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How to Make Propeller Blades for Windmills

Good propeller or blade design is absolutely key to building an efficient windmill. As well as being lightweight and strong you need the shape to direct the wind energy as efficiently as possible so as to generate rotary motion. Thankfully, you don't need to shape the fins yourself; it's much more efficient to cut them from something that already has a curve that lends itself to fin design. Furthermore, this approach can be used to make practically any size of fin to suit a range of different-sized projects.

Things You'll Need

PVC pipe
Marker pen
Set square
Ruler
Jigsaw
Sanding block
Coarse sandpaper

Instructions

- 1
  Choose a width of pipe appropriate to your windmill. Use pipe with a diameter of roughly 4 inches to make fins for a windmill that will stand a yard tall. Reduce this to 1 inch for a windmill that will stand only 1 foot tall. Use a length of pipe a quarter the height of the windmill.
- 2
  Cut the pipe lengthwise into four equal sections. You need to get them straight, so measure the circumference of the pipe and divide by four. Use this measurement to mark four equally spaced points around the mouth of the pipe. Press the handle of the set square against the rim of the pipe and lay the metal flat along its length.
- 3
  Draw onto the pipe using the metal edge of the set square to guide you. Use these lines to line up the ruler and continue drawing the lines from the top of the pipe to the bottom. Cut down the lines with a jigsaw.
- 4
  Lay one of the quarter pieces down on its concave side with the short edges on either side. Measure the short edges of the rectangle formed by the strip of pipe. Measure a quarter of the way up from the bottom of the left-hand edge of the rectangle and a quarter of the way down from the top of the right-hand edge. Draw a line between these points.
- 5
  Cut down this line with the jig saw. The fin will be a right-angle triangle. The long edge that forms a right angle with the short edge is the trailing edge. Sand this edge into a tapering point all the way along. Sand the other edge into a rounded curve.

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