Mine laying capabilities of the Japanese I-121 class

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Fatboy Coxy
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Mine laying capabilities of the Japanese I-121 class

Post by Fatboy Coxy » Tue Feb 16, 2021 6:06 pm

Hi guys, I have a couple of questions on the minelaying capabilities of the Japanese I-121 class submarines. Four were built, I-121, I-122, I123 and I-124 between 1924-1928, each capable of carrying up to 42 mines.

Did they carry these mines internally, or externally, and if internally, did they have to lay them while on the surface?

Fatboy Coxy
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Re: Mine laying capabilities of the Japanese I-121 class

Post by wadinga » Fri Feb 19, 2021 7:12 pm

Hi Fatboy,

According to various sources these boats were copies of the German U-125 minelayer ceded to Japan as part of the Versailles Treaty. U-125 sometimes gets confused with UB-125, also ceded to Japan, but this was a shorter coastal boat with no minelaying capability.

UB-125 was designated O-6 in the Japanese Navy and scrapped at Kure in 1921.

U-125 was designated O-1 and broken up at Kure 1922. She carried 42 mines in two 1 metre diameter horizontal tubes which discharged below the waterline at the stern. However, additionally there were storage racks for a further 30 mines on the upper deck with rails to the launching tubes. I get the impression the tubed mines could be launched underwater, and the reloads transferred from the deck needed to be done whilst surfaced. Presumably these deck racks on the Japanese versions were used to store the aviation fuel in their additional role as "range extenders" for reconnaissance float planes from 1940 onwards.

Hope this helps

All the best

"There seems to be something wrong with our bloody ships today!"

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