WI/AHC: Ise class battleship converted to AA-Battleship

[Thomas27]

OTL after the defeat at Midway, IJN decided to convert the Ise class Battleship (Ise & Hyuga) into hybrid carrier-batteship. That make theme pretty inefficient in both role.
http://en.wikipedia.org/wiki/Ise-class_battleship#Conversion_to_hybrid_carriers

But what if before before the convertion is to advanced IJN decided to convert them to AA-Battleship?

Instead of building a flight deck on the stern, they build a massive AA nest.
They keep the Type 13 & 21 radars.

Which type and how many canons would be needed to make Ise class massives and efficients AA Battleships?


Thanks to all people who gonna help me.

 

[Rubicon]

They're to slow to be of a use to the Kido Butai. You'd need to rip out the entire interior and replace the boilers, which is a 3-4 year long job to make either the Ise or the Hyuga usable with the carriers.

 

[sharlin]

The thing is the IJN's AA guns were shiiiiiiiiiiiiiiiiiiit. Only the dual 3.9 mounts on the Atizuku's were any good but they were in short supply and high demand so getting them would be a problem.

This means you're then filling the ass of the ship with the standard IJN fallback the Type 96 25mm gun. And this was a horrid mounting. At the end of her career the Yamato featured 162 barrels and in that battle is credited with 10 kills between her and her escorts. And thats not counting her 5 inch DP guns that were used as well.

The Type 96 is a terrible AA gun, it had a small clip and had to be manually loaded, it fired a small shell with a rather low range (effective range of about the same distance as a dive bomber releasing and pulling out of its dive) and the mounting itself trained and elevated too slowly. The vibration of the guns firing was so severe that the loaders had to lean on the magazine to stop it jumping out of its position and due to the size of the clip there was problems there as well. In a dual mount for example the tactic was to fire one barrel, reload that one and whilst thats being reloaded the other barrel is firing to keep up the volume of fire. Also the massed mounts would have had little director control save a senior pointing with a white stick at a target. Even when the Japanese had hundreds of them lining ships decks they were of little use.

You'd need the IJN to have an equivalent of the 40mm bofors for an AA battleship to have any real use.


In this clip

https://www.youtube.com/watch?v=D7tzNfSGEnU

you can see the 25mm's in operation and the movie folks doing this film actually rebuilt them to factory specs as well as looking at the training etc, so what you're seeing is as real as can be made now. Of course the gunners shoot down more aircraft than the USN lost that day but thats Japollywood(?) for you. As I said you can see the loaders leaning on the magazines and you can see how many crew they used which is a HUGE amount, you've got the gunnery director, 6 loaders, and 2 gunners, per mounting.

 

[Rubicon]

You'd need the IJN to have an equivalent of the 40mm bofors for an AA battleship to have any real use.

The Bofors is unfortunatly highly overrated as a naval AA gun. To low ceiling and the caliber is to small to use proximity fuses.

 

[sharlin]

The Bofors is unfortunatly highly overrated as a naval AA gun. To low ceiling and the caliber is to small to use proximity fuses.

True but its still better a gun than the turd bucket that was the IJN's 25mm gun.

 

[Scotty]

They're to slow to be of a use to the Kido Butai. You'd need to rip out the entire interior and replace the boilers, which is a 3-4 year long job to make either the Ise or the Hyuga usable with the carriers.

I cant find any details of their speed after carrier conversion (they were 25kt as battleships) but they did serve with Zuikaku, Zuiho, Chitose and Chiyoda at Leyte and they're all 28+ kts so the KB must have thought they were an acceptable speed as BB/CV hybrid

Anyone know just how fast they were after shedding all that weight off their arses (or whether the removal of the turrets/ barbettes and addition of flight deck, planes, stores - and the 8 inches of concrete evened things out))

 

[sharlin]

I don't think it altered the speed much, they had to add so much concrete to counter the loss of the weight of the two turrets that it basically was the same weight. Its also very likely that they never carried aircraft in their re-designed role and basically served as bomb/torpedo bait and AA batteries.

 

[Rubicon]

True but its still better a gun than the turd bucket that was the IJN's 25mm gun.

If you use the Type 96 as the standard then all AA guns are better

... even Italian 20mm ones....

 

[sharlin]

The italians had some good guns, their 90mm AA gun was very advanced for its time whilst their 15 inch rifles had mad high muzzle velocity and by all accounts were accurate weapons.

 

[Rubicon]

The italians had some good guns, their 90mm AA gun was very advanced for its time whilst their 15 inch rifles had mad high muzzle velocity and by all accounts were accurate weapons.

Oh absolutetly, the 90mm was about as good as the German 88mm L/56, it's main problem was the carriage wasn't as versatile as the German one. I was talking about light AA guns, sorry if I wasn't clear enough.

 

[Thomas27]

I don't think it altered the speed much, they had to add so much concrete to counter the loss of the weight of the two turrets that it basically was the same weight. Its also very likely that they never carried aircraft in their re-designed role and basically served as bomb/torpedo bait and AA batteries.

Even with all the things they to ships OTL they were 2.000 tons lighter.

 

[sharlin]

*nods* I was talking about the 90mm guns on the Littorio class battleships, probably as good in terms of raw performance as the USN's 5 inch but with a smaller round, of course the FCS was nowhere near as good and no proxy shells.

The Type 96 was just a bad design and the IJN stuck with it even though they had captured examples of 40mm guns in Singapore because it was simply too difficult to swap over production to a different gun (understandable considering the resources that would nom up, resources the Japanese didn't have to spend really) so they stuck to their 25mm guns and just went MOAR! when it was obvious that they sucked, going for more and more volume of fire.

2k tonnes blimey, you'd probably still not see much in the way of speed increases, maybe half a knot or so and them being a bit more nose heavy when at speed.

 

[Rubicon]

I cant find any details of their speed after carrier conversion (they were 25kt as battleships) but they did serve with Zuikaku, Zuiho, Chitose and Chiyoda at Leyte and they're all 28+ kts so the KB must have thought they were an acceptable speed as BB/CV hybrid

And neither was present as Marianas, that ought to tell you something. Good enough to use as bait, not good enough to use in a full blown carrier battle.

Like I said, to slow, to old and without a mission.

If converted to AA platforms, best usage would be to use them as a floating battery in an important port.

 

[sharlin]

If I recall from Shattered Sword, post Midway the IJN had a doctrinal idea shift to basically put large capital ships out in front of their carriers to act as an early warning for the carriers, an AA trap and bomb bait. I suppose if you was willing to chug along at 25 knots with the Ise's in front then they could serve this role. Its basically what they did with the carriers when they did sail with them, they were HEY! BOMB ME! NOT THEM! TARGET HERE distraction carnifex's.

 

[Richter von Manthofen]

MY sources say they were 23,6 kts max speed as built and modernisation increased speed to 25,6 kts. When they were rebuilt as carriers the number of 12,7cm Flak was increased (8 to 16) and in the end they had up to 108 2,5 cm Flak + 6 Multi AA-Rocket launchers. But they never carried the 22 assigned Divebombers (lack of planes/pilots).

Basically the WERE built as AA BBs (sort of) and the "official role" as dual purpose BB/CV was never tested.

the Iowa class in comparison had 20 12,7cm (5") DP + 80 40mm Bofors + 49 20mm oerlikon - on a much larger ship of course. In this regard the Ise's were "not bad" AA-ships, but as was said by otehrs gun quality also counts .

 

[Rubicon]

If I recall from Shattered Sword, post Midway the IJN had a doctrinal idea shift to basically put large capital ships out in front of their carriers to act as an early warning for the carriers, an AA trap and bomb bait. I suppose if you was willing to chug along at 25 knots with the Ise's in front then they could serve this role. Its basically what they did with the carriers when they did sail with them, they were HEY! BOMB ME! NOT THEM! TARGET HERE distraction carnifex's.

Anything conjured up by the Japanese after Midway I always find suspect, to but it bluntly they paniced.

I did an exploratory investigation of capital ship construction earlier here and for example the cost in matieral and time it took the Japanese to finish the Shinano as a bad carrier, they could have gotten the Shinano finished much earlier as a battleship AND an Unryū-class carrier.

 

[johnboy]

Even with all the things they to ships OTL they were 2.000 tons lighter.

Actually I think you will find their tonnage was much the same, deep load was actually more. In addition, their machinery was not as thoroughly overhauled as on 1935-7 so they would likely be slower than 25 knots

 

[Andras]

The 40mms were the most effective AA weapons the USN had, getting 33% of all a/c shot down in sight of a ship. 20mms accounted for 28%.

5" common and 5" VT both scored 15%, so that would be 30% combined for all types of 5".

3"/50, 1.1" and .50cals are all in the single digits.

http://www.history.navy.mil/library/online/antiaircraft_action_summary_wwii.htm#II


The IJN also lacked a director for their automatic AA. The USN even had lead computing optical sights for the 20mms.


This is a great personal history of an officer involved in the USN antiaircraft program, from the training command to shipboard service.
http://www.ibiblio.org/hyperwar/USN/rep/DamnNeck/index.html

 

[sharlin]

The main thing is that the USN had the perfect storm with the 5-inch gun and the Mk37 FCS especially when they introduced proximity shells. The Bofors may have an inflated reputation but its probably still the best medium caliber AA gun of the war, its better than the Japanese equivalent or the RN's the 2lb pom-pom and the Germans had the 25mm flakverwlraiajghahghab or what ever the hell it was called as well as the Bofors (the Germans 37mm gun was a turd).

It was a quantum leap over the 1.1-inch the USN used beforehand.

The Bofors was reliable, it fired a decent sized round at a good velocity and could pritty much be mounted anywhere that there was deck space as it was non intrusive into the hull. Add to this 20mm guns as well and then you add that lovely dose of cinamon with the USN's doctrine.

The IJN in battle would have its ships very far spread out, each ship defended itself and manouvered independently. A destroyer could be 8000 yards away, cruisers further still and their main defence was always viewed as being the helm. Hence this.

carriers doing doughnuts.

The USN's doctrine had all ships move under the control of the ship they were escorting. They would form a tight ring to max firepower and move as a unit. This greatly increased the volume of fire and the USN also stressed that use of the helm for radical manouvers was not needed unless to dodge torps or dive bombers in their final run.

Throwing a ship around the place like the IJN did utterly wrecked any fire solutions you have and basically reduced the AA guns to a case of 'FIRE EVERYTHING IN THE DIRECTION OF THE ENEMY!' no box barrages or anything, just point guns, spray, pray.

The USN's doctrine was the creamy topping to their AA guns. The IJN's doctrine was a poo pavlova. It looks great...but its still filled with shit.

 

[Rubicon]

The 40mms were the most effective AA weapons the USN had, getting 33% of all a/c shot down in sight of a ship. 20mms accounted for 28%.

5" common and 5" VT both scored 15%, so that would be 30% combined for all types of 5".

3"/50, 1.1" and .50cals are all in the single digits.

20, 25, 37 and 40mm AA guns are great as deterrant against fighter bombers. Occassionally they may even down a few attacking planes, that's great - if you are stuck on land. On a ship most attacks will be either by dive bombers or torpedo bombers both of which if you focus on using small-calibre AA guns will have a very narrow timespan in which to hit and more importantly kill the plane with.