Battleship Vittorio Veneto

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Re: Battleship Vittorio Veneto

Post by Bgile » Thu Jan 13, 2011 7:48 pm

Dave Saxton wrote:Removal of the cap has effect on the amount of precession and ultimately the amount of yaw. Removal of the cap increases the distance between the projectiles center of pressure and the center gravity. Complete removal of the cap will result in greater yaw as well as decreasing the shells penetration potential by removal of the cap.
I thought the purpose of the cap was to improve penetration of face hardened armor. Why would it's removal affect penetration of homogeneous armor?

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Re: Battleship Vittorio Veneto

Post by Dave Saxton » Thu Jan 13, 2011 8:33 pm

For one thing it reduces the mass of the projectile. Another factor is that for two projectiles of equal mass, one capped, and another un-capped, if the homogenous armour has greater tensile strength than 80 kg/mm2, it takes significantly more energy for the un-capped projectile to penetrate than the capped one. So the penetration capability of the projectile has been reduced in two ways by removal of the cap. This does not take into account any reduction of velocity, which the Germans found with materials such as Wh is significant for the amount of energy required for further penetration, nor the greater energy required for penetration because the projectile is striking while yawed, which yaw will be greater because the cap has been removed. The British found that a cap also helps the projectile initially bite into the homogenous armour better, thereby reducing the probability of scooping.

The cap's purpose could be described as an aid to penetration in the case of face hardened armour, but really the cap's primary purpose in the case of impact against face hardened armour is to prevent the projectile from being destroyed by the impact. Even against homogenous armour in the cases oblique impact, the cap helps prevent the projectile from being destroyed by axial forces by keeping the center gravity closer to the head of projectile. The center of pressure is a term often used to describe where the forces of decceleration are focused.
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Re: Battleship Vittorio Veneto

Post by lwd » Fri Jan 14, 2011 3:17 pm

Dave Saxton wrote:.... The center of pressure is a term often used to describe where the forces of decceleration are focused.
This would typically be the point of impact would it not? If so I can't see how the loss of the cap increses the distance between the center of gravity and the center of pressure.

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Re: Battleship Vittorio Veneto

Post by Bgile » Fri Jan 14, 2011 4:09 pm

I believe this would depend on the relative mass density and construction of the shell body and the cap. It seems to me that the center of gravity will likely move, but if the cap is less massive than the forward end of the shell body, the loss of the cap might actually move the center of pressure toward the center of gravity.

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Re: Battleship Vittorio Veneto

Post by lwd » Fri Jan 14, 2011 4:30 pm

It doesn't require a difference in density to have this affect. If for instance your shell was a cylander (choosing this for ease of explanation and math). If the shell was say 100 units long and the cap also a cylinder of the same diamteter and density was 10 units long then if the cap is removed the cg moves back 5 units. However the shell is now 10 units shorter so the cg is also closer to the front of the shell. If the shell is a cylinder with a conical tip then as long as the cap is conical with a hieght greater than or equal to that of the concial portion of the shell you will get a similar result. The fact that the back of the shell has a cavity for less dense explosives will actually tend to mean mean that even if the cap cone is shorter than the shell cone the cg is likely to be closer to the point of the shell after the cap is lost than it was before.

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Re: Battleship Vittorio Veneto

Post by WestPhilly » Fri Jan 14, 2011 5:23 pm

If only I understood all this. Is it fair to say that V. V. was roughly equivalent to its European contemporaries, at least in terms of a traditional gunnery engagement?

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Re: Battleship Vittorio Veneto

Post by lwd » Fri Jan 14, 2011 5:44 pm

WestPhilly wrote:If only I understood all this. Is it fair to say that V. V. was roughly equivalent to its European contemporaries, at least in terms of a traditional gunnery engagement?
I'd say yes. Indeed most of the modern battleships with the exception of the small ones and the Yamatos were relativly close performance wise at least in theory at least IMO. That is the odds wouldn't be any worse than say 60:40 and probably closer to 55:45 in most cases. Would depend on what you are taking into account though.

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Re: Battleship Vittorio Veneto

Post by Bgile » Fri Jan 14, 2011 5:59 pm

WestPhilly wrote:If only I understood all this. Is it fair to say that V. V. was roughly equivalent to its European contemporaries, at least in terms of a traditional gunnery engagement?
Yes. I think there was some excessive dispersion (kind of confused myself after all the back and forth), but that doesn't seem to have been a problem with the weapons, just some tolerance problems with the ammunition.

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Re: Battleship Vittorio Veneto

Post by Mostlyharmless » Sun Jan 16, 2011 6:27 pm

Bgile wrote:
WestPhilly wrote:If only I understood all this. Is it fair to say that V. V. was roughly equivalent to its European contemporaries, at least in terms of a traditional gunnery engagement?
Yes. I think there was some excessive dispersion (kind of confused myself after all the back and forth), but that doesn't seem to have been a problem with the weapons, just some tolerance problems with the ammunition.
The class may or may not have suffered from excessive dispersion. I am told that the article by Colliva in "Bollettino d'Archivio" (Historical Archive Bulletin) of the Marina Militare is the best discussion of this but alas I cannot read Italian :( (see http://warships1discussionboards.yuk...rformance.html). The Naval Weapons site says “Possibly the greatest contrast was seen between the shooting of Littorio in the first battle of Sirte Gulf and that of Vittorio Veneto in the 28 March Guado encounter. Despite the fact that Littorio was shooting at targets 32,000 yards away while Veneto was attacking at first Orion and afterwards Gloucester at only 24,000 yards, the Littorio's shot groups were significantly more consistent, despite the greater range, doubtlessly owing to a batch of properly fabricated 381-mm projectiles.” Thus if some batches of shells or charges gave high dispersion, it was only seen some of the time. I have seen it argued that it must have been the charges rather than the shell weights that were irregular as shell weight does not have such a dramatic effect on range.
I found a photograph at http://www.perthone.com/1matap.htm which shows the dispersion of a single salvo at Matapan on 28th March 1941 as seen from the RN cruisers. The dispersion of the triple salvo seems to be twice the length of the cruiser or roughly 420 yards. That would be judged OK by the USN, who wanted 1.6% to 1.9% of range, IF it had been a full salvo. I am not a statistician but I think :think: that a nine shell salvo will have twice the dispersion of a three shell salvo on average. Thus the dispersion was roughly twice what it should have been. This is poor but is similar to the Richelieu class problems (575 yards at 29000 yards).

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Re: Battleship Vittorio Veneto

Post by RobertsonN » Mon Jan 17, 2011 11:30 am

Such actions as occurred in the Mediterranean were usually long range running fights in which no direct hits were scored because of the extreme range (26000 to 32000 yards). This pattern was mainly the result of one side being clearly superior to the other (for example, British 6 in cruisers usually retreated from 8 in Italian ones because they were badly outranged). The limit of the Italians' ambition was to ensure that Italian convoys got through to Libya and that British ones did not get through to Malta. Matapan was the exception to this but German pressure to intercept Alexandria to Greece convoys was the reason.
The greatest "success" of the VVs was in forcing a British convoy from Alexandria to Malta to turn back through their being in a position to intercept it in June 1942. This was the occasion on which Littorio was hit by a bomb of US high level bombers and a torpedo from an RAF Wellington. At this stage of the War, Malta was of little offensive use as a base. The tide turned in August when the giant Pedestal convoy got through. Only Italian cruisers tried to intercept this because of a fuel shortage. On the other hand, all Allied resources had to be mobilised, with convoys to Russia being suspended. This confirmed Stalin in his view that the Western allies were happy to let the Russians do most of the fighting against the Germans.
Cunningham said in his memoirs that because the Italian battleships remained in existence the British had to keep some reasonably up to date battleships in the Mediterranean for the eventuality that the Italians did come out for a fight. This meant that up to late 1943 Britain had no modern ships to field against the Japanese. The four Revenge class formed a "fleet in being" in the Indian Ocean and pretended to be a threat.
When Italy surrendered, Churchill apparently wanted to tropicalise the VVs and use them against the Japanese. There was also a plan to use one of them for bombardment during the invasion of southern France, but this was given up for political reasons. Churchill had also in 1941 offered Stalin British ships to replace Russian losses after the war. In late 1943 Stalin wanted some of the now available Italian vessels, but all he got were some old British and American ships. After the war, Stalin again wanted one of the VVs but had to make do with the ancient Guilio Cesare. Maybe the VVs were too good for the Russians.
The employment of the VVs showed very limited ambition, however they were more actively employed than the Yamatos, at least in the period (up to July 1942) when the outcome of the War lay in the balance.

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Re: Battleship Vittorio Veneto

Post by RobertsonN » Tue Jan 18, 2011 9:30 am

Mostly Harmless wrote ... "dispersion of three gun salvo from Vittorio Veneto about 420 yards at 24000 yds ... dispersion of Richelieu was 575 yards at 29000 yds".

These seem very high although they may well be correct. Official German sources (given on KBismarck web site and in "German Capital Ships of World War 2" by Whitley) show curves for the German 38 cm gun giving much lower values for dispersion, for example 140 m at 30000 m (i.e. under 0.5%). Even so, the hit probability (danger space/dispersion) is less than 0.5. And this assumes that target speed and course are exactly correctly estimated, and that there is no change of speed or course of the target while the shells are in the air, together with a correct evaluation of the wind at various altitudes, etc.).
These figures illustrate why the greatest range at which one battleship ever hit another moving battleship was 26000 yds.

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Re: Battleship Vittorio Veneto

Post by Mostlyharmless » Wed Jan 19, 2011 12:12 pm

There are several threads in various for a discussing dispersion. One big problem is that some numbers refer to the dispersion of shots from a single gun on the proving field while others are from ships at sea. When you try to calculate for a full salvo at sea, you then have the choice whether you use all the shells or exclude some “outliers”. “Naval Firepower: Battleship Guns and Gunnery in the Dreadnought Era” by Norman Friedman & A. D. Baker seems critical of Italian dispersion on page 310 but gives only 320 m at 27,000 m for the Littorios. For comparison, on page 185 they report 1352 yards at an average range of 23,959 yards for California in 1924-5 battle practice compared to 558 yards for Maryland. However, the problems with the US 14/50 were solved before WW2. The articles by Bill Jurens at http://www.navweaps.com/index_inro/INRO ... ery_p1.htm and http://www.navweaps.com/index_inro/INRO ... ery_p2.htm give helpful data and show how dispersion decreased with time.
I suspect that Germany and Japan aimed at smaller dispersions than the USN. The Americans commented that the Japanese patterns were too tight at Leyte causing them to miss US destroyers.

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Re: Battleship Vittorio Veneto

Post by Bgile » Wed Jan 19, 2011 4:08 pm

Obviously if your dispersion at 30,000 yds is only 150m you are going to have a very hard time hitting any ship, since a very small error in FC or a small maneuver by the target is going to take it out of your pattern.

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Re: Battleship Vittorio Veneto

Post by tommy303 » Wed Jan 19, 2011 7:11 pm

Obviously if your dispersion at 30,000 yds is only 150m you are going to have a very hard time hitting any ship, since a very small error in FC or a small maneuver by the target is going to take it out of your pattern.
The Royal Navy also sought and achieved very small dispersion patterns, but once achieved, found they had to spread the line to increase the pattern size slightly and thus enhance the possibility of hitting in the face of minor errors in range or with very small targets. If I recall, the British noted Hipper's salvo patterns at the Barents Sea action were very small and commented that the Germans did not appear to be spreading the line. It is possible though, that the Germans, having a high velocity low trajectory gun to work with, did not feel the need to do so at most battle ranges up to about 20,000m as the danger space would have been fairly wide and in some measure would have negated slight errors in range estimate.

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Re: Battleship Vittorio Veneto

Post by Dave Saxton » Wed Jan 19, 2011 10:23 pm

The Germans appear to have been capable of exceptional precision in terms of range estimate, meaning that they would not need to expand their line much. I know that by 1943 their radar was accurate to 25 meters regardless of the distance to the target.
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