Intercepting Force H

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Dave Saxton
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Re: Intercepting Force H

Post by Dave Saxton » Tue Jan 22, 2013 2:55 pm

paul.mercer wrote:Gentlemen,
Two questions. Would not the British carrier have had some scouting aircraft aloft to avoid being surprised and would the twins have attemped to engage if it was Nelson instead of Renown? After all, they ran away from Rodney when she was escorting a convoy
Its depends on the mission and the tactical situation. When commerce raiding far from home you seek to avoid combat if at all possible. But if your mission is to take out an aircraft carrier that changes everything.

Its unlikely that Nelson would be escorting a carrier because of its speed. In that case the carrier may have left the battleship behind as it raced into position.
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Re: Intercepting Force H

Post by dunmunro » Wed Jan 23, 2013 7:59 am

alecsandros wrote:Well, the storm that was ravaging the area made tracking S&G a big problem, and it would be likely that they would show up against force H undetected.

Ark Royal didn't have the speed to outrun them, and the escorts wouldn't have lasted long, especialy if the twins would bring escorts of their own.

Renown was an old battlecruiser with 7" belt, and, granted the urgency of their mission, S&G wouldn't have withdrawn as at Stromvaer [where they were tasked with sinking merchant ships, while avoiding enemy capital ships]
Ark Royal was at least as fast as S&G, having made 31.2 knots at deep displacement on trials, and had additional power in reserve.

Renown had a inclined 9in belt backed by a 2in scarf similar to that on Scharnhorst. If S@G hadn't withdrawn at Stromvaer they would have been pounded by Renown and finished off by the flotilla of destroyers just behind her. Force H consisted of Ark Royal, Renown, Sheffield and 6 H class destroyers.

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Re: Intercepting Force H

Post by alecsandros » Wed Jan 23, 2013 10:05 am

dunmunro wrote:
alecsandros wrote:Well, the storm that was ravaging the area made tracking S&G a big problem, and it would be likely that they would show up against force H undetected.

Ark Royal didn't have the speed to outrun them, and the escorts wouldn't have lasted long, especialy if the twins would bring escorts of their own.

Renown was an old battlecruiser with 7" belt, and, granted the urgency of their mission, S&G wouldn't have withdrawn as at Stromvaer [where they were tasked with sinking merchant ships, while avoiding enemy capital ships]
Ark Royal was at least as fast as S&G, having made 31.2 knots at deep displacement on trials, and had additional power in reserve.

Renown had a inclined 9in belt backed by a 2in scarf similar to that on Scharnhorst. If S@G hadn't withdrawn at Stromvaer they would have been pounded by Renown and finished off by the flotilla of destroyers just behind her. Force H consisted of Ark Royal, Renown, Sheffield and 6 H class destroyers.
S&G were more closer to 32kts on trials. In actual combat (against Glorious), they recorded 31kts.

Ark Royal did 31kts on trials in 1938, but I doubt it could make more than 30kts in May 1941 [because of many factors :D ]

But the difference is marginal nonetheless.
===

At Stromvaer, Scharnhorst had radar malfunctions (only Gneisenau managed to hit Renown), and, as always, some nice turbine problems...

===

Renown had 9" of WW1 vintage armor, protecting only a small portion of the sides. 9" of WW1 armor was probably equivalent to 8" of WW2 armor.
German 28.3cm L4.4 performance against oblique surfaces was comparable to that of the German 38cm L4.4 (they were shells of the same family)

On the other hand, S&G vitals were imune against 15" guns at any range below 22km, except some possible underwatrer trajectories.

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Re: Intercepting Force H

Post by dunmunro » Wed Jan 23, 2013 7:42 pm

alecsandros wrote:
dunmunro wrote:
alecsandros wrote:Well, the storm that was ravaging the area made tracking S&G a big problem, and it would be likely that they would show up against force H undetected.

Ark Royal didn't have the speed to outrun them, and the escorts wouldn't have lasted long, especialy if the twins would bring escorts of their own.

Renown was an old battlecruiser with 7" belt, and, granted the urgency of their mission, S&G wouldn't have withdrawn as at Stromvaer [where they were tasked with sinking merchant ships, while avoiding enemy capital ships]
Ark Royal was at least as fast as S&G, having made 31.2 knots at deep displacement on trials, and had additional power in reserve.

Renown had a inclined 9in belt backed by a 2in scarf similar to that on Scharnhorst. If S@G hadn't withdrawn at Stromvaer they would have been pounded by Renown and finished off by the flotilla of destroyers just behind her. Force H consisted of Ark Royal, Renown, Sheffield and 6 H class destroyers.
S&G were more closer to 32kts on trials. In actual combat (against Glorious), they recorded 31kts.

Ark Royal did 31kts on trials in 1938, but I doubt it could make more than 30kts in May 1941 [because of many factors :D ]

But the difference is marginal nonetheless.
===

At Stromvaer, Scharnhorst had radar malfunctions (only Gneisenau managed to hit Renown), and, as always, some nice turbine problems...

===

Renown had 9" of WW1 vintage armor, protecting only a small portion of the sides. 9" of WW1 armor was probably equivalent to 8" of WW2 armor.
German 28.3cm L4.4 performance against oblique surfaces was comparable to that of the German 38cm L4.4 (they were shells of the same family)

On the other hand, S&G vitals were imune against 15" guns at any range below 22km, except some possible underwatrer trajectories.

Scharnhorst made 31.65 knots on trials while Gneisenau made 30.7 knots at 160,050 shp; both at unknown displacements. The output-speed curve for Scharnhorst predicts 31 knots at 160k shp at 39000 tons. Against Glorious, Scharnhorst made 30 knots briefly, than burst a boiler tube and her speed fell below 28 knots.

Renown's belt armour was renewed in 1926, and was of post war manufacture.

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Re: Intercepting Force H

Post by RNfanDan » Wed Jan 23, 2013 7:53 pm

Hey, no fair! Introducing correct facts into a "hypothetical" discussion ruins the whole "Axis Rules!" fantasy.

I strenuously object!! :whistle:
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Re: Intercepting Force H

Post by alecsandros » Thu Jan 24, 2013 6:17 am

dunmunro wrote:
Scharnhorst made 31.65 knots on trials while Gneisenau made 30.7 knots at 160,050 shp; both at unknown displacements. The output-speed curve for Scharnhorst predicts 31 knots at 160k shp at 39000 tons. Against Glorious, Scharnhorst made 30 knots briefly, than burst a boiler tube and her speed fell below 28 knots.

Renown's belt armour was renewed in 1926, and was of post war manufacture.
Scharnhorst obtained 31kts against Glorious, and Gneisenau 32kts.

The 39000 tons displacement was the maximum possible displacement for those ships (and I don't know any situation when they carried that load. The ships were wet enough at 36000 tons load, so putting an extra 3000 tons would reduce freeboard even more). Usual load was around 35-37000 tons. What would the power curve predict at 160k shp and 35000 tons ?

According to Nathan's papers, British CA armor improved significantly after 1930, with KGV main belt having a quality factor of 1.0, while preceding, Krupp-derived British armors, varied around .80 and .92

It was a thin strip of 9" armor on Renown, most the the main belt being actualy thinner than that.

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Re: Intercepting Force H

Post by dunmunro » Thu Jan 24, 2013 10:40 pm

alecsandros wrote:
dunmunro wrote:
Scharnhorst made 31.65 knots on trials while Gneisenau made 30.7 knots at 160,050 shp; both at unknown displacements. The output-speed curve for Scharnhorst predicts 31 knots at 160k shp at 39000 tons. Against Glorious, Scharnhorst made 30 knots briefly, than burst a boiler tube and her speed fell below 28 knots.

Renown's belt armour was renewed in 1926, and was of post war manufacture.
Scharnhorst obtained 31kts against Glorious, and Gneisenau 32kts.

The 39000 tons displacement was the maximum possible displacement for those ships (and I don't know any situation when they carried that load. The ships were wet enough at 36000 tons load, so putting an extra 3000 tons would reduce freeboard even more). Usual load was around 35-37000 tons. What would the power curve predict at 160k shp and 35000 tons ?

According to Nathan's papers, British CA armor improved significantly after 1930, with KGV main belt having a quality factor of 1.0, while preceding, Krupp-derived British armors, varied around .80 and .92

It was a thin strip of 9" armor on Renown, most the the main belt being actualy thinner than that.
Renown's main belt was of a uniform 9" thickness, only tapering at the very bottom edge.

Koop in Battleships of the Scharnhorst class, quotes from Scharnhorst's war diary and the maximum speed recorded was 30 knots, and then the boiler failure occurred.

Given the liquid loading required for her TDS, it is unlikely that S&G could operate at less than 37000 tonnes, which might give another ~.5 knots. Full load with full fuel was 39643 tonnes. However, we would have to make the same calculations for Ark Royal and Renown:

Ark Royal made 31.2 knots at deep displacement (27500 tons) with 103,000 shp ( no overload power). Full overload = ??.? knots. (my guess is ~32 knots at ~125000shp)
Renown made 30.1 knots at 34800 tons (full load = ~ 36500-37000 tons in 1941) with ~120,000 shp (no overload). One book on Renown states that she developed 160,000 shp and 32 knots when using full overload power in 1943.
Scharnhorst made 29.9 knots at unknown displacement with 125,000shp (no overload), 31.65 at 161000 shp (full overload) Power curve states ~31 knots at 160000 shp at 39000 tonnes.
Gneisenau made 28 knots at unknown displacement with 107,500shp (no overload) 30.7 knots with (full overload - G&D state 152000shp)

According to NAaB the difference between WW2 RN CA and post WW1 RN CA at 20k yds with a 28cm gun is about 5%.

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Re: Intercepting Force H

Post by alecsandros » Fri Jan 25, 2013 7:02 am

dunmunro wrote:
Renown's main belt was of a uniform 9" thickness, only tapering at the very bottom edge.
According to GK DOS 100, 9" of KC n/A armor would be vulnerable up to 22km against 28.3cm L54 gunfire.

Of course Renown's armor plates where not of KC n/A quality.

From Nathan's Okun table of metallurgical propeties,

"GERMAN THICK-PLATE IMPROVED KRUPP CEMENTED 'NEW TYPE' (KC n/A)
ARMOR QUALITY: Q=0.96 and QD=Q BLT: 59 TC=N CW=N SS=1"

"AVERAGE BRITISH WWI-ERA KC-TYPE ARMOR:
1919-1930:. . . . . . . . . . . . . . . . ARMOR QUALITY: Q=0.900 and QD=Q BLT: 65 TC=N CW=N SS=2"


Variance: 6.66%

=> Renown belt armor would be vulnerable up to 23,5km, assuming perfectly parrallel courses.
Koop in Battleships of the Scharnhorst class, quotes from Scharnhorst's war diary and the maximum speed recorded was 30 knots, and then the boiler failure occurred.
John Asmussen's analysis, drawing from primary German and British documents, states:
"At 17:27, Gneisenau opened fire against Ardent that was hit on the Nr. 1 Boiler room by the first salvo, speed got reduced on Ardent that started zig-zag in her own smoke while shooting her 4,7 inch (120 mm) guns.

At 17:28, speed on Scharnhorst was 29 knots.

Ardent kept on zig-zag turns and reacted to German shots firing her first salvo of torpedoes against the German ships, one of which was seen to pass close ahead of the Scharnhorst

At 17:34, on board Glorious first group of Swordfish was now on the main deck and getting ready to be launched, armed with torpedoes.

At 17:35, signal "P" received, course now 170°.

Scharnhorst's second salvo went too far over Glorious.

At 17:36, speed was 29 knots on board Scharnhorst. Gneisenau was making already 30,5 knots.

Fire was continuing with main and secondary artillery against the British ships.

At 17:38, speed was 30 knots on board Scharnhorst.
Gneisenau kept on speeding up at more than 32 knots moving in the wake of Scharnhorst moving from port side to the wake of the leading German battleship.
The first hit from Scharnhorst with her third salvo reached Glorious from 24.175 meters (26.450 yards), which is the longest gunfire hit on any enemy warship ever achieved.
The 280 mm (11 inch) shell penetrated the flightdeck and burst into the upper hangar starting a big fire, in the middle of the deck a big hole made it impossible to launch any other aircraft.
All the aircraft present on the main deck were seen falling over board (presumably the 2 Swordfish that reached the main deck earlier).
Splinters pierced a boiler casing and smoke entered air intakes. This caused a temporary drop in steam pressure from 2 boilers, but steam was built up again as the smoke cleared.
Gneisenau turned to starboard at full speed.
At 17:43, Gneisenau was moving fast crossing Scharnhorst wake.
At 17:44, Gneisenau was now sailing on Scharnhorst's starboard side at faster speed.
Scharnhorst Chief Engineer reported an engine room out of service, speed was decreasing.
At 18:02, Scharnhorst was making 27 knots. The ship was having engine problems, boiler 1.1 out, probably due to split tube."
Given the liquid loading required for her TDS, it is unlikely that S&G could operate at less than 37000 tonnes, which might give another ~.5 knots. Full load with full fuel was 39643 tonnes.
The "39643 tons" figure was a 1943 displacement, after wartime modifications.
In 1940, maximum load for Scharnhorst class was about 37.600 tons, and I haven't seen any indication of a single time when they actualy carried even that kind of a load
However, we would have to make the same calculations for Ark Royal and Renown:

Ark Royal made 31.2 knots at deep displacement (27500 tons) with 103,000 shp ( no overload power). Full overload = ??.? knots. (my guess is ~32 knots at ~125000shp)
Renown made 30.1 knots at 34800 tons (full load = ~ 36500-37000 tons in 1941) with ~120,000 shp (no overload). One book on Renown states that she developed 160,000 shp and 32 knots when using full overload power in 1943.
We can make all the calculations you want,

fact is Renown made 29kts max at Stromvaer, and was gradualy left behind by the raiders, demonstrating quite clearly which was the faster ship class.

Ark Royal was tested in 1938, and in the 3 years passing until her demise, the bottom fouling and machinery wear would take it's toll.

On the other hand, S&G demonstrated 31-32+ kts speeds in 1940 and 1941, so they were actualy capable of those speeds.

Moreover, the infamouse North Cape chase shows Scharnhorst at a 3-4kts advantage from Duke of York. Given DoY was the larger ship, I would expect it to behave better in heavy seas, so the speed reduction should have been smaller for her than for Schar.
Alas, even considering similar speed reductions, the situation showed again Schar capable of at least 31-32kts speeds.

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Re: Intercepting Force H

Post by Dresden » Fri Jan 25, 2013 10:44 am

dunmunro wrote: Renown had a inclined 9in belt backed by a 2in scarf similar to that on Scharnhorst.
Krupp pre-war tests give just under 9" of penetration at 20km. This is with RPC/32 propellant against Krupp KC armor inclined at 70 degrees obliquity. During the was, however, the Twins used the more powerful RPC/38 propellant. Renown's Scarp is 50mm at about 45-degrees; Scharnhorst's is 105mm at about 20 degrees from horizontal. I don't think these can be called similar in any way save that both ships have scarps.
The Twins' guns also have a 10km range advantage.

dunmunro wrote: Ark Royal was at least as fast as S&G, having made 31.2 knots at deep displacement on trials, and had additional power in reserve.
The speed difference is minimal. One nautical mile is 1852 meters, so if Ark Royal is, say 2 knots faster that means in a stern chase she can open the range only 3700m in one hour.

But back to one of my main points: S&G do NOT have to sink Ark Royal, or renown, or any other Force H ship, but only delay Ark Royal one hour or so. Since the fatal attack to Bis occurred in near-darkness, one hours delay then provides I expect total darkness and no way to attack. Really, all the Twins have to do is scare Force H, then either head back to port or go join Bis. Even if they open fire they don't need to hit anything. Its kinda like driving cattle or herding sheep. (Cattle and sheep with nasty bites, though.) Heck, if Somerville knows they've even put to sea that alone might be enough.

One possible variable very much in favor of Force H is if Ark Royal already has her Swordfish armed and ready to launch and with a favorable wind direction. Even then, she'll have to maintain course into the wind to launch, which makes a gunnery solution easier than if she just tries to run and shell-chase.

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Re: Intercepting Force H

Post by alecsandros » Fri Jan 25, 2013 11:58 am

Dresden wrote:
dunmunro wrote:
The speed difference is minimal. One nautical mile is 1852 meters, so if Ark Royal is, say 2 knots faster that means in a stern chase she can open the range only 3700m in one hour.
Where is this from ?

Gneisenau went over 32kts, and Schar was capable of 31-32kts. They were both repaired and mantained in 1940, while Ark Royal was not. Moreover, the carrier received extra radars, AA guns, and extra crew until 1941, thus adding several hundred tons of displacement.

Thus, it's hard to imagine Ark Royal obtaining 31kts in May 1941.

[Remember Hood was rated at 32kts, but only went at 29kts+ at Denmark Strait]

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Re: Intercepting Force H

Post by Thorsten Wahl » Fri Jan 25, 2013 12:33 pm

dunmunro wrote: Renown had a inclined 9in belt backed by a 2in scarf similar to that on Scharnhorst.
this is not so. You may live with the explanation the "Unterlagen zur Bestimmung der Hauptkampfentfernung" gives.

"The strongest armored deck therefore has to be lay as deep as possible with a flat slope as possible to the lower edge of the main belt, but, unlike previously, now so strong that even projectiles, wich penetrates the belt with a significant surplus of speed and hit the slope, can not penetrate, but get breaked or dismissed."

The scarp at Renown was probably not sufficiently laid back that much and was also not thick enough, to cause the projectile failures as described.
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Re: Intercepting Force H

Post by Dresden » Fri Jan 25, 2013 5:28 pm

alecsandros wrote:Where is this from ?
Just pointing out that even if Ark Royal was faster it was not enough to make any reasonable difference.

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Re: Intercepting Force H

Post by dunmunro » Fri Jan 25, 2013 9:09 pm

Ark Royal only added two 8 barrelled pom-poms during her time in service - no radars were ever fitted. She was last docked in Nov 1940, but AFAIK her machinery was in good shape, however S&G had machinery problems constantly - every time they tried to use overload power.

Renown was outrun at Stromvaer because she suffered damage to her forward bulge, which had partially torn away in the heavy seas, and because she couldn't obtain ranges for her forward armament at such high speeds in the prevailing seas, so there was no point in trying for more speed. OTOH both S&G lost all their forward armament due to flooding. If they had found Glorious, in heavy seas, they probably wouldn't have been able to pursue her anyways, since they wouldn't be able to work their forward guns.

By maintaining a 30 deg inclination (very typical in combat and easy to do with an inclined belt), Renown has an immune zone from 28cm guns from about 11,000 yards or less:

Image
broken shells will be rejected by her scarf armour. Both the belt and scarf armour are backed by about 1in of HT steel. Here's the scarf (main deck slope thickness's: main deck (slope) : 4inch (2inch NCD + 1inch HT + 1 inch HT) over magazines, 3 inch and 1inch (1+1+1 or 1 inch HT) over machinery. So Renown was practically immune from the 28cm gun, through her main belt, at 30 deg target inclination.

KM practise was to run trials with full overload power - so there is no way that KM ships can move faster then their trials speeds - 32 knots for S&G is fantasy. G made 30.7 knots on trials with full overload power and she will only be slower in service. Here's a weight breakdown:

http://www.schlachtschiff.com/kriegsmar ... emein.html

note that with only 4900 tons of fuel that displacement is 38443 tons; full fuel = 6500 tonnes and max displacement is therefore about 40,000 tonnes. These ships used so much fuel that it is unlikely that they would a foray into the Atlantic without full tanks and that is why they had such a reputation as wet ships, they were constantly overloaded beyond their design displacements.
Last edited by dunmunro on Fri Jan 25, 2013 10:01 pm, edited 1 time in total.

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Re: Intercepting Force H

Post by Dresden » Fri Jan 25, 2013 9:56 pm

But the target of the twins isn't Renown, but Ark Royal. And, again, all that's required is about an hour's delay.

If both twins are present, Renown can only chase one.

If only one of the Twins is present, she has some 10km extra gun range to work with and Renown doesn't have enough of a speed advantage to close this distance within an hour or two. Even firing at Ark Royal at extreme range the Twin does not have to hit but only force a course change.

And I'm not sure Gneisenau had the same machinery problems that Scharnhorst did - at least I don't ever recall reading about it. The ships had different machinery manufacturers. Gneisenau's problem was that she was a magnet for British explosives.

Hope the snow's not too deep up there in beautiful BC.

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Re: Intercepting Force H

Post by dunmunro » Fri Jan 25, 2013 10:16 pm

Dresden wrote:But the target of the twins isn't Renown, but Ark Royal. And, again, all that's required is about an hour's delay.

If both twins are present, Renown can only chase one.

If only one of the Twins is present, she has some 10km extra gun range to work with and Renown doesn't have enough of a speed advantage to close this distance within an hour or two. Even firing at Ark Royal at extreme range the Twin does not have to hit but only force a course change.

And I'm not sure Gneisenau had the same machinery problems that Scharnhorst did - at least I don't ever recall reading about it. The ships had different machinery manufacturers. Gneisenau's problem was that she was a magnet for British explosives.

Hope the snow's not too deep up there in beautiful BC.
It's true that a sortie by S&G would have caused problems for Force H and that Bismarck might not have been struck by an Ark Royal launched torpedo, OTOH it is also possible that Sheffield would not have been detached to shadow Bismarck and thus the first strike would still have found it's intended target. But a sortie by the twins to attack Force H, would have been suicidal, and even if it saved Bismarck, it would have doomed S&G which would have left the KM in an even worse position than before.

No snow, here, just lots of rain, although it's clear today.

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