The Aerodynamics of Power Kites

(Not the project, just the page... :) )

This was the title of my project for my MEng. Although the engineering course at Cambridge is general for the first two years, specialisation occurs over the next two. I chose to specialise in fluids. In the fourth year, 8 papers are studied. These run concurrently with the project, and 50% of the marks is awarded for each. This project was run for the first time in 2000-2001, and I took part in it along with Tom Street and Ari Liddell. The research was sponsored by Flexifoil International, one of the leading kite manufacturers. I'm not going to attempt to describe all of our findings, as that took three reports of 30+ pages! This is just a bit of an insight into what we did, and a chance to show some of the pictures.

What is a power kite?
This is normally one of the first questions we get asked! The easiest answer is to show people, but most of the time this isn't possible. The picture to the right is of a Flexifoil Blade 2.6, flying on Heacham beach in Norfolk. It looks quite small in the picture, and this is the smallest kite in the Blade series, but it is still 2.6 square metres. Believe me, it doesn't look so small when you unroll it indoors! These kites fly very steadily (unlike stunt kites), and provide a lot of power - the kite in the picture can lift me off the ground on moderately windy days! These kites are fun to fly and jump with, or can be used to tow buggies at up to 60mph, and they are used in the increasingly popular sport of kite surfing.

Do they have any aerodynamics?
This was a question we had to field from our head of department! We felt it was a little... umm... rude, but I guess it's valid. The ram-air kites (like the Blade) do look rather like ripstop sacks on the ground. They are called ram-air because they look rather like paragliders, with a vent at the front to allow the air in which then inflates the kite, causing it to take on a more aerodynamic profile.