Anyone interested in some intellectual exercise?

The Oyodo mounts looks a lot smaller in pictures, NavWeaps doesn't give data but speaks of a different hoist tech, I agree we need stronger AA protection for all our ship, introducing the bofors is one step in the right direction, one thing we should do as soon as convenient is remove the 8" from Kaga and Akagi, while that will not give us any more space for AA it will save us some tonns for stores and some space for accomodation and delete a vulnerable magazine, IMO we should probably just empty those magazine ASAP without waiting for a dockyard slot. As more long ranged destroyers equipped with the type 93 join the fleet we should probably gradually remove the torpedoes from the heavy cruisers in favour of more AA, this wil cost us some tubes when the big surface engagement we are planning for eventually happens but will help a lot in the air based attrition phase that will preceed it, having that much unprotected explosive on a 13.000t ship is a risk. I would leave them on the flottilla leaders though.

 

could the 8" mounts be replaced with AA?

 

I agree with TOS. The "Oyodo" mount is a shielded, open-backed pedestal type, similar to the twin 5"/40 which we know can be mounted easily in place of the 5.5". The Akizuki mount is a base-ring type with handling room below and would be a significant structural alteration, for only a slight improvement in performance.

Side note, our designers and ordnance staff have reverted to the 5"/40 for the next cruiser and carrier designs, Ibuki and Unryu; apparently they're not totally convinced of the superiority of the 3.9".

While it's tempting to slap on as many barrels as possible, the key constraint might actually be ammunition supply. The 3.9 shell is about half the weight/volume of the 5.5, but for AA we'll want at least 2-3 times as many rounds per gun, on top of which we propose to increase the number of barrels. And there are all those 40mm as well. There will be some ready-use ammunition on deck, but most of it will have to be stored in the same magazine spaces that supported seven 5.5" and two 3". It might actually be more useful to start by calculating the amount of ammunition a ship can carry and then determine the optimum number of barrels to discharge it at an appropriate rate, keeping in mind that we don't want to fire it all off in the first few minutes of a battle. Of course if we do reduce the number of gun mounts, we'll keep the ones with the best arcs of fire.

I would definitely work in a second Type 94 director aft, even at the expense of a gun mount. The catapult pedestal might be a suitable location, especially in the Kuma or Nagara classes, assuming we remove the tripod mainmast.

 

could the 8" mounts be replaced with AA?

Not literally; they're in casemates low in the ship, but the weight savings would facilitate other additions, and the gun crews could be reallocated to AA weapons.​

 

Both you and TOS were indeed correct. I went back and looked at the original source(s) I had used and they did indeed give the impression that the Oyodo used Akizuki type mounts. I have always had great respect for your, seemingly, encyclopedic knowledge of all things naval. I figured that you were probably correct and the information I had was incorrect. I then went to NavWeapons, a site I regularly use and one I feel is a pretty good source. They did not specify that there were two turret types. They did mention that there were two hoist systems, but only gave one turret weight and I was certain an open backed pedestal mount did not weigh the same as a turreted, enclosed base ring mount. I checked other sources, Pacific War Online, Hyper War, Combined Fleet and on and on. I looked at pictures. None of them specified, just said both ships (and others) used the same gun. Normally the phrasing was, "These guns are the same as that carried by the Akizuki-class destroyers.." I was sure that you had a source that stated otherwise so I kept looking, I finally found my answer at a model ship site that showed both types of mount. Proving that, as I suspected, you were indeed correct.
I had planned for handling rooms and incorporated the necessary structure in my suggested modification. I located all turrets near the extant magazines and figured we'd just need to swap out the hoists. The A and Y turrets, because they were not located on any type of raised structure would of necessity have to have their handling rooms located below the deck. I had planned for compensating for this by adding additional spaces in the two deckhouses I added. (1st reason I saluted your post, your impressive knowledge on the subject).

I had calculated the difference in volume and weight between the 5.5 and 3.9" rounds. I located the mounts near extant magazines, I planned for handling rooms and hoists. Even crew accommodations. What I did not account for, and it was a stupid mistake, was the difference in the number of barrels. I was thinking number of mounts when I should have been thinking in terms of the number of tubes. Dooh! Smack my head! Thank you for pointing this out. (Second reason for the salute, a very astute observation on your part).

I did plan to do this. I hadn't finished the concept yet. I still needed to add it, 20mm mounts and life boats. Just haven't calculated how much weight I still have to spare.

 

Well, Bobimoto-san, you've certainly done your homework! I thought it odd that navweaps did not state clearly that there were two different mountings or give complete information about both, but these notes from that page address the differences between them:

3) Akizuki class used two dredger hoists to supply ammunition to the working chamber. From here, rounds were manhandled to loading positions for pusher hoists, one for each gun. At the top of the hoists, rounds automatically rolled to waiting positions where shell passers handed them to loaders standing on the gun platform, which moved with the guns. Fuze-setting machines were attached to the breech faces of the guns. Loading trays were manually operated.

4) The Oyodo class used four bucket hoists which delivered ammunition from the magazines to a working chamber abaft the No. 2 15.5 cm (6.1") gun barbette. The maximum rate of supply was 20 to 22 shells per minute per hoist. The ammunition was then carried by hand to the 10 cm (3.9") gun mounts, which were 77 and 135 feet (22 and 41 m) further aft. There were ready-use ammunition storage lockers near the weapon mountings which allowed for a higher rate of fire for a period of time. The fuze setting on this class was done by a separate machine before the shells were loaded into the gun.

Of course it would be possible to install the base-ring mounts on our old cruisers, just more work. Our attache in Washington reports that the Americans are doing something like this, installing their 5"/38s on the British cruiser Delhi in one of their shipyards (those Americans seem to have an odd interpretation of neutrality). The RN themselves did a simpler installation on the C class, replacing their 6" guns with twin 4" rather similar to our Oyodo 3.9s. My thought and I think TOS's is that that would be the example for us to emulate.

Look forward to seeing your final product!

 

Thank you. I guess my next step is to try and find ship plans to see if there is additional internal space that can be reasonably, and efficiently converted to additional magazine space. Based upon your and TOS's suggestion, if I can find the additional internal spaces, I will at the very least propose we change the A and Y turrets to the shielded pedestal type. The weight savings there can be applied towards the additional gun director. The A and Y turrets can be serviced out of the upper handling rooms for the B and X turrets, just need to add an additional hoist and a properly located pass through. I had read the NavWeapons description of the two different systems for supplying the guns with ammunition that you quoted. The Oyodo system struck me as particularly inefficient.


Some things I'd like you to ponder, so we can make use of your knowledge (a valuable resource to us).
1.) AA upgrades for all our combatant naval vessels. There are the pre-defined upgrades that historically occurred. We are not limited to that. What would you like to see done?
2.) The Akizuki was a very good AA escort, but was quite large. The size and displacement approaching that of a light cruiser. Length 440'3", Beam 38'1", full load displacement 3759 tons. Japan only managed to produce 12 of them. Though a very capable AA ship, I think we need something smaller that we can produce more of. Instead of the 4 x 2 3.9" (8 barrels)mounts of the Akizuki's, cut one and you'd still have 6 tubes which would be comparable to a US Fletcher class DD, 5 x 1 5"/38 (5 barrels). We could produce a perfectly functional, general purpose DD on a size and displacement similar to a Fletcher. The Fletcher's had a length 376'6", beam 39'6" and 2500 tons full load displacement. According to the NavWeapons site the 3.9" twin (I'm assuming base ring) mount weighed in at 76,060lbs or for three mounts, 228,180lbs. I'm not sure of the thickness of the steel for the Japanese mounts enclosure which makes exact comparisons impossible. The US 5"/38 Mk 30, single mount varied from about 41,400 lbs. for 1/8th inch thick protection to 45,600 or 45,700 lbs. for a 1/4 inch protected type. We'll go for an average of 43,550 for illustration purposes. In that case the 5 mounts on a Fletcher weigh in at 217,550 lbs. (if you use the quarter inch thickness enclosure, it comes out to 228,500) which is very close to what the three 3.9" twins would weigh. So theoretically, from a main battery weight perspective, we should be able to do it. We should also be able to give it a decent medium AA battery, and decent ASW weapon fit on that size and tonnage. Your thoughts? (When pondering this I thought the layout should be A mount 3.9" twin, B mount ASW mortar, (possibly two but need to find out what size working circle they require) X and Y mounts would be 3.9" twins.

The 5"/38 data I got from this source: http://www.hnsa.org/doc/guncat/index.htm#toc
This is a great web resource and anyone interested in WWII US Navy gun mounts should bookmark it.

Let me go off track for a moment to make what I think is an important point. The militaries of many countries are criticized for always training to fight the last war. We might be falling into the same trap. We have placed much planning into correcting what Japan could have reasonably forseen with the knowledge they had at the time. We can't erase what we do actually know so we have been veering towards preparing to re-fight the Pacific War of 1941-1945, based upon how the US historically fought us. We might need to push our thinking more outside the box. There is a very good chance the strategy or application thereof, will change markedly. We're not attacking the US surface fleet, how will this intact asset effect the US strategy? Historically, during the Guadalcanal campaign there were old US battleships sailing up and down the west coast that couldn't be forward deployed because the US Navy lacked the tankers, to ship the fuel, to adequately support them if they were used. This despite the fact that the US found itself in extremely desperate straits during the campaign. What if our change of focus towards using our submarines against logistical shipping takes a few extra tankers out, causing the fuel situation to be even worse? I think, we as a group, need to broaden our planning to incorporate alternate US strategies, possibly quite different from those that were historically pursued.

3.) The old Fuso and Ise class battleships. Fuso, Yamashiro, Ise and Hyuga. I think they should be used to support our initial offensive, but what then? Historically, after Midway they looked at converting them to hybrid battleship/carriers. The Japanese went with the Ise class because they had a slight speed advantage and Hyuga had a turret explosion that had never been repaired. They had their rear turrets and barbettes removed, a short flight deck added and shipped 22 aircraft, including D4Y's. They did not prove successful, partly due to a lack of aircraft and pilots. Was the concept itself bad, or did they just not take it far enough? I've never been a fan of the conversions, but recently re-evaluated the concept. We've addressed the pilot/aircraft issue and hopefully will have adequate numbers of each. The ships are of limited utility as battleships. The addition of the flight deck does make them formidable escort vessels, but they are not efficient in that regard. Based upon the most likely threats our shipping will face (submarines and aircraft) and having high fuel and manpower requirements, they are not an efficient use of resources. If the US adopts a surface raider tactic they would be useful. My question is what if we went even more radical and deleted the two midship turrets so we could have an even larger flight deck? One big enough to actually be useful. What if we shipped double the air complement? The remaining two, forward, twin 14" turrets and armor would still be enough to scare off most surface threats. What if we outfitted them with increased C & C capabilities, so they could serve as the flagship of a new specialized type of task force?
If it's possible to make such a ship and I haven't looked at it in more than a cursory manner, they could prove useful in a number of roles.
1.) Use as "Jeep" carriers to ferry replacement aircraft to the real carrier fleet. The magazines for the big guns that have been removed, might also be useful for transporting ordinance for replenishing the Kido Butai in a pinch.
2.) Use in concert with a squadron of DD's, 1,2, or three AV's and support with an AO and AKE. Park at some undeveloped atoll, or island, and use to monitor gaps in our defensive perimeter. The AV's would support large, long range search aircraft (flying boats), medium range float plane search aircraft and a few float fighters for local defense. The BB/CV could, depending upon the mission ship strike aircraft, fighters or a mixed complement. How different would the Doolittle raid have been had a similar type of task force had detected their approach? What if 24 dive bombers and escorting fighters, from one of these conversions, had struck the Hornet with the B-25's on her deck?
3.) Using the same makeup and parking in different areas, fly ASW missions in areas not well covered by land based air. Move regularly to keep the enemy sub forces guessing as to what areas are safe hunting grounds. Use the attached DD's to hunt contacts.
4.) Use to provide intermediate air support in areas like the Solomons. They could again park in areas not easily supported by developed air bases. Provide reconnaissance of the enemy and use their air and DD compliment to attack shipping. Cover the withdrawl of damaged ships from the area of operations. Just think how different things would have been if SBD's from Guadalcanal hadn't been able to hunt up the slot during daylight for damaged or approaching convoys because fighter cover could have been provided from a closer location. Ise had a Type 21 radar fitted prior to Midway and Hyuga a Type 22. Use them as early warning assets also.
5.) Again, use the same type TF parked in areas where they are unobserved. Have the AV's use their flying boat aircraft to recover downed pilots and the fighters from the CV/BB to protect them. What if our attrition of highly experienced pilots can be greatly decreased?

Not saying this is a correct expenditure of assets, that the conversion is feasible or that the concept is what we should do. I do think it is the type of out of the box use of our assets that might make a difference.

I'm now donning my Kevlar and Flak Jacket and await the return, incoming.

 

I could see them being converted and possibly being of use in the South pacific or in the Indian ocean.

 

What a nice quiet bunch of guys must the IJA be! No need for you to wear the Kevlar and the Flak jacket! we only lay some mines out if you won´t give us our toys LOL!

 

Outside the box? More like down the street, into another building and up 3 flights of stairs!

We must ask ourselves a few questions.

When would these ships be ready from conversion? Late 1943 or early 1944?

How many do we convert? 2 or all 4?

How will this affect their AA defence with half to 2/3's of the deck devoted to flight operations?

Will they act as cannon fodder to roving enemy carrier groups looking for an easy kill?

Will we find ourselves needing to add light/escort carriers to protect these units because we underestimated the threat to them?

How does this affect our base strategy of aggressively contesting enemy landings with counter landings/re-inforcements? Will we miss the weight of fire they can provide?

If our fuel situation becomes critical, with they become the ultimate 'white elephant's' of our fleet?

What do we do with the spare turret's and guns?

How much will this cost in resources, slipway usage and time?

My comments have been critical, but I would support a feasability study on the matter.

Prime Minister

 

Depends upon when we start them and how extensive the conversions are. I don't think we should consider the conversion until we have reached a point in our offensive operations where they are not needed for naval gunfire support. If one or more are damaged during our initial operations they should be the ones selected for conversion. In real life the Ise took 168 days to convert (23 Feb-10 Aug 1943@ 5 1/2 months), Hyuga took only 140 days (01 Jul-18 Nov 1943@ 4.6 months). That should give you a general idea.

I'm not convinced it is a good idea, just throwing ideas out there. If we did decide to do them I'd suggest two. Then if they prove valuable, do two more.

This is an area I would go more extensively into for modifications. IRL, the ships had to have a lot of concrete added aft to made up for the weight lost when the two after turrets and barbettes were deleted. We'll be deleting 4 turrets and four barbettes. I'd suggest first of all, add more storage tanks for AVGAS to make up some of the weight. Next add sponsons to support med and heavy AA mounts in line with where the turrets were. Add elevators, associated machinery, whatever we need to use the weight advantageously. Add an armored hangar deck. We'd need to look at it in more detail. There is so much weight we'd need to use if we are creative we could mount a very heavy AA suite.

I'd say we use them behind and as a reinforcement to the front lines, not as offensive frontline units. Ise and Hyuga got early radar sets (May '42 and later E-27 detectors) and paired with AV's to support sea-planes they'd be useful for early detection of enemy incursions. I'd use them and their associated task forces to cover gaps in our lines or in rear areas where we want to concentrate additional ASW assets. If a roving carrier group did find them, they'd likely be behind our lines. If struck first, the BB/CV's would have enough ass offer some degree of defense and to hurt the enemy in a return strike. It is more likely with the TF's robust scouting assets that they would sight the enemy raiding force first and we could get in a first strike and vector additional assets to strike them as they were fleeing.

No, if this is the situation we were to find ourselves in I'd pull the hybrid's back to Japan and use them to train carrier pilots. We do have a need for training carriers.

I don't think so. In fact this is an area I had not considered before you mentioned it. I would think that if they were equipped with fighters they could provide cover for the invasion fleet and naval gunfire in support of the landings. If they carried a compliment of attack aircraft they could provide naval gunfire and close air support. Or I'd drop the AV's on the side of the invasion area opposite of the possible avenues of approach by enemy forces. The CV/BB's and their destroyers could then be placed in an area between the invasion fleet and the avenues of approach that an enemy response would most likely come from. They would interpose themselves between the vulnerable invasion ships and any potential enemyforce, covering the most likely avenue of approach and using it's destroyers, it's strike aircraft, it's fighters or even their own big guns to interdict enemy response.

Park them in Japan and use them as training carriers.

Shore batteries.

The amount of resources would be tied to the final configuration we decided upon. They'd be converted in naval repair yards and wouldn't interfere with our regular building plan. For the first six to eight months we should have plenty of excess capacity. Once our expansion slows down we'll need to return our carriers and frontline ships for yard periods, repair, overhaul, upgrades etc. If we did the first two early enough we'd have them back in service before we hit that mark. Worst case scenario we do any hull work that might be required first so if we do need the yard space we can suspend the work on them, remove them from drydock and restart work once capacity again exceeds need. At worst it would result in a couple days delay before we could start work on the incoming ship.

I didn't take them as anything, but asking the questions that we need to ask concerning all ideas. As I said, I've never been a fan of the hybrids as they were converted and until the other day never considered how they might have been used if a more extensive conversion was done on them. I'm not even convinced that it is a good idea myself. I do think we need to throw all ideas out there because one of them might be the answer to one of our needs. I would encourage all council members to do likewise, if it turns out to be a bad idea no harm done. If it is or can evolve into a good idea we need to pursue it.

 

One of the things that bothers me about the whole idea was that several early carriers were built with 8" guns such as Lexington, Saratoga, Akagi and Kaga. I always thought this was a fairly dumb idea since they were so lightly armored and filled with combustible AVGAS. Apparently, early naval planners thought it was the right idea at the time, though WWII proved otherwise. Now with the Fuso/Ise potential conversions I seem to be moving along a parallel path. I've been arguing back and forth with myself, "this is a stupid idea", "no it could work", "you're better off building a small carrier", "but this will only take 6 months vs two years or more for a CVL", "it can't operate with the fleet", "it's not intended to operate with the fleet". And on and on. Hope this internal discussion doesn't cause my personality to split.

 

OK, which Bob is typing now?

It doesn't hurt to study what a longer flight deck/more aircraft might offer, still used as training carriers, as they might be forced to do, is a very expensive option compared to Escort CV's in reguard to escort/fuel.

 

Let me take your idea and take one further step into crazyland.

Don't we have two CVL's soon to enter service with fairly slow speed's in the 22-25 knot range. Admiral Karonada has favored them for use with the Kido Butai due to their large (50 each) air compliments, while I favored them for training/escort duty due to there slow speed.

If we can extend the hanger/deck to allow each BCV to operate 40-45 combat aircraft each, then merge both these slow CVL's with the BCV's we could have a fairly large carrier group (admittedly slow, but nearly 200 aircraft) that has its own big gun protection and C&C suite.

If the rest of the council thinks I going mad, I'm blaming Col. Bobimoto and the bottle of sake he gave me.

 

They could operate together the Ise class after conversion were good for 25.3 knots and had a range of 9500 mi. The Fuso's would probably be good for 25.5. The two carriers you are referring to are Hiyo and Junyo, converted passenger liners. They can make 25.5 knots, have a range of 11,700 and do carry an aircraft compliment of 48-53 aircraft each. I don't see why they could not operate as a second strike force when necessary.

 

I would see them operating out of Truk or some other forward base. In slack periods they could cover those 'dead spots in our coverage. I would place pilots with limited deck time (say just off MAC's or CVE's) on board to gain even more training while covering these spots (help's fill the training void and makes your PM happy). After a period here they could transfer to our fast carriers or return to the reserve pool to tap as needed.

If we need to repel an enemy incursion they could act as close support or in conjunction with our Fast CV's as Admiral Karonada feels appropiate. This would allow our Fast CV's to operate to their full potential speedwise in all situations and not be tied to convoy protection of some counter landing.

Of course this is all speculation.

 

What I'm looking at is something to fill the gap until we get additional purpose built fleet carriers into commission. We need the extra strength during our expansion phase, because once the US starts commissioning large numbers of new carriers in 43 we will need to go over to the defensive. We hold the advantage early with Kido Butai and it's six carriers, Akagi, Kaga, Soryu, Hiryu, Zuikaku and Shokaku. We have the CVL's Ryujo and Zuiho that can operate with Kido Butai if and when we need to pull one from service for repairs/overhaul etc. We'll be gaining an additional CVL Shoho at the end of November. Junyo and Hiyo are scheduled to commission in May and June '42 respectively. Their speed makes them unsuitable to operate with Kido Butai, but their air compliment makes them more capable than the CVL's. I would suggest to the Council that we allocate additional resources to hasten their completion. The only other carrier we have building is the Taiho laid down on 10 July of this year. I support Admiral Noka's suggestion that we immediately lay down two more Shokaku's and as soon as we have some additional capacity another Taiho. We have a number of ships that can be converted to CVL's, but I think they will be of only marginal use because of the hulls we would be converting from, mainly auxiliary types. If we are going to go forward with CVL conversions I would suggest using cruiser hulls so the resulting ship is more capable as a war ship. CVE's are another matter, since they will be used in ASW work, supporting amphibious operations and ferrying aircraft, and will probably not be involved in fleet actions, a merchant hull should suffice. One of the reasons that the old BB's are intriguing is that they should be able to absorb some level of damage and survive to fight another day after repairs. I'm just not sure the type of conversion I've mentioned is feasible. One of the strangest things when looking at this is that I have to look at adding a lot of weight when normally I'm looking for anyway possible to cut weight. This is due to the enormous weight of four turrets and their barbettes.

 

In speaking with the esteemed Lt. Wiki I understand there are some plans for converting the Ise and Hyuga into true CV's with about 55 aircraft each operational. The cost and time however, considering the end result seem a rehash of a single hanger Shinano which we all do not favor (though a double hanger version would be acceptable).

Your estimate of 5 months for the limited hybrid would seem to indicate that a full hybrid (as far as the funnel) would seem to indicate a 9 to 12 month conversion period, as though removing turrets are fairly easy, the barbettes and aft superstructure are considerably more complex and time consuming.

If this is the case and we wait until our initial actions have run their course, then these ships could not enter a naval repair yard till approximately 6 months after start of hostilities, another 9 to 12 months to effect the conversion and perhaps 3 months to work up ship and aircrew.

Would this not place their availabillity only about 3 to 6 moths earlier than a new construction CV's? If we have greater than expected damage to operational ships or if the weight issue proves troublesome to solve they might enter service at the same time as our new CV's. It would seem that this course, while usefull for other reasons, could not help us bridge our CV gap in a meaningfull way untill the arrivial of our new construction.

Prime Minister

 

One important factor is to try to fight in the south pacific where our land air advantage can fill in the gap.

 

I am in full agreement Steve. Which brings us back to our earlier discussion on the Noumea Operation.