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DeliciousFart

Iowa vs. Montana size comparison

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YOXweLz.png

 

 

hg7xg73.jpg

On the internet I see a bunch of size comparisons between the Iowa and Montana classes, and unfortunately some of them get the proportions of the Montana comically wrong. So, to set the record straight, here's an actual size comparison of the Iowa and Montana classes, with specs below. The drawings are from shipbucket.

  Montana (1942 design) Iowa (WW2 configuration)
Length (waterline) 890.0 ft (271.3 m) 860.0 ft (262.1 m)
Length (overall) 925.0 ft (281.9 m) 887.3 ft (270.4 m)
Beam 121.2 ft (36.9 m) 108.2 ft (33.0 m)
Draft 36.9 ft (11.2 m) 37.2 ft (11.3 m)
Displacement 70,965 long tons 57,540 long tons
Power 172,000 SHP 212,000 SHP
Design Speed 28 knots 33 knots
Armament 4x3 16"/50 Mark 7, 10x2 5"/54 Mark 16 3x3 16"/50 Mark 7, 10x2 5"/38 Mark 12

You can see that dimensionally, in terms of length the Montana isn't much longer than the Iowa. However, it is considerably beamier and also has a fuller hull form, allowing for an additional turret and much more extensively sub-divided machinery spaces. The armor is considerably thicker as well, 409 mm on Montana compared to 307 mm on Iowa. Note that the Montana displacement would probably be 2,000-3,000 tons heavier than the listed design value due to the large increases in AA guns that would've been carried had the ships actually been completed.

EDIT: Added top-down view comparison.

Edited by DeliciousFart
added top-down view comparison
  • Cool 2

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To resurrect an old thread, simply comparing the side view of the Iowa and Montana don't do the two ships justice. Here is a top down view comparison, and it really shows the increased beam of the Montana compared to the Iowa, thus better illustrating the ~14,000 ton displacement difference between the two ships.

 

hg7xg73.jpg

Edited by DeliciousFart

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both are such gorgeous ships

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To further elaborate on some differences in the internal arrangement of the Iowa and Montana, let's look at how their propulsion plants are arranged. The Iowa's powerplant consists of having eight boilers and four turbine sets producing 212,000 SHP. 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. Longitudinally, the four engine and four boiler rooms are arranged in alternating sequential fashion, eight longitudinal compartments in total like so:

image.thumb.png.a3bf872148b4bf29304d3127ddc9f73e.png

The Montana powerplant also has eight boilers and four turbine sets but the power output is 172,000 SHP and the arrangement is very different and has very extensive subdivisions of machinery in the traverse direction as well, in contrast to the North Carolina, South Dakota, and Iowa classes. The turbines sets for the two center shafts are placed along the center in their own traversely divided compartments, and divided from each other longitudinally as well. The boilers here flank the center shaft turbines in separate traversely divided compartments and are longitudinally alternating with the turbines for the outboard shafts. The subdivision is very extensive and largely allowed because of the considerably greater beam of the Montana. You can see the extensive subdivision from this screenshot from Navsource.

image.thumb.png.6c48c824fdc963416e11986d35a3faa0.png

Edited by DeliciousFart

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So Montana couldn't transit the Canal?

Also interesting, the rearrangement of amid-ship secondaries.

 

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On ‎12‎/‎25‎/‎2017 at 11:35 PM, DeliciousFart said:

YOXweLz.png

 

 

hg7xg73.jpg

On the internet I see a bunch of size comparisons between the Iowa and Montana classes, and unfortunately some of them get the proportions of the Montana comically wrong. So, to set the record straight, here's an actual size comparison of the Iowa and Montana classes, with specs below. The drawings are from shipbucket.

  Montana (1942 design) Iowa (WW2 configuration)
Length (waterline) 890.0 ft (271.3 m) 860.0 ft (262.1 m)
Length (overall) 925.0 ft (281.9 m) 887.3 ft (270.4 m)
Beam 121.2 ft (36.9 m) 108.3 ft (33.0 m)
Draft 36.9 ft (11.2 m) 37.2 ft (11.3 m)
Displacement 70,965 long tons 57,540 long tons
Power 172,000 SHP 212,000 SHP
Design Speed 28 knots 33 knots
Armament 4x3 16"/50 Mark 7, 10x2 5"/54 Mark 16 3x3 16"/50 Mark 7, 10x2 5"/38 Mark 12

You can see that dimensionally, in terms of length the Montana isn't much longer than the Iowa. However, it is considerably beamier and also has a fuller hull form, allowing for an additional turret and much more extensively sub-divided machinery spaces. Note that the Montana displacement would probably be 2,000-3,000 tons heavier than the listed design value due to the large increases in AA guns that would've been carried had the ships actually been completed.

EDIT: Added top-down view comparison.

Ty. I always wondered about how they compared size-wise. 

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2 hours ago, iDuckman said:

So Montana couldn't transit the Canal?

Also interesting, the rearrangement of amid-ship secondaries.

 

No. That was explicitly one of the things that was given up in the Montana design - the expectation was that the Montanas would be Pacific-Ocean only deployment, so there was no need to have them fit through the Canal.

The maximum width of a ship for the Panama Canal is 110 feet. (That's being changed right now as they put in new locks).

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3 hours ago, EAnybody said:

No. That was explicitly one of the things that was given up in the Montana design - the expectation was that the Montanas would be Pacific-Ocean only deployment, so there was no need to have them fit through the Canal.

The maximum width of a ship for the Panama Canal is 110 feet. (That's being changed right now as they put in new locks).

The Montana was designed with a third set of locks planned as well. These new locks would've been 140 ft wide and normally reserved for USN ships.

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I'm guessing back when the Montana class was designed for 212,000 shp (which was found to be more than what was needed for 28 knots) the machinery spaces weren't as extensively subdivided.

Edited by Lampshade_M1A2

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To further illustrate the difference in length between Iowa machinery and Montana machinery, here is a scan from Friedman's U.S. Battleships that compares the two. You can see here that the Montana machinery is considerably shorter, both as a result of the Montana's greater beam and less powerful powerplant; this is why despite the additional gun turret, the Montana is not much longer than the Iowa.

image.thumb.png.f39842cd90a641b8ab5a724ccb5f7c27.png

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