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Dreadnought Battlecruiser Doctrine
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jwduquette1



Joined: 20 Dec 2005
Posts: 90

PostPosted: Sun Apr 16, 2006 9:29 am    Post subject: Reply with quote

He doubtless did leave out information. But it seems unlikely that more heavy shell hits on British Ships is the missing piece of the puzzle. A number of cross source checks confirm the various hit totals on the British Battlecruisers. It also appears that, aside from Meteor, no other British ships received any heavy shell hits.

One would deduce that the missing information could only be that Massie left the German 8.2" shell use totals out of his figures, and that his 3.5% hit ratio for German gunnery is an error. I suppose it makes since that the 8.2" shell expenditure was not indcluded in the German shell count. After all Blucher went down. That sort of information might have gone down with her. The long and short being that it appears the German hit ratio for 11 & 12 inch shell fire is either:

22/976 = 2.25%
or
21/976 = 2.15% (assuming the Meteor hit was by an 8.2" shell)

If we employ a guesstimated shell usage by Blucher of say 150 or 200, than the overal heavy caliber ammunition expenditure was maybe 976 + 200 = 1176 -- 1126. And the hit ratio by the Germans becomes

25/1176 = 2.12%
or
25/1126 = 2.22%
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jwduquette1



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PostPosted: Sun Apr 16, 2006 11:48 am    Post subject: Reply with quote

An aside, but Massie indicates that the RN BC hit ratio at Falklands was about 5%. But even this figure -- at least at the time -- was considered by the RN to be extremely poor gunnery results. High expectations. Massie goes on to indicate that by the end of the war, a 5% hit ratio was considered to be fairly decent shooting.
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tone
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PostPosted: Sun Apr 16, 2006 2:43 pm    Post subject: Reply with quote

Ugh ... Just spent two hours on a spreadsheet and tossed it out. I haven't the attention span to count shots and hits -- much less to try to reconcile disparate sources that may not agree. Heck... it's hard just trying to figure out with certainty which ships had Dreyer tables at Jutland.

The bottom line is that no two salvoes are the same, and any tallying of hits per shot that implicitly ignores the differences in time of day, smoke conditions, and range of any two shots is, I feel, a misguided effort to hide complexity.

My spreadsheet even had the gunlayer scores for the various RN ships from 1913. Upon thinking on it, I realized that gunlaying per se was not a skill being tested at Jutland as they were firing by director and in 1913 they were not doing so.

This is just the sort of over analysis that has already caused many to swear by conclusions built of sand.

tone
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jwduquette1



Joined: 20 Dec 2005
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PostPosted: Sun Apr 16, 2006 5:39 pm    Post subject: Reply with quote

tone wrote:
Ugh ... Just spent two hours on a spreadsheet and tossed it out. I haven't the attention span to count shots and hits -- much less to try to reconcile disparate sources that may not agree. Heck... it's hard just trying to figure out with certainty which ships had Dreyer tables at Jutland.

The bottom line is that no two salvoes are the same, and any tallying of hits per shot that implicitly ignores the differences in time of day, smoke conditions, and range of any two shots is, I feel, a misguided effort to hide complexity.

My spreadsheet even had the gunlayer scores for the various RN ships from 1913. Upon thinking on it, I realized that gunlaying per se was not a skill being tested at Jutland as they were firing by director and in 1913 they were not doing so.

This is just the sort of over analysis that has already caused many to swear by conclusions built of sand.

tone


Totally agree. This is all just internet forum fun and games with the tip of the ice berg.

I was fiddling around with target sizes thinking perhaps there maybe a major disparity between RN Battle Cruisers target footprints and SMS Battle Cruiser target footprints. Siegfried Breyer has a large number of 1:1250 scale drawing presented in his book Battleships and Battle Cruisers, 1905 to 1970”. The common scale throughout made it easy – no scaling required. I simply overlaid the Seydlitz over the top of Lion.

With the exception of a bit of additional freeboard and length on the part of Lion – as well as her much more massive turrets – the size of the ships are not grossly different. This is obviously an extreme over simplification as the hitting space presented by a given ship will be much larger the footprint of the ship itself – depending upon projectile descent angle. But along this same line, I would speculate that the lighter German shells would have had greater descent angles relative to the heavier British shells. In theory this should – assuming the same size target ships – give the British a bit of an advantage as the hitting space presented by the German Ship would be larger as a result of the shallower descent angles of British shells.

Best Regrads
JD


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PostPosted: Sun Apr 16, 2006 7:13 pm    Post subject: Reply with quote

This is an interesting line of inquiry, and I am glad to see you not overblow the larger RN ship size, but it is illuminating to see this evaluated.

Quote:
I would speculate that the lighter German shells would have had greater descent angles relative to the heavier British shells


I think I made the same point once and was proven wrong at a given range. A gross difference in MV at a surprisingly large span of ranges gives a lighter shell a flatter trajectory. It always bears a little checking.

tone
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rubberboot



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PostPosted: Sun Apr 16, 2006 8:16 pm    Post subject: Reply with quote

I've read somewhere (internet site, maybe?) that when the main turrets are fired, that there is a split second delay between the guns in the same turret. I can't remember the reasonning for this, whether it was timed that way or just how it happened due to differences in cordite, but it would jar the turret off one way or the other. If there was enough wear in the turret gears, over 20000 yards, it could throw out the aim. This was primarily a problem with Twin mountings. I believe this article I read was a paper from the USN. With the triple mountings, the centre gun was 'time delayed' to fire last, which helped to alleviate this, as well as reduce the overall shock of the firing. Since all the the guns at Dogger and Jutland were twin mountings, could this have caused some of the poor shooting?

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tone
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PostPosted: Sun Apr 16, 2006 8:44 pm    Post subject: Reply with quote

rubberboot wrote:
I've read somewhere (internet site, maybe?) that when the main turrets are fired, that there is a split second delay between the guns in the same turret. I can't remember the reasonning for this, whether it was timed that way or just how it happened due to differences in cordite, but it would jar the turret off one way or the other. If there was enough wear in the turret gears, over 20000 yards, it could throw out the aim. This was primarily a problem with Twin mountings. I believe this article I read was a paper from the USN. With the triple mountings, the centre gun was 'time delayed' to fire last, which helped to alleviate this, as well as reduce the overall shock of the firing. Since all the the guns at Dogger and Jutland were twin mountings, could this have caused some of the poor shooting?


This feature in at least some USN WW2 ships was intended to minimise aerodynamic interference between sheels in flight (I think the Bernoulli effect would cause two shells flying side by side to be drawn into each other, but don't quote me on that), but I've never found a hint that it was a feature in RN firing circuits.

I could pull the fine Iowa class book I have on the shelf off, but by memory, the firing sequence was left, right, center with perhaps 1/20th of a second between each (or 1/40th?).

But keep in mind -- almost all firing in this era was done in "half salvoes". For ships with double guns, this meant that only one gun would fire in each salvo, and they'd alternate. That is, the Lion (4x2 = 8 guns) would fire at most 4 guns in a salvo, but the salvoes would come at about twice the reload rate. This allowed them to double the spotting opportunities, and doubled the rate at which their target's nerves were jangled. I'm sure the Iowa class mostly operated in modes other than full broadsides, too. In particular, shore bombardment would have benefited from the efficiency of more spotting and few targets deserve a 9 shell drubbing.

I am not sure of the slewing effect an off-center single firing would produce, but other than wear and tear, it is immaterial when only one gun per turret is firing per salvo.


tone
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jwduquette1



Joined: 20 Dec 2005
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PostPosted: Mon Apr 17, 2006 8:56 am    Post subject: Reply with quote

tone wrote:
I think I made the same point once and was proven wrong at a given range. A gross difference in MV at a surprisingly large span of ranges gives a lighter shell a flatter trajectory. It always bears a little checking.

tone


Hi Tony:

I assume Lion would be firing primarily 1250-lbs MkV APC at Dogger Bank. I have the range tables for most RN heavy guns of the period.

I also assume Seydlitz would have been firing primarily 666-lbs APC. Unfortunately I don’t have schußtafeln for 11” APC of this period, but if I have a reasonable estimate of the projectile geometry it is easy enough to back calculate trajectory data and remaining velocity data. I have scale sectionals of both 11” and 12” spgr, and they are basically the same geometry – 11” spgr is of course slightly reduced in size and weight (see attached). I have always thought that 11" SKL/50 APC was simply a reduced size version of 12" SKL/50 APC -- both with about a 4-crh nose. Can you confirm whether or not this is true?

Thanks

Regards
JD


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PostPosted: Mon Apr 17, 2006 10:00 am    Post subject: Reply with quote

I could do a fair estimate on its performance with little data.

My code for this actually grew more sophisticated than my own understanding, but let me try to print out a range table for this german shell.

Let me google a bit to find a MV and an extreme range/elevation pair.

I'd love to have a copy of whatever work this image came from.

tone
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jwduquette1



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PostPosted: Mon Apr 17, 2006 10:48 am    Post subject: Reply with quote

The MV and extreme range launch angles are readily available from a number of sources. I'm more interested in developing a set of ballistic coefficient\s for 28cm APC. But for that I would also need nose geometry to determine a reasonable form factor.

The 30,5cm APC and spgr. images are scanned from Campbell's book on Jutland. The 28cm spgr is from a post-War British investigation into German Army and Naval artillery ammunition. I can't recall the title as I am at work at the moment. Not sure why the British didnt also provide a scale image of 28cm SK L/50 APC in the work. Mostly high explosive -- shrapnel -- chemical. Some Naval AP & APC. I'll send you a cite on the thing when I get home.

Regards
JD
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jwduquette1



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PostPosted: Mon Apr 17, 2006 10:53 am    Post subject: Reply with quote

Sorry -- I think I see what your saying. Set launch angle to max -- than back calculate a form factor that results in the maximum range that should be achieved. Base data From Navweapons:

Range @ 13.5 degrees = 19,790 yards

Range @ 16.0 degrees (maximum elevation after 1915) = 20,890 yards

W = 666 lbs.
Mv = 2,887 fps

I think I can figure out the form factor from this info.
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PostPosted: Mon Apr 17, 2006 10:58 am    Post subject: Reply with quote

I'll plug these in and assume a 4 CRH head (let me knof if this is wrong), and a shell length overall making it proportional to the 30.5 APC shell you show (btw: what is ITS overall length? I can't read it)

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PostPosted: Mon Apr 17, 2006 1:24 pm    Post subject: Reply with quote

Ok .. here is some synthetic data comparison between Lion's CPC and Seydlitz's APC (if that is what you were describing). Let me know if you see bad inputs, and read a bit on the "process" page linked to these to see more about the code that generated them.

Lion's Light 13.5" Shell (I also have the historical table for this)

JW's shell and gun in UK unit printout


JW's shell and gun in an untested, more metricky unit printout

I assumed 4CRH head and a overall length similar in proportion to the 305mm shell you showed (based on rough measurement as I could not read its dimensions).

I could tweak this further if you have reason to suspect I'm totally off.

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jwduquette1



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PostPosted: Mon Apr 17, 2006 2:14 pm    Post subject: Reply with quote

Kewl.

I am sort of swamped with work at the moment (yet still find time to check back to this forum -- go figure). I want to look at your numbers a bit closer this evening. My only comment at this point is I was assuming 13.5" APC. There is a note on the 1918 Range Tables that indicates APC MkIa ranges further than CPC MkIa by an amount equal to an increase of 4% over the CPC ballistic coefficient. Probably wont make a huge difference in decent angle, but I can't be sure untill I check the numbers.
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jwduquette1



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PostPosted: Tue Apr 18, 2006 8:52 am    Post subject: Reply with quote

The 28cm spgr image is from: “Notes on German Shells, 2nd Edition, 1918”.

The exterior ballistics problem is a bit of a head scratcher. I am getting two different BCs. One for the 13.5-degree launch angle, and a different one for the 16-degrees launch angle.

To get the trajectory to match the level line at 19790-yrds I need to use a BC = 8.284 -- so i=0.6476.

However if I use the same BC with a 16.5-degree launch angle I get the trajectory crossing the level line at about 21410-yrds. This is a bit further than the NavWeapon web sites quote figure of 20890-yrds.

I'm using an Ingals Drag function, and US Army Standard Atmospherics. Are you aware of what standard conditions were employed by the Germans during this period?
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