Yamato and Musashi vs. Missouri and Iowa

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Byron Angel
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Re: Distance does matter

Postby Byron Angel » Sat Sep 28, 2013 3:11 am

George Gerolimatos wrote:Hello,
Perhaps I wasn't being clear enough. Yes, nominal RoF of American ships might be faster than Japanese. By "nominal" I mean that American ships can load and fire fast without concern for range or accuracy. However, gunnery dictates that for accurate shooting (meaning spotting fall of shot), there must be a time interval to allow the shells to fly to the target. Then, gunners will correct aim and fire again. At long ranges, shells take up to a minute to get there; hence, ships with even the fastest RoF must wait to allow the shells to fall around (or on) the target. Of course, at shorter ranges, flight time is much shorter. This is where RoF would matter. Once shots are spotted at closer ranges, American ships can pump out shells faster than their Japanese counterparts. At longer ranges, however, RoF is not very important.

I once thought that the raw numbers of RoF correlated with more shells in the air, as you do. However, I got a wargame and with some questions I learned that going by numbers by themselves don't account for the whole picture.



George ..... What you say is largely true of gunnery craft before the advent of radar controlled gunnery. Under radar FC, however, the rules changed somewhat. It was no longer necessary to wait to spot fall of shot in order to correct for range, as even early FC radars were very good at providing quite accurate range data in real time. USN BB daylight gunnery doctrine by 1944 was to employ rapid full salvoes with direct spotting under radar control at targets within the effective ranges of their FC radars. By 1944, this would have been the Mk8, with an effective ranging capability of 27-32,000 yards. At ranges beyond the FC ranging limit, aerial spotting and/or conventional bracketing and spotting techniques such as those you describe were to be used.

So, the nature of any engagement would depend a great deal upon visibility conditions.

FWIW.

B

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Re: Yamato and Musashi vs. Missouri and Iowa

Postby paul.mercer » Sun Sep 29, 2013 10:47 pm

Gentlemen,
We are considering two different sizes of ships here, a more interesting comparison would be two US 12x16" (Montana class?) against Yamoto and Musashi as they would be approximately the same weight and the 12 x16" per ship would be a better match against the two 9x 18" ships. Now that would be a battle!

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Re: Yamato and Musashi vs. Missouri and Iowa

Postby RF » Mon Sep 30, 2013 7:57 am

It certainly would.....
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Re: Yamato and Musashi vs. Missouri and Iowa

Postby Guest » Tue Apr 22, 2014 7:38 pm

Gentlemen,
We are considering two different sizes of ships here, a more interesting comparison would be two US 12x16" (Montana class?) against Yamoto and Musashi as they would be approximately the same weight and the 12 x16" per ship would be a better match against the two 9x 18" ships. Now that would be a battle!


Not really. What is overlooked is the Yamato was a ship built prior to WW2 - the Montana at the very end. The Montana is about 5 years newer, and in wartimes that a couple generations of ship "evolvement".

I think a few things are being overlooked here:

1) The US shell penetrated well, yes. But the Yamato had the advantage of armor about 25% thicker. Even if Japanese armor was indeed inferior as suggested, it's about 95% a effective as US class A armor, which gives it an effective belt of 15.2" vs the Iowa's 12.1". That's a major difference. The Iowa would take penetrating hits at about any range and would have to close to almost 1/2 of her guns range to penetrate.
2) Iowa's shells indeed penetrate better - but they do not do the damage the Yamato's shells do. Based on weight of shell and bursting charge, Iowa's shells do not to 80% of the damage the Yamato's would.
3) The Iowa has speed as an advantage - but speed does little to influence a battle once engaged. Alfred Thayer Mahan of the US Navy pointed this out which is why the US had 21-23 knot speed battleship built in the 20's. Speed confers certain advantages - but would not influence combat in a situation like this. Want to try to stay at far range with the Yamato? Only way to do that is to turn tail and run, then you are fighting Yamato's forward turrets with your rear turrets. And using the Scharnhorst as an example, once battle is joined it's very easy to lose a speed advantage due to taking enemy fire. Find a WW2 Battleship and or cruiser battle where speed played a role once combat was joined - if it helps in the engagement/disengagement is irrelevant.
4) US radar fire control is better, true. But in good weather and daytime, as stated at the start of this thread, it's not going to make much of a difference. And the Japanese had the best optics of the war. I'd also like to add that radar gets knocked out easily - look at the South Dakota at Guadacanal. Optics are more damage resistant, and you have more redundancies. One shell hit and the radar advantage can be lost, and in good weather/daylight operations it's not a great advantage to begin with.

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Re: Yamato and Musashi vs. Missouri and Iowa

Postby Steve Crandell » Fri Apr 25, 2014 1:09 am

Mr. Guest,

I don't think you understand the nature of long range gunnery very well. Since we have stipulated that there is very good visibility, combat will begin at about 40,000 yds or so. The probability of belt armor being hit at that range is pretty much nil. Both ships will be able to penetrate each other's deck armor. Then it comes down to who gets the most hits.

Imagine, if you will, looking through your rangefinder at a ship at that range. It's likely that it will be kind of indistinct and wavy in the haze, and quite small even in a high powered scope. Very hard to get a good optical range. You get your best idea of what it is and begin firing. Your shell splashes are only seen for a short period because you can only see the tops of them near the hazy upper levels of the target's superstructure. It's nearly impossible to tell whether they are hitting in front or behind the target, especially if they aren't perfectly in line with it.

Now look at a Mark 8 mod 1 gunnery radar scope. The target is in the middle of a circular display, and you have a relatively precise range. When your salvo lands, you see little spots where each shell lands in relation to the target location. It's very easy to determine salvo MPI.

Now, who do you think has the advantage in this situation? The guy with the radar, or the guy with the 15m optical rangefinder?

You mentioned the possibility of radar being hit and put out of action. That can happen to Yamato's main fire control position as well.

Radar was subject to shock damage from the firing of the main battery, but there are two or three main battery radars on a USN battleship and I wouldn't want to stake my survival on them all being out of action when you needed them to be. There were more battles where it remained in action than there were when it didn't.

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don't forget the extra-long fuze delay

Postby alecsandros » Fri Apr 25, 2014 11:45 am

... of the Japanese 460mm APC shells. 0.4seconds delay is huge when the shell strikes at 450m/s. The shells, if it would still be in functioning condition after passing through 200mm+ of successive armor layers, would probably explode somewhere beneath the ship, and possibly very far away from it, depending on exact trajectory of the impact.

On the other hand, the K.E. of the impact of the 1.46 tons shell was enormous, and it would cause heavy shock damage by impact force alone.

Yamato was a giant beast, and it would take massive amount of hits to take it down.

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Re: Yamato and Musashi vs. Missouri and Iowa

Postby Byron Angel » Fri Apr 25, 2014 8:56 pm

I think the quoted fuze delay time is off by a decimal place. Should read as .040 seconds, which @450 m/s striking velocity = about 18 meters (60 ft).

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Re: Yamato and Musashi vs. Missouri and Iowa

Postby Steve Crandell » Fri Apr 25, 2014 11:16 pm

Byron Angel wrote:I think the quoted fuze delay time is off by a decimal place. Should read as .040 seconds, which @450 m/s striking velocity = about 18 meters (60 ft).

B


I can't vouch for the exact number, but the IJN fuse delay was much longer than anyone else's because their shells were designed to follow a stable underwater trajectory to obtain more than the normal underwater hits. That required a very long fuse delay.

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Re: Yamato and Musashi vs. Missouri and Iowa

Postby Mostlyharmless » Fri Apr 25, 2014 11:16 pm

I think that it really was a huge 0.4 seconds for the Japanese Type 91 shells (the Type 13 mark 5 fuze is described on page 17 of the USN Technical Mission to Japan Report O-17 http://www.fischer-tropsch.org/primary_ ... 200-17.pdf). The report seems to suggest that a 0.1 second fuse was being considered. Presumably, the IJN wanted the enemy to have time to notice a 46 cm shell arriving in or under the magazine before it went off :D

ps. “Kaigun: Strategy, Tactics, and Technology in the Imperial Japanese Navy 1887-1941” by David C. Evans & Mark R. Peattie, page 265 is also interesting.

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Re: Yamato and Musashi vs. Missouri and Iowa

Postby Byron Angel » Sun Apr 27, 2014 11:53 am

Mostlyharmless wrote:I think that it really was a huge 0.4 seconds for the Japanese Type 91 shells (the Type 13 mark 5 fuze is described on page 17 of the USN Technical Mission to Japan Report O-17 http://www.fischer-tropsch.org/primary_ ... 200-17.pdf). The report seems to suggest that a 0.1 second fuse was being considered. Presumably, the IJN wanted the enemy to have time to notice a 46 cm shell arriving in or under the magazine before it went off :D

ps. “Kaigun: Strategy, Tactics, and Technology in the Imperial Japanese Navy 1887-1941” by David C. Evans & Mark R. Peattie, page 265 is also interesting.



..... I checked my reference sources and you are indeed correct - the fuze time delay on Japanese AP projectiles was approx 0.40 seconds. Compared to the delay fuzes of other nations, which were in the range of 0.030 - 0.035 seconds, this was longer by a factor of more than 10x. High marks must be given to Japan for technical ingenuity and persistence. It cannot have been a trivial task to develop such a unique shell + fuze combination. Insufficient action experience exists to reach any fair verdict as to its true operational effectiveness. But, had it worked as intended in a long-range capital ship engagement, it might have proved a nasty and possibly decisive surprise to the USN.

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Re: Yamato and Musashi vs. Missouri and Iowa

Postby Steve Crandell » Sun Apr 27, 2014 12:45 pm

Byron Angel wrote:
Mostlyharmless wrote:I think that it really was a huge 0.4 seconds for the Japanese Type 91 shells (the Type 13 mark 5 fuze is described on page 17 of the USN Technical Mission to Japan Report O-17 http://www.fischer-tropsch.org/primary_ ... 200-17.pdf). The report seems to suggest that a 0.1 second fuse was being considered. Presumably, the IJN wanted the enemy to have time to notice a 46 cm shell arriving in or under the magazine before it went off :D

ps. “Kaigun: Strategy, Tactics, and Technology in the Imperial Japanese Navy 1887-1941” by David C. Evans & Mark R. Peattie, page 265 is also interesting.



..... I checked my reference sources and you are indeed correct - the fuze time delay on Japanese AP projectiles was approx 0.40 seconds. Compared to the delay fuzes of other nations, which were in the range of 0.030 - 0.035 seconds, this was longer by a factor of more than 10x. High marks must be given to Japan for technical ingenuity and persistence. It cannot have been a trivial task to develop such a unique shell + fuze combination. Insufficient action experience exists to reach any fair verdict as to its true operational effectiveness. But, had it worked as intended in a long-range capital ship engagement, it might have proved a nasty and possibly decisive surprise to the USN.

B


I believe the British delay was more like .025 seconds.

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Re: Yamato and Musashi vs. Missouri and Iowa

Postby tommy303 » Mon Apr 28, 2014 6:01 pm

British base fuzes for large shells generally had a set screw which allowed setting the fuze to non-delay or normal delay prior to loading; so too did German fuzes after 1942 with settings for 0, .015, and .035 (If i recall correctly). In any event, it might be worth noting that pyrotechnic delay figures are based on an average and could run shorter or longer, with longer being the usual case.

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Re: Yamato and Musashi vs. Missouri and Iowa

Postby tommy303 » Tue Apr 29, 2014 5:49 pm

It is worthwhile noting that in inertial action base fuzes, there is a finite delay between impact and fuze initiation, so that even a base fuze set to 0 will still take about .003 second to initiate, assuming it has met enough resistance to decelerate enough to do so.

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Re: Yamato and Musashi vs. Missouri and Iowa

Postby Mostlyharmless » Fri May 02, 2014 9:55 pm

I am not sure if this is the best place to ask but does anyone know what the thickness of Yamato's main armour deck was?

There is a drawing by Janusz Skulski which suggests 200 mm on 10 mm http://www.flickriver.com/photos/274176 ... 181515847/, the USN technical report http://www.fischer-tropsch.org/primary_ ... S-01-3.pdf suggests that 20.3 cm was reduced to 190 mm and Dickson's IJN Yamato article from Warship International (1975) has 200 mm in a drawing on page 315 and 190 mm in a table on page 297.

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Re: Yamato and Musashi vs. Missouri and Iowa

Postby alecsandros » Sat May 03, 2014 7:32 am

Mostlyharmless wrote:I am not sure if this is the best place to ask but does anyone know what the thickness of Yamato's main armour deck was?

There is a drawing by Janusz Skulski which suggests 200 mm on 10 mm http://www.flickriver.com/photos/274176 ... 181515847/, the USN technical report http://www.fischer-tropsch.org/primary_ ... S-01-3.pdf suggests that 20.3 cm was reduced to 190 mm and Dickson's IJN Yamato article from Warship International (1975) has 200 mm in a drawing on page 315 and 190 mm in a table on page 297.

... it's unlikely it had a perfectly equal deck thickness throughout... the casting would produce slabs with some small variations, which may have been partialy superimposed on the edges in order to diminish the resistance loss.

Most likely the designed thickenss was 200mm inboard and 230mm on the (slightly sloped) outboard region of the armored deck...

But not enough it seems to keep out dive bomber 454kg AP bombs, as shown by Musashi's terrific damage suffered in her final battle...


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