HMS Calcutta became a 56-gun fourth rate after serving as an East Indiaman. She measured about 48 metres overall, with a keel just under 40 metres, a beam of 12.6 metres, and a draft slightly over five metres. Her merchant complement of 125 rose to 324 in Royal Navy service. The merchant battery consisted of twenty-six 9-pounder guns on the upper deck. After conversion, the lower deck carried twenty-eight 18-pounders, while the upper deck carried twenty-six 32-pounder carronades and two 9-pounder guns. The carronades offered powerful short-range fire, and the lighter long guns suited the upper deck's weight limits. The new lower battery alone delivered more than twice the original merchant broadside weight. The hull's size and strength made conversion possible, while the extra men and weapons supplied the fighting power.
Notable Point · 1:07:10-1:10:47
HMS Calcutta shows the merchantman-warship gap
A converted East Indiaman shows why these ships could resemble fourth rates while still falling far short of a purpose-built ship of the line.