit to form because it keeps the bottom of the board perpendicular to the flow of water. This creates the most lift and thrust.
The Bottom Turn
By banking over into a big bottom turn, the flow of water hits the bottom of the board at 90 degrees. This allows the surfer to generate speed when dropping down the face and continue to generate and not lose speed as they turn.
Most Efficient Surfing
The most efficient way to surf a wave is with a gentle roller coaster ride up and down the face. This requires mastering the timing and technique of the bottom turn.
Common Mistakes to Avoid
Trimming on the Bottom
Trimming along the bottom of the wave is the worst place for generating speed because the rail is at a shallow angle to the flow of water, causing the flow to spill off the inside rail.
Shedding Flow
Failing to lock in the inside rail causes water flow to shed off the rails instead of being redirected along the length of the board and out the tail, resulting in lost speed.
Riding Straight
The board must be on rail. If the board is flat or straight, the efficiency of the thrust is lost.