Hi everyone. I’m new to Japanese warship so hope you don’t mind I ask a stupid question.
I find that many Japanese aircraft carriers in WWII have their funnel pointing downwards. This is very weird. Probably they are the only ships in the world having this feature. Question is why the Japanese design their carrier like this? Is there a specific reason? To make thing weirder, I’ve seen a picture of a Japanese carrier (I think is Kaga) that there was water coming out from the funnel! How can that happen? In fact the box art of Hasegawa Akagi also show this. Can anyone shine some light. Thanks.
I don’t really know, but I’ll offer my best guess!
Perhaps the funnels point down and away from the carrier deck to reduce soot and smoke interference. I’ve seen the cover art you refer to, and it certainly looks like water coming out of what must be the funnel. Maybe the Akagi incorporated a design to flush water through the funnel stack to filter out the soot from the engines, lowering the possibility of early detectment?
The IJN were very ingenious with many of the designs they used for ships and carriers, and were early proponents of larger and more complex carriers.
The hot exhaust gases from the stack disturbed the handling of the light, fragile aircrafts of 1920s and 1930s during their landing runs. The Japanese simply wanted a means of keeping those hot gases away from the flight deck. The flip side of their down turned stack is the hot exhaust gases coming out of the funnel made the ant-aircraft gun positions on the side of the hull almost uninhabitable. This is why Akagi and Kaga has unique, sealled air-tight 5 inch AA gun mounts abft the down turned stack.
Also, the down turned stack means if the ship were to list seriously, as in a storm, water could enter the stack and put out the boiler fire.
USS Ranger (CV-4) had a similar arrangement of horizontal funnels. The aborted postwar American carrier USS United States also were to have horizontal stacks.
I believe the message about the stack gases interfering is correct As to water it may be like when you run your car in cold weather you can see condensation water dripping out of the tailpipe but that is just a guess on my part
There’s a couple of things going on with a capital ship’s steam plant. The number (and efficiency) of the boilers creates a “need” for a certain length of “chimney” from the oil burners in the boilers (allowing, also for the balancing effect of the blowers supplying combustion air to the boiler spaces). To complicate the equation a bit more, the number of boilers “lit” has to be able to vary, as well.
Now, with all that draft going, it becomes a convenient place to exhaust anything unwanted over the side. So, there’s lots of gas volume of many components exiting a naval stack.
Sticking said stack on an aircraft carrier adds a whole 'nuther level of complexity. USS Langley had hinged stacks, IIRC, which the engineering department is alleged to have not liked at all. But, the deck plan was not wide enough to get the exhaust gasses out of the flight operations envelope in any other fashion. Consider the solution used by Lexington & Saratoga. The height of the stack mass was dictated by the engineering plant, and by flight operations.
Now, it’s been years since I sat in classroom being taught steam engineering plants, but the IJN carrier designs were cited for both their hits and misses (as engineering solutions). One of the less-good ideas was the turn-down on the funnel.
The top edge of that funnel would be as hot as the gasses running over it, the lower edge not so much. Driving that heated metal shape at full throuttle in humid conditions is likely to create condensate. As much as on the rendering? Dunno.