The parent model is a galley model made by Captain_Ahab_62 on Thingiverse. I've amended the model here to make a cataphract version, and additional versions with towers.
The original model can be found here: https://www.thingiverse.com/thing:3057533
I've also used the basic model to make a small set of Renaissance galleys. I'll be aiming to print off a test set tomorrow.