The wind is coming over the hill towards us/the camera. Two sails are shown. The left one is coming towards us, and the right one is going away. The left adding to rotation, the right momentarily resisting it.
The sails shown in this design are solid. If they were cloth and between two bars, then the sails could adopt a modest aerofoil shape and add to rotational force in multiple positions. Most notably, positions 4 & 6 in the previous blog entry. As is with this solid sail design, positions 4, 5, and 6 are effectively drag.
Also, the gearing is shown as a chain and cogs here. That would be impractical due to chain sag. The real one that I built was used bevel gears that are also inefficient.
This illustration shows something that is a couple of hundred yards tall. It will keep going in low wind conditions and still perform in higher winds.
Next up, horizontal vs vertical axis wind turbines.