A Question concerning AP Bombs at Pearl Harbor

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A Question concerning AP Bombs at Pearl Harbor - 11/15/2015 5:17:09 PM

Gregg

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I just finished rereading a old book about Pearl Harbor "Pearl Harbor: Why, How, Fleet Salvage and Final Appraisal". This book was published in 1968 by the US Government Printing Office. I remember first reading it while I was in college, about 1969.
Through out the book, the author Vice Admiral Homer N. Wallin (who was in command of the salvage effort at Pearl Harbor) kept referring to Armor Piercing Bombs dropped on Battleship Row as converted 15 inch AP projectiles. The Japanese had no Battleships with 15 inch guns. I was under the impression the AP Bombs were converted 16 inch AP Projectiles.
Interesting note, most if not all of the said bombs dropped were either duds, or yielded only low order detonations. It appears only one of these AP Bombs was recovered intact, a dud found in the West Virginia. Parts of a second dud were recovered from inside the number three main gun turret on the West Virginia. This bomb broke up upon impact on the turret roof, and then striking one of the guns with in the turret. If they did recover one bomb intact, why do they keep referring to it being a converted 15 inch projectile?
Gregg

< Message edited by Gregg -- 11/15/2015 6:18:39 PM >

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RE: A Question concerning AP Bombs at Pearl Harbor - 11/15/2015 5:33:31 PM

geofflambert

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Here's a site that disagrees with battleship shells being used.

http://www.pacificaviationmuseum.org/pearl-harbor-blog/pearl-harbor-the-bombs-of-the-second-wave

I've heard the same as what you read. I think 16 inch shells were too heavy, but someone will know about that. I'm going to check to see if they had 15" CD guns.

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RE: A Question concerning AP Bombs at Pearl Harbor - 11/15/2015 6:16:28 PM

Puhis

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This is screenshot from Japanese Bombs, "Intelligence Targets Japan" (DNI) of September 1945. U.S. Naval technical mission to Japan.

According that report, it was 40 cm AP shell.
EDIT: I think the japanese 16 inch gun was actually 41 cm (isn't that diameter below 409 mm?)

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< Message edited by Puhis -- 11/15/2015 7:24:36 PM >

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RE: A Question concerning AP Bombs at Pearl Harbor - 11/15/2015 7:18:55 PM

Gregg

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Well, 40 cm equals 15.6 inches.

Gregg

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RE: A Question concerning AP Bombs at Pearl Harbor - 11/15/2015 7:33:22 PM

spence

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The 800kg bombs functioned very poorly at Pearl Harbor. One one actually performed as hoped for rendering Arizona a total wreck. The bombs were intended to damage the inboard battleships sufficiently to put them out of action for 6+ months. Inboard battleships Tennessee and Maryland however suffered only minor damage. In fact the dud/low order detonation rate of the 800kg AP bombs was 60%.

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RE: A Question concerning AP Bombs at Pearl Harbor - 11/15/2015 7:50:06 PM

Puhis

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quote:

ORIGINAL: Gregg

Well, 40 cm equals 15.6 inches.

Gregg

And 409 mm equals 16.1 inches.

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RE: A Question concerning AP Bombs at Pearl Harbor - 11/15/2015 7:54:33 PM

witpqs

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It's a little tough to see, but I think the diagram does say 409 mm.

The other interesting thing is the high dud rate in spite of the diagram noting TWO tails fuses to ensure detonation! I wonder if that was a post-Pearl Harbor modification?

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RE: A Question concerning AP Bombs at Pearl Harbor - 11/15/2015 11:35:34 PM

Gregg

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quote:

ORIGINAL: witpqs

It's a little tough to see, but I think the diagram does say 409 mm.

The other interesting thing is the high dud rate in spite of the diagram noting TWO tails fuses to ensure detonation! I wonder if that was a post-Pearl Harbor modification?

No, the photo of the bomb found in the West Virginia clearly shows two fuse holes on the base.

As to the Arizona, the US Naval Institute in its magazine "Proceedings" had a detailed article many years go about exactly what happened to the Arizona. The bomb hit next to one of the forward turrets (I think that was turret number 2), and penetrated the first and second decks, then the armored third deck, either into or next to the Black Powder Magazine. The bomb detonation was enough to set off the black powder magazine, that was located next to the 14 inch powder magazine. The rest is history.
Black powder was used onboard for at least three things that I know of: First, the signal guns used for saluting used black powder charges. Second, the airplane catapults used a black powder charge to launch the airplane. Third, they used small bags of black powder in the big cordite main gun bags, to light off the cordite charges. They were still doing that on the Iowa class Battleships right to the very end. Originally it was thought a black powder bag was the cause of the number two turret gun explosion on the Iowa. Black powder is very easy to ignite.
Gregg

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RE: A Question concerning AP Bombs at Pearl Harbor - 11/16/2015 2:43:49 AM

geofflambert

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I have read that compressed air catapults were replaced with black powder powered ones but not why. Steam catapults came next didn't they?

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