The Sendai class was based upon the Tenryu class / Nagara class of cruisers.
The Sendai class was to built under the 1920 Program and approved by the 1921 - 1922 Estimates. The Washington Treaty was signed right after the ships were ordered and several had to be cancelled to stay with its limitations.
Was originally going to be called the Nara class, but as it was damaged in an earthquake the Sendai ended up being finished first and the class named after her.
Under the navigation bridge was a hanger for the aircraft. Initially there was a flyoff platform, but no aircraft were ever operationally used from there. Later a catapult was installed between the aft guns, Nos. 6 and 7 and a Type 94 floatplane was used.
Only one Kanpon mixed firing boiler was installed. It was placed in the forward boiler room with its own uptake.