Shipbucket

I'm no expert in naval weapons ballistics, so I was hoping there might be people on this forum who are. I design quite a few fictional ships and one in particular has been a favorite project of mine, a little beauty called the Tannhauser class batteships. Built in response to the escalation of naval guns in the 1920s, in a fictional universe where no equivalent to the WNT was ever conceived, they posses immense armor of a scale never seen on any warship put to sea. Here is the Springsharp file detailing these behemoths:

Tannhauser, Regia Nautica Battleship laid down 1925

Displacement:
60,406 t light; 63,838 t standard; 68,264 t normal; 71,805 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(864.64 ft / 850.00 ft) x 116.00 ft (Bulges 122.00 ft) x (36.00 / 37.66 ft)
(263.54 m / 259.08 m) x 35.36 m (Bulges 37.19 m) x (10.97 / 11.48 m)

Armament:
10 - 16.00" / 406 mm 45.0 cal guns - 2,365.46lbs / 1,072.96kg shells, 110 per gun
Breech loading guns in turret on barbette mounts, 1925 Model
2 x Triple 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, 2,550 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 56.0 cal guns - 0.07lbs / 0.03kg shells, 2,800 per gun
Machine guns in deck mounts, 1916 Model
12 x Single mounts on sides amidships
8 raised mounts
Weight of broadside 26,982 lbs / 12,239 kg

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 23.0" / 584 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 36.00 ft / 10.97 m

- Hull Bulges:
1.00" / 25 mm 560.00 ft / 170.69 m 35.00 ft / 10.67 m

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 28.0" / 711 mm 18.0" / 457 mm 20.0" / 508 mm
2nd: 3.00" / 76 mm 1.00" / 25 mm 1.00" / 25 mm
3rd: 0.50" / 13 mm - -

- Box over machinery & magazines: 10.00" / 254 mm

- Conning towers: Forward 30.00" / 762 mm, Aft 0.00" / 0 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 4 shafts, 87,642 shp / 65,381 Kw = 24.00 kts
Range 10,000nm at 15.00 kts
Bunker at max displacement = 7,966 tons

Complement:
2,111 - 2,745

Cost:
£15.708 million / $62.834 million

Distribution of weights at normal displacement:
Armament: 4,225 tons, 6.2 %
Armour: 27,468 tons, 40.2 %
- Belts: 12,963 tons, 19.0 %
- Torpedo bulkhead: 2,984 tons, 4.4 %
- Bulges: 725 tons, 1.1 %
- Armament: 7,138 tons, 10.5 %
- Armour Deck: 2,579 tons, 3.8 %
- Conning Tower: 1,080 tons, 1.6 %
Machinery: 2,846 tons, 4.2 %
Hull, fittings & equipment: 23,068 tons, 33.8 %
Fuel, ammunition & stores: 7,858 tons, 11.5 %
Miscellaneous weights: 2,800 tons, 4.1 %
- Hull below water: 300 tons
- Bulge void weights: 550 tons
- Hull above water: 400 tons
- On freeboard deck: 850 tons
- Above deck: 700 tons

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
136,960 lbs / 62,124 Kg = 66.9 x 16.0 " / 406 mm shells or 31.9 torpedoes
Stability (Unstable if below 1.00): 1.09
Metacentric height 7.3 ft / 2.2 m
Roll period: 18.9 seconds
Steadiness - As gun platform (Average = 50 %): 84 %
- Recoil effect (Restricted arc if above 1.00): 0.80
Seaboat quality (Average = 1.00): 1.62

Hull form characteristics:
Hull has rise forward of midbreak,
a normal bow and a round stern
Block coefficient (normal/deep): 0.640 / 0.644
Length to Beam Ratio: 6.97 : 1
'Natural speed' for length: 29.15 kts
Power going to wave formation at top speed: 41 %
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): 56.7 %
- Above water (accommodation/working, high = better): 173.5 %
Waterplane Area: 74,842 Square feet or 6,953 Square metres
Displacement factor (Displacement / loading): 118 %
Structure weight / hull surface area: 231 lbs/sq ft or 1,129 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.98
- Longitudinal: 1.38
- 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
Excellent seaboat, comfortable, can fire her guns in the heaviest weather

How effective might this heavy protection fare against some of the heaviest naval guns in history (46 Cm, 16 inch Mark 7, ect)? Assuming the steel is of comparable quality to German or British plates of the same year, the ship is constructed with large amounts of welding, and the belt itself is inclined at about a 25 degree angle from vertical. Any other technical questions I can attempt to answer as best I can, or seek advice determining an answer. Thanks for any points you guys are able to make!

Depends on the range mostly as that's going to affect the angle of striking and the striking velocity as that will strongly determine the kinetic force and subsequent penetration

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I have to wonder if it's even possible to make such a thick piece of armour plate with the technology of the day

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As far as I know the thickest belt armour was 18in thick as a single plate and that was pushing metallurgy. It was also fairly brittle.
You could go for a double-belt if you had sufficient beam, a thinner external belt (12-15in) and a internal belt (4-6in) to stop splinters etc.
Not sure that would be totally effective however.

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If the 23" armoured belt could be cast and hardened at the same rate as the other armour equivalents (14-15") of the time. Then it would take something like the Japanese 20" dreamed for the Super-Yamato's. An armament of 10x16" on your ship is a waste of time as the most it would pierce is the 14-15" level of armour at best. If your opponents know you have 23" armour (bit hard to disguise) then they will probably place at least 18" or above on their ships to defeat your weapons. Since there is no WNT to curb your enemies building, the ships will just get bigger and bigger.

From what I read you seem to have no deck armour, just this "Box over machinery & magazines: 10.00" / 254 mm". I hope you have killed off General Billy Mitchell in your fictional world too.

As far as I'm aware the thickest armour ever used is the 26" plate on the front of Yamato's turrets, however, the important question is what are you attempting to stop? USN 16" Mark 8 AP rounds would penetrate up to 829mm at zero degrees and point-blank range, so if that's your spec it's still not enough - I make your effective thickness for a 584mm belt at 25 degrees about 680mm, combining angle of fall from Navweaps that gets you safe at ranges between 5,000 yards and 10,000 yards and up, more the 10,000 yard end of that range if I'm correct. At distance, though, from 40,000 yards and up, the shells start coming through your armoured deck because that's not thick enough.

Not to say that this is inherently a bad design, but I think that if you're after invulnerability to incoming fire that resultant ship won't really resemble a ship any more so much as a floating fort.

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A few comments,
1- This is for cruisers you should have a full deck for a battleship.
That 10" deck will be a little heavy! I would look at SDs and G3s decks

2 - 23" at 25deg is very strong especially once you add the effect from not fighting broadside to broadside to the 25deg.
Looking at the USN 16"/50 MK 2 (why MK7 in text for a 1925 ships with no WNT?) you only get 23.1" penetration (at 0 deg I assume) at 9000 yards, so 23" at 25 is probably not penetrable by the Mk 2. (http://www.navweaps.com/Weapons/WNUS_16-50_mk2.htm)

I think 23" and 10" only makes sense in a world with many 18" ships ? and 1925 is probably a bit to early and you would want to balance the design with more fire power than 10x 16" IMO ?

The USN tested a 28" armor plate from a Yamato against the 16"/50 mk 7 and it penned that 28" plate like butter. It's not the thickness of the armor that counts, its the quality of the steel its made of that counts.

Taking into account the input given here, I decided to switch from a armored box to a single layer full armor deck. I also changed the 23 inch belt, to instead having a 17 inch belt with a 4 inch thick belt behind it to catch spalling and splinters. I increased the height of the torpedo bulkhead to represent this weight. Increasing firepower to eight 18 inch guns proved too much weight for the ship, and offered very little practical improvement in throw weight. Eight 17.5 inch guns proved to be viable, though I'm not entirely sold on the merit of trading the more numerous 16 inch guns for fewer 17.5s. Speed had to be reduced to 22 knots as well, but not a large loss for an already sluggish ship. This is how it looks now:

Tannhauser, Regia Nautica Battleship laid down 1925

Displacement:
63,806 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:
10 - 16.00" / 406 mm 45.0 cal guns - 2,365.46lbs / 1,072.96kg shells, 90 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 26,982 lbs / 12,239 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:
0.00" / 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: 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:
£15.776 million / $63.103 million

Distribution of weights at normal displacement:
Armament: 4,226 tons, 5.9 %
Armour: 31,785 tons, 44.4 %
- Belts: 9,605 tons, 13.4 %
- Torpedo bulkhead: 4,973 tons, 6.9 %
- Armament: 5,774 tons, 8.1 %
- Armour Deck: 10,616 tons, 14.8 %
- Conning Tower: 817 tons, 1.1 %
Machinery: 2,141 tons, 3.0 %
Hull, fittings & equipment: 23,195 tons, 32.4 %
Fuel, ammunition & stores: 7,815 tons, 10.9 %
Miscellaneous weights: 2,460 tons, 3.4 %
- Hull below water: 500 tons
- Bulge void weights: 600 tons
- Hull above water: 300 tons
- On freeboard deck: 110 tons
- Above deck: 950 tons

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
167,332 lbs / 75,901 Kg = 81.7 x 16.0 " / 406 mm shells or 50.0 torpedoes
Stability (Unstable if below 1.00): 1.18
Metacentric height 8.7 ft / 2.7 m
Roll period: 18.2 seconds
Steadiness - As gun platform (Average = 50 %): 86 %
- Recoil effect (Restricted arc if above 1.00): 0.64
Seaboat quality (Average = 1.00): 1.65

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): 49.9 %
- Above water (accommodation/working, high = better): 170.3 %
Waterplane Area: 76,133 Square feet or 7,073 Square metres
Displacement factor (Displacement / loading): 119 %
Structure weight / hull surface area: 228 lbs/sq ft or 1,114 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.97
- Longitudinal: 1.39
- 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
Excellent seaboat, comfortable, can fire her guns in the heaviest weather

I just don't see why you are building such a large ship ?

- Its massively larger (75 v 47 Kt full load) than a South Dakota 1920 and what does this give you ? Much thicker protection but 2 less guns.

- Your protection only makes sense if you intend to be hit by much more powerful weapons than 16" guns (18"+) and in that case you will be fighting ships that are likely protected on balanced lines (due to no treaty's) against their own 18+ guns and your 16" will not be sufficient.

- Ship speed of 22Kn in a no WNT world post LD in 25 is slow IMO, forgetting the G3s all the SD and IJN ships are faster 23-26-29Kn range.

- You have 2 x Twin mounts on centreline, evenly spread and 2 x Twin mounts on centreline, evenly spread but 10 guns ? are you missing a turret ?

- Light/heavy AAA is very heavy for 1925 ?

- Deck of 9.2" is still massively strong N3 only had 8"-6" and its a full 18" battleship (just look at your % Armour: 31,785 tons, 44.4 % )

-Seaboat quality (Average = 1.00): 1.65 is very high 1.5 is excellent why so high ?

I would suggest cutting it massive and save loads of cash a 22Kn No treaty Battleship with 16" guns and protected for 18" should be build able on less than 50,000t full load (add protection to Nelson or South Dakota or cut gun size from N3)