From Erich Plaut
In Julian Smith’s fascinating “Ted’s excellent adventure” (31 January, p 36), the diagram of Ted Ciamillo’s submarine shows the rear fin as rigidly attached to its propulsion rods. This can’t be how it works. Instead of constantly thrusting the water to the rear, half the time the attachment would propel the water forward, causing the submarine to remain stationary.
Surely there must be some kind of hinge linking the fin to the rods, so that it moves in a similar way to a dolphin’s tail or a human diver’s swim fins.
Pompton Plains, New Jersey, US
