Liberty Ships - Design Flaws

In Book 1, The Hesperus Prophecy, the Clypeate travels to Antarctica aboard the SS Valencia, a prototype of the Liberty ship class of cargo ships.

In Book 2, Girl in the Glass, we learn more about Liberty ships, including their flaws. After liftoff, Captain Noonan tells his senior officers:

“Her hull suffered damage during lift off, minor stress fractures created when the ship pitched and yawed during liftoff. Normally this wouldn’t be an issue, except there’s a recently discovered design flaw in Liberty vessels like the Valencia, one we didn’t anticipate. With low temperatures the steel becomes brittle, rigid, and cracks easily.”

Despite their crucial role in World War II, Liberty ships had several design flaws, stemming primarily from their rapid wartime production and the use of welding instead of riveting.

First, the metal used to build the hull was problematic. As mentioned in the novel, the steel used in early Liberty ships became susceptible to brittle fracture at low temperatures, such as those encountered in the North Atlantic.

Second, the welded hulls allowed cracks to propagate unimpeded. On riveted ships, the rivets can stop cracks, but the welding on Liberty ships could cause the hull to break in half without warning.

Further adding to the issues, welding as a primary shipbuilding technique was new. Many new, less experienced welders were hired, leading to weld defects that acted as points of stress concentration, causing and propagating cracks.

While these problems led to some catastrophic failures and significant losses, the valuable lessons learned greatly advanced the study of fracture mechanics and metallurgy used in later ships.