Refinements in RN CV decisions?

zen

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Two 1937 Carriers were ordered. Formidable and Indomitable.
The latter was a modified design, adding in a lower short hanger at the rear.
But what if it had been kept to just a repeat Illustrious?

Arguably a fourth Illustrious might have permitted a 1950 Victorious modernisation repeat on this AH Indomitable. Which should be much lower cost and result in two such Carriers through the 60's and 70's.

1938 Carrier, E-in-C stated maximum available power from three shaft arrangement was between 126,000shp to 135,000shp but he insists these figures excessive and three shafts would be of low propulsive efficiency. Designers were forced to four shaft arrangement and thus Implacables resulted.
But post war in the 50's the higher power plant and less efficient three shaft was felt acceptable.
So what happens if E-in-C is told to achieve his estimates and designers told to develop three shaft solutions?
Could this then be a refined Indomitable/Implacable design?

Note that the upper figure of 135,000shp is divided by 3 a figure of 45,000shp.....much as late 50's Y300 and the revised CVA-01 plant.

The flipside is with four plant and shaft layout to opt for a full new design. Not quite Audacious but arguably more than Implacable.
Opting then in 1938, resource constraints by 1940 force minimal changes. But two years lead could alter that despite the general acceleration to war. Though unlikely to actually accelerate laying down and building.


The third is my bugbear, why wasn't Controller asking what could fit Davenport No.10 earlier? His request during the Malta process is likely after Design C approval 8 Oct 1943.
Responded to 31 Jan 1944!!!
But this question ought to have been asked as early as 1938 if not 1939 or at the latest late 1942.
Inject this rational change then and four shaft CV design to limit of infrastructure is inherent to studies from then.
 
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EwenS

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Two 1937 Carriers were ordered. Formidable and Indomitable.
The latter was a modified design, adding in a lower short hanger at the rear.
But what if it had been kept to just a repeat Illustrious?

Arguably a fourth Illustrious might have permitted a 1950 Victorious modernisation repeat. Which should be much lower cost and result in two such Carriers through the 60's and 70's.

1938 Carrier, E-in-C stated maximum available power from three shaft arrangement was between 126,000shp to 135,000shp but he consists these figures excessive and three shafts would be of low propulsive efficiency. Designers were forced to four shaft arrangement and thus Implacables resulted.
But post war in the 50's the higher power plant and less efficient three shaft was felt acceptable.
So what happens if E-in-C is told to achieve his estimates and designers told to develop three shaft solutions?
Could this then be a refined Indomitable design?

The flipside is with four plant and shaft layout to opt for a full new design. Not quite Audacious but arguably more than Implacable.
Opting then in 1938, resource constraints by 1940 force minimal changes. But two years lead could alter that despite the general acceleration to war. Though unlikely to actually accelerate laying down and building.


The third is my bugbear, why wasn't Controller asking what could fit Davenport No.10 earlier? His request during the Malta process is likely after Design C approval 8 Oct 1943.
Responded to 31 Jan 1944!!!
But this question ought to have been asked as early as 1938 if not 1939 or at the latest late 1942.
Inject this rational change then and four shaft CV design to limit of infrastructure is inherent to studies from then.
Correction. The design sequence is (see Friedman "British Carrier Aviation":-

Illustrious class designed 1936 and 2 ordered in 1936 Programme (Illustrious & Victorious) & 2 in 1937 Programme (Formidable & Indomitable). All ordered & laid down in 1937.

Implacable class (1938 carrier) designed late 1937/early 1938 as an Illustrious firstly with a request for more speed and then greater aircraft capacity. Initial design completed by Feb 1938, sent to the Board for approval in Aug and finally approved Nov 1938. Implacable was then laid down in Feb 1939. The second ship initially included in the 1938 Programme was pushed back and becomes the "1939 carrier" later named Indefatigable which is laid down after the outbreak of war, in Nov 1939.

Indomitable, laid down 10 Nov 1937, was already subject to an 8 month delay in completion by early 1938 due to predicted delays in her armour coming from Czechoslovakia. So the order at that point was modify the Illustrious design to incorporate as many of the 1938 carrier features then under discussion as possible without incurring any major delay in completion. The revised design was signed off on 31 March 1938.

Given that Implacable wasn't approved until Nov 1938 and laid down until Feb 1939, presumeably the EinC spent at least the period Mar-Aug 1938 designing the new machinery layout (possibly longer). So the question is when was it finalised? Meanwhile the construction of Indomitable is ongoing. If construction is stopped, then it seems to me that that would lead to further delays in her eventual completion which was not the purpose of the redesign.

When you look at Indomitable's build time (47 months) that compares with Illustrious (37), Victorious (48) and Formidable (41). So it seems to me that the aim of not incurring any further delays was achieved.

As for a complete redesign, it needs to be remembered that the 1936 London Treaty carrier limit of 23,000 tons is still in place in 1938 when the design is being worked through. You know by the end of 1938 that war is coming but you don't know when. Politically you can't bin the Treaty as that opens a whole can of worms. So within the limit, if you increase machinery weight, you have to sacrifice something and that was some of the armour.

In the early design stages of the 1938 carrier there were two options of similar size in tonnage and dimensional terms. Design A was 140,000shp with 33 aircraft. Design D "trading protection for more aircraft" with 48 aircraft. The final Implacable design came out of the latter. The problem was staying within the Treaty limit. When you look at the design of Indomitable & Implacable it becomes apparent that in going from the single hangar to the double hangar layout, the lower hangar had to be dropped a deck compared with Illustrious, presumeably from a stability perspective. The result of that however was that it couldn't run the whole length of the ship as at the forward end the fan room (above the boiler room) presented an obstruction. Somewhere in the past I've analysed the depth of the 3 ships to explain that. i'll try to remember where I posted it and dig it out.

As for the dockyard infrastructure, it is one of the great mysteries to me. On the one hand there is no great upgrading of dry docks in Britain inter-war, yet the Govt chose to spend money on the King George VI dock in Singapore at this time (opened 1938 and then the largest dry dock in the world). All I can think of is that what was there was adequate for the ships being built in the late 1930s and a decision was taken that funds would be better spent on ships now rather than facilities for bigger ships down the line. Rearmament was already costing a huge amount.

But the US dry dock building programme didn't get funding until 1938 along with other improvements to their Navy Yards. The eventually spent $590m through to 1945 on such works. Work on the first two super sized dry docks under that spend didn't start until June 1940, designed to be just in time to lay down the Montana class. And by then of course Britain was at war.
 

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Found what I wrote about the hangar & hull depth of the Implacables & Indomitable on another site over 2 years ago. I hope that it still makes sense. It did, to me at least, at the time!!!

Indomitable was the subject of an 8 month delay in her construction as her armour had to come from Czechoslovakia. So while the 1938 carrier was being designed the opportunity was taken to fit some of the improvements into Indomitable. So she starts life like the other 3 Illustrious class and she remained so from the keel to the upper deck. The upper deck is the deck that carries the boiler uptakes across the ship to the funnel uptakes on the starboard side. Hobbs In “British Aircraft Carriers” puts it this way – ”The original hangar now became the lower hangar… The area forward of it was converted into extra workshops and accommodation to support the larger air group”. Due to the 16ft height it was possible to get 2 decks in this space just as with the Implacables. A second hangar was then built on top.

The difference in the design of these 3 ship groups therefore becomes the depth of the hull from keel to flight deck. Per Friedman:-

Illustrious class - 68ft (72ft for Victorious post modernisation)

Indomitable – 74ft

Implacable – 71ft (resulting from the lower hangar being 14ft)

Here however there is a discrepancy between the 2 authors. Friedman is very clear that the hull depth only increased by 6ft in the design of Indomitable, and quotes the 2 figures above in the chapter on the armoured carriers. In the post-war rebuild chapter he gives Implacable at 71ft and Victorious as modernised at 72ft. The figures for Victorious agree with Watton’s drawings pre and post modernisation.

But Hobbs refers to the flight deck in Indomitable getting lifted by 14ft. He then goes on to say in the chapter on the Implacables, that their freeboard was 2ft less than Indomitable but 12ft greater than Illustrious.

In this I think that Hobbs is wrong. Looking at the internal profile drawings of Implacable in Friedman, it is clear that her lower hangar deck is not at the same level as Illustrious’. It is one deck lower. As a result the hangar could not be extended further forward as it ran into the transverse boiler uptakes. It also appears that the armour on the lower hangar floor was actually a deck higher amidships to protect the area over those transverse uptakes That would then make sense of the difference in depth between Illustrious and Implacable i.e. 68ft + depth of new hangar (14ft) – lower depth of lower hangar (2ft) – height of 1 deck (say 7ft) = 73ft v Friedman’s 71ft. The difference is about 3% which is probably due to my measuring errors.

I’m not sure how you square the 2 sets of figures without detailed plans of the latter 2 ships, which I don’t have.

The point is that the lower hangar on Indomitable and the Implacables was created by a combination of dropping what was the lower hangar by a deck and by deepening the hull.
 

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It was lucky the timing worked out the way it did, had Indomitable's hull construction reached the lower hangar deck level it would have caused greater delay removing all the beams and fitting new ones. They might have had to revert to Plan A and retain the original single hangar.
 

zen

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If Indomitable is built as just another Illustrious, then the question has to be, does this assist the speed of building?
From what I see here possibly.
And does it materially impact actual operations to a significant degree?


Given that Implacable wasn't approved until Nov 1938 and laid down until Feb 1939, presumeably the EinC spent at least the period Mar-Aug 1938 designing the new machinery layout (possibly longer). So the question is when was it finalised?
Good question.


As for a complete redesign, it needs to be remembered that the 1936 London Treaty carrier limit of 23,000 tons is still in place in 1938 when the design is being worked through. You know by the end of 1938 that war is coming but you don't know when.
Not examining treaty breaking options seems illogical. Such would be subject to secrecy and inform the possible political negotiations and is good contingency planning.

Drydocks.
It is certainly the case new build options were examined pre WWII. But it seems somewhat a failure to expand existing facilities bar the combination of two docks into Davenport No.10. Spending is confined to overseas facilities. But without a military drydock of comparable size. This overseas expansion seems flawed.

I think while history explains a situation to state nothing of substance could change is fundamentally flawed and especially so in section labeled Alternative History.

Things could have been different.
Yes this looks like a Compound problem. In that a series of decisions over the course of years upto and during WWII are likely needed.
But none of them seem impossible or overly distorting in their discreet locus.

If E-in-C is told pursue 3 shaft arrangement, and designers told to wrap a new CV design around it. This alleviates certain constraints during and after WWII by a modest but useful degree.
If that makes Implacables design more like a Illustrious or Indomitable. This also makes a possibility that Irresistible doesn't become Audacious.
It also brings to focus testing and development facilities for plants, shafts and props, to the fore earlier. Making postwar upgrade more likely.
As it does drydocks.
As it does for the process of Malta's design itself.
 

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Looking at some of the data I have available about construction times, estimated completion dates etc, I don’t think building Indomitable as an Illustrious would get her into service any quicker, especially as her armour was being delayed.

Based on what we know, her estimated completion date in Sept 1939 was April 1941. That was 6 months before her launch so her steelwork would have been well on the way to completion.

Cabinet papers around this time discussing the 1940 Programme refer to delays in the existing Programmes. For the Illustrious class these were already:-

Illustrious - 4 months
Victorious - 8 months
Formidable - 3 months
Indomitable - 6 months
Implacable - 3 months.

What is not clear is what that delay is based on.

An April 1941 completion would have given a total build time of 41 months so equalling the build time of Formidable and only 4 months longer than Illustrious. And remember the estimated 8 month delay back in early 1938 for the armour most of which was structural and was incorporated in the hull build before launch.

Of the further 6 month delay during wartime, 4 arose after Sept 1940. Air raids on Barrow, with the VA yard a principal target, began in Sept 1940 with the worst attacks being March-May 1941. 25% of the town’s housing stock was damaged or destroyed, as well as damage in the yard itself. That must have had some effect on the workforce and the ship.

By way of comparison the fastest build was Illustrious, built in the same yard. In Sept 1939 her completion date was estimated to be April 1940. It slipped by only a month thereafter.

Compared to Illustrious, Indomitable spent an extra 5 months on the slip and 5 months fitting out. It seems to me that the former is down to the 1938 expectation of armour delays and the latter to the consequences of trying to build ships in the middle of a war.

Victorious was the ship that suffered greatest delays. In Sept 1939 her completion date was estimated as Sept 1940. When that date came round it was Dec 1940. She finally completed in May 1941.

So in conclusion, I really don’t think building Indomitable as an Illustrious is going to get her into service any quicker.
 

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As for a complete redesign, it needs to be remembered that the 1936 London Treaty carrier limit of 23,000 tons is still in place in 1938 when the design is being worked through. You know by the end of 1938 that war is coming but you don't know when.
Not examining treaty breaking options seems illogical. Such would be subject to secrecy and inform the possible political negotiations and is good contingency planning.
The previous naval treaties set an aircraft carrier limit of 27,000 tons.

As I understand it the reduction was because the Admiralty wanted to reduce the cost of each ship so that they could be built in the numbers required. I think they asked for a reduction to 22,000 tons at the Second London Naval Conference and were able to negotiate the reduction to 23,000 tons in the resulting Treaty. Similarly they asked for a reduction in the cruiser displacement limit from 10,000 tons to 7,600 tons and got a reduction to 8,000 tons.

One of the reasons why I mentioned the reduction of the cruiser displacement limit to 8,000 tons is that the Fiji class broke the Treaty. According to Morris in Cruisers of the Royal and Commonwealth Navies their standard displacement when completed was 8,525 tons, which is about 6.5% more than the Treaty allowed. Apply that increase to the 6 aircraft carriers in the 1936-37 to 1938-39 and that produced a standard displacement of about 25,500 tons.

A Third London Naval Conference was scheduled to take place in 1941 which would negotiate a new Treaty to replace the Second LNT when it expired on 31st December, 1942. Viz.:-

Second LNT Articles 27 and 28.png

Article 4 of the Treaty was modified by the protocol of 30th, June 1938, i.e. the one that allowed capital ships to mount guns of up to 16" calibre and have a standard displacement of up to 45,000 tons.

So there's one precedent for the British breaking the Second LNT and another precedent for amending the Treaty to allow ships of greater displacement.

Also (as already noted) Implacable and Indefatigable weren't laid down until 1939 and at the time (as I understand it) weren't due to be completed until 1942. So they'd be under construction while the Third LNT was being negotiated and be completed close to or even after the current Treaty expired.

So if the Admiralty was prepared to cheat...

They could have said that they were 23,000 ton ships when their construction was announced with the intention of announcing later on that a mistake had been made in the displacement calculations and ask the Americans and French for a protocol to amend the existing Treaty to accommodate this and/or when negotiating the replacement treaty press for an increase in the aircraft carrier displacement limit to accommodate them.

Or go back to 1935 and don't reduce the aircraft carrier and cruiser displacement limits in the first place.
 
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NOMISYRRUC

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Or go back to 1935 and don't reduce the aircraft carrier and cruiser displacement limits in the first place.
I've always thought that reducing the aircraft carrier and cruiser displacement limits to 23,000 tons and 10,000 tons respectively, was a false economy.

If the Second London Naval Treaty had left the aircraft carrier limit at 27,000 tons what could the DNC have done with the extra 4,000 tons?
 

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As far as I know the Admiralty allowed three years for the building of an aircraft carrier.

If that's correct. This is the result.

Aircraft Carrier building times Mk 2.png

The dates are from Conway's 1922-46 and they are arranged in the order in which they were laid down.

NB: More than a few of my recent statements have been proved to be wrong. This could be wrong as well.
 

zen

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If E-in-C gets minimum power predicted of 42,000shp (3 plants giving the 126,000shp figure), then this is somewhat transformative.

Implacables are now much more a development of Illustrious. Likely with the still limited height double hanger of OTL.
This make Indomitable still an intermediate vessel again as per OTL.

To my understanding capital ship plant is one of the bottlenecks in production. A cut of 25% in number of plants for Implacables must have a modest effect on

But this exerts influence on Centaur and Irresistible/Audacious design processes. As now they have 168,000shp and 84,000shp respectively.
Arguably Malta might opt for a 5 shaft arrangement for 210,000shp or to further improve induvidual plant power upto 45,000shp to 50,000shp.
 

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But the US dry dock building programme didn't get funding until 1938 along with other improvements to their Navy Yards. The eventually spent $590m through to 1945 on such works. Work on the first two super sized dry docks under that spend didn't start until June 1940, designed to be just in time to lay down the Montana class. And by then of course Britain was at war.

Do you have information on what was done and where?
 

Hood

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There was no sign of wanting to cheat. At one point it was desired to fit 12x 4in guns to Unicorn which would have taken it out of the auxiliary category. By itself this was not an issue given it didn't breach the carrier tonnage limits. There seems to have been a worry if it was classified as a carrier that the Treasury might count it towards the number of carriers the RN wanted rather than recognising it as a depot ship. Not until the legend was presented in January 1939 was the classification as a carrier confirmed.

Well I guess for the public works programme during the Depression relief years that new bypasses seemed better value for money than new dry docks.
 

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Two 1937 Carriers were ordered. Formidable and Indomitable.
The latter was a modified design, adding in a lower short hanger at the rear.
But what if it had been kept to just a repeat Illustrious?

Arguably a fourth Illustrious might have permitted a 1950 Victorious modernisation repeat on this AH Indomitable. Which should be much lower cost and result in two such Carriers through the 60's and 70's.
With regret my honest opinion is that the cost of rebuilding this ALT-Indomitable to the same standard as Victorious is unlikely to have been much lower that the cost of the latter ships "great rebuild".

Hopefully, there would be time and money savings by deciding to re-boiler the ship before the refit began.

But the modernisation of Victorious was so extensive that I doubt that it was a significant proportion of the cost, which included:
  • Cutting the ship in two so that it could lengthened by 30 feet and the beam increased by 8 feet.
  • Stripping the hull to the hangar deck.
  • Rebuilding virtually every below decks compartment that was outside the machinery spaces.
  • Converting the ship's electrical system from DC to AC which included renewing all the wring.
  • Renewing all the piping.
  • A new fixed armament.
  • Advanced (and expensive) electronics, i.e. The Type 984 radar, CDS and DPT.
Most of the above came from the chapter on HMS Victorious in Royal Navy Aircraft Carriers 1945-1990 by Leo Marriott. He wrote on Page 71.
Work on this was proceeding when it was retrospectively decided that new boilers would be installed to replace the old Admiralty pattern units, some of which had been damaged in an accidental fire. This involved undoing some of the work already carried out and meant further delay.
I don't recall reading about the fire before. Does anyone know if this fire damage was a significant factor in making the decision to fit new boilers?
 

EwenS

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As for a complete redesign, it needs to be remembered that the 1936 London Treaty carrier limit of 23,000 tons is still in place in 1938 when the design is being worked through. You know by the end of 1938 that war is coming but you don't know when.
Not examining treaty breaking options seems illogical. Such would be subject to secrecy and inform the possible political negotiations and is good contingency planning.
The previous naval treaties set an aircraft carrier limit of 27,000 tons.

As I understand it the reduction was because the Admiralty wanted to reduce the cost of each ship so that they could be built in the numbers required. I think they asked for a reduction to 22,000 tons at the Second London Naval Conference and were able to negotiate the reduction to 23,000 tons in the resulting Treaty. Similarly they asked for a reduction in the cruiser displacement limit from 10,000 tons to 7,600 tons and got a reduction to 8,000 tons.

One of the reasons why I mentioned the reduction of the cruiser displacement limit to 8,000 tons is that the Fiji class broke the Treaty. According to Morris in Cruisers of the Royal and Commonwealth Navies their standard displacement when completed was 8,525 tons, which is about 6.5% more than the Treaty allowed. Apply that increase to the 6 aircraft carriers in the 1936-37 to 1938-39 and that produced a standard displacement of about 25,500 tons.
The design and build process was not an exact science. Margins were built in and savings during construction hoped for. Friedman in "British Carrier Aviation" has a table showing the final design characteristics of the various British carriers with the following standard displacements:-
Ark Royal - 22,000 tons
Illustrious - 23,207 tons
Indomitable - 23,080 tons
Implacable - 23,460 tons

But in the text he notes that while Ark Royal is generally quoted at 22,000 tons standard displacement as above, the actual design figure approved by the Admiralty was 22,800 tons, but again with the hope that savings could be made. When completed she was 22,585 tons standard (reported under he Treaty as 22,500 tons).

And care needs to be taken with the figures for the Fiji class. They were designed under the Treaty but completed after the whole Treaty system collapsed on 3 Sept 1939 with the outbreak of WW2. .

Friedman in his "British Cruisers Two World Wars and After" provides a detailed design history of the 18 month timescale that led to the Fiji class. The design approved by the Admiralty in Nov 1937 was 8,170 tons standard. That was within the margin that was believed acceptable and there was hope, based on past experience, that weight could be saved in the construction process. By Jan 1939 this estimate had grown to 8,268 tons partly due to the addition of torpedo tubes (the original design only had provision for these). It was only after the launch of Fiji in May 1939 that it became apparent that the design was overweight.

There was then a whole series of approved additions, detailed in Friedman, while she completed that added up to 319 tons, most of which could never have been envisaged when the design was signed off in Nov 1937.

Undoubtedly the design was "tight" weight wise but I don't believe that it is an indication that the British sought to deliberately flout the Treaty limit.


A Third London Naval Conference was scheduled to take place in 1941 which would negotiate a new Treaty to replace the Second LNT when it expired on 31st December, 1942. Viz.:-

Article 4 of the Treaty was modified by the protocol of 30th, June 1938, i.e. the one that allowed capital ships to mount guns of up to 16" calibre and have a standard displacement of up to 45,000 tons.

So there's one precedent for the British breaking the Second LNT and another precedent for amending the Treaty to allow ships of greater displacement.
The question of the increase in gun size was provided for in the 1936 London Treaty. Article 4

Article 4​

  1. No capital ship shall exceed 35,000 tons (35,560 metric tons) standard displacement.
  2. No capital ship shall carry a gun with a calibre exceeding 14 in. (356 mm.); provided however that if any of the Parties to the Treaty for the Limitation of Naval Armament signed at Washington on 6 February 1922, should fail to enter into an agreement to conform to this provision prior to the date of the coming into force of the present Treaty, but in any case not later than 1 April 1937, the maximum calibre of gun carried by capital ships shall be 16 in. (406 mm.).
  3. No capital ship of sub-category (a), the standard displacement of which is less than 17,500 tons (17,780 metric tons), shall be laid down or acquired prior to 1 January 1943.
  4. No capital ship, the main armament of which consists of guns of less than 10 in. (254 mm.) calibre, shall be laid down or acquired prior to 1 January 1943.
Japan had announced its intention to withdraw from the Treaty system in March 1934 , and did so with effect from 31 Dec 1936, on the expiration of the 1922 Washington & 1930 London Treaties. Japan, as a signitory to the 1922 Washington Treaty, formally rejected the proposal on 14" guns on 31 March 1937. The USA then rejected the limit, notifying the British in July 1937. And therefore the US built the North Carolina and South Dakota classes as a result.

So the 1938 Protocol, signed on 30 June 1938, only covers the increase in tonnage from 35,000 tons to 45,000 tons. That became necessary as the Japanese wouldn't provide assurance that they would limit themselves to the 35,000 ton limit. The USA then sought to move to a higher limit. Even then the British announced that they would limit themselves to 40,000 tons, which was the figure they proposed but the USA rejected.

So the indications are that the British wanted to stick to previously agreed limits. As the BB was still the king of the fleet, that was what concerned everyone the most.

Looking at carriers specifically, Britain went to 23,000 tons with the Illustrious class after building the 22,500 ton Ark Royal. In 1938 the USA, via the Naval Act of 1938, chose to increase its Washington Treaty carrier tonnage of 135,000 tons by 40,000 tons. And as a consequence ordered a single repeat Yorktown of 20,000 tons (USS Hornet CV-8) in March 1939. The next carrier, the Essex CV-9, was a design that was initiated under the Treaty system but concluded after it ended, and after a major increase in tonnages allowed by US home legislation, allowing an increase to 27,100 tons standard displacement.

Meanwhile over in Japan, they had complied with the Treaty limits for carriers until 31 Dec 1936 when they left the Treaty system. It was only with the Third Naval Replenishment Programme of 1937 (which also included the first pair of the Yamato class BB) that they sought to build bigger. That was the Shokaku & Zuikaku of 25,675 tons standard displacement, laid down in Dec 1937 and May 1938. Japan was under no obligation to report the size of these ships to anyone. And anyway these ships were laid down after the Illustrious class. Japan operated under a veil of secrecy so it is highly unlikely that anyone knew the size of these two ships in the 1937-39 timescale.

So in 1938 there is no incentive for Britain to choose to break the Treaty carrier limits.

Also (as already noted) Implacable and Indefatigable weren't laid down until 1939 and at the time (as I understand it) weren't due to be completed until 1942. So they'd be under construction while the Third LNT was being negotiated and be completed close to or even after the current Treaty expired.

So if the Admiralty was prepared to cheat...

They could have said that they were 23,000 ton ships when their construction was announced with the intention of announcing later on that a mistake had been made in the displacement calculations and ask the Americans and French for a protocol to amend the existing Treaty to accommodate this and/or when negotiating the replacement treaty press for an increase in the aircraft carrier displacement limit to accommodate them.

Or go back to 1935 and don't reduce the aircraft carrier and cruiser displacement limits in the first place.
But the Admiraly were not prepared to "cheat" to anything like the extent you need for your plan (c2,500 tons). And remember all the details that had to be supplied both at the point of laying down a vessel and annually during its construction period in respect of any design alterations.

Articles 11 to 21.

In Sept 1939 the estimated completion dates for the Implacable and Indefatigable were Oct 1941 and June 1942. Britain was not required to initiate discussions on holding a "Third" London Naval Treaty Conference until the final quarter of 1940 with a view to holding it in 1941. (Article 28). So at least Implacable if not both, would have been launched by the time this process even started, and both would be complete and in service by the time the 1936 Treaty expired. It hardly helps negotiating a new limit if you are by then clearly seen to be "cheating".
 

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But the US dry dock building programme didn't get funding until 1938 along with other improvements to their Navy Yards. The eventually spent $590m through to 1945 on such works. Work on the first two super sized dry docks under that spend didn't start until June 1940, designed to be just in time to lay down the Montana class. And by then of course Britain was at war.

Do you have information on what was done and where?
Here you go

Other chapters cover other aspects of support for the USN.
 

EwenS

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As far as I know the Admiralty allowed three years for the building of an aircraft carrier.

If that's correct. This is the result.

The dates are from Conway's 1922-46 and they are arranged in the order in which they were laid down.

NB: More than a few of my recent statements have been proved to be wrong. This could be wrong as well.
Your final entry for Eagle at VA(T) should be 23/12/43.

Is the Scheduled Completion date column simply based on your comment about the Admiralty allowing 3 years for a carrier build or actual information from official documents?

In Sept 1939 Implacable and Indefatigable were scheduled to complete Oct 1941 and June 1942 for an optimistic 32 month build time. In Sept 1942 Audacious and Ark Royal were scheduled for completion March 1946 (before even being laid down) or a 41 month build time. The first date I have for Eagle is May 1947 and that was in March 1944. Data from Moore " Building for Victory".

In late 1941 the Admiralty carried out a study and the estimated time for construction of a fleet carrier was 46 months which is a few months over the actual average for the 4 Illustrious class. Moore again.

And the build times only tell part of the story. The Implacables are a sorry tale of suspensions (Indefatigable 4 months in 1940), changing priorities, lack of labour (no work on Implacable for 13 months in 1940/41), redesign and all culminating in 2-3 months sorting out machinery defects between their leaving the yards on the Clyde and finally entering service.

Audacious & Ark Royal are then subject to suspension post-war. While Eagle (Audacious) completed largely as designed, Ark emerged in a completely different configuration.
 

EwenS

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Two 1937 Carriers were ordered. Formidable and Indomitable.
The latter was a modified design, adding in a lower short hanger at the rear.
But what if it had been kept to just a repeat Illustrious?

Arguably a fourth Illustrious might have permitted a 1950 Victorious modernisation repeat on this AH Indomitable. Which should be much lower cost and result in two such Carriers through the 60's and 70's.
With regret my honest opinion is that the cost of rebuilding this ALT-Indomitable to the same standard as Victorious is unlikely to have been much lower that the cost of the latter ships "great rebuild".

Hopefully, there would be time and money savings by deciding to re-boiler the ship before the refit began.

But the modernisation of Victorious was so extensive that I doubt that it was a significant proportion of the cost, which included:
  • Cutting the ship in two so that it could lengthened by 30 feet and the beam increased by 8 feet.
  • Stripping the hull to the hangar deck.
  • Rebuilding virtually every below decks compartment that was outside the machinery spaces.
  • Converting the ship's electrical system from DC to AC which included renewing all the wring.
  • Renewing all the piping.
  • A new fixed armament.
  • Advanced (and expensive) electronics, i.e. The Type 984 radar, CDS and DPT.
Most of the above came from the chapter on HMS Victorious in Royal Navy Aircraft Carriers 1945-1990 by Leo Marriott. He wrote on Page 71.
Work on this was proceeding when it was retrospectively decided that new boilers would be installed to replace the old Admiralty pattern units, some of which had been damaged in an accidental fire. This involved undoing some of the work already carried out and meant further delay.
I don't recall reading about the fire before. Does anyone know if this fire damage was a significant factor in making the decision to fit new boilers?
While there are sources out there that have Vic's waterline length increasing by 30 ft, so suggesting she was cut in half and stretched, those same sources claim her length between the perpendiculars did not change.

The truth is she was not cut in half and lengthened. Friedman still has her waterline length post modernisation at 710ft, same as it was when first completed. The increase in length comes from rebuilding the bow above the waterline and increasing the length of the flight deck with overhangs. The increase in beam was achieved by bulging the hull.

Never read of fire damage to the boilers in any of my multiple sources.

Hobbs in a Warship 2020 article on her reconstruction says this

"The work carried out between 1950 and 1958 to build a new Victorious should, therefore, be thought of as a series of modernisations that took place within a prolonged, overall building process. Some of them required work that had already been completed to be dismantled before the new equipment and structure could be fitted".

The most famous of these is of course the boiler saga.
 

zen

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Which implies that a second modernisation of a ship of the same design ought to be quicker and cheaper.

But obviously the question is....is it cheap and quick enough to justify for the capability achieved?

Arguably if the Implacables are to a more similar design to Victorious (three shaft/plant setup) then the case to continue those modernisations gains strength.
Which would be the case if below the lower hanger deck the ship was a slightly stretched Illustrious in design.

It also defers the new carrier effort back enough to invest in facilities for development and operation of such. The 1952 process looking at the USN and the Forrestal class.

Which implies that the debate on the future limitations of carrier development and production are had while modernisations continue.
 

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To my understanding capital ship plant is one of the bottlenecks in production. A cut of 25% in number of plants for Implacables must have a modest effect on
I'm not following you with that statement.

The process was that the machinery was designed by the Admiralty. That design was then passed to the shipbuilders. The shipbuilding companies then tendered to build it for each ship. In almost all cases the big naval shipbuilders built the machinery for the ships they were building. The only cases where that did not happen was with the ships built in the Royal Dockyards or the 1930s reconstructions that got new machinery. For auxiliary machinery the Admiralty chose sub-contractors from a list which allowed commonality between vessels of the same class.

Given the extended build time for the Implacables I doubt that it presented a problem for Fairfield or John Brown in building this machinery even with all the other work that they had on hand.

But the machinery that went into the Implacables had problems to begin with that were only revealed on trials. Both ships service entry was delayed by 2-3 months while they were ironed out.
 

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It is weird to think Victorious was ordered in 1937 and retired in 1967. Yet that's "only" 30 years - not that much for a carrier, some lasted 50 years or more.
But evolution of naval aviation within the same span of time was jaw-dropping. As far as the USN was concerned it went from Grumman F3F to McDonnel F4H...

From this...

To this.
 

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Link to Post 14.

1936 Treaty Article 4.png
Article 4 of the Treaty was modified by the protocol of 30th, June 1938, i.e. the one that allowed capital ships to mount guns of up to 16" calibre and have a standard displacement of up to 45,000 tons.
My understanding was that the protocol of 30th June 1938 amended Article 4, Paragraph (1) which was the displacement increase from 35,000 to 45,000 tons and invoked the escalator clause of Article 4, Paragraph (2) increasing the maximum gun calibre from 14 inches to 16 inches.

That's what I meant by the above sentence which could have been written more clearly.

However, having reviewed the 27 pages of The Protocol Signed June 30, 1938 by the United States, France, and the United Kingdom Providing for Naval Escalation Under The Treaty of March 25, 1936 that I downloaded from the Library of Congress of website it appears that the Protocol increased the maximum displacement to 45,000 tons but only confirmed the increase to 16" gun calibre under the escalator clause of Paragraph 4 (2) and that the latter was invoked on 31st March 1938 rather than April 1937. See below.

Protocol of 30.06.38 Page 1.png

Protocol of 30.06.38 Page 2.png
 

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NOMISYRRUC

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Snip to Post 16.
The the Scheduled Completion date column is simply based on my comment about the Admiralty allowing 3 years for a carrier build and not on actual information from official documents. Although I did not explicitly write as much it was implicitly obvious.

All the laying down, launching and completion dates are from Pages 18 to 21 of Conway's 1922-46. I checked them twice before copying and pasting it into Microsoft Paint. I've looked at the entry for the Eagle laid down at Vickers-Armstrong (Tyne) again and it does say 19th April 1944 or to be exact 19.4.1944.

Conway's 1922-46 also says that Jean Bart was laid down in January 1939 (Page 260), that the pp length of the Implacable class was 673 feet (Page 20), the lower hangar of Indomitable was 168 feet long (Page 20) and that the hangars of the Colossus class were 445 feet long (Page 22). Please don't correct me with the correct laying down date, pp length and hangar lengths because I know that they're wrong.
 

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Link to Post 17.
I still think that rebuilding @zen's ALT-Indomitable to the same standard as Victorious wouldn't be much cheaper than the rebuild that Victorious had in the 1950s. That's regardless of whether or not Victorious was cut in two and a new section of hull added.

Friedman does say that one of the reasons for replacing the boilers on Victorious was that they were needed to generate more electric power. He didn't say so specifically but it appears that the extra power was needed for the Type 984 radar et al.
 

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One of the factors that caused the Implacables to be ruled out of modernisation was degree to which they were substantially different from Victorious. The 4 shaft and plant arrangement took up much more of the hull volume and this made the changes to how the modernisation could be implemented.
The limitations on hull height resulting in the modernisation forcing much greater bulging to retain stability. Which in turn effected predicted speed.
All with less than ideal results for hanger, potential for gallery deck and island size.

Now IF Implacables are more like improved Illustriouses and with the similar beneficial availability of hull volume. Then the Victorious standard of modernisation is not only massively more achievable. They deliver slightly more capability than Victorious.

A force of 3 or 4 so modernised.
Victorious by started 23 Oct 1950 finished Jan 1958 = 7 years 2 months and 8 days.
But many changes were incorporated during the process including significant redesign.
A more rational repeat Victorious ought to take 4.5 years
Indomitable start Jan 1958 finishes July 1962
Implacable start August 1962 finish Jan 1967
Indefatigable start Feb1967 finish Sept 1971

Result in replacements being needed from the mid 70's to early 80's.

Arguably Implacable might receive the Victorious update, but Indefatigable would be cancelled or visa versa or indeed Indomitable might be bypassed as the two higher powered Implacables in this scenario offer better prospects.

CVA-01 or whatever emerges as a successor is going to dominate the 70's effort.
And notably while the likes of Sea Dart, Ikara and Broomstick are being incorporated into designs. They don't get implemented until the 70's.
 

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Two 1937 Carriers were ordered. Formidable and Indomitable.
The latter was a modified design, adding in a lower short hanger at the rear.
But what if it had been kept to just a repeat Illustrious?
Just a slight correction.. the lower hangar was NOT the add on.. the upper hangar was; hence its shorter height. The lower hangar was 16 feet the first half of it was converted into accommodation in the Indomitable because of the full length 14 foot upper hangars personal requirements.
 

uk 75

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Victorious illustrates the importance of matching carriers to the planes the RN wants them to carry.
She makes her final cruise with Sea Vixen and Buccaneer. But Sea Vixen is obsolete and the RN wants to replace it as soon as possible with F4.
Converting additional carriers in the 1950s or building new ones would not have altered this step change. The only real solution was an Audacious class conversion or a new design like CVA01.
The RN attempted to get an F4 that could operate from Hermes and in doing so saddled the UK with the most powerful but slowest F4 variant.
Other threads have discussed at lengths smaller alternatives to the F4 notably the F8 Crusader or various aircraft ranging from the SuperTiger to Bac VG designs that never left the drawing board.
The RN were right to want a new design even if CVA01 had some flaws. Ark Royal and Eagle were the only ships that could carry worthwhile loads with Eagle being the one that but for fate should have been chosen.
Victorious and the other I class ships were just too old and tired even if their conversion had been possible.
 

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The real missed opportunity was " a better low end to the Phantom, than the Crusader II".
Because the Phantom was too large for a) Essex, even SBC-125 b) Victorious c) Centaurs and d) Clem & Foch
- Alternative 1 - Crusader IV with J79
- Alternative 2 - Skylancer (also with J79)
- Alternative 3 - Super Tiger (had J79 from day one).
- Alternative 4: Northrop N-156N, but as with every F-5: lacks a valuable radar, AIM-9 only.
French and British alternatives would be
- SR.177
- Breguet 1120
... but one is rocket powered (partially) and the other is paper only...

One of the factors that caused the Implacables to be ruled out of modernisation was degree to which they were substantially different from Victorious. The 4 shaft and plant arrangement took up much more of the hull volume and this made the changes to how the modernisation could be implemented.
The limitations on hull height resulting in the modernisation forcing much greater bulging to retain stability. Which in turn effected predicted speed.
All with less than ideal results for hanger, potential for gallery deck and island size.

My feeling too. Those six ships (Illustrious and the five others) were a "rebuild death trap" and the RN could not really avoid falling into that trap.
- they were the "heavies" (unlike the Centaurs)
- and as the "heavies" they had to back the Audacious which were too few.

It is fascinating to think the RN at least tried one massive rebuild of a Centaur (Hermes) and one massive rebuild of Victorious.

What is pretty despairing is that, once BOTH were REBUILD at HORRIBLE expense of TIME and MONEY - both proved unable to operate Spey-Phantoms.

That, and Ark Royal poor material shape, are quite head-scratching conundrums.

There was no clear, easy path toward a balanced fleet of 2*Audacious AND 6*Illustrious half sisterships AND 4*Centaurs.
Not in 1945 not 1955 nor in 1960.

With perfect hindsight it was a complete nightmare.
 
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zen

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But Sea Vixen is obsolete and the RN wants to replace it as soon as possible with F4.
It wants to do that after the F4 becomes real. By which time the second such Carrier could be in process and too far gone to scrap.
‐-----
It needs be understood that from July 1953, the concentration was on Third World missions freeing the RN from coordinating aircraft policy with the USN (which had come to dictate it by sheer size). While cross decking was the ideal....it wasn't a base requirement.

And the significant decisions on Victorious were made June 1953 when it was already clear the 1952 CV effort was, like defence spending overall. Overly ambitious and in need of pruning back.

June 1952 is when the modernisation program was cut to just Victorious.

Now if Implacable is more like Victorious, and much more like her below the hanger (lower) deck, then the modernisation study is going to conclude it is much more achievable....In 1952.

The critical question would be when can she enter modernisation and the answer was (in 1952) 1956.

Now I'm slightly hazy on the precise details, but suspect that this isn't far off the point when Victorious's modernisation was less focused on hull and hanger and more focused on the new technologies incorporated into that hull.
So that the difficult task of stripping back Implacable below the hanger deck could begin.
---
Arguably this AH Implacable has the lower original Illustrious hanger as per Indomitable and the additional upper hanger. A revision would likely raise by one deck the new single hanger but leave room for a full gallery deck. Potentially there would be some 22ft of freeboard depending on the under hanger deck height needed. Arguably one might raise the UDH deck height to 10ft as per the 1952 design to accommodate supporting beams, flexible weapon stowage, vent trunks, piping, gearing etc. This would give something around 25ft of freeboard....enough for a deck edge lift. Giving room for full 151ft stroke catapults at the bow....possibly revised to 171ft stroke later on.

This also allows a gallery deck of 10.25ft to grow ship depth by 3ft to 76.75ft.
Only a modest bulge would be needed to keep stability margins.

This all makes the AH Implacable a more potent and capable carrier than Victorious. Faster, carrying at least 3-6 more aircraft and able to operate them at higher weights/lower WOD.
 

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Furthermore flipside of higher power plant is application on Centaurs and Irresistible/Audacious.
The extra power on four sets may induce a stretch to 764ft LWL as per limitations of facilities giving a figure of 820ft length of flight deck.....
However it's possible circa 1944 that a stretch of flight deck to 840ft might occur in the design as the new minimum was 838ft per Malta design debates.

While the Centaur might become 690ft LWL and 740ft FD.

The existence of such new low development risk plant is fundamental to the Malta design process and furthermore assusts decision processes for 1952 and Medium Fleet Carrier studies.

But had Implacable been so upgraded her replacement is needed 20 years after.
1987
And Indefatigable been completed 1971 pushes replacement to 1991.

All of which alleviate the pressure to complete CVA-01 design and build.
A delay in design process could alter the basis for decisions
 
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