HMS Rochester was a 50-gun fourth rate ship of the line

Ship of the line

A ship of the line was a type of naval warship constructed from the 17th through the mid-19th century to take part in the naval tactic known as the line of battle, in which two columns of opposing warships would manoeuvre to bring the greatest weight of broadside guns to bear...

 of the Royal Navy

Royal Navy

The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...

, built at Deptford Dockyard and launched on 3 August 1749.

In contrast to standard practise at the time, Rochester was not built to the Establishment of dimensions in effect at the time (in this case, the 1741 proposals of the 1719 Establishment

1719 Establishment

The 1719 Establishment was the first formal 'Establishment' laid down to govern the construction of all ships built or rebuilt down to those of 20 carriage guns, whether in the Royal Dockyards or by commercial contractors...

). Rochester and her sister-ship, , were 6 ft (1.8 m) longer than the Establishment specified, and were ordered as an experiment in building larger ships in response to the widening gulf between the sizes of British ships and their continental counterparts.

Rochester was eventually sold out of the navy in 1770.