Jump to content
You need to play a total of 5 battles to post in this section.
Ajatcho

Japanese Capital Ship Design from Kawachi to Yamato

27 comments in this topic

Recommended Posts

Members
42 posts
217 battles

The one thing Japan stuck to during the 20th Century was the idea of a single decisive battle deciding the outcome of a war, something they had done when they destroyed the Russian 2nd Pacific Squadron at Tsushima, and while Yamamoto and others advocated focusing on aircraft carriers as the way to win the war once it began, many still clung to that single decisive battle would win the war even when it became clear that the war was lost.

Share this post


Link to post
Share on other sites
263
[REVY]
Members
977 posts
7,854 battles
On 12/4/2018 at 11:37 PM, snakes3425 said:

The one thing Japan stuck to during the 20th Century was the idea of a single decisive battle deciding the outcome of a war, something they had done when they destroyed the Russian 2nd Pacific Squadron at Tsushima, and while Yamamoto and others advocated focusing on aircraft carriers as the way to win the war once it began, many still clung to that single decisive battle would win the war even when it became clear that the war was lost.

That was the Mahan's Theory of Sea Power.

 

Mahan advocated the 'decisive battle' idea based on how Trafalgar had turned out. The Japanese win over the Russians seemed to back up Mahan. 

Share this post


Link to post
Share on other sites
969
[LEGIO]
Members
3,099 posts
5,743 battles

It strikes me how the armor scheme of the Yamato class was quite inefficient from a production standpoint. The well angled forward and aft citadel armored bulkheads may have saved some weight, but surely not that much due to the added complexity. A thicker vertical armor plate would have probably been easier to manufacture too.

Share this post


Link to post
Share on other sites
494
[MAHAN]
Beta Testers
1,416 posts
5,170 battles

Hello,

I was actually the host for this podcast. My apologies for my slow speech at times, the recording method I used was awful. I will be recording a more specific thematic follow-up next week (armour, fire control, etc., etc.) complete with a better recording method so I can actually speak properly, haha.

Share this post


Link to post
Share on other sites
115
[SOUTH]
Members
252 posts
2,640 battles
On 12/10/2018 at 5:40 PM, Lampshade_M1A2 said:

It strikes me how the armor scheme of the Yamato class was quite inefficient from a production standpoint. The well angled forward and aft citadel armored bulkheads may have saved some weight, but surely not that much due to the added complexity. A thicker vertical armor plate would have probably been easier to manufacture too.

The point of the Yamatos were to obsolete the Standards in a fleet action, which they likely would. Having a solid 7 knot advantage and substantially stronger guns would do that, plus belt and deck that'd have a huge immunity zone to the 14s and 16s of the Standards. Efficiency aside for design considerations, slanted out armor seemed to be the standard by that interwar design era for likely good reason. Presumably their calculations on likely trajectories of American shells of the known types played into why it was designed that way.

Share this post


Link to post
Share on other sites
361
[ZIPPO]
Members
1,589 posts
3,603 battles
On 12/14/2018 at 5:06 PM, Neph said:

The point of the Yamatos were to obsolete the Standards in a fleet action, which they likely would. Having a solid 7 knot advantage and substantially stronger guns would do that, plus belt and deck that'd have a huge immunity zone to the 14s and 16s of the Standards. Efficiency aside for design considerations, slanted out armor seemed to be the standard by that interwar design era for likely good reason. Presumably their calculations on likely trajectories of American shells of the known types played into why it was designed that way.

Not just that, they were well aware of the 35,000 ton treaty battleships the US and  UK were producing so they built them with the plan of facing them. The US weren't the only targets, they also knew UK had a sizable force in the area regardless which is why they attacked them after Pearl Harbor 

Share this post


Link to post
Share on other sites
1,372
[RKLES]
Members
7,543 posts
9,589 battles
On 12/4/2018 at 10:37 PM, snakes3425 said:

The one thing Japan stuck to during the 20th Century was the idea of a single decisive battle deciding the outcome of a war, something they had done when they destroyed the Russian 2nd Pacific Squadron at Tsushima, and while Yamamoto and others advocated focusing on aircraft carriers as the way to win the war once it began, many still clung to that single decisive battle would win the war even when it became clear that the war was lost.

 

On 12/10/2018 at 11:06 AM, Lord_Slayer said:

That was the Mahan's Theory of Sea Power.

 

Mahan advocated the 'decisive battle' idea based on how Trafalgar had turned out. The Japanese win over the Russians seemed to back up Mahan. 

And to be fair the Japanese were not the only ones that thought that way leading up to and even during WWII. Pretty much all the major navies had been taken in by those ideas until Pearl Harbor proved ironically in a decisive manner that the argument of using Carriers was over and done with. Think we discussed this in a couple other historical threads as well such as the subs ne I had made “ What if Japan had avoided Pearl Harbor”. Some of the world’s naval leaders had still been debating on if CVs could really be better than a traditional BB force, and with out Pearl Harbor attack I would have given that debate another few months at least if not a couple more years or so, perhaps even longer since hard to say. ( After all “theoretical” ideas that go against long and widespread beliefs often need a major and conclusive demonstration in practice to change such ideas quickly)

So bottom line we can’t fault the those in the IJN that had planned for and expected Mahan ideals when other nations still clung to such ideas. And actually I guess you could call Bismarck Battle Decisive for RN, although it was scuttled. So I would go with Scharnhorst battle being the of the last battle fought as a Decisive Capital ship gun engagement.

Edited by Admiral_Thrawn_1

Share this post


Link to post
Share on other sites
361
[ZIPPO]
Members
1,589 posts
3,603 battles
5 hours ago, Admiral_Thrawn_1 said:

 

And to be fair the Japanese were not the only ones that thought that way leading up to and even during WWII. Pretty much all the major navies had been taken in by those ideas until Pearl Harbor proved ironically in a decisive manner that the argument of using Carriers was over and done with. Think we discussed this in a couple other historical threads as well such as the subs ne I had made “ What if Japan had avoided Pearl Harbor”. Some of the world’s naval leaders had still been debating on if CVs could really be better than a traditional BB force, and with out Pearl Harbor attack I would have given that debate another few months at least if not a couple more years or so, perhaps even longer since hard to say. ( After all “theoretical” ideas that go against long and widespread beliefs often need a major and conclusive demonstration in practice to change such ideas quickly)

So bottom line we can’t fault the those in the IJN that had planned for and expected Mahan ideals when other nations still clung to such ideas. And actually I guess you could call Bismarck Battle Decisive for RN, although it was scuttled. So I would go with Scharnhorst battle being the of the last battle fought as a Decisive Capital ship gun engagement.

 

Well it's hard to even say that because by the end of WWII, proximity fuse shells were getting better and better among with ever increasingly radar accuracy among with fire control, there was a worry CVs would be put back to a limited role, granted the jet age put the final nail in the coffin 

Share this post


Link to post
Share on other sites
1,333
[GWG]
[GWG]
Members
5,597 posts
10,056 battles

1945 brought in Battleship bombardment over CV ops.  The Japanese had proximity fuses and homing torpedoes.

Not to mention the 'LIVE' guided weapons.  At Okinawa, the US was losing function of one CV a day.  Those losses were unacceptable.

Had 'Ten-Go' delayed until after the US CV groups had been whittled down and forced to withdraw, they might have had a chance to succeed.

  • Bad 1

Share this post


Link to post
Share on other sites
300
[JFSOC]
Members
972 posts
3,079 battles

I count a total of just 16 carrier hits by Kamikaze off Okinawa.  The Victorious and Formidable each took two separate hits on different days.  Most resulted in minor damage to the ship and generally they continued operations afterwards.  There are a couple of dates that stand out when the Japanese launched mass Kamikaze raids with hundreds of planes involved.  The most significant is probably May 4th.  When they managed to hit five carriers.  Most of those were British (3) and shrugged off the hit.

Kamikaze were generally not very discriminate about their targets.  Often the first ship spotted was the recipient.

  • Cool 1

Share this post


Link to post
Share on other sites
1,333
[GWG]
[GWG]
Members
5,597 posts
10,056 battles
5 hours ago, Murotsu said:

I count a total of just 16 carrier hits by Kamikaze off Okinawa.  The Victorious and Formidable each took two separate hits on different days.  Most resulted in minor damage to the ship and generally they continued operations afterwards.  There are a couple of dates that stand out when the Japanese launched mass Kamikaze raids with hundreds of planes involved.  The most significant is probably May 4th.  When they managed to hit five carriers.  Most of those were British (3) and shrugged off the hit.

Kamikaze were generally not very discriminate about their targets.  Often the first ship spotted was the recipient.

A Kamikaze sunk the DD William D Porter...  That was an impressive feat in history.  No doubt saved millions of American lives.

  • Funny 1

Share this post


Link to post
Share on other sites
494
[MAHAN]
Beta Testers
1,416 posts
5,170 battles

The philosophy behind the Yamato-class was fine. Criticism of the decision to build them is done entirely in hindsight. They went ahead from 1934, when air power was right on the cusp of an RMA. Air power in the interwar years was nowhere even close to as capable as its advocates professed (without evidence). There was so much overstatement from air power radicals about how air power would make surface fleets obsolete that their most crackpot claims were literally never realized. Air power's offensive capability through the 1920s was anemic. Aircraft didn't have the range, speed, ordnance, or doctrine to by a truly effective offensive weapon against warships. Training crews and adapting technology to actually navigate over water, find ships, and then hit them is often taken for granted. Wrongfully so. Aircraft began to show signs of improvement from the start of the 1930s, and the doctrine of navies began to adapt along with it, contrary to the binary and oversimplified "stuffy battleship admirals" vs. "brilliant, forward-thinking visionaries."

There was a clear doctrinal progression of the use of naval air power from primarily scouting/spotting (and denying the same to the enemy), to offensive usage as aircraft performance increased to the point that they could be used in such a capacity. The primary target was the enemy's aircraft and aircraft carriers to gain control of the air over the battle space. Aircraft could then cripple enemy warships for the surface ships to finish off. Not exactly backward thinking for the time. Problems arose when the technology from the mid-to-late 1930s improved so rapidly that doctrine couldn't keep pace. From the mid-1930s the first generation of carrier-borne, all-metal monoplanes appeared on the drawing boards. Their appearance brought a massive increase in capability, but the war was on top of the world's major navies (or had already started) by the time the new generation of aircraft entered service (1937-1941). The debate wasn't about "battleships vs. aircraft carriers" so much as how the aircraft carriers would be used in the fleet. Should they be used primarily in the offense or defense? Could they stand on their own or should they operate in support of the battleships? Etc. There was a reason that the world's navies were able to quickly make use of their carriers when war broke out, and it wasn't because they had all ignored naval air power until 1941. Heck, there was a reason the navies had significant amounts of air power available at the outbreak of the war in the first place.

  • Cool 1

Share this post


Link to post
Share on other sites
300
[JFSOC]
Members
972 posts
3,079 battles

On a more technical note, a big part of Japan's problem was at the time they simply weren't leaders in ship design and engineering.  By the mid to late 30's the US and Germany, in particular, had moved to welding as the assembly method for ships.  This held several advantages.  First, the ship's structure was stronger.  Next, elimination of overlapping plates and stringers for rivets reduced weight substantially.  Japan was still riveting ships and their welding technology through 1945 remained limited and of iffy quality.

The US also had better ability to pay attention to details in the design having both more experience and engineering capacity available.  It's pretty clear that the US could and did pay far more design detail attention to stability and buoyancy than the Japanese could and did.  The typhoon that wrecked a number of their ships, or the Mogami class that as designed, had serious cracking of the hull from poor welding (requiring reinforcement using riveting), as well as stability issues.

The US, and Britain, also had considerably more experience building steam turbines (the Germans relied heavily on Swiss Brown - Boveri data for theirs) meaning that their plants could be lighter and more efficient.  This was particularly true with the US who got 600 psi plants to work very efficiently by 1940.  That's almost double the working pressures that Japanese plants ran at.

This results in their ships under the WNT and LNT being about 25 to 40% heavier than their US counterparts.  Thus, the US could successfully cram fifteen 6" guns on a 10,000 cruiser with reasonable armor protection while the Japanese required roughly 15,000 tons to do the same thing.  It wasn't that the Japanese were stupid.  It was simply they didn't have the capacity in terms of design engineers and experience that some other nations did, while at the same time they tried to push the curve of design limits beyond safety margins.

That curvy hull form that is characteristic on many Japanese warships was a design attempt to minimize hull weight by reducing its height according to the wave forms expected to be generated in operation.  Thus, the lower points were ones where wave height was expected to be lower, etc.  I suspect it made a good many other design issues problematic, such as internal deck heights.  Since nobody else did this, I'd say it was likely not worth the effort.

I suspect that the US could have built a Yamato on about 50,000 tons of ship as a comparison.

Share this post


Link to post
Share on other sites
2,558
[NSF]
Beta Testers
5,038 posts
6,522 battles
On 12/17/2018 at 2:55 PM, Murotsu said:

I suspect that the US could have built a Yamato on about 50,000 tons of ship as a comparison.

Some of the various 45-50000 ton ‘slow’ (26.5-28 knot) designs are essentially that. 15” sloped belts, 7” decks, 20” turret faces, nine 18” guns...to be honest, I have some doubts that the displacements listed for some of these designs would actually be possible, but the numbers provided do generally match up. 

I have always wondered how much weight the Japanese wasted on the magazines underwater mine protection. It’s difficult to find a complete breakdown of the armor weight for each section, and those sections would probably not include the mass spent on the support structure for the additional deadweight in armor.

Share this post


Link to post
Share on other sites
2,500
[HINON]
Beta Testers, In AlfaTesters
7,339 posts
2,050 battles
On 12/25/2018 at 11:31 AM, Big_Spud said:

Some of the various 45-50000 ton ‘slow’ (26.5-28 knot) designs are essentially that. 15” sloped belts, 7” decks, 20” turret faces, nine 18” guns...to be honest, I have some doubts that the displacements listed for some of these designs would actually be possible, but the numbers provided do generally match up. 

I have always wondered how much weight the Japanese wasted on the magazines underwater mine protection. It’s difficult to find a complete breakdown of the armor weight for each section, and those sections would probably not include the mass spent on the support structure for the additional deadweight in armor.

I imagine if you know the dimensions of the plate, you could get a rough estimate based on the 40 lbs. = 1" of armor (over a square foot, iirc?) rule.

In any case, if you told American designers to build a ship like Yamato, you'd have a massive weight saving from the propulsion alone, especially if you could ditch the 'four boiler rooms side-by-side arrangement'. Yamato's 12 boilers feed four turbines for 150,000 shp, at a weight of 5300 metric tons. The SouDak's are 130k shp with only 8 boilers, and the weight is only 3,647 metric tons - Yamato generates 28 shp/ton, while SouDak generates 35.6 shp/ton. Theoretically, one could generate the same 150k shp with just ~4200 mt, although obviously that's not a hard number to use.

I imagine that would also repeat itself with various other systems, and possibly even the hull structure of the ship itself.

Share this post


Link to post
Share on other sites
278
[HC]
[HC]
Beta Testers
1,475 posts
9,931 battles
On 12/10/2018 at 8:40 PM, Lampshade_M1A2 said:

It strikes me how the armor scheme of the Yamato class was quite inefficient from a production standpoint. The well angled forward and aft citadel armored bulkheads may have saved some weight, but surely not that much due to the added complexity. A thicker vertical armor plate would have probably been easier to manufacture too.

 

On 12/14/2018 at 5:06 PM, Neph said:

The point of the Yamatos were to obsolete the Standards in a fleet action, which they likely would. Having a solid 7 knot advantage and substantially stronger guns would do that, plus belt and deck that'd have a huge immunity zone to the 14s and 16s of the Standards. Efficiency aside for design considerations, slanted out armor seemed to be the standard by that interwar design era for likely good reason. Presumably their calculations on likely trajectories of American shells of the known types played into why it was designed that way.

Slanted out armor increases the effective thickness, very similar to sloped armor on a tank. The difference is, with sloped armor as found on tanks, the longer the range, the closer to perpendicular the shells impacts, which reduces the effectiveness. Slanting out at the top, the longer the range, the greater the angle of impact, the more effective the armor. At least until the incoming round hits the deck behind the belt. Also, AP shells going though armor plate tend to normalize, or square up to the plate as they go though, which will leave the shell heading upwards though ship's structure instead of downwards through the magazines.

Also, production wise, there's a few problems with making thicker plates. It gets harder to make the plates without them cracking. The plates have to be made smaller, as to not exceed the ability of a shipyard to install them efficiently, which will leave more joints, which are weaknesses. Finally, a big problem for Japan, was shortages of the rare materials for making armor grade steel, making more armor just makes this shortage worse.

Edited by SgtBeltfed

Share this post


Link to post
Share on other sites
300
[JFSOC]
Members
972 posts
3,079 battles

With Japanese armor there were several issues they were contending with.

First, their armor was roughly equivalent to Vickers NC and early Krupp cemented.  This is a process issue.  To make armor, the Japanese had to have the proper means to mix the alloying agents into the steel, and know the formulas to use in doing that.  At the time, this was something of a trade secret for many manufacturers and nations.  There were none of the AISI standards existed back then.  Today, it's as easy as picking up a copy of this book to find out all about any steel you want to mention:

0831130911.jpg

I still use the 24th edition, but steels really haven't changed today...

Anyway, that's their first problem:  Getting the steel alloyed properly each and every time.

The next problem they have is casting the plates and shapes they need.  This is as much an art as a process.  Thick castings are a problem in several ways: 

First, you have to cool the casting in a precise manner to control grain size.  As the steel cools, it forms grains.  The larger these are the more weakness you are putting into the plate.  With thin plates and castings, this isn't a huge problem.  But, pouring and cooling a plate 6" or more thick it's a major issue.  You can get all sorts of grain sizes and that can seriously weaken a plate.

Then there's the weight and size of the plate and the pour.  You have to be able to alloy the steel and pour the plate all in one shot.  You can't pour some, then pour some more because the plate will be cooling at different rates in different portions.  This will introduce weaknesses into it.  So, plate size is limited by the foundry or steel mill's crucible size and quantity.  This will also determine just how much steel you can make too.

Then, post production, if you want face hardening you need a furnace large enough to heat the plate to critical temperature and hold it there for several days while it face hardens using whatever process you are going to use.  The KC method is essentially to coat the plate with lampblack (carbon dust) and heat it in a vacuum furnace letting the carbon sublimate into the plate and hardening the surface to a few millimeters.  Again, the process has to be precise and repeatable to get consistent results.

Above about 3" thickness, face hardening is less important than the alloy and grain size of the steel.  Better consistency of these two items makes a superior thick plate.

Putting the armor in place requires a method to secure it to the ship.  You can't weld or rivet it because welding will cause weaknesses at the weld joints if the armor is face hardened or heat treated.  Riveting is out because trying to drill holes in an armor plate is extremely difficult (it is designed to resist having holes put in it...)  These would also weaken the armor.  In the 20's and 30's the typical method was to back the plates with teak wood and use special bolts that secured the plates from the rear leaving the faces untouched.  The wood backing acts as a shock absorber for the plate.

So, for Japan, they were limited in how big a pour they could make, had issues with quality control, and also very limited by the amount of armor they could produce simply by the size and number of steel mills they possessed.  Building a battleship like Yamato took a big chunk of their national resources over a period of several years.  Hence, when the war started, they could no longer devote that sort of resources to construction of a single ship and that in turn is a major reason Shinano wasn't finished as a battleship.  It was taking up too many critical resources needed more urgently for things like aircraft carriers or merchant ships.

Share this post


Link to post
Share on other sites
Members
1,252 posts
737 battles
15 hours ago, Phoenix_jz said:

I imagine if you know the dimensions of the plate, you could get a rough estimate based on the 40 lbs. = 1" of armor (over a square foot, iirc?) rule.

In any case, if you told American designers to build a ship like Yamato, you'd have a massive weight saving from the propulsion alone, especially if you could ditch the 'four boiler rooms side-by-side arrangement'. Yamato's 12 boilers feed four turbines for 150,000 shp, at a weight of 5300 metric tons. The SouDak's are 130k shp with only 8 boilers, and the weight is only 3,647 metric tons - Yamato generates 28 shp/ton, while SouDak generates 35.6 shp/ton. Theoretically, one could generate the same 150k shp with just ~4200 mt, although obviously that's not a hard number to use.

I imagine that would also repeat itself with various other systems, and possibly even the hull structure of the ship itself.

The design scheme that @Big_Spud was referring to is the April 1938 "slow" design. I'll list out the characteristics below from Friedman page 307.

Waterline length 800 ft
Beam 108 ft 3 in
Draft 35.96 ft
Max displacement 56,595 long tons
Battle displacement 54,495 long tons
Standard displacement 45,495 long tons
Speed 27.5 knots
SHP 130,000
Range (15 knots) 15,000 nmi
Main battery 9 x 18"/48
Secondary battery 20 x 5"/38
Belt (19 degrees on 30# STS) 14.75"
Heavy deck 5.1"
Bomb deck 1.5"
Splinter deck 0.63"
Barbette, conning tower 21"
Turret face 20"
Turret, CT roof 10"
Traverse bulkheads 16.75"
Splinter protection 2.5"

Given the hull's outer dimensions, the belt armor would've almost certainly been arranged internally like on South Dakota and Iowa. The heavy deck would presumably be laminated on 1" STS for a combined thickness of some 6".

I would like to consult some naval historians on how feasible it would be to actually build this ship to its design displacement values. Certainly, based on SoDak and Iowa displacement figures, the additional AA armament and electronics alone would have added another 2-3000 tons. I would also imagine that the backing plate for the belt would be thicker; SoDak and Iowa were 35#.

Edited by DeliciousFart

Share this post


Link to post
Share on other sites
2
[HMCS-]
Members
7 posts
5,453 battles

Japanese and American officers criticized Yamamoto post war for not committing the entirety of the Combined Fleet at Guadalcanal where they actually had a chance for the decisive fleet action.  Instead, the piecemeal commitment and war of attrition in the Solomon's, coupled with the prewar construction programs, decisively tipped the balance towards the USN.  The Nimitz Gray Book is illuminating in tracking the evolution of the strategic and operational thinking of CINCPAC and CINCUSFLT.  Their message traffic indicates an attempt to husband capital ships as a hedge, and then to eventually build up for eventual use to force the decisive battle on the USN's own terms.

http://www.ibiblio.org/anrs/graybook.html

 

Share this post


Link to post
Share on other sites
494
[MAHAN]
Beta Testers
1,416 posts
5,170 battles

VH was adopted for economic rather than qualitative reasons. The Japanese could, and did, produce higher quality armour. This is from the extensive chapter on Japanese armour in Lengerer, Hans; Ahlberg, Lars. Capital Ships of the Imperial Japanese Navy 1868-1945: The YAMATO Class and Subsequent Planning. Other types of armour were used in the Yamato-class as well, and there is a multitude of factors beyond that.
 

Quote

 

Vickers Hardened Armor (VH)
VH plates were used for the (1) 410-mm thick hull side armor, (2) 660-mm thick front shield of the main gun turrets and (3) 560-mm thick upper part of the main gun barbettes. The biggest features were (1) to stop the surface carbonisation of the V( ickers) C( emented) armor and (2) to improve the toughness of the back plate. These goals were attained by the adoption of a special production method that became a secret patent of the IJN. Roughly speaking the principles were the application of the then world’s biggest hydraulic press, the change of the heat treatment and the introduction of a particular method for the investigation of the physical properties. An outline of the process follows.

Melting and Ingot Practice
All armor steel was made in the acid open hearth (AOH) process. For the production of the large quantity the Third Steel Work (Seikō Kōjō) was established in Kure Navy Yard and four new acid open hearth furnaces of 70 tons each were installed. In the charges about 35% pig iron (mainly from Korea [Kenjuko] or Kamaishi [Iwate Prefecture]) and 65% scrap were used. The heats of three furnaces were necessary to fill up one mould in order to get one ingot of approximately 200 tons.

Rolling and Forging
The steel ingot was roughly forged to approximately half of reduction and then rolled. Forging was accomplished by a very large hydraulic press, rolling by either the British made (Davy Bros., bought in 1904) or Japanese-made mill (using the Davy Bros. unit as a model, built in 1921) with rolls of 1.21 m in diameter in both cases and 3.61 m long in case of the former, 6.27 m long in the latter. Reciprocating steam engines of 12,000 hp drove both. 12 Taking a 420-mm thick VH plate with the approximate dimensions 1,900-mm gauge, width 2,850 mm and length 2,160 mm (the latter was also the forging direction) and a weight after cropping of about 100 tons as an example the process of rolling and forging was as follows:
(1)   Heat in a producer-gas fired furnace (used for all sequences) in 32 hours to 1,200ºC, hold 10 to 15 hours.
(2)   Press from 1,900 mm to 1,550 mm. Then second press to 1,340 mm.
(3)   Heat to 1,200ºC in 25 hours, hold 8 to 10 hours.
(4)   Press to 1,100 mm.
(5)   Heat to 1,200ºC in 25 hours, hold 8 hours.
(6)   Roll to 850 mm (4,090 mm width).
(7)   Re-roll to 600 mm (width unchanged).
(8)   Relief heat to 650ºC in 28 hours, hold 32 hours, air cool. Then reheat to 650ºC in 28 hours, hold 30 hours, air cool.
(9)   Scale and scarf.
(10)   Heat to 1,200ºC in 25 hours, hold 8 hours.
(11)   Roll to 420 mm (still 4,090 mm wide and 6,500 mm long).
(12)   Relief heat to 650ºC in 20 hours, hold 20 hours, air cool.

Face-Hardening
While VC plates were carbonised (“ cemented”) to obtain a thin super-hard surface layer, 14 VH plates were face-hardened to attain a hardened layer of about 140 mm thickness in case of the 410 mm armor. This was accomplished by the following method:
(1)   The plate was placed, face up, on a bed of wet sand of about the same thickness as the plate. The edges of the sand and the plate were insulated by firebrick. The whole assembly was supported on two layers of steel plates between 76 and 102 mm thick.
(2)   One Pt-Pt/ Rd thermocouple was secured to the face of the plate; another inserted into a hole through the back of the plate and extended through 70% of the plate thickness.
(3)   A Siemens type reverberatory furnace, with recuperator equipment, fired with producer gas was brought to 1,100 to 1,150ºC and the assembly then charged into the furnace to heat the plate from the surface as rapidly as possible.
(4)   The plate was removed when the interior thermocouple registered about 730ºC (face had reached at least 850ºC) and immediately water-sprayed at the front and back.
(5)   The plate was charged with a concave curve so that the quench resulted in a more or less flat plate. However, when necessary plates were rectified at about 150ºC to relieve stress.

The face-hardening process resulted in almost uniform material structure from the front to the back including the centre layers, disappearance of the so-called Krupp disease (called temper brittleness by the Japanese) and other irregularities, increase of impenetrability and reduction of the production process to about 2/ 3 compared with VC armor.

Tests
Structural tests were conducted frequently at various processes of melting, casting, pressing, rolling, heating, quenching, etc. In none of these process cracking, webbing, strains, “ghosts”, etc. were permitted if they would affect the impenetrability of the finished plate. The carbon-gradient analysis (composition test) after the heat treatment in six depths was a special test of the VH plate. The main physical tests were (1) blow-bend fracture, (2) tensile strength, (3) Izod impact and (4) Charpy shock. After these tests and the measurement of dimensions, weight and, if need be, taper and curvature a few plates underwent ballistic tests.

VH Adoption for Economical Rather than Ballistic Reasons
Before the adoption of VH armor extensive ballistic tests were conducted, which indicated only a slight superiority of the VH compared with the VC in gauges from 330 mm to 430 mm, while thin plates, for example of 152 mm thickness, had even occasional inferior results. But this was meaningless for the IJN did not intend to use such thin face-hardened armor and although plates of 183 mm thickness were produced they served only for experimental purposes or projectile tests. When VH armor was finally adopted to replace VC it was for a number of economic reasons rather than ballistic ones:
(1)   To decrease the time cycle for production and, hence, increase the manufacturing capacity (It took about one month to produce one VC armor plate and this time was shortened to about half in case of VH armor. Thus, about twice as many armor plates could be produced with the same equipment and the costs decreased remarkably.).
(2)   To eliminate carbonisation materials and fuel consumption in the carbonisation process (mainly time and cost saving).
(3)   To be able to re-roll plates with certain types of defects, for example flaking, into thinner homogenous NVNC plates if necessary (NVNC and VH plates had the same analysis so that a VH plate could be changed at any time during or even after the processing [a very important economical factor]).

The maximum dimensions (l × w × thickness in mm) were 11,000 × 4,500 × 660 with a weight of 99.8 tons and those of a 410-mm side armor plate of the Yamato class 5,900 × 3,600 and weight 68.5 tons. The front shield of the main gun turrets provided particular problems. It consisted of four plates of which the two sheets at the centre (between the two outer guns) had a narrow width of only 2.5 calibres. It was supposed, that the huge capped AP projectiles would destroy these plates when hitting at about 0º. There existed no method to increase the thickness of the armor or to adopt a special shape to stop the projectile. Finally, the purpose could be attained with VH armor and the maximum possible production thickness of 660 mm.

 

Lengerer, Hans; Ahlberg, Lars. Capital Ships of the Imperial Japanese Navy 1868-1945: The YAMATO Class and Subsequent Planning: Chapters 4 and 5 (Kindle Locations 428-529). Nimble Books LLC. Kindle Edition.

Share this post


Link to post
Share on other sites
410
[R-F1]
Beta Testers
1,910 posts
7,133 battles
On 12/4/2018 at 11:37 PM, snakes3425 said:

The one thing Japan stuck to during the 20th Century was the idea of a single decisive battle deciding the outcome of a war, something they had done when they destroyed the Russian 2nd Pacific Squadron at Tsushima, and while Yamamoto and others advocated focusing on aircraft carriers as the way to win the war once it began, many still clung to that single decisive battle would win the war even when it became clear that the war was lost.

Thing is, considering midway is pretty universally considered the turning point of the war in the Pacific... Mahans theory wasnt completely wrong.

Just that the decisive big battle occurred between carrier fleets instead of battlewagons.

This is of course just referring to the naval aspect of the war; the island hopping campaign was a weird combination of blitzkreig style skipping of fortified Japanese positions (leaving em to wither on the vine as it were) and attrition fishing on select Japanese strongholds that couldn't be bypassed.

But in terms of naval battles, the war really was decided by a handful of major engagements.  (The Pacific war that is... The battle of the Atlantic was a completely different beast since Germany never even attempted to match Britains surface fleet as mahans theory would've required)

Edited by Shadeylark

Share this post


Link to post
Share on other sites
16
[VFW]
Beta Testers
54 posts
2,509 battles

This theory is slowly being reconsidered. Many people believe the slow attrition of the Solomon's campaign was the real turning point of the Pacific war. Midway was the first real reversal the Japanese suffered but they still heald a huge advantage in ships and planes after Midway. it was the Solomon's that killed off most of the IJN's pilots and where they lost many planes and smaller naval assets as well as some major naval assets as well. 

 

After Midway, the IJN was still very much superior to the USN but after the brutal, bloody attrition of the Solomon's, the IJN really could not challenge the USN for the rest of the war. 

Share this post


Link to post
Share on other sites
300
[JFSOC]
Members
972 posts
3,079 battles
11 hours ago, Vettish said:

This theory is slowly being reconsidered. Many people believe the slow attrition of the Solomon's campaign was the real turning point of the Pacific war. Midway was the first real reversal the Japanese suffered but they still heald a huge advantage in ships and planes after Midway. it was the Solomon's that killed off most of the IJN's pilots and where they lost many planes and smaller naval assets as well as some major naval assets as well. 

 

After Midway, the IJN was still very much superior to the USN but after the brutal, bloody attrition of the Solomon's, the IJN really could not challenge the USN for the rest of the war. 

The Solomon campaign is the turning point.  This is clear because of what the campaign achieved.

The Solomons became the first major staging base for the US in the Pacific.  Tulagi harbor, the Russell Islands, and Guadalcanal became a major forward base and supply depot that allowed movement to the next location:  Funafuti atoll.  That allowed conquest of the Gilbert island group (Tarawa) then movement into the Marshall islands.

The Guadalcanal campaign represents the point at which Japan could no longer mount a major offensive against the Allied forces and began a slow decline to defeat.

Share this post


Link to post
Share on other sites
361
[ZIPPO]
Members
1,589 posts
3,603 battles

I thought the Battle of Leyte Gulf was the turning point because it crippled their navy. Midway showed that we could not just win, but a major battle against the Japanese

Share this post


Link to post
Share on other sites

  • Recently Browsing   0 members

    No registered users viewing this page.

×