Construction: Steel hull and decks

Steel hull and decks

The steel hull of the ROTTERDAM, built in 789 sections, was primarily of welded construction. Some sections were, however, joined with the traditional rivets both to act as ripstops and to facilitate the erection of the ship in her building berth. Riveting was also used in certain frame-to-skin connections forward and aft for esthetic reasons. Similar connections made by welding always show an indentation or dimpling which would be especially noticeable and disturbing on otherwise long, smooth sections of the ship’s skin.

The keel was laid on December 14 1956 picture RDM

The decks of the Promenade and Lower Promenade Decks were of thicker construction than that of the other decks. Together with the ship’s double bottom, these formed a box which acted as the ship’s strength hull in order to withstand the lengthwise bending stresses to which she would be subjected in service.

It would have been possible to include the walls of the Promenade and Upper Promenade Decks in the strength hull of the ship, but that would have made it impossible to include the large windows which were desired without considerable extra strengthening which would in turn have added considerable weight to the ship topsides. Since it was now possible to construct the superstructure of relatively light materials, it became necessary to divide its construction into five independent sections. Movement between sections would be handled by expansion joints. This principle had been used previously. What was unusual was that in the ROTTERDAM the joints were left exposed. Watertightness and limitation of movement of the joints required careful finishing. And naturally a sufficient number of partitions had to be provided in each section to resist thwartship bending forces.

The situation on June 27 1957 picture RDM

The situation on March 15 1958 picture RDM

An internal truss on the Boat Deck made it possible to span the length of the auditorium below. In this way, the space could be kept free of columns. Its construction consisted of steel walls with a minimum number of small, specially strengthened door openings. The width of the Ritz Carlton Lounge was bridged in a similar fashion.

Aluminum deckhouses

All deckhouses above the Sun Deck were constructed of aluminum. The reason for this was not only to save weight, but also to lower the ship’s center of gravity with a consequent increase in stability. The use of aluminum below the Sun Deck would have made little sense mostly because of the extra fire precautions required. The aluminum deckhouses contained the navigating bridge forward, the Sky Room midships with observation decks above, and the top deck with its two slim smokestacks. The smokestacks themselves were of steel construction, clad in an aluminum outer skin. In order to provide a smooth outer surface the cladding of the smokestacks, the walls of the deckhouses, and the radar mast were riveted; the remainder of the aluminum used in the construction of the ship was welded.


Aluminium superstructure and lifeboats  picture Klaas Krijnen

The use of aluminum was an expensive business. It would have been cheaper to ensure the stability of the ship by using permanent ballast in the ship’s bottom. It was determined, however, that the higher initial cost would be offset by fuel savings which would pay back the added expense after only ten years.