Complex sentence: SMS "Gneisenau" was a three-masted, full-rigged sail frigate of the German Kaiserliche Marine (Imperial Navy) with an unplated iron hull and a steam engine.
Split into simpler sentences: SMS "Gneisenau" was a three-masted, fully-rigged sail ship of the German Kaiserliche Marine (Imperial Navy). It had an unplated iron hull and a steam engine.