U.S. ships in World War II had 'phantom decks'

While the U.S. was lucky to fight World War II away from its shores, that meant it had to move massive amounts of supplies across the ocean.

With German submarines sinking American vessels and shipyards busy rebuilding the fleet after the Pearl Harbor attacks, America needed a creative way to pack as much gear on each ship as it could.

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P-47s arrive in an Irish port while riding on a meccano deck on a tanker in World War II. (Photo: Government Printing Office)

Enter the “phantom deck,” also known as a “skeleton” or “Meccano” deck. Developed by the West Side Iron Works, these decks were frames built on top of the normal top deck of the ship. This allowed the vessel to carry up to 10 percent more cargo.

The decks were normally about 8 feet above the original top deck but could be as high as 15 feet. Separate platforms were bolted to holders to make the deck, and pad eyes were welded on so that cargo could be tied down.

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Planes stacked on the false deck of a liberty ship. Photo: Government Printing Office

The platforms were built so high to allow any large waves to wash across the original top deck without knocking cargo from the skeleton deck. The ships rode lower in the water due to the additional weight, and so were more vulnerable to waves.

While the modifications were originally introduced on normal cargo ships, they eventually were fitted onto tankers and any other large vessels making the trip across the ocean. The platforms and pad eyes could be quickly removed if the ship needed to be reconfigured or the platforms were needed on another vessel.

Tankers were generally kept in the center of a convoy so that they were better protected. So, additional cargo space on those ships was especially valuable.

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(Photo: The Mast magazine, April 1944)

More than 600 tankers received these false top decks and shipped over 20,000 aircraft to Britain in the final years of the war.

Because of the salt water, vehicles and planes on these false decks had to be coated with heavy lubricants or other chemicals to prevent corrosion. Before the Army learned this lesson, many of the tanks that arrived in theater needed extensive work to remove rust before they were fit for service.

When the war ended, the need for phantom decks subsided and the temporary innovations were removed.