Complex sentence: The "Ajax" class copied "Inflexible" s armour scheme of a heavily armoured citadel with unamoured ends and sides, but unlike their predecessor, they lacked enough buoyancy to remain afloat if their ends were flooded.
Split into simpler sentences: The "Ajax" class copied "Inflexible" s armour scheme of a heavily armoured citadel with unamoured ends and sides. But unlike their predecessor, they lacked enough buoyancy to remain afloat if their ends were flooded.