Hello, I am working on a screenplay set during World War 1 and am looking for diagram, schematic or blueprint of a U-31 class, ocean-going diesel-powered torpedo attack boat. My hero begins the movie as an engine room crewman and I would like to follow him through the ship. I would also like to identify the location of the bolt holding the external keel.

As a side note, my hero is based on my wife's grandfather, who served in just such a position during WW1. His boat was forced down by British destroyers and "ran aground," the keel stuck in the soft ocean bottom. After several attempts at "rocking" the boat by alternately filling and blowing port and starboard ballast tanks, they released the external iron keel. The boat rose quickly to the surface but without the keel they could no longer submerge and had to make it back to port on the surface - a dangerous task for a slow-moving boat with one forward gun.

Many thanks for any and all assistance. John