Comparison of Savonius variations

Having built models of the designs i wanted to test,I then monitored their performance over  a few hours.

Base for the comparison was a cup-type anemometer

the first model was a std Savonius design









next came a split 4-bladed version

lastly a revised version of the last design, only with zero overlap
(as suggested in my previosu postings, I was curious about whether any more lift effect might be gained)

 Here are the results

 

Summary / interpretation of results

Well it seems my alternative designs  werent a radical improvement on the original!

I'm a bit mystified by the ripple in all plots around the 17rpm (of the base anemometer, which I must get around to calibrating in mph!) mark;