The ship was designed as an improved version of existing battleships with greater displacement and a thicker armoured belt amidships.
As originally designed, Trafalgar was to have displaced 11,940 tons, and carried a secondary armament of ten guns of 5-inch (130 mm) calibre, disposed in the broadside battery.
This in turn led to the main belt being immersed to a deeper level than had been intended, with a potential decrease in defensive effect in combat.
[citation needed] As compared to HMS Sans Pareil, Trafalgar's under-water hull form was finer, with a larger rudder.
Together with the reduced freeboard as compared to earlier ships, this had a significantly adverse effect on her handling; as she spent her active service in relatively calm water in the Mediterranean, however, this defect was of minimal importance.