Weekly Submarine Mystery - One Question

November 19, 1981 - The New York Times - Submarine Tanker Plans -

"General Dynamics Corporation disclosed that it was discussing with several West German shipbuilders plans to build 28 submarine tankers to carry liquefied natural gas from the Arctic to North America and Europe. ... General Dynamics said that it had designed two versions of the tanker submarines, a $725 million nuclear-powered ship and a $700 million version powered by methane."

Germany's history already includes commercial submarines. The Deutschland had been built in 1916 to counter Britain's naval blockade in WW1. The blockade had hindered Germany's war efforts sub- stantially. ---------------------------------------------------------------------------------------------

Two subs were intended to travel to the neutral United States selling goods in exchange for vital raw materials. Britain and France soon protested submarines used as merchant ships, arguing that they could not be inspected (for munitions) like surface shipping. The U.S. rejected this argument, declaring unarmed submarines merchant vessels. [1] ----------------------------------------------------------------------------------

Deutschland's third journey, planned for January 1917, was aborted when the U.S. abruptly entered the war against Germany due in part to anger over German submarines sinking shipping bound for Great Britain just beyond U.S. territorial waters. The German Imperial Navy converted Deutschland to a submarine cruiser (U-155), a type submarine fitted with added artillery. In three war cruises, Deutschland was subsequently credited with sinking 43 ships. ---------------------------------------------------------------------------------------

Becoming a British war trophy in December 1918, Deutschland was scrapped in 1921. Her sister ship, the Bremen, launched its first journey in August 1916 under Karl Schwartzkopf, but never arrived in the US. Its fate is not known with certainty. source

The mystery question:

There were a total of eight boats of Deutschland's merchant class subs built, plus Bremen. Because of their original, merchant design, there were only two 20-inch torpedo tubes both in the bow. How heavy was their surface gun battery? Answer Monday.