Decks, hatches, and superstructures

This chapter focuses on the decks, hatches, and superstructures of the ships. Decks at different levels in a ship serve various functions; they may be watertight decks, strength decks, or simply cargo and passenger accommodation decks. Watertight decks are fitted to maintain the integrity of the main watertight hull, and the freeboard deck, which is the uppermost deck having permanent means of closing all openings in the exposed portions of that deck, is the most important. Although all decks contribute to some extent to the strength of the ship, the most important is that which forms the upper flange of the main hull girder, called the “strength deck”. Superstructures might be defined as those erections above the freeboard deck which extend to the ship's side or almost to the side. Deckhouses are those erections on deck which are well within the line of the ship's side. Both structures are of importance in the assignment of the load line as they provide protection for the openings through the freeboard deck. Of particular importance in this respect are the end bulkheads of the superstructures, particularly the bridge front which is to withstand the force of any seas shipped.