Nemi Ships - Construction

Construction

Both vessels were constructed using the Vitruvian method, a shell first building technique used by the Romans.

• Step 1: construction of the profile.
• Step 2: construction of the keel and the flat bottom up to the second order of cincti, in two phases.
• Step 3: construction of the shell up to the third wale (topgallant bulwarks).
• Step 4: Insertion of the ribs, first those with trabes (crossbeam bracing) and then those without.

The hull had been sheathed in three layers of lead sheeting to protect the timbers from shipworms; as there are none in fresh water lakes, this design feature was not only useless but costly. It is evidence that the ships hulls were constructed following standardized Roman shipbuilding techniques rather than being purpose built. The topside timbers were protected by paint and tarred wool with many surfaces decorated with marble, mosaics and gilded copper roof tiles. There was a lack of coordination between the structure of the hull and that of the superstructures, which suggests that naval architects designed the hulls, while civil architects then designed the superstructure to use the space available after the hulls were completed. After their recovery, the ships hulls were found to be completely empty and unadorned.

They were steered using 11.3 meters (37 ft) long quarter oars, with the Seconda nave equipped with four, two off each quarter and two from the shoulders while the Prima Nave was equipped with two. Similar pairs of steering leeboards appear frequently in early 2nd century depictions of ships.

The Seconda nave was almost certainly powered by oars, as structural supports for the rowing positions protrude along the sides of the hull. The Prima nave had no visible means of propulsion so was likely towed to the center of the lake when in use.

A lead pipe found on one of the wrecks had Property of Gaius Caesar Augustus Germanicus stamped on it while many tiles had dates of manufacture. Together it leaves little doubt as to when the ships were built or for whom.

Seutonius describes two ships built by Caligula; "...ten banks of oars...the poops of which blazed with jewels...they were filled with ample baths, galleries, and saloons, and supplied with a great variety of vines and fruit trees." It is reasonable to speculate that the Nemi ships were equipped to a comparable standard. One year after being launched, the ships were stripped of precious objects, ballasted and then intentionally sunk following the assassination of Caligula.