Info on Omaha-class cruiser modernizations

[YourChair]

I read in Friedman's US cruisers book that it was proposed to modernize the Omahas by replacing their guns with 152mm/47s, among other things.

Also, I found from another source a proposal to convert the class to AA cruisers:
"In 1940, a project was developed to convert Omaha-class cruisers into air defense cruisers. It was planned to change the armament of the ships to two twin 152-mm gun mounts, seven single-gun 127-mm gun mounts and six quadruple 28-mm machine guns. However, the stability of ships with such a composition of weapons was a matter of concern and the modernization was rejected."

Does anyone have more information about these and other modernizations?

 

[Tzoli]

There were actually 3 CLAA conversion schemes in 1939/40:
Scheme 1: 2x2 6"/53, 7x1 5"/25, 6x4 28mm/75
Scheme 1: 2x2 6"/53, 8x1 5"/25, 7x4 28mm/75
Scheme 1: 2x2 6"/53, 9x1 5"/25, 4x4 28mm/75

There was also a proposal to convert two of them in 1920 into sort of light carriers similar to the USS Langley but with 3 single 6"/53 guns retained and a capacity to carry 40 aircraft.

 

[PMN1]

There were actually 3 CLAA conversion schemes in 1939/40:
Scheme 1: 2x2 6"/53, 7x1 5"/25, 6x4 28mm/75
Scheme 1: 2x2 6"/53, 8x1 5"/25, 7x4 28mm/75
Scheme 1: 2x2 6"/53, 9x1 5"/25, 4x4 28mm/75

There was also a proposal to convert two of them in 1920 into sort of light carriers similar to the USS Langley but with 3 single 6"/53 guns retained and a capacity to carry 40 aircraft.

Any more on the carrier conversions?

 

[Tzoli]

Not much a deck would be constructed with overall hull length, no island. The late CanisD made a drawing once:

 

[ptdockyard]

I started the CVL conversion in 1/1200 and thought is was not real as the flight deck would be really narrow. An air group of 40 planes seems high but I have not seen any documentation aside from CanisD's drawing.

Did all of the AA conversions also involve reducing the stacks from four to two, as in the drawing in Friedman's Cruiser book?

Dave

 

[BlackBat242]

Here is the 7 June 1940 Omaha AA conversion scheme from Friedman:




In this conversion, all except the turret mounted fore and aft 6" guns would have been removed. The two center stacks would have been removed, this area becoming an amidships gun deck, with the draft from these fire rooms vented into two larger stacks located at the original fore and aft stack location. In the drawing the catapults and aircraft handling cranes were also retained. The ships would have received seven 5"/25 single mounts and eight 1.1"/75 machine cannon mounts. There is a drawing of this configuration dated June 7, 1940 in Friedman's U.S. Cruisers book (page 83)[see above].

With their speed they would have made good task force escorts, but would have been a bit short-legged (4,920 miles @ 20 knots versus 5,630 miles @ 20 knots for the modern Atlanta class) at task force operational speeds. I would assume that 40mm Bofors would have replaced the 1.1"/75's. With these additions and more modern directors they would have made adequate AA escorts.


I made a modernized Omaha scheme a decade ago... here are the original and each of my two variants - note the increase in size of the AA guns.

While I did not note calibers on the drawing, the 6" guns could be simply the existing 6"/53s (with 4 moved from casemates to new turrets) or all-new 6"/47 guns in the same low-angle design turrets).

Likewise, the hull could be widened a couple of feet on each side to preserve stability, at the cost of a knot or two:

 

[M. A. Rozon]

I made a modernized Omaha scheme a decade ago... here are the original and each of my two variants - note the increase in size of the AA guns.

While I did not note calibers on the drawing, the 6" guns could be simply the existing 6"/53s (with 4 moved from casemates to new turrets) or all-new 6"/47 guns in the same low-angle design turrets).

Likewise, the hull could be widened a couple of feet on each side to preserve stability, at the cost of a knot or two:

View attachment 691073

Were these 1941 arrangements based on other information (if so then what source(s), please?) or were they generated in their entirety by you? I like the arrangement and they would make for a good small light cruiser that makes far more efficient use of the ship's displacement.

 

[Dilandu]

I made a modernized Omaha scheme a decade ago... here are the original and each of my two variants - note the increase in size of the AA guns.

While I did not note calibers on the drawing, the 6" guns could be simply the existing 6"/53s (with 4 moved from casemates to new turrets) or all-new 6"/47 guns in the same low-angle design turrets).

Likewise, the hull could be widened a couple of feet on each side to preserve stability, at the cost of a knot or two:

I'm concerned about upper weight of superfiring turrets. Each of them add 52+ metric tons, not counting the barbettes. While removal of four casemate mounts from each end theoretically free 77.6 tons, the superfiring turrets are placed on the level of upper casemates. Which means that upper weight increased significantly. I'm not sure 25+ tons of summary weight reduction per turret would be enough.

P.S. Maybe the more optimal idea would be to limit ship to just three turrets, placing the third on the rear (and retaining the lower pair of forward casemates). In that case the upper weight increase would be tolerable, and you would have 7 guns per broadside (just one less than with four turrets).

 

[BlackBat242]

I made a modernized Omaha scheme a decade ago... here are the original and each of my two variants - note the increase in size of the AA guns.

While I did not note calibers on the drawing, the 6" guns could be simply the existing 6"/53s (with 4 moved from casemates to new turrets) or all-new 6"/47 guns in the same low-angle design turrets).

Likewise, the hull could be widened a couple of feet on each side to preserve stability, at the cost of a knot or two:

View attachment 691073

Were these 1941 arrangements based on other information (if so then what source(s), please?) or were they generated in their entirety by you? I like the arrangement and they would make for a good small light cruiser that makes far more efficient use of the ship's displacement.

Yes, they were purely my own creation.

I made a modernized Omaha scheme a decade ago... here are the original and each of my two variants - note the increase in size of the AA guns.

While I did not note calibers on the drawing, the 6" guns could be simply the existing 6"/53s (with 4 moved from casemates to new turrets) or all-new 6"/47 guns in the same low-angle design turrets).

Likewise, the hull could be widened a couple of feet on each side to preserve stability, at the cost of a knot or two:

I'm concerned about upper weight of superfiring turrets. Each of them add 52+ metric tons, not counting the barbettes. While removal of four casemate mounts from each end theoretically free 77.6 tons, the superfiring turrets are placed on the level of upper casemates. Which means that upper weight increased significantly. I'm not sure 25+ tons of summary weight reduction per turret would be enough.

P.S. Maybe the more optimal idea would be to limit ship to just three turrets, placing the third on the rear (and retaining the lower pair of forward casemates). In that case the upper weight increase would be tolerable, and you would have 7 guns per broadside (just one less than with four turrets).

While I had not considered the possibility when I made them (my design-creation was still at a "baby" stage), that very stability issue is why I suggested a possible slight bulging, even at the cost of a couple of knots speed. However, note that more than just the casemate guns would be removed to make room for the superfiring turrets.

One thing I learned looking at photos of the actual ships is that some had only 3 aft "casemate" guns, with one of them even higher... see the below:

USS Cincinnati CL-6 (note the removal of the upper two aft casemate 6: guns in favor of a lot of light AA and an enlarged deckhouse amidships):






Compared to USS Marblehead CL-12:






USS Trenton CL-11 1930 (note the large block structure housing the fore casemate guns):




USS Detroit CL-8 Dec 1928 (note how wide the block for the casemate guns is, nearly all would be cut away):

 

[Dilandu]

Compared to USS Marblehead CL-12:

She have an unique refit - her upper two casemates were replaced with "semi-turret" (i.e. circular gun shield) in superfiring position. The idea was to save upper weight, by allowing a single gun to do the job of two. As far as I know, the refit was considered sucsessfull, but not further implemented due to not improving their stability as much as engineers hoped.

 

[johnpjones1775]

hello, just stumbled across this discussion and as i had some ideas about the omaha class, and went a googling to see if they were considered before.

so, my idea for an omaha modernization, would be cut away the casemates, leave them open as gun tubs for 40mm guns twin mounts, quads if they'd fit.
replace the 6" guns with twin 5" DP mounts
and i'm not sure how many guns could be fitted on the main deck of either 3" or 5" in size, but looking at some of the historical proposals it seems at least three 5" guns could be fitted either side. removing the middle stacks could also open up room for a few more light/medium AA guns.

there are also pictures of omaha with platforms and spotlights around the two aft smoke stacks, so potentially you could add a platform around the two remaining stacks, where you could mount twin 20s as well.

 

[Dilandu]

so, my idea for an omaha modernization, would be cut away the casemates, leave them open as gun tubs for 40mm guns twin mounts, quads if they'd fit.
replace the 6" guns with twin 5" DP mounts

You would get basically a 2/3 capabiliies of Gearing-class destroyer for much higher service cost. Not sure it would be practical.

 

[johnpjones1775]

so, my idea for an omaha modernization, would be cut away the casemates, leave them open as gun tubs for 40mm guns twin mounts, quads if they'd fit.
replace the 6" guns with twin 5" DP mounts

You would get basically a 2/3 capabiliies of Gearing-class destroyer for much higher service cost. Not sure it would be practical.

If you put 3 pedestal mounted 5” DP guns per side, in terms of overall fire power you’re getting an extra 33% more fire power than a gearing.

Removing the two center stacks you could likely fit a few more guns, I’d go with 3” for more AAA.

 

[drwells42]

so, my idea for an omaha modernization, would be cut away the casemates, leave them open as gun tubs for 40mm guns twin mounts, quads if they'd fit.
replace the 6" guns with twin 5" DP mounts
and i'm not sure how many guns could be fitted on the main deck of either 3" or 5" in size, but looking at some of the historical proposals it seems at least three 5" guns could be fitted either side. removing the middle stacks could also open up room for a few more light/medium AA guns.

I had discussed something comparable to this with a friend once. Replace the 6" twins with 5"/L38 mk 32, (small weight savings) and then put as many open mount Mk 30s and 40mm as you can on the sides. Trunk the funnels as shown in Friedman.

The Brits did something comparable with HMS Delhi, (4 single Mk 30 in closed mounts) and they seemed to like it. The armament may have been comparable to a destroyer, but they still had the cruiser's cruising range.

 

[drwells42]

The Brits did something comparable with HMS Delhi, (4 single Mk 30 in closed mounts) and they seemed to like it. The armament may have been comparable to a destroyer, but they still had the cruiser's cruising range.

A bit of bad wording on my part. It was of course a US refit of a British ship.

 

[johnpjones1775]

so, my idea for an omaha modernization, would be cut away the casemates, leave them open as gun tubs for 40mm guns twin mounts, quads if they'd fit.
replace the 6" guns with twin 5" DP mounts
and i'm not sure how many guns could be fitted on the main deck of either 3" or 5" in size, but looking at some of the historical proposals it seems at least three 5" guns could be fitted either side. removing the middle stacks could also open up room for a few more light/medium AA guns.

I had discussed something comparable to this with a friend once. Replace the 6" twins with 5"/L38 mk 32, (small weight savings) and then put as many open mount Mk 30s and 40mm as you can on the sides. Trunk the funnels as shown in Friedman.

The Brits did something comparable with HMS Delhi, (4 single Mk 30 in closed mounts) and they seemed to like it. The armament may have been comparable to a destroyer, but they still had the cruiser's cruising range.

i just think in general any refit that leaves the 6" turrets on the ship will end up leaving the ship with no real role. give some DP turrets, and some DP guns along each side it can at least act like a large air defense DD at the very least

 

[EwenS]

The Brits did something comparable with HMS Delhi, (4 single Mk 30 in closed mounts) and they seemed to like it. The armament may have been comparable to a destroyer, but they still had the cruiser's cruising range.

A bit of bad wording on my part. It was of course a US refit of a British ship.

It was 5x5”/38 that we’re fitted to Delhi (originally earmarked for the destroyer USS Edison) along with 2xMark 37 directors. The deal was that if British tests of the system worked out, a second conversion was intended to follow during 1942. But then Pearl Harbor changed everything and the US needed every weapon it could get so the second conversion never happened (can’t remember offhand which vessel was earmarked).

 

[Yellow Palace]

It was 5x5”/38 that we’re fitted to Delhi (originally earmarked for the destroyer USS Edison) along with 2xMark 37 directors. The deal was that if British tests of the system worked out, a second conversion was intended to follow during 1942. But then Pearl Harbor changed everything and the US needed every weapon it could get so the second conversion never happened (can’t remember offhand which vessel was earmarked).

DUNEDIN was to have been the second conversion, approved in July 1941, but it was contingent on successful trials with DELHI. Since the former had a date with two German torpedoes in November 1941, and the latter didn't complete its refit until December 1941, plans would probably have changed even without the US entering the war.

 

[1Big Rich]

It was 5x5”/38 that we’re fitted to Delhi (originally earmarked for the destroyer USS Edison) along with 2xMark 37 directors. The deal was that if British tests of the system worked out, a second conversion was intended to follow during 1942. But then Pearl Harbor changed everything and the US needed every weapon it could get so the second conversion never happened (can’t remember offhand which vessel was earmarked).

View attachment 700986

That is a great profile pic of Delhi after her modernization. Thanks for sharing that, Ewen!

Regards,

 

[BlackBat242]

Enlarged Fletcher class...