Naval sub History - interesting!!

[Vorkapitan]

Hi mates,
Thought you might be interested in this trivia!!
More info: http://en.wikipedia.org/wiki/I-400_class_submarine

"It was seven minutes before midnight on August 28, 1945, when a large unidentified object appeared on the radar screen of USS Segundo, a Balao-class submarine on patrol south of Japan. It had been 13 days since Japan’s sur­ren­der an­nounce­ment, and Segundo’s commanding of­fi­cer, Lieu­tenant Commander S.L. John­son, was on the lookout for remnants of Japan’s naval fleet. Segundo was 18 days out from Midway, and except for an en­coun­ter with a Japanese fishing boat, the patrol had been uneventful.
Soon after Segundo changed course to intercept the blip, Commander Johnson and his men realized they were on the trail of a Japanese submarine. After tracking the sub for more than four hours, Johnson tired of the cat-and-mouse game and radioed for it to stop, receiving a positive acknowledgement in reply. But as Segundo closed in, Johnson and his crew were literally in for a big surprise.
The vessel 1,900 yards off their bow was not your average Japanese submarine; it was I-401, flagship of the I-400 class known as Sen-Toku, or special submarines. At the time I-400s were the biggest submarines ever built, and they would remain so for nearly 20 years after the war. The sub Commander Johnson intercepted simply dwarfed Segundo.
Johnson and his men were about to discover that they’d happened upon one of the war’s most unusual and innovative weapon systems. Not only was I-401 bristling with topside weaponry, the sub was also designed to carry, launch and retrieve three Aichi M6A1 Seiran floatplane attack bombers. In other words, I-401 wasn’t just a major offensive weapon in a submarine fleet used to playing defense—it was actually the world’s first purpose-built underwater aircraft carrier.
Japan’s I-400 subs were just over 400 feet long and displaced 6,560 tons when submerged. Segundo was nearly 25 percent shorter and displaced less than half that tonnage. Remarkably, I-400s could travel 37,500 nautical miles at 14 knots while surfaced, equivalent to going 1½ times around the world without refueling, while Segundo could travel less than 12,000 nautical miles at 10 knots surfaced. I-400s carried between 157 and 200 officers, crew and passengers, compared to Segundo’s complement of 81 men.
The I-400s boasted a maximum speed of 18.75 knots surfaced, or 6.5 knots submerged. They could dive to a depth of 330 feet, shallower than most U.S. subs at the time, and had a draft of 23 feet—fairly deep but hardly surprising given the sub’s size.
Nevertheless, the I-400s were to submarines what the Yamato class was to battleships. They carried Type 95 torpedoes, a smaller version of the Type 93 Long Lance torpedoes, the most advanced used by any navy in the war. The oxygen-powered 95s traveled nearly three times farther than the American Mark 14s, carried more explosive punch, left virtually no wake and were the second fastest torpedoes built during the war (Type 93s were the fastest). They were launched from eight 21-inch forward torpedo tubes, four on each side (two upper and two lower). Unlike U.S. subs, I-400s had no aft torpedo tubes, which could prove a shortcoming in certain situations, but topside they were all business, with one 5.5-inch rear- facing deck gun, three triple-barrel 25mm anti-aircraft guns on top of the aircraft hangar and a single 25mm gun on the bridge."

Just one opinion but I think that the I-400's and big diesel boats in general (Surcouf, M-Class, the dirty K's from WW1 as other examples) have been the subjects of too many historical urban myths and legends. They were tactically dangerous and strategically useless when all is said and done. Leaving aside any prejudice against wikapedia history, the sensationalized tone of the article is enough to put one off ones lunch. To wit:

it was actually the world’s first purpose-built underwater aircraft carrier.

A failed concept that was tried in the twenties and rejected as unsafe, unsound and impractical.

I-400s carried between 157 and 200 officers, crew and passengers, compared to Segundo’s complement of 81 men.

There's a totally useless statistic in the context of the narrative so one has to assume the author intended the reader to be awed by mere numbers. Note, no mention of any advantages that having 157 men all competing for oxygen in the confines of a big suberged diesel boat might provide.

Nevertheless, the I-400s were to submarines what the Yamato class was to battleships.

Got something correct here, they were entirely useless as weapons when they slid off the stocks. With the added bonus that large-size made the WW2 submarine more vulnerable and so less effective.

It took some 8-minutes to dive an I-400, longer if the hanger was in use as I understand it and surfacing off the U.S. coast or the Panama Canal zone to attack with three floatplanes (or even nine from all three I-400's)is a tactic not worth the fuel to get them there. It's not even desperate, just strategically stupid.

Look past the hype; these were badly flawed ships built for an impossible fantasy mission by an arm of service lacking an effective and cohesive doctrine throughout its entire existance. The I-400 boats added nothing to the technology of the submarine and the U.S. Fleet Boat was an infinitely superior warship by any objective, measurable yardsticks.

See Submarine Commander Cdr. Paul Schratz, USN (ISBN 0-8131-1661-9). In 1945 then LCdr Schratz captained the Japanese high-speed (Sen Taka) I-203 from occupied Japan to Hawaii for testing by the USN. His impressions of this most sophisticated sub in the IJN as seen through the eyes of an experianced Fleet Boat XO make interesting reading.
Good Hunting

Edited for typos

[Bronzewing]

Don't use the K class as an example of a big diesel boat. They were nothing of the sort.
Big yes, diesel no. The K class have the dubious distinction of being the world's first operational class of steam submarines (complete with folding boiler room funnels).
The K class were AWFUL boats, the only thing any of them ever sank was each other (K4 sank K1, K6 sank K4). Both due collisions stemming from the rather insane idea of using high speed submarines with the speed of a destroyer, the turning circle of a battlecruiser and the bridge control facilities of a picket boat as part of battlefleet formation manouvers.
something of their character can be seen from my signature, which is a quote made originally by a K boat skipper.

You're correct about the Dirty K's, I wrote them in as an afterthought because they were both big and unsuccessful. The wikipedia article quoted stressed the size of the I-400's, implying that somehow size = effectiveness. Including the K's made sense to help debunk that contention but I did fail to mention that they were steam/electric. You're referring to the 'Battle of May Island' of course, night 31 Jan - 01 Feb 1918 but you never mentioned the three K's damaged when the BCF came up.

As for being first operational steam powered submarines, the four Triton class (built 1898-1903, 200t submerged, one heavy oil boiler with triple expansion engine and four external 18" torpedo launchers) were in operational and flotilla service with the French Navy well before WW1.

Good Hunting

[Laufen zum Ziel]

Thanks for shareing.