Designing the blades
This allows you to enter the parameters described in the equations on the previous page and generate a plan of the wind turbine blades that can be cut out of PVC (or any other material) pipe.
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.
In the plan below the lines are:
- Green line - An estimate of the theoretical chord width.
- Blue line - The actual chord width.
- Red line - The arc around the exterior of the tube.
- Red dotted line - The position where the blade is perpendicular to the axis or where it would be bolted to the flat front of the hub..