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bsbr

Iowa/Missouri speed mistake?

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image.png.f019c1709c4f8f92338f07aa76c0b47c.png

 

So Iowa class only did 31.9 knot when overloading the engines. Operating speed is about 31 knots and in Pacific they're good for 30.7 knots. So Iowa speed in game too high? 33 knot can't be done in full load like in game.

https://forum.worldofwarships.com/topic/70407-yamato-vs-iowa/?page=6&tab=comments#comment-1749526

Summary:

 

1. 33 knots was never tested or achieved.

2. Theoretical calculations show that 33.5 knots for a fully loaded Iowa was possible, but only by overloading the power plant to the limits.

3. Fastest tested speed was 31.9 knots by overloading the power plant.

4. Based on model tests, 31 knots was considered the operating speed.

5. The Pacific Fleet considered 30.7 knots as good for average conditions.

Edited by bsbr
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Not really, given the fact that the trials we're considering unrepresentative because they were in shallow waters, which would result in lower speeds. This is why so many of the WWI KM Dreadnoughts got lower results on trials than they were able to make in deeper waters.

 

As for the 31 and 30.7 knot figures, that's taking into account things such as fouling - generally something not considered when taking into account a ship's top speed, otherwise almost every ship in the game would shed 1-2 knots.

 

At operational load 32.5 knots is probably the most realistic number, but 33 knots could be reached too.

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2 minutes ago, Phoenix_jz said:

Not really, given the fact that the trials we're considering unrepresentative because they were in shallow waters, which would result in lower speeds. This is why so many of the WWI KM Dreadnoughts got lower results on trials than they were able to make in deeper waters.

 

As for the 31 and 30.7 knot figures, that's taking into account things such as fouling - generally something not considered when taking into account a ship's top speed, otherwise almost every ship in the game would shed 1-2 knots.

 

At operational load 32.5 knots is probably the most realistic number, but 33 knots could be reached too.

Proof?

https://forum.worldofwarships.com/topic/70407-yamato-vs-iowa/?page=6&tab=comments#comment-1749526

Summary:

 

1. 33 knots was never tested or achieved.

2. Theoretical calculations show that 33.5 knots for a fully loaded Iowa was possible, but only by overloading the power plant to the limits.

3. Fastest tested speed was 31.9 knots by overloading the power plant.

4. Based on model tests, 31 knots was considered the operating speed.

5. The Pacific Fleet considered 30.7 knots as good for average conditions.

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@bsbr There is a signal flag for a 5% speed increase that can be used on any ship. If you must have a knot or 2 max speed Fly It!

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With all the kvetching it took about 2 years ago(and all the time before that, which goes back into CBT, which I wasn't a part of) to get Iowa her 33kt speed, and you wanna undo it?

Heck, I'm not a fan of the boat in-game, but really, there's no point in changing this. Not after what it took to get her the current speed.

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43 minutes ago, bsbr said:

Proof?

https://forum.worldofwarships.com/topic/70407-yamato-vs-iowa/?page=6&tab=comments#comment-1749526

Summary:

 

1. 33 knots was never tested or achieved.

2. Theoretical calculations show that 33.5 knots for a fully loaded Iowa was possible, but only by overloading the power plant to the limits.

3. Fastest tested speed was 31.9 knots by overloading the power plant.

4. Based on model tests, 31 knots was considered the operating speed.

5. The Pacific Fleet considered 30.7 knots as good for average conditions.

You didn't read half of what I said.

 

1. Correct - but that doesn't mean the weren't capable of it, especially when we have numbers from when they were in active service - for example, both Iowa and New Jersey made 32.5 knots chasing the Japanese DD Nowaki.

 

2. This is true - but then again many ships in-game get their trial figures running at extra power, half fuel load, no ammo, and no turrets or directors! So it somewhat makes the topic as a whole rather pointless, as we could easily throw 35 knots at Iowa by using the same logic as other ships in-game.

 

3, 4, & 5. I already addressed this. The rest mentioned in #3 was run in shallow waters - thus, this does not equate to regular deep-watee figures. See the HSF during WWII as an example. The other examples take into account things such as hull fouling and less than perfect seas. Thus, this does not equate to the 'top speed' rating of other ships, especially not those used by WG in WoWs.

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Due to wartime, the ships never ever got a proper trials run.

As the war continued, their displacement increased with more AAA added as well as the increased crew.

 

In 1968, New Jersey was recommissioned without the AAA guns and extra crew. She was as 'basic' as could be and hit 35.2 knots reportedly.

 http://www.guinnessworldrecords.com/world-records/fastest-speed-recorded-for-a-battleship/

When they came back into service in the 1980s, the rest lost their AAA, they all lost 4 5in guns, but gained weight in 8 armored tomahawk launchers, harpoons, and other modern equipment, thus slowing them down.

 

The official US Navy page on them pegs them at 33knots.

http://www.navy.mil/navydata/nav_legacy.asp?id=129

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If you want to remove unrealized expectations in the Iowa class in game you would have to keel haul most other ships and just about the entire line of Russian paper ships.

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I'm not sure how this converts to speed, but I do know the following regarding the horsepower of the Iowa classes:

The US navy has a habit of leaning on the side of caution when listing technical specifications. With regards to engine power, they usually include a "10% overload" buffer zone which can be used safely with zero damage to the boilers and turbines (in fact, the engines aren't even governed).

In the case of the Iowa classes listed shaft horsepower (shp) of 212k, the contractor—General Electric—had already calculated in the buffer zone at 233k shp, but the navy didn't realize this and further reduced it by another 10%, resulting in the current 212k listed number, which everyone just decided to run with.

Thus, in reality, the maximum shp (ignoring the overload zone) of the Iowa classes is probably something around 256k, but you're liable to damage something at those speeds, so 233k shps is a more realistic number.

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1 hour ago, Phoenix_jz said:

You didn't read half of what I said.

 

1. Correct - but that doesn't mean the weren't capable of it, especially when we have numbers from when they were in active service - for example, both Iowa and New Jersey made 32.5 knots chasing the Japanese DD Nowaki.

 

2. This is true - but then again many ships in-game get their trial figures running at extra power, half fuel load, no ammo, and no turrets or directors! So it somewhat makes the topic as a whole rather pointless, as we could easily throw 35 knots at Iowa by using the same logic as other ships in-game.

 

3, 4, & 5. I already addressed this. The rest mentioned in #3 was run in shallow waters - thus, this does not equate to regular deep-watee figures. See the HSF during WWII as an example. The other examples take into account things such as hull fouling and less than perfect seas. Thus, this does not equate to the 'top speed' rating of other ships, especially not those used by WG in WoWs.

New Jersey need overload to 221,000 horsepower to go 31.9 knots. 35 knots need power thats impossible to make.

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24 minutes ago, bsbr said:

New Jersey need overload to 221,000 horsepower to go 31.9 knots. 35 knots need power thats impossible to make.

Well, during her shakedown cruise in 1968 the New Jersey made 35.2 knots and held it for six hours on her 8 oil fired boilers. So maybe not so impossible.

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38 minutes ago, bsbr said:

New Jersey need overload to 221,000 horsepower to go 31.9 knots. 35 knots need power thats impossible to make.

I thought we were discussing 32.5 to 33 knots, not 35 knots? Such as speed would not be possible under normal circumstances, and I make no claim as to that being her normal top speed.

 

But again, circumstances matter. NJ herself was able to make 35.2 knots later on in her life, although at a significantly lighter load.

On top of that, we have examples of the Iowa's hitting 32 to 32.5 knots *in combat*, which is generally viewed as the best indicator of performance.

 

But, at the risk of sounding like a broken record - you're listing results from shallow water trials, which are not indicative of deep-water performance. This is why the figures that correct for circumstances credit equivalency to 32.5 knots.

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3 hours ago, Avenge_December_7 said:

In the case of the Iowa classes listed shaft horsepower (shp) of 212k, the contractor—General Electric—had already calculated in the buffer zone at 233k shp, but the navy didn't realize this and further reduced it by another 10%, resulting in the current 212k listed number, which everyone just decided to run with.

 

A simple reduction gear accounts for between 8% and 12% loss of computed power, a more complex reduction gear set you can quite easily be looking at 20% or more computed power loss.

 

Based on 4 shafts, with one high pressure and one low pressure turbine per shaft, you’re looking at your looking at ~10% loss based on a simple single reduction of 9.3333:1, you will also be looking at some power loss in connecting the high and low pressure turbines to the reduction gear set.

 

Or in other words, you would require a compound turbine set with an output ~64,000SHP per set (256,000SHP total) to deliver the normal 53,000SHP at each propeller shaft after the reduction gear-set (total 212,000SHP), which would give ~57,600SHP at overload per shaft (total 230,400SHP), meaning overload is just under +9%, given the ~10% reduction gear losses.

 

Maths:

64,000SHP gross power at compound turbine output – 10% = ~57,600SHP overload power at propeller shaft.

53,000SHP nominal power at propeller shaft + 9% = ~57,770SHP overload power at propeller shaft.

 

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5 hours ago, Phoenix_jz said:

I thought we were discussing 32.5 to 33 knots, not 35 knots? Such as speed would not be possible under normal circumstances, and I make no claim as to that being her normal top speed.

 

But again, circumstances matter. NJ herself was able to make 35.2 knots later on in her life, although at a significantly lighter load.

On top of that, we have examples of the Iowa's hitting 32 to 32.5 knots *in combat*, which is generally viewed as the best indicator of performance.

 

But, at the risk of sounding like a broken record - you're listing results from shallow water trials, which are not indicative of deep-water performance. This is why the figures that correct for circumstances credit equivalency to 32.5 knots.

Proof of 32.5 knots in combat? Ship speed indicator in combat can be inaccurate because its not calibrated. 31.9 knots by New Jersey did not say it was shallow water and it needs overload engines to get that speed. 32.5 can only be at lighter weight.

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22 minutes ago, bsbr said:

Proof of 32.5 knots in combat? Ship speed indicator in combat can be inaccurate because its not calibrated. 31.9 knots by New Jersey did not say it was shallow water and it needs overload engines to get that speed. 32.5 can only be at lighter weight.

 

Iowa has more likely achieved 33 knots in combat than the Khabarovsk and Zao achieved 1 knot in combat.

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BTW: 33kts was at normal displacement, which is all crew and 2/3 of stores, ammunition, fuel and boilers full of water producing steam.

 

on the basis of fuel alone of which there was a maximum capacity of 8,841 long tons, and based on 57,540 long tons full load, there would be 2947 long tons less fuel, which takes displacement down to 54,593 long tons, taking shells into account, based on 1,220 x 16" AP shells, there would be 406 fewer 16" shells, which would be a saving of a further ~490 long tons, bringing the displacement down to less than <54,103 long tons, meaning there is probably another 500 long ton to 1000 long ton that can be knocked of the <54,103 long tons, to account for 2/3 food etc, other ammunition and propellant charges at which 33kts would be attained.

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5 hours ago, bsbr said:

Proof of 32.5 knots in combat? Ship speed indicator in combat can be inaccurate because its not calibrated. 31.9 knots by New Jersey did not say it was shallow water and it needs overload engines to get that speed. 32.5 can only be at lighter weight.

I don't have the necessary resources to prove or disprove whether or not they actually hit 32.5 knots, but that's what the plotting tables from the action indicate if I'm remembering correctly.

While the quoted article does not specifically state that the December trial was done in shallow water, it really doesn't need to - all trials in 1943 were run in shallow waters because of the U-boat threat. It's also worth noting that the December trial was run at a displacement exceeding even full load.

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13 hours ago, Prothall said:

If you want to remove unrealized expectations in the Iowa class in game you would have to keel haul most other ships and just about the entire line of Russian paper ships.

+1

^^ This was immediately the first thing that came to mind.  It's obvious.

It's fallacious and silly for anyone to make such a point of citing realism and historical figures to cherry-pick over one aspect of one ship in this game.  Yet we see some people here do it all the time.

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Here's data from Iowa's 1985 sea trials.

http://www.navweaps.com/index_tech/tech-104_BB61_Sea_Trial.pdf

Iowa made 31.0 knots at 186,260 SHP and 55,960 long tons, with 71 days out of drydock (so some bottom fouling). Using this data, as well as other speed and power data points collected during the trial, resulted in a calculated speed of 32.25 knots at 212,000 SHP. Furthermore, if you consider that the "trial" displacement is about 2,000 tons less at 53,900 long tons, and with each 1,000 long ton estimated to have quarter knot difference, then Iowa is good for 32.75 knots. With bottom fouling taken into account, ~33 knots is a completely reasonable speed to attain.

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16 hours ago, bsbr said:

4. Based on model tests, 31 knots was considered the operating speed.

And you forgot to read your source properly. I quote:

"All of these data taken together suggest an operating speed of about 31 knots, bottom fouling and sea state having been taken into account."

Bottom fouling becomes a factor when you stay on the sea for quite some time, like the North Carolina-class USS Washington staying on open water for four months at one point. You won't believe how much life will form underneath your butt. And that affects the speed of any ship. And sea state is when you take into consideration that you want to operate your ship outside a bathtub. On an actual ocean in somewhat rough weather any ship, be it British, Japanese, German or American, will lose speed. None of the ships in-game take that the aforementioned into consideration, so why should the Iowas have it taken into consideration now?

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Another thread from everyone's favorite anti-USN ship hater. :cap_tea:

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No proof that Iowa actually ever reach 33 knot, just optimistic prediction. If using trial speed then other ships should be faster too. Yamato can go 30 knots, only 3 knot slower than Iowa.

9C57AF66-A9F6-43BD-BA9E-01D627389116.jpeg

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5 minutes ago, bsbr said:

No proof that Iowa actually ever reach 33 knot, just optimistic prediction. If using trial speed then other ships should be faster too. Yamato can go 30 knots, only 3 knot slower than Iowa.

9C57AF66-A9F6-43BD-BA9E-01D627389116.jpeg

Substantiate your claim with more than a secondary source that itself states that this was entirely unofficial and simple hearsay from a singular, anonymous, crew member.

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Ah yes, just like all those times CVN crew members remembered their ships going 45+ knots, despite it being physically impossible. I guess we should go update the wiki pages to accurately reflect this new method of determining speed.

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