Battleship Classes and Throw Weights

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Figure 1: USS West Virginia. She demonstrated some of the best battleship gunnery of the war at Surigao Straits. (Wikipedia)

I just finished reading The Battle of Surigao Strait by Anthony Tully, a battle that saw the final clash of battleships. For a battleship aficionado, the climax of the fight was the contest between two Japanese battleships and six US battleships, where five of the six US battleships had been sunk or heavily damaged during the Pearl Harbor attack – only the USS Mississippi had escaped the carnage of Pearl Harbor. These were old battleships (Table 1), with two having been commissioned during WW1 and the rest shortly after the WW1 ended.

When US folks think of WW2 battleships, they generally focus on the Iowa Class, probably because these ships survived the war and avoided the scrap heap. However, they did not begin deployment until 1944, which was after much of the tough surface combat had passed.

Table 1: US Battleships at Surigao Straits

BattleshipDesignationClassCommissioned
USS PennsylvaniaBB38Pennsylvania1916
USS MississippiBB41New Mexico1917
USS TennesseeBB43Tennessee1920
USS MarylandBB46Colorado1921
USS CaliforniaBB44Tennessee1921
USS West VirginiaBB48Colorado1923

Table 1 also shows us that there were four different classes of US battleship at Surigao Strait. This seemed like a lot and made me curious about the evolution of US battleships relative to other combatants.  Fortunately, Wikipedia has a great table of battleship throw weights (i.e, the weight of a broadside from the main guns).  I used Power Query to download and tidy the table, and R to plot the data.

Figure 2 shows the number of battleships classes in service with major combatants. Notice how the US had the largest number of battleship classes. My personal opinion is that the US had so many classes in operation because

  • It had a lot to learn about battleships during and after WW1 and the commissioning of new classes shows how the US was working hard to catch up.
  • The US operated the old battleships for the entire war because new classes of battleships would not be available until the latter part of the WW2.

Figure 2: Number of Battleship Classes During WW2 By Major Combatants.

An important metric for a battleship is the weight of a broadside.  As I read about the Battle of Surigao Strait, it became clear the rate of the broadsides was also import. To understand the broadside weight per minute, I multiplied the rate of fire by the weight of an individual broadside to find the weight of fire per minute.

Figure 3 shows the top ten weights of fire for the different WW2 battleship classes. The Yamato and US 16-inch gun classes clearly dominate this metric.

Figure 3: Weight of Fire Per Minute.

The weight of a broadside depends on the weight of an individual shell. WW2 saw battleships with a wide range of shell calibers (i.e., diameter in inches). I became curious as to how the shell weight varied by caliber. I also fit a cubic curve (Figure 3) to the data to show that shell weight is roughly related to the cube of the caliber, which follows from the dimensional scaling laws.

Figure 3: Battleship Shell Weights Versus Caliber.

My spreadsheet and R markdown document are included here.

 
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5 Responses to Battleship Classes and Throw Weights

  1. NotACapitalist says:

    Liars, damned liars and statisticians. Authority, irrespective of claimant, is self-serving, biased and divisive.

    What my authority finds most interesting regarding such creations is the cultural/social/personal psychology that, throughout history [my academic field of study, BA], has required such creations of self-destruction.

    I also consider that the world population has more than tripled in the first 75 years of my existence (pre-Hiroshima, itself 4 yrs BP).
    I have grasped Darwin's OOS, wherein he envisions a new foundation for Psychology. [Accepting laughter] Psychology, individual and group, Man's Inherent Dichotomy. [Greater accepting laughter] I have gratitude for my capacity to laugh in the temporal dynamic, the moment of perturbation of stasis, the unstable equilibrium of the temporally and areally boundless spacetime which goes nowhere and does nothing.

    Live well, love fervently. Maths is a fun language set, while the life of the individual is temporally short and très dynamique.

     
  2. Malcolm Frame says:

    Some questions raised by your interesting article:
    When a battleship fires a broadside at sea, aiming for another vessel, are the guns set at different angles so that the shells straddle the target? What is the ratio of shells fired/hits?
    Is the rolling displacement of the battleship taken into account when targeting?
    Do the guns have to return to the horizontal after each salvo in order to load for the next one?
    Are the shells built like a rifle bullet, with the projectile and propellant all enclosed within a casing? How is the shell triggered?

    My home town was Portsmouth (in Hampshire, not New Hampshire) and from my bedroom window, I could see dozens of ships moored in the harbour after the end of the war, mostly awaiting a final trip to the scrapyard. Most notable was the battleship "Vanguard" whose keel was laid during the war but was not commissioned until after the war. In 1960 it was towed out for scrap, but as it passed through the very narrow entrance to the harbour, a tow line came loose and it swung around and went aground, nearly demolishing a pub crowded with sightseers. Apparently, it was the most violent action it was ever involved with. Here is a youtube film which includes that event (excuse the plummy accent of the narrator, but once you had to speak like that to get a job with the BBC):
    https://www.youtube.com/watch?v=Db6bgu0gs-g

     
    • mathscinotes says:





      When a battleship fires a broadside at sea, aiming for another vessel, are the guns set at different angles so that the shells straddle the target?

      There was enough variation between individual shots that multiple shots were usually fired at each range setting. Three guns were often fired at a time to ensure that an errant splash round could be detected (2 out of 3 at the same range). Here is a desciption of the ladder salvo used for ranging by the US Navy from the Navweaps website:

      Ladder Salvo - Also called "Ranging Salvo." When a ship is firing at a target and isn't quite sure of the range, what the gunnery officer will often do is elevate each gun or group of guns slightly differently. This makes each shell land a little farther along than the last one. By watching to see which shell hit or landed closest to the target, the range can be determined more accurately. During the early part of World War II, the procedure used by the new US battleships was to fire all nine guns as a ranging salvo, a typical pattern being one group (three guns from one turret) at 200 yards (180 m) up from the initial range estimate, one group at 200 yards (180 m) down and one group at 400 yards (370 m) down. There was also a timing difference between groups to avoid confusion between the shell splashes. Once a bracket had been obtained, thus indicating the correct range, the ship would then switch over to rapid fire, with the guns firing as they were ready.

      The US Navy procedures are discussed a bit on this web page.

      The Royal Navy used a procedure that involved firing a salvo with half the guns at a specific range (Friedman, Naval Firepower). The other half were then available for a correction. You want more than two guns in a salvo because a two gun salvo with an errant shot will create an ambiguity as to which splash reflected the correct range.

      The Germans also used a half-salvo approach.

      I should mention that all the countries first fired salvos to get the deflection correct, then they corrected for range.

      What is the ratio of shells fired/hits?

      This question gets the battleship crowd stirred up. Here is a table from a forum discussion that I think is reasonable. There are many other examples using battle data, but it has proven to be difficult to separate out the hits from multiple ships and I do not trust the results.

      Iowa
      vs Bismarck-Type
      Target Aspect  
      Range (yards) Broadside % End-On % B/EO
      10,000 32.7 22.3 1.47
      20,000 10.5 4.1 2.56
      30,000 2.7 1.4 1.93

      Is the rolling displacement of the battleship taken into account when targeting?


      Yes, but different ships used different approaches. The US Navy had a stable vertical reference and Remote Power Control in both elevation and azimuth for directing the guns. This allowed them to cancel out the roll electromechanically. If I recall correctly, the UK and Germans had stable verticals, but did not have RPC for elevation (example).

      Do the guns have to return to the horizontal after each salvo in order to load for the next one?

      Certainly for US battleships. Here is a quote from a forum discussion.

      03-01-2016, 12:09 AM
      On an Iowa Class, as well as the South Dakota Class, which used the earlier Mk6 16"/45 caliber guns, loading and reloading could only be accomplished with the breech at a 5 degree angle so that after firing, the barrel would almost invariably have to be moved to the correct position. Although the powder bags and shells were man handled into elevators (I pitty those poor swabbies), virtually the entire loading process was automated. Because of that, the the guns could not be loaded and fired any faster than the machinery was able to function and that served as a built in limit on rate of fire. With all nine of her 16 inch guns firing, and Iowa could have a shell in the air every four or five seconds.

      Are the shells built like a rifle bullet, with the projectile and propellant all enclosed within a casing?


      No. Large bore guns normally use bag charges (for example, USS North Carolina used as many as six 90 lb bags). The Germans did use a system with one cased charge and the rest bagged.

      How is the shell triggered?


      Do you mean fired from the gun? As far as firing goes, a primer charge is loaded. The primer is detonated, which initiates the powder train that detonates the bags.

       

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