Four-decker (sailing ship)
A four-decker is a sailing ship with four battery decks .
Representatives of this type of ship were the Santissima Trinidad (launched in Havana in 1769, Battle of Trafalgar until 1805 ), which was converted from a three-decker, and the American USS Pennsylvania (1837 to 1860). According to the English classification, these ships were ships of the line of the 1st rank.
In fact, these ships were not "real" four-deckers in the sense that a two- decker was a two- decker . In the case of two-deckers and three- deckers, the aft deck (with the hut deck attached) and the forecastle deck followed above the top battery deck. In the case of "four-deckers", however, the uppermost battery deck was completely open (as in the case of the Pennsylvania ) or only covered aft by the original hut (in the case of the Santissima Trinidad ). Aft deck and forecastle superstructures were therefore missing. The fourth battery deck was created by joining the bulwarks of the aft deck and the forward superstructure (forecastle deck). This also made it possible to use the previously unused middle area of the top deck (the "Kuhl ”) set up cannons. Nevertheless, the term four-decker is correct after the number of continuous battery decks, even if there are no differences to the three-decker from the actual deck layout.
The combat value increase of such a ship was negligible compared to a three-decker. On the one hand, because of the weight, only light cannons (8 pounders in the Santissima Trinidad ) or carronades (in the Pennsylvania ) could be set up there, and on the other hand the cannons prevented the crew from operating the sails. The raised bulwarks also offered the wind more surface to attack and increased the drift to leeward .