[yarddog]

I read that an American submarine hit the Yamato fairly early with a single torpedo and it nearly sank.

The Japanese realized there was a real defect in it’s armor and put it in dry dock to correct it. I have no idea what it was.

I think it took 19 torpedoes to finally finish it off along with however many bombs etc.

[Nuc 1.1]

I think it was around 14 torpedoes for Yamato and 11 for Musashi. However I read about it in a book long long ago so the memory may not be exact. The book was called The End of the Imperial Japanise Navy. Aa great read with many rare photos. I highly recommend it.

[Darksheare]

Defective joint in the armor plate where upper and lower sidebelts met.
(USS Skate was the one who almost bagged her.)
And they had a philosophy of making the armor a structural member and part of the superstructure much like a wall joist.
U.S. ship armor was analogous of hung drywall.
So when the armor joint failed, it threatened to collapse the structure around it.
The advantage of doing it the way they did it: saved weight and space.

IJN Shinano had a defect that sent an I beam like a battering ram, bashing a hole from one boiler room to the next.
Even better, her watertight doors were rumored to be incomplete.

[packrat35]

https://www.youtube.com/watch?v=D7tzNfSGEnU

[tanknetter]

The Japanese realized there was a real defect in it’s armor and put it in dry dock to correct it. I have no idea what it was.

IIRC there were two basic problems with the Yamato-class armor. First, the armored box/citadel was too rigid. Second the armor itself was pretty brittle.

There's a big chunk of Yamato-class armor on display at the Navy Yard in Washington DC. It had been use for penetration tests by the 16" 45 caliber armor piercing shells used on the North Carolina and South Dakota-class battleships (the Iowas mounted 16" 50 caliber rifles, which could fire a "super-heavy" AP shell).

In looking at the armor section, from a distance you notice that it's been penetrated through by the round. But when you get close up you see that the section has also been severely fractured/spider-webbed by the hit. Which is much worse than the section just being penetrated.