American SH shells - Famed or Folly

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Bill Jurens
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Re: American SH shells - Famed or Folly

Post by Bill Jurens » Mon Dec 09, 2019 12:27 am

I like your definition of 'balanced'. It's at least something to jump-off from. Can you provide a primary USN source which would support that usage?

Bill Jurens

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Re: American SH shells - Famed or Folly

Post by Ski206 » Sun Dec 15, 2019 4:54 pm

Bill Jurens wrote:
Mon Dec 09, 2019 12:27 am
I like your definition of 'balanced'. It's at least something to jump-off from. Can you provide a primary USN source which would support that usage?

Bill Jurens
Mr. Jurens,

My understanding of the topic comes from Friedman’s US Battleships an Illustrated Design History. His sources are of course a treasure trove of documents from the period.

I’m on the road (again) so don’t have my copy in front of me but I suspect that the USN never had a hard formal definition of what exactly constituted “balanced” in design parlance. My sense from the reading I’ve done (and I’m an amateur most of whose knowledge comes from reading books and the like and thus secondary vice primary sources). It seems like in the early days of battleship design that Armour was applied in a less than scientific fashion. As technology evolved we see the concept of an immune zone coming into play which leads to a more scientific analysis of what’s exactly required in the way of armor to provide meaningful protection. I know based on Friedman that the USN considered most of its WWII BB’s to be unbalanced because they lacked useful immunity zones against the guns and shells they used. This of course was a by product of technology that was evolving as the ships were designed and built first with the switch to 16” guns in the North Carolina’s and then the creation of the SH 2700 lb AP shell that unbalanced the Iowa’s and South Dakota’s.

This of course leads to the question of what constitutes a useful zone of immunity and I very much doubt that you would find that the USN had a specific design goal for this. And by specific design goal I mean a formal board policy that specifies that USN BB’s should be designed to have a zone of immunity of not less than x yards against the designed gun and shell combination. If such a goal existed you would expect it to have been a major driver in ship design and thus I would have expected Friedman to have noted it at some point. The SD class started with a 13.2k yard wide zone (based on the data from my last post which I have not confirmed) that was considered balanced and ended with a zone 5.9k yards wide that was considered unbalanced. I’d have to go back and see if I can find the design numbers for any of the other ships (like NC vs her original 14” guns) which would give us some indication of the ranges that were normally in play. I suspect that the immunity zone was a bit of a moving target as technology and thus expected battle ranges changed and thus the ranges at which ships needed protection.

So if you return to what I posited in my last post the key question seems to be what is a “useful” zone of immunity (at least in USN terms). And that’s a question I don’t have an answer to. But I would argue that the answer should lie in the ranges at which you expect to fight the enemy because you’d certainly want to design a ship whose armor can protect its vitals at those ranges.

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Dave Saxton
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Re: American SH shells - Famed or Folly

Post by Dave Saxton » Tue Dec 17, 2019 4:02 pm

The NC's IZ was from 18,000 yards to 28,000 yards vs the new 14"/50 firing a 1500 lb projectile. (see G&D)

Malcolm Muir, in his book The Iowa Class Battleships included the IZ specs in an appendix as well as including some commentary in the General Board minutes about IZ that you may find helpful:
I, Vertical Armor:
A, Belt armor: To be internal armor of sufficient thickness, tapered and sloped at the most suitable angle, to give protection at 18000 yards against the 16-inch 45 caliber 2240 lb armor piercing projectiles at 90 degree taget angle....
....(b) Second deck (protective deck)-As necessary with main deck (upper deck) to give protection at an outer limit of 30000 yards against the 16-inch projectile mentioned above. .....
Admiral Greenslade: In as much as we are finding it almost impossible to protect our ships (The Montana class design) against the 16"/50, what enemy could put 18-inch guns on a ship and protect it (against 18-inch shells)?

Admiral Furlong: They could not protect it against our 16"/50.
It is apparent that they were willing to accept designs with inadequate protection, or a very narrow IZ, against the ship's own gun. Perhaps they were gambling that an enemy would not develop guns of equal or superior capability, or that they could hit first and more often. Also note that the IZ inner and outer limits they worked with were 18k to no more than about 30k.
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.

Byron Angel
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Re: American SH shells - Famed or Folly

Post by Byron Angel » Sat Dec 21, 2019 5:51 pm

Interesting discussion. It seems to me that, while the IZ is a valid concept, it is also a distinctly ephemeral one, valid only until the introduction of the next larger main battery caliber or improvement in projectile quality.

Season's greetings to all.


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