Sinpo Sub Brief handed over to Research Team

Jones's article does write that the Type XVII stored hydrogen peroxide inside a figure-8 pressure hull, to my surprise. 1940s submarines often stored diesel fuel outside the pressure hull in floodable tanks within the outer hull. HMS Explorer and Excalibur stored hydrogen peroxide in plastic bladder tanks outside the pressure hull. Pressure hull volume is expensive in terms of weight, as the structure must resist hydrostatic pressure at depth.

Fascinating - when the pandemic lifts, someday I want to travel to Bremerhaven and see the Wilhelm Bauer museum ship.

Lots of great info, thanks!

Andrew MacDougall

The torpedoes are not fixed in their racks but on light weight cradles that can slide up/down the racks. The torpedo load out for the XXI was 20 torpedoes, 6 in the tubes and 14 on the racks, however the racks had space for 17. Three cradles were left empty to allow servicing of the torpedoes in the tubes, hence the 8/5 arrangement on the diagram. If the torpedoes in the tubes on the 8 side needed servicing, the 3 torpedoes on the end in the rack were moved to the empty positions and then the torpedoes in the tubes were pulled out.

Interesting that Section A seems to show asymmetric torpedo stowage. I count 5 on one side, 8 on the other (not the tubes, but stowage).

Andrew MacDougall

Nope, it is a figure 8. But I will give you that the bottom loop of the 8 is smaller and only runs 2/3 of the length of the top one. Have a look at https://en.m.wikipedia.org/w/index.php?title=File:SRH025-p40.jpg&mobileaction=toggle_view_mobile for a Type XXI submarine diagram with cross sections. Also this https://en.m.wikipedia.org/w/index.php?title=File:Type_XXI_section.jpg&mobileaction=toggle_view_mobile is a great photo showing that the pressure hull is not a conventional circular cross section.

BG213 Have a look at Jones, Marcus O. (2014) "Innovation for Its Own Sake: The Type XXI U-boat," Naval War College Review : Vol. 67 : No. 2 , Article 9. Available at https://digital-commons.usnwc.edu/nwc-review/vol67/iss2/9, pages 5-6 (or 121-122 if you’re looking at the page numbers at the top of the page). For others and B213 if you don't have the time to download and read (a very cut down summarisation): The author (Jones) puts forward that the XXI (Type 21) design has its origins with the experimental submarine V-80 and the XVIII (Type 18) design. V-80 was the platform for propulsion engineer Helmuth Walter’s AIP (Hydrogen Peroxide), XVIII had the AIP and improved hydrodynamic hull. The hull of XVIII was a figure 8 design, with the lower section of the 8 used to store the large amounts of Hydrogen Peroxide required to fuel the AIP. In a November 1942 meeting on U-boat design projects the director of naval construction and a pair of engineers came up with the concept to utilise the hull design of the XVIII to house a standard electric propulsion system, with the Hydrogen Peroxide storage replaced by an increase in battery capacity. The concept was developed further, with the end result being the XXI.

Actually they didn't the cross-section of a XXI is a "conventional" crucialr typ!!!

Interesting. I wonder why the germans did that.

Andrew MacDougall

An important difference between the Type XXI and Romeo classes is that the Type XXI's pressure hull had a figure-8 cross section, like two conjoined cylinders. I believe the Romeo's pressure hull has a circular cross-section throughout it's length, although my sources are unclear. Foxtrot- and Zulu-class submarine pressure hulls had circular cross-sections.

Ha ha, I was about to say the same thing! The Type XXI just won't die. Speaking of U-boats I've been watching some videos about the U977 and U530 and their mysterious goings on off the coast of Argentina.

Andrew MacDougall

You are right!

Aaron Amick

Aren't the Romeos an improvement of the German type 21 after the Soviets got their hands on them? Or am I wrong?