WW1 IJN Fast Battlecruiser studies

Not much I know about the history of these 4 battlecruiser studies, but they were proposed in 1916 as very fast and large capital vessels with good armour and armament. Their armour and armament was almost the same as the Nagato class battleships but speed was chosen for 34,5 or 35knots. My idea that these ships were actually the battlecruiser versions of the Nagato class battleships. Later these studies were used for the B-62 design battlecruisers (A through F) which were (among many) are the preliminary designs of the Amagi class battlecruisers (design B-64).

The unique things about these studies are the large size together with strong engines and 6 shafts to achieve the desired speed.
All images are from the Hiraga archive of University Toyko.

Sidenote: The 14" 3rd year type cannons listed in the documents are actually the 41cm Type 3 (3rd year type) cannons used on Nagato, Amagi, Tosa and Kii classes. The designation is for secrecy, the only large calibre Type 3 cannons the IJN had at that time was the 41cm.

Data pages:







Original drawings:
Design I:

Design II:

Design III:

Design IIII:



Arrangement of 6 shafts of Design I and III:

Arrangement of 6 shafts of Design II and IIII:



My take for a modernised Design III:

Just as a matter of curiosity, but why is it in English? Did the Japanese constructors use English? Or are these some sort of British or American intelligence files?

Regards.

The Japanese were allied to the UK up until the early 1920s and kept buying designs from British armament firms even when they started home build and design.

In converting the armour measure from plate weight to inchs I found an interesting tidbit.

www.kbismark.org/forum/viewtopic.php?t=1643

Which is that 40 lbs of plate equals one inch of thickness. But a British armour inch is 25.9mm not 25.4mm. So a 600 lbs plate of British armour is written as 15" but is actually 373.5m or 14.7". Thank the Goddess of Reason for the Metric System!

PS Thanks to Tz. for the images.

Yes 1inch = 40 pounds of armour. USN used this system too in WW1.

As for english: Hiraga Yuzuru studied in England for many years and had strong connection with the Vickers company.

Thanks for those bits of info.

Another question which your answers has caused. I've never quite understood when armour is described by weight. I understand that it is for a given thickness of armour, but is it for how much say a square foot of armour weights?

Thanks for your answers in advance.

Regards.

It's based on a plate 1 foot (12 inches) square and 1-inch thick.
For the Metricated that's 30.5cm

Thanks for that, another metaphorical itch scratched.

Regards.