A propeller is a very complex airfoil, and its pitch (the "slant" of the blade) is not the same throughout its length. Think about it. The tips are moving very fast (many feet per minute) through the air compared to the parts of the blade near the center or hub. We want to force developed by the blade to be "somewhat the same" along its length, with a bit more near the hub where it's stronger. Use the link below to see how a three-bladed, variable pitch design is manufactured. Be sure to let the first few seconds of "other stuff" go by before the start of the segment on the manufacture of the propeller, okay? And while you're at that site, look at the other related video clips listed on the right. It's really interesting stuff!