2. Liberty ships were built by assembling prefabricated sections
Liberty ships were among the earliest classes of ships built by assembling sections prefabricated elsewhere. The sections were assembled on the slipway or construction basin, where they were welded together. The use of welding rather than riveting reduced the number of workmen needed to assemble the sections. Riveting required a team of workers, one to heat the rivets, one to toss them to the riveters, one to hold the rivets in place as the riveter pounded them into the shape required to pin the sections. Each seam required multiple rivets to complete the joint. A welded seam required just one or two welders. Thus, multiple men found themselves free for other duties, a boon considering so many joined the surge to enter the armed forces in the weeks following the attack on Pearl Harbor.
Another factor altered the manpower required to build the Liberty ships. As Liberty ship production expanded in 1942 (eventually 18 American shipyards were building the ships), acute labor shortages led to the recruitment of women at all of them. Women received rudimentary training in the skills required for their jobs before assignment to work on the ships. When it came to the Liberty ships, Wanda the Welder replaced Rosie the Riveter. The women became so adept at their jobs that the time required for the completion of one Liberty ship contracted from just under nine months to an average of 42 days. By mid-1943 the United States completed 3 Liberty ships every day of the year. At most shipyards, launchings were attended by women workers, dressed in their work clothes, in tribute to their counterparts across the United States.