The blades were made from sections cut from a piece of PVC gutter which had a radius of approximately 60mm. I roughly followed some of the instructions here
and ended up with a blades 58cm radius with a chord of 37mm at the tip and 72mm close to the hub. They were bolted to the hub about 10mm from the trailing edge, which sets the angle of attack of the blade.
Since constructing this first wind turbine I have added the pipe blade designer
page which will generate a plan of an optimised wind turbine blade.