Furious and Akagi routed exhaust through long internal or horizontal trunks rather than a compact island funnel. Those ducts occupied hangar volume, added weight and complexity, and could heat the aircraft working space. Open lower flying-off positions helped move cool air through the ship but did not remove the fundamental penalty. The comparison gives a concrete reason why later carriers preferred to carry exhaust upward and away through an island.
Chapter · 2:17:44-2:21:19
Furious and Akagi show how exhaust trunking consumed hangars
The comparison links aircraft capacity, hot hangars, weight, and complex airflow directly to the absence of a conventional island.