Anyone interested in some intellectual exercise?

We're looking at 25 November as the date we will initiate hostilities with the British and Dutch. Initial landings 25 November and follow-up during the next week. We won't need these ships after the initial landings. Support can be provided by land based air and cruisers. If we look at early December as the date for placing them under conversion and I'm guessing closer to 8 months for the conversion, then were looking at re-commissioning in late-July early August '42. Since we'll be getting the CV(a)'s you mentioned in May and June '42 add the first two BB/CV's in August and we'll have a respectable backup force. Taiho which has already been laid down will commission on 7 March '44 (historically) though we can probably accelerate her completion to a small degree. The two Shokaku's if we lay them down immediately, will not commission until around the fall or winter of '44. Again we can probably speed this up to a degree, but probably won't get them before early '44. This leaves a huge gap. If we go with the Unryu's and lay them down immediately instead of in mid-42 as happened historically, we're still looking at the end of '43 and early '44 before they commission. If a study of the BB/CV hybrid proves the feasible we could pull two and start work immediately which would cause them to enter service in mid-June '42. That leaves a year and a half gap at best, if we go with the Unryu's. (I didn't figure in work up time as you did because it should wash with similar time required for either ship type). We'll have to keep Kido Butai busy for the first six months at least, we'll need to keep the better part of it active as a deterrent to US carrier counter strikes. The ships will be tired and in bad need of refitting. We need to have something in reserve, even if it is less capable to address potential enemy actions.

 

AA upgrades for all our combatant naval vessels.

The main improvement I envision is the installation of 40mm Bofors guns, at least two twin mounts on destroyers and eight on heavy cruisers and larger. Quad or more mounts would be useful on the larger ships if we can devise an arrangement that allows ammunition clips to be fed to the guns; they need a clip about every two seconds (I'm trying not to just duplicate everything the USN did). Up to about sixteen barrels I'd stick with twin mounts to have enough to engage multiple targets on either side of the ship.

One important point about the Akizuki class, they had not just eight guns but two directors, allowing them to engage more targets than a group of six-gun ships with the same total number of barrels. They were intended as escorts for carrier forces, where their size and range helped them to keep up, so I see a rationale for enough of them to fulfill that role (their size will also help them to accommodate added 40mm mounts).

The six-gun Fletcher equivalent seems like a Yugumo with 3.9" guns. That might be feasible; destroyers' main gunnery opponents are each other, unarmored, vulnerable to 3.9" shells, and our tactics largely emphasize night action for which maximum range may not be a major issue. And of course the majority of our fleet destroyers willl still be our existing 5" ships.

One observation, the most common arrangement in major navies including ours is one AA/DP director for 2-3 twin mounts or 4-5 single guns. Our Yamato, not surprisingly, is well equipped with four Type 94s for six twin 5"/40 mounts; as it turns out this will facilitate our planned replacement of the side 6.1" turrets with additional 5".

 

immediately lay down two more Shokaku's and as soon as we have some additional capacity another Taiho.

These are two very different ship types; I suggest we choose one or the other. The armored deck, or more accurately armored hangar, type can only accommodate two elevators, and the aft one will be covered i.e. out of action early while staging a deckload strike. The lower hangar is almost at the waterline, increasing vulnerability to underwater damage. It also appears that the air group of the Taiho may be slightly less. Overall the Shokaku has superior aviation capability, which is also a carrier's best defense.

 

If we're really interested in battleship/carrier conversions, perhaps we should consider Mutsu and Nagato. This would only involve losing half rather than 2/3 of the main armament, the remaining four guns would be 16" vice 14", and they're a few knots faster for flight operations.

In any case, there is only about 500' of length for a flight deck, less than any of our light or escort carriers. Most of them had around 590', the Taiyo class 564', Junyo and Hiyo 690'. The battleship/carrier would not be able to spot and launch as many aircraft in a single operation as the Junyo (690', 25 knots) or a light carrier like Zuiho (590', 29 knots).

The flight deck would have to be high enough to clear the forward turrets; this might favor a dual-hangar design. Would there be a small island, or would the bridge be under the forward end of the flight deck as in most conversions? The later would make the flight deck a bit higher so the bridge personnel could see over the turrets. The height might make an armored flight deck unfeasible.

The conversion proposal would remove battleships from the battle line in order to produce carriers of very marginal value. Although we can imagine missions the hybrids might perform, in combination with other ships, which of those missions could not be performed by some combination of light/escort carriers, seaplane carriers, conventional surface combatants, land-based aircraft, or other assets?

p.s. Hornet on the Doolittle raid was escorted by Enterprise, so a ship with 24-30 aircraft would not necessarily have the advantage.

 

Bobimoto-san, looking back at this I think I may have misunderstood your ideas about the BB/CV conversions; if so I apologize for the confusion. When you mentioned removing the midships turrets, especially in the Fusos whose #3 is immediately behind the bridge, forward of the funnel, I thought that meant also removing the forward superstructure and fitting a flight deck and hangars all the way to the forward turrets, for conventional takeoffs and landings. Guess I was remembering proposals for hybrid carriers with turrets forward in the interwar years.

Or were you thinking of the same concept as Ise/Hyuga, just with the catapults further forward and more deck/hangar space? If so my previous post on the topic is mostly off base. Now that I think of it, your comment about increased C&C capabilities suggests that the bridge structure would be retained.

Hopefully I haven't confused things too much further. Again, apologies to all.

 

I agree. We go with the twin 40mm mount. I am not convinced we can engineer a reliable and effective quad mount. We need to pursue it, but not commit a ton of resources to it. As soon as we have mounts stockpiled I'd immediately start replacing 25mm mounts with the 40mm on a one for one basis, while the ship is in for repairs, yard periods or refits. Later when we have sufficient mounts we can further improve on the AA suite in subsequent refits/yard periods. All new construction will be built with optimal AA suites. I also favor slapping as many 20mm Oerlikon, single mounts on, as deck space will reasonably allow.

I was not suggesting that we not build the Akizuki's, I was suggesting a smaller, less costly ship to augment them. The Akizuki's are formidable AA escort ships. Japan historically planned for 27, but only completed 12. The early ships took about two years to build. The Fuyuzuki subclass got that build time down to approximately one year by simplifying the design. The Michizuki subclass, of which only the Hanazuki was built, got the time down to eight months. We have 4 laid down at this time and have another scheduled to start in December. We need to immediately look at simplification and maximizing production efficiencies. Hopefully, we can get the planning done to incorporate some of these changes into the December ship. I think we need at least twelve, two per active Fleet Carrier. My suggestion was for an additional, smaller, cheaper in time and resources, class that we can build in greater numbers.

I appreciate your suggestion and I'll look into using a version of the Yugumo's to fill our need. IMHO, we need a fairly cheap ship, we can build quickly and in numbers. This ship needs to be a Jack-of-All trades, with a decent anti-ship, AA and ASW capability that we can use in many roles. Maybe not the best at anyone, but good enough. I think we need to look at an even smaller ship, (comparable to a US DE) for convoy, escort and ASW work. However, my plate is already pretty full and that ship will have to wait unless someone else would like to step forward with a proposal. Hope...hope...

Good info and something I think we should keep in mind (I know I will) when discussing the outfitting of our ships.

There are two reasons behind my suggestion, one rational and one personal. I have a tendency to look at things symmetrically and therefore if we have one we need another to balance it out. Probably a personality flaw on my part. The rational reason is that we need to operate, or I prefer to operate carriers in pairs. We do not know which type Shokaku or Taiho will prove to be the better warship. IRL, the Essex's I think were more successful than the armored British CV types (personal opinion). It can however, be argued that for much of the type of fighting that the Brit ships engaged in, an armored flight deck was an advantage. We really don't know what type of war we will end up fighting. By producing both types we would be hedging our bets. In open ocean, carrier vs carrier fights I see the Shokaku's as probably being the better choice. In more confined areas like the SW Pacific, where we might be in danger of encountering land based air, perhaps the more heavily armored Taiho's would be a better choice. I do not favor repeating the Soryu or Hiryu. They are really too fragile and susceptable to damage, in my opinion.

 

Not at all. Your knowledge and insightful comments are extremely valuable and greatly appreciated. I always look forward to, and enjoy your posts. I will address your comments on the BB/CV proposal, but I've got to go right now, but will get to it later this evening.

Bobimoto out.

 

Hello to all,

I just wanted to say hello to all of you, my good colleagues. Sorry for being so remiss in my duties but I know you will all do a great and fine job on the plans and logistics. I will try and catch up on the information soon. Everyone be well.

 

I think we need to look at an even smaller ship, (comparable to a US DE) for convoy, escort and ASW work.

We have a spectrum of escort ships - Shimushu/Etorofu, Mikura/Ukuru, C/D - which I would think covers our ASW needs. I believe the council had agreed on a mix of mainly C/Ds with a proportion of Etorofus or Mikuras to serve as convoy/escort group flagships (historically that was a common arrangement; such groups sank several US submarines).

The one new type we might need is the AA escort. It would be nice if we could do an AA version of say the Etorofu, but that size ship may not be able to accommodate the necessary armament, at least two twin 3.9/65s, Type 94 director, automatic weapons, and some depth charges, though not as many as a dedicated ASW ship. A new design could use the enclosed Akizuki type 3.9" mount, and I would suggest three twin 40mm. Again I think we had general agreement on this, although we might not start building them in numbers until the war situation requires it.

 

Due to the numerous bases available along the shipping routes we can get by with smaller patrol/corvette type of ASW ships. they will need some guns, but their primary function will be ASW. the main need for the larger escourts will be the south routes

 

Hybrid BB-CV

The more consideration I give this concept, the more conflicted I become over matter. Looking back to Col. Bobimoto's original proposal it would seem that the primary mission for these modified ships is for them to operate in rear, low threat area of operations, with only brief periods in near contact with strong enemy force's. Tasks such as ASW, aircraft ferry, pilot training and patrol of gaps in our base coverage. This would seem to be in conflict with the need for a ship capable of sustaining heavy battle damage such as these BB-CV's. Further a heavily armord ship is still vunerable to one or two 'lucky' hits as was the Hood, The Bismark and the Italian battleline were to bi-plane torpedo planes.

I conceed that they could be of use as a stopgap option until our new CV's can deploy, but at what cost? To achieve its target goal of 22 aircraft (in the limited hybrid version) it must employ deck parking for the majority aircraft compliment. A more extensive conversion would either need to ship fewer aircraft than the 40+ we hope for smooth turn arounds or the same degree of heavy deck parking to keep the higher projected aircraft compliment.

Is it worth it for us to have a 35,000 ton CVE (22-25 aircraft) that can operate aircraft with the same (or near) levelof speed as our first line cv's or even a CVL (40-45 aircraft) that could operate their planes with a fair degree of difficulty which would seem a liability in fast moving carrier duel?

Nor can I entirely dismiss the thought that we may need these ships at some point for the role they were intended, putting steel on target. Once converted its doubtfull that we could easily re-convert should we need to.

Finally, looking at their primary tasks it would seem that most of these could be acomplished with hulls (conversion's of liner's/Auxillery Cruiser's) that are far less costly to operate in fuel and personel.

While I am impressed by Col. Bobimoto's original thinking, the more I consider this project, the less enthused I become.

Prime Minister

 

They would still be better suited for use in the indian ocean or as first attack surface.

 

Do you mean as converted or in original configuration.

 

in original. there is less of an air threat in the Indian.

 

Good point. Although we're trying to be air-minded, we should not overlook the need for a few battleships. The British have two capital ships at Singapore and can easily deploy more in the Indian Ocean. We may also have a battle with the American fleet, which hopefully will give us an opportunity to sink them somewhere in mid-Pacific. Our battle line is just six ships. This can be augmented by the four Kongos, but they will also be in demand for operations with the carrier force or in support of cruiser-destroyer battle groups. It might be a bit wasteful to use them for shore bombardment; that could be a good role for the Fuso/Ises.

It appears that we will have only two new battleships. Under the circumstances that is probably the best we can do, but it argues against removing units from our existing battle line. Did we ever reach a formal consensus on completing Shinano as a carrier? Or evaluate the feasibility of a dual-hangar configuration comparable to our other fleet carriers?

 

My support for Shinano as a carrier is contingent on a duel hanger configuration. As yet we do not know if she can be built as such or not as we have had more pressing matters before us.

 

how far along is the shinano and would it be possible to just keep her as a BB.

 

Japanese aircraft carrier Shinano - Wikipedia, the free encyclopedia states:

Avalanche Press states:

So rougly 2.5 years from keel laying to launch. Mid 41 is a 1.5 years into construction for Shinano. This suggest if she is to be completed as a battleship and the labor can be found to do so with a decision made in October of 41 then a launch around October of 42 is possible with a commissioning date some time in early 44.

 

I do remember the informal discussion, but did not think we came to a definative decision. As for your suggestion. I would not go with the Type-C and D at this time, they were a desperation measure when Japan found themselves behind the eight-ball in relation to the US submarine campaign. They are less capable ships than the Shimushu/Etorofu and Mikura/Ukuru classes. I'd suggest we build the Ukuru's and standardize on them.
Information for those following the discussion:
--The four Shimushu's are already in service, I favor building no more of them, but when able upgrading them to the new standard.
--The Etorofu's are scheduled to begin being laid down, starting in March '42.
--The Mikura's were improved Etorofu's dedicated to AA and ASW work. Historically the first was laid down in October '42. Slightly heavier ships, (955tons vs 874 and 884 on the same dimensions and .3 knots slower at 19.5 knots).
--The Ukuru's were modified Mikura's, simplified and using prefabrication to get the build time down to as little as four months. Basically the same weapons fit. They were noted as being very durable ships.
--The Type-C and D, were downsized Mikura's with 3 fewer knots speed and less weapons. They also used prefabrication and dropped buildtime down to as little as 3-4 months. The man hours required were: Mikura's 57,000 hours--Ukuru's 35,000--Type C/D 20,000. I think because we are wanting to address the potential submarine threat early, are going to have more ASW air assets and start building small escorts sooner, we might not get behind the bell curve. I'd prefer to build a simplified ship using mass production and a good ASW/AA weapons fit. Basically an Ukuru. Let's build as many as we can and standardize on that type. If it looks like we're not keeping up we can always lay down the C/D type ships, but the one month or so build time difference should not be a big factor since we're starting early. I would build them to the historical ASW fit with an upgrade to a 5.9" ASW mortar replacing the 3.1" when we have enough available. The historical ships had 16-20 25mm guns. If we take the weight of these weapons and substitute a similar weight of 40mm twins and 20mm Oerlikon singles we'd have 3 x 40mm twin bofors mounts and 10 single 20mm oerlikons. Not a bad AA suite. Historically, they had 3 x 4.7"/45. Would you suggest we keep them or build with the 5" Type 89. It is an excellent DP gun, with good AA capability, but it's low muzzle velocity limits it's range somewhat. The change to the 5" would cause an additional 1.5 tons of weight.

I like it. We have the Akizuki's for our most valuable ships, but build time, size and cost will limit us on them. What would you recommend? Please elaborate.

 

Our current projection is that:

In mid-1941, construction on Shinano's hull was temporarily suspended so as to allow personnel and equipment to be utilized for other naval projects in response to approaching hostilities..........her hull was only 45 percent complete by that time, with structural work complete up to the lower deck and only major machinery parts installed.

In one of our previous discussions, Takao I think? informed us that her nine 46cm guns had/have been built.

Pending better information, my guess is that it would take roughly the same investment of resources to complete her as carrier or battleship. The time to make her operational is probably about the same also.

As I see it, we are basing our strategy largely on what might be called 'asymmetrical warfare'. Our predecessors realized that we cannot hope to match the Americans, British, et. al. ship-for-ship in every category, so we have stressed tactics like night or long-range torpedo attack and land- or carrier-based aircraft. So, while there is some merit in completing another powerful battleship, I think pumping up our investment in aircraft carriers might be the better option.

Getting back to Bobimoto-san's proposal, it would take a substantial investment in 'un-construction' to get ships like Ise or Fuso to where Shinano is now; so if we are going to turn any battleship into an aviation ship, we should probably start with Shinano.