Roman Shipbuilding & Navigation

Unlike today, where shipbuilding is based on science and where ships are built using computers and sophisticated tools, shipbuilding in ancient Rome was more of an art relying on rules of thumb, inherited techniques and personal experience rather than an engineering science. The Romans were not traditionally sailors but mostly land-based people who learned to build ships from the people that they conquered, namely the Carthaginians (and their Phoenician predecessors), the Greeks and the Egyptians.


Warships were built to be lightweight, fast and very manoeuvrable. They would not sink when damaged and often would lay crippled on the surface after a naval battle. They had to be able to sail near the coast, which is why they had no ballast and were built with a length to breadth ratio of the underwater hull of about 6:1 or 7:1. They had a ram often made of bronze which was used to pierce the hulls or break the oars of enemy ships. Warships used both wind and human power (oarsmen) and were therefore very fast.

There were many kinds of warships. The trireme (derived from Latin “triremis” meaning “with three banks of oars”) was the dominant warship from the 7th to 4th century BCE. It had three rows with rowers in the top, middle and lower rows, and approximately 50 rowers in each row. The rowers in the lower row had the most uncomfortable position as they were under the other rowers and were exposed to the water entering through the oar-holes. It is worth noting that contrary to popular perception, rowers were not slaves but mostly Roman citizens enrolled in the military.

The trireme was superseded by the larger quadriremes and quinqueremes. The quadrireme had four rows of oarsmen while the quinquereme had five. According to Polybius, the Roman quinquereme had a total of 300 rowers with 90 oars on each side. It was about 45 m long and 5 m wide and would displace around 100 tons. It was superior to the trireme, being faster and performing better in bad weather.

Merchant ships were built to transport lots of cargo over long distances and at a reasonable cost, therefore speed and manoeuvrability were not a priority. They had a length to breadth ratio of the underwater hull of about 3:1, double planking and a ballast for added stability. Unlike warships, their V-shaped hull was deep underwater meaning that they could not sail too close to the coast. They usually had two huge side rudders (or steering oars) located off the stern and controlled by a small tiller bar connected to a system of cables. They had from one to three masts with large square sails and a small triangular sail called the supparum at the bow.

The Roman merchant ship’s cargo capacity usually was between 100 to 150 tons (150 tons being the capacity of a ship carrying 3,000 amphorae). The smallest ships had a capacity of 70 tons while the largest could have a capacity of 600 tons for a length of 150 feet (c. 46 m). Cargo included agricultural goods (e.g. grain from Egypt’s Nile valley, wine, oil, etc.), raw materials (iron bars, copper, lead ingots, marble, and granite) and other goods. Just like warships, merchant ships also used oarsmen. Following the collapse of the Roman Empire, no ships of the cargo-carrying capacity of Roman ships were built until the 16th century CE.

Just like with shipbuilding, navigation in ancient Rome did not rely on sophisticated instruments such as compasses or GPS but on handed-on experience, local knowledge and observation of natural phenomena. In conditions of good visibility, seamen in the Mediterranean often had the mainland or islands in sight which greatly facilitated navigation. They sailed by noting their position relative to a succession of recognizable landmarks and used sailing directions. Written sailing directions (periploi in Greek) for coastal voyages were actually introduced in the 4th century BCE. They were initially written in Greek and they existed for trips in the Mediterranean. By 50 CE, there were written directions not only for the Mediterranean but also for routes from Atlantic Europe to the city of Massilia and for routes along the coast of north-west Africa, around the horn of Africa or past the Persian Gulf to India and beyond.

When weather conditions were not good or where land was no longer visible, Roman mariners estimated directions from the pole star or, with less accuracy, from the sun at noon. They also estimated directions relative to the wind and swell. A lot of the Romans’ navigational skills were inherited from the Phoenicians. Pliny claimed that the Phoenicians were the first to apply astronomical learning gained from the Chaldeans to navigation at sea.

Both merchant ships and warships used wind (sails) and human power (rowers). Coordinating the hundreds of rowers was not an easy task and in order to solve this problem of rowers’ coordination, a musical instrument, usually a wind instrument, would be played. Roman seamen also had to have a good understanding of natural phenomena, wind direction relative to the sail, and they had to know how to operate the sails in various weather conditions.

Presented by Romano Pisciotti

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