In the British
Royal Navy, a
third rate was a
ship of the line which from the 1720s mounted between 64 and 80 guns, typically built with two
gun decks (thus the related term
two-decker). Years of experience proved that the third rate ships embodied the best compromise between sailing ability (speed, handling), firepower, and cost. So, while
first rates and
second rates were both larger and more powerful, the third-rate ships were in a real sense the optimal configuration.