Ahh nice one!
Perhaps the photo is deceiving me, but it looks like you have set the airfoil at the same angle along the whole length of the blade? It should be twisted ... look at the oncoming wind and the speed of each point, radially, on the blade as vectors and the angle between those vectors plus the angle of attack is the angle you set each cross section at. I also offsetted the leading edge to obtain a taper, so the chord at the end of the blade is centered about the root. This was my first attempt before I made the CNC router, so done on the mill in 4 operations, plywood:

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Then I did an MDF mould about the same length as yours and made them with fiberglass...which you've already seen. It's so much better, try it!

http://www.mycncuk.com/forums/showth...turbine-blades

1.5m blades coming soon...

4 axis would make it faster as you could use the side or, with 5 axis, the end of an endmill for the finishing pass. But I'm not sure it's really worth it? Would look good though!
Since I'm going to make moulds for the blades, not the actual blade, the surface is concave so I would still have to use a ball-nose cutter. 4/5 axis allows the cutter to be kept at a constant angle to the surface, which should allow it to cut faster as it avoids using the centre of the ball nose cutter.