Efficiency of the U-boat fleet

[Raesene]

That's interesting, do you have any more information about the cost and time period of her refit, as well as how much additional armor was added? I always thought improving deck armor would be hugely impractical.

As the reconstruction in the late 1930s removed the whole bridge structure and 15'' turrets, access might have been easier. I'm always wondering about how to change change damaged amour plates somewhere in the ship myself if the ship has to be back in service soon.

[...]
(General remarks to the gunery fit as designed/entering service during WW1)
The 15in guns were the standard Mk I with 20° elevation, 120rpg. But the secondary armament was unique in that the proven 6in gun previously regarded as essential for stopping modern torpedo-craft was discarded in favour of 4in calibre guns, and casemate mountings were abandoned for shielded pedestal mountings. These guns were the BL Mk IX, fifteen of which were shipped in triple mountings TI Mk I to give a good volume of fire, with two single mountings on 'B' shelter deck. The triple mounting did not prove a success, being clumsy and crowded to operate. Two 3in AA were fitted abreast the after funnel. Two single submerged 21in torpedo tubes were carried in the torpedo flat forward of 'A' barbette and ten torpedoes were shipped. This too was an unsuccessful arrangement. Fisher's demands for a minelaying capability were dropped after design difficulties arose.

[...]
(Renown's smaller scale refits and changes)
Renown had a major refit from July 1923 to September 1926 when the main 6in belt was replaced by 9in armour which was carried rather higher than that in Repulse because Renown's wartime additions had more greatly increased the draught. Part of this 9in belt came from plates rolled for the Chilean Almirante Cochrane, taken over by Great Britain and completing as a carrier. Below the new main belt the space between it and the amour shelf was filled by a strake 9in thick at the top, tapering to 2in at the bottom. This new side armour weighed 1,505 tons, but the 6in belt was not refitted above the new armour belt, thus saving 896 tons. NC armour, 2in thick, was added to the main deck above the magazines on the flat and slopes, and 4in armour was added horizontally from the edge of the flat of the main deck abreast the magazines to within 2 feet of the ship's side. Armour of 1.5in thickness was added to the main deck over the boiler rooms, and 2.5in armour was fitted horizontally from the edge of the main deck to the ship's side in the way of the boiler and engine rooms. Extra plating was also added to the lower deck forward (3in) and aft (l.5in) to improve magazine protection. She was given bulges of a new type.

The only alterations made to the armament were the replacement of the 3in HA by 4in and two extra 4in singles added.

In 1931-2 Renown was given HACS Mk I in the foretop, and was equipped for two eight-barrelled 2pdrs, but only one (starboard) was fitted. In 1933 she was fitted with an athwartships catapult, the midships triple 4in being landed. The second 2pdr mounting was received at about this time, and two quadruple 0.5in MGs were fitted.

(Major reconstruction)
In September 1936 Renown was again taken in hand, this time for major reconstruction. The existing tiered bridge structure was removed and replaced by a block bridge on the lines of that in Warspite, The protection scheme was not altered in any major way, 4in being added over the new 4.5in magazines and 2in over the engine rooms. Over the boiler rooms the thickness of the flat portion was made uniform, and 2in armour was fitted to the lower deck forward and 2.5-3in to the lower deck aft. The sides of 'A' and 'B' barbettes were increased respectively from 4in to 6in.

The old machinery was replaced by eight Admiralty 3-drum boilers in four boiler rooms, and Parsons geared turbines with a designed output of 120,000shp for a maximum speed of 29 knots. The new funnels were slightly farther aft than previously. The 15in turrets were taken out to be modified, increasing elevation to 30°. All the secondary armament was landed, being replaced by twenty 4.5in Mk I in twin BD mountings MK II. These were on shelter decks, with three mountings abreast the fore funnel and two abreast the mainmast. A third eight-barrelled 2pdr was added aft, above 'Y' turret on the shelter deck. A new director tower for the 15in was fitted above the bridge and the old one was resited aft. Four HACS Mk IV provided control for the 4.5in battery. The submerged tubes were replaced by eight above-water tubes.
[...]

(italicisation (is that even a word? ) and remarks in brackets added by me.)

Regarding the (secondary) guns, Renown was assigned to Force H at Gibraltar, Valiant and Queen Elizabeth joined Cunningham's Mediterranean Fleet at Alexandria, where they could be expected to endure severe axis air attacks. I have a book somewhere about the Crete campaign commenting that their AA-armament was considered the best in the fleet, hence the disposition (at least I think teh remark was in that book).

By the way, I really recommend the site I quoted. There's a lot of data (and pictures and stories) about cruisers and battleships of WW2.

[Raesene]

To add to my prevous post: Prior improvements to the protective scheme of Repulse, Royal Oak and Malaya had led to lower speed and reduced stability due to the increased weight. It emerged that a major, expensive (no numbers, I'm afraid) reconstruction was required to achieve a satisfactory result.

Warspite, Renown, Queen Elisabeth and Valiant were thus rebuilt extensively, similar proposals existed for Hood, Nelson and Rodney. Revenge was planned to be rebuild like Warspite starting in 1936, but that proposal wasn't approved.
The outbreak of the war made the reconstruction any further capital ships taking years impossible.

Durations:
Repulse: 1933-1936
Malaya: 1934-1936
Warspite: rebuilt 1934-1937
Renown: rebuilt 1936-1939
Queen Elisabeth and Valiant: rebuilt 1937-1941

[Sea Skimmer]

That's interesting, do you have any more information about the cost and time period of her refit, as well as how much additional armor was added? I always thought improving deck armor would be hugely impractical.

Renown got entirely new machinery which saved 2,800 tons of weight. That's why she could receive a significant deck armor improvement without being blistered to restore freeboard and losing speed. Her rebuild cost £3,088,000. This was close to half the price of an entirely new battleship. The work took from September 1936 to September 1939, nearly as long as building a new ship too.

Most nations battleships received some level of deck armor increase between the wars. In the RNs case the modernizations cost anything from about £500,000-2.3 million for Warspite which had the next most elaborate upgrade package after Renown. All and all such upgrades could provide very useful protective increases, but the high end rebuilds got expensive very fast and only really made sense because of the treaty system.

[Simon_Jester]

On the subject of refits to capital ships:

I suspect that some of the naval-oriented posters here are already familiar with "Operation Catherine:" Churchill's proposal to refit the R-class battleships as... the best term I can come up with is "supermonitors." He proposed to remove two of the twin 15" gun turrets, put on additional torpedo protection and deck armor, and slap a large AA battery on them. He thought this would make them safe enough from air attack to operate close to shore in the face of hostile land based air power.

Now, I assume that this was a stupid idea, because of the cost, the fact that he didn't suggest it until 1939 by which point it was far too late to make major refits, and the fact that it wouldn't have made the ships immune enough to air attack to be very safe.

Am I correct in assuming this?

[PainRack]

Another question regarding refits, the Renown/Hood refits caused them to be reclassified as Fast battleships. How accurate was this designation in terms of its armour, firepower and etc？

[Sea Skimmer]

Am I correct in assuming this?

Yup. The rebuilt R class were to be used as part of a Baltic invasion plan, which Churchill thought up because he was far too blind to have learned a thing from the Gallipoli disaster. They would have gained 4-5in of deck armor, and had a beam of 140ft with no more then 14 knot speed flooded down for combat. So sinking them would not be easy, but any ship will be quickly put out of action by repeated bomb hits.

The Luftwaffe didn’t have any really heavy anti ship bombs (as in nearly nothing over 250kg and nothing over 500kg at all) until 1941 so that would have made it hard to actually sink any decently armored battleship. They also didn’t have an aerial torpedo until 1940 when they bought them from the Italians. Course the Germans also had lots of mines, U-boats, motor torpedo boats and other weapons which would make life hell for any major ship in the Baltic.

Bad plan all and all, but Churchill like many other people figured the western front would be static again, and that such schemes would have time to play out to win the war by peripheral means.

[atg]

Another question regarding refits, the Renown/Hood refits caused them to be reclassified as Fast battleships. How accurate was this designation in terms of its armour, firepower and etc？

IIRC in terms of weight of armour Hood had more than any other ship afloat when she sunk. Certainly more than enough to be Battleship level protection. Just the layout/distribution sucked.

[Sea Skimmer]

http://www.ibiblio.org/hyperwar/USN/rep ... 201941.pdf

Since it’s relevant to general discussions of sea power in WW2, the above is an official USN report on British information on ships sunk or damaged by aircraft bombing up until September 1941. This includes the Battle for Crete. File is about 1.9 megs.

[Simon_Jester]

Yup. The rebuilt R class were to be used as part of a Baltic invasion plan, which Churchill thought up because he was far too blind to have learned a thing from the Gallipoli disaster. They would have gained 4-5in of deck armor, and had a beam of 140ft with no more then 14 knot speed flooded down for combat. So sinking them would not be easy, but any ship will be quickly put out of action by repeated bomb hits.

The Luftwaffe didn’t have any really heavy anti ship bombs (as in nearly nothing over 250kg and nothing over 500kg at all) until 1941 so that would have made it hard to actually sink any decently armored battleship. They also didn’t have an aerial torpedo until 1940 when they bought them from the Italians. Course the Germans also had lots of mines, U-boats, motor torpedo boats and other weapons which would make life hell for any major ship in the Baltic.

Bad plan all and all, but Churchill like many other people figured the western front would be static again, and that such schemes would have time to play out to win the war by peripheral means.

Sort of like Cultivator No. 6, then?

Looking at some of the stuff Churchill came up with is a great reaffirmation of Sturgeon's Revelation: ninety percent of everything is crud, especially with a guy like him around. I'm inclined to forgive him on the grounds that a few of the ideas that weren't crud turned out to be real gems, but that's just me.

[JBG]

Another question regarding refits, the Renown/Hood refits caused them to be reclassified as Fast battleships. How accurate was this designation in terms of its armour, firepower and etc？

IIRC in terms of weight of armour Hood had more than any other ship afloat when she sunk. Certainly more than enough to be Battleship level protection. Just the layout/distribution sucked.

I've never heard of Renown being reputably referred to as anything other than a BC. Which she was. The again I recall a newspaper article I read recently referring to a light cruiser as a BB!

The Admiralty class were always to be, in the sense of the times, super BCs but you are right. Hood did have BB levels of protection but there was a known flaw in the armour scheme which was to be remedied in a rebuild/modernisation that they never got around to and it seems that the projectile that did Hood in exploited that very weakness.

On another point, wasn't Barham also modernised? She certainly met her fate with 4.5" secondaries.

[Sea Skimmer]

Barham had a major refit in 1931, her AA armament was increased to four single 4in guns, replaced by twins by wartime, and post Jutland armor additions were removed. In their place she had new 4in thick armor plates laid on top of the original 1in thick armor deck over the magazines. Machinery armor remained as thin as ever. She was bulged to partly restore freeboard and improve torpedo protection.

Barham never had 4.5in guns. She exploded in fact because extra 4in AA ammunition had been stacked outside the main magazines as emergency storage space, leaving it very exposed to torpedo hits. This was because only the main magazine areas had proper deck protection.

[PainRack]

I've never heard of Renown being reputably referred to as anything other than a BC. Which she was. The again I recall a newspaper article I read recently referring to a light cruiser as a BB!

It was the budgetary proposal for the last refit for the Repulse/Renown, giving them improved AA and stuff. I'm not so sure whether Hood twist into a Fast battleship was a news reporting agenda however or a budgetary move.

[Iosef Cross]

On another forum, someone mentioned that the recources spent on the larger ships of the German surface fleet, would have been more usefull when spent on building more U-boats instead. While I certainly agree with the first part, wouldn't it have been more usefull to divert those recources in the Luftwaffe and/or Wehrmach rather than building more U-Boats? As far as I know, U-boats were only efficient for a short period during the war but I might be mistaken.

So, which would give the most bang for buck? More U-boats or more land/airforce?

Second to this article:
http://www.navy.mil/navydata/cno/n87/hi ... aigns.html
Submarine warfare was very efficient:

"Appendix 1 specifies how the costs were calculated. As a result, I have estimated that the Allies spent (countering the U-boats) nearly 10 times what the Germans spent on their U-boat fleet. One should note that German submarine industry employed between 30,000 and 45,000 workers.(45) However, the Americans alone employed 640,000 workers at peak just to construct merchant ships during the war.(46) Thus, my calculation probably substantially underestimates the Allied effort during the war."

The Germans could make around 25 submarines per month, and they had only 57 at the start of the war. So yes, they should have made several times more during the pre and early years of ww2.

[K. A. Pital]

On another forum, someone mentioned that the recources spent on the larger ships of the German surface fleet, would have been more usefull when spent on building more U-boats instead. While I certainly agree with the first part, wouldn't it have been more usefull to divert those recources in the Luftwaffe and/or Wehrmach rather than building more U-Boats? As far as I know, U-boats were only efficient for a short period during the war but I might be mistaken.

So, which would give the most bang for buck? More U-boats or more land/airforce?

Second to this article:
http://www.navy.mil/navydata/cno/n87/hi ... aigns.html
Submarine warfare was very efficient:

"Appendix 1 specifies how the costs were calculated. As a result, I have estimated that the Allies spent (countering the U-boats) nearly 10 times what the Germans spent on their U-boat fleet. One should note that German submarine industry employed between 30,000 and 45,000 workers.(45) However, the Americans alone employed 640,000 workers at peak just to construct merchant ships during the war.(46) Thus, my calculation probably substantially underestimates the Allied effort during the war."

The Germans could make around 25 submarines per month, and they had only 57 at the start of the war. So yes, they should have made several times more during the pre and early years of ww2.

Oh, yes, THAT article.

Which measures efficiency by absolute numbers of cargo destroyed as opposed to reaching strategic goals. Here's a hint - if you only destroy ~1% (offhand quote by Blair) of the Allied shipping sent, it's a failure. No matter how much you destroyed in absolute numbers, no matter how much you destroyed relative to your own costs incurred.

The sumbarines were cost-efficient, but they were not strategically or tactically efficient.

[PeZook]

Furthermore, after a certain escort saturation was reached, the U-Boat fleet became completely ineffective. Therefore, each dollar spent on new subs at that time had no effect other than forcing the continuation of the convoy system, while the Allies could maintain their iron grip on the Atlantic by simply replacing munitions and damaged platforms.

Also, the author of that article makes a few unfounded assumptions:

2. It is assumed that 50% of destroyed ships had cargoes and I have estimated the value of each cargo as equivalent to the price of the ship.(98)

Data is available on the amount of loaded vs. unloaded ships sunk ; Also, the assumption that every cargo load was equivalent in price to the price of the ship is completely ridiculous, and probably massively distorts the cost.

6. It is assumed that 33% of the total merchant fleet was lost due to inefficiency of convoying. That is 11.36 million tons at $420/ton.(103)

Why does he attribute equal costs to shipping lost due to inefficiency of convoying and that lost due to enemy action?

He also doesn't take rented and seized ships into account: those have a much lower cost per ton of capacity than newly built ones.

His calculations of the German cost of the submarine war are off, too: he only takes into account the cost of building the boats themselves, without munitions and facilities necessary to support them. What would've happened if Germany magically got 300 Type XXI U-boats in 1944?

Nothing, because they'd have no bases and no torpedoes for them. Remember, the torpedo was the most expensive naval weapon system of the war per round expended, and accuracy was rather low: U-Boats would often launch 4-6 torpedoes to hit a single merchant.

[K. A. Pital]

Yeah, that got me thinking too - he forgot to mention the "cost" of the nameless soldier who died to take Lorient. That way, the cost to the enemy to defeat the U-boat "menace" rises again! How devious!

[Iosef Cross]

Which measures efficiency by absolute numbers of cargo destroyed as opposed to reaching strategic goals. Here's a hint - if you only destroy ~1% (offhand quote by Blair) of the Allied shipping sent, it's a failure. No matter how much you destroyed in absolute numbers, no matter how much you destroyed relative to your own costs incurred.

The sumbarines were cost-efficient, but they were not strategically or tactically efficient.

Well, if even with 10 times the cost efficiency, you cannot achieve your strategic objectives, that means that you were fighting against impossible odds, so any strategy would be useless and "strategically or tactically inefficient" in this case. With makes your definition of "strategic or tactical" efficiency useless.

Also, the 1% number is the death rate for 1 voyage, not the proportion of merchant shipping that the allies had lost to submarines. In 1942, the allies lost 8 million tons of merchant shipping, most of it to submarines, while Britain had 16 million tons of shipping at the start of the war. Losses against the u boats were very high and surpassed allied production until may 1943.

[PeZook]

First of all, what counts is the amount of cargo deliveries prevented, not the sheer amount of sunk tonnage.

Even then, though...

Overall Allied losses amounted to about 2900 ships and circa 15 million BRT. Total merchant ship production was 34 million tonnes, Britain started the war with 21 million. So, not counting the United States (I don't have the data on their fleet on hand), the U-Boats managed to sink 27% of all tonnage, yet less than 1% of the cargo.

Any other claims of extraordinary efficiency?