This is a very speculative attempt to model a double-hulled ship carrying a siege tower in 1/1200 scale. Demetrius I Poliorcetes or Lysimachus may have used something like this for siege operations against cities in the early 3rd Century BCE. See Chapter 6 of “The Age of Titans” by Murray.
The model uses the hulls of two 1/900 scale Ramming Speed ships by Valiant Enterprises. The tower is 30 meters tall in 1/1200 scale, or about 3/4 of the estimated height of Helepolis.
ncc1717.com 