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Heres a quick SpringSharp attempt; this is an abbreviated report, if you'd like the whole thing let me know.

30kts BB Proposal A

Displacement
> 45,540t Light
> 47,680t Standard
> 52,210t Full

Dimensions
> 245m x 30m x 10m
> 804ft x 98ft x 33ft
> Block Coefficient 0.677

Armament
> 3xIII 410mm/50 (Centerline forward, 1 raised mount, 100rpg)
> 12xII 120mm/45 (Sides center/aft, 4 raised mounts, ~360rpg)

Armour
> Belt 405mm (15.9") @ 19 degrees
> Deck 200mm (7.9")
> Conning Tower 460mm (18.1")
> Turrets
> > Primary 550mm (21.7")
> > Secondary 10mm (0.4")

Propulsion
> Maximum
> > 30.4kts @ 160,000shp
> > 29.9kts @ 150,000shp
> Cruise 15kts @ 15,000shp
> Range 7500nm @ 15kts
> Bunker 4,532t

So Terminus' estimate was pretty close, maybe a little under on the displacement.

Range could be quite a bit more if desired, as bunkerage is pretty low compared to other Japanese BBs (~6000t). Design is notably more efficient fuel use wise than historical Yamato class, though not as good as smaller BBs like Kongo or Nagato. I put the 150kshp figure in to show how little that extra 10kshp will get you; and getting up to say 33 knots will take around 70kshp more. I went with the suggested layout of all guns forward, though I personally believe the issues with blast and loss of rearward firepower are worth the slightly longer citadel required (not to mention it just looks better [;)]). If you'd like a comparative one for that design let me know.

In game, I would estimate durability at around 180-190 mark.

This is an interesting direction to take with regards to designs; using extra displacement for defence rather than offence much like the WWI german navy did is an interesting change for Japan, as most of their 8-8 plan ships were along the lines of 'eggshells with big hammers'.

Here's my old side for the 140...

Thanks, Juan!

ORIGINAL: JuanG
This is an interesting direction to take with regards to designs; using extra displacement for defence rather than offence much like the WWI german navy did is an interesting change for Japan, as most of their 8-8 plan ships were along the lines of 'eggshells with big hammers'.

Evaluations of attack/defense relative importance are not static. Germans ships built before WWII were not very well armored, and never-were superdreadnoughts following them had relatively even weaker protection. Japanese ordered well-balanced ships in early 20th century, and Yamato, as well as their cruisers of the Pacific War can be considered to have balanced offense and defense in as well (save for the cruisers' Achilles heel of torpedo detonations).

I think we can settle on 150 000 shp engine, as used on RL Yamato class here, as speed difference is pretty minimal. Better looks are a strong argument (as is following the historical pattern if possible), but with the 150k turbine the ship only just reaches the desired speed. What changes will use of the standard configuration cause? I think 29.5-29.6 knots is the lowest level at which the design comittee might still said "close enough". The same goes for adding exta weight by expanding bunkerage. I'll be very grateful if you recalculate that, as Springsharp still befuddles me and I've yet to get any sensible results from it[&:].

ORIGINAL: FatR

Thanks, Juan!

ORIGINAL: JuanG
This is an interesting direction to take with regards to designs; using extra displacement for defence rather than offence much like the WWI german navy did is an interesting change for Japan, as most of their 8-8 plan ships were along the lines of 'eggshells with big hammers'.

Evaluations of attack/defense relative importance are not static. Germans ships built before WWII were not very well armored, and never-were superdreadnoughts following them had relatively even weaker protection. Japanese ordered well-balanced ships in early 20th century, and Yamato, as well as their cruisers of the Pacific War can be considered to have balanced offense and defense in as well (save for the cruisers' Achilles heel of torpedo detonations).

I think we can settle on 150 000 shp engine, as used on RL Yamato class here, as speed difference is pretty minimal. Better looks are a strong argument (as is following the historical pattern if possible), but with the 150k turbine the ship only just reaches the desired speed. What changes will use of the standard configuration cause?

I would argue that the German WWI BB designs were very well armoured for their time (compare Konig to Iron Duke or even Queen Elizabeth). Regardless, thats a discussion for another time.

Shifting to a standard layout brings the following changes;

All Displacements up by ~1800tons, Length increased to 255m (+10m), Maximum Speed 29.85kts @ 150,000shp (152,500shp for 30kts). Bunkerage increased to 4660t (+128t) for 7500nm.

As an experiment, using a bunker close to the other BBs gives the following on top of that;

Light Displacement up by ~50tons, Full Displacement up by ~1200tons (up to 55,100t now), Maximum Speed 29.8kts @ 150,000shp (154,000shp for 30kts). Bunkerage increased to 5816t for 9500nm. Standard displacement 49,250t.

Also, witness feature creep here. You'd be surprised how quickly one can add 5,000t to a design just trying to 'improve it' minimally. Granted in our case its just fuel for now. If you want a full readout, let me know.

ORIGINAL: JuanG

I would argue that the German WWI BB designs were very well armoured for their time (compare Konig to Iron Duke or even Queen Elizabeth). Regardless, thats a discussion for another time.

I agree, I was talking about what they were building and intending to build before WW II.

ORIGINAL: JuanG
Shifting to a standard layout brings the following changes;

All Displacements up by ~1800tons, Length increased to 255m (+10m), Maximum Speed 29.85kts @ 150,000shp (152,500shp for 30kts). Bunkerage increased to 4660t (+128t) for 7500nm.

As an experiment, using a bunker close to the other BBs gives the following on top of that;

Light Displacement up by ~50tons, Full Displacement up by ~1200tons (up to 55,100t now), Maximum Speed 29.8kts @ 150,000shp (154,000shp for 30kts). Bunkerage increased to 5816t for 9500nm. Standard displacement 49,250t.

Also, witness feature creep here. You'd be surprised how quickly one can add 5,000t to a design just trying to 'improve it' minimally. Granted in our case its just fuel for now.

Thanks, it is very gracious of you to do all this work for us.

What do you think about all of this, John? I'd say, we should go with the last variant, for the best balance of traits. It is pretty big, but still sufficiently smaller than Yamato, to justify completion of four ships, I think.

EDIT: Although, while Juan's arguments against all-forward turrets positioning sound solid, and the increase in size/loss of speed from using a classical positioning isn't that big, I'm still partial to using all-forward turrets, if only for the distinctive look[:)]. As Terminus' excellent shipside shows, such ship actually looks pretty good, and with more RL Yamato-style supestructure, it will be even cooler.

The armour is far too heavy, IMHO. What's the role for this ship? CV escort, battleline flagship, what?

EDIT:

ORIGINAL: Terminus

The armour is far too heavy, IMHO. What's the role for this ship? CV escort, battleline flagship, what?

With bigger guns being non-viable yet, and the fourth turret increasing weight too much, armor is the only remaining way of achieving some form of superiority to enemy post-treaty battleships.

As about the planned role:
1)Vanguard of the battleline in case of an all-out battleship battle. Kongos are way too fragile against 16in shells, and RL BatDiv3 was planned to be used in the vanguard of the first two divisions in a daylight battleship battle, only for the lack of available alternatives. These ships, on the contrary, should be able to withstand long-range fire from American/British battleships, and close with them without fearing destruction or crippling from a single well-aimed shell, hopefully getting into range where their citadels can still withstand hits, yet they can score penetrating hits on the enemy.
2)Fast attack battleship division, capable of maintaining the same speed as non-battleship main components of the fleet (carriers and heavy cruisers), yet being able to go toe-to-toe with the post-treaty battleships. If it is technically viable, why new battleships shouldn't be brought in line with the fast components of the fleet, instead of the slow ones? Duty of carrier escorts fits thin-skinned Kongos more, although these ships will undoubtely be used this way as well.

ORIGINAL: Terminus

The armour is far too heavy, IMHO. What's the role for this ship? CV escort, battleline flagship, what?

EDIT:

Maneuver is a little low, but otherwise good. I'd say atleast 25 for Maneuver, maybe 26. Use SoDak and Iowa as reference points. Thought we were going with 30 knots?

Also, I forgot to put it in the report, but I assigned weight for ~7 floatplanes like in the historic Yamato. Deck space should definately not be a problem given you've got the whole aft deck to play with. I could see the ship having space to potentially carry as many as 10 floatplanes.

Pretty wild discussion on this beast. They are smaller then the Yamato but no by much. How much $$$ would we see being saving here. I love the new BBs but want more CVs!

Tradeoffs Gents---Tradeoffs...

ORIGINAL: John 3rd

Pretty wild discussion on this beast. They are smaller then the Yamato but not by much. How much $$$ would we see being saving here? I love the new BBs but want more CVs!

Tradeoffs Gents---Tradeoffs...

ORIGINAL: John 3rd

Pretty wild discussion on this beast. They are smaller then the Yamato but no by much. How much $$$ would we see being saving here. I love the new BBs but want more CVs!

Tradeoffs Gents---Tradeoffs...

The combined displacement of all four is about equal to combined displacement of the three built ships of the Yamato class, plus we're hopefully saving on weapons and costly reconstruction of Shinano here. I think they will cost roughly as much as Yamato/Musashi/Shinano, maybe even less, and will occupy the yards for less time.

It would still take a LONG time to roll all that armour. Japan's armour factories were not exactly fast.

ORIGINAL: JuanG

Maneuver is a little low, but otherwise good. I'd say atleast 25 for Maneuver, maybe 26. Use SoDak and Iowa as reference points. Thought we were going with 30 knots?

Also, I forgot to put it in the report, but I assigned weight for ~7 floatplanes like in the historic Yamato. Deck space should definately not be a problem given you've got the whole aft deck to play with. I could see the ship having space to potentially carry as many as 10 floatplanes.

I think you've calculated weight with 12x2 DP mounts? Placement I think should be: 1 raised mount behind the main turrets, four on each side (2 on the deck level, 2 raised), 3 in the rear, behind the main superstructure. Maybe 4 in the rear, if fitting a twin firing over the main turrets will be difficult

If we accept the project (John?), different art will be needed, with no aft secondary battery, aft end and floatplane equipment here resembling RL Yamato, and perhaps superstructure more similar to it as well (thanks in advance if anyone will be kind enough to draw it).

As about the production of armor, yes it will be as difficult as IRL, and the program will consume the same huge funds as RL Yamato program, but I think Japan is too poor to affort cheap battleships, if any should be built at all (and rejecting battleships entirely before the war begins is too unbelievable). Alt_naval provides a good illustration to what trying to go for economical solutions, rather than effective ones, leads in this area: a fleet of BBs that, optimistically, costs 2/3rds of RL Jap battleline cost, and can take only on cruisers in actual fight (because the only two units that maybe can go one-on-one against most pre-treaty battleships, never mind post-treaty ones, are far too slow).

How's this?

I LOVE the artwork above as well as the concept.

My concern sits with the issues that bedeviled the Yamato's. Will these ships FIT in EXISTING yards. If yes then there is no cost to increasing slipway size. Four for the cost of three? OK. That saves Yen somewhat but is it enough for whatever else we are building?

Armor is an issue as Terminus stated. What was the armor on the North Carolina-Class? These would be contemporary to the first pair. Knowing how the Japanese wanted MORE then I could see some extra on top of that class... The US Fleet is a little beyond my immediate knowledge range for this stuff.

The North Carolina had about 70-80% of the armour we postulate here.

My problem with it is knowing where the Japs came to this armour scheme. The usual way to do armour was to immunize a ship against its own main battery at optimum range. Let's face it, this IJN ship isn't super-heavily gunned and it's being armoured against a gun that doesn't exist.

Excellent art, Terminus! Thanks.

As about stats, with all-forward turrets, normal displacement should be around 47 450 though. Speed and probably Maneuver should be higher by, as noted by Juan.

ORIGINAL: John 3rd

I LOVE the artwork above as well as the concept.

My concern sits with the issues that bedeviled the Yamato's. Will these ships FIT in EXISTING yards. If yes then there is no cost to increasing slipway size. Four for the cost of three? OK. That saves Yen somewhat but is it enough for whatever else we are building?

As ship 101 was 30% completed, we might even save something here... But extra materials and money will go into wartime reconstructions of the oldest battleships, I think.

About increasing slipway size - I don't think that slipways will need rebuilding. See here:
http://books.google.ru/books?id=TAyRtKK ... ip&f=false
p.50: "The yards chosen for the construction of these ships were carefully selected. In some cases approaches to them had to be dredged and the building facilities modified to handle the construction".
Doesn't imply the need to reconstruct the yards to the point of extending slipways. Even actual Yamatos had only slightly bigger dimensions than Shokaku/Taiho carriers, and these ships will be smaller.

ORIGINAL: John 3rd
Armor is an issue as Terminus stated. What was the armor on the North Carolina-Class? These would be contemporary to the first pair. Knowing how the Japanese wanted MORE then I could see some extra on top of that class...

The proposed belt armor is approximately 100mm thicker than that of post-treaty US battleships. IRL Japanese considered that such difference is necessary to provide a tactically noticeable (i.e., a recognizable zone where you can penetrate the enemy citadel, and the enemy can't penetrate yours) advantage in protection. And this ship really needs one, as it doesn't have an advantage in armament, like Yamato.

EDIT: In response to Terminus above - the logic should go somewhat like this. "We need a superior battleship, that can kill existing and currently building enemy BBs one-on-one and at least limp into port after that, because we can't win the numbers race" -> "The best way to do that is to install both guns and armor heavier than that of the potential enemy BBs" -> "But the heavier guns design we can produce is unsuitable for a ship that is supposed to fight more than 1-2 battles per war, and we expect more. Also, very heavy and expensive." -> "Let's at least keep heavier armor, and give the new ship enough speed so it can at least dictate the distance of engagement, which will aslo enable it keep up with non-battleline components of the fleet as well (unlike trying to achieve firepower advantage by expanding the number of guns to 12, which will probably make the design too big and heavy)".

If you look closer at the stats, I've gone with Juan's second option of upping the bunkerage for the 9000+ mile endurance. That's why it's 49000+ tons.

ORIGINAL: Terminus

If you look closer at the stats, I've gone with Juan's second option of upping the bunkerage for the 9000+ mile endurance. That's why it's 49000+ tons.

I thought 49k+ plus was with extra bunkers on top of the traditional turret placement.

D'OH, you're right. It's still plus 1,000 tons for the extra fuel, though. Compromise at about 48.5k?