Triple and quatruple turrets

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tommy303
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Re: Triple and quatruple turrets

Post by tommy303 » Sat Dec 22, 2012 12:41 am

I am not aware of any major problems with the USN 16-in triples, nor the Italian 15-in triple, although the latter had a rather slow rate of fire. The USN 16-in/50 light weight guns were installed in a turret of similar dimension to the earlier 16-in/45. It was found that in service gearing for traverse was difficult to access, as well as other components. On the whole, though, they performed well. It should be stated that no mounting of the complexity of which we speak, whether it be a German 15-in twin or KGV's quad, is ever completely with out some sort of trouble, particularly early on when first installed and often it is a long and laborious task to set things right and give an acceptable level of reliability. Many problems are caused by drill errors on the part of the crews, while others might be caused by a poor designed component.

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Re: Triple and quatruple turrets

Post by Dave Saxton » Sat Dec 22, 2012 3:26 am

It should be stated that no mounting of the complexity of which we speak, whether it be a German 15-in twin or KGV's quad, is ever completely with out some sort of trouble, particularly early on when first installed and often it is a long and laborious task to set things right and give an acceptable level of reliability.
This is a good point and something that is not so well understood today when we are surrounded by high tech gadgets that require little to no maintenance. For example, we have cars today that don't require changing of the spark plugs for 100,000 miles. We don't need to get out and tap on the carburetor with a screw driver handle on occasion anymore. Things work alomost perfectly or they don't work at all today. In the recent past however, there could be a wide range of how well mechanical things worked.

I think it is fair to point out the concern over the problems of the KGV turrets originate with the Royal Navy itself and that has spilled over into the related technical and historical literature. They were indeed deeply dissapointed with the reliability of these equipment. I'm sure they expected problems, but they also expected better.
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Re: Triple and quatruple turrets

Post by Dave Saxton » Sat Dec 22, 2012 3:35 am

alecsandros wrote:Dave,
any leeds on the performances of German 2-gun 15" turrets and it's integration with radar?
...
I didn't mean the tone of my previous posting answering this question to come across the way it did. I now realize your question is more about how the guns performed using radar direction, rather than if it had the radar intergrated into the FC or not. I think Thorsten's findings speak for themselves regardless of if it was via radar data, optical data, or a combination of both, being feed into the firecontrol.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

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Re: Triple and quatruple turrets

Post by alecsandros » Sat Dec 22, 2012 11:17 am

Dave Saxton wrote:
alecsandros wrote:Dave,
any leeds on the performances of German 2-gun 15" turrets and it's integration with radar?
...
I didn't mean the tone of my previous posting answering this question to come across the way it did. I now realize your question is more about how the guns performed using radar direction, rather than if it had the radar intergrated into the FC or not. I think Thorsten's findings speak for themselves regardless of if it was via radar data, optical data, or a combination of both, being feed into the firecontrol.
Yes, this is what happens when I write fast :)

Thorsten's findings are as always fantastic, and they do shed more light on the matter.

My question above was in fact related to Bismarck's shootings during operation Rhinubung: salvos were fired against Norfolk, Hood, PoW, Suffolk, Sheffield, Vians destroyers, Rodney, KGV.
There accuracy of the fire was good, with a good number of straddles obtained on the targets.

What puzzled me always was the relatively low number of hits compared to the number of straddles [2 hits on Hood, 4 on PoW, 1 near-miss on Norfolk, 2 near misses on Vian's destroyers, 1 near-miss on Rodney, 1 near miss on Sheffield. In all likelihood, there were at least 250x38cm shells fired by Bismarck, not to mention the 15cm shells]

This can be, of course, explained by geometry of the battles, time of day, weather, speed and size of the targets (it's hard to hit a DD at 10km on rough seas and at night).

It can also have something to do with the incomplete artillery testing and drilling, and with insufficiently tuned RPC.

Some of those points are alluded in AVKS-700, and I always wondered wether the RPC was fully functional by the time of Rheinubung.

My best guess would be that yes, it was; however, I;m not suree...

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Re: Triple and quatruple turrets

Post by alecsandros » Sat Dec 22, 2012 11:22 am

Thorsten:
any info on the total number of shells fired by Tirpitz, speed and bearing of Hessen ?

thanks a lot,

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Re: Triple and quatruple turrets

Post by alecsandros » Sat Dec 22, 2012 3:03 pm

Digging around, I found some info on Hessen:

- speed 20kts (after 1935 rebuild)
- dimensions: 138m long, 22m width, 8m draft (destroyer size for WW2, lest the draft...)

So hiting this target 9 times at 25km seems to be quite good.

However, any info on the total number of 38cm shells fired would be very welcomed
(from Thorsten;s time intervals, it is possible that over 300 shells were fired on Oct11th and maybe 400 on Oct 12th. If, those were the days when Hessen was attacked)

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Re: Triple and quatruple turrets

Post by Dave Saxton » Sat Dec 22, 2012 3:44 pm

alecsandros wrote: What puzzled me always was the relatively low number of hits compared to the number of straddles ......This can be, of course, explained by geometry of the battles, time of day, weather, speed and size of the targets (it's hard to hit a DD at 10km on rough seas and at night)....2 near misses on Vian's destroyers
...
The shooting against Vians destroyers may hold the key to your questions regarding the effectiveness of radar intergration on Bismarck in 1941. First, it was certainly radar ranged fire at least with no help from artificial lighting such as star shell or search lights. Secondly, the shooting was spectacular. Read Grenfell's acount, which was given to him directly from Vian, and other accounts, and it becomes clear just how well Bismarck was shooting at these destroyers. Bismarck scored numeruous straddles, over an extended time period, while not opening up a sustained fire. It only fired very deliberately driving off the destroyers by a handful of extremely accurate salvoes as needed. Considering the conditions, Bismarck being crippled, and the probabilities of scoring direct hits without sustained fire, it was remarkable shooting. I don't think you will find another case of a battleship shooting so well at destroyers at night. Luetzow's shooting at Obdurate with radar directed blind fire was impressive though. It straddled and seriously damaged Obdurate with its first salvo from 15,400 meters range. Bismarck had twin turrets and Luetzow had triples if that means anything.
Entering a night sea battle is an awesome business.The enveloping darkness, hiding the enemy's.. seems a living thing, malignant and oppressive.Swishing water at the bow and stern mark an inexorable advance toward an unknown destiny.

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Re: Triple and quatruple turrets

Post by alecsandros » Sat Dec 22, 2012 5:09 pm

Dave Saxton wrote: I don't think you will find another case of a battleship shooting so well at destroyers at night. Luetzow's shooting at Obdurate with radar directed blind fire was impressive though. It straddled and seriously damaged Obdurate with its first salvo from 15,400 meters range. Bismarck had twin turrets and Luetzow had triples if that means anything.
...
Perhaps Scharnhorst hiting Saumarez during North Cape ?
Given the conditionst (very rough seas, severe damage to Scharnhorst's radars AND main artillery), hiting Saumarez at least twice from 3-4000m
Also, the 28cm hits on Sheffield during the same battle were impressive enough, as Sheffield was a small cruiser, and distance well over 12km, in poor visibility and rough seas.

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Re: Triple and quatruple turrets

Post by Thorsten Wahl » Sat Dec 22, 2012 7:57 pm

However, any info on the total number of 38cm shells fired would be very welcomed
(from Thorsten;s time intervals, it is possible that over 300 shells were fired on Oct11th and maybe 400 on Oct 12th. If, those were the days when Hessen was attacked)
the number of fired shells is unknown to me,
I dont think, Tirpitz fired so much projectiles, as it is absolutely not neccessary to fire until you hit a target.
The question of artillery is finding range and deflection (MPI on target) and their rates of change the rest is probability theory. And full caliber firing cost much money and barrel wear and hitting the targetship makes monetary things even worser.
And its known that the KM suffers from low amount of available ammunition for their heavy artillery at that time.

According "Denkschrift über das Ergebnis der mit Frontvertretern durchgeführten Untersuchung der Kriegsbauchbarkeit der Seeziel- und Flakartillerie auf Schlachtschiffen und Kreuzern und die für Neubauten hieraus zu gewinnenden Erfahrungen, B.Nr. Skl.Qu A I 2983/41 Gkdos".

"After World War II, the german development of anti-ship and anti-aircraft artillery was pushed forward under the following assumptions:
Fastest achieving of the first hit on the enemy, as far as possible with the first salvo, and at the same time fast and safe tracking of of the enemy
Independence of roll and pitch effects in the Atlantic even in bad weather
Independence of own ship maneuvers
100% technical reserve of fire control, targetting capabilities and ammunition feed."

according to that document they believed they had achieved this goal with Bismarck and Tirpitz as they(SKL) consider their(Bis, Tir) shootings as excellent.
Meine Herren, es kann ein siebenjähriger, es kann ein dreißigjähriger Krieg werden – und wehe dem, der zuerst die Lunte in das Pulverfaß schleudert!

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Re: Triple and quatruple turrets

Post by dunmunro » Mon Dec 24, 2012 9:51 am

Dave Saxton wrote:

The problems encountered by S&G's forward turrets during the April 9th 1940 squirmishs were due to water coming though the ejection ports with the turrets trained around with their backs facing the spray coming over the bows. The problems were mostly electrical, rather than mechanical, through the short circuits caused thereby. SH had to go over to back up systems instead of using the primary RPC.

The Germans didn't know that Renown was having similar problems. Bewteen 0419 and 0456 hours (British time) Renown was forced to reduce its speed more than once, because of the water coming over the bows made her forward turrets unworkable. At 0544 Renown had worked up to 29 knots, but had to keep the forward turrets trained around facing away from the water coming over the forcastle while doing so. Such was the sea state that day.
Renown ceased fire because her FC system could no longer generate a solution due to visibility, not because of water ingress into the forward turrets, which did not lead to a loss of output.

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Re: Triple and quatruple turrets

Post by alecsandros » Mon Dec 24, 2012 10:50 am

Thorsten,
I remember you found some coefficients for GErman battery firings, which could be applied to GKDoS100 figures.

Having teh coefficients for 2-gun firings (1 x turret firing), and the data from GKDOS100, we can find out, roughly, how many shells would be theorecaly needed to score 9 hits at 25km.

I don't remember exactly, but was the coefficient for 2-gun firing 1.1 ?

= If it was so, the dispersion for 2-gun firings would be ~ 130meters from the point of aim.
= Reconstructed Hessen had 138m length, 22m maximum width and about 6m height, and 8m draft.
Only the command tower and funnel were taller, at 18m and 15m respectively.
= Angle of fall of 38cm projectgiles at 25km would be 23.7*.
= Assuming perfectly parallel courses
= Assuming perfect data on range, course, speed of enemy target
= Assuming no gun wear, and no mechanical or electrical faults within the firing system
= Assuming pefect shell trajecctory
= Assuming 0 underwater hits
----------

Hessen deck surface (using ellipsoid area formula): S = pi x 11 x 69 = 2383 square meters
Hessen 1-side freeboard surface: roughly 138 x 6 = 828 square meters
Hessen command tower and funnel area (vertical cut) = roughly 12 x 3 + 10 x 4 = 76 square meters

----------

Projected area of target for 23.7* aof:
2383 x 0.402 + (828 + 76) x 0.916 = 958 + 828 = 1786 square meters

----------

In a very simplistic way (probably to simplistic...), 380mm 2-gun shots would end up in a circle with a radius of 130m, or, otherwise said, in a circle with a surface of 53066 square meters.

----------

Puting together the 2 figures, we would have, very roughly,

53066 / 1786 / 2 = 15 x 2-gun shots fired for maximum probability of a hit.

Otherwise said, about 30 shells needed to be fired for a hit on a target like Hessen...

-----------

IF the correction coefficient for shot dispersion is not 1.1, the solution changes accordingly....

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Re: Triple and quatruple turrets

Post by tommy303 » Tue Dec 25, 2012 6:34 am

I believe the normal method during full calibre shoots with Bismarck and Tirpitz, and presumably with the Hippers as well, was to fire by four gun turret groups. The reasoning for turret groups rather than two gun turret salvos was it was nearly impossible to estimate an MPI with just two shells; a four shell salvo was much more effective in that respect and made spotting and adjustments for range and deflection rather easier.

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Re: Triple and quatruple turrets

Post by alecsandros » Tue Dec 25, 2012 9:57 am

tommy303 wrote:I believe the normal method during full calibre shoots with Bismarck and Tirpitz, and presumably with the Hippers as well, was to fire by four gun turret groups. The reasoning for turret groups rather than two gun turret salvos was it was nearly impossible to estimate an MPI with just two shells; a four shell salvo was much more effective in that respect and made spotting and adjustments for range and deflection rather easier.
Thorsten found some adjustment coefficients for 2, 4 and 8 gun salvos.
I don't remember them, but I hope he could repost them when reading this...

The reason why I calculated for 2-gun shots was that both Thorsten and Dave mentioned photos of the shots against Hessen which depict 2-gun shots...

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Re: Triple and quatruple turrets

Post by Dave Saxton » Tue Dec 25, 2012 3:15 pm

Most of the handful of photos I have seen show TP firing four shot salvoes; either the forward turrets or the aft turrets together. One photos indicates that the aft group has fired (by the smoke) and the guns are back down to the reload elevation and the forward group is firing together.

TP is at speed with a bow wave (exagerated by the shock wave of the salvo), a thin stream ejecting out of the stack, and pretty good white water wake from the stern. In one photo, Anton fires alone with Bruno trained fore and aft. The guns all have those silver bands on them that were sensors to measure the MV from shot to shot.

There were shots fired not only at Hessen but also at at least two towed target barges with canvas tops during one of the shoots. One photo shows one large splash very close to a towed target.

A fall of shot photo (obviously taken from the remote control ship) shows a huge major caliber splash right at Hessen's belt line and another huge splash about 50 meters short, followed by a photo with a smoke signal indicating that a third shot scored a direct hit (the stills were taken from a motion picture film frames set). A fourth shot may have fallen beyond the Hessen, but its beyond the field of view. Another photo shows the inspection team inspecting the Hessen after the shoot.

btw, Merry Christmas to all, and to all a good night.
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Re: Triple and quatruple turrets

Post by tommy303 » Tue Dec 25, 2012 6:24 pm

During initial full calibre shoots, the guns might even have been fired singly instead of in any sort of salvo, but this was to measure the shot to shot variation so as to extrapolate the amount of wear caused by each shot and allow the Siemens technicians to incorporate that data into the fire control system. Normal gunnery practice was generally conducted using turret group salvos, as would be used in combat, though sometimes with reduced charges instead of full charges to reduce barrel wear.

As to hit probability for a salvo which has straddled a target ship, the figure is about 10% with a four gun salvo at 25 000 that one shell at least will hit or about 5% that two will hit.

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