Japanese stacks

[chuck]

Some of the Japanese warships funnels features prominent bulge near the top that supposedly trap sparks and reduce the ship's visibility at night.

1. Why would oil burning boilers produce sparks?
2. Why do other people's funnel not have this feature?

[Werner]

I thought the shrouded caps were to prevent rainwater from entering the boilers.

[chuck]

Why do some ships have it while others not? The ships that had it mostly seemed to have acquired it as a retro-fit. No ship seemed to have been built with it.

[Werner]

I will look through LaCroix and report back.

[bengtsson]

Do you mean like on the Kongo class BBs. The stack is wider at the top? This shows up clearly in some photos in Fukui's BB book. Haruna as well. I'm not finding that on the Cruisers.

Bob B.

[chuck]

Do you mean like on the Kongo class BBs. The stack is wider at the top? This shows up clearly in some photos in Fukui's BB book. Haruna as well. I'm not finding that on the Cruisers.

Bob B.

Yes. The old light cruisers with 3 or 4 stacks often had them.

[peppe]

lacroix pag 186 "while the Kuma was in reserve [1929] she underwent special repairs, during which her three funnels were fitted with special antirain caps. Such caps were also tested temporarily on the Kongo and Kako and on the destroyer Shiokaze."
the antirain caps are cited also in the foto page 188 drawing pace 190 and foto page 199
ciao peppe

[Werner]

I was about to post p. 186 reference, but peppe beat me to it!

[bengtsson]

So how were they supposed to work? Were they kept on the Kongo and sister ships?

Bob B.

[chuck]

How come no one else found the rain bothersome enough to fit something similar?

[chuck]

Is anti-rain cap the same thing as the bulge on the upper section of the funnel, or is it some sort of lid fitted to the top of the funnel?

[Neptune]

Hmm, maybe it has to do with exhaust temperature and length of funnel. The longer the funnel, and the hotter the exhaust, the more time the rain would have to vaporise and return upwards with the exhaust flow. If you have a low exhaust temperature you might actually have rain (liquid) coming inside and cooling down some parts that shouldn't be cooled down or block certain parts of the engines. Of course the lower the exhaust temperature the better the engine...

[Werner]

I think it's a cover which diverts the smoke 180 degrees and then outboard, where it meets a stream of rising air generated at the lower surface of the "bulge", which makes sure the smoke clears what would otherwise be an obstruction.

[bengtsson]

It's a mystery to me! Only experience I've ever had with water down a funnel was out in the Bering Sea once in a Destroyer Escort. In very heavy seas, we took water down the funnel and killed the boiler fires. We had an exciting 10 minutes till they were fired up again! No idea how that all worked, as I never had a thing to do with boiler of engine rooms.
Rain couldn't really be a problem could it? We needed a a storm with 100 mile an hour wind gusts and waves god knows how high to kill the fires on a very small ship.

Bob B.

[chuck]

It's a mystery to me! Only experience I've ever had with water down a funnel was out in the Bering Sea once in a Destroyer Escort. In very heavy seas, we took water down the funnel and killed the boiler fires. We had an exciting 10 minutes till they were fired up again! No idea how that all worked, as I never had a thing to do with boiler of engine rooms.
Rain couldn't really be a problem could it? We needed a a storm with 100 mile an hour wind gusts and waves god knows how high to kill the fires on a very small ship.

Bob B.

Was the water that doused the boilers from wave washing over the funnel or from the rain?

I find it hard to believe a couple of inch of mere rain an hour can make its way down the exhaust against the superheated gases coming up, much less reach the burner tips in enough quantity to douse the boiler fire.

[bengtsson]

Massive wave crashing onboard and throwing water down the stack. A freak wave. I've never heard of rain being enough to flood out the boilers. First I knew of it I was thrown across the compartment and was nearly knocked out. No steam, you soon go broadside to the seas and roll nearly over. The wave was a freak because we were steaming into the seas and doing fine. Just happened to be twice the size of the others from what the bridge watch said. Winter of 1970-71.

Bob B.