Complex sentence: The second torpedo struck "Blanco Encalada" between the stern and the stem, creating a hole roughly seven by 15 feet in dimension, becoming the first ironclad to be sunk with a torpedo.
Split into simpler sentences: The second torpedo struck "Blanco Encalada" between the stern and the stem, creating a hole roughly seven by 15 feet in dimension. The ironclad started to sink, becoming the first ironclad to be sunk with a torpedo.