Shipbucket

In 1939 Rome laid down a new breed of heavy cruisers; The Kronus class. A total of 10 ships would be built in the next 4 years. Unlike all the previous cruisers, the Kronus was a completely new design from the keel up. Almost nothing was based on previous cruiser classes. The Kronus ended up being much larger, both in terms of physical size, and weight than the other cruisers. Only the Venus class battlecruisers was bigger and heavier than the Kronus. Designed around the new design of quick firing 8 inch guns that under controlled circumstances fired at least 1/3 faster than the older guns. She was also provided with a solid secondary battery of 12 5 inch DP guns in 6 turrets. Her initial AA battery consisted of 28x40mm and 36x20mm AA guns. Unlike most of the earlier heavy cruiser classes, the Kronus was completed with two quad 21 inch torpedo launchers mounted amidships. Though fitted for, the Kronus never shipped seaplanes as radars were advanced and reliable enough for ships to do without sea planes.

The ships had a displacement of 15,706 tons standard. The armor was a 6 inch armor belt, 3 inch deck armor and 8 inch armor on the conning tower. Top speed was 30, although speed of up to 32 were possible, but not for a very long time as damage to the boilers was of serious concern, speed around 31+ knots also brought on excessive vibrations that was not just unpleasent, but could also do damage to very sensitive equiplments on board. The ships were regarded as very good seaboats, able to go fast and still keep shooting where other, much larger ships could not.



RRS Kronus, Republic of Rome, Heavy Cruiser, laid down in 1939

Displacement:
15 190 t light; 15 706 t standard; 16 492 t normal; 17 121 t full load

Dimensions: Length overall / water x beam x draught
700,00 ft / 676,00 ft x 77,10 ft x 25,00 ft (normal load)
213,36 m / 206,04 m x 23,50 m x 7,62 m

Armament:
9 - 8,00" / 203 mm guns (3x3 guns), 256,00lbs / 116,12kg shells, 1937 Model
Breech loading guns in turrets (on barbettes)
on centreline ends, majority forward, 1 raised mount - superfiring
12 - 5,00" / 127 mm guns (6x2 guns), 62,50lbs / 28,35kg shells, 1935 Model
Dual purpose guns in turrets (on barbettes)
on side, all amidships
28 - 1,57" / 40,0 mm guns (7x4 guns), 1,95lbs / 0,88kg shells, 1936 Model
Anti-aircraft guns in deck mounts
on side, evenly spread
36 - 1,18" / 30,0 mm guns (18x2 guns), 0,82lbs / 0,37kg shells, 1938 Model
Anti-aircraft guns in deck mounts
on side, evenly spread
Weight of broadside 3 138 lbs / 1 423 kg
Shells per gun, main battery: 100
8 - 21,0" / 533,4 mm above water torpedoes

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 6,00" / 152 mm 460,00 ft / 140,21 m 17,50 ft / 5,33 m
Ends: Unarmoured
Main Belt covers 105 % of normal length

- Torpedo Bulkhead:
3,00" / 76 mm 460,00 ft / 140,21 m 10,00 ft / 3,05 m

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 8,00" / 203 mm 5,00" / 127 mm 8,00" / 203 mm
2nd: 3,00" / 76 mm 2,00" / 51 mm 3,00" / 76 mm

- Armour deck: 3,00" / 76 mm, Conning tower: 8,00" / 203 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 4 shafts, 83 757 shp / 62 482 Kw = 30,00 kts
Range 7 500nm at 12,00 kts
Bunker at max displacement = 1 415 tons

Complement:
726 - 945

Cost:
£6,856 million / $27,425 million

Distribution of weights at normal displacement:
Armament: 392 tons, 2,4 %
Armour: 5 557 tons, 33,7 %
- Belts: 2 010 tons, 12,2 %
- Torpedo bulkhead: 511 tons, 3,1 %
- Armament: 1 090 tons, 6,6 %
- Armour Deck: 1 835 tons, 11,1 %
- Conning Tower: 112 tons, 0,7 %
Machinery: 2 266 tons, 13,7 %
Hull, fittings & equipment: 6 875 tons, 41,7 %
Fuel, ammunition & stores: 1 302 tons, 7,9 %
Miscellaneous weights: 100 tons, 0,6 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
30 571 lbs / 13 867 Kg = 119,4 x 8,0 " / 203 mm shells or 5,1 torpedoes
Stability (Unstable if below 1.00): 1,09
Metacentric height 4,0 ft / 1,2 m
Roll period: 16,2 seconds
Steadiness - As gun platform (Average = 50 %): 79 %
- Recoil effect (Restricted arc if above 1.00): 0,46
Seaboat quality (Average = 1.00): 1,57

Hull form characteristics:
Hull has raised forecastle
Block coefficient: 0,443
Length to Beam Ratio: 8,77 : 1
'Natural speed' for length: 26,00 kts
Power going to wave formation at top speed: 49 %
Trim (Max stability = 0, Max steadiness = 100): 50
Bow angle (Positive = bow angles forward): 28,84 degrees
Stern overhang: 5,00 ft / 1,52 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 34,50 ft / 10,52 m
- Forecastle (20 %): 30,00 ft / 9,14 m (21,60 ft / 6,58 m aft of break)
- Mid (50 %): 22,50 ft / 6,86 m
- Quarterdeck (15 %): 22,50 ft / 6,86 m
- Stern: 24,50 ft / 7,47 m
- Average freeboard: 24,38 ft / 7,43 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 86,4 %
- Above water (accommodation/working, high = better): 172,9 %
Waterplane Area: 33 058 Square feet or 3 071 Square metres
Displacement factor (Displacement / loading): 124 %
Structure weight / hull surface area: 131 lbs/sq ft or 638 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0,95
- Longitudinal: 1,61
- Overall: 1,00
Hull space for machinery, storage, compartmentation is adequate
Room for accommodation and workspaces is excellent
Ship has slow, easy roll, a good, steady gun platform
Excellent seaboat, comfortable, can fire her guns in the heaviest weather

Hi Karle,

Looking good! I'm quite liking the Rome AU, but I do have a question ... given that the Roman inch was reported to be 24.6mm rather than the modern 25.4 (which, if I'm remembering correctly, is scaled from some old monarch's foot), wouldn't the gun sizes come down slightly in order to be round numbers for Rome? I mean, from an engineering standpoint what you've got is perfectly feasible, just feels ... off ... somehow for the Romans to be using old enough units to be on 203mm rather than 200, when you'd think they'd settle for 197mm (8 Roman inches) if they're not just to upgrade to metric.

Regards,
Adam

P.S.: "You're right, but I can't be bothered," counts as a perfectly valid answer as far as I'm concerned, as does "Who is OCD enough to check the size of Roman inches on a warship discussion board?"

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To be honest, I never though about going full immersive with proper Roman weight and length scale, as it will only create confusion as to how big something actually is. As you said, with modern inch it is 203 mm, the standard for all heavy cruisers, and not 197 mm.

Hi Karle,

Yeah, possibly a bit much, I was mainly interested in seeing if you'd model it in a similar fashion to the HSF and KM in WWI and WWII with lower-calibre, higher-velocity guns, but as you can see even without making efforts to improve the velocity the KE and weight of shell delivered to target are going to be just about the same regardless.

Ad

(another PS) - yeah, I remember the 203mm thing, was wondering if without the history establishing 25.4mm per inch if the calibre would ever get introduced. But, as you've said, it's probably more the OCD kicking in than delivering an actual tangible benefit to go completely Roman in the measurements...

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It's indeed impressive looking ship.

What a beautiful ship! Looks almost like a USN Atlanta-class CLAA with streamlined funnels, upgraded armament, and a clipper bow! LOVE this design!

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MS State Guard - 08 March 2014 - 28 January 2023

The Official IJN Ships & Planes List

#FJB

A very handsome looking ship.

Thanks for the praise. I can confirm that the superstructure is indeed based on that of the Atlanta class. I used it for its rather sleek and lower build, giving me a slightly more aggressive looking ship.

Great cruiser!

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kike-92