WesWorld

As more and more indications that the Hellenic Navy is planning to build a number of large and powerful battleships, the Regia Marina has been forced to reply in kind with various studies being drawn up. The final design, conjecturely pictured above, was chosen after much deliberation. The new battleships in service and still building for other countries were examined and incorporated into the new design. The cancelled Battleship laid down in 1928, Principe Eugenio di Savoia, was used as a starting point in the process, but with more modern building techniques and armament added. The protective scheme was also given a large overhaul with various factors taken under consideration. As a result, the Regia Marina will have a capability unparalleled around the world.

RN Roma, Italian Battleship laid down 1933

Displacement:
37,680 t light; 39,592 t standard; 43,818 t normal; 47,198 t full load

Dimensions: Length overall / water x beam x draught
771.20 ft / 744.75 ft x 106.41 ft x 34.25 ft (normal load)
235.06 m / 227.00 m x 32.43 m x 10.44 m

Armament:
9 - 15.00" / 381 mm guns (3x3 guns), 1,951.09lbs / 885.00kg shells, 1930 Model
Breech loading guns in turrets (on barbettes)
on centreline ends, majority forward, 1 raised mount - superfiring
24 - 3.94" / 100 mm guns (12x2 guns), 33.07lbs / 15.00kg shells, 1933 Model
Anti-aircraft guns in deck mounts with hoists
on side, all amidships, 4 raised mounts - superfiring
24 - 1.46" / 37.0 mm guns (6x4 guns), 1.83lbs / 0.83kg shells, 1933 Model
Anti-aircraft guns in deck mounts
on side, evenly spread, 2 raised mounts
16 - 1.00" / 25.4 mm guns (4x4 guns), 0.50lbs / 0.23kg shells, 1933 Model
Anti-aircraft guns in deck mounts
on centreline ends, evenly spread
Weight of broadside 18,405 lbs / 8,349 kg
Shells per gun, main battery: 100

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 13.8" / 350 mm 426.51 ft / 130.00 m 13.12 ft / 4.00 m
Ends: 2.76" / 70 mm 196.85 ft / 60.00 m 13.12 ft / 4.00 m
121.39 ft / 37.00 m Unarmoured ends
Upper: 2.76" / 70 mm 426.51 ft / 130.00 m 8.20 ft / 2.50 m
Main Belt covers 88 % of normal length

- Torpedo Bulkhead:
2.99" / 76 mm 426.51 ft / 130.00 m 44.09 ft / 13.44 m

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 16.9" / 430 mm 9.06" / 230 mm 13.0" / 330 mm
3rd: 1.18" / 30 mm 0.79" / 20 mm -
4th: 0.39" / 10 mm 0.39" / 10 mm -
5th: 0.39" / 10 mm - -

- Armour deck: 40mm forwards / 25+125mm over machinery / 25+145mm over magazines / 100mm over steering gear, Conning tower: 2.76" / 70 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 4 shafts, 140,000 shp / 104,440 Kw = 29.03 kts
Range 2,600nm at 29.03 kts
Bunker at max displacement = 7,607 tons

Complement:
1,513 - 1,968

Cost:
£16.858 million / $67.433 million

Distribution of weights at normal displacement:
Armament: 1,996 tons, 4.6 %
Armour: 15,121 tons, 34.5 %
- Belts: 4,120 tons, 9.4 %
- Torpedo bulkhead: 2,082 tons, 4.8 %
- Armament: 3,291 tons, 7.5 %
- Armour Deck: 5,555 tons, 12.7 %
- Conning Tower: 74 tons, 0.2 %
Machinery: 4,079 tons, 9.3 %
Hull, fittings & equipment: 16,184 tons, 36.9 %
Fuel, ammunition & stores: 6,138 tons, 14.0 %
Miscellaneous weights: 300 tons, 0.7 %

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
64,317 lbs / 29,174 Kg = 38.1 x 15.0 " / 381 mm shells or 11.3 torpedoes
Stability (Unstable if below 1.00): 1.16
Metacentric height 7.3 ft / 2.2 m
Roll period: 16.6 seconds
Steadiness - As gun platform (Average = 50 %): 51 %
- Recoil effect (Restricted arc if above 1.00): 0.58
Seaboat quality (Average = 1.00): 1.06

Hull form characteristics:
Hull has low quarterdeck
Block coefficient: 0.565
Length to Beam Ratio: 7.00 : 1
'Natural speed' for length: 27.29 kts
Power going to wave formation at top speed: 53 %
Trim (Max stability = 0, Max steadiness = 100): 48
Bow angle (Positive = bow angles forward): 30.00 degrees
Stern overhang: 6.56 ft / 2.00 m
Freeboard (% = measuring location as a percentage of overall length):
- Stem: 34.45 ft / 10.50 m
- Forecastle (20 %): 22.97 ft / 7.00 m
- Mid (80 %): 21.33 ft / 6.50 m
- Quarterdeck (20 %): 13.12 ft / 4.00 m (31.17 ft / 9.50 m before break)
- Stern: 13.12 ft / 4.00 m
- Average freeboard: 21.42 ft / 6.53 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 81.4 %
- Above water (accommodation/working, high = better): 156.4 %
Waterplane Area: 56,090 Square feet or 5,211 Square metres
Displacement factor (Displacement / loading): 111 %
Structure weight / hull surface area: 206 lbs/sq ft or 1,005 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.96
- Longitudinal: 1.40
- Overall: 1.00
Hull space for machinery, storage, compartmentation is excellent
Room for accommodation and workspaces is excellent

40mm forwards
25+125mm over machinery
25+145mm over magazines
100mm over steering gear
=135.97mm average

Hmmmm. If the RMI didn't think the 100mm gun is sufficient against destroyers before, why have they changed their minds? I'd think, in the relatively confined waters of the Med (like the Baltic) that a heavier secondary battery would be recommended.

Before when?

High-velocity 65 calibre 100mm gun in powered mounts with rate of fire up to 22-24rpmpg (normal 16-1 and 24 barrels, and the special shell which ensures a quick destruction of smaller vessels.

Since 1928, when PEdS was being laid down with 130mm secondaries?

Since your comments in the thread on the proposed Blucher design, "With regards to 130 vs. 105. Italians have calculated that the 130mm/45? gun is about 80-90% more effective than the 105/65 in the anti-surface role"?


I'm not disagreeing that the 100mm would do the job (though not as rapidly or as surely as a 130-152mm), I'm just finding the about face rather interesting.

Quoted

With regards to 130 vs. 105. Italians have calculated that the 130mm/45? gun is about 80-90% more effective than the 105/65 in the anti-surface role"?

The 130/45 is only about 50% more effective than the 100/65 in ASuW and about 30% less effective for AA.

Splitting the secondary battery is no longer an option so it was a choice between 135mm or 100mm. There wasn't a great deal of choice here as the 135/45 is low-angle with only 40° elevation and is not a dedicated AA gun. The shell is a bit heavy as well and only 6 duple mounts would fit. The decision to change to 12 duple 100/65 was quite easy.

Another reason is the large hoists for the 135mm guns interfering with below decks arrangements.

Likely threats? The French and Greek destroyers are all fairly small. The 152mm is not neccessary as there are no contre-torpilleurs like Le Fantasque.

Why is splitting the secondaries no longer an option? What combat experience has shown aircraft to be a threat to a major warship like Roma?

Quoted

The 130/45 is only about 50% more effective than the 100/65 in ASuW and about 30% less effective for AA.

Interesting how much the 130mm has slid since the original quote was posted.

Quoted

Likely threats? The French and Greek destroyers are all fairly small. The 152mm is not neccessary as there are no contre-torpilleurs like Le Fantasque

Heh. Hint to France and Greece, eh?

Quoted

Why is splitting the secondaries no longer an option?

Space.

Quoted

Interesting how much the 130mm has slid since the original quote was posted.

The 130/45 has stayed the same. The 100/65 and 105/65 are different weapons with different performances.

Confused here. If the secondaries are deck mounts, doesn't that imply manual loading? Can a crew manually handle 33 lb shells every two and a half seconds? Sounds like a drill error or accident waiting to happen.

On the other hand, if the mounts are mechanically loaded, I'd expect them to be simmed as turrets.

She's a powerful ship, but doesn't strike me as being any more capable than the older Memnon or Ophion, for example.

Both the 135/45 and 100/65 are semi-automatic with horizontally sliding breech blocks. Both mounts have below deck penetrations with hoists linking them to magazines below decks. This is opposed to unpowered deck mounts fed by ammunition lockers on deck level.

My comment before was to do with the size of the hoists needed for a duple or triple 135mm gun. Twice as many hoists for a start because the ammunition is split. Then the hoists are individually larger and there are three guns to service. It all adds up to a complicated and sizable mess.

Quoted

She's a powerful ship, but doesn't strike me as being any more capable than the older Memnon or Ophion, for example.

Better firepower from the 381/50 guns. A bit faster than Memnon. Greatly superior armour than Ophion or Memnon. More survivability. Of course she isn't a massive improvement, but thats because the displacement is fixed at 40.000tons.

Quoted

The 130/45 has stayed the same. The 100/65 and 105/65 are different weapons with different performances.

Not by much. The WW 105/65 fires a somewhat heavier shell (16.02 kg vs 15 kg) to similar velocities, and in the enclosed powered mounting used in WW Germany will have about the same rate of fire. So there's little reason to believe that the 100/65 will be a much better performer.

Quoted

Better firepower from the 381/50 guns. A bit faster than Memnon. Greatly superior armour than Ophion or Memnon. More survivability. Of course she isn't a massive improvement, but thats because the displacement is fixed at 40.000tons.

Better firepower, granted. A little faster, granted, but as you've pointed out before, a difference of 1 knot isn't a lot. "Greatly superior armor", though? Better end armor, surely, but the belt is lighter, the deck is lighter, and the upper belt isn't heavy enough to make much difference against heavy shells.

22-24 RPM - sounds like propaganda to me. ;o)

Semi-automatic 100mm gun mounts? I´m sure you have some sources at hand to give use more technical insight? Can we expect those guns to be prone to jamming?

The Italians use superheavy 381mm shells for their 50 caliber guns? Guess we need to read "barrel wear" between the lines....

Regarding protection one would expect improvements on a ship 9 years younger than OPHION - but I wouldn´t rate them as "greatly superior". Yes, your face plates are thicker (even though 400mm is already suffice against standard 380mm shells and your main turrets sides and back plates are thinner) and especially the thicker TB gives your design an edge (at the cost of weight - which is countered by a more modern machinery with similar output) but I wonder what the forward/aft and upper belts are for? I cannot understand your design philosophy here. Same for her deck armor (Btw, I´d like to have values NOT modified here. What´s the deck armor thickness entered in SS?)

You seem to aim for long range duels in general where your very heavy main gun shells can proof to be good deck penetrators (for other ranges a high velocity/light shell combination would have been more useful). However, in such a duel neither a fore, aft or upper belt will be of much help. But a thick deck armor would....

And finally your design lacks adequat CT armor - which means your command stuff will have hard times when "unfriendly" shells are comming in.

In the end I cannot see that ROMA is superior by much to older designs.

I read about German semi-Automatic guns in the late 1920s... so how was the german experience with those guns. I would expect that the Italians (and the Japanese as well) would have the same problems as the Germans.

Quoted

The Italians use superheavy 381mm shells for their 50 caliber guns? Guess we need to read "barrel wear" between the lines....

Should be obvious. What do you recon? 250 shells max before the liners need to be replaced?

Quoted

(Btw, I´d like to have values NOT modified here. What´s the deck armor thickness entered in SS?)

I'd expect it to be 135.97mm as given in the calculation at the bottom of the sim. I tested the ship myself to see if it was correct (I actually simmed it at 136mm) and I got the same deck weight (5,555 tons).

Quoted

And finally your design lacks adequat CT armor - which means your command stuff will have hard times when "unfriendly" shells are comming in.

You're still not used to the infamous spagetti-style CT armor??

Quoted

Same for her deck armor (Btw, I´d like to have values NOT modified here. What´s the deck armor thickness entered in SS?)

Appears to be approximately 136mm, based on the comments at the end of the file.

Quoted

The Italians use superheavy 381mm shells for their 50 caliber guns? Guess we need to read "barrel wear" between the lines....

Not necessarily: the US 16" Mk 7 had an approximate barrel life of 290+ rounds, which isn't too bad.

Of course, the historical Italian 15"/50 with this 885 kg projectile WAS a terrible barrel-burner: it had an expected barrel life of only 110-130 rounds.

It won't be a good gun for firing at enemy decks, the high velocity and high retained velocity (from the heavy shell) will keep the trajectory flat out through the useful firing ranges. However, the heavy shell and high velocity will give it good belt penetration even at long ranges (assuming the shell holds together, a fair question given Italian quality control).

Considering were this ship could be stationed and the likely ranges of combat with say Greek battleships...the Greeks probably have just as good of a vessel on a smaller hull with 14 inch guns. What was the record for a hit, slightly over 26,000 yards? What is the more likely combat range?

Quoted

Of course, the historical Italian 15"/50 with this 885 kg projectile WAS a terrible barrel-burner: it had an expected barrel life of only 110-130 rounds.

Good thing it only carries 100 rounds. By the time you need to fill up the magazines, you'll need to replace the liners.

Quoted

I read about German semi-Automatic guns in the late 1920s... so how was the german experience with those guns. I would expect that the Italians (and the Japanese as well) would have the same problems as the Germans.

Depends on whether we're talking about a semi-automatic gun, or a semi-automatic breech. There's NO chance of a semi-automatic 4" gun at this time period, the earliest shipboard mountings I can find are post WWII (1947 for the 4.5"/45 QF Mark V, 1948 for the 3"/50RF Mk 27, and around 1946-7 for the 12.7 cm/45 (5") SK C/41 (never actually built)).
Semi-automatic breeches, on the other hand, are certainly available, they were included on the 15 cm/45 (5.9") Tbts KL/45 that the S.113-class large torpedoboats of the German Navy was building at the end of WWI, the two that were completed were transferred to France and Italy as part of the Versailles Treaty.

Quoted

What was the record for a hit, slightly over 26,000 yards? What is the more likely combat range?

Correct, and there were only 2 out that far. More common battle ranges would be under 25,000 for hits, in daylight firing on a moving target. At night, well, subtract a fair amount.

Yes, I meant the breech... but I still refer to it as a semi-automatic gun (eventhough the definition of that 'semi-automatic gun' would be different from the one you are referring to).

Quoted

they were included on the 15 cm/45 (5.9") Tbts KL/45 that the S.113-class large torpedoboats of the German Navy was building at the end of WWI, the two that were completed were transferred to France and Italy as part of the Versailles Treaty.

Good to know that. I was actually reading a wikipedia article about a german AA gun (I think it was a predecessor of the FlAK 36) which used the semi automatic breech. That was 1927/1928.

@Hrolf

The 100/65 has about 100m/s more velocity and longer range plus those special shells...In other ways the guns and mounts are very similar.

The belt might be thinner, but it is more effective.

@ Stephan

22/24 is possible for short periods with trained crew and no fuse setting.

Semi-automatic breech blocks, not guns. Normal for Italian guns of the period.

Superheavy shells? 885kg is moderate. This is the historical weapon. I could electro-plate the barrel to give 20% more barrel life as costs don't factor here. The loose-liners employed by Italy mean that the liner can be changed in about 12/24hours or so.

The end belts are to stop splinters and smaller shells like historical. The upper belt decaps projectiles before they strike the main deck and stops splinters and small shells, like historical.

Main belt armour is 70+280@15° like historical with a 40mm splinter plate behind this that continues into the TDS. I'll draw a picture.

The 381/50 is a poor deck penetrator because of it's high muzzle velocity. This is not a problem as the armour-piercing capabilities are greatly enhanced.

Deck armour - the thinnest part, 125mm main deck is proof against 16"/45 2700lb(worse-case) until 260hm. That is enough.

Average thickness is 135.97 as pointed out.

The thin conning tower ensures the survival of the staff in hte conning tower. Have an 18" thick CT. A shell hits it and sends splinters shooting off the back and basically vaporises part of the plate into high velocity metal gas which promptly kills everything in the CT.

@HH

Got to assume equal quality between all nation here. Look at the news. The quality control problem was solved with a thorough overview. Now the gun(under development since 1927) is very accurate and very powerful, as it historically was.

@Ithreko

With the 381/50, if you can hit the target you can penetrate it.

Out of curiosity, what would the effect of a battleship of this size be of a large caliber HE shell? Say a 12-14 inch shell.