“Kitesurfing” is a popular style of kiteboarding that’s specific to wave riding. Anywhere there is a body of water with waves and the wind blows, on any day, the sky above beaches can be littered with colorful hyperbolic shapes floating above the surface of the water. And from time to time, pulling their human cargo out of the water for long or short jumps.
There are different styles of kiteboarding, including freestyle, freeride, downwinders, speed, course racing, wakestyle, jumping and kitesurfing in the waves.
But, as in my case, my eyes were attracted to the arching shapes of the sail portion of these recreational crafts. On the beaches near Kahului on the island of Maui, we often see the kites above the trees lining the beach at Kanaha. They bob and weave above the trees, always in constant motion. The colors are wide in variety and vibrant in the bright sun.
Modern day kites are made from a fabric known as ripstop nylon. The kite, or sail is attached to a control bar that is held by the surfer. These lines are made of a material with a high tensile strength, frequently ultra-high-molecular-weight polyethylene, in order to handle the dynamic load in unpredictable wind while maintaining a small cross-sectional profile to minimize drag.
The flotation device is a small composite, wooden, or foam board. There are now several types of kiteboards: directional surf-style boards, wakeboard-style boards, hybrids which can go in either direction but are built to operate better in one of them, and skim-type boards. Some riders also use standard surfboards, or even long boards, although without foot straps much of the high-jump capability of a kite is lost. Twin tip boards are the easiest to learn on and are by far the most popular. The boards generally come with sandle-type footstraps that allow the rider to attach and detach from the board easily; this is required for doing board-off tricks and jumps. Bindings are used mainly by the wakestyle riders wishing to replicate wakeboarding tricks such as KGBs and other pop initiated tricks. Kiteboards come in shapes and sizes to suit the rider’s skill level, riding style, wind and water conditions.
Flight is the physical principle in which an object moves through the atmosphere. But for an object, like a bird, or a flying squirrel, or even a human, there must be some method of propulsion to gain enough height to glide, or continue on a sustained trajectory. To do either, an object must generate aerodynamic lift (Bernoulli’s principle) propulsive thrust, buoyancy or ballistic movement.
Daniel Bernoulli was a Swiss mathematician and physicist, born in Groningen in the Netherlands, into a family of distinguished mathematicians.
Daniel studied medicine in Basel, Heidelberg, and Strasbourg, and earned a PhD in anatomy and botany in 1721.
He is best known for his work: “Hydrodynamica” which laid the basis of the kinetic theory of gasses.
In his work on Conservation of Energy he described how a moving fluid exchanges its kinetic energy for pressure. A consequence of this law is that if the velocity increases then the pressure falls. This is exploited by the wing of an aeroplane which is designed to create an area above its surface where the air velocity increases. The pressure in this area is lower than that under the wing, so the wing is pushed upwards by the relatively higher pressure under the wing.
Kite-boarding combines wakeboarding, windsurfing, surfing, paragliding, and gymnastics into one extreme sport. A kite-boarder harnesses the power of the wind with a large controllable power kite to be propelled across the water on a board similar to a wakeboard or a small surfboard.
But how do these kites become airborne?
Partially by the principle of fluid dynamics as described by Daniel Bernulli, and partially as a parachute – and in this case, the propellant is a good stiff breeze like the tradewinds that buffet the beaches on the island of Maui almost every day.