When Akagi was rebuilt in 1938, she had an island on the port side.
When Kaga was rebuilt in 1934, she had an island to starboard.
Previously they (and other early Japanese carriers) had no island at
all.

The island didn't serve as a venue for smokestacks. Instead, the
stacks were vented to the side and down.

There are later Japanese carriers with the island to port and also to
starboard.

all the best -- Dan Ford
email: (put CUB in subject line)

see the Warbird's Forum at www.warbirdforum.com
and the Piper Cub Forum at www.pipercubforum.com