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Thread: Iowa class torpedo protection

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    Iowa class torpedo protection

    Looking at the drawings of the Iowa-class ships, it seems that abreast of turret 1, the torpedo protection system is not as deep as other parts of the ship? Are the powder magazines of the ship directly next to the last holding bulkhead (BHD #4)? It seems pretty dangerous for the torpedo system to thin right by the magazines.

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    Defense Professional RustyBattleship's Avatar
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    Quote Originally Posted by Radical View Post
    Looking at the drawings of the Iowa-class ships, it seems that abreast of turret 1, the torpedo protection system is not as deep as other parts of the ship? Are the powder magazines of the ship directly next to the last holding bulkhead (BHD #4)? It seems pretty dangerous for the torpedo system to thin right by the magazines.
    There is no reduction of torpedo protection. The booklet does not show the extend of the Class B armor BELOW the Class A armor that tapers down to the Innerbottom. The Hull starts narrowing as it goes forward. The Iowa class Battleship hulls are actually an extended Cruiser hull. So the narrowing is ONLY in the shape of the shell plating. Otherwise, up to bulkhead 50 and on back to bulkhead 166 the inner torpedo, falling shot, armor arrangement is the same.
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    Thought of this thread today after reading a story about the USS Porter "Willie Dee" where the author takes huge literary license to talk about how that one torpedo launched almost sunk and killed FDR. Talk about a glass jaw...

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    Defense Professional RustyBattleship's Avatar
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    Quote Originally Posted by tbm3fan View Post
    Thought of this thread today after reading a story about the USS Porter "Willie Dee" where the author takes huge literary license to talk about how that one torpedo launched almost sunk and killed FDR. Talk about a glass jaw...
    Ummm, no. One torpedo would not sink the Iowa. However, when FDR heard that a torpedo had been launched from a Destroyer, he first thought it was part of the weapons demonstration that the Navy was staging for him. Therefore, to satisfy his curiosity, he moved his wheelchair over to the railing to watch the torpedo. Well, the secret service men realized it was not a demonstration and pulled FDR away from the starboard side to the port side. Supposedly, one of the agents even drew his gun. Now, I don't know what a .38 caliber snub-nose revolver would do to a torpedo, but you have to give that agent kudos for instinctive reflexes.

    Even Delano Roosevelt (FDR's grandson) who has worked with us and is a founding member of the Pacific Battleship Center laughs about it every time the incident is brought up.

    Seriously, however, if the torpedo hit the side of the ship just below where FDR was looking over the life rails, that geyser of water would certainly have done unimaginable harm to him.
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    Looking at the drawings from the Booklet of General Plans, it seems like Missouri's torpedo holding bulkheads are 3/4" but the New Jersey is 5/8"? Why did the thickness increase for Missouri?

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    Defense Professional RustyBattleship's Avatar
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    Quote Originally Posted by Radical View Post
    Looking at the drawings from the Booklet of General Plans, it seems like Missouri's torpedo holding bulkheads are 3/4" but the New Jersey is 5/8"? Why did the thickness increase for Missouri?
    The Iowa and New Jersey were designed to stay within the weight limits of the London Treaty. When we discovered that the German Bismarck class and the Japanese Yamato class totally ignored the treaty. Monkey see, Monkey do. Our enemies did not follow the Treaty so we didn't have to either. Therefor the holding bulkheads, the splinter deck and 40mm guntubs were all increased in thickness from 5/8" to 3/4" (or more in some cases) for the Missouri and Wisconsin.

    During modernization I added 1/4" to 1/2" HY-80 armor on top of existing 1" STS armor. New deck houses were built of 3/4" to 1" thick HY-80 armor. We converted a barracks compartment into a communication center and added 1" thick HY-80 armor over the existing 1/4" to 3/8" bulkhead and deck plating. The new Combat Engagement Center gave me a bit of challenge as I added 1 1/2" thick HY-80 armor to outer bulkheads that did not have a continuous deck to support their weight. Don't forget, 1 1/2" thick steel weighs 61.2 lbs per square foot. Just imagine our riggers and shipfitters hulking in a 5-foot wide by 7 1/2 foot tall plate of armor steel weighing 2,142 lbs -- EACH.

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    Was the original 5/8" torpedo holding bulkheads not enough for something? I was under the impression that you don't want your bulkheads to be too stiff or thick to prevent rupture, and some compartments are liquid loaded as well.

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    Defense Professional RustyBattleship's Avatar
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    Quote Originally Posted by Radical View Post
    Was the original 5/8" torpedo holding bulkheads not enough for something? I was under the impression that you don't want your bulkheads to be too stiff or thick to prevent rupture, and some compartments are liquid loaded as well.
    Believe it or not, 3/4" thick steel is cheaper by the square foot than 5/8" still. To squeeze down that extra 1/8" takes another heating of the plate to reset the rollers for the lesser thickness.

    Besides, on warships the thicker steel is better. BUT, you must also design the ship to still be able to float. If you use too much heavy steel for strength and/or armor, it would soon become an anchor.
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    Quote Originally Posted by RustyBattleship View Post
    Believe it or not, 3/4" thick steel is cheaper by the square foot than 5/8" still. To squeeze down that extra 1/8" takes another heating of the plate to reset the rollers for the lesser thickness.

    Besides, on warships the thicker steel is better. BUT, you must also design the ship to still be able to float. If you use too much heavy steel for strength and/or armor, it would soon become an anchor.
    What I mean is that torpedo holding bulkheads are meant to be relatively thin and elastic and have some "give" to absorb the shock of a detonation. Too thick or rigid would have the bulkhead rupture at the keel or near the top. I think Yamato had this problem with its lower belt. But is 3/4" determined to be better than 5/8" for the holding bulkheads?

    By the way, how is the upper and lower belt of the Iowa attached?

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    Quote Originally Posted by RustyBattleship View Post
    The Iowa and New Jersey were designed to stay within the weight limits of the London Treaty. When we discovered that the German Bismarck class and the Japanese Yamato class totally ignored the treaty. Monkey see, Monkey do. Our enemies did not follow the Treaty so we didn't have to either. Therefor the holding bulkheads, the splinter deck and 40mm guntubs were all increased in thickness from 5/8" to 3/4" (or more in some cases) for the Missouri and Wisconsin.

    During modernization I added 1/4" to 1/2" HY-80 armor on top of existing 1" STS armor. New deck houses were built of 3/4" to 1" thick HY-80 armor. We converted a barracks compartment into a communication center and added 1" thick HY-80 armor over the existing 1/4" to 3/8" bulkhead and deck plating. The new Combat Engagement Center gave me a bit of challenge as I added 1 1/2" thick HY-80 armor to outer bulkheads that did not have a continuous deck to support their weight. Don't forget, 1 1/2" thick steel weighs 61.2 lbs per square foot. Just imagine our riggers and shipfitters hulking in a 5-foot wide by 7 1/2 foot tall plate of armor steel weighing 2,142 lbs -- EACH.

    Just another day doing our job.
    Curiously the Booklet of General Plans (https://maritime.org/doc/plans/bb63.pdf) for Missouri shows splinter deck of only 25# STS, which is 5/8". Do shipbuilders not follow these explicitly sometimes?

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    Military Professional JCT's Avatar
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    Quote Originally Posted by Radical View Post
    Curiously the Booklet of General Plans (https://maritime.org/doc/plans/bb63.pdf) for Missouri shows splinter deck of only 25# STS, which is 5/8". Do shipbuilders not follow these explicitly sometimes?
    Ha! You should see today's shipbuilders. Two ships built at the same time in different shipyards using identical plans (I have to assume this as I do not truly know, but if you are both building a Flight IIA Burke DDG at the same time, I'm going to assume my assumption is correct - but my assumptions have shown me to be an @ss at times) are remarkably different in the details. A massive group of cable runs going through a compartment use wildly different paths. A rack of radios is located 6" farther to port on one ship. Some ships have a desk in this corner, some have a truncated desk, and 6 out of 50+ ships do not have one at all. And this is just in Combat!

    Fast forward a few years as various different alterations are made to each ship, the differences begin to increase and begin to multiply as differences between two ships force what should be an identical equipment installation to be installed differently in almost every ship. Makes configuration management a nightmare.

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