Mizuho and Nisshin as CVL?

[Historiker]

Working on the interwar Japanese Naval-Buildup, I just read that both Nisshin and Mizuho weren't converted into carriers because they were sunk before it was needed.
This implicates, that conversions were both possible and considered.
Is there any reason why this two ships shouldn't be able to convert into carriers because of historic technical reasons in a hypothetic mod?

[DuckofTindalos]

The Mizuho was never considered for conversion as her top speed was only 22 knots. The Nisshin could have been converted; the problem would have been the same as with all the other IJN carriers, i.e. finding the aircraft and pilots to put on her.

[Historiker]

Yes, that's what I thought, thank you.

As the Mizuho was an improved Chitose, her Diesels have to be replaced by Steam/Diesel or just Steam turbines. This should give her the necessary speed. But: Is that to expensive? How long does it take?

With her Diesels, she should also be able to operate as CVE, no?

[DuckofTindalos]

Takes a long time to change powerplants, and Japan had more than enough other priorities. However, if all you wanted was a CVE to do plane ferrying and ASW escort, she could be useful.

[herwin]

ORIGINAL: Historiker

Yes, that's what I thought, thank you.

As the Mizuho was an improved Chitose, her Diesels have to be replaced by Steam/Diesel or just Steam turbines. This should give her the necessary speed. But: Is that to expensive? How long does it take?

With her Diesels, she should also be able to operate as CVE, no?

She was slower than the Chitose class at 28 knots.

[Historiker]

Hmm...
Having the exact sizes of the engine might allow to consider the replaceing of the engine by (several) destroyer turbines. If we look at the other Japanese CVLs and CVs, a speed of 25-26 should be enough for most fleet operations, no?
Destroyer turbines were available throughout (most) of the war, so this should be possible, no?

If you agree, what do think how long the conversion would take without shortages of material? 6 months? 12 months?


As CVE: That would be better than nothing.


What would you do if you were in charge? Leave it as a CS or convert it to a CVE or CVL?

[Historiker]

ORIGINAL: herwin

ORIGINAL: Historiker

Yes, that's what I thought, thank you.

As the Mizuho was an improved Chitose, her Diesels have to be replaced by Steam/Diesel or just Steam turbines. This should give her the necessary speed. But: Is that to expensive? How long does it take?

With her Diesels, she should also be able to operate as CVE, no?

She was slower than the Chitose class at 28 knots.

I know, that was because she only had diesels, no mixed propulsion.

[DuckofTindalos]

I'd probably turn her into a diesel-powered CVE. Fastest conversion I could do, to give my convoys some modicum of air cover.

She'd be sunk quickly, of course, but still...

[herwin]

ORIGINAL: Historiker

Hmm...
Having the exact sizes of the engine might allow to consider the replaceing of the engine by (several) destroyer turbines. If we look at the other Japanese CVLs and CVs, a speed of 25-26 should be enough for most fleet operations, no?
Destroyer turbines were available throughout (most) of the war, so this should be possible, no?

If you agree, what do think how long the conversion would take without shortages of material? 6 months? 12 months?


As CVE: That would be better than nothing.


What would you do if you were in charge? Leave it as a CS or convert it to a CVE or CVL?

A reliable 25 knots was enough for carrier TF operations. More than that allowed the ship to get the hell out of Dodge City when necessary--there isn't much that can stay with a CVN at full speed over a distance, but 25 knots was good enough for flight operations.

[Historiker]

Well, that would be the cheapest and fastest solution, yes.

30 aircraft and 90 Missions both?


Any more ships, where a conversion was realisticly possible?

[DuckofTindalos]

Not even 30 planes. For CVE convoy escort duty, maybe 18 planes tops.

[Historiker]

ORIGINAL: herwin

ORIGINAL: Historiker

Hmm...
Having the exact sizes of the engine might allow to consider the replaceing of the engine by (several) destroyer turbines. If we look at the other Japanese CVLs and CVs, a speed of 25-26 should be enough for most fleet operations, no?
Destroyer turbines were available throughout (most) of the war, so this should be possible, no?

If you agree, what do think how long the conversion would take without shortages of material? 6 months? 12 months?


As CVE: That would be better than nothing.


What would you do if you were in charge? Leave it as a CS or convert it to a CVE or CVL?

A reliable 25 knots was enough for carrier TF operations. More than that allowed the ship to get the hell out of Dodge City when necessary--there isn't much that can stay with a CVN at full speed over a distance, but 25 knots was good enough for flight operations.

It should be cheaper to leave it with the slow speed. When I use my system of calculating the building costs, it will make a significant difference wheter to equip it with fast turbines or "just" put a flightdeck on it.


One more significant question:
Can conversions be done in a civil shipyards, i.e. be payed by merchant shipyards? I would guess: Yes! - but this isn't my business.
As CVEs are payed IIRC with merchant points, I can let them be (re)build as CVE and immediately upgrade to their correct type after construction.

[DuckofTindalos]

Besides, destroyer turbines are for destroyers. Build Akizukis with them, and don't waste them on a low-effectiveness CVE conversion.

[Historiker]

ORIGINAL: Terminus

Not even 30 planes. For CVE convoy escort duty, maybe 18 planes tops.

Why?
If I take the size of the Chitose, both ships should be able to carry 30. So what reduces it's capability so drastically?

With only 18, equiping the ship with new turbines gets attractive again...

[DuckofTindalos]

The Chitose could operate 30 aircraft on an 11,000 ton hull. The Taiyo, Japan's first CVE, could theoretically operate 23 on nearly 18,000 tons.

Size isn't the issue, however, but keeping as many aircraft as possible for the first-line fleet carriers is.

Call it 20: Six A6M (with 2 in reserve) and 10 B5N (with 2 in reserve).

[Historiker]

ORIGINAL: Terminus

Besides, destroyer turbines are for destroyers. Build Akizukis with them, and don't waste them on a low-effectiveness CVE conversion.

I thought about Katsuragi and Aso... 12 more planes should be an argument to build one or two Akizukis later, no?

If I'm right, the Chitose had 56,800 SHP, the Akizuki 50,000. But did the Chitose use both enginges to achieve its 29kn or just the turbine?
The Mizuho reached 22kn with only 15.200SHP, what would it reach with 50.000?
The Chitose had 28,9kt, so with 83%, the ship will rund how fast? 83% of 28,9kt are 24kt, but is that correct? In Battleships, Design and Developement are the correct formulas to calculate it but I don't have it in my hands before monday as it lies in the library of my university.

[DuckofTindalos]

Again, depends on what you want to convert her into. A fleet CVL needs all the horsepower she can get, obviously. A convoy escort CVE needs enough to conduct flight operations and that's it.

[Historiker]

ORIGINAL: Terminus

The Chitose could operate 30 aircraft on an 11,000 ton hull. The Taiyo, Japan's first CVE, could theoretically operate 23 on nearly 18,000 tons.

Size isn't the issue, however, but keeping as many aircraft as possible for the first-line fleet carriers is.

Call it 20: Six A6M (with 2 in reserve) and 10 B5N (with 2 in reserve).

Sorry, I don't understand that. I understand that both the sheer dimensions and displacement don't explain accurate how many planes a ship can carry. Is it armoured, hwo big is the hangar, etc. But why does the Chitose carry 30 while a Mizuho of the same size isn't able to do it? The slower speed might reduce the weight of the planes to launch but why less?

If the speed is important, the Akizuki turbine is an option - but only then, of course.

[DuckofTindalos]

It's your call, of course. If you want it to be 30, then it's 30.

[Historiker]

ORIGINAL: Terminus

It's your call, of course. If you want it to be 30, then it's 30.

I know

But I'm always interested to learn! I don't believe you say "18 or 20" just for the joy of disagree. [;)] So you'll have your reasons. Can you give me them (perhaps in German if I don't understand)? If I still disagree after understanding your arguments, I still can leave it at 30.

But I really want to learn.