I recently made some steel blades for my tape drive motors, that work quite well.
The base material is 1.5mm sheet galv. I cut 3 pieces 840mm (34")long, just because thats how long the piece was, 100mm wide at base and 50mm wide at tip.
At the edge which is at right angles to the base (leading edge) I measure down 20mm at tip end and 40mm at base end, scribe a line between both and bend along this line to a 25 degree angle approximatly.
I mount the broard part onto a fan hub (off a CAT)the angle of which is aroung 5 deg, but this is what I fine tune for required speed.
In my experience these motors are 25 rpm/volt, so charging my 12v system the best I have seen so far is around 8 amps. Having said that our best winds at this time of year are overnight and Allan is usually making zzzzzzz then.
A very un-high tech but works starts with a nats fart and spins up quickly, so heres the pics,


