The Ship Model Forum

Revise the IJN? No plans to do so--what we have are based on Japanese sources. Would have been nice to see those samples, though, for comparison purposes and perhaps to add some colours.

Send you a bottle? At 25 quid?? I've sent you Battenburg cake, Indian chutney, and Marmite--all the staples of British life. You'll have to come here for the Welsh whiskey!

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John Snyder
Shady Grove Farm
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Agano class were the weakest and smallest cruisers commissioned by anyone during WWII. What useful cruiser like role they really could outstandingly fulfill is not clear to me. They were not much removed from large destroyer leaders. Hara may have thought highly of Agano simply because because he was by experience and temperament a DD commander, and in Agano class he found a ship that was almost destroyer like, and yet large enough to have avoided the crampedness and sea-keeping shortcomings of most destroyers.

Fukui was almost certainly speaking of the Agano's from a naval architect/design perspective, in which the design is tasked to a particular tactical/doctrinal role. In this case, yes, a DD leader role for divisional torpedo attack.

No doubt in hindsight that they were ineffective as the role they were built for was no longer viable late in the war. Fukui was not responsible for setting doctrine or tactics, just building ships.

It's interesting that they built turrets for the Vickers-pattern 6-inch guns left over from modernization of Fuso and Yamashiro rather than use a more effective and modern weapon. These were bag guns, after all.

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If an unfriendly power had attempted to impose on America the mediocre educational performance that exists today, we might well have viewed it as an act of war.

-- "A Nation at Risk" (1983)

That is undoubtedly attributable to the lack of industrial capacity or inadequate priority to produce enough new 6" barrels. The Japanese already has developed a superlative native 6"/60 gun, generally acknowledged to be the best 6" naval gun of WWII period, for the Mogami class. Guns of that design would seem to be easily the most obvious choice for the new CL had Japanese been able to deliver enough of them in time.

Which is interesting, because the 15.5cm mounts you refer to became surplus in precisely the time frame these ships were designed.

Who, by the way, besides a small number of Japanese officers would be able to evaluate or compare them with the properties of other 15cm guns? A gun, powder, and shell is a complex and dynamic combination. A few calculations on the back of an envelope are insufficient to qualify them in any way.

It appears there were 112 fully assembled guns and spares, only 30 of which were further employed aboard ships after rearmament; 24 were destined to swing uselessly at anchor for most of the war as secondary armament on the Yamato and Musashi.

The four Mogamis alone provided 20 surplus turrets. Eight more were in various states of construction when the order changed Tone & Chikuma from Class "B" to Class "A".

This strongly implies that the Japanese found some cardinal defect either in the gun or it's fire control system, and chose the Vickers 6-inch instead for these cruisers.

My suspicion is that these guns suffered from excessive barrel wear and projectile hammering, with a 3000 f/s muzzle velocity and 6 caliber head radius (a long) shell. It is also possible that these very long shells either tumbled in flight, or suffered severe dispersion. The USN had the latter problems for some time with the 8-inch/55 caliber guns until the shell head radius was modified and the muzzle velocity brought down.

In any event, the Japanese 15.5cm/60 only went to war on one cruiser, the "headquarters ship" Oyodo (besides the two Yamatos), and she at least never fired them in anger.

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If an unfriendly power had attempted to impose on America the mediocre educational performance that exists today, we might well have viewed it as an act of war.

-- "A Nation at Risk" (1983)

The 20 turrets removed from the 4 Mogamis during their upgrade were reserved for the 5 Yamato class. Their guns were therefore not available to the Aganos in 1940. Some of the guns meant for Tone were intended to be diverted to the Oyoda class, which were intended to consist of more than one ship and which were to be built at the same time as Aganos. Thus these guns were also unavailable. That leaves few if any of the installed guns available for any other use. Of the surplus barrels not immediately assignable to any triple turrets, at least a portion, if not all, must be held in reserve against barrel wear, accidents, for the 80 or so barrels clearly intended for installation.

So given the reservation already made for the existing 6"/60 guns' allocation at the time when Aganos were planned, the number of guns available is not sufficient to support what was intended to be a large class of ships to replace all 21 of the WWI era 5,500 ton light cruisers.

The ballistic properties of the Japanese 6"/60 is widely publicized and widely praised. It is not clear why fire control that might work with 6" Vickers would not work at least as well with these guns, which would feature much flatter trajectories. People far more knowledgeable than you do not seem to find it indecent to accept the excellence of these guns. Based on experience I do not believe you would be inclined to exhibit equitable skepticism were you to read good words about the guns of, say, Des Moine. I find it hard to believe that you would in that case quibble with:

Quote "the smallest cruisers commissioned by anyone durimng WW11".

Oh dear. Would somebody please respond to Mr GUest.

Not having any particular references handy, I am pretty sure the 3,750 tonne "Capitani Romani" class, "Condottieri" cruisers, British cruisers built to the general pattern of Leander, Gotland, are smaller than these Japanese cruisers. Even the Atlanta class are about the same size, with less length and more beam on about the same general displacement as Agano.

If you want to recall that the Akizuki class destroyers were briefly typed as "B"-type cruisers for AA defense, they would be much smaller.

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If an unfriendly power had attempted to impose on America the mediocre educational performance that exists today, we might well have viewed it as an act of war.

-- "A Nation at Risk" (1983)

I was thinking of the Didos' and the two 'toothless terrors".

Yes, of course...and the Tromps.

To make a further point, at least two of my references state the Agano class was to be fit with the 15.5/60, but this was dropped after a staff change in the constructor's office. There were a large number of complete guns and many turrets all sitting in warehouses just as the design for these ships was cast. It would have been an immense savings in design alone (at a time when draughtsmen were a critical resource) to use these "birds in the hand".

At least two of the turrets removed from the Mogamis wound up being fit as shore batteries at naval bases in the Home Islands.

I think there is building a fairly strong circumstantial case that the 15.5/60 was defective in some way (see my previous post on this).

Update: dispersion of the 15.5cm/60 was 278m at 20Km, much higher than the 20.3cm gun.

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If an unfriendly power had attempted to impose on America the mediocre educational performance that exists today, we might well have viewed it as an act of war.

-- "A Nation at Risk" (1983)

As indicated, all available 6"/60 guns and turrets, with margin for spares, were already earmarked for other projects currently in progress when Aganos were designed. The available 6"/60 turrets were in any case triples, and were therefore not substitutable, even in principle, with doubles of the same caliber. To design and manufacture double turrets for 6"/60 would require as much time, effort and material as doing the same for 6" Vicker pattern guns. To use the 6"/60 themselves for Agano could only be done either at the expense of the ongoing Battleship program, or by imposition upon the armament industry to make additional barrels. When seen in this light, using 6" Vickers were clearly a resource saving approach when viewed from the perspective of meeting the competing resource demands of the Japanese naval expansion ambitions in 1940.

I stand corrected. They displaced 6000 tons and were medium sized. But their armament of mere 6 6" guns, 8 torpedo tubes, and negligible AA firepower certainly is competitive in weakness to any smaller cruiser of their their era. As to their being a constructor's favorite, any constructor could lavish attention on things dear to his heart when he has to put so little armament on so large a hull.

Dispersion of 6" guns at longer ranges is expected to be much larger than that of 8" guns.

- Chuck

Even if we agree on the prospective future employment of 8 of the remaining 10 turrets (with the last 2 mounted as shore batteries), Oyodo's sister would have required a couple more, unless the decision not to build her was taken before the guns were made into shore batteries. I'll have to check LaCroix.

To me the evidence speaks to a gun with a demonstrably large dispersion pattern and very likely a short barrel life of 125-150 rounds. Satisfactory for supplying star shells in an engagement for Yamato, but not for an independent vessel.

The long-barreled, high-velocity, long-shell guns of several navies seem to have suffered similar problems in barrel wear, hammering of the lining, and tumbling shells.

Since the Vickers 6-inch in various marks was serving in cruisers of several navies for decades, it obviously was an eminently successful gun.

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If an unfriendly power had attempted to impose on America the mediocre educational performance that exists today, we might well have viewed it as an act of war.

-- "A Nation at Risk" (1983)

Since LaCroix refers to this problem being raised by the Japanese operators, it was probably much worse than they expected.

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If an unfriendly power had attempted to impose on America the mediocre educational performance that exists today, we might well have viewed it as an act of war.

-- "A Nation at Risk" (1983)

Japanese sources suggested that Musashi was painted with Singapore paint during her final sortie, and the distinctive lighter color it gave her may have been responsible for her being singled out for American attack. The sources indicated that painting of the ship in IJN was usually done at discretion of the captain and records of Musashi's activities in Singapore prior to Lyete has been lost. But survivors recall Musashi was painted in a silver gray that made her stand out from the collection of dark gray Japanese warships.

... as if her size wasn't enough? That's not a moon... that's a space station!

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If an unfriendly power had attempted to impose on America the mediocre educational performance that exists today, we might well have viewed it as an act of war.

-- "A Nation at Risk" (1983)

This comes from a friend of mine whose Dad was an Avenger Pilot on Essex:

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Tracy White -Researcher@Large

"Let the evidence guide the research. Do not have a preconceived agenda which will only distort the result."
-Barbara Tuchman

Not being able to judge her size is probably an indication of how long it had been since these pilots had practiced attacks on major naval units. Avengers would be in a better position to judge size than dive bombers, and the proximity of other units and land should have helped them to judge size.




The two ships at the extreme right show their characteristic Japanese heavy cruiser shape.

_________________
If an unfriendly power had attempted to impose on America the mediocre educational performance that exists today, we might well have viewed it as an act of war.

-- "A Nation at Risk" (1983)