Unless you want to work at tsr 8 or above things are fairly forgiving.
The golden rule is to have a tapered and sharp trailing edge. A gentle radius on the leading edge is a good idea but it will still work ok if you leave it sharp.
A flat front face is easy to make and works well. Cambered blades probably are more touchy and need to be made to higher standards. The thickest part should be about 25 to 30 % back from the leading edge.
The most important thing is for your blade to match the alternator. You can gain more from this than by any amount of fiddling about with fancy aerofoils.
The shape of the blade has a lot of influence on the matching. Using a blade with ideal twist and width at each station seems to need a lower speed alternator than a blade of fairly constant angle and width. Both will work perfectly well if you can match the load.
The old Lucas Freelite blade was constant pitch, only slightly tapered and the back surface was part of a circle, no doubt cut on a spindle moulder for simplicity.
I have tried one on a modern alternator and it works very well over the range tsr6 to tsr9.
For a commercial manufacturer making many blades for a known load condition there is no doubt a bit to be gained by carefully selecting aerofoils but for home use the simple designs are likely to be as good as any.
Flux
