Richelieu and Jean Bart

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alecsandros
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Re: Richelieu and Jean Bart

Post by alecsandros » Wed Nov 14, 2018 8:22 pm

Also, the timeframe of Jean Bart's salvoes on Nov 10th was between 11:41 to 11:51AM, or 10 minutes to fire 10 salvos.
That's a round 1 minute/salvo, and, as each salvo had 2 guns, it means each gun fired 5 shells, therefore "rate of fire" was 1 shell/2 minutes/gun, or 0.5 shells/minute/gun - a very low rate of fire by any metric.

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Alberto Virtuani
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Re: Richelieu and Jean Bart

Post by Alberto Virtuani » Thu Nov 15, 2018 10:42 am

Hi Alec,
I do agree: re. RoF, it may not have been a problem, in this specific case.

However, to fire a single gun out of the two belonging to the same half-turret, would imply to double the theoretical time to re-load and fire, and except the test mentioned by GiZi and this specific case, I see no reason why this procedure could have been used "in action"... :think:


Bye, Alberto
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Re: Richelieu and Jean Bart

Post by alecsandros » Thu Nov 15, 2018 3:18 pm

Well, instead of having 1.33 salvos per minute with 1km dispersion, perhaps they preffered 0.5 salvos per minute with 200m dispersion. That way at least they had an honest chance of hitting. (Hypothetical numbers used !)

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Re: Richelieu and Jean Bart

Post by Alberto Virtuani » Thu Nov 15, 2018 7:29 pm

:ok:
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Re: Richelieu and Jean Bart

Post by GiZi » Tue Nov 20, 2018 4:47 am

Alberto Virtuani wrote:
Tue Nov 13, 2018 9:16 am
Hi GiZi,

I agree on almost everything you have written above regarding Littorio's. A comment and an answer for you:
you wrote: "not only do most accounts of the action only describe Orion and Gloucester being targeted, but the image's caption also describes the salvo as being an over of Orion rather than being aimed at Perth"
I know that, but the British cruisers were (at that stage of the battle) on a front line (roughly) and Orion should have been on the starboard side of Perth (possibly the smoke we see on the extreme left side of the photo). Thus, if this picture shows a salvo aimed at Orion, it should have been a short and not an over.
The VV GAR doesn't specify which ship was targeted at what time, but it says that VV had to switch target several times (not only once) during the action, due to the maneuvers and the British smoke, thus it is IMHO more probable that the salvo is actually aimed at Perth, wrong for line (a bit too much on the right, as British ships were zig-zagging at each VV salvo) and good but dispersed for range. We will possibly never know, as British may not have registered it as aimed at Perth if VV, immediately after, changed her target to Gloucester.
Hi Alberto,

Thank you for the explanation - I think I may be confusing the orientation of the cruisers at this point in the action. I was under the assumption that the cruisers still had not quite turned away yet, but from what I understand, at the point the image was taken the ships were in open flight? Also, would I be correct in assuming the images are taken from Gloucester? In any case, if at this point they are heading south than I agree the salvo surely must be a short.
As far as which ships were targeted, if the GAR states targets had to be changed more than once, I cannot argue with that! :lol: Especially given how difficult it may have been given the time it took for shells to arrive versus target movement (since it took 26.35 seconds to reach 18.5 km for Palla, I imagine to reach 23-25 km it must have taken over 30 seconds - although I'd assume because the targets are cruisers, Granata Perforante would be fired rather than Palla?).

Out of curiosity does the VV GAR/the books using it list which turrets fired for which salvoes? By my own math, for 29 salvoes & 105 shells ordered to fire, the total must have been split between 6 salvoes of two turrets, and 23 salvoes of 1 turret. That leads to an average rate of 1.26 salvoes/minute, or the salvoes being fired once every 47.6 seconds (as total time of firing was 23 minutes), but it would be interesting to see if it is possible to break it down by turrets firing, and thus see how often guns were firing.
You are right, but the scheme seems to be vulnerable to airplane bombs more than to ships plunging fire, as the "citadel" (corazza di murata) 70 mm armor grade would decap anyway the shell at medium range (thus having a "Bismarck" like protection of 70+100 mm, leaving only a (less probable) very long range shell to be able to penetrate it due to the thin 36 mm armor grade upper deck (36+100), being possibly unable to decap the shell (that had to pass anyway also through the ship superstructure above machinery, being possibly activated). Please see Bagnasco scheme for armor thickness:
I know of the vulnerability to aircraft bombs, and it seems to have become quite the concern as the war wore on. To again borrow from Bagnasco, he describes the May 1935 tests of deck armor as being able to resist 1,250 kg 'Standard' bombs (General-Purpose, I assume?) dropped from 2500m with relative ease, but 800 kg Armor-Piercing bombs dropped from 2500m or higher at 250m/s as penetrating all armor deck layers. Meanwhile, the 1943 tests (June-July?) found all areas vulnerable to 820 kg AP bombs dropped at 4300m (5700 for turret roofs), and 480 kg at 5700m (7200m for turret roofs). 160 kg bombs, it seems, could not do the same, although penetration is described as 'far from negligible'. Another 'combat test' for bomb resistance would be the loss of 3ª Div at La Maddalena - the American heavy bombers dropped 1000 lb. (454 kg) bombs from 5000-6000m, which were able to penetrate Trieste's 50mm main armor deck, and dealt heavy damage that caused the ship to capsize. However, Gorizia withstood the bombs to a far greater degree, as although the roof of her No.3 turret (70mm, iirc?) was penetrated by a bomb (causing heavy damage), the main armor deck (70mm thick, with a 20mm upper deck) was able to resist penetration by the bombs, and this fact seems to have proven decisive to the survival of the ship. I'm not sure if these bombs were General-Purpose of Armor-Piercing, but given the figures for the Littorio (480 kg @ 5700m for 100-150mm + 36mm), I assume they were GP. To be honest, I've never come across other figures for other battleships, but it would be interesting to compare to the figures given for the Littorio-class.

In regards to resistance against shells, I hadn't really taken decapping into account. While I've read about decapped shells against Cemented armors, I'm honestly not very familiar with the affects of a decapped shells against homogenous armor, so I wasn't sure how to approach it. Decapping would obviously increase resistance, but by how much I'm not sure - so I'm not really sure how to judge it against against a single-thickness deck.
I don't think any of Iachino's books have been translated in English, unfortunately as it was not also the "ultimate" Mattesini book ("L'operazione Gaudo e lo scontro notturno di Capo Matapan", USMM, Ufficio Storico Marina Militare, 740 pages covering all aspects and including several original documents) in which the VV GAR data have been used (included in the final fleet command operation report, mentioning the 94 shells in 29 salvos and speaking of a first opening salvo of the 2 fore turrets only) and the corrective actions have been mentioned as well.
Iachino mentions the corrective actions as a whole (not only dispersion) in two book: "Gaudo e Matapan", 1946 and in "Il punto su Matapan", 1969 (out of the three ddicated to Matapan and the preface to the Italian version of Pack's book).

The only corrective action he suggested by Iachino to Riccardi (Capo di Stato Maggiore = First Sea Lord) and Mussolini (the "Duce" wanted to meet him immediately after the disaster...) re.dispersion was the improvement of the quality controls vs. ammunition provider firms.

The other suggested improvements regarded other deficiencies emerged during the tragic operation:

"Short term" actions:
1) Improvements to lighting shells and guns (both were bad): partial success (and no projectors usage foreseen anyway for RM)
2) Reduced flash powder introduction for main guns (successful)
3) Night fighting training start on all large warships for main guns (not foreseen up to then) (partially successful as gap with British was big and anyway the secondary guns fire directors had to be used to provide data to fire control, as main directors had no suitable night optics installed).
4) Investigations over the possible treachery/espionage episode that had allowed British to be aware of the Italian operation precise date, being at sea with the whole battlefleet the same day (Italians could not imagine yet about Enigma decrypting...)

"Long" term actions:
1) Radar development and implementation (+ requests to Germans for help) (partially successful only few month before the armistice in 1943)
2) Carriers construction (unsuccessful, it was clearly too late to complet any before the armistice)
Interesting, thank you for the response. It sounds like at the very least I'm going to have to see if I can get my hands on Mattesini's book!

Looking at the list of improvements, it does seem success was varying. Ironically, I've read that Fiume actually sailed for Op. Gaudo with experimental flashless charges for the 203mm guns - the trials had been conducted the night before, but the documentation as to the results were lost when she sank. Out of curiosity, when did such charges start to arrive for the 381mm guns?
Also, in regard to the direction of fire by night - by secondary directors, do you mean the Nocturnal APG's, behind all the enclosed aircraft lookout stations next to the bridge? Or do you mean something else by directors? And as far as espionage - a red herring, for sure, as there was no way to know enigma was compromised. It's also a shame that some authors post-war decided to latch onto the idea of a spy giving away the information resulting in the Matapan ambush. Although it is well before my time, I imagine the release of information regarding ULTRA must have caused quite the ripple through the naval community, given how many false conclusions could be reached without accounting for ULTRA (For example - almost half of all losses from the convoys from Italy to North Africa were the result of direct ULTRA intelligence).
Contrarily to what is usually accounted, and despite reciprocal accusations between Rome and Berlin, the cooperation with the Regia Aeronautica (Air force) and German Luftwaffe was not so bad during the operation (see Mattesini book), but it was simply impossible to provide a constant air cover to the fleet so far from the airfields. What was very bad was the interpretation of Italians and Germans pilots sightings done by Supermarina (Admiralty) in Rome, that did not keep Iachino well/clearly informed of the proximity of the British battlefleet.

Mussolini approved all these above suggestions (including the quality control amelioration re. ammunition, of course, that was quite successful, at least looking at the results of following gunnery trials) but added a (very heavy) limitation for the RM: "Prohibition to plan any action at more than 100 miles from the Italian land airfields of Regia Aeronautica, waiting for the carriers to be ready". This order, issued officially on March 31 1941, and never officially removed, affected negatively the whole war for the RM, especially during Crete evacuation.
With what was available for Op. Gaudo, I agree it would have been very difficult for either the Regia Aeronautica or Luftwaffe to provide air cover to the fleet, although had co-operation between the Navy and Air Force prior to the war been better perhaps better arrangements for air cover could have been possible. Again - the lack of effective reconnaissance is not just due to those flying, but how the data was interpreted - and the inefficient manner by which information from pilots had to be relayed back to superaereo and then to supermarina, who only then could inform the admiral at sea (if I'm understanding the process correctly) precluded information from being received in a timely manner. If Iachino, or any admiral at sea, was able to directly receive the reports of pilots, or from nearby stations, without having to go through high command in Rome, then they could much more rapidly receive and interpret information. That is an issue that extends well beyond the scope of Operazione Gaudo, and in many regards only looked to be solved in some regards by 1943 (with the fighter-direction abilities equipped to the battleships).
alecsandros wrote:
Tue Nov 13, 2018 5:28 pm
GiZi wrote:
Tue Nov 13, 2018 3:11 am
Indeed, that table is one of the references I've been using. Given the basis of Italian gunnery was on turret salvoes, I think it's safe to assume all recorded figures are for 3-gun turret salvoes. I do wish more information was provided in regards to number of rounds/salvoes fired, and what the conditions of the target was (as hit rates are listed). The pattern from the figures is somewhat difficult to use due to how wild Vittorio Veneto's figures are.
Bagnasco comments, that "[gunnery practice results] suffered a rapid and progressive increase as the range to the target rose (for example: nearly 400meters at 22-24.000meters)".

But the table does not include gunnery results for firings over 22000meters - therefore the 22.000 to 24000 meters commentary must come from analysis of other data, not included in the table of Annex no 3.

We need to compare the available information at correct ranges.

Jordan/Dumas give results for Richelieu out to 25km. We do not have data for Littorio firing out to 25km - but presumably the dispersion was very large.

I should add to this that Littorio class dispersion problems mainly came from uneven powder cartridges used - the mass of the powder varying from charge to charge, because of issues in the manufacturing process. During some trials, the producer (manufacturer) reportedly prepared good batches of powder charge, in effect producing consistent patterns of salvos. In normal loading of the battleships however, there was no such strict quality control, and various qualities of powder arrived on board. This not only produced somewhat different "explosions" inside the guns, thus creating different muzzle velocities - and ranges per gun, but also caused different (uneven) erosion inside the gun barrels, thus causating prolonged troubles for future firings as well.
Perhaps there is additional data - to be honest, I had always assumed the datapoint of 'almost 400 meters at 22-24 km' was derived from Littorio's 1939-1940 shoot at 22.5 km, which resulted in 364m dispersion (1.62%). I may easily be wrong though, although I would have expected Bagnasco to have shared the information in annex no. 3 if he had other information.

Unfortunately I've never seen long range data of dispersion for any of the ships - only that the British noted VV's dispersion to be particularly bad at Gaudo, while the same observations were not present in regards to her long-range shooting at Capo Teulada/Spartivento, or Littorio's fire at either battle of Sirte. The only 'hard' information I have is, at a range of somewhere between 28.5-32.5 km (Bagnasco) or 29.3-36.6 km (O'Hara quoting Campioni), a 3-gun salvo from VV's aft turret produced this spread straddling Manchester;

Image

Which appears to be a little over 200 meters.

Such a value is very accurate, and if due to a 'proper' batch of ammunition, would seem to be consistent with comments about the gun that credit it as highly accurate when ammunition quality was good. That is why, as I mentioned early in the thread, I think that much of the comments about bad dispersion may be relatively 'isolated' to the early 1941 period, as the dispersion of Littorio was much more consistent than VV, who in contrast saw a huge increase going into 1941 - around the time of the engagement with British cruisers off Gavdos. That seems to be very likely down to VV being given a bad load of ammunition prior to the engagement, which, given ammunition testing methods, would pass undetected by the RM. As discussed before - the results are well known, with the poor dispersion of the VV being noted by both the Italians and the British, and this lead to quality control improvements and more careful examinations of the ammunition. I consider the fact that dispersion as an issue for the 381mm guns does not appear after this period, either from Littorio in combat, or for the exercises of any of the sisters - performance of the 381mm guns is repeatedly described as satisfactory or better. I definitely agree that the inconsistent charges were a major issue - the 381/50 M1934 was very sensitive to velocity and elevation*, so any variation in charge performance would affect it to a greater degree than most other naval guns (the same was true for most Italian guns, due to the emphasis on high velocity for many of the '20s & early '30s projects). The guns have been described as 'painstaking' to calibrate as well, so uneven wear would hurt them greatly. I don't recall Bagnasco describing how often they were relined, but certainly until that point the uneven wear from the early war would haunt the fire control crew!

*I emphasis elevation because of how much variation could affect the range spread of the guns. As Bagnasco states, the variation of a single thousandth, .05625º, could result in a round falling long or short by 83.4 meters - so even 0.1º would change the range by 148.3 meters! I think the fact these 381mm guns had greater range at an elevation of only 36º than the 460mm guns of the Yamato at 45º is one that many don't grasp from a point of view of not just raw power, but also sensitivity. Very, very slight changes in elevation affect the guns to a greater degree than many others, so if each gun is not appropriately elevated, it could easily increase dispersion. If uneven wear means the elevation of the gun will always be slightly off... Ouch!
I misread, sorry.
Those must be some sort of averages for different ranges. It's highly unlikely that dispersion remained the same for 16000 meters as for 25.000 meters firings.
No problem, it happens! I think I did a poor job of explaining it the first time, so the fault is mine. And I agree, it is extremely unlikely that the dispersion was the same over such a large range span (6000m). Unfortunately those are the only figured Jordan & Dumas give, for both Richelieu shoots, and the figures for Queen Elizabeth, which leaves me somewhat frustrated as I'm not sure for which range (16 or 25 km) they are more appropriate.
S: Jean Bart's 2 x 380mm gun salvos , fired on Nov 10th 1942 against CA USS Augusta from range ~ 18000meters certainly did not exhibit 450meters dispersions, as Augusta was nearly directly hit by the shells, and her decks were put awash. Out of 10 x 2 x 380mm shots salvos, the "last three" being "close straddles". (according to Morrison, operations in North African Waters, pg 163)

PS2: Interestingly enough, an online book depicting Jean Bart's sole turret firing against USS Augusta , shows guns being fired from odd and even barrels. I.e., gun1 with gun3 and gun2 with gun4. If this is a correct depiction of the actual firing being executed on NOv 10th, it may explain the better dispersion - then that exhibited by Richelieu , firing with gun1 and gun2 or gun3 with gun4 - as distancce between barrels was substantialy larger for the method employed on Jean Bart, and therefore shell interference was smaller. ("Operation Torch 1942: The Invasion of French North Africa", by Brian Lane Herder, pg 58)
Also, the timeframe of Jean Bart's salvoes on Nov 10th was between 11:41 to 11:51AM, or 10 minutes to fire 10 salvos.
That's a round 1 minute/salvo, and, as each salvo had 2 guns, it means each gun fired 5 shells, therefore "rate of fire" was 1 shell/2 minutes/gun, or 0.5 shells/minute/gun - a very low rate of fire by any metric.

Well, instead of having 1.33 salvos per minute with 1km dispersion, perhaps they preffered 0.5 salvos per minute with 200m dispersion. That way at least they had an honest chance of hitting. (Hypothetical numbers used !)
That's very interesting. Which online book? That sounds like a very interesting read. It would certainly explain why her dispersion was so tight - using a single gun from each pair at a time would allow for significantly tighter spreads than what would result from the usual half-turret salvoes - as an example, the Trincomalee firings - the single-gun dispersion being 60% of what it was with half-turrets.

As far as rate of fire goes, for 8 November Jordan & Dumas describe her as firing four 2-gun salvoes between 0708 and 0719 at 22000 meters, for 1 salvo every 2:45 (0.36 salvoes/min), for a rate of fire of 0.18 rpgpm (330 seconds).

For 10 November, Jordan & Dumas give nine 2-gun salvoes (from 1141 to 1151), not ten, and although one of my books by O'Hara describes ten salvoes, a later one by the same author describes 9 salvoes instead, so I think that may be the actual figure - not that it changes much, 0.9 salvoes/min, or 0.45 rpgpm (133 sec).

The range is given as 16000m by Jordan & Dumas, who describe the second salvo falling close enough that "the great orange shell splashes drenching the bridge and upper decks", and also says the last three were straddles. The rate of fire, however, may not be as slow as one might think - on 25 July 1945 during Operation Crimson (bombardment of Sabang), Richelieu fired 21 salvoes in just over 20 minutes, 4-gun salvoes using a half-turret salvoes from each turret, for a rate of fire of 1 salvo every 50 seconds (1.2 salvoes/minute), which one would assume means 0.6 rpgpm (100 sec). This rate of fire is described by Jordan & Dumas as "... almost twice the rate of fire of the other battleships", the other battleships being Queen Elizabeth, Valiant, and Renown. Expenditure was 81x 380mm shells rather than 84, so I assume there were 3 failed rounds. Range was about 6000 meters.

For further examples - Vittorio Veneto at Capo Teulada/Cape Spartivento fired seven 3-gun salvoes from her aft turret over the course of 10 minutes (1300 to 1310), for a rate of fire of 0.7 (salvoes and rpg)/minute (85.7 sec), range 28.5-32.5 km.

At Punta Stilo/Calabria, Warspite fired 10 2-gun salvoes from her fore guns at 4ª Div over the course of 4 & 1/2 minutes, for a rate of 2.2 salvoes/min (every 27 sec), or 1.1 rpgpm (54 sec). After her 360º turn, she fired 6 more salvoes over the course of 2 minutes, although I'm not sure how many turrets were involved - rate would be 3 salvoes/min (20 sec), assuming only fore turrets still, that would be a rate of 1.5 salvoes/min, or about ever 40 seconds. In her gunnery duel against Cesare she fired 17 salvoes in 11 minutes (1.55 salvoes/min), but I'm not sure what the output per gun was. Cesare fired 74 rounds in 15 minutes, but I've no idea what the salvo count was. Range was 26-29 thousand yards (23.8-26.5 km) for the BB engagement.

Iowa fired 5 8-gun salvoes in 11 minutes at extreme range against the destroyer Nowaki, 40 rounds total (0.45 salvoes/min, rpgpm is the same I think - every 132 sec). In the same engagement and at similarly long range, New Jersey fired 7 salvoes, mostly 3-gun, over the course of 9 minutes for 18 rounds fired (0.77 salvoes/min, or every 77 seconds). I'm guessing they were all fore guns, so rpgpm would likely be 0.39, or every 154 seconds.


Overall, given Richelieu's own performance in the Far East (and this being after JB's action), I'd assume half-turret salvoes were the 'norm' regardless, and the use of alternating guns from each half-turret would not be used - although I am very curious to see what prompted it. Perhaps difficulties with loading the guns made it pointless to try and load one half-turret and then the other? Either way, the rate of fire may have not been particularly fast, but compared to many other examples it's far from glacial.

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Alberto Virtuani
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Re: Richelieu and Jean Bart

Post by Alberto Virtuani » Tue Nov 20, 2018 9:37 am

Hi GiZi,
please find the answers I'm able to provide....
you wrote: "would I be correct in assuming the images are taken from Gloucester? In any case, if at this point they are heading south than I agree the salvo surely must be a short."
This is a very interesting question, I was unable to answer up to now. To have an answer we should know the exact sequence of the cruisers when sailing in line, before the turn to south (when the photo was taken), that is not specified in any Italian document. I imagine Orion was leading as flagship, we see Perth in the photo, but I cannot say whether the photo was taken from Glocester or from Ajax (I suspect the latter as Glocester should have been behind, loosing ground due to her machinery problems)... Does anybody have to order of the British line before the turn away from any British source ?

Strangely enough, the VV GAR speaks explicitly of 94 "palle" (AP shells) fired during the action, no SAP ("granate perforanti") nor HE shells ("granate dirompenti").


you wrote: "does the VV GAR/the books using it list which turrets fired for which salvoes? "
Unfortunately, it doesn't. The GAR only mentions the failures by turret, not giving the expended rounds/ordered shots per turret. So we can have any combination of single turret salvos and two turrets salvos + possibly some broadsides (difficult due to battle geometry and distance but not impossible as VV had blind spot of only 20° per side for the aft turret). I agree with you that the most probable is 23 + 6 +0, however turret 3 fired as well during the battle as the GAR lists her few failures as well.


you wrote: "it would be interesting to compare to the figures given for the Littorio-class."
AFAIK,I don't think any WWII battleship was designed to (and actually could) resist AP bombs dropped from high altitude bombers.


you wrote: "I'm honestly not very familiar with the affects of a decapped shells against homogenous armor"
All armored decks in Littorio's were armor grade steel, homogeneous armor steel comparable to homogeneous Wh in Bismarck, as well as the upper belt of 70mm. The non-armor grade steel = construction grade steel (high resistance, "elevata resistenza") is marked as ER in Bagnasco's scheme (viewtopic.php?f=14&t=8342&start=15#p81278). The NiCr plates were something comparable to Ww (less resistant but more elastic than Wh), used in connection with the torpedo system, where huge vibration/deformation was to be faced.


you wrote: "do you mean the Nocturnal APG's, behind all the enclosed aircraft lookout stations next to the bridge? Or do you mean something else by directors?"
The main battery was directed by the secondary armament fire directors at night, with clear limitations as the main directors were not carrying any night optic. No modification was planned to the main directors.


Bye, Alberto
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Re: Richelieu and Jean Bart

Post by Thorsten Wahl » Tue Nov 20, 2018 1:36 pm

Decapping would obviously increase resistance, but by how much I'm not sure - so I'm not really sure how to judge it against against a single-thickness deck.
the problem appears more difficult. and ist not only the effect of decapping one has to taken into account.

If protection is increased or not depends also from the the distance between the first impact and the main armor deck - the more time the projectile has to change ist orientation.

To small a distance under certain circumstances may reduce effectiveness of spaced armor. so that the critical velocity to pentrate both plates is lower than the critical velocity for the main armor plate alone.

it may be different and it appears case sensitive.
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Re: Richelieu and Jean Bart

Post by Alberto Virtuani » Tue Nov 20, 2018 3:26 pm

Thorsten Wahl wrote: "Too small a distance under certain circumstances may reduce effectiveness of spaced armor"
Hi Thorsten,
true, but in case of Littorio's, the distance between the "de-capping" weather deck and the main armored deck is the same as in Bismarck's (2 decks). The only "problem" of the Littorio's is the thin (36 OD steel + 9 ER steel) de-capping weather deck, not really able to de-cap heavy shells at any but quite low impact angles.

Richelieu's armored deck were separated by only one deck distance, but the upper MAD was thick enough (150-170 mm) to probably stop any shell at low and mid impact angles, even if French steel quality may be somehow questionable.


Bye, Alberto
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Re: Richelieu and Jean Bart

Post by Dave Saxton » Tue Nov 20, 2018 4:16 pm

Alberto Virtuani wrote:
Tue Nov 20, 2018 3:26 pm

true, but in case of Littorio's, the distance between the "de-capping" weather deck and the main armored deck is the same as in Bismarck's (2 decks). The only "problem" of the Littorio's is the thin (36 OD steel + 9 ER steel) de-capping weather deck, not really able to de-cap heavy shells at any but quite low impact angles.

In the German system, the in between deck is 6mm ST52. This is an indicator that they were cognizant of the need for precession to become fully manifest. The Italians are also demonstrating an understanding of influence of yaw by setting the distance between the upper deck and they main armoured deck as they did. However, it would have been better to reduce the thickness of 12mm ER deck more, so as to be less likely to upset precession from coming more fully manifest.

Nutation and precession effects are present during striking angles against such systems close to the normal, as well as during more oblique striking angles, as long as the outer plate is just heavy enough. It is the consumption of sufficient energy that initiates these yaw effects. The effects can be active against bombs and other projectiles striking close to the normal.

I agree with your assessment that no WWII battleship deck protection was fully effective against bombs of high striking velocity at or close to the normal.
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Re: Richelieu and Jean Bart

Post by Alberto Virtuani » Tue Nov 20, 2018 5:53 pm

@ Dave Saxton,
:ok:

One question, in addition to the thicker deck in between the 2 armored ones, Littorio's did not use armor as a structural component of the ship, thus the weather deck was 36 armor grade steel + 9 ER construction steel. We know that 36 + 9 is NOT = 45 mm in terms of protection, even in case we speak of two armor grade plates, so I expect the 9 mm ER to give very little improvement in terms of penetration.
Would they help in terms of de-capping ?

Also, would the 9 mm ER help or not (or even "damage") in terms of precession/nutation process of the shell ?


Bye, Alberto
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Alberto Virtuani
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Re: Richelieu and Jean Bart

Post by Alberto Virtuani » Tue Nov 20, 2018 10:52 pm

Hello everybody,
I wrote: " the VV GAR speaks explicitly of 94 "palle" (AP shells) fired during the action, no SAP ("granate perforanti") nor HE shells ("granate dirompenti")"
I have to correct my above statement: 94 "palle" (AP shells) fired during the Gaudo action, no SAP shells ("granate perforanti"). HE shells ("granate dirompenti"), that had been produced for the 381 gun, were not carried on board, at least at that stage of the war.


Bye, Alberto
"It takes three years to build a ship; it takes three centuries to build a tradition" (Adm.A.B.Cunningham)

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Re: Richelieu and Jean Bart

Post by Dave Saxton » Wed Nov 21, 2018 3:17 am

Alberto Virtuani wrote:
Tue Nov 20, 2018 5:53 pm
@ Dave Saxton,
:ok:

One question, in addition to the thicker deck in between the 2 armored ones, Littorio's did not use armor as a structural component of the ship, thus the weather deck was 36 armor grade steel + 9 ER construction steel. We know that 36 + 9 is NOT = 45 mm in terms of protection, even in case we speak of two armor grade plates, so I expect the 9 mm ER to give very little improvement in terms of penetration.
Would they help in terms of de-capping ?

Also, would the 9 mm ER help or not (or even "damage") in terms of precession/nutation process of the shell ?


Bye, Alberto
Krupp engineers determined that the effective thickness of deck laminates could be determined accurately enough by a simple formula. The effective thickness is the square root of the sum thickness of (each plate squared). This indicates that backing plates have little to no significance either way. The significance is so small that type of material of the backing plate will not matter much. As I recall, some British tests indicated that the effective thickness was greater if there was space between the plates instead of being in direct contact.
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: Richelieu and Jean Bart

Post by Alberto Virtuani » Wed Nov 21, 2018 7:48 am

Hi Dave,
in terms of thickness, I agree the 9 ER mm would not add much to the 36 OD mm.

I wonder whether they play a role in order to help de-capping the shell and/or enhancing the jawing movement before hitting the main armored deck, compensating (in some way) the presence of the 12 ER mm deck in between... :think:


Bye, Alberto
"It takes three years to build a ship; it takes three centuries to build a tradition" (Adm.A.B.Cunningham)

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Re: Richelieu and Jean Bart

Post by alecsandros » Wed Nov 21, 2018 8:59 pm

GiZi wrote:
Tue Nov 20, 2018 4:47 am
Unfortunately I've never seen long range data of dispersion for any of the ships - only that the British noted VV's dispersion to be particularly bad at Gaudo, while the same observations were not present in regards to her long-range shooting at Capo Teulada/Spartivento, or Littorio's fire at either battle of Sirte. The only 'hard' information I have is, at a range of somewhere between 28.5-32.5 km (Bagnasco) or 29.3-36.6 km (O'Hara quoting Campioni), a 3-gun salvo from VV's aft turret produced this spread straddling Manchester;

Image
Many thanks for this photograph - it's the first time that I see it.

Regarding long-range dispersion: Bill Jurens has thorough information concerning this. I seem to remember one of his INRO articles describing a curious phenomenon: battleship battery produces a smaller dispersion at long range (above 30km), then the same battery , fired in the same way, at , say, 25km.

The trouble with uneven powder charges caused big dispersion immediately, but, also, it produces uneven wear of the internal gun barrels, and , as such, caused problems for subsequent firings as well. As Littorios and Venetos guns were not replaced or relined (at least I couldn't find any suggestion that they had been), it is probable that they served the entire war with the same tubes - in effect carrying with them the "marks" of the uneven loads. Various sources suggest that initial muzzle velocity decreases with each shot fired , the average normally used to compound velocity reduction being about 3ft/s (1meter/second) for each shot fired. Hence, with 100 shots fired/gun, the average velocity reduction would be about 300ft/s (100m/s). But , as the average is not representative, each barrel would be unevenly worn... therefore producing different velocities and points of impact.

Thorsten and Delcyros, IIRC, have data about Bismarck class dispersion for 2-gun and 4-gun salvoes, at various ranges , out to 25km. I don't remember the numbers, but in any case the values for 4-gun shots at that range were above 300meters IIRC. For more info, we should see if they can reply as well.



That's very interesting. Which online book? That sounds like a very interesting read. It would certainly explain why her dispersion was so tight - using a single gun from each pair at a time would allow for significantly tighter spreads than what would result from the usual half-turret salvoes - as an example, the Trincomalee firings - the single-gun dispersion being 60% of what it was with half-turrets.
"Operation Torch 1942: The Invasion of French North Africa", by Brian Lane Herder, pg 58
Iowa fired 5 8-gun salvoes in 11 minutes at extreme range against the destroyer Nowaki, 40 rounds total (0.45 salvoes/min, rpgpm is the same I think - every 132 sec). In the same engagement and at similarly long range, New Jersey fired 7 salvoes, mostly 3-gun, over the course of 9 minutes for 18 rounds fired (0.77 salvoes/min, or every 77 seconds). I'm guessing they were all fore guns, so rpgpm would likely be 0.39, or every 154 seconds.
This must be correlated with the time of flight of the 406mm shells, which, at that range, was more then 60 seconds.
After the fall, observation of the columns of water was required, and small gunnery alterations ordered. Only then was the subsequent salvo fired. That's why the rate of fire is so low...

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Re: Richelieu and Jean Bart

Post by dunmunro » Wed Nov 21, 2018 11:25 pm

GiZi wrote:
Tue Nov 20, 2018 4:47 am

Unfortunately I've never seen long range data of dispersion for any of the ships - only that the British noted VV's dispersion to be particularly bad at Gaudo, while the same observations were not present in regards to her long-range shooting at Capo Teulada/Spartivento, or Littorio's fire at either battle of Sirte. The only 'hard' information I have is, at a range of somewhere between 28.5-32.5 km (Bagnasco) or 29.3-36.6 km (O'Hara quoting Campioni), a 3-gun salvo from VV's aft turret produced this spread straddling Manchester;

Image


Can you provide the source for the above photo?

This is from Manchester's report on the action:
At 1214 a further group of cruisers, referred to as Group
B [the 8-inch gun cruisers POLA, GORIZIA and FIUME
plus 4 destroyers] came into sight further to the eastward
by MANCHESTER, at that time, as four cruisers bearing
003° 15 miles distant. At 1216, I received a signal from FO
Force H saying that a Sunderland had reported that no
enemy battleships were present.

At 1220 the enemy of Group A opened fire and at 1221
MANCHESTER engaged the right hand cruiser of this
Group at a range of 21,000 yards and the action became
general. The first enemy salvo fired at MANCHESTER was
exact for range. all the splashes falling within the length of the ship
but about a 100yds clear.
(The watery grave: The life and Death of HMS Manchester)
There is no mention of accurate fire being received from RM battleships and the above shell splashes do not appear to be from 15in shells.

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