A ZipString is an incredible device that rapidly propels, a loop of string. When the strings momentum is balanced within the forces of gravity, lift, and drag, the string actually flies. The momentum of the string is derived from its speed and its mass. Optimal strings are moving fast, and the string is made light. In a ZipString, the string is moving at about 35 miles or 65 Kilometers per hour. And the string is made from very light fibers. Another important feature is the fact that the string in the ZipString isn’t smooth. This is critical to help the string fly. When we look closely, we can see that the string has lots of small filaments that radiate outward. As these filaments move through the air, they create drag. So much so in fact, when you put your hand near the string, you can feel the air movement. Technically, the string is always under tension. Since the string is a loop, as the string is propelled out of the device, it eventually has to return. As the string begins its return, gravity pulls it downward, but because of the speed of the string, and the drag from the filaments around the string, it creates lift. This lift is mostly pronounced at the distal end, the end farthest from the device. When there’s more lift than the actual weight of the string, the string begins to fly. Another interesting observation is that because of the opposing forces of gravity and lift on the loop of string, the string always orients itself vertically. So the key to ZipString is moving a light fuzzy string through the air fast enough that it creates enough lift to overcome its weight. When that happens the string is flying. For Age 8 +
