|Single hull, Double bottom, and Double hull ship cross sections. Green lines are watertight; black structure is not watertight|
Thursday, 31 March 2016
Waratah was built with the much-acclaimed double hull, which together with watertight compartments was supposed to make her unsinkable. The depth of hull (outer) was quoted as being about 38.5 ft. and depth in hold from tonnage deck to ceiling midships, about 35 ft. which implies that the space between the two hulls was 3.5 ft. (minus hull plate thicknesses). This space no doubt contributed significantly to additional buoyancy. It was referred to as a cellular double bottom, due to the incorporation of 9 ballast tanks + 2 peak tanks. It immediately becomes apparent that if these ballast and peak tanks were full, Waratah would lose much needed additional buoyancy. The inner hull would be protected in low-energy collisions but not in high-energy collisions such as striking a rock; sand bar or wreckage at 13.5 knots. The Waratah was making 13.5 knots astern of the Harlow when the lights went out....