As for use of steel plates - the manufacture of steel plates didn't begin until about fifty years later. Little coal was available, little iron ore. I tried hard to find dates, had no luck.

Not true, Bill. Boilers were being manufactured as early as 1780. To do that they had to manufacture iron or steel plates. They knew how to do it. They had the technology. They chose not to use it. Or they lacked the imagination to.

- Pfranz