I-400 sized German U-boat projects from WW2?

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Vahe Demirjian

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The I-400 was the biggest ever submarine built in WW2 and the largest until the advent of the nuclear powered ballistic missile subs, but the Regia Marina is not known to have built any gigantic submarines because it was pounded big time in the November 1940 Battle of Taranto. However I wanted to ask if the Kriegsmarine had plans for U-boat designs rivaling or approaching the size of the I-400 because one of the schemes for Hitler's plans to attack Manhattan included launching V-2s from U-boats.
 
To my knowledge (and to that of Erich Gröner), the biggest submarine designed for the Kriegsmarine was the "U-Kreuzer" Typ XI, which
nevertheless wasn't much bigger, than about half size of the I-400. For the kind of missions and the areas, German Uboats were designed
for, very big probably wouldn't have been an advantage.
And the plans for attacking the USA with V2 rockets, were made around towed launch containers.
https://www.secretprojects.co.uk/threads/prüfstand-xii-submarine-launched-v-2-rockets.9651/

(drawing from Erich Gröner "Die deutschen Kriegsschiffe 1815-1945", volume 3)
 

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Largest sub designed by Germans in WW2 was a 4000 ton cargo submarine, a 1943 project by eng. Kohr with multiple pressure hull a length of 93 meters and a width of 11 meters. Still considerably smaller than I-400 class. Something larger was studied during WW1 in the context of cruiser-submarine experimentation. However Regia Marina had actually a mid '30 plan for a much larger submarine, a 10000 ton submarine oil tanker to evade naval blockade 15622260149613431595259235424215.jpg
 
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Actually there were two for the German Navy:
From 1929 a 3.000ton cruiser submarine, no dimensions given but a 10.000shp engine would drive it 41km/h on surface, armament would be 2 single 15cm and 2 single 8,8cm guns
2 twin and two single 533mm torpedo tubes and a light armour of 30mm.
The other was a slightly earlier project from 1928 by the engineer Oswald Flamm:
25.000shp 3 shaft Diesel-Electric engines, 7.067tons displacement, again no dimensions, armament were: 2x1 21cm guns, 4x1 8,8cm guns and 2x2 53cm torpedo tubes with a 45mm armour.
 
Tzoli said:
Actually there were two for the German Navy:
From 1929 a 3.000ton cruiser submarine, no dimensions given but a 10.000shp engine would drive it 41km/h on surface, armament would be 2 single 15cm and 2 single 8,8cm guns
2 twin and two single 533mm torpedo tubes and a light armour of 30mm.
The other was a slightly earlier project from 1928 by the engineer Oswald Flamm:
25.000shp 3 shaft Diesel-Electric engines, 7.067tons displacement, again no dimensions, armament were: 2x1 21cm guns, 4x1 8,8cm guns and 2x2 53cm torpedo tubes with a 45mm armour.
Click to expand...
Ok, first is typ XI, but do you have a name of second one? Link you posted below is broken.
 
ceccherini said:
Largest sub designed by Germans in WW2 was a 4000 ton cargo submarine, a 1943 project by eng. Kohr with multiple pressure hull a length of 93 meters and a width of 11 meters. Still considerably smaller than I-400 class. Something larger was studied during WW1 in the context of cruiser-submarine experimentation. However Regia Marina had actually a mid '30 plan for a much larger submarine, a 10000 ton submarine oil tanker to evade naval blockade
Click to expand...
Which book is this?
 
Vahe Demirjian said:
The I-400 was the biggest ever submarine built in WW2 and the largest until the advent of the nuclear powered ballistic missile subs, but the Regia Marina is not known to have built any gigantic submarines because it was pounded big time in the November 1940 Battle of Taranto. However I wanted to ask if the Kriegsmarine had plans for U-boat designs rivaling or approaching the size of the I-400 because one of the schemes for Hitler's plans to attack Manhattan included launching V-2s from U-boats.
Click to expand...
No, not to my knowledge. The "Rocket U-Boats" you mention were planned to be of conventional size (built upon or converted from existing U-Boats). The rockets would have been towed in small, watertight containers behind the submarine, then surfaced and positioned vertically for launch. Launching something like a V-2 from the deck of the submarine would have been extremely dangerous; one wrong move and the entire ship heads to Davy Jones's Locker.

Below is a diagram of the towable rocket container:
1746453555370.png

Now back in WWI, they developed something known as the "Projekt 50", which appears to be a steam powered submarine of goliath proportions (larger than the aforementioned I-400), discussed in this thread: https://www.secretprojects.co.uk/threads/german-ww1-steam-u-cruiser.3963/#post-31196
 
Absolutely incredible find, moin. I will start a separate thread.
 
Goodmorning,
Anyone able to supply me a (digital) copy of an article written in the German published magazine Marine Rundschau in 1924 by Oswald Flamm dealing with his caluclations of submarines? Probably the last edition of 1924
 

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