Quick mods to the Courageous class

Denniss said:

In short: C&G hulls were at their limits, a larger flight deck could only be achieved with massive investments in money and time. The timespot for this work was missed in late 1930s and in wartime they couldn't afford rebuilding them.

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Good points. I think just by having them Courageous and Glorious survive into 1941 would have been impactful even without modifications. But if we're not doing mods we're best to return to this thread Better luck for the RN carrier force 1939-1941

Could they operate the larger FAA aircraft without mods? Those catapults were designed a long time before aircraft of the Tarpon's weight were conceived of.

Admiral Beez said:

Good points. I think just by having them Courageous and Glorious survive into 1941 would have been impactful even without modifications. Could they operate the larger FAA aircraft without mods? Those catapults were designed a long time before aircraft of the Tarpon's weight were conceived of.

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The BH.I accelerators on C&G, Ark and Argus were uprated from 1938 to launch 12,000lb at 56 knots using the trolley launch method.

So they could handle Albacores, but would have to be uprated further to handle the Barracuda and Avenger which both entered FAA service in early 1943. But they would also need modified for tail down launching of US types. Investigation of tail down launching at the RAE began in mid-1942 after US built escort carriers arrived in the U.K. The later BH.III on the Illustrious class were modified for that around late 1943 / early 1944.

EwenS said:

The BH.I accelerators on C&G, Ark and Argus were uprated from 1938 to launch 12,000lb at 56 knots using the trolley launch method.

So they could handle Albacores, but would have to be uprated further to handle the Barracuda and Avenger which both entered FAA service in early 1943. But they would also need modified for tail down launching of US types. Investigation of tail down launching at the RAE began in mid-1942 after US built escort carriers arrived in the U.K. The later BH.III on the Illustrious class were modified for that around late 1943 / early 1944.

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You reminded me of these poor Seafires going to waste postwar.

Admiral Beez said:

You reminded me of these poor Seafires going to waste postwar.

https://external-preview.redd.it/p4x7Z3Bdcz5H-JRjiLiySvGFCM2IjX_Fo-JAhBSqV1s.gif?format=mp4&s=df0809079ea485356a914b2085f32276ff69b534

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Why going to waste? They were a valuable part of testing the very first steam catapult on Perseus from 1950-52 which is where this film was taken. Note the catapult is located on top of the flight deck.

EwenS said:

Why going to waste? They were a valuable part of testing the very first steam catapult on Perseus from 1950-52 which is where this film was taken. Note the catapult is located on top of the flight deck.

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I know, it was a fine use at the time. I only meant that as artifacts and museum pieces today they are highly prized.

I just want to say how much I appreciate the knowledge and detail E EwenS brings to these conversations.

Thumpalumpacus said:

I just want to say how much I appreciate the knowledge and detail E EwenS brings to these conversations.

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Well. hopefully it isn't to out of line to respectivefully disagree with him.

EwenS said:

Ark Royal's problems didn't lie in the boiler rooms but in the space above that contained the boiler uptakes that carried the boiler gases across the ship to the funnel. That arrangement allowed gradual flooding of the centre and then port boiler rooms, as she listed to starboard and sank lower in the water. Her loss revealed the problem.

The same design was used in the Illustrious class. A fix was applied to them as they came in for refit or repair from 1942. That involved half height bulkheads being installed in the spaces concerned. The problem was caught early enough to allow the modification of the Audacious class design to carry the boiler uptakes higher in the ship before moving them across the ship.

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While I 100% agree that the boiler uptakes were one of the nails in the coffin (along with no diesel powered generators to keep the pumps running even without steam). Putting 2 boiler in each of the starboard, center and port boiler rooms wasn't ideal.

The Ark's TDS almost did its job - even the starboard boiler room didn't fill immediately, there was time for the crew to evacuate. But then you have a >15m x 8m x 6m offset chamber that filled with water - that's almost 1,000 tons of off center load increasing list. If the boiler rooms had been split into 6 (fore and aft separation of the existing chamber, Ark might very well have only lost only the boiler room adjacent the torpedoes impact. With only 500 tons of off center load/500 tons more buoyancy, the boiler intakes might never have slipped below water level and she wouldn't have had the cascading flooding.

Then, if you get both tugs pulling*, so Ark's crew can see they are making headway, you don't have them taking the risk of restarting the port turbine.

*2nd tug, didn't attach her line 1st try, but rather than try again, beat it back to Gib. 1st tug was making ~3knots, but the Gib Straits current is 2+ knots so progress was painstaking.

Admiral Beez said:

Good point. Though an octuple Pom Pom and 8-10 20mm is a not insignificant increase

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An octuple pom-pom is a considerable weight around 20 tons with ammunition and water. Probably going to need a lot of strengthening if mounted at flight deck level.

Well, I was flattered by Thumpalumpacus's comments the other day and I have no problems with anyone disagreeing with me, just as I hope they would have no problems with me disagreeing with them. However someone once said to me a long time ago that anyone using a term like "respectful (respectivefully)" or "with respect" generally doesn't intend to be.

Ultimately any machinery layout, as with any aspect of ship design, will be a compromise particularly in the Treaty limited times of the interwar period. Between the wars the RN generally chose to put 2 boilers in each boiler room for ships of cruiser size and above. But would more boiler rooms actually have been of benefit? I can perhaps see a case in Ark where the torpedo hit was forward of the boiler room. But more generally?

In "Nelson to Vanguard" Chapter 10 Wartime Damage by D.K. Brown, he comments on the torpedo damage to warships from Admiralty studies and notes:-

"The effects of underwater explosions are notoriously variable and the diagram below shows the probability of rupturing a bulkhead at different distances from the explosion. The length of the hole in the outer bottom would be about half the distance over which such damage would occur. There is strong evidence that the hole in Ark Royal was about 120ft long".

One caveat to that hole size, we don't know how much was caused by the torpedo itself and how much from tearing of the plates after the hit by her motion through the water at c20 knots, but that would be true of any ship being torpedoed, with only the speed varying.

Turning to the diagram itself, Brown notes that it was based on a limited number of examples from mainly riveted ships (Ark's forward section was welded) and should be taken as a rough guide only. But it shows that with a 21" (submarine) torpedo hit there is a 100% probability of bulkheads being ruptured up to 25ft away, dropping to 50% at at 40ft and 0% at 60ft. For an 18" (aircraft) torpedo the distances are 20/30/50ft.

The boiler room in an Illustrious class was about 60ft long so Ark would be similar. So further subdivision of the boiler rooms might have done Ark some good given that the torpedo hit forward of the starboard boiler room. But I doubt that it would have been of any benefit to Indomitable in July 1943 which was hit squarely abreast a boiler room. Her damage reports can be found here.

Certainly when you look at damage to cruisers which were torpedoed more frequently in the machinery compartments generally there are multiple large engineering compartments flooded. And the experience with Yorktown at Midway, which had her boilers in individual compartments and was hit by 2 torpedoes, was that all three of her starboard side boiler rooms flooded. Incidentally in both Ark and Illustrious the boiler rooms were separated from the engine rooms by other compartments, something that I don't believe was true of Yorktown.

Because of the need for more speed, the Implacables needed an extra shaft so the design was able to move from a 3 abreast machinery layout to one where the 8 boilers were in 4 rooms but there were compartments placed between them on the ship centreline. But each boiler room still abutted its neighbour longitudinally.

Machinery design for all ships including carriers did evolve. An 1940 designed Essex for example had 8 boilers in 4 boiler rooms but with a unitised layout. And each boiler room ran the full width of the ship within the torpedo defence layers on either side. The 1942 RN Audacious class followed a similar pattern. This way flooding was intended to be spread more evenly across the ship. But this layout was never put to the test.

The 1942 Colossus class used a combined boiler room / engine room with 2 longitudinally separate compartments, one for each shaft, again taking up almost the full width of the ship (2 boilers and a single turbine in each compartment). This combined unit was planned for the never built RN cruiser designs and was used by the USN for its Des Moines class and the postwar carrier designs.

The most extreme sub-division of a carrier machinery plant was the Midway class. 4 engine rooms, 12 boiler rooms (1 for each boiler) and 10 other machinery spaces for pumps, generators, auxiliary machinery and evaporators. That wasn't repeated postwar because, as confirmed by those who served in the class through to the 1990s, that level of sub-division made them difficult to operate day to day and repair.

A lot of lessons were learned from the ship losses in 1940/41 regarding design and damage control. The former was applied to existing ships where possible as they came in for refit (like the previously referred to bulkheads in the Illustrious class and fitting diesel generators outwith the main machinery spaces) and to new designs (Audacious class). But damage control improved dramatically in all navies based on war experience. And the loss of Ark Royal played a major part in those improvements, partly because so many of her crew survived. Those lessons can be seen in how Indomitable survived her torpedoing in July 1943 when compared to the loss of Ark.

So, in conclusion, while I agree with don4331 that Ark's machinery layout might not be ideal, I don't believe having 6 individual boiler rooms would have made a difference. Pure hindsight would suggest some of the later adopted layouts would have been better because the list would not have been so great.

don4331 said:

Well. hopefully it isn't to out of line to respectivefully disagree with him.

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Not at all. I learn more from disagreements here than simple agreements!

Desperately obsolete carriers. If they had survived, like Furious, they'd have been relegated to secondary duties

HMS Victorious (Illustrious class) was rebuilt and modernized post-war, and served in the Royal Navy- as needed - until 1967.

One of the RN's Colossus class Light Fleet carriers served from early-1945 to 1955 - in RN and RAN service - and from 1956 until 2001 in Brazilian service as the NAel Minas Gerais. At the time of her final decommission she was the longest (55 years) serving aircraft carrier of any nation to that time. (I think she still holds the record but am not 100% sure.)

Minas Gerais completed as HMS Vengeance on 15 Jan 1945, served with RN, RAN and Brazilian Navy and decommissioned 16 Oct 2001. 56 years 9 months. Finally scrapped 2004.

INS Viraat completed as HMS Hermes 25 November 1959, served with RN and Indian Navy, decommissioned 6 March 2017. 57 years 3 months. Finally scrapped last year.

Both those periods include time between RN decommissioning and purchase by successor countries. Extract those and MG edges it by a few months.

EwenS said:

Minas Gerais completed as HMS Vengeance on 15 Jan 1945, served with RN, RAN and Brazilian Navy and decommissioned 16 Oct 2001. 56 years 9 months. Finally scrapped 2004.

INS Viraat completed as HMS Hermes 25 November 1959, served with RN and Indian Navy, decommissioned 6 March 2017. 57 years 3 months. Finally scrapped last year.

Both those periods include time between RN decommissioning and purchase by successor countries. Extract those and MG edges it by a few months.

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HMS Hermes was laid down in 1944, launched in 1953 and completed 1959. Has to be the longest gestation of any warship.

fastmongrel said:

HMS Hermes was laid down in 1944, launched in 1953 and completed 1959. Has to be the longest gestation of any warship.

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French battleship Jean Bart?

Laid down 12 Dec 1936, launched 6 March 1940 but not finally declared complete until 1 May 1955.

fastmongrel said:

HMS Hermes was laid down in 1944, launched in 1953 and completed 1959. Has to be the longest gestation of any warship.

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Fifteen years is a stretch for a ship that unlike Jean Bart, was not delayed by the defeat and occupation of the nation. Mind you, HMS Victory took nineteen years.

Did Britain ever finish an aircraft carrier in an expeditious manner? World Aircraft Carriers List: Master List of RN Carriers

HMS Courageous - 4 years for conversion June 1924 to May 28
HMS Glorious - 6 years for conversion
HMS Ark Royal - 3-1/4 years from laid down to commission
HMS Illustrious - 3 years
HMS Formidable - 3-1/2 years
HMS Victorious - 4 years
HMS Indomitable - 4 years
HMS Implacable - 5-1/2 years
HMS Indefatigable - 5 years
HMS Eagle R05 - 9-1/2 years
HMS Ark Royal R09 - 12 years

The light fleets, Centaurs aside were faster to build, World Aircraft Carriers List: RN Light Fleet Carriers. HMS Colossus was completed in under three years, entering service in Dec 1944. HMS Vengeance did even better, taking only 26 months from laying down to completion. I wonder how fast a dockyard could have completed HMS Implacable if they'd been given the resources and labour that Admiral Fisher put in place to have HMS Dreadnought completed in twelve months.

Was Britain worse than the US or Japan?

Lexington CV-2 - 6 years 11 months incl the conversion time from battlecruiser to carrier while on the slip.
Saratoga - 7 years 2 months
Ranger - 2 years 9 months
Yorktown - 3 years 4 months
Enterprise - 3 years 10 months
Wasp - 4 years 1 month.
Hornet - 2 years 1 month.

As I've pointed out on other threads the contractual build times in 1940/41 for the Essex class were c3 years. The fact that they were generally completed in 18-24 months is a credit to US industrial capacity once war broke out. 13 of the 16 month time saving on Essex came after Pearl Harbor. In a US free from the danger of bombing, round the clock working in the shipyards was possible, unlike in Britain. But even in the US there was a slowdown postwar with ships generally taking several months longer than earlier vessels from the same yards.

The final Essex, Oriskany, took 6 years and 5 months. Construction was suspended in 1946 when she was 85% complete. She was completed to an entirely different design (SCB-27) when work restarted in Aug 1947, incorporating many lessons from WW2 and provision for jets.

Same thing happened with Eagle, Ark Royal and all 4 Centaurs and 5 of the 6 Majestics. All suffered periods of suspension in the years immediately following WW2 and design changes so extending their build times. Ark's design was completely altered to incorporate a side lift, steam catapults, mirror landing aid and finally angled deck. Each alteration caused delay. She was in fact the first carrier to complete with all of the last 3 features, beating the USS Forrestal and HMAS Melbourne into service in 1955. Hermes represents the most extreme example, because she also suffered design changes to incorporate provision for a much later generation of aircraft and their guided missiles which had not even been conceived when she was laid down in 1944.

In Sept 1942 when Eagle and Ark Royal were authorised, completion was expected in March 1946. While Eagle was laid down the following month, Ark immediately suffered a 9 month delay before being laid down. By the end of the war completion was expected in mid-1947. Then you arrive in Britain's post war financial and manning crises.

Some of the Illustrious class build times were extended due to delays in obtaining armour plate from Czechoslovakia. Those delays allowed the redesign of Indomitable in 1938 while she was building. Implacable and Indefatigable were delayed by WW2 priorities in the yards (demand for destroyers took priority in those two yards in 1940/41), suspensions and labour shortages not to mention substantial design changes as a result of war experience, and, when they finally left the yards, machinery problems that added 3-4 months to their completion times while they were ironed out. In Sept 1939 the anticipated completion dates of that pair were Oct 1941 and June 1942 which would have given them build times of 2 years 8 months. Minor correction for your Indefatigable data, she only took 4 years 6 months.

As for Japan:-
Hosho - 2 years
Akagi - 6 years 4 months incl conversion time from battlecruiser while on the slip.
Kaga - 7 years 8 months
Rjuyo - 3 years 5 months
Soryu - 3 years 1 month
Hiryu - 3 years
Shokaku - 3 years 8 months
Zuikaku - 3 years 4 months
Taiho - 2 years 8 months
Unryu - 2 years
Akagi - 23 months
Katsuragi - 23 months

So I think that you are being unduly harsh on Britain.

Good points. CVLs aside, I wonder what the fastest time was for building a fleet carrier. Hornet at 2 years 1 month has to be close.

Admiral Beez said:

Good points. CVLs aside, I wonder what the fastest time was for building a fleet carrier. Hornet at 2 years 1 month has to be close.

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CV-10 Yorktown 16.5 months
CV-12 Hornet 15 months
CV-13 Franklin 14 months

Some of the other middle Essex class come in around those times. Nothing beats US industrial might in WW2. All the above 3 came from the same yard as Essex (20 months). Then add another 4-5 months on average for work up and they arrive at PH ready to fight.

EwenS said:

Nothing beats US industrial might in WW2.

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I wonder how fast the US could today build a non-nuclear flattop. The America-class LHA seem to take about five year from keel to commission.

Does the US still make Main Battle Tanks? IIRC all the Abrams in service today are just refurbished models produced years earlier. How fast could they ramp up to make a thousand Abrams? Not to pick on the USA, I imagine no one can make the complex ships, tanks and planes of today at WW2 speed.