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I have long been interested in bulding a homemade wind turbine for generating electrical power, especially if if means lowering my electric bill.

Lately, I have been finding some info on the web that moves this closer to being a doable project for the home tinkerer. I am sure the most efficient wind turbine blades are those with a carefully shaped airfoil. But that means carving or machining 3-dimensional blades to fairly tight tolerances. I am sure that is possible for some folks in their home workshop but I am sensing there are ways to make blades without all that trouble, although these other ways would undoubtedly result in somewhat less efficient airfoil shapes.

I live in an area that is quite flat for miles around and surrounded by large open fields, it is very often quite windy, even down close to the ground. So I expect that a wind turbine would not have to be up too high to work pretty well at my place.

In fact, one issue that must be considered is what to do when the wind is so strong that it might threaten the structural integrity of the turbine itself. In recent years, we have had a number of occasions when the wind was in excess of 40 mph and has reached 75 mph at least one time.

On the subject of fabricating homemade blades, I have found that others have made blades by the careful cutting of a length of large diameter plastic pipe. While most turbines run with 3 blades, I think I can make a good case for using 4 blades because it results in a stronger structure. It might also increase output power somewhat but that is not the big reason.

A two bladed wind turbine is definitely out due to stress and vibration issues, especially when the direction of the wind changes. If the structure of the hub and blades has a lot of mass along one axis but little mass along an axis perpendicular to the first axis, the vibration problem is at its worst. That is why you do not see wind turbines with a simple two-bladed prop design. Adding the third blade causes the mass to be distributed evenly all around the plane in which the blades spin so the vibration problem goes away. However, using a three-bladed design means that there would be a hub with three separate blade pieces bolted to it. Those attachment points (the bolts) experience some very high forces when the turbine is under load. Sometimes, the blades break right where they are attached to the hub because of that.

Therefore, I am considering a four-bladed design. That way a single long piece of plastic pipe serves to become two blades that point in opposite directions. A second identical piece of pipe forms the two blades that point at right angles to the first piece. There is no requirement that one pair of blades rotates in exactly the same plane as the first so one piece of plastic pipe can simply pass right behind the other. This should also simplify balancing each pair of blades because each piece of pipe can be statically balanced before being mounted to the hub of the turbine.

If you have thoughts on this, please contact me. (More later.)