Uboat Exhaust Smoke

[grimes]

i finally got the exhaust/water combimod to work. i had a question though, did uboats really create exhaust smoke such as that. i imagine they would at full ahead.

[Damo]

Diesel engines = Dirty ****ers.

[Cheapskate]

Originally Posted by grimes

i finally got the exhaust/water combimod to work. i had a question though, did uboats really create exhaust smoke such as that. i imagine they would at full ahead.

The exhaust smoke mod works on a speed related basis i.e. more speed = more smoke.

From what I've read (and remember from RB's original thread), it isn't quite as simple as that.

A properly maintained diesel engine will emit some black smoke on startup and whilst accelerating. It is caused by the engine not burning all the diesel fuel being injected until it reached the desired operating rpm.

So in going from ahead slow to ahead one third say, the exhaust should show some smoke gradually reducing to nothing. This would happen each time the engine telegraph settings were increased. So even at flank, the engine would not always be smoking.

Racerboy's implementation was therefore rather unrealistic ..unless there was some malfunction, but it is nice eye-candy and many Kaleuns wouldn't be without it!

[Laufen zum Ziel]

I would not be without it.

[Patkins1983]

Diesel is a mixture of hydrocarbons so there is some variation in the mixture.
I would imagine as the war went on, the diesel quality probably went down and you would get more smoke from poor quality fuel.

Just how well where the engines on a U-boat maintained, anyone know of any figures or a site with this info?

[U2222]

Well keeping on top of the injector maintenace was a pretty high priority.
Making smoke means only one thing sooner or later - detection.

[Patkins1983]

I would imagine the whole engine would be a high priority, oil burning wouldn't help the smoke situation.

I have seen trains with old engines put some fairly lengthy blue smoke trails behind them, now that would be a disaster with a u-boat. Might as well have flashing neon sign saying "bomb me"

[sunvalleyslim]

Originally Posted by Cheapskate

The exhaust smoke mod works on a speed related basis i.e. more speed = more smoke.

From what I've read (and remember from RB's original thread), it isn't quite as simple as that.

A properly maintained diesel engine will emit some black smoke on startup and whilst accelerating. It is caused by the engine not burning all the diesel fuel being injected until it reached the desired operating rpm.

So in going from ahead slow to ahead one third say, the exhaust should show some smoke gradually reducing to nothing. This would happen each time the engine telegraph settings were increased. So even at flank, the engine would not always be smoking.

Racerboy's implementation was therefore rather unrealistic ..unless there was some malfunction, but it is nice eye-candy and many Kaleuns wouldn't be without it!

Cheapskate is right. Having been on a Fleet Boat, start up and low RPMs causes smoke. At Standard speed or above I never saw smoke from the exhaust while under way. Unless it was a change in RPMs

[Zilch]

Historically being more of an aviation guy, I'm not as familiar with the workings of diesel subs just yet...where were the exhaust vents? Would this have worked in a similar fashion to the outboards on the family fishing boat, where the exhaust gases pump out into the boat's wake?

[Ford Prefect]

It could be worse, they could start doing like a badly maintained russian diesel loco and spit huge flames out their exhausts into the air. That would be akin to having a beacon saying "yoo hoo, i'm here!" every time you throttled up.

Surprise.
The exhaust went into the main balast tank, filling it, and providing posative boyancy.
The germans didn't use compressed air for this. Smart idé. No smoke. Everything eventualy goes out the bottom. Makes for a good muffler too.

[Cheapskate]

Originally Posted by Snestorm

Surprise.
The exhaust went into the main balast tank, filling it, and providing posative boyancy.
The germans didn't use compressed air for this. Smart idé. No smoke. Everything eventualy goes out the bottom. Makes for a good muffler too.

You are referring to the KM method of blowing the residue out of the Main Ballast Tank after surfacing. This was a specialised function designed to avoid unnecessarily depleting the high pressure air banks. The RN and USN used a separate low pressure air blowing system to do this.

Ordinarily the engine exhausts did vent into the atmosphere. They can be seen ( above and in between the two rows of rectangular hull vents ) in the following photographs:-

http://www.uboat.net/gallery/index.h...95D&img=15
http://www.uboat.net/gallery/index.h...505A&img=8
http://www.uboat.net/gallery/index.h...534A&img=6

All in all I don't think the KM were unduly concerned about noise suppression on U-Boats. They weren't particularly noisy (even when running on diesels) and the amount of smoke generated during acceleration was minimal on a properly maintained engine.

However they did have a different attitude to the S-Boote where the later models did feature underwater exhausts. Mind you they did have three engines apiece and operated in packs.

Thank you, Cheapskate.
I found your expansion on my post to be both interesting and educational.
I salute you, sir.

[Cheapskate]

Glad to be of help Snestorm

"Interesting and educational" - Kind words indeed ... never before applied to yours truly.

Cheers for that

Happy hunting