Regarding the two towers : if you look at the E-ship 1 [0] you'll see 4 towers - 2 in the front, 2 in the rear. There are no towers in the middle, probably beca

Regarding the two towers : if you look at the E-ship 1 [0] you'll see 4 towers - 2 in the front, 2 in the rear. There are no towers in the middle, probably because that area is intended for cargo. I presume there is also a minimum distance they need to be separated - if you look at some of the illustrations of the Magnus effect [1], you'll see a turbulent region downwind of the tower. Another tower in this turbulent region won't work as intended. This is pure speculation on my part, but perhaps most ships simply aren't wide enough to have two towers side by side (the E-ship 1 being an exception). That, and wanting to use most of the ship for cargo, explains why most ships only have 2 towers. [0] https://en.wikipedia.org/wiki/E-Ship_1#/media/File:Bateau_enercon_P9240983_part.jpg https://en.wikipedia.org/wiki/E-Ship_1#/media/File:Bateau_en... [1] https://en.wikipedia.org/wiki/Magnus_effect https://en.wikipedia.org/wiki/Magnus_effect