Shipbucket

I will admit the firepower is not as heavy as it could be, however if it turns out to be insufficient then the option of 17.5 inch weapons still remains, which hopefully would put this on more even terms against the superheavy gun warships. Furthermore, the armor isn't just about protecting against 18 inch type weapons, it also is intended to grant a wider zone of immunity to 15 and 16 inch gun designs (Tosa and SoDak are two examples of 16 inch non-treaty type battleships of this era). Which, I think it accomplishes nicely.

The ship is a complete slug, the designers were thinking along the same kinds of lines as the SoDak (21) and G3 (23) type ships in building a heavy slug rather than a faster, more balanced combatant.

The first group of twins was supposed to be triples, I'll have to edit that. She uses an armament layout the same type as seen on the Nevadas, since compared to a traditional five twin turret scheme it offers better firepower ahead, astern, and it eliminates a turret from the middle to make the engine room layout more spacious.

The AA is indeed extremely heavy for 1925. This is deliberate, as the Admiralty assumed that ships of such immense dimensions would be the most easy targets to hit in an air raid. Thus, it was appropriate to arm them heavily with anti-air weaponry.

I'm not sure why the seaboat quality is so high, but I'm rather glad for it. Being able to have high performance in treacherous sea conditions surely could come in handy.

Here's a SS report on a version with the 16 inch guns swapped for 17.5s:

Tannhauser, Regia Nautica Battleship laid down 1925

Displacement:
64,028 t light; 67,049 t standard; 71,621 t normal; 75,280 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(864.64 ft / 850.00 ft) x 118.00 ft (Bulges 128.00 ft) x (36.00 / 37.68 ft)
(263.54 m / 259.08 m) x 35.97 m (Bulges 39.01 m) x (10.97 / 11.49 m)

Armament:
8 - 17.50" / 445 mm 45.0 cal guns - 2,702.53lbs / 1,225.85kg shells, 80 per gun
Breech loading guns in turret on barbette mounts, 1918 Model
2 x Twin mounts on centreline, evenly spread
2 x Twin mounts on centreline, evenly spread
2 raised mounts
Aft Main mounts separated by engine room
24 - 6.00" / 152 mm 52.0 cal guns - 115.32lbs / 52.31kg shells, 300 per gun
Quick firing guns in turret on barbette mounts, 1918 Model
8 x Triple mounts on sides, evenly spread
4 raised mounts
16 - 4.00" / 102 mm 50.0 cal guns - 33.88lbs / 15.37kg shells, 450 per gun
Dual purpose guns in deck and hoist mounts, 1925 Model
8 x Twin mounts on sides, evenly spread
4 raised mounts
16 - 1.25" / 31.8 mm 50.0 cal guns - 1.03lbs / 0.47kg shells, 3,000 per gun
Anti-air guns in deck mounts, 1920 Model
8 x Twin mounts on sides, evenly spread
4 raised mounts
12 - 0.50" / 12.7 mm 90.0 cal guns - 0.07lbs / 0.03kg shells, 6,000 per gun
Machine guns in deck mounts, 1916 Model
12 x Single mounts on sides amidships
8 raised mounts
Weight of broadside 24,947 lbs / 11,316 kg

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 17.0" / 432 mm 544.00 ft / 165.81 m 24.00 ft / 7.32 m
Ends: Unarmoured
Main Belt covers 98 % of normal length

- Torpedo Bulkhead:
4.00" / 102 mm 560.00 ft / 170.69 m 60.00 ft / 18.29 m

- Hull Bulges:
0.50" / 13 mm 560.00 ft / 170.69 m 30.00 ft / 9.14 m

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 23.0" / 584 mm 10.0" / 254 mm 17.0" / 432 mm
2nd: 3.00" / 76 mm 1.00" / 25 mm 1.00" / 25 mm
3rd: 0.50" / 13 mm - -

- Armoured deck - single deck: 9.20" / 234 mm For and Aft decks

- Conning towers: Forward 22.00" / 559 mm, Aft 0.00" / 0 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 4 shafts, 65,946 shp / 49,195 Kw = 22.00 kts
Range 10,000nm at 15.00 kts
Bunker at max displacement = 8,231 tons

Complement:
2,188 - 2,845

Cost:
£16.094 million / $64.376 million

Distribution of weights at normal displacement:
Armament: 4,260 tons, 5.9 %
Armour: 31,994 tons, 44.7 %
- Belts: 9,588 tons, 13.4 %
- Torpedo bulkhead: 4,973 tons, 6.9 %
- Bulges: 311 tons, 0.4 %
- Armament: 5,689 tons, 7.9 %
- Armour Deck: 10,616 tons, 14.8 %
- Conning Tower: 817 tons, 1.1 %
Machinery: 2,141 tons, 3.0 %
Hull, fittings & equipment: 22,853 tons, 31.9 %
Fuel, ammunition & stores: 7,593 tons, 10.6 %
Miscellaneous weights: 2,780 tons, 3.9 %
- Hull below water: 300 tons
- Bulge void weights: 600 tons
- Hull above water: 300 tons
- On freeboard deck: 950 tons
- Above deck: 630 tons

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
163,814 lbs / 74,305 Kg = 61.1 x 17.5 " / 445 mm shells or 48.7 torpedoes
Stability (Unstable if below 1.00): 1.16
Metacentric height 8.5 ft / 2.6 m
Roll period: 18.5 seconds
Steadiness - As gun platform (Average = 50 %): 86 %
- Recoil effect (Restricted arc if above 1.00): 0.63
Seaboat quality (Average = 1.00): 1.64

Hull form characteristics:
Hull has rise forward of midbreak,
a normal bow and a round stern
Block coefficient (normal/deep): 0.640 / 0.643
Length to Beam Ratio: 6.64 : 1
'Natural speed' for length: 29.15 kts
Power going to wave formation at top speed: 37 %
Trim (Max stability = 0, Max steadiness = 100): 52
Bow angle (Positive = bow angles forward): 10.00 degrees
Stern overhang: 9.00 ft / 2.74 m
Freeboard (% = length of deck as a percentage of waterline length):
Fore end, Aft end
- Forecastle: 20.00 %, 32.00 ft / 9.75 m, 27.00 ft / 8.23 m
- Forward deck: 30.00 %, 27.00 ft / 8.23 m, 26.00 ft / 7.92 m
- Aft deck: 35.00 %, 25.00 ft / 7.62 m, 25.00 ft / 7.62 m
- Quarter deck: 15.00 %, 25.00 ft / 7.62 m, 26.00 ft / 7.92 m
- Average freeboard: 26.33 ft / 8.02 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 50.4 %
- Above water (accommodation/working, high = better): 170.3 %
Waterplane Area: 76,133 Square feet or 7,073 Square metres
Displacement factor (Displacement / loading): 116 %
Structure weight / hull surface area: 224 lbs/sq ft or 1,095 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.96
- Longitudinal: 1.36
- Overall: 1.00
Hull space for machinery, storage, compartmentation is excellent
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

If you don't mind here is my try at a much cheaper alternative none treaty 18" slow Battleship.

Cheaper Alternative, Regia Nautica No WNT Battleship laid down 1925

Displacement:
42,209 t light; 44,617 t standard; 48,187 t normal; 51,042 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(602.19 ft / 600.00 ft) x 128.00 ft x (36.00 / 37.76 ft)
(183.55 m / 182.88 m) x 39.01 m x (10.97 / 11.51 m)

Armament:
9 - 18.00" / 457 mm 45.0 cal guns - 2,940.86lbs / 1,333.95kg shells, 80 per gun
Breech loading guns in turret on barbette mounts, 1923 Model
3 x Triple mounts on centreline ends, majority forward
1 raised mount - superfiring
16 - 6.00" / 152 mm 52.0 cal guns - 115.32lbs / 52.31kg shells, 200 per gun
Breech loading guns in turret on barbette mounts, 1918 Model
6 x Triple mounts on sides, evenly spread
2 raised mounts
8 - 4.00" / 102 mm 50.0 cal guns - 33.88lbs / 15.37kg shells, 400 per gun
Anti-air guns in deck mounts, 1925 Model
8 x Single mounts on sides, evenly spread
8 raised mounts
12 - 0.50" / 12.7 mm 90.0 cal guns - 0.07lbs / 0.03kg shells, 5,000 per gun
Machine guns in deck mounts, 1916 Model
12 x Single mounts on sides, evenly spread
12 double raised mounts
Weight of broadside 28,585 lbs / 12,966 kg

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 15.0" / 381 mm 360.00 ft / 109.73 m 24.00 ft / 7.32 m
Ends: Unarmoured
Main Belt covers 92 % of normal length
Main Belt inclined 10.00 degrees (positive = in)

- Torpedo Bulkhead - Strengthened structural bulkheads:
4.00" / 102 mm 552.50 ft / 168.40 m 50.00 ft / 15.24 m
Beam between torpedo bulkheads 90.00 ft / 27.43 m

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 23.0" / 584 mm 10.0" / 254 mm 17.0" / 432 mm
2nd: 3.00" / 76 mm 1.00" / 25 mm 3.00" / 76 mm
3rd: 0.50" / 13 mm - -
4th: 0.30" / 8 mm - -

- Armoured deck - single deck:
For and Aft decks: 7.00" / 178 mm
Forecastle: 0.00" / 0 mm Quarter deck: 2.00" / 51 mm

- Conning towers: Forward 15.00" / 381 mm, Aft 5.00" / 127 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 4 shafts, 57,619 shp / 42,984 Kw = 22.00 kts
Range 10,000nm at 15.00 kts
Bunker at max displacement = 6,425 tons

Complement:
1,626 - 2,114

Cost:
£14.471 million / $57.885 million

Distribution of weights at normal displacement:
Armament: 4,636 tons, 9.6 %
- Guns: 4,636 tons, 9.6 %
Armour: 21,660 tons, 45.0 %
- Belts: 6,137 tons, 12.7 %
- Torpedo bulkhead: 4,089 tons, 8.5 %
- Armament: 4,637 tons, 9.6 %
- Armour Deck: 6,228 tons, 12.9 %
- Conning Towers: 571 tons, 1.2 %
Machinery: 1,871 tons, 3.9 %
Hull, fittings & equipment: 13,043 tons, 27.1 %
Fuel, ammunition & stores: 5,977 tons, 12.4 %
Miscellaneous weights: 1,000 tons, 2.1 %
- On freeboard deck: 500 tons
- Above deck: 500 tons

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
70,062 lbs / 31,780 Kg = 24.0 x 18.0 " / 457 mm shells or 16.9 torpedoes
Stability (Unstable if below 1.00): 1.26
Metacentric height 11.0 ft / 3.3 m
Roll period: 16.2 seconds
Steadiness - As gun platform (Average = 50 %): 60 %
- Recoil effect (Restricted arc if above 1.00): 0.44
Seaboat quality (Average = 1.00): 1.21

Hull form characteristics:
Hull has a flush deck,
a normal bow and a cruiser stern
Block coefficient (normal/deep): 0.610 / 0.616
Length to Beam Ratio: 4.69 : 1
'Natural speed' for length: 24.49 kts
Power going to wave formation at top speed: 50 %
Trim (Max stability = 0, Max steadiness = 100): 50
Bow angle (Positive = bow angles forward): 5.00 degrees
Stern overhang: 0.00 ft / 0.00 m
Freeboard (% = length of deck as a percentage of waterline length):
Fore end, Aft end
- Forecastle: 20.00 %, 25.00 ft / 7.62 m, 21.00 ft / 6.40 m
- Forward deck: 30.00 %, 21.00 ft / 6.40 m, 18.00 ft / 5.49 m
- Aft deck: 35.00 %, 18.00 ft / 5.49 m, 18.00 ft / 5.49 m
- Quarter deck: 15.00 %, 18.00 ft / 5.49 m, 18.00 ft / 5.49 m
- Average freeboard: 19.37 ft / 5.90 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 89.4 %
- Above water (accommodation/working, high = better): 124.1 %
Waterplane Area: 56,697 Square feet or 5,267 Square metres
Displacement factor (Displacement / loading): 93 %
Structure weight / hull surface area: 254 lbs/sq ft or 1,242 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.93
- Longitudinal: 2.00
- Overall: 1.00
Adequate machinery, storage, compartmentation space
Excellent accommodation and workspace room
Good seaboat, rides out heavy weather easily

- Not sure believe the cost estimates cost will be very linked to weight and mine is 42,209 t light v your 64,028 t light that and the crew size should make it closer to 2/3 the cost IMO

- 9 x 18" should be the equal of 10 x 17.5" and I have cut numbers of 6" as I just don't think you need as many, I can still fire 9 guns each side on most arcs and at least 6 on any bearing

- Not fitted the 1.25" as .5" should work v 1925 biplanes and is more realistic IMO as well as numbers of 4" guns

- Cut the protection as its still more than N3 (or any other RL design)

- Cut length so she can fit into RL slipways and docks and to reduce cost

- I would go for more speed but that's your navy's choice....

It's an interesting design, but certainly one that would never be accepted in the context of the fictional navy I'm working on. For one, at 44,000 tons standard it wallows at 11k tons less than the 55,000 tons standard originally allotted for the type in the first place. It's too light. Also, it's far too stumpy and fat, the length to beam ratio is absurd.

There is also too much emphasis on firepower and not enough on protection, it's barely equal to N3 in regards of armor. Our navy puts firepower as subservient to armor protection, unlike others who may feel the need to balance speed and firepower against armor. Perhaps it is a doctrine of faulty logic, but I never intended to create a doctrine that would build perfectly balanced warship designs.

How is a 1.25 inch AA autocannon unrealistic in any way? According to Navweaps the Royal Navy was fitting the early marks of 2 pounder pom-poms as early as 1915, and the 1.25 is simply a lighter fictional counterpart to the pom-pom.

And with a 128 foot beam it's going to fit in what docks exactly? It's wider than Yamato by a fairly meaningful margin, I think that huge of a beam would cause it far more trouble. 865 feet, after all, is still shorter than USS Lexington.

Here is an example of a ship built at the allotted 55,000 tons, with what would be considered the very minimum for armor protection and nothing more:

Displacement:
52,466 t light; 54,992 t standard; 57,288 t normal; 59,124 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(783.94 ft / 770.00 ft) x 116.00 ft (Bulges 124.00 ft) x (35.00 / 35.98 ft)
(238.94 m / 234.70 m) x 35.36 m (Bulges 37.80 m) x (10.67 / 10.97 m)

Armament:
8 - 18.00" / 457 mm 45.0 cal guns - 2,940.86lbs / 1,333.95kg shells, 80 per gun
Breech loading guns in turret on barbette mounts, 1925 Model
4 x Twin mounts on centreline ends, evenly spread
2 raised mounts - superfiring
16 - 6.00" / 152 mm 52.0 cal guns - 115.32lbs / 52.31kg shells, 250 per gun
Quick firing guns in turret on barbette mounts, 1925 Model
8 x Twin mounts on sides, evenly spread
4 raised mounts
8 - 4.00" / 102 mm 45.0 cal guns - 32.27lbs / 14.64kg shells, 400 per gun
Anti-air guns in deck mounts, 1925 Model
8 x Single mounts on sides amidships
16 - 1.25" / 31.8 mm 50.0 cal guns - 1.03lbs / 0.47kg shells, 2,000 per gun
Anti-air guns in deck mounts, 1925 Model
8 x Twin mounts on sides amidships
4 raised mounts
16 - 0.50" / 12.7 mm 90.0 cal guns - 0.07lbs / 0.03kg shells, 4,000 per gun
Machine guns in deck mounts, 1925 Model
16 x Single mounts on sides amidships
8 raised mounts
Weight of broadside 25,648 lbs / 11,634 kg

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 16.0" / 406 mm 490.00 ft / 149.35 m 22.00 ft / 6.71 m
Ends: Unarmoured
Main Belt covers 98 % of normal length

- Torpedo Bulkhead:
3.00" / 76 mm 530.00 ft / 161.54 m 55.00 ft / 16.76 m

- Hull Bulges:
0.00" / 0 mm 0.00 ft / 0.00 m 0.00 ft / 0.00 m

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 20.0" / 508 mm 12.0" / 305 mm 16.0" / 406 mm
2nd: 1.00" / 25 mm 1.00" / 25 mm 1.00" / 25 mm

- Armoured deck - single deck: 8.00" / 203 mm For and Aft decks

- Conning towers: Forward 20.00" / 508 mm, Aft 0.00" / 0 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 4 shafts, 58,188 shp / 43,408 Kw = 22.00 kts
Range 5,500nm at 15.00 kts
Bunker at max displacement = 4,132 tons

Complement:
1,850 - 2,406

Cost:
£14.756 million / $59.024 million

Distribution of weights at normal displacement:
Armament: 4,178 tons, 7.3 %
Armour: 24,739 tons, 43.2 %
- Belts: 7,533 tons, 13.1 %
- Torpedo bulkhead: 3,236 tons, 5.6 %
- Armament: 5,401 tons, 9.4 %
- Armour Deck: 7,929 tons, 13.8 %
- Conning Tower: 640 tons, 1.1 %
Machinery: 1,889 tons, 3.3 %
Hull, fittings & equipment: 20,385 tons, 35.6 %
Fuel, ammunition & stores: 4,822 tons, 8.4 %
Miscellaneous weights: 1,275 tons, 2.2 %
- Hull below water: 200 tons
- Bulge void weights: 150 tons
- Hull above water: 200 tons
- On freeboard deck: 510 tons
- Above deck: 215 tons

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
106,047 lbs / 48,102 Kg = 36.4 x 18.0 " / 457 mm shells or 26.0 torpedoes
Stability (Unstable if below 1.00): 1.14
Metacentric height 8.0 ft / 2.5 m
Roll period: 18.4 seconds
Steadiness - As gun platform (Average = 50 %): 74 %
- Recoil effect (Restricted arc if above 1.00): 0.63
Seaboat quality (Average = 1.00): 1.47

Hull form characteristics:
Hull has a flush deck,
a normal bow and a round stern
Block coefficient (normal/deep): 0.600 / 0.602
Length to Beam Ratio: 6.21 : 1
'Natural speed' for length: 27.75 kts
Power going to wave formation at top speed: 39 %
Trim (Max stability = 0, Max steadiness = 100): 50
Bow angle (Positive = bow angles forward): 10.00 degrees
Stern overhang: 9.00 ft / 2.74 m
Freeboard (% = length of deck as a percentage of waterline length):
Fore end, Aft end
- Forecastle: 20.00 %, 28.00 ft / 8.53 m, 24.00 ft / 7.32 m
- Forward deck: 30.00 %, 24.00 ft / 7.32 m, 22.00 ft / 6.71 m
- Aft deck: 35.00 %, 22.00 ft / 6.71 m, 22.00 ft / 6.71 m
- Quarter deck: 15.00 %, 22.00 ft / 6.71 m, 21.00 ft / 6.40 m
- Average freeboard: 22.95 ft / 6.99 m
Ship tends to be wet forward

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 60.4 %
- Above water (accommodation/working, high = better): 151.1 %
Waterplane Area: 65,327 Square feet or 6,069 Square metres
Displacement factor (Displacement / loading): 109 %
Structure weight / hull surface area: 239 lbs/sq ft or 1,164 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.97
- Longitudinal: 1.45
- Overall: 1.01
Hull space for machinery, storage, compartmentation is excellent
Room for accommodation and workspaces is excellent
Ship has slow, easy roll, a good, steady gun platform
Good seaboat, rides out heavy weather easily

EDIT: swapped in a proper 55k tonner version, the original specs i posted only totaled 53k at standard.