The internal bulge placed a protective bulkhead twelve feet inboard behind an outer airspace and a buoyancy space. Flooding the system required about 2,870 tons of water, increased draft, and reduced speed, so the buoyancy spaces normally remained dry in peacetime. Model trials at Chatham led to a full-scale test in which a thousand-pound charge tore a large opening in the outer plating but produced negligible leakage into the hull proper. The result supported the conclusion that a protected ship could continue in action at reasonable speed after such a hit. Later evidence also led designers to seal venting plates that did not relieve pressure at the decisive moment, showing how the scheme continued to evolve through destructive testing.
Chapter · 1:54:50-1:57:18
Nelson's water-filled protection and full-scale torpedo test
Nelson and Rodney used layered air and buoyancy spaces that could be flooded in wartime, with a full-scale trial indicating protection against a thousand-pound underwater charge.