By 1978 the initial excavation work had uncovered a complete and coherent site with an intact ship structure and the orientation of the hull had been positively identified as being on an almost straight northerly heading with a 60-degree heel to starboard and a slight downward tilt towards the bow. As no records of English shipbuilding techniques used in vessels like the "Mary Rose" survive, excavation of the ship would allow for a detailed survey of her design and shed new light on the construction of ships of the era. A full excavation also meant removing the protective layers of silt that prevented the remaining ship structure from being destroyed through biological decay and the scouring of the currents; the operation had to be completed within a predetermined timespan of a few years or it risked irreversible damage. It was also considered desirable to recover and preserve the remains of the hull if possible. For the first time, the project was faced with the practical difficulties of actually raising, conserving and preparing the hull for public display.