Why do modern aeroplane wings have a vertical tip?
The concept of using winglets has been studied since the 1800’s and a patent was even filed in 1897 by Frederick Lanchester for what was then called the endplate concept. The drag penalty was found to be too high in cruise to be of any benefit at the time. In conventional wing design, the cambered upper surface of the wing creates a low pressure or suction effect, while the more flat lower surface creates a higher pressure than the upper surface. The air flowing around these two surfaces remains divided until the wing tip where the airflow from the lower surface gets sucked up and rearward by the low pressure created on the upper surface. It begins to swirl and creates a lot of drag. It’s called wingtip vortices, much like a mini-tornado. This effect creates a wake consisting of two counter-rotating cylindrical vortices, called wake turbulence. Flight tests have shown that the vortices from larger aircraft sink at a rate of several hundred feet per minute in calm air about 1000 feet lo
