from Athens was a capital offense. This cable would act as a stretched tendon straight down the middle of the hull, and would have prevented hogging. Additionally, hull plank butts would remain in compression in all but the most severe sea conditions, reducing working of joints and consequent leakage. The hypozomata would also have significantly braced the structure of the trireme against the stresses of ramming, giving it an important advantage in combat. According to material scientist J.E. Gordon: "The hupozoma was therefore an essential part of the hulls of these ships; they were unable to fight, or even to go to sea at all, without it. Just as it used to be the practice to disarm modern warships by removing the breech-blocks from the guns, so, in classical times, disarmament commissioners used to disarm triremes by removing the hupozomata." Dimensions Excavations of the ship sheds (neōsoikoi, νεώσοικοι) at the harbour of Zea in Piraeus, which was the main war harbour of ancient Athens, were first carried out by Dragatsis and Wilhelm Dörpfeld in the 1880s. These have provided us with a general outline of the Athenian trireme. The sheds were ca. 40 m long and just 6 m wide. These dimensions are corroborated by the evidence of Vitruvius, whereby the individual space allotted to each rower was 2 cubits. With the Doric cubit of 0.49 m, this results in an overall ship length of just under 37 m. The height of the sheds' interior was established as 4.026 metres, leading to estimates that the height of the hull above the water surface was ca. 2.15 metres. Its draught was relatively shallow, about 1 metre, which, in addition to the relatively flat keel and low weight, allowed it to be beached easily. Construction Construction of the trireme differed from modern practice. The construction of a trireme was expensive and required around 6,000 man-days of labour to complete. The ancient Mediterranean practice was to build the outer hull first, and the ribs afterwards. To secure and add strength to the hull, cables (hypozōmata) were employed, fitted in the keel and stretched by means of windlasses. Hence the triremes were often called "girded" when in commission. The materials from which the trireme was constructed were an important aspect of its design. The three principal timbers included fir, pine, and cedar. Primarily the choice in timber depended on where the construction took place.