Yamato verses Iowa

Great thread. ..MrT- never thought it would take a minute and a half for shells to land. It almost defeats the 18 inch guns as the target has so much time to change course. Would individual turrets fire different trajectories in order to counter any forseeable reaction from the target?
Wonder how the IJN 46cm vs the GER 38cm guns would fare in a battle. If the 38 fires flatter, wouldn't it be the more desireable gun for a shoot out?

 

I think the angle of the trajectory is basically a function of shell speed and distance. At extreme ranges all shells will be traveling at terminal velocity. This will be a little higher for a more aerodynamic shell with a smaller surface area and a greater mass, but I'd guess the differences in TV for a German 38, a Japanese 46, and indeed any other battleship main gun would be rather small. (Not so small that they don't play into range, mind you, but small enough that we don't need to worry about them right now.) I'm not a Nathan Okun, but I suspect the muzzle velocity will be the primary indicator here. The shell will only slow down after it leaves the muzzle of the gun, as initial speed is WELL beyond terminal velocity (which is subsonic). This is why penetration decreases with range. The shell loses energy as friction slows it down. In effect, the more air it must penetrate the less steel it will penetrate. The basic math isn't so different, really. Steel is simply more dense and more cohesive (stronger in both compression and tension), thus producing much more friction against the shell (and deforming it to reduce its steel-o-dynamicness. Note aeordynamic shapes and armor penetrating shapes aren't so different. Pointy is better. The kinetic energy of the shell will concentrate at the point, thus imparting more energy on a small surface for that nice nail-in-the-board effect.) But let's prove this. Let's see what NavWeaps and The Real Nathan Okun have to say . . .

Per NavWeaps:

Yamato has the heavier shell (1460 kg v. 800 kg) and Bismark the higher muzzle velocity (820 mps v. 780 mps), but the energy comes down in favor of Yamato. Angle of fall at low and mid ranges is slightly in favor of Bismark, but not by much. For 5000 m Yamato has a fall angle of 3.3 degrees and Bismark 2.4. At 10,000 the difference is slightly greater: 7.2 v. 5.8. 15000: 11.5 and 10.4. By 20000 meters the difference is negligible: 16.5 for Yamato and 16.4 for Bismark. By 25000 meters the trend is reversed: 23 degrees for Yamato and 23.8 for Bismark, and thus does it remain. (Presumably Bismark's light round is bleeding energy faster, since it has much more surface area per mass or volume.)

So the two perform a little differently, but the trajectories are startlingly similar. Yamato has a much higher range, but her turrets also elevate fifteen degrees further. (I'd call that an oopsie on Bismark's part.) Yamato also wins the penetration contest at all ranges. (Recall the higher energy.) Coming out of the muzzle Bismark has a theoretical penetration of a bit more than 29" and Yamato right at 34". At 30000 meters Bismark will chew through 4.7" of your Krupp decking and Yamato a bit more than 9"; a not an insignificant difference.

Now, the German guns theoretically fire faster (3 rounds a minute to the Japanese 2) but with half the broadside weight, that still doesn't make up the deficiency. And at typical engagement ranges you won't be firing at quickest possible anyway, as you'll be waiting on fall of shot. I'll take Yamato in the fight, thanks. Not that this is relevant to the Iowa v. Yamato thread. That's a much closer fight and depends a lot on conditions.

Note all data about ballistics from:

http://www.navweaps.com/Weapons/WNGER_15-52_skc34.htm
and
http://www.navweaps.com/Weapons/WNJAP_18-45_t94.htm

General observations about weight of broadside and rate of fire from:

http://www.combinedfleet.com/b_guns.htm

 

A salient point about Yamato's armor piercing shells is in order here.

Yamato hit White Plains from a distance of 19.65 miles with her third salvo on the morning of 10/25/1944, the longest shot in naval history.

Robert Lundgren makes a good point about this hit in a recent email to me, quoted below (Italics mine):

"However, any time a ship takes structural damage she has been hit. It is the only way the ship can take damage. Direct hit the use of the word direct is an adjective defining the "type" of hit. It does not change the fact White Planes "was" hit. Her crushed in keel and the photos are absolute proof. It is a fact. Yamato's shells are specifically designed to attack the underwater hull of a target either by striking the side or detonating underneath by a designed and stable underwater trajectory due to a flat nose and a long delay fuse. It worked perfectly as designed. These shells gave the Japanese a specific advantage at long range by widening the danger space. It worked! This was engineered and not a fluke or dumb luck."

 

That is very interesting Mr Al. Have you any links? Wondering about the design and if that tech is still applied today. It's all missiles now.

 

With all due respect(an it is a lot) to Mr. Lundgren, only the first part of that statement is correct.

The Japanese "diving shells" or "suichudan" were designed to travel a more or less predictable ballistic path underwater to impact a ship's hull, which was an improvement over the usual underwater tumbling of a normal shell. Regretfully, the rest of the sentence "not a fluke or dumb luck." is utter bunk. The "diving shells" performed as advertised only a handful of times during World War II; the USS Boise at the Battle off Cape Esperance, and possibly the USS Salt Lake City at the Battle of the Komandorski Islands. now, given that the "suichudan" performed as intended a grand total of 3 times...How on earth can he legitimately claim that the "near miss" against the USS White Plains was anything but a fluke or dumb luck? I'm sorry, but, in my opinion, 3, to use his term, "hits" during the entire Pacific War is chalked up to a "fluke" or "dumb luck".

 

Hey. They made some neat stuff.
Never heard of the "suichidan" before. Shells tumbling in water. Gonna look it up.Thanks for that.

Edited. Just because.

 

Here is a link to wikipedia page on Yamato's big guns. Photos of each type of shell are at the bottom of the page. Be sure to click on the armor piercing shell diagram and enlarge it, for there is some fascinating info there, including the fact that the pointy cone was designed to be jettisoned upon the shell's impact with water...

http://en.wikipedia.org/wiki/40_cm/45_Type_94_naval_gun

 

Forgive my faulty memory, I misspelled the name. it should be "suichudan."

Here are the relevant pages from "Kaigun: Strategy, Tactics, and Technology in the Imperial Japanese Navy 1887-1945"
http://books.google.com/books?id=iSDOAwAAQBAJ&pg=PA263&lpg=PA263&dq=japanese+ap+shell,+underwater+trajectory&source=bl&ots=EBbQoSLXyD&sig=9vPj1vxmlHEKNItCv8bpr8OhuEw&hl=en&sa=X&ei=GK-4U4vxCY-0yASdz4HQCg&ved=0CCwQ6AEwAQ#v=onepage&q=japanese%20ap%20shell%2C%20underwater%20trajectory&f=false

 

Well in all fairness if it was a "fluke" or "dumb luck" it still took an accurate gun & FC,as well as well trained crew, to get straddles to enable "dumb luck" or "fluke" to achieve what it did.

 

omg. Just wet my pantaloons. That was an awesome bit of info MrT. ..Never thought a shell could travel up to 80 meters underwater. Even 40 seems crazy... Mythbusters showed how much bullets in water decrease velocity and barely travel-new respect for heavy weapons...And the torpedo bits-great stuff. Going to save that page for slow digestion.

 

20.000 odd tonns more of armour and weapons are likely to make a difference, to make things worse for Iowa a lot of her tonnage was invested to get very high speed for a battleship and despite the better technology of US machinery that means less armour. So barring some convincing element to reverse the balance, and if we believe there is conclusive evidence Yamato's defective gunnery is a myth there is none so far, my money is on Yamato. Of course in real life anything can happen when the big guns start firing. BTW what about USS Missouri's suspected defective armour ?

http://www.navweaps.com/index_tech/tech-037.htm

 

Hey. Another good bit there. Article did not state whether the crack would have lessened the integrity of the turret.

 

I'm betting on Iowa all the way. Just wait for a cloudy (maybe rainy) moonless night and pound her into oblivion.

 

One advantage to the Iowas(and all US fast battleships in general) was their ability maintain a bead on their target while conducting radical maneuvers, something that no other nations battlewagons were capable of doing I believe, and this, combined with the Iowas superior speed, fire control, and comparable gunpower thanks to the mark 8 "super heavy" round, does give her a strong chance at winning.

 

I thought I remember reading several times that the visibility was highly variable that day with squalls moving through the area. Thus one could have visibilty of 12 miles at one point and only a mile or two a few minutes later and almost unlimited a few minutes after that. Picking the visibility at one point and saying it disproves anything is pretty questionable. I've also read that at least some of the IJN battleships were getting their ranges from radar during at least part of this battle.

As far as the heights go it should be reciprical. If A can see B then B can see A. Looking at:
http://www.ringbell.co.uk/info/hdist.htm
If their spotting tops are at 100 ft and 50 ft then they should be able to see each other at ~20 miles. The horizon for the 100 ft spotting top would be ~12 miles. Yamato did have her spotting plane up for at least the first salvo though.
The site above doesn't specify whether they are talking nautical or statute miles but this one indicates they are likely nautical miles:
http://www.boatsafe.com/tools/horizon.htm

 

The navweapons pages for these guns are very useful if you want to compare them. See:
http://www.navweaps.com/Weapons/WNGER_15-52_skc34.htm
and
http://www.navweaps.com/Weapons/WNJAP_18-45_t94.htm
Note that at closer ranges hits would often be against vertical armor while at longer ranges against horizontal armor. Also of some interest are the following:
http://www.navweaps.com/index_nathan/index_nathan.htm
http://www.navweaps.com/index_nathan/Penetration_index.htm
http://www.navweaps.com/index_nathan/Penetration_Japan.htm
http://www.navweaps.com/index_nathan/Penetration_Germany.htm

Some more links to them PLS excuse any duplicates:
http://www.navweaps.com/index_nathan/Japanese_Type_91_Projectile_Data.pdf
http://www.navweaps.com/index_tech/tech-041.htm
Somewhere I've read a really good article on the development of those shells and from what I recall they didn't quite live up to their promise often diving deeper than planned. I can't seem to find it right now though. In odrder to take advantage of the diving effect they did have to use longer fuses which allowed for the possiblity of through and through penetrations before the burster went off.

 

One has to be a bit careful there. From what I recall the faceplates of Yamato's turrets were theoretically impervious to any battleships guns. If one was close enough to penetrate the angle was such that they still wouldn't. However that does leave the sides, back, and top vulnerable to penetration. Furthermore if one got multile hits or close enough to the gun ports for edge effect to come into play then a penetration might be possible.

 

Except for the fact that the Iowa used armor quality steel througout her structure as was US practice. so she may actually have had more armor than the Yamato. The torpedo hit the Yamato took early on also revealed some problems with her armor from what I recall. Not sure they would come into play in a battleship duel though. The higher speed combined with the US radar fire control would also allow Iowa to "salvo chase" and still maintain a very good fire control solution which Yamato couldn't.

Yamato's optical fire control was probably unsurpassed. However once you get over 30,000 yards radar dominates and the US radar fire control was significantly supperior to that of the IJN ship (when she got it). This give the Iowa an advantage in a long range duel and her speed gives her the ability to keep it at long range. Whether or not the USN commander would elect to do so is an open question that would depend a lot on what he believed the Yamato was capable of (in particular did he think she was a balanced desigh with 16" guns or a balanced design with 18" guns) and the tactical and strategic situation. I'd also give the edge to US damage control at least after the first few shells land.

 

The Iowa can also fire faster, so even if she closes the distance, the Yamato has to try to hit a faster, more manouverable ship that shoots faster with superior targeting. Yamato gets pummeled.

 

At longer ranges the time of flight and necessity to correct based on observation of the shell splashes pretty much means there is little difference in the rate of fire. At closer ranges it may make a difference but at closer ranges Yamato's additional armor starts having a greater impact as well. At least until they close to knife fighting range. My personal opinion for instance is that if you replace Kiroshima with Yamato the latter doesn't survive the pummeling Washington delivered.