I meant: Furutaka ship class upgrades to Aoba ship class. I am wondering because this classes have different maximum speed, endurance and fuel capacity. Sister ships should have the same values and there should be only one ship class, or not?
I have not looked at this - it is data from CHS. However:
There are two nearly identical classes of Japanese CAs - the first modern ships of their type in the world; each class has two ships:
Furutaka and Kako are the first sub class;
Aoba and Kinugasa are the second sub class
Originally armed with six singe guns, they were all rearmed with three twin mountings. These were the very first heavy cruisers built under terms of the London Naval Treaties, and they were, with the light cruiser Yubari, technology test platforms for a new concept in cruiser design (done because there would not be large fleets of modern battleships).
The ships actually did change speed over time, and they also changed fuel capacity and radius. Whatever data is in our database is probably correct for some variant or other! But I will look at it.