SDN World 3 Ship Design Thread

[Steve]

I was in the middle of designing a proposed 1926 Large Cruiser, the Artemis, that would be almost 35,000 tons due to upping the guns from the completely ahistoric 10"/51 caliber to 12"/50 (based somewhat on the historic 12"/50 Mark 8 used on Alaska, though I wasn't sure if I could justify similar performance), raising the speed to near the very limit of the era's engine plants (I was told that 52,000hp/shaft was max limit, anything higher is impossible in the 1920s), but reducing the armor belt max thickness from 13" to 10-11.5" to keep the weight down. Also added 2" deck armor to the quarterdeck for steering gear protection. Also considered removing the light TDS Lightning enjoys (2.5" bulkheads) to save weight, reduce belt length, etc., since the likelihood of facing torpedo attack for now is light (and the ship will break 34 knots anyway).

[Norseman]

I'm also not sure how thick my torpedo bulkheads should be, given that my Large Cruiser is also likely to move at around 34 knots amd cruise at 20, do I really need torpedo protection at that point?

[Ma Deuce]

The following is a design study for what a large cruiser might look like if I built one. I don't have any immediate plans to build such a Large Cruiser for the foreseeable future as they don't fit my navy's doctrine (though if everyone else keeps building supercruisers, it may force my hand eventually), but if I did this is probably what it would look like. Unfortunately, the design is compromised in several areas, but it was intended to be cheap, and at less that 25kt, it can be built without taking up a slip, and can be completed in 2 years according to the game's rules, while still being able to overwhelm 8" gunned cruisers. Realistically, one expensive aspect of construction would likely be the inclined, internal belt which is also tapered; the number presented in Springsharp here is supposed to represent a belt that is 24 cm at the top, and 12 cm at the bottom. The use of two types of turrets might also be a cost issue, but then again the guns themselves are intended to be "donated" by retired dreadnoughts, so that should take a big chunk out of costs and construction times.

CB-1927, Conceptual Large Cruiser laid down 1926 (Engine 1927)

Displacement:
23,853 t light; 24,999 t standard; 28,068 t normal; 30,523 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(820.80 ft / 807.09 ft) x 78.74 ft (Bulges 86.94 ft) x (27.56 / 29.50 ft)
(250.18 m / 246.00 m) x 24.00 m (Bulges 26.50 m) x (8.40 / 8.99 m)

Armament:
8 - 12.01" / 305 mm 45.0 cal guns - 992.08lbs / 450.00kg shells, 100 per gun
Breech loading guns in turret on barbette mounts, 1926 Model
1 x 2-gun mount on centreline forward
1 raised mount - superfiring
2 x 3-gun mounts on centreline ends, evenly spread
8 - 5.51" / 140 mm 50.0 cal guns - 88.18lbs / 40.00kg shells, 240 per gun
Quick firing guns in deck and hoist mounts, 1926 Model
4 x Twin mounts on sides, evenly spread
8 - 3.94" / 100.0 mm 50.0 cal guns - 30.86lbs / 14.00kg shells, 360 per gun
Dual purpose guns in deck and hoist mounts, 1926 Model
4 x Twin mounts on centreline, evenly spread
4 raised mounts
Weight of broadside 8,889 lbs / 4,032 kg

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 7.09" / 180 mm 508.53 ft / 155.00 m 15.09 ft / 4.60 m
Ends: Unarmoured
Main Belt covers 97 % of normal length
Main Belt inclined 18.00 degrees (positive = in)

- Torpedo Bulkhead - Strengthened structural bulkheads:
1.57" / 40 mm 508.53 ft / 155.00 m 24.44 ft / 7.45 m
Beam between torpedo bulkheads 70.21 ft / 21.40 m

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 10.2" / 260 mm 4.72" / 120 mm 9.45" / 240 mm
2nd: 1.97" / 50 mm 1.57" / 40 mm 1.57" / 40 mm
3rd: 1.57" / 40 mm 0.98" / 25 mm 1.57" / 40 mm

- Armoured deck - multiple decks:
For and Aft decks: 5.12" / 130 mm
Forecastle: 0.00" / 0 mm Quarter deck: 2.52" / 64 mm

- Conning towers: Forward 9.45" / 240 mm, Aft 0.00" / 0 mm

Machinery:
Oil fired boilers, steam turbines,
Electric motors, 4 shafts, 134,049 shp / 100,000 Kw = 32.48 kts
Range 10,142nm at 16.00 kts
Bunker at max displacement = 5,524 tons

Complement:
1,083 - 1,409

Cost:
£7.537 million / $30.148 million

Distribution of weights at normal displacement:
Armament: 1,762 tons, 6.3 %
- Guns: 1,762 tons, 6.3 %
Armour: 8,254 tons, 29.4 %
- Belts: 2,243 tons, 8.0 %
- Torpedo bulkhead: 724 tons, 2.6 %
- Armament: 1,526 tons, 5.4 %
- Armour Deck: 3,572 tons, 12.7 %
- Conning Tower: 188 tons, 0.7 %
Machinery: 4,231 tons, 15.1 %
Hull, fittings & equipment: 9,531 tons, 34.0 %
Fuel, ammunition & stores: 4,215 tons, 15.0 %
Miscellaneous weights: 75 tons, 0.3 %
- On freeboard deck: 75 tons

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
38,306 lbs / 17,375 Kg = 44.2 x 12.0 " / 305 mm shells or 5.6 torpedoes
Stability (Unstable if below 1.00): 1.10
Metacentric height 4.2 ft / 1.3 m
Roll period: 17.9 seconds
Steadiness - As gun platform (Average = 50 %): 70 %
- Recoil effect (Restricted arc if above 1.00): 0.67
Seaboat quality (Average = 1.00): 1.20

Hull form characteristics:
Hull has a flush deck,
a normal bow and large transom stern
Block coefficient (normal/deep): 0.508 / 0.516
Length to Beam Ratio: 9.28 : 1
'Natural speed' for length: 32.58 kts
Power going to wave formation at top speed: 50 %
Trim (Max stability = 0, Max steadiness = 100): 58
Bow angle (Positive = bow angles forward): 20.00 degrees
Stern overhang: 1.77 ft / 0.54 m
Freeboard (% = length of deck as a percentage of waterline length):
Fore end, Aft end
- Forecastle: 22.00 %, 32.81 ft / 10.00 m, 23.46 ft / 7.15 m
- Forward deck: 21.00 %, 23.46 ft / 7.15 m, 20.34 ft / 6.20 m
- Aft deck: 41.00 %, 20.34 ft / 6.20 m, 20.34 ft / 6.20 m
- Quarter deck: 16.00 %, 20.34 ft / 6.20 m, 20.34 ft / 6.20 m
- Average freeboard: 22.18 ft / 6.76 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 83.3 %
- Above water (accommodation/working, high = better): 162.8 %
Waterplane Area: 44,363 Square feet or 4,121 Square metres
Displacement factor (Displacement / loading): 117 %
Structure weight / hull surface area: 162 lbs/sq ft or 792 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.98
- Longitudinal: 1.09
- Overall: 1.00
Excellent machinery, storage, compartmentation space
Excellent accommodation and workspace room
Ship has slow, easy roll, a good, steady gun platform
Good seaboat, rides out heavy weather easily

Facilities for 3 aircraft

[CmdrWilkens]

I'm also not sure how thick my torpedo bulkheads should be, given that my Large Cruiser is also likely to move at around 34 knots amd cruise at 20, do I really need torpedo protection at that point?

Well a) Torpedoes even in the 20s can run at 44 kts+
b) Sub launches as you refuel/cruise around can still catch you off guard
c) Maneuverability rather than pure speed is a better defense, the ability to corkscrew saved the Maryland a couple times IIRC

[Sea Skimmer]

I'm also not sure how thick my torpedo bulkheads should be, given that my Large Cruiser is also likely to move at around 34 knots amd cruise at 20, do I really need torpedo protection at that point?

It can go either way. The USN went as big as Alaska with no torpedo protection on the grounds that this plus centerline bulkheads to exploit its protection would lead to too much instability on the restricted beam. It was better to take more flooding, but flood evenly across the beam with no bulkheads at all. A ship which will sink bodily will take longer to sink, and can survive more tonnage of flooding before going down. However it also meant taking more tons of floodwater from each hit.

Just about all other cruiser killers, and even some earlier concepts for the program that became Alaska had a TDS meanwhile. However rarely did they have one that was going to be fully effective. What it would really just do is localize damage, the centerline bulkhead in the machinery spaces would mean that limited damage through the TDS would only flood halfway across the beam. This would save some machinery, but then you’d need major counter flooding to balance it back out.

Now the magazines of each turret cannot be divided, so any breach of the TDS (which is nearly certain on anything with much less then 100 feet of beam to play with) means loss of magazine space and the turret above. A ineffective TDS still has some value in reducing the probability of an explosion though. But normally the floodwater would put out magazine fires anyway. So explosions were not a huge problem unless you are HMS Braham and take three torpedo hits right next to each other.

So a TDS has some value, but its also a liability on replacement restricted ships. Japan and the British went as small as heavy cruisers with limited TDSs, but both nations also produced ships which were in general, very highly prone to sinking by capsizing. In contrast the Iowa class had a full TDS, but even on that size it was still difficult to find sufficient volume for it around the turrets, and A turret was quite vulnerable. Narrow ends are a serious problem on a fast warship, even if you have plenty of beam amidships.

[Fingolfin_Noldor]

So fed up as I was with the huge bulge, that probably would make the ship look silly, I decided to go with a slower ship, a much much smaller bulge, but with much higher survivability. The USN made do with Standard ships, so I will go with their line of thinking after all.

Justinian, Byzantine Empire Battleship laid down 1926

Displacement:
52,181 t light; 55,024 t standard; 58,732 t normal; 61,699 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(818.12 ft / 800.52 ft) x 108.27 ft (Bulges 114.83 ft) x (39.37 / 40.99 ft)
(249.36 m / 244.00 m) x 33.00 m (Bulges 35.00 m) x (12.00 / 12.49 m)

Armament:
9 - 18.00" / 457 mm 45.0 cal guns - 3,000.01lbs / 1,360.78kg shells, 90 per gun
Breech loading guns in turret on barbette mounts, 1926 Model
3 x 3-gun mounts on centreline ends, majority forward
1 raised mount - superfiring
16 - 5.00" / 127 mm 38.0 cal guns - 59.33lbs / 26.91kg shells, 400 per gun
Dual purpose guns in deck and hoist mounts, 1926 Model
8 x Twin mounts on sides, evenly spread
4 raised mounts
40 - 1.57" / 40.0 mm 56.0 cal guns - 2.12lbs / 0.96kg shells, 2,000 per gun
Anti-air guns in deck mounts, 1926 Model
10 x Quad mounts on side ends, majority aft
4 raised mounts - superfiring
40 - 0.79" / 20.0 mm 70.0 cal guns - 0.26lbs / 0.12kg shells, 2,000 per gun
Anti-air guns in deck mounts, 1926 Model
10 x Quad mounts on side ends, majority aft
16 - 0.50" / 12.7 mm 12.0 cal guns - 0.04lbs / 0.02kg shells, 4,000 per gun
Anti-air guns in deck mounts, 1926 Model
16 x 4-gun mounts on centreline, aft deck forward
Weight of broadside 28,045 lbs / 12,721 kg

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 16.0" / 406 mm 410.00 ft / 124.97 m 20.00 ft / 6.10 m
Ends: Unarmoured
Main Belt covers 79 % of normal length
Main Belt inclined 19.00 degrees (positive = in)

- Torpedo Bulkhead - Additional damage containing bulkheads:
4.00" / 102 mm 430.00 ft / 131.06 m 40.00 ft / 12.19 m
Beam between torpedo bulkheads 74.00 ft / 22.56 m

- Hull Bulges:
1.00" / 25 mm 430.00 ft / 131.06 m 40.00 ft / 12.19 m

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 26.0" / 660 mm 12.0" / 305 mm 19.0" / 483 mm
2nd: 3.00" / 76 mm 2.00" / 51 mm 3.00" / 76 mm
3rd: 0.50" / 13 mm - -
4th: 0.50" / 13 mm - -
5th: 0.50" / 13 mm - -

- Armoured deck - multiple decks:
For and Aft decks: 8.00" / 203 mm
Forecastle: 3.00" / 76 mm Quarter deck: 3.50" / 89 mm

- Conning towers: Forward 15.00" / 381 mm, Aft 6.00" / 152 mm

Machinery:
Oil fired boilers, steam turbines,
Electric motors, 4 shafts, 71,447 shp / 53,299 Kw = 24.00 kts
Range 10,000nm at 14.00 kts
Bunker at max displacement = 6,675 tons

Complement:
1,886 - 2,452

Cost:
£16.228 million / $64.913 million

Distribution of weights at normal displacement:
Armament: 5,179 tons, 8.8 %
- Guns: 5,179 tons, 8.8 %
Armour: 24,302 tons, 41.4 %
- Belts: 5,917 tons, 10.1 %
- Torpedo bulkhead: 2,546 tons, 4.3 %
- Bulges: 636 tons, 1.1 %
- Armament: 6,016 tons, 10.2 %
- Armour Deck: 8,503 tons, 14.5 %
- Conning Towers: 684 tons, 1.2 %
Machinery: 2,287 tons, 3.9 %
Hull, fittings & equipment: 20,282 tons, 34.5 %
Fuel, ammunition & stores: 6,551 tons, 11.2 %
Miscellaneous weights: 130 tons, 0.2 %
- Hull above water: 30 tons
- On freeboard deck: 100 tons

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
97,775 lbs / 44,350 Kg = 33.5 x 18.0 " / 457 mm shells or 20.0 torpedoes
Stability (Unstable if below 1.00): 1.06
Metacentric height 6.3 ft / 1.9 m
Roll period: 19.2 seconds
Steadiness - As gun platform (Average = 50 %): 73 %
- Recoil effect (Restricted arc if above 1.00): 0.88
Seaboat quality (Average = 1.00): 1.51

Hull form characteristics:
Hull has a flush deck,
an extended bulbous bow and large transom stern
Block coefficient (normal/deep): 0.568 / 0.573
Length to Beam Ratio: 6.97 : 1
'Natural speed' for length: 33.00 kts
Power going to wave formation at top speed: 41 %
Trim (Max stability = 0, Max steadiness = 100): 48
Bow angle (Positive = bow angles forward): 25.00 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 %, 37.73 ft / 11.50 m, 26.25 ft / 8.00 m
- Forward deck: 30.00 %, 26.25 ft / 8.00 m, 21.98 ft / 6.70 m
- Aft deck: 35.00 %, 21.98 ft / 6.70 m, 22.31 ft / 6.80 m
- Quarter deck: 15.00 %, 22.31 ft / 6.80 m, 28.54 ft / 8.70 m
- Average freeboard: 24.97 ft / 7.61 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 77.3 %
- Above water (accommodation/working, high = better): 147.5 %
Waterplane Area: 64,070 Square feet or 5,952 Square metres
Displacement factor (Displacement / loading): 110 %
Structure weight / hull surface area: 239 lbs/sq ft or 1,169 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0.94
- Longitudinal: 1.60
- Overall: 1.00
Excellent machinery, storage, compartmentation space
Excellent accommodation and workspace room
Ship has slow, easy roll, a good, steady gun platform
Excellent seaboat, comfortable, can fire her guns in the heaviest weather

[Doomriser]

The coastal submarines need to travel at higher speeds in order to remain competitive with surface ships. Current submarines in most navies have a surface speed of 17-20 kts (or even less), and a submerged speed usually of 7-11 kts.

Is there anything that could be done to design a submarine that can reliably reach higher surface and submerged speeds? I can imagine building a larger submarine simply to accomodate a larger engine and fuel stores (and batteries.)

Some streamlined or underwater-performance designs are in existence (R-class and the X-1 submarine cruisers). But even then, there are limitations.

Is there anything that can be done to improve the ability of submarines to intercept enemy capital ships (aside from improvements in detection and communication)?

[CmdrWilkens]

The coastal submarines need to travel at higher speeds in order to remain competitive with surface ships. Current submarines in most navies have a surface speed of 17-20 kts (or even less), and a submerged speed usually of 7-11 kts.

Is there anything that could be done to design a submarine that can reliably reach higher surface and submerged speeds? I can imagine building a larger submarine simply to accomodate a larger engine and fuel stores (and batteries.)

Some streamlined or underwater-performance designs are in existence (R-class and the X-1 submarine cruisers). But even then, there are limitations.

Is there anything that can be done to improve the ability of submarines to intercept enemy capital ships (aside from improvements in detection and communication)?

In this time period? Not really. Subs are area and SLOC denial weapons if you look at both world wars the vast majority of sinkings were commercial in nature because those ships run slower, don't maneuver out of torpedoes path well and don't have TDS built in to their hulls. Actual capital ships being sunk by Submarines was quite rare percentage wise. In this time period with ASDIC (or a home grown equivalent) probably available to any NF 4 or 5 nation and shore based HF/DF probably popping up here and there subs sneaking up and attacking ships in the battle line probably isn't going to happen.

One of the reasons why things were getting retro'd left and right in the Mexican-Colombian war is that neither of us (Ryan or I) realized how largely ineffective cruiser subs were in the 20s.

[Ryan Thunder]

I have to ask; were Surcouf's problems a result of a bad design or were those problems endemic to the very concept of the cruiser sub itself?

[Sea Skimmer]

One of the reasons why things were getting retro'd left and right in the Mexican-Colombian war is that neither of us (Ryan or I) realized how largely ineffective cruiser subs were in the 20s.

Who came to that conclusion? The main reason cruiser subs died out was lack of budgets for normal warships, and aircraft development. The former is a joke here, the latter doesn't really matter yet because as long as planes only go 150mph the high diving time of large submarines wasn’t a serious liability. Also in real life the major powers able to invest in cruiser subs lacked any worthwhile targets. Neither the US nor UK saw each others commerce as a serious target, the French also realized they had no targets, and Japan never emphasized commerce destruction ever. Italy had narrow seas to play in, and the Germans meanwhile actually did want to build new cruiser subs in the late 1930s but Hitler’s mass mobilization left little margin for them. After all the Nazis had fewer subs then the British did in 1939. This issue is far less relevant in a hyper industrialized world in which numerous powers spread all over all of which must have large merchant fleets open to attack.

[Doomriser]

It's my understanding that the innovation in submarine hull design between WWI and WWII was somewhat limited. The most significant advances might have been in engines and battery (as well as "add-on" features such as detection and communications equipment, AA, and armament- and computer). The actual hulls were like improved WWI hulls.

The two most successful German U-boat of WWII designs were based on updated WWI designs (the Type UBIII and the Mittel-U). Germany actually suffered a gap in its submarine construction because of Versailles, and had to spend years clandestinely recouping its WWI submarine experience in the 1920s. It relied on secret construction in other countries just to maintain a cadre of shipbuilders to expand from, and I think Germany's first post-Versailles designs may have been inferior to or little better than many WWI subs.

So, it appeared to me that, rather than continuous and radical innovation from WWI to WWII, Germany experienced a "lost tech" situation, regained the ability to build subs, and incrementally improved on its WWI designs. The major innovation came in tactics, facilitated by better communications and such.

Britain did not pursue certain interesting avenues of research post-war, such as its interesting R-class design. Moreover, it's cruiser subs suffered from unfortunate accidents, that prevented full testing of their capabilities in a budget-conscious climate.

Japan had to start from less, but pursued its own submarine avenues and became world-class by WWII.

The U.S., too, started from a weaker position vis-a-vis submarines than either Germany or Britain, but caught up eventually.

So it seems to me that if certain German and British designs had been pursued, improved, and fully-funded, rather than scrapped, forgotten, or made illegal, it might have been possible to have better subs within a given 1920s technological environment.

I think we might be letting the experience of Versailles and Britain's limited enthusiasm for subs colour our interpretation of how subs would be designed in this world.

Ryan, regarding cruiser subs, I think Surcouf was one of the more successful cruiser subs. After all, it wasn't capsized in a collision like so many were! It had a chance to become operational and demonstrate its capabilities. I think the real problem with cruiser subs was that the powers-that-be tried to design them as submersible gun cruisers, so as to fit into the perceived "Cruiser rules" or "prize rules" of anti-shipping warfare.* The large guns on the subs challenged their seaworthiness, dive times, machine complexity, and other factors.

That is why the Bolivarian Union and a couple of other countries designed cruiser subs without large guns. They retain the large hull (or even large underwater-streamlined hull) and long range, but emphasize torpedo armament, and dispense with the big guns. Plus, there's more room for machinery without all of those 5+ inch guns and loading mechanisms.

The X-1 and R-class submarines demonstrated the possibility of developing underwater-streamlined hulls in the 1920s. Naval doctrine at the time mitigated against undersea merchant raiding for political reasons. If naval doctrines of the 1920s saw unrestricted submarine warfare as a possibility, it is conceivable that submarine designs could have given greater emphasis towards underwater performance. As it was, the lack of fast anti-submarine aircraft or radar appeared to enable fast surface raiding by submarines. Add large guns to this equation and you have an unwieldy cruiser submarine.

*True "submersible cruisers" probably didn't become practical until the advent of submarine-launched missiles.

[Thanas]

Actually, the VII and the IX classes profited from new welding techniques as well, which IIRC were not invented until the 30s.

[Sea Skimmer]

I have to ask; were Surcouf's problems a result of a bad design or were those problems endemic to the very concept of the cruiser sub itself?

Her most boat specific problem was that it took two and half minutes to ready the guns for action, which was quite excessive and entirely the result of a lack of refinement. The British were able to make a 12in mounting earlier that could be ready to fire in 30 seconds. Other then that the main downside was just that she was as big and expensive as two fleet submarines and needed as many men. Meanwhile France had nothing for her to attack.

However quite a bit of economy was expected in return by being able to sink even armed merchant ships with gunfire. Torpedoes were and are very expensive, the most expensive pieces of ammo a military has other then its various nuclear weapons systems (you can buy a half dozen Tomahawks for the price of a Mk48). It also took 30 minutes to assemble the aircraft for launch; this once more was mainly lack of refinement. The Japanese fielded a large number of catapult submarines with had aircraft they could assemble and launch in about half that time.

Diving time was 2 minutes, which is could have been improved upon but not dramatically. It isn’t great but against a 100-150mph patrol aircraft (and in 1925 a patrol plane might cruise at well under 100mph) that means spotting the enemy at about five miles suffices. This is the inherent problem that killed big 3,500 ton cruisers off in real life, because once planes exceeded 200-250mph you couldn’t dive in time with only visual warning to work from. But those kinds of speeds are ten years in the future in 1925 and as we see in real life, it took a long time to get complete air coverage even on the North Atlantic. Covering say, the Pacific would be absurdly demanding. You also have the advantage that once you do dive, no one has sonar. That means the bigger size and lesser agility of large subs is no serious liability.

Also a cruiser need not be a 3,500 ton monster with a fixed 8in mount. On 2,000 tons or less, not that much larger then a big fleet submarine already reached, you could easily have two 5.5in or 6in guns in deck mounts, and 2,500 tons would allow two or three such guns in enclosed mountings. A twin forward and a single aft most likely. Japan built a 2,100 ton cruiser sub with a twin 5.5in mount and light armor on 2,135 tons in 1926 for example. Range was no less then 24,400nm.
Japan never made the shift from low-medium speed to high speed diesels either as a note (this is an engine RPM matter) which meant her submarine designs never really progressed past the 1920s. So anything you see Japan having built in WW2 could probably be built in the 1920s, while the same is not true of other nations submarines.

Of course, you could also go crazy and build the USN’s design for a 25,000 ton steam powered underwater battlecruiser with as much as six inches of armor, a torpedo defense system. and either four 12in or eight 8in guns along with AA weapons. Plus five separate pressure hulls, enabling the boilers to be isolated from the crew spaces and thus avoiding the absurd temperature problems that plagued the British K class. At this point even if an aircraft did attack you, it would need to drop rather large weapons to cause any damage.... But its also half the cost of a battleship.

As a last note, the sub cruiser really didn't die out until after WW2 either. The USN was in fact busily converting a number (seven IIRC) of Gatos into submarine cruisers when WW2 ended by adding a second 5in gun, along with an actual vertical stabilizer and gunfire control computer. The reason for this being that Japan had few big merchant ships left, and yet was able to move strategically significant tonnages of material in shallow draught junks and sampans, many of which mounted enough armament to be a serious threat to a sub with only a single gun firing by eye.

[CmdrWilkens]

Diving time was 2 minutes, which is could have been improved upon but not dramatically. It isn’t great but against a 100-150mph patrol aircraft (and in 1925 a patrol plane might cruise at well under 100mph) that means spotting the enemy at about five miles suffices. This is the inherent problem that killed big 3,500 ton cruisers off in real life, because once planes exceeded 200-250mph you couldn’t dive in time with only visual warning to work from. But those kinds of speeds are ten years in the future in 1925 and as we see in real life, it took a long time to get complete air coverage even on the North Atlantic. Covering say, the Pacific would be absurdly demanding. You also have the advantage that once you do dive, no one has sonar. That means the bigger size and lesser agility of large subs is no serious liability.

Just as a bit of a toss out, ASDIC would be available since it was in development as early as 1916 and deployed by the early 1920s with both the US and British having operational systems (though the US took longer to go operational) in that time period. I would think it suffice to say that an NF 5 would definitely have sonar and an NF 4 MIGHT have sonar in this time period (certainly an NF 4 would have a developmental version).

At the same time the other tidbit worth noting for Ryan's sake is that if his subs are going to operate in the Caribbean or Gulf of Mexico those are far more confined waters that could more easily be given sufficient air cover. Pacific and open Atlantic operations would suffer from the same historical difficulties but the more confined waters of the Caribbean would pose much less of a challenge.

[Ryan Thunder]

Of course, you could also go crazy and build the USN’s design for a 25,000 ton steam powered underwater battlecruiser with as much as six inches of armor, a torpedo defense system. and either four 12in or eight 8in guns along with AA weapons. Plus five separate pressure hulls, enabling the boilers to be isolated from the crew spaces and thus avoiding the absurd temperature problems that plagued the British K class. At this point even if an aircraft did attack you, it would need to drop rather large weapons to cause any damage.... But its also half the cost of a battleship.

Where could I read more about this?

[Sea Skimmer]

Just as a bit of a toss out, ASDIC would be available since it was in development as early as 1916 and deployed by the early 1920s with both the US and British having operational systems (though the US took longer to go operational) in that time period. I would think it suffice to say that an NF 5 would definitely have sonar and an NF 4 MIGHT have sonar in this time period (certainly an NF 4 would have a developmental version).

Yeah, the very early ASDIC and sonar sets worked so poorly you’d have to seriously question using it at all in many tactical situations. I tend to discount it as having a serious effect. The speed limit was no more then 3-4 knots, and at that point hydrophones had nearly as long a range while searching a wider area and not constantly alerting the submarine and begging it to torpedo you as you creep along. Decent sonar that works the way you’d want it to work didn’t appear until the early 1930s.

Where could I read more about this?

Friedman’s US Submarines Through 1945 An Illustrated Design History. It covers a number of giant submarine cruiser concepts in the mid 1920s, as well as everything else the US Navy worked on or built. Since it’s a moderately expensive book and mostly on normal submarines I suggest you try the library system. Lots of US libraries have this series, and I can’t imagine Canukistan is devoid of them.

The image below isn’t the format you’d see in the book, but it shows one of the smaller concepts the US Navy was able to crack smoke its way into drawing which I happened to have handy. No steam power or armor but she does have three pressure hulls and a couple aircraft to spot for her 8in main battery.


history.navy has a couple more, though not of the really big heavily protected 25,000 tonner

http://www.history.navy.mil/photos/imag ... 84164c.htm
http://www.history.navy.mil/photos/imag ... 84165c.htm
http://www.history.navy.mil/photos/imag ... 84166c.htm

[CmdrWilkens]

Most of Friedman's works seem to be at least partially available on Google Books. Sections are missing often but, as a for instance, most of his work on US Battleships is available including most of the "Standard" classes, the South Dakota design work which never made it in to production and the North Carolina class.

[Sea Skimmer]

Not a bad idea; I looked into that but it seems its only one page partly concerning cruiser submarines that they have online. It does mention some of the larger concepts in that one page. The full book has a couple more pages on large cruisers, then the detailed evolution of how the USN got Nautilus with her 2 x 6in guns.

[CmdrWilkens]

Not a bad idea; I looked into that but it seems its only one page partly concerning cruiser submarines that they have online. It does mention some of the larger concepts in that one page. The full book has a couple more pages on large cruisers, then the detailed evolution of how the USN got Nautilus with her 2 x 6in guns.

Really, I went and found page 170 onwards to be available but that might be because I jumped straight there. I think the limited preview function only allows you to read a certain number of pages per session before kicking you back out but I could definitely see many of the 1920-22 proposals.

[Ryan Thunder]

The image below isn’t the format you’d see in the book, but it shows one of the smaller concepts the US Navy was able to crack smoke its way into drawing which I happened to have handy.

So what exactly is the problem with them in this era? Cost?

[Raesene]

design for a light cruiser for fleet escort. should be able to prevent eneny destroyers from closing in and eliminate the enemy destroyer screen to give the own destroyers the chance for a torpedo attack.

****************

Penelope, Tuscan Kingdom cruiser concept for 1927

Displacement:
9.553 t light; 9.901 t standard; 11.149 t normal; 12.148 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
(573,86 ft / 557,74 ft) x 65,62 ft x (21,33 / 22,73 ft)
(174,91 m / 170,00 m) x 20,00 m x (6,50 / 6,93 m)

Armament:
12 - 5,51" / 140 mm 45,0 cal guns - 88,18lbs / 40,00kg shells, 150 per gun
Breech loading guns in turret on barbette mounts, 1925 Model
3 x 4-gun mounts on centreline ends, evenly spread
8 - 2,99" / 76,0 mm 45,0 cal guns - 11,02lbs / 5,00kg shells, 150 per gun
Anti-air guns in deck mounts, 1923 Model
8 x Single mounts on sides amidships
12 - 1,57" / 40,0 mm 45,0 cal guns - 1,97lbs / 0,89kg shells, 300 per gun
Anti-air guns in deck mounts, 1923 Model
12 x Single mounts on sides amidships
12 raised mounts
Weight of broadside 1.170 lbs / 531 kg
12 - 23,6" / 600 mm, 26,25 ft / 8,00 m torpedoes - 2,112 t each, 25,346 t total
In 4 sets of deck mounted side rotating tubes

Armour:
- Belts: Width (max) Length (avg) Height (avg)
Main: 2,99" / 76 mm 362,53 ft / 110,50 m 9,84 ft / 3,00 m
Ends: Unarmoured
Main Belt covers 100% of normal length
Main belt does not fully cover magazines and engineering spaces

- Torpedo Bulkhead:
1,18" / 30 mm 362,53 ft / 110,50 m 17,49 ft / 5,33 m

- Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
Main: 2,99" / 76 mm 1,97" / 50 mm 1,97" / 50 mm
2nd: 1,18" / 30 mm 0,79" / 20 mm -
3rd: 0,79" / 20 mm - -

- Armoured deck - multiple decks: 0,98" / 25 mm For and Aft decks
Forecastle: 0,98" / 25 mm Quarter deck: 0,98" / 25 mm

Machinery:
Oil fired boilers, steam turbines,
Geared drive, 4 shafts, 111.121 shp / 82.897 Kw = 34,00 kts
Range 10.000nm at 14,00 kts
Bunker at max displacement = 2.247 tons

Complement:
542 - 705

Cost:
£3,376 million / $13,504 million

Distribution of weights at normal displacement:
Armament: 343 tons, 3,1%
- Guns: 318 tons, 2,9%
- Torpedoes: 25 tons, 0,2%
Armour: 1.385 tons, 12,4%
- Belts: 446 tons, 4,0%
- Torpedo bulkhead: 277 tons, 2,5%
- Armament: 203 tons, 1,8%
- Armour Deck: 458 tons, 4,1%
Machinery: 3.508 tons, 31,5%
Hull, fittings & equipment: 4.218 tons, 37,8%
Fuel, ammunition & stores: 1.596 tons, 14,3%
Miscellaneous weights: 100 tons, 0,9%
- Hull above water: 25 tons
- On freeboard deck: 50 tons
- Above deck: 25 tons

Overall survivability and seakeeping ability:
Survivability (Non-critical penetrating hits needed to sink ship):
12.393 lbs / 5.621 Kg = 148,0 x 5,5 " / 140 mm shells or 1,8 torpedoes
Stability (Unstable if below 1.00): 1,24
Metacentric height 3,9 ft / 1,2 m
Roll period: 13,9 seconds
Steadiness - As gun platform (Average = 50 %): 63 %
- Recoil effect (Restricted arc if above 1.00): 0,22
Seaboat quality (Average = 1.00): 1,05

Hull form characteristics:
Hull has a flush deck,
a normal bow and small transom stern
Block coefficient (normal/deep): 0,500 / 0,511
Length to Beam Ratio: 8,50 : 1
'Natural speed' for length: 25,53 kts
Power going to wave formation at top speed: 63 %
Trim (Max stability = 0, Max steadiness = 100): 60
Bow angle (Positive = bow angles forward): 20,00 degrees
Stern overhang: 6,56 ft / 2,00 m
Freeboard (% = length of deck as a percentage of waterline length):
Fore end, Aft end
- Forecastle: 20,00%, 26,25 ft / 8,00 m, 22,97 ft / 7,00 m
- Forward deck: 30,00%, 22,97 ft / 7,00 m, 22,97 ft / 7,00 m
- Aft deck: 35,00%, 22,97 ft / 7,00 m, 22,97 ft / 7,00 m
- Quarter deck: 15,00%, 22,97 ft / 7,00 m, 22,97 ft / 7,00 m
- Average freeboard: 23,23 ft / 7,08 m

Ship space, strength and comments:
Space - Hull below water (magazines/engines, low = better): 160,0%
- Above water (accommodation/working, high = better): 196,1%
Waterplane Area: 24.968 Square feet or 2.320 Square metres
Displacement factor (Displacement / loading): 118%
Structure weight / hull surface area: 109 lbs/sq ft or 530 Kg/sq metre
Hull strength (Relative):
- Cross-sectional: 0,98
- Longitudinal: 2,11
- Overall: 1,06
Hull space for machinery, storage, compartmentation is cramped
Room for accommodation and workspaces is excellent

**************
misc. space is for aircraft and their equipment, the second torpedo set are reloads.
the torpedo bulkhead makes it a cramped design, but I'd like the ship to be able to limp away after a torpedo hit instead of exploding like a destroyer - it's too expensive to be expendable...

[Fingolfin_Noldor]

Gun is kinda small for killing destroyers...

[Raesene]

Gun is kinda small for killing destroyers...

If they stop out of torpedo range because they are otherwise occupied I'm happy

A 14 cm with a 40 kg shell is a bit smaller than the usual 6'' guns (the 6'' of the Nelson-class fired shells of about 45 kg), the 5.25'' of King George V and the Didos' used 36kg shells. The 5.5'' of HMS Hood used 37kg shells.
These guns will be easier to load because of the lower shell weight, increasing the rate of fire (at least that was my thought).

[Fingolfin_Noldor]

Gun is kinda small for killing destroyers...

If they stop out of torpedo range because they are otherwise occupied I'm happy

A 14 cm with a 40 kg shell is a bit smaller than the usual 6'' guns (the 6'' of the Nelson-class fired shells of about 45 kg), the 5.25'' of King George V and the Didos' used 36kg shells. The 5.5'' of HMS Hood used 37kg shells.
These guns will be easier to load because of the lower shell weight, increasing the rate of fire (at least that was my thought).

True. Though 6"/47 quick firing guns fire off a 50kg shell that is a guaranteed to cause more hurt I think. I guess what you lose in quality, you gain in quality.

Though I admit that my idea of a light cruiser happens to have 5"/38s in addition to the main guns of 6"/47, which might be tad overkill....

[Raesene]

[...]

True. Though 6"/47 quick firing guns fire off a 50kg shell that is a guaranteed to cause more hurt I think. I guess what you lose in quality, you gain in quality.

Though I admit that my idea of a light cruiser happens to have 5"/38s in addition to the main guns of 6"/47, which might be tad overkill....

A bit early for a Cleveland-lookalike

Rate of fire and number of guns is important in the Tuscan Navy. I partly complensate that with heavier shells than springsharp offers, following the Austro-Hungarian guns concept; their 35 cm guns fired shells about the weight of the german 38cm (700 kg vs 750kg).

My line of thought is more towards the RN Town-class, ending with Edinburgh/Belfast as orgininally envisaged, with 4 quad turrets.
Or maybe five quad turrets in a Brooklyn-layout...