Due the late-war chronic shortage of raw materials, the Unryuu-class machinery was designed to use heavy cruiser turbines, but even with that compromising, the Japanese had no choice but use destroyer turbines on Katsuragi to complete her.

LucasHidemiKomori said:

Due the late-war chronic shortage of raw materials, the Unryuu-class machinery was designed to use heavy cruiser turbines, but even with that compromising, the Japanese had no choice but use destroyer turbines on Katsuragi to complete her.

Oh that explains their difference in, err... displacement.

I dunno man, 2 knots seem to be a highly marginal difference in speed in regards to power difference...

2weeabo4u said:

I dunno man, 2 knots seem to be a highly marginal difference in speed in regards to power difference...

Power in ships is extremely non-linear, particularly as you approach or exceed 30 knots the cost for every extra knot skyrockets. It's only rarely worth the effort and the Japanese obsession with high powered machinery particularly on cruisers and carriers really did them no favors in my view. It bought perhaps a knot and a half to two knots of useless speed at the cost of increases in weight, plant size, and complexity that likely contributed to laughable cutbacks in protection.

Though the real issue with the use of destroyer machinery was that it was optimized for maximum power in a given space, but not anything like maximum reliability or efficiency. Destroyer plants on all sides were rather fickle and only rarely actually operating at full capacity, they were the race engines of the ship world. By contrast the larger 'decompressed' plants on cruisers and capital vessels tended to be 'less efficient' power to weight wise, but considerably more maintainable and fuel efficient.

2weeabo4u said:

I dunno man, 2 knots seem to be a highly marginal difference in speed in regards to power difference...

As was discussed in a previous post, even large increases in power generally result in little actual increase in speed or utility. The "oh so fast" Shimakaze was only ONE knot faster than most of the other Fubuki-class. In fact, which ships were in the top five rankings of horsepower would probably be hard for you to guess. It's mostly that, as speed increases, so does friction and fuel consumption (which means carrying more fuel, which means a larger ship, which means more mass, which means needing more engine to counteract that mass...) such that you have a quadratic increase in needed power/engines relative to speed.

That said, this "Katsuragi is so flat" thing is kinda exaggerated based upon simply not being as decked-out as her older sisters. It's quite open to debate by some artists. People seem to just want to sort all the carriers into one of two opposite extremes when it's a much less clear-cut thing looking at just the official art...

NWSiaCB said:
That said, this "Katsuragi is so flat" thing is kinda exaggerated based upon simply not being as decked-out as her older sisters. It's quite open to debate by some artists. People seem to just want to sort all the carriers into one of two opposite extremes when it's a much less clear-cut thing looking at just the official art...

Actually, her official art isn't ambiguous as to the size of her assets. The example you provided is simply the common practice of drawing a character to have bigger breasts than they actually have. In fact, the majority of the 39 fanarts currently uploaded here as of this post portray Katsuragi as being very modest.

LoweGear said:

Actually, her official art isn't ambiguous as to the size of her assets. The example you provided is simply the common practice of drawing a character to have bigger breasts than they actually have. In fact, the majority of the 39 fanarts currently uploaded here as of this post portray Katsuragi as being very modest.

That's actually part of my point... All the other carriers are just immediately tagged as "giant breasts" if they have any at all, and "flat chest" if it's more modest than some of her most direct competition. Akagi in her original official art has a chest that's not nearly as ample as most fan artists (or the anime) like to portray. The difference between Shoukaku and Zuikaku isn't nearly so pronounced as artists keep trying to make it.

It's more than a little annoying to see Zuikaku turned into a "cries blood over seeing women with breasts due to breast envy" Flanderized character.

Katsuragi is clearly smaller than her sisters, but in her official damage poses, she has something of a curve...

LucasHidemiKomori said:

Due the late-war chronic shortage of raw materials, the Unryuu-class machinery was designed to use heavy cruiser turbines, but even with that compromising, the Japanese had no choice but use destroyer turbines on Katsuragi to complete her.

The heavy cruiser machinery was not really a war compromise, the original Soryu and Hiryu also used similar heavy cruiser machinery, essentially the same as Mogami/Tone/Ibuki class.

Hyper_Shinchan said:

The heavy cruiser machinery was not really a war compromise, the original Soryu and Hiryu also used similar heavy cruiser machinery, essentially the same as Mogami/Tone/Ibuki class.

At that point, the Japanese had the Shoukaku and Taihou classes, but since they lost four fleet carriers at Midway, they decided to use a modified older design (Hiryuu) to replace these losses faster.

EGADS!

NWSiaCB said:

As was discussed in a previous post, even large increases in power generally result in little actual increase in speed or utility. The "oh so fast" Shimakaze was only ONE knot faster than most of the other Fubuki-class. In fact, which ships were in the top five rankings of horsepower would probably be hard for you to guess. It's mostly that, as speed increases, so does friction and fuel consumption (which means carrying more fuel, which means a larger ship, which means more mass, which means needing more engine to counteract that mass...) such that you have a quadratic increase in needed power/engines relative to speed.

Fubkui never made 38 knots, ever, just like Mogami never made 37 knots, ever.

38 knots was the "design speed" AKA the goal they hoped to attain. I haven't seen trial data from before them, but after various rebuilds added weight the Fubuki's trial speed dropped to 34 knots. The very similarly sized and powered Asashio was credited at 35.

Shimakaze however conducted trials under a heavier load condition then earlier Japanese vessels and the nearly 41 knots attained was also an actual measured speed not a 'design' goal. Although like many trial figures she was running the engines at a minor overload condition, but even so she was probably legitimately good for 39 knots at a reasonable combat load. Meanwhile whatever it said on the tin other US and Japanese DDs in the 2,000 ton class could not get much over 35 even under fairly ideal conditions. However this still meant she was, at best, about 4 to 5 knots faster then ships that were much lighter and much cheaper designs and possessed zero offensive or logistical advantage over them.

NWSiaCB said:

That's actually part of my point... All the other carriers are just immediately tagged as "giant breasts" if they have any at all, and "flat chest" if it's more modest than some of her most direct competition. Akagi in her original official art has a chest that's not nearly as ample as most fan artists (or the anime) like to portray. The difference between Shoukaku and Zuikaku isn't nearly so pronounced as artists keep trying to make it.

It's more than a little annoying to see Zuikaku turned into a "cries blood over seeing women with breasts due to breast envy" Flanderized character.

Katsuragi is clearly smaller than her sisters, but in her official damage poses, she has something of a curve...

Amen brother, it really is annoying so many artists seem to only be able to comprehend "gag boobs" and "washboard".

LucasHidemiKomori said:

At that point, the Japanese had the Shoukaku and Taihou classes, but since they lost four fleet carriers at Midway, they decided to use a modified older design (Hiryuu) to replace these losses faster.

Shoukaku and Taihou used plants only slightly modified over the dragons meaning they all essentially had cruiser plants.

Honestly the Japanese cruiser plants were much too large and the power output overkill that gave no real tactical advantage. (Indeed much of the reason US cruisers were able to match or even exceed the cheating bastards in weaponry and protection while remaining close in speed was because their plants were as much as 100 feet shorter and much more efficient). However it must be said that in a CV application they were ironically just about right with 150-160,000 HP being about what's needed to drive a 20-25,000 ton vessel to 30+ knots.

Given that the Japanese cruisers were already stupidly overpowered this then was really no weakness at all. Nor was it that uncommon in any case. Essex utilized a pair of compact plants derived from the Atlanta class AA cruiser for power for instance. Cruiser plants in general were a good fit for CVs as they tended to be high power, reasonably compact, but designed for long cruising operations. Engineering plants are complex and if roughly the same design can be utilized across multiple classes considerable design work and retooling can be saved making it a sensible decision in peace or wartime.