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ImperiumDylan

Why do some battleships have 1 or 2 smoke stacks and what is the benefit of 2 over 1

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It all depends on the placement of the boiler rooms and the way the funnel updraught from them is arranged. If the boiler rooms are close enough together, you can trunk all the funnels into one.  This has some benefits in regard to NOT being able to determine a ship's heading on the basis of its funnels' separations. However, the aerodynamics and thermodynamics of the duct systems, not to mention the volume they occupy, can sometimes make trunking very awkward if the boiler rooms are too far apart.

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3 minutes ago, Ensign_Cthulhu said:

It all depends on the placement of the boiler rooms and the way the funnel updraught from them is arranged. If the boiler rooms are close enough together, you can trunk all the funnels into one.  This has some benefits in regard to NOT being able to determine a ship's heading on the basis of its funnels' separations. However, the aerodynamics and thermodynamics of the duct systems, not to mention the volume they occupy, can sometimes make trunking very awkward if the boiler rooms are too far apart.

Think it also depends on the numbers of boilers and boiler rooms in addition to what is mentioned above.

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3 minutes ago, Ensign_Cthulhu said:

It all depends on the placement of the boiler rooms and the way the funnel updraught from them is arranged. If the boiler rooms are close enough together, you can trunk all the funnels into one.  This has some benefits in regard to NOT being able to determine a ship's heading on the basis of its funnels' separations. However, the aerodynamics and thermodynamics of the duct systems, not to mention the volume they occupy, can sometimes make trunking very awkward if the boiler rooms are too far apart.

^ Got it in one.

Some Japanese ships have very obvious duct trunking going on like here on Yuubari for example:

E6RiUZG.jpg

 

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Fewer stacks takes up less deck space and gives you better arcs of fire for your guns. You can see it with the Baltimore class. The later Baltimores (the Oregon city subclass if you look them up) were modified to have one stack to clear deck space for improved fields of AA fire. Des Moines copies that in the game. One stack requires you to run a lot of extra ducting from the boilers to the single stack though to exhaust the smoke. That tends to eat up space below decks which could go to armor and other things. It's really just a design choice. North Carolina class for example had two stacks because she could afford the deck space. TO stay within the tonnage range and improve armor, the follow-on South Dakota design (Alabama and Massachusetts in game) had to be shorter than NC. That meant less deck space so South Dakota and her sisters only had 1 stack. It's really just a matter of linear space that you can afford on the deck (two stacks) or space to spare for extra ducting below deck in the form of more volume (for one stack). 

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Something else I forgot to mention is that the ducting or trunking of a funnel either forward or aft can help remove its efflux from sensitive things like rangefinders, gun directors or secondary armament emplacements.

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24 minutes ago, Lert said:

^ Got it in one.

Some Japanese ships have very obvious duct trunking going on like here on Yuubari for example:

E6RiUZG.jpg

 

Yep. Quite a few Japanese ships did this. This is an above-deck trunking. It is still eating up the deck space of two stacks, but the first stack is curved and fused with the second to clear the bridge like @Ensign_Cthulhu mentioned above. This isn't much of a space saving on the deck. It is more to keep funnel exhaust away from the bridge and the rangefinders. Oregon City and Des Moines did a more extensive trunking below the deck. Here's Baltimore:

Spoiler

See the source image

Here's Oregon City:

Spoiler

us_cr_18.gif

It's basically the same ship, but the Oregon Citys have the exhaust from two funnels in the earlier Baltimores trunked under the decks to one funnel so the superstructure could be consolidated for better AA fire. The later Cleveland class ships (Fargo subclass) did the same thing. They then followed it again with Des Moines.

Edited by Tzarevitch
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Generally, making separate straight funnels is cheaper and quicker to manufacture, and is much easier in terms of maintenance and battle repair, but takes up more deck space.  Trunked funnels allow more deck space but is more expensive, difficult, and time consuming to manufacture and repair.

Depending on the design of the ship and layout of the boilers and manifolds, there can be an additional topside weight savings with either layout.

Edited by Kuckoo
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I think someone mentioned recently that in several of the post-PH battleship repair/refits, they trunked previously double-stack arrangements into South-Dakota-ish single stack arrangements?

For better AA? Like several here have said?

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You can also see it go the other way in the Modified Leanders that served in the RAN, they had seperate boiler and machinery rooms and in turn had two funnels instead of one. 

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For example, Kirishima (Kongo class BB) lost a funnel in the refit between the two wars, as they changed the machinery around, so they didn't need the 3rd funnel anymore.

 

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It's a little bit more complicated than just, 'They placed the engine rooms x far apart,' or 'had this many separate engine rooms.' We still have this issue today in ship building and the short version is, while yes, Engineering plant size/location/split effects it (although we seldom do that last one in either civil or naval builds anymore) it also has to do with the operating temperatures (function of pressure). That's why on modern ships you'll see *two* funnels, but they'll be side by side:

636221467708219713-005.jpgcristophe_lng_trial.jpg

The reason it is done like this, and why number of funnels also matters, is that it is a function of distance (volume, really) to how fast you can cool down those gases coming off of the engineering plants (this is why having a CE Degree works for ship design) and you cannot vent certain temperature gases through certain amounts of space/thickness of walls. A boiler is *designed* expressly to allow gases and liquids within it to be in the hundreds, if not thousands, of degrees (or equivalent when account for pressure differentials through a phase diagram) but typically the metals and other construction materials  throughout a ship are not, and thus venting ALL those gases through a single location, a single funnel, can represent a serious hazard on a ship. On a warship, vs. a Cruise ship, this is potentially worse as you have VERY temperature sensitiveness materials all over the place, but even still. you don't want what amounts to 500 degree C flue gases just flowing in 1 location, because they may still be 200 degrees as they exit the funnel, and can effectively air fry anyone in a spotting top aft or forward of the funnel depending on the wind conditions and movement of the ship.

So if that's the case, you will actually vent the gases, not trucked into a single funnel, but actually deliberately separate them. Since the Iowa's used a mack, I assume this was a problem to a degree, and why they have two funnels instead of a single trunked one.

Edited by _RC1138

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This is a nice thread...I wish we had more like it. OP you can leave gulag. 1 night only.

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It depends on design goals. In most cases, you don't want to have your uptakes run long stretches horizontally, as battle damage to them could potentially contaminate more ship spaces and superstructure with flue gasses. This was actually a concern raised about the Alaska-class cruisers. However, reducing the number of funnels can also improve the sectors of fire for your AA mounts. So the placement of funnels is really what is considered the best compromise, especially with treaty battleships and the limitations on displacements and it varies for each design, there isn't really a "rule", so to say. Here are a few specific designs and how they trunk their exhaust.

South Dakota (1939): The powerplant consisted of eight boilers and four turbine sets for 130,000 SHP, and they are arranged in four longitudinal compartments, with each compartment containing a pair of boilers and turbines that drives one shaft, and arranged in staggered fashion like so:

B|E|B|E
E|B|E|B

Because the front machinery compartments results in long shaft runs, the boilers are actually placed above the shafts. The short and compact nature of the South Dakotas (shorter than North Carolina while generating more power), they were able to trunk all of the boiler uptakes into one funnel.

Iowa: The powerplant, while also having eight boilers and four turbine sets, is substantially more powerful at 212,000 SHP and thus longer than the South Dakota's, and the extra space meant that the machinery spaces are heavily subdivided, twice as subdivided that of the South Dakotas. Longitudinally, the four engine (E) and four boiler (B) rooms are arranged in alternating sequential fashion, eight longitudinal compartments in total like so:

B|E|B|E|B|E|B|E

Each boiler and engine room pair powers one shaft, and this sequential subdivision ensures that one torpedo hit can only flood at most one boiler and engine room pair. Because of this alternating arrangement, the front funnel is for flue gasses of the front two boiler rooms, and the rear funnel is for the flue gasses of the rear boiler rooms.

Yamato: In contrast to the American system of staggering and longitudinally alternating the boiler and engine spaces, the Yamato groups all of its twelve boilers in the front half of the machinery spaces. The boilers are arranged in three rows longitudinally, four abreast of each other in the traverse direction, with each boiler in its own compartment. Because all of the boilers are grouped together, all of the exhaust and flue gasses can then be trunked into one funnel. The engine rooms of the yamato are also arranged roughly inline with each other longitudinally, four abeast and each divided from each other with longitudinal bulkheads. The overall arrangement looks like this:

E|B|B|B
E|B|B|B
E|B|B|B
E|B|B|B

The Yamato had extensive longitudinal bulkheads in the machinery spaces in contrast to the American arrangement, which abandoned longitudinal bulkheads to mitigate the risk of asymmetric flooding and subsequent capsizing. This four-abreast arrangement of boilers and turbines meant that despite the Yamato's great beam, the TDS depth is actually rather shallow, 5.1 m (without liquid loading either) compared to the South Dakota's and Iowa's 5.45 m. Note that the machinery of the Yamato demonstrates how much more advanced American steam turbine technology was; the Iowa's eight boilers can provide 212,000 SHP while Yamato's twlve boilers provide 150,000 SHP.

Edited by DeliciousFart
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3 hours ago, Estimated_Prophet said:

I think someone mentioned recently that in several of the post-PH battleship repair/refits, they trunked previously double-stack arrangements into South-Dakota-ish single stack arrangements?

For better AA? Like several here have said?

Yes. It both cleared deck space for more AA, and gave that AA much better fields of fire. 

SD class as built before:

Spoiler

See the source image

West Virginia after:

Spoiler

See the source image

I think they also used SD as the template for the redesign because the old BBs were closer in length to SD. A modified SD superstructure just made more sense than NC and required less squishing, especially since the NCs were somewhat longer. 

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3 hours ago, Estimated_Prophet said:

I think someone mentioned recently that in several of the post-PH battleship repair/refits, they trunked previously double-stack arrangements into South-Dakota-ish single stack arrangements?

For better AA? Like several here have said?

Yes. Both the Tennessee class battleships, (USS Tennessee and USS California) as well as the Colorado class, USS West Virginia had extensive rebuilds. Both California and West Virginia were severely damaged at Pearl, both being sunk, salvaged and completely rebuilt. USS Tennessee on the other hand, being inboard of West Virginia didnt take much of a beating. She took two bomb hits, one failing to detonate in turret 3 and one hitting the center 14" gun of turret 2, which incidentally mortally wounded West Virginia's skipper, Capt  Mervyn Bennion from the bomb fragments. Tennessee's major threat was the burning fuel oil from the wrecked Arizona just aft of her, which the heat did buckle several hull plates on Tennessee's stern. Tennessee was quickly repaired and underwent a overhaul stateside that changed her features considerably. While the Guadalcanal campaign was underway, Tennessee was selected to receive her second phase of her overhaul after which, she was completely changed as well. They had the more compact "cruiser" style superstructures as seen on the South Dakota class with single funnels trunked into the back of the forward fire-control tower. Also had sixteen 5"/38 DP guns mounted in dual mounts, eight per side. Had massive torpedo blister tanks added, not only for additional protection, but mainly to reclaim lost buoyancy as the three ships gained nearly 10,000 tons displacement in their modernization.  The blisters took their beam from 98ft wide, to 114ft wide, making them too wide to transit the Panama Canal. And of course with those refits also came the upgraded AA suite and the most up-to-date radar and fire-control systems (which played a large role in the Battle of Surigao Strait). The rest of the older battleships received very little to moderate upgrades. Most of which was to cut down the old remaining cage masts or restructuring around them. For example the cage foremast of the USS Colorado, USS Maryland and on all three New Mexico class ships were still intact by wars end, just the structure was rebuilt up and around it, while the rear cage or tripod (depending on ships) mainmasts were all removed completely. This opened up firing arcs for the newly installed 40mm Bofors and 20mm Orelikon AA suites and 5"/38 DP mounts for some ships, like Pennsylvania.

 

 

 

In the Battle of Surigao Straits, the upgraded West Virginia, California and Tennessee held a significant advantage over the Pennsylvania, Maryland and Mississippi. The West Virginia struck the Japanese battleship, Yamashiro, in her first salvo. California and Tennessee also was able to achieve a quick firing solution via radar and was  fairly accurate, firing  some sixty-five 14" AP shells a piece. The Maryland was only able to visually spot shell splashes later in the engagement and joined in. Mississippi fired just one salvo and the final salvo of the battle. Pennsylvania herself, was unable to plot a firing solution at all and never fired a main battery salvo in the entire night time engagement. 

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Remember, it is not about how many stacks you have but how big they are. :cap_book:

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This was a great change of pace.

I speak with no authority of WW2 ships, but in the modern military, there are many trade offs and advantages provided by every design decision. I would bet we only scratched the surface, there could be 100 or more trade offs made by each choice.

Really just so happy to see a thread that isnt trolling, is geniunly interested, not whining, or not showing off!

 

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2 hours ago, DeliciousFart said:

Note that the machinery of the Yamato demonstrates how much more advanced American steam turbine technology was; the Iowa's eight boilers can provide 212,000 SHP while Yamato's twlve boilers provide 150,000 SHP.

This was an intentional decision. Efficiency and power were poor for the time but they chose power plants that were well established in reliability. Last thing you want to do is put new technology inside all that armor. Had Yamato been launched when the Iowa's were, without any wartime shortages of course, there is every possibility it would of had similar SHP.

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15 hours ago, ksix said:

This was an intentional decision. Efficiency and power were poor for the time but they chose power plants that were well established in reliability. Last thing you want to do is put new technology inside all that armor. Had Yamato been launched when the Iowa's were, without any wartime shortages of course, there is every possibility it would of had similar SHP.

No. The Yamato had boilers that operated at 350 psi and 625 degrees F, whereas the North Carolina which had similar construction and launch dates had 575 psi and 850 degrees F. The fact that the Japanese intentionally chose lower pressure and temperature boilers for increased reliability simply reinforces the fact that their steam turbine technology is behind that of the US.

 

Based on your comment, I don't think you understand naval architecture very well; in general you don't just set your propulsive power arbitrarily; your powerplant is the result of your speed and endurance requirements. There's no reason for the Yamato to be designed with similar propulsive power as the Iowa simply because there was no need to do so. For example, during the design process of the Montana, propulsive power was actually decreased from 212,000 SHP to 172,000 SHP because the former was more than necessary for achieving the design speed of 28 knots. Furthermore, even if the Japanese decided to increase power and speed, that would result in more boilers and size increases that would make the ships even larger, something that the Japanese weren't exactly keen on doing; even when designing the A-150, they settled for a design that had 3x2 20.1 cm guns and displacement close to the Yamatos as larger designs were seen as impractical.

Edited by DeliciousFart

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The number of funnels on a ship doesn't really affect anything in-game. As far as this game goes, it's pretty much cosmetic. In real life, it was ventilation for the engines. A useful utility the smokestacks offered is smoke screens.

Not the clouds that linger like in WoWS. In reality, they looked more like this: (yes, there were both white and black smokescreens, though they formed a wall rather than a cloud)

Spoiler

Image result for WW2 warship smoke screenImage result for WW2 warship smoke screen

 

But, BB in this game do not have the ability to lay a smoke screen, so it's kinda moot. As for the reasoning behind the number of stacks, it's usually based on the volume of exhaust gasses the boilers produce. Bigger engines = more stacks & larger stack size.

 

Yamato and Bismarck's funnels are very large, single funnels, while a ship like Iowa has 2 moderately sized funnels. It helps with exhaust management. Hope that kinda helps.

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I'm assuming that more funnels in a late generation Fast Battleship means it contains more boiler rooms, and therefore more engine power.

Old generation Battleships used coal, and could not cluster their boiler rooms so they had to use more then one funnel.

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It’s also not just exhaust. But propulsion plants require a lot of air as well.  Not just steam boilers but also modern gas turbine engines (navalized jet engine)

for steam boilers there are forced draft blowers which take air from the outside and force it into the firebox / boiler furnace.  

On gas turbine ships the intake air surrounds the exhaust stack providing two benefits. The cooler intake air cools the hotter exhaust and reduces the thermal signature of the ship against infrared anti ship missiles and the exhaust air warms up the intake air for antiicing of the engines. Since they are jet engines any ice would not be welcome against the compressor fan blades.

in addition the uptake space on a modern ship is also the means of extraction for the gas turbine engine in the event the ship needs an engine change.

i don’t know whether the air intakes are combined with the exhaust stacks on World War Two ships.

 

on one of the carrier museums (midway I think) the general exit for the Carrier back to the pier they cut through the uptake stack/space to create the pedestrian exit. I guess since the ships boilers will never be relit it doesn’t need uptake spaces anymore so the museum repurposed the exhaust stack for the pedestrian exit.

Edited by wtfovr
Added info for engine change

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