Bismarck and European battleships vs.US battleships - hull shape and seakeeping qualities.

[TTTT]

The hull shape of Bismarck and other European battleships were radically different from the new US battleships (and Yamato). While Bismarck and the Europeans had the "classical shape" with a very wide, but rather small, midsection becoming gradually narrower both in front and aft, the US battleships had a very narrow bow section, but very wide mid and aft section.

While ships like Bismarck, HMS Vanguard, KGV and Richelieu were regarded as very good seaboats, the US battleships were seemingly not. I've read that USS Washington received a lot of criticism from the British for her seakeeping qualities while she was serving with the Home Fleet, and USS Iowa did not impress in heavy weather in the post war NATO exercise "Mariner" in 1953, where she had to drop speed considerably and cease fire, all the while HMS Vanguard was moving happily along at near top speed.

The wide hull also made them a beefier target for plunging fire and bombs.

Then what's the reason for this design choice in the US battleships, and had the hull shape any advantages? More space for machinery?

[Joe100]

American battleships, especially evident on the Iowa class, used that hull shape for speed. Long, thin, hulls are faster than wide hulls. To get an 800+ foot battleship to 33kts, one has to have 210,000hp+ and the most optimized hull. The power to speed curve goes up exponentially, so one needs everything in their favor. Bismarck, 150,000hp for 30 and a bit knots, 212,000hp for 33kts.

The Japanese realized this too with the Yamatos but didn’t take it to the extent of the Americans.

Bismarck was designed the way she was to minimize her draught to an extent. She had limitations the Americans, Japanese, and British didn’t have to worry about. Of course there are other factors, but we’re simplifying here.

Every battleship design is some sort of compromise and the Americans chose to sacrifice seakeeping for speed.

[TTTT]

Yes, but that doesn't explain the wide aft section on the newer US battleships as well as Yamato. And both the speed and especially the range of the latter was not especially impressive.

The preceding classes, Colorado and Nagato, were much more similar to European ships.

[marcelo_malara]

The Iowa class seems to have a very long and thin entrance, that would make the bow less buoyant, and for sure is the culprit of her bad seakeeping. This, as commented, was surely to give her more speed. The fullness of the stern is a little more difficult to explain, may be it is related to the need of internal volume, or may be it was determined that it would not harm her speed, remember than most cruisers of the late war had a transom stern, which by definition is wide.

Regards

[Byron Angel]

The hull shape of Bismarck and other European battleships were radically different from the new US battleships (and Yamato). While Bismarck and the Europeans had the "classical shape" with a very wide, but rather small, midsection becoming gradually narrower both in front and aft, the US battleships had a very narrow bow section, but very wide mid and aft section.

While ships like Bismarck, HMS Vanguard, KGV and Richelieu were regarded as very good seaboats, the US battleships were seemingly not. I've read that USS Washington received a lot of criticism from the British for her seakeeping qualities while she was serving with the Home Fleet, and USS Iowa did not impress in heavy weather in the post war NATO exercise "Mariner" in 1953, where she had to drop speed considerably and cease fire, all the while HMS Vanguard was moving happily along at near top speed.

The wide hull also made them a beefier target for plunging fire and bombs.

Then what's the reason for this design choice in the US battleships, and had the hull shape any advantages? More space for machinery?

[hans zurbriggen]

Hello,
In addition to speed emphasis, I have always thought that "non-classical" shape of US BB's was due to Panama Channel max width of 33.5 meters. Bismarck could not pass through (36 meters), while US designers were required to design their BB's to enable moving them quickly from one ocean to another. AFAIK Montana class BB's design was not required to cope this requirement.

I don't know why such a large stern, possibly a consequence of propulsion plant design ? Bismarck 3 shafts design allowed thinner stern then others.

hans

[paul.mercer]

Gentlemen,
Out of interest, I've often wondered if the long slender bows on the Iowa's would have been very vulnerable in fight either from shells or bombs?

[OpanaPointer]

Every battleship design is some sort of compromise and the Americans chose to sacrifice seakeeping for speed.

The basic criteria: Power + Protection + Endurance = 1

I picture a set of sliding scales, interlocked so pushing one up pushes the other two down.

[TTTT]

Battleships.jpg

(151.1 KiB) Not downloaded yet

Left to right: Richelieu, KGV, Baden, Bismarck, Yamato, Nagato, Colorado, North Carolina, South Dakota and Iowa.

[marcelo_malara]

Battleships.jpg

Left to right: Richelieu, KGV, Baden, Bismarck, Yamato, Nagato, Colorado, North Carolina, South Dakota and Iowa.

Well, the hangar in the stern may be responsible too.

[Byron Angel]

See "Operational Experience of Fast Battleships: World War II, Korea, Vietnam". US battleships were not deficient in seaworthiness, but they were considered "wet" ships due to the fine bow entry mentioned by the OP. This extended through the IOWA Class and it was recommended that new BB construction feature a fuller hull form forward to resolve the problem. Here is what the fleet review committee convened by Admiral Nimitz immediately after the surrender of Japan reported with respect to the IOWA class:

b. SEAWORTHINESS
( 1 ) The seaworthiness of the IOWA class is excellent. The ships are steady gun platforms and they have good stability in all conditions of loading and weather. They have a good freeboard, but are wetter, from Turret II aft, than seems proper for ships of their size. This wetness seems due to the the sudden and extreme widening of the hull lines just forward of Turret I. It is understood that the narrow forecastle , distinctive to this class, was adopted to save overall weight and as a means of avoiding the necessity for providing support for the weight of a heavier bow structure forward of the armored box.
( 2 ) In future design an attempt should be made to broaden the bow lines above the waterline to provide a drier and more roomy ship, and one with more reserve buoyancy forward. The wetness of the present ships has been of no concern in the normally smooth South or Central Pacific, but would be a decidedly undesirable feature if they were to be employed in other waters, such as the North Atlantic.

To sum up, the fast US battleship classes were designed for operations in the Pacific. Had they been intended for service in the North Atlantic, they may very likely have displayed materially different design aspects. It is also worth keeping in mind that these US battleships safely weathered major typhoon events in the Pacific.

FWIW - the KGV Class were considered to be notoriously "wet" ships as well, but for different reasons - they lacked both bow flare and forward sheer. which resulted in green seas coming over the bow and washing out the forward turret. This occurred with PoW at Denmark Strait and with DoY at North Cape.


Byron

[marcelo_malara]

See "Operational Experience of Fast Battleships: World War II, Korea, Vietnam". US battleships were not deficient in seaworthiness, but they were considered "wet" ships due to the fine bow entry mentioned by the OP. This extended through the IOWA Class and it was recommended that new BB construction feature a fuller hull form forward to resolve the problem. Here is what the fleet review committee convened by Admiral Nimitz immediately after the surrender of Japan reported with respect to the IOWA class:

b. SEAWORTHINESS
( 1 ) The seaworthiness of the IOWA class is excellent. The ships are steady gun platforms and they have good stability in all conditions of loading and weather. They have a good freeboard, but are wetter, from Turret II aft, than seems proper for ships of their size. This wetness seems due to the the sudden and extreme widening of the hull lines just forward of Turret I. It is understood that the narrow forecastle , distinctive to this class, was adopted to save overall weight and as a means of avoiding the necessity for providing support for the weight of a heavier bow structure forward of the armored box.
( 2 ) In future design an attempt should be made to broaden the bow lines above the waterline to provide a drier and more roomy ship, and one with more reserve buoyancy forward. The wetness of the present ships has been of no concern in the normally smooth South or Central Pacific, but would be a decidedly undesirable feature if they were to be employed in other waters, such as the North Atlantic.

To sum up, the fast US battleship classes were designed for operations in the Pacific. Had they been intended for service in the North Atlantic, they may very likely have displayed materially different design aspects. It is also worth keeping in mind that these US battleships safely weathered major typhoon events in the Pacific.

FWIW - the KGV Class were considered to be notoriously "wet" ships as well, but for different reasons - they lacked both bow flare and forward sheer. which resulted in green seas coming over the bow and washing out the forward turret. This occurred with PoW at Denmark Strait and with DoY at North Cape.


Byron

Not to be forgotten, most ships lost the forecastle in post WWI designs. Warspite for instance had two full length decks plus a forecastle above water line, while WWII designs had only the two full length decks, that would rest about 3 m of freeboard in the bow of the ship.

[TTTT]

Supposedly British admirals were seriously concerned about the effect of a serious sea stare on the American ship during the time that American ships were escorting convoys against a possible sortie by Tirpitz. Apparently the “coke bottle” hull shape - with a narrow bow and broad stern - was prone to burying its nose in any kind of sea, making the forward turrets inoperable. This was true for all the three new classes.

During heavy weather in NATO exercise "Mariner" in 1953, HMS Vanguard proved to be a much better seaboat for rough North Atlantic conditions, as Iowa was much wetter and also rolled much more. As stated by Byron above, US Navy's main priority in WW2 was the Pacific, and in the ususal conditions here the new US battleships proved more than good enough,

I guess the main reason for this design choice was to make room for the powerful machinery as well as the 4 propellers? Especially the South Dakota class had a very powerful machinery compared to the overall size of the ship - she was barely longer than a WW1 super-dreadnought. And Iowa was in many ways "just" a longer SD, with the same armor layout, but much longer bow.

[Byron Angel]

Hi TTTT,
Please don't ask me where I read the following; I just don't remember. But I recall reading that a major motivation behind the somewhat unusual hull plan form of the US fast BBs was to maximize the coverage of the anti-torpedo protection system in relation to the length of the ship. In as much as 90+ pct of time spent at sea would have been in the range of 15-20 kts, it makes sense. The experience of USS North Carolina is a good case in point.

As the great American thinker Professor Thomas Sowell is fond of saying: "There are really no solutions, only trade-offs".

B

[dunmunro]

Supposedly British admirals were seriously concerned about the effect of a serious sea stare on the American ship during the time that American ships were escorting convoys against a possible sortie by Tirpitz. Apparently the “coke bottle” hull shape - with a narrow bow and broad stern - was prone to burying its nose in any kind of sea, making the forward turrets inoperable. This was true for all the three new classes.

During heavy weather in NATO exercise "Mariner" in 1953, HMS Vanguard proved to be a much better seaboat for rough North Atlantic conditions, as Iowa was much wetter and also rolled much more. As stated by Byron above, US Navy's main priority in WW2 was the Pacific, and in the ususal conditions here the new US battleships proved more than good enough,

I guess the main reason for this design choice was to make room for the powerful machinery as well as the 4 propellers? Especially the South Dakota class had a very powerful machinery compared to the overall size of the ship - she was barely longer than a WW1 super-dreadnought. And Iowa was in many ways "just" a longer SD, with the same armor layout, but much longer bow.

An interesting read:
http://www.researcheratlarge.com/Ships/ ... amage.html