Historically the middle decades of the nineteenth century were a period of flux in naval tactics, as the advent of gun-proof ironclads led naval commanders to search for some new method of defeating enemy ships. In the end this situation was resolved by the invention of the armour-piercing shell and of the torpedo, which meant that vessels were once again able to destroy each other at a distance. Say, though, that these inventions were butterflied away, or at least delayed by a few decades relative to their discovery IOTL. How would naval tactics have developed in their absence? A lot of people at the time expected the ram to become the dominant weapon, although most modern historians seem sceptical as to their efficiency. Maybe boarding enemy vessels would become the main tactic?