Liberty Ship Production Data

Quote of the Day

Logistics is the ball and chain of armored warfare.

- Heinz Guderian

Introduction

Figure 1: Photograph of the USS John W. Brown, one of two Liberty Ships serving as museums (Source).

One WW2 battle that we hear little about was fought by logisticians. Their battle was between what could be produced versus what could be delivered in time to matter.  This point was driven home to me when I heard a WW2 historian say that the US had the manufacturing capacity to produce 150K tanks, but that level of tank production would consume all the US steel and leave nothing to build the ships needed to carry the tanks to the fight.

Background

Figure 2: Cross-Section of a Liberty Cargo Ship  (Source).

WW2 logisticians needed to balance performance and quality with time to build and deliver. The Liberty Ship was a prime example of this balancing act. It was a key contributor to the timely delivery of war materials to all fronts during WW2. Figure 2 shows the basic layout of a Liberty Ship configured for carrying cargo, which was its most common configuration. These ships could carry just over 10,000 tonnes of cargo. This meant that a Liberty Ship could carry 2,840 jeeps, 440 light tanks or 260 medium tanks, or 230 million rounds of rifle ammunition (Source).

The design of the Liberty Ship was very simple, which allowed it to be built by many shipyards. Its simple design also made it easily configurable for other applications. There were three basic types: Cargo, Tanker, and Collier. However, some of these ended up configured as hospital ships, floating maintenance platforms, boxed aircraft transports (i.e., carried aircraft that were in boxes), and troopships.

Analysis

Process

I found all the data that I needed in the tables within this pdf document. I extracted the tables using the free tool called tabula. I then used the regular expression processing ability of Notepad++ to tidy up the data for processing. The actual analysis was performed using Excel, Power Query, and pivot tables. My workbook and the associated text files are in this zip files.

Summary Statistics

Table 1 shows the number of Liberty Ships built per year. As you can see, production peaked in 1943. This makes sense when you see that the US was preparing to supply its big push during 1944. Table 2 shows the number of Liberty Ships built per shipyard. There were 16 shipyards that laid keels for 2711 Liberty Ship – one ship, Louis C. Tiffany, was destroyed by fire before it was completed. Table 3 shows how the median number of days to produce a Liberty Ship varied by year. The median number of days required to product a Liberty Ship reached its minimum during the year when production peaked.

Conclusion

There was nothing pretty about a Liberty Ship – FDR called it "a dreadful-looking object." It provided sealift when needed to support the major campaigns of 1944 and 1945. It certainly had issues. It was vulnerable to U-boat attack because it was underpowered and slow. Also, a major problem was discovered after three ships split in two while operating in cold water (Figure 3). 30% of the Liberty Ship fleet eventually experienced the cracking problem (Source). A pioneering female metallurgist, Constance Tipper, discovered that the steel used in the Liberty Ships became brittle below a critical temperature. A series of remedies were provided the resolved the issue for later production runs. One contributing factor to the cracking problem was the extensive use of welding in the fabrication of the Liberty Ships. ww2 shipyards had relatively little experience with welding because previous ship designs had been built using rivets – a form of fastening that is much less susceptible to cracking issues, but not applicable to modern mass-production methods. Welding and design practices were eventually developed that made welding a mainstay of the shipbuilding industry.

Figure 3: Picture of the SS Schenectady after a cracking failure (Source).

Because the Liberty Ship's slow speed made it vulnerable to U-boats, the US developed the Victory Ship class that had more powerful engines and higher speed. This made it usable in high-speed convoys, which the lower speed U-boats had more difficulty engaging.

Figure 4 shows my summary of Victory Ship production during WW2. Here is my Victory Ship workbook for those who are interested. There were five wartime Victory Ship variants:

• VC2-S-AP2: 6,000 SHP steam turbine engine
• VC2-S-AP3: 8,500 SHP steam turbine engine
• VC2-M-AP4: single ship, MS Emory Victory, 5,850 SHP diesel engine
• VC2-S-AP5: Haskell-class attack transport
• VC2-S-A2: single ship, SS Sea Marlin, built to US Army requirements

This data ignores three Victory Ships made post-war by Alcoa in 1947.

Figure 4: Summary of Victory Ship Data.