Small Wind Turbine Blade (6 Foot Dia.): This Instructable will give you a step by step process on how to carve a real wind turbine blade out of wood (not those fake ones from a 4' PVC pipe, but they are cool too.). This was designed by me, a real Aerospace Engineer, using real airfoils.
It is possible to produce some impractical shapes so. Use the external radius of the pipe for the calculation. The plan can then be wrapped around the pipe to generate the shape of the blade. If the pipe radius is too small and the offset is large to compensate you will end up with a near semi-circular blade section at the blade tip. If a high tip speed ratio is used and a high angle of attack, the tips of the blades will be at a negative angle. I choose a value of Cl=0.85 at 4 degrees angle of attack but this was an estimate. The lift and drag coefficients will depend on the thickness of the section which varies along the blade length.
This project shows us how you can build a small DIY Vertical Axis Wind Turbine, We are not expecting to get much over 50 watts of production, though it would be fairly simple to double the size of the blade area to increase power. This DIY Vertical Axis Wind Turbine is based on the use of 4 inch PVC pipes, cut in half, for the blades.
The blades are mounted on bicycle rims. This structure is then mounted using 2×4’s and a DC treadmill motor is connected at the bottom, via a belt. The belt connection allows for an increase in RPMs to the treadmill motor. Check out this article from greenterrafirma.com below to see just how they made a pvc verticles axis wind turbine.