Best U.S. cruisers at the river Platte

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Best U.S. cruisers at the river Platte

Post by guesser » Wed Jul 25, 2012 2:44 am

What if rather than Exeter, Achillies and Ajax the US had exchanged the use of UK bases for 2 Brooklands and a late model New Orleans or even Wichita?. A few calculations show that the weight of fire per minute was very equal between the Germans and English, but the 3 U.S. ships had the equal all four from both groups combined, not to mention more armor and a slight edge in speed; would the German ship have been able to fend off these ships long enough to make shelter or would she have been overwhelmed outright?

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Re: Best U.S. cruisers at the river Platte

Post by alecsandros » Wed Jul 25, 2012 10:13 am

If the Graf Spee would be commanded as poorly as she was, against the US cruisers, it probably would have been sunk.

If it would have been better commanded, and kept the range at ~ 20km, and concentrating all fire on a single ship at every time, and not trying to make torpedo runs, than it would have a chance.

Cheers,
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Re: Best U.S. cruisers at the river Platte

Post by WestPhilly » Wed Jul 25, 2012 2:48 pm

The slower Graf Spee could not have controlled the range. If Spee had concentrated on, presumably, the heavy cruiser, the two Brooklyns would have closed on Spee to unleash an avalanche of 6" shells. The four 6" secondary mounts on Spee would have been no deterrent against the Brooklyns, thereby necessitating the Spee to train one of the 11" turrets on the Brooklyns.

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Re: Best U.S. cruisers at the river Platte

Post by alecsandros » Wed Jul 25, 2012 2:56 pm

I know,
But 4 kts advantage is not that much, and G Spee would have a lot of time to strike before the 6" guns could play a meaningfull part.

And in the historical engagement, Graf Spee received a large number of 6" shell hits, without suffering important damage.

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Re: Best U.S. cruisers at the river Platte

Post by Keith Enge » Wed Jul 25, 2012 5:30 pm

The US ships would wipe up. There should be no surprise in this. After all, each of the US ships had almost the tonnage of AGS and there were three of them. The extra range advantage of the AGS had little value because the ship couldn't see as far as her guns could shoot. The Brooklyns would have been much more dangerous to AGS than Ajax and Achilles. They had a higher rate of fire and almost twice as many guns besides. They also had much better armor than the British Commonwealth ships and this results in a 13,000 yard immune zone against the German 5.9" secondaries. Wichita's immune zone against those guns was even larger (she had even better deck armor than the Brooklyns). Therefore, only the 11.1" guns were of much use and there were too few of them for that number of targets. The only things that the US ships lacked were torpedoes but they would be unlikely to be useful at the likely ranges and courses.

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Re: Best U.S. cruisers at the river Platte

Post by alecsandros » Wed Jul 25, 2012 5:39 pm

No.
Graf Spee could effectively engage the enemy at ~ 24km or so [at River Plate it obtained straddles at ~ 18km on Exeter, IIRC, and shortly after it obtained direct hits], while the 6" guns were only usefull below 12km in terms of precision [the 155mm guns were ideal for short range engagements, were the weight of fire/minute could realy deter an enemy. At medium to long range, the dispersion patter was simply to large to put real hope in obtaining hits]. At 4kts speed differential, it woudl take more tahn 2 hours for the Brooklyns to close the range [from 24 to 12 km], plenty of time to be plastered with 11" shells.

The US cruisers had 0 immunity zone against the 11" guns, while GS had significant protection against the enemy's weaponry, as demonstrated in the historical battle.

In the real engagement, the 150mm secondaries proved useless, with only the 6x 11" guns causing damage to the British cruisers.
And, in the real engagement, GS was poorly commanded, but even so, it still crippled Exeter and put Ajax's fw turrets out of action.

P.S.: IF the Graf Spee would be commanded the same as in the historical scenario, I would expect it to be sunk fast. Her only hope would be to keep the range opened as long as possible, and deliver critical hits before the US cruisers would enter killing range.

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Re: Best U.S. cruisers at the river Platte

Post by Keith Enge » Wed Jul 25, 2012 7:48 pm

alecsandros -
There are two things wrong with your argument. First, to best prevent the range from closing, AGS would have to put her stern to her pursuers. This would limit her gunfire to the aft turret. With only three guns and a not particular fast rate of fire, AGS would have difficulty obtaining hits, especially having only three shells with which to judge straddles. AGS would also likely run out of shells in that aft turret (she only had 315 there and probably had used some earlier in her voyage). After all, to use the range obtained by the previous salvo before the data becomes stale, the next salvo must be fired as quickly as possible. At this maximum rate of fire, AGS would empty that aft magazine in about 30 minutes. Second, you understate the speed advantage of the US ships; they have a 7-8 knot advantage, not the 4 knots that you mentioned. Even limiting it to a 6 knot advantage, the Brooklyns could close 1000 yards every 5 minutes. They could therefore close that 12,000 yards in an hour, not more than two hours (using the full 8 knot advantage, it would take only 45 minutes). In addition, I question if they would have to close that 12,000 yards from 24,000 yards to obtain a significant number of hits. Historically, they were shooting at smallish Japanese destroyers at those 12,000 yard ranges; AGS is a much larger target so the resulting effective range would be larger, probably closer to 18,000 yards. They could close from 24,000 to 18,000 in a half hour, by which time AGS was likely out of shells in the aft turret. Of course, this closure rate assumes that they hadn't been slowed by hits during the closure but, as stated above, AGS would have trouble getting hits with only three guns and AGS might be slowed by hits herself anyway. After all, in five minutes, AGS could put about 100 shells in the air from that aft turret. Meanwhile, the four forward turrets on the two Brooklyns (they each had three triple turrets forward but one of them only could bear to the broadside) could put 540 shells in the air. I like my chances of getting hits with 540 shells compared with 100. By the way, AGS's armor wasn't particularly thick and those 6" shells (a heavy 130 lbs) could penetrate AGS except for a very small immune zone of about 1500 yds wide at around 17,000 yards.

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Re: Best U.S. cruisers at the river Platte

Post by alecsandros » Wed Jul 25, 2012 8:31 pm

Keith,
With all due respect, you don't know what you're talking about.

1. Graf Spee achieved 29kts max speed, and the Brooklins had 32.5kts max. Thus, 3.5KTS difference.

2. Graf Spee had a scarp behind the main belt... The immunity zone of the vitals against 6"/L47 was anywhere over 8km. At River Plate, GS probably took 15x6" hits, with no important damage to be recorded.

3. You don't seem to understand the positionign of the ships.
Graf Spee would move on a certain course, pursued by THREE cruisers. How would those cruisers be alligned ? I doubt very much that they wouyld be forming a single line, dead astern the Graf Spee. They would most likely advance in echelon formation, thus 2 of them being exposed to fire from 6 guns.

4. Also, you don't seem to understand what happened at River Plate: Exeter took 3 debilitating hits in the first 8 minutes of the battle, from ranges between 14 to 18 km. The problems arose later, when the GS started shifting fire from main and secondary guns, and later spliting the main battery. This caused great shooting problems, and later hits only came slowly.

5. Finaly, the US cruisers were significantly larger targets than either British ship, and given the amount of straddles G Spee obtained in the historical encounter, a larger number of hits is probable.

---

6. As for the ballistics and hit ratio of 11" and 6" shells, and for perforation/penetration limits, you should realy take a look at some charts....

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Re: Best U.S. cruisers at the river Platte

Post by Keith Enge » Wed Jul 25, 2012 9:44 pm

alecsandros -
1) AGS did obtain 28 knots but suffered extreme vibration. Her maximum usable speed for any length of time was 26 knots. The problem was synching multiple diesel motors to shafts. This is extremely difficult and small differences between two motors on the same shaft led to scary situations if those motors were forced too far. On the other hand, the Brooklyns were capable of 34 knots, it is the later Cleveland class that only were rated at 32.5 knots.

2) That scarf would have been useful at short ranges but, given the good visibility during this action, the hits would be at ranges where the shells would be arcing over that scarf and AGS's deck was only equivalent to 1.8" (her belt was only equivalent to 3.1"), the panzerschiffs didn't really have much tonnage available for thick armor. Conversely, the Brooklyn's belt was 6" with a 2" deck (not that either would help against 11.1" shells but they did cause problems for the 5.9" secondaries).

3) The fore turret on AGS had an 80 degrees (plus and minus 40 degrees) blind arc aft. Therefore, the three US ships wouldn't have to be in a line astern. In fact, at 20,000 yards, the three ships could be in a line abreast each separated from the others by almost 13,000 yards and still remain in the AGS's blind arc (20000*sin(40)).

4) Yes, Exeter took those three hits at about those ranges. However, it was only three hits and, if AGS let the US ships get that close, her goose was cooked. All three ships would be hitting her often. Against the British light cruisers with their 100 lb shells, most of the 6" hits on AGS was while she was in her immune zone against those guns so the hits did little damage. On the other hand, the immune zone against the US 130 lb shell was about three times smaller. Meanwhile, the US light cruisers' immune zone against the German 5.9" shells was two to three times larger than the British Commonwealth light cruisers' immune zone. The "two to three" results from the fact that Ajax and Achilles weren't uniformly armored, the magazines had thicker armor than the propulsion spaces so it had two different immune zones. The result of all of this is that the AGS could basically ignore the gunfire of the British CLs but wouldn't be able to ignore the US CL's gunfire. Also, while the German secondaries could deter the British CLs, they wouldn't do the same against the US CLs because of the thicker armor.

All of this reinforces my original point that this battle would be a walkover as it should be. With newer ships with almost three times the tonnage, it would have reflected very badly on US ship design if it wasn't so. The German ships paid a heavy price for 11.1" guns on a cruiser hull (5.9" secondaries were also unusually heavy for a cruiser hull). Little weight was available for thick armor, high speed, or very many shells for those large guns.

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Re: Best U.S. cruisers at the river Platte

Post by alecsandros » Wed Jul 25, 2012 10:34 pm

No,
Extreme vibration appearead at 29.5kts, the maximum speed obtained in trials. 28kts was sustainable.
http://en.wikipedia.org/wiki/German_cru ... _Graf_Spee

The Brooklyns were rated at 32kts, and may have exceeded that, depending on load, water temperature, bottom fouling, etc.
But they were expected to do 32kts, just like the Wichita class.
http://en.wikipedia.org/wiki/Brooklyn_class_cruiser

The perforation of 6" shells was low, even using the 130lbs shell (about 100mm at 10km with no lateral obliquity). Impact obliquity and impact velocity were to unfavorable to obtain deck penetrations.
The max range was 23km , and effective aroudn 12km or so. The reason lies in the dispersion pattern on those guns.

GS secondaries would probably be useless, just like they were at River Plate.

The primaries though could swing the battle in her favor, provided they would score a few early hits on either US cruiser (3-4 hits would inflict massive damage)

Finaly, at any likely range, the Graf Spee could easily make some small course correction, fire a broadside, and return to course while the main guns are reloading. This is exacly what Schrnhorst did at North Cape against DoY, obtaining a good number of sraddles (and cutting off the radars).

Again, no US cruiser had ANY immunity against 11" shells, and taking into account the way GS fired at River Plate at long range, against fast moving targets, I woudl expect severe damage to be delivered early into the battle, especialy as the US cruisers were considerably larger than their BRitish counterparts.

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Re: Best U.S. cruisers at the river Platte

Post by Keith Enge » Wed Jul 25, 2012 11:59 pm

alecsandros -
Several hard copy sources which I consider more reliable than Wikipedia rate the panzerschiffe at 28 knots with the caveat that this wasn't obtained in service, hence the 26 knots that I mentioned. Similar, the Brooklyns were credited with 33.6 knots.

When you are putting as many shells in the air as the Brooklyns, dispersion is basically moot. To free her fore turret, AGS would have to turn 40 degrees, this is not a small course correction. In fact, it would reduce the forward component of her speed from 26 knots to less than 20 knots and so allow the range to close even quicker. Furthermore, the Brooklyns, if desired, could make a smaller course correction and free their aft turrets and the wooded fore turret. This would allow the pair to put 1350 combined shells into the air in five minutes while the AGS was only firing about 100 from her two turrets. By the way, I was incorrect earlier when I said that the AGS could fire 100 from her aft turret in five minutes, actually it is only about 50 (her best rate of fire per barrel was 3.4 shells per minute) (which is why the turret would run out of shells in only about 30 minutes of maximum fire).

I agree that the US CLs were larger targets than the British CLs. However, besides being larger, they were also much tougher and so much more able to withstand hits even ignoring their armor advantage. Therefore, those notional three or four hits would be unlikely to inflict "massive damage" especially if split between two ships. Actually, they would be split between three ships since our discussion has been ignoring Wichita. My database actually rates Wichita alone slightly more powerful than AGS. As an aside, a Brooklyn is about 50% more powerful than a Leander class ship.

guesser

Re: Best U.S. cruisers at the river Platte

Post by guesser » Thu Jul 26, 2012 5:41 am

I think if the British ships managed to get close enough to obtain hits the U.S. ships would have done the same as they were slightly faster, and they would have done so at about twice the rate with the 30 guns on the Brooklands as opposed to the 16 combined guns of Ajax and Achillies; and those hits would have been heavier. The New Orleans or Wichita would not only have three additional guns but those guns threw a shell that was considerably heavier, the combined weight of fire from the U.S. ships was over 40,000 lbs per minute, or twice the main and secondary fire combined from GS. The turrets dissabled on Exceter had a maximum 1" of armor as opposed to 6-8" on the U.S. ships, so they would have fared far better than the british ships in absorbing punnishment. The hail of 6" shells would have made accurate fire difficult for GS due to damage to fire control, secondary battery and the bridge, and the 335 lb 8" shells would have done more damage than the 268 lb shells from Exeter that made GS seek shelter. The histories I've read say that GS was limited to 26 kts due to delayed hull cleaning so the advantage at the time was about 7 kts. I feel GS would have been finished before making port.
alecsandros wrote:Keith,
With all due respect, you don't know what you're talking about.

1. Graf Spee achieved 29kts max speed, and the Brooklins had 32.5kts max. Thus, 3.5KTS difference.

2. Graf Spee had a scarp behind the main belt... The immunity zone of the vitals against 6"/L47 was anywhere over 8km. At River Plate, GS probably took 15x6" hits, with no important damage to be recorded.

3. You don't seem to understand the positionign of the ships.
Graf Spee would move on a certain course, pursued by THREE cruisers. How would those cruisers be alligned ? I doubt very much that they wouyld be forming a single line, dead astern the Graf Spee. They would most likely advance in echelon formation, thus 2 of them being exposed to fire from 6 guns.

4. Also, you don't seem to understand what happened at River Plate: Exeter took 3 debilitating hits in the first 8 minutes of the battle, from ranges between 14 to 18 km. The problems arose later, when the GS started shifting fire from main and secondary guns, and later spliting the main battery. This caused great shooting problems, and later hits only came slowly.

5. Finaly, the US cruisers were significantly larger targets than either British ship, and given the amount of straddles G Spee obtained in the historical encounter, a larger number of hits is probable.

---

6. As for the ballistics and hit ratio of 11" and 6" shells, and for perforation/penetration limits, you should realy take a look at some charts....

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Re: Best U.S. cruisers at the river Platte

Post by alecsandros » Thu Jul 26, 2012 8:01 am

I guess you put far to much emphasis on the theoretical side of the engagement. In reality, a high speed Broolklyn was not such a good gun platform, and it would take some time before obtaining any hits.
Graf Spee on the other hand was a much stable platform.

The ballistics and perforation limits of the guns also are not the ones that you imagine. The 6" 130lbs shell could only perforate 100mm of vertical steel at 10km, while the 11" shells could perforate pretty much anything, including main magazines and machinery spaces.

In theory, lots of shells put into the air = a high number of hits.
In reality, if you would check the statuses of Pacific cruiser combats, you will discover than for ranges of 16-25 km, gigantic amounts of ammo were expended on either side, for 0 or only a few hits.

This is caused by several factors, amongst which gun ballistics - as the shell is fired closer to the maximum gun range, it will have a steeper angle of fall, and thus danger space for the enemy would be smaller.
The rule of thumb is that efective shootings can best be done at 50% of maximum gun range.

As for the speed, again, the sources that I have indicate 28kts was the speed GS obtained at River Plate. Higher speeds were possible, as shown on trials, but with virbration problems.

Alex

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Re: Best U.S. cruisers at the river Platte

Post by RF » Thu Jul 26, 2012 8:32 am

alecsandros wrote: P.S.: IF the Graf Spee would be commanded the same as in the historical scenario, I would expect it to be sunk fast. Her only hope would be to keep the range opened as long as possible, and deliver critical hits before the US cruisers would enter killing range.
I am inclined to agree with this verdict.
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Re: Best U.S. cruisers at the river Platte

Post by RF » Thu Jul 26, 2012 8:36 am

alecsandros wrote:And in the historical engagement, Graf Spee received a large number of 6" shell hits, without suffering important damage.
But enough damage to cause the AGS to go running to Montevideo.......

Two of the hits were significant - as was noted by the Uruguayan inspection commission, including a two metre hole that could affect the ships seaworthiness in rough seas and another hit that had disabled the water distillation plant.
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