This week, we’ve arrived at something that everyone will be able to recognize right away: Titanic’s steel hull. The construction of her hull is quite intricate, which becomes evident when one closely analyzes photographs of it. From the thousands of rivet heads to the rows of plating defined by their slight overlap, the hull is a study in the shipbuilding techniques of the early 1900s.

Let’s start with the basic materials that made up the hull.

Titanic’s hull was made up of individual plates, each of them averaging 30 feet in length and six feet in width, with a thickness averaging one inch, but thinning toward the bow and stern ends. The largest plates were 36 feet in length. Each plate weighed in around four tons. The plates were of mild steel, rolled in a low-speed mill, and were of extremely high quality for the time. 

The plates were held together by rivets, about three million of which were used in her overall construction. Shipbuilder magazine’s special number on Olympic and Titanic notes that over 500,000 of these rivets were located in the double bottom we discussed last week. The rivets were of wrought iron and of various sizes up to one and a quarter inches in diameter. The rivets along the sides of the hull, where the plates were relatively flat and the holes easy to access, were driven hydraulically. The ones at the ends and at the turns in the hull where hydraulic riveting wasn’t possible were driven by hand-hammering. The rivets were placed while still white hot, allowing them to expand into the hole as they cooled.

Other parts of the hull, such as the propeller shafts and rudder post, were made by the process of forging, or hammering or pressing a heated steel into a required form. Likewise, the ship’s rudder, stem, and stern frame, among other components, were made by casting, where molten steel was poured into a cast, or pattern. Both casting and forging were used for special shapes that couldn’t be rolled in a mill as the plates were, and also to create parts that were required to be particularly strong and stand up to stress.  

Two methods were used to assemble the hull, giving its distinct pattern. The lower part of the hull was built with the “clinker” method, where each row, or strake, was placed outboard and overlapping with the previous and lower one. Once the turn of the ship’s bilge was passed and the hull proceeded upward to form the sides of the ship, the method switched to an “in-and-out” one, where an inner strake was positioned against the individual frames and alternated with an outer strake that overlapped the adjacent inner strakes. 

While much has been made of the strength (or lack thereof) of Titanic’s hull and rivets, it’s important to note that Titanic’s construction used the best methods and materials available at the time. As Harland and Wolff built ships for White Star on a cost-plus basis, there was also no incentive or need to cut corners to meet a budget. Finally, as Titanic sank, her hull was subjected to extraordinary stresses and not only stood up beyond her design specifications and the expectations of her builders, many of her rivets and hull plates remain fully in place today on the ocean floor. 

The hull was formed around a series of frames. Next week, we’ll take a look at how the framing was completed. 

Next Week: Titanic’s Frames

Written By: Nick DeWitt