Hi Rainer,

Perhaps I am misnaming my features. Stern's book displays a number of photos of the various section of the U-boat before welding/assembly. One photo of the control room section has a caption which points out the transverse bulkheads at either end of the section, before the watertight doors have been cut out. Additionally, there is a concave bulkhead that divides the cylinder (control room section) in half along its longitudenal dimension.

regards,

Robert