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AU, USA, Omaha Class Light Cruiser 1926
http://67.205.157.234/forums/viewtopic.php?f=15&t=7053		 Page 1 of 3
Author:  Krakatoa [ June 30th, 2016, 3:28 am ]
Post subject:  AU, USA, Omaha Class Light Cruiser 1926
I have been watching the other threads on US cruiser designs and decided I would have a try as well. Put my lines where my mouth is.

At the end of World War One the US Navy had only the 3 Chester class that could be classed as light cruisers, and the 'Big Ten' armoured cruisers. Both sets of cruisers were obsolete and only good for reduced service. This left a big hole in the US order of battle that needed to be filled soonest. One of the armaments designed for the new large battleships stopped by the Washington Treaty was a new triple 6". This weapon was also chosen for the new cruiser design. A hull of 590 feet long and 58 foot wide would be able to contain both four of the new triple turrets and 80,000shp oil fired propulsion system. A speed of 33 knots was to be able to be sustained for 1500 miles. An overall range of 7500 miles at 14 knots was specified. The new 5"/25cal AA guns were fitted as the secondary armament. 0.5"/50cal machine guns were fitted for use against small craft and aircraft.

Eventually twelve of these ships were laid down in groups of 4 in 1923-24-25 and were completed 1926-28. All twelve easily made over 33 knots on trials and even 15 years later with war additions could still make 31/32 knots. One of their main uses during the peacetime period was as Flotilla Leaders to the destroyer squadrons.

[ img ]


Displacement: 7,750 tons standard, 9,300 full load
Dimensions: 590 x 58 x 24
Machinery: Oil fired, geared turbines, 80,000shp, 4 shafts.
Speed: 33 knots
Endurance: 7,500 miles @ 14 knots
Armour: 2" side, 2" deck. 2" turrets.
Armament:
12 x 6" (4x3)
6 x 5" (6x1)
9 x 0.5" mg (9x1)
6 x 21" torpedoes (2x3)
Aircraft: 1
Crew: 585
Author:  bezobrazov [ June 30th, 2016, 8:15 am ]
Post subject:  Re: AU, USA, Omaha Class Light Cruiser 1926
Hmmm...a nice attempt, but there are a few issues: the bow form wasn't adopted till mid-1930s, the bulbous bow would not have been adopted. The double-storied FCS and spotting top is too much (too heavy) and too low. Also, six 5/25, when the standard for the heavy cruisers were only four? Not very plausible, I'm afraid. And, you don't seem to have understood the function and, most importantly the actual appearance of the uniquely USN flutes along the aft floatplane. You persist in pretending to have them, which results in a wholly implausible configuration, instead of actually studying, for instance the Northampton-class, which, I can assure you, have them featured the correct way. Boat stowage would have been concentrated aft; if you carefully study virtually all USN cruiser designs up until the lapse of the London Treaty, you'll discover that that's a common feature, so, why not here then? Finally, one thing I advised TristanAlting about: the scuttles need to be far, far more numerous and be continued all the way to the bows! Your ship also lacks a main gunnery director atop the pilothouse, which would have been a normal feature, even with 6"-guns.
Author:  eltf177 [ June 30th, 2016, 10:17 am ]
Post subject:  Re: AU, USA, Omaha Class Light Cruiser 1926
I like her.
Author:  Krakatoa [ June 30th, 2016, 12:25 pm ]
Post subject:  Re: AU, USA, Omaha Class Light Cruiser 1926
Thank you Elf177, I like it too.

Sorry Ari but I do not agree with a lot of your advice. The boats are fine where they are. The US cruisers had their boats aft because the centre section was the aircraft handling area. Take out the aircraft and the boats would have been centred. So if you carefully scrutinise those US cruiser photos all of them will have the aircraft handling facilities centrally located, so the boats have to be aft. I do agree with the bow and I have changed them both for the CL above and CA below. I have added extra gunnery and torpedo directors fore and aft. Secondary armament at six guns is fine. If the US was silly enough to only have four, more fool them. It did not take them long to increase four to eight. I actually keep torpedoes on both the CL and CA which US doctrine did not like on their CA's. Another mistake by the US. Those US cruisers that had the extra tall mast complexes also suffered from excessive topweight. So I kept my foretops a bit lower than the US norm.

Geez you do go on. "And, you don't seem to have understood the function and, most importantly the actual appearance of the uniquely USN flutes along the aft floatplane. You persist in pretending to have them, which results in a wholly implausible configuration, instead of actually studying, for instance the Northampton-class, which, I can assure you, have them featured the correct way." I looked up the ship that I cut'n'pasted the aircraft from and there is no comment from you that this section is wrong? How can I persist in using something that is the first time I have ever used it? Bit of a double standard? You do keep on about your three Northampton class drawings which I am sorry to say I do not like. There is too much so called 'detail' that half of the drawing aft is almost impossible to tell what is what. One of those times when too much detail really is far too much. I would suggest they are in need of a redraw, maybe have a look at how Garlicdesign, Maomatic, BB1987 and others achieve lots of detail without compromising the look of the drawing.

Unfortunately Ari, you get too hung up on everything in the AU/PD sections, where US ships are being drawn, in trying to make them conform exactly to US standards. That is no good to anybody drawing US ships in the PD/AU sections. 'We' doing those drawings, are more interested in creating 'alternative' drawings that look like US ships than directly conforming to US doctrine. If we can get 80% right then close your eyes to the other 20% as PD/AU drawing license.

Pensacola Class Heavy Cruisers.

Having made the Omaha Class a decent size at 590x58 I can also use them as the basis for the first heavy cruiser class. The real Pensacola's were 585x65 but the extra breadth was needed for the triple turrets where my lot are four twins. The armour increases to a 4" belt armour, deck armour remains the same.

[ img ]

The extra armour and heavier building to take the 8" turrets reduced the speed from 33 to 32 knots.
Author:  bezobrazov [ June 30th, 2016, 1:23 pm ]
Post subject:  Re: AU, USA, Omaha Class Light Cruiser 1926
Whatever...
Author:  Colosseum [ June 30th, 2016, 2:44 pm ]
Post subject:  Re: AU, USA, Omaha Class Light Cruiser 1926
Seems to be impossible to have a thread about US cruisers here anymore. :shock:

Part of making a realistic PD/AU design is introducing flaws (like the many "mistakes" you've called out re: prewar USN practice). To me these make the designs more believable.

An interesting personal design USN cruiser to me would follow the basic design practices of the period (including the flaws) but introducing a new "shape" to the ship itself. I'm not very good at this myself as I tend to only draw real designs as I don't consider myself a ship designer but rather a ship drawer. But that's just me!

It would be interesting to show this cruiser in several different "year" iterations. If it were up to me I'd draw these:

1. 1929, as built.

2. 1935: a few light AA guns added, painted in pre-war light grey with large hull numbers.

3. December 7th, 1941: more light AA, Measure 1 dark grey scheme with light grey above the funnel tops, CXAM radar above the foremast. Bathtub of .50-cals above the mainmast.

4. Maybe a drawing of a sister ship stationed with the Asiatic Fleet painted in Cavite Blue with a slightly-similar fit?

5. A drawing of that same sister ship as sunk at Sunda Strait along with HMAS Perth and USS Houston, weathered Cavite Blue and maybe a Measure 5 false bow wave?

6. CA-1929's original unit in 1942, with a lot more light AA (mostly 1.1" quads and .50-cals) and a single SG surface search above the pilot house. Likely painted in Measure 21 (overall 5-N Navy Blue).

7. CA-1929 original unit in 1943, with 40mm Bofors quads replacing the 1.1" and 20mm Oerlikons starting to replace the .50cals. A revamped foremast with an SK air search radar and the SG surface search set relocated to the mainmast. Probably painted in one of the cruiser Measure 32 schemes.

8. CA-1929 in 1944, with the standard mid-to-late-war radar fit of SK/SG on the foremast and SG on the mainmast. Maybe a few Mk.57 radar-assisted directors above the pilot house. The basic SPT-1 ECM suite on the yards, with a few of the early corner reflector TDY jammers on the front of the foremast and aft of the mainmast. Probably painted in Measure 22 (graded system) as the ship becomes basically a shore bombardment vessel and carrier escort.

9. CA-1929 in 1945, with the SK upgraded to an SK-2, and maybe an enlarged mainmast with an SP or SM height finder. Late-war TDY trainable jammer assembly on the aft funnel, with associated monitoring antennas ahead of the pilothouse. TDY-1A S-band jammers in radomes along the deck edge and a receiving antenna on the mainmast. Even more light AA. Maybe it's painted in the later Measure 22 graded system based on the grey instead of blue paint tint.

Kind of makes me want to design a few cruisers!
Author:  erik_t [ June 30th, 2016, 3:39 pm ]
Post subject:  Re: AU, USA, Omaha Class Light Cruiser 1926
I think the appearance, growth, and then minimalization of USN cruiser hangars from the 20s to the 40s reflects a growing appreciation of the importance of aircraft, and then of their increasing maturity and durability. A Pensacola didn't maybe care about her aircraft being beaten by the weather, because nobody appreciated how much aircraft mattered. In any case, they were midships were maintenance would be reasonably easy. Northamptons demonstrated a much greater commitment to the ship impact of a major aircraft fit, with a large hangar amidships that would protect the relatively fragile aircraft of the day, or at least protect spare parts and spare airframes. By the 1940s, aircraft were faster, more heavily built, and simply better-engineered, and so while a hangar was still desirable, they did not mandate such a large ship impact.

My $0.02 as an airplane guy.

They're attractive drawings, to be sure. I would note that USN doctrine eliminated torpedoes from cruisers almost entirely (only the Atlanta super-leaders had them, IIRC). I think this was a self-protection decision, justified to some degree by the damage some Japanese cruisers suffered from exploding torpedo fits.

I think the 6" turrets look a little too modern for a ship of this era. I'd expect them to look more like downsized Pensacola turrets, particularly without such aggressive turret face armor slope.
Author:  Colosseum [ June 30th, 2016, 3:51 pm ]
Post subject:  Re: AU, USA, Omaha Class Light Cruiser 1926
That's a good point - also good to note that the later cruiser designs (Cleveland, Baltimore, Fargo, Oregon City, etc) all did have hangars at their stern, but the BBs did not (I think this was because of the large quarterdecks of the BBs which meant the planes wouldn't be exposed to nearly as much damaging wave action, etc).

As for the lack of torpedoes being "another mistake by the USN", well you can say whatever you want, but as erik_t says this was likely based both on the unreliable early torpedoes as well as the explosive danger posed by same. Torpedo attacks are the domain of the destroyer, not the heavy cruiser (whose guns and aircraft are its weapons) - this was the USN doctrine of the time and your design won't make sense given design practice of the time if you attempt to keep torpedoes on the big cruisers after 1940.
Author:  erik_t [ June 30th, 2016, 4:02 pm ]
Post subject:  Re: AU, USA, Omaha Class Light Cruiser 1926
Not only are they an explosive danger, but they force different tactical maneuvering and task group disposition. In general, you cannot simultaneously maneuver ownship for maximum gunnery effect and move into position for a torpedo attack. Note that a DD of the era would not really worry about 5/38 gunlaying against a target worthy of a torpedo spread. It was all or nothing one way or the other.

Certainly had a couple of USN CA's been snookered into a bad position by a Japanese BB, they'd want to have torpedoes aboard. It's a question of, on limited displacement, do you want to maximize your one capability or handicap it somewhat for an off-design usage? The USN had the luxury of 5:5:3 tonnage and so considered cruisers to be fleet scouts and raider-hunters first, second, and third. They never envisioned them attacking units immune to 6/47 or 8/55; if they encountered them, run away and let the job be handled by ships optimized for the task.

I think it's totally fair to question USN doctrine on this point, but to outright call it a definite mistake is an oversimplification.
Author:  Karle94 [ June 30th, 2016, 5:02 pm ]
Post subject:  Re: AU, USA, Omaha Class Light Cruiser 1926
Some of the early design iterations of the Pensacolas had a hangar on the stern, with a triple turret above, slightly behind. The design was changed to have 10 8 inch guns to make them more capable of defending themselves when attacked. They were fleet scouts (light cruiser), after all, not ships of the line. The Pensacola class with its triple turrets on top, and twin at the bottom, combined with the flush deck design made them quite top heavy, making the removal of the hangar a neccessity.

Krakatoa, Bezo is not referring to the planes, but rather the aft section of the underwater hull. I made the mistake of shading it like a normal hull, whereas the American cruisers, and even BBs, had a quiet steep angle on the hull.

This is what he means: https://www.dropbox.com/s/aqi49f7rjamd9 ... 8.png?dl=0
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