Step 6: Add the Other Two Blades
Add the other 2 blades below, at 90 degrees to the first two. This gives a much smoother running, and a better chance of the blades facing the wind at startup.
Remember to cut 50mm holes in the top of each bucket half so they fit onto the center shaft.
You can drill small holes where the top 2 blades meet the bottom two, and tie the blade sets together with wire or cable ties. This really stiffens the whole strucure up nicely.