View attachment 176139
Also measured on the other axis
View attachment 176140
I also did measure this thing, assuming it is what I think it is, ie the pressure hull cap, based on
@Maikeru's measurement of the smaller hull section I get around 12.7m in diameter accounting in for the picture being at an angle which could make it appear abit larger, it could be reasonably inferred that the "cap" is somewhere around ~12m in diameter.
IMO possible hybrid hull instead of double? Also, this does give a more reliable estimate for the beam of the submarine at 12-12.5m.