US battleship secondary gun arrangement question

[Scott Kenny]

I've been looking at various US ship designs and came to an odd question about why the battleships kept all their secondary mounts on the sides and didn't shift a pair of turrets to sit on the centerline like the cruisers did. It would allow at least one extra turret to fire into a broadside (20% increase in broadside weight), and that's assuming that people kept 10 total mounts instead of making it 12 mounts.

I've seen an early design sketch for the SoDaks (on wikipedia) that had this arrangement, and I'm curious why it wasn't pursued.

From wiki:

(This particular version actually only has 8 secondary turrets instead of 10.)

Was it really the increased length of the Citadel that hurt the centerline secondary turrets? Could it have been topweight? I just don't have the education or references to begin to look.

 

[johnpjones1775]

I’d assume topside weight might have something to do with it.

 

[Yellow Palace]

Generally, centreline length is a major consideration for warships. There are lots of disadvantages, and few advantages, to making a ship longer than necessary. Anything that can be pushed out to a beam generally is.

Centreline secondary mounts only really make sense if the ship needs to be particularly long (generally for speed), or you want to minimise weight for some reason. In the former case, the centreline space is less restricted, and in the latter, you're probably giving up something else that's less important to you than the secondary battery.

The major advantage of centreline secondaries is that one mount can contribute to fire on either beam. Since you generally plan on fighting such a ship on the broadside, you'd almost certainly use them to reduce the number of mounts carried.

 

[BlackBat242]

In that drawing I don't see the secondary (aft) main battery rangefinder/control location, nor the fore & aft centerline directors for the 5" battery (all of the USN's new battleships had 4, 1 on each beam, 1 each fore & aft on the centerline).

Those require the space you devote to the centerline 5" mounts.

 

[Scott Kenny]

In that drawing I don't see the secondary (aft) main battery rangefinder/control location, nor the fore & aft centerline directors for the 5" battery (all of the USN's new battleships had 4, 1 on each beam, 1 each fore & aft on the centerline).

Those require the space you devote to the centerline 5" mounts.

While true, I don't think I see any fire directors in the sketch.

 

[BlackBat242]

While true, I don't think I see any fire directors in the sketch.

It kinda looks like one atop the tower structure, which is where the USN battleships put the primary main battery director.

 

[DE1083]

I believe there was a proposal from Adm Halsey for the Kentucky and subsequent ships to have a twin 5" mount on the center line fore & aft, with the remaining mounts port & starboard

 

[Ainen]

I believe there was a proposal from Adm Halsey for the Kentucky and subsequent ships to have a twin 5" mount on the center line fore & aft, with the remaining mounts port & starboard

It was for tactical reasons, i believe - i.e. the ability to continuously engage targets crossing course of the vessel.
It's a way to solve one of the most common ways to throw off effective AA fire control of a WW2 ship.

 

[Scott Kenny]

It was for tactical reasons, i believe - i.e. the ability to continuously engage targets crossing course of the vessel.
It's a way to solve one of the most common ways to throw off effective AA fire control of a WW2 ship.

And since the fast battleships were spending more time as carrier escorts than as shore bombardment or fighting other battleships, they'd likely see many targets doing that on their way to the carrier(s).

 

[Ainen]

And since the fast battleships were spending more time as carrier escorts than as shore bombardment or fighting other battleships, they'd likely see many targets doing that on their way to the carrier(s).

Fundamentally (technically), yes.

To be fair, escorting carriers wasn't seen as their specific job. It was done in 1942, as an act of desperation.

Battleship, despite its reputation, wasn't really the best escort. Thee amount of its firepower was more than offset by the fact that a unit far away in outer AA screen (covering no more area than a DD) was more expensive to procure and operate compared to fleet carriers themselves. Doing little with 90% of their own firepower at that.

It was just a very obvious missuse of assets, and US fleet in 1944 was continuously giving more and more independence to its fast BB TFs, to let them deal actual damage.

US carrier screens by 1945 were already receiving their own dedicated heavy escorts, i.e. Alaska class CBs - still expensive as f...the carriers themselves (legacy of their mission to stop equivalent IJN units - which was also needed for carrier screens, just not by 1945), but capable of perfectly matching carrier maneuvers. And those, like all other modern cruisers, already had their centerline secondary turrets.

And for BB it was mostly for their own protection, esp. in Kamikaze context: better trained Kamikaze pilots often did this or other well-calculated, sharp maneuvers right before their terminal dive - and very often succeeded.
Even modern subsonic ASCMs on rwr warning are programmed to do the same.

 

[BlackBat242]

 

[Scott Kenny]

View attachment 706276

Yes, that's what I'm talking about! Looks like 4x 5" turrets on the sides and then the fore and aft 5" turrets. Along with a very SoDak like superstructure.

 

[Scott Kenny]

Fundamentally (technically), yes.

To be fair, escorting carriers wasn't seen as their specific job. It was done in 1942, as an act of desperation.

Battleship, despite its reputation, wasn't really the best escort. Thee amount of its firepower was more than offset by the fact that a unit far away in outer AA screen (covering no more area than a DD) was more expensive to procure and operate compared to fleet carriers themselves. Doing little with 90% of their own firepower at that.

It was just a very obvious missuse of assets, and US fleet in 1944 was continuously giving more and more independence to its fast BB TFs, to let them deal actual damage.

US carrier screens by 1945 were already receiving their own dedicated heavy escorts, i.e. Alaska class CBs - still expensive as f...the carriers themselves (legacy of their mission to stop equivalent IJN units - which was also needed for carrier screens, just not by 1945), but capable of perfectly matching carrier maneuvers. And those, like all other modern cruisers, already had their centerline secondary turrets.

Only 2x CBs built, and they took almost as many crew as an Iowa to operate while only giving the AA protection of a Baltimore class CA.

 

[Ainen]

Only 2x CBs built, and they took almost as many crew as an Iowa to operate while only giving the AA protection of a Baltimore class CA.

(1)Two were built for the same reason as four Iowas (only two in time to matter). War ended, too late, IJN failed to survive beyond 1944 in fighting shape (to be exact, it survived, but with Philippines again in American hands it didn't matter). The last point wasn't obvious till early 1945, however, and evolution of US battle plans continued.

(2)Iowas (and other FBBs) weren't operating as carrier escorts in great battles of 1944, and were progressively more independent.
A bit of a shame FBBs got full independence only after Leyte, but Leyte was perhaps a necessary step to show why battle force shouldn't become subordinated to light forces.
That meant, BBs weren't and shouldn't be expected to be with carriers.

(3)Main difference between DD, CL/CA and CB/BB in AA escort role ultimately goes not to the number of guns or even fire control, but to platform stability. Numbers matter more for platform defending itself.

Alaska was giving that highly stable platform with ~same maneuvering specs and habits as Essex, and thus could consistently keep up with any fleet carrier doing it annoying flight ops maneuvering. Battleship couldn't.
12" battery also ensured that TF had a ready answer to delay any fast surface threat (Haruna was technically still operational).

In 1945 we can see a lot of that, they work specifically with carrier TFs or in their interest.
BBs at this point are their own thing.

 

[Colonial-Marine]

I don't know why the configuration was rejected during the development of the South Dakota class but it may have been due to how hard they were working to keep the design within treaty tonnage limitations. During the war it seems that the USN determined it wanted a pair of centerline secondary gun mounts as shown by the King/Nimitz redesign proposed for Illinois and Kentucky. I wonder if any of the battleships of the Montana class would see the same modification of their design had it been decided to go ahead with the construction of them?

 

[BlackBat242]

Alaska was giving that highly stable platform with ~same maneuvering specs and habits as Essex, and thus could consistently keep up with any fleet carrier doing it annoying flight ops maneuvering. Battleship couldn't.

The only reason (some) fast battleships couldn't "keep up" was that the North Carolinas & South Dakotas were only fairly fast (~27 knots compared to the carriers' 33 knots) - but the 4 Iowas made 33 knots.


The Alaskas, with their single rudder, were notoriously poor-maneuvering ships, with a turning radius at speed much larger than that of either the Iowas or the slower 6 fast battleships {edit: or the Essex class}.

According to the various volumes of Friedman's:

Alaska had a tactical diameter of 915 yds @ 30 kts
North Carolina: (model tests)- 759 yds @ 27.5 kts; (trials performance)- 683 yds @ 27.5 kts
South Dakota: (model tests)- 733 yds @ 26.5 kts
Iowa: (model tests)- 1430 @ 33 kts; (trials performance)- 814 yds @ 30 kts

Carriers:
Lexington: (model tests)- 1950 yds @ 33 kts (the worst of any US warship of WW2)
Yorktown: (trials performance)- 790 yds @ 30 kts
Essex: (trials performance)- 765 yds @ 30 kts
Casablanca CVE: (trials performance)- 450 yds @ 15 kts

Alaska had faster loss of speed in a hard turn as well.

https://www.alternatehistory.com/fo...best-for-80s-reactivation.171057/post-3775232

 

[Ainen]

The only reason (some) fast battleships couldn't "keep up" was that the North Carolinas & South Dakotas were only fairly fast (~27 knots compared to the carriers' 33 knots) - but the 4 Iowas made 33 knots.


The Alaskas, with their single rudder, were notoriously poor-maneuvering ships, with a turning radius at speed much larger than that of either the Iowas or the slower 6 fast battleships {edit: or the Essex class}.

According to the various volumes of Friedman's:

Alaska had a tactical diameter of 915 yds @ 30 kts
North Carolina: (model tests)- 759 yds @ 27.5 kts; (trials performance)- 683 yds @ 27.5 kts
South Dakota: (model tests)- 733 yds @ 26.5 kts
Iowa: (model tests)- 1430 @ 33 kts; (trials performance)- 814 yds @ 30 kts

Carriers:
Lexington: (model tests)- 1950 yds @ 33 kts (the worst of any US warship of WW2)
Yorktown: (trials performance)- 790 yds @ 30 kts
Essex: (trials performance)- 765 yds @ 30 kts
Casablanca CVE: (trials performance)- 450 yds @ 15 kts

Alaska had faster loss of speed in a hard turn as well.

https://www.alternatehistory.com/fo...best-for-80s-reactivation.171057/post-3775232

Thanks!

Though from what I understand, it's simply about similar powerplant and weight class (i.e. inertia and responsiveness to the rudder, not the same maneuvering specs per se). Many fast WW2 ships (esp. destroyers!) were notoriously bad at maneuvering for various reasons, until the situation was too outrageous, they still did common steaming and maneuvering within screen just fine.

It was just one of the things skippers needed to get right when forming a unit together.

 

[Scott Kenny]

I don't know why the configuration was rejected during the development of the South Dakota class but it may have been due to how hard they were working to keep the design within treaty tonnage limitations. During the war it seems that the USN determined it wanted a pair of centerline secondary gun mounts as shown by the King/Nimitz redesign proposed for Illinois and Kentucky. I wonder if any of the battleships of the Montana class would see the same modification of their design had it been decided to go ahead with the construction of them?

Maybe? I think it would have also required a more compact superstructure, like the SoDaks. Montanas already had an armored citadel that was a good 100ft longer than the Iowas, they don't need to make that any longer!

 

[MadRat]

I would think the fire control layout dictated AA placement.

 

[1635yankee]

Thanks!

Though from what I understand, it's simply about similar powerplant and weight class (i.e. inertia and responsiveness to the rudder, not the same maneuvering specs per se). Many fast WW2 ships (esp. destroyers!) were notoriously bad at maneuvering for various reasons, until the situation was too outrageous, they still did common steaming and maneuvering within screen just fine.

It was just one of the things skippers needed to get right when forming a unit together.

I suspect that part of the reason for the relatively large turning circles of the Alaskas (and the Atlantas and the Lexington and Saratoga) was because they were designed under USN cruiser design rules, which preferred single rudders.

Any ship design has a large number of compromises to reach fruition (avoiding compromise leads to ships that can't be afforded); the USN chose to sacrifice some level of maneuverability in cruisers and destroyers for characteristics they felt more important.

 

[1635yankee]

Remembering that none of my hats include "naval architect," putting centerline 5"/38 mounts super-firing the main-battery 16" turrets would have quite a few side effects: increased citadel length, increased height for the bridge, relocated AA fire control, yadda, yadda, yadda. In all, this makes me think that putting centerline 5"/38 onto Kentucky would require signficant redesign, and could not be done in anything resembling a "timely manner."

As for the Alaskas? These were ships that were, reportedly, built in response to a Japanese super-cruiser that was only rumored to be planned. Once built, the problem was finding something they were even vaguely useful for. Their lack of utility is pretty solidly proven by how long they stayed in service post-WW2. Overall, the USN would have been much better off devoting that amount of steel, yard space, and labor to more landing craft.

 

[apparition13]

Re. the King-Nimitz plan for Illinois and Kentucky, the same as Oregon City vs. Baltimore or Fargo vs. Cleveland - trunk the funnels to one to gain the centerline clearance to move two of the dual purpose mounts to the centerline.

 

[BlackBat242]

Re. the King-Nimitz plan for Illinois and Kentucky, the same as Oregon City vs. Baltimore or Fargo vs. Cleveland - trunk the funnels to one to gain the centerline clearance to move two of the dual purpose mounts to the centerline.

Both the Baltimore class and its single-funnel variant the Oregon City class had two twin 5"/38 mounts on centerline and two more on each beam. There was no change in the 5"/38 layout, only in that of the 40mm and 20mm guns.

The same was true for the Cleveland class and its single-funnel variant the Fargo class - no change in 5"/38 locations/numbers (except for the Fargos lowering the beam 5"/38 mounts to the main deck, rather than elevated a deck as in both heavy cruiser classes and the Clevelands).

The King-Nimitz plan for the "modified Iowa class" battleships would have moved two twin 5"/38 mounts from the beam (one port & one starboard) to centerline, leaving four mounts on each beam.

The goal, however, would be the same as in the cruisers - to reduce the side area vulnerable to shellfire and to improve the arcs of fire for the AA battery - its just that the improvement in the arcs for the 40mm and 20mm (or possibly 3"/50) guns would ALSO see improvement for the 5"/38 guns due to the relocation.