Surfing Explained: Ep5 The Physics of Surfboard Fins. скачать в хорошем качестве

Surfing Explained: Ep5 The Physics of Surfboard Fins.

In Episode 5 of Surf Simply's animated exploration of surf science, we explore the physics involved with surfboard fins, and which fin configurations work best in what conditions. This episode was written and animated by Surf Simply Coach Will Forster. Season 1 will cover 5 episodes over the next 5 weeks: Ep1: Understanding Speed and Grip Ep2: Generating Speed and Grip Ep3: What is Surfboard Volume Ep4: Using an Online Volume to Weight Calculator Ep5: The Function and Physics of Fins Transcript: I’m going to try to explain the physics involved in surfboard fins, within 4 minutes. Thats approximately 500 words if we average normal speech.  And..GO! Single fin, twin fin, thruster, quad fin, lots of configurations to choose from, but first imagine riding a finless board; slippery, slidy and challenging to control and maneuver. Fins have two functions that contribute to control and maneuverability lacking in the finless board. Function 1: Stability. By adding a fin under the board we have a resistant surface area that will help to stop the board from sliding sideways when in trim across the wave. It also creates a pivot point that the rider can push off when attempting to rotate the board during a turn, without the risk of the tail sliding away.  Function 2: Lift As outlined in previous episodes, the engagement of the rail is imperative to holding our board in trim on the wave face, it contributes to speed generation and our grip, reducing the chance of us slipping down the wave face and losing both speed and position. That’s where the side fins shine, Because as well as providing a resistant surface, they are foiled like an airplane wing, and so generate lift in a similar way. You’ll notice side fins, and airplane wings, are curved on one side and flat on the other. This produces lift in a specific direction, and for fins that direction is towards the wave face. There are two explanations as to how the fins generate lift to help engage the rail in the wave face, Benoulli’s Principle, and Newtons third law. It is yet to be exactly determined how much influence either theory has but we know for sure that the result is lift generated towards the wave face, holding the rider in trim on the wave face. Benoulli's Principle is explained by differing the distance the water travels across both sides of the fin, which creates a pressure difference.  As the pressures attempt to equalize, the high pressure on the flat size pushes the fin and the attached surfboard further into the wave face. Newtons third law however is explained by redirecting the flow of water traveling around the fin away from the wave face, and as every action has an equal and opposite reaction, must then direct the surfboard towards the wave face. Before we move on i’ll mention that all fins are there for function 1, stability. But not all fins encourage function 2; generation of lift. It’s also worth noting that the bi-product of both functions is an increase in drag, that can slow the board down compared to our finless example from earlier. So let’s name a few configurations. Single fins and center fins only offer function 1, they allow the rider to pivot and push off the fin while giving some extra stability in trim. Typically you will find a single fin on longer boards that don’t need help from function 2 as they already have a long rail available for engagement in the wave face, but those long rails could be hard to turn without the big pivot point at the back. Twin fins. Two large foiled side fins, so lots of rail engagement. This explains why we see twin fins on shorter boards or very rounded outline boards, with a reduced rail length in the wave face. All that lift is compensating for the lack of effective rail length. Twin fins can also be very fast in a straight line, since all the drag from the centre fin has been removed. Thrusters. Well. Kind of a best of both functions scenario. The center fin creates a pivot point, offering a rider more confidence to push hard during a turn, whilst still benefitting from the rail engagement the two side fins offer. Quad fins. As per the physics, quads function like a twin fin; 2 foiled fins each side amounting to four in total offering strong rail engagement. Like Twin Fins, Quads function well on short railed boards,  but also excel in unforgiving situations that require extra speed and hold, like big waves, or barreling waves for example. Quads also allow for an easier pivot than their twin fin cousins by creating a gap between the two side fins allowing water flow to release between them during pivoting, reducing the resistance to the turn. Well that was 701 words…so thank you for sticking with me. And until the next episode, thanks for watching.