Comparing Montana's bomb deck armor to Yamato's Question?

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petsan
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Comparing Montana's bomb deck armor to Yamato's Question?

Post by petsan » Tue Jan 24, 2012 12:38 pm

Comparing Montana's deck armor to Yamato's I have found a problem.....over and over I have read that it was better to concentrate deck armor against bombs

Question #1....Montana's 2¼" weather (Bomb) deck was laminated with either a ¾” thick STS the structural substrate, leaving the 1½” thick STS plates as deck armor used for protection or was the 1½” thick STS the structural substrate leaving the ¾” thick STS plates as deck armor used for protection?

Question #2....The Yamato used lighter "D" type armor for her two upper decks leaving the 7.8" to 9” Armor hard armor for her Armor deck, the Montana
used a thicker and heavier type 2¼" STS armor for her upper decks leaving a slightly thinner 7.05" to 7.35" Class B for her Armor deck.......Which was better
from an Aerial warfare perspective IE, if germany attacked your battleship at Malta with 550 and 1,100lb HE/SAP type bombs (carrier HMS Illustrious) which of the two would fare better (just hits...not talking about air defence guns)?

The "Never-built" Montana had a 2¼" weather (Bomb) deck of made up of two laminated plates
a (19mm) ¾” thick STS and (38mm) 1½” thick STS plates
The main armor deck Amidships-centerline was 7.05" Class B (147mm + 32mm) 5.8" on
1¼" STS structural substrate and Amidships-outboard was 7.35" Class B (155mm + 32mm)
6.1" on 1¼" STS structural substrate, and a third deck of 0.625" centerline (16mm) ¾” outboard (19mm)
......A total of 10.35" of steel at its maximum.

Yamato had
D steel 1/2"- outer 1.42" Weather (Bomb) deck (.79 OVER .63= 1"+ sts EQUIV)
.39" - outer 1" second deck (1" D STEEL = less than 1" sts EQUIV)
7.8" to 9” Armor third deck
1/4" Splinter deck over
.375 fourth deck

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Dave Saxton
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Re: Comparing Montana's bomb deck armor to Yamato's Question

Post by Dave Saxton » Tue Jan 24, 2012 2:52 pm

Question #1....Montana's 2¼" weather (Bomb) deck was laminated with either a ¾” thick STS the structural substrate, leaving the 1½” thick STS plates as deck armor used for protection or was the 1½” thick STS the structural substrate leaving the ¾” thick STS plates as deck armor used for protection?
I don't know how it would have been arranged on Montana, but it probably doesn't matter as the thicker of the two would have made up most of the effective thickness either way. In British testing they found that laminated plates in direct contact provides less ballistic protection than if the plates are spaced. Krupp used this formula for laminates: necessary velocity = (square root) V plate 1 (squared) + V plate 2 (squared)...ect...
Question #2....The Yamato used lighter "D" type armor for her two upper decks leaving the 7.8" to 9” Armor hard armor for her Armor deck,
D steel or Dulcol is not an armour grade steel. It is a British developed construction or structural steel. The ultimate tensile strength is only about 80,000 PSI and the elongation at that tensile strength is 17% (in 8"). It is not comparable to STS or other homogenous armours in terms of ballistic properties. The homogenous armour used for the main armoured deck, according to The Technical Mission to Japan reports, had the same chemistry and mechanical properties as British Non Cemented Armour used in the KG5s and Vanguard.
the Montana
used a thicker and heavier type 2¼" STS armor for her upper decks leaving a slightly thinner 7.05" to 7.35" Class B for her Armor deck.......Which was better
Ignoring that they were laminated decks in any evaluation of effective thickness for now, the splitting of the armour among two decks creates the possibility of induced yaw-provided that the space between them was great enough for the yaw to become manifest- and possible de-capping of armour piercing ordnance. This could make defeating the main armour deck more difficult despite a lesser effective thickness for the main armoured deck. In some USN documents the upper armour deck is referred to as a Yaw deck and not a "bomb deck."
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

petsan
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Re: Comparing Montana's bomb deck armor to Yamato's Question

Post by petsan » Tue Jan 24, 2012 7:13 pm

Thanks Dave,
I have Friedmansbook, Dulin Garzkes BB book, and assorted (warship int,sea classics) mags on Montana
and other than that and Internet searches is there any other place to get Montana info?

Keith Enge
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Re: Comparing Montana's bomb deck armor to Yamato's Question

Post by Keith Enge » Tue Jan 24, 2012 8:04 pm

petsan -
Siegfried Breyer's "Battleships and battlecruisers, 1905-1970" is an oldie but a goodie

Bill Jurens
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Re: Comparing Montana's bomb deck armor to Yamato's Question

Post by Bill Jurens » Sat Mar 17, 2012 10:42 pm

For what it is worth, the actual weather deck plating for the Montana design consisted of two 45# STS plates with no substrate below. The entire weather deck was covered except for a portion forward of the muzzles of the guns of Turret I. There was an irregular transition in thickness for a space of about 20 feet aft of that, from zero thickness of STS to one thickness of 45# plate and then to two. The bow was of 20.4# mild steel.

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Re: Comparing Montana's bomb deck armor to Yamato's Question

Post by lwd » Tue Jun 19, 2012 11:18 pm

I thought the purpose of the upper or bomb deck was to initiate the fuse on the bomb so that there was a good chance it went off before it even reached the main armored deck.

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