Larger British light fleet carriers?

NOMISYRRUC

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Indeed, how would a larger Veinticinco de Mayo have served Argentina in 1982...assuming no change elsewhere.
Link to Post 109.
In May 1982 25 de Mayo deployed with

8x A4Q Skyhawk
4x S2E Tracker
2x S3D Sea King
2x Alouette III.

While her capacity may have been more the ability of the ARA to fill those slots is questionable. For example of 16 A4Q Skyhawks acquired in 1972 only 10 remained in service in 1982. Of 5 S3D in service in May 1982 only 3 were operational. Of 6 S2E in service only 5 were operational with only 4 deploying on the carrier at any one time.

The Argentinians only ordered 14 Super Etendards which were intended to replace not augment the Skyhawks remaining in service.

So you can begin to see how some of the figures quoted in earlier publications are arrived at. But whether that represents the actual intended embarked air group or not I don’t know.

With regard to the ARA and the SUE, ISTR reading somewhere recently that although they trained on the carrier, for which there are videos around on the net, their ability to carry a full weapons load was limited. I’ll try to remember where I saw it and dig it out.
Fair enough.

Is it possible that they'd have acquired more than 16 Skyhawks in 1972 because the larger version of VdM could accommodate more aircraft so more would be left in 1982. And a greater percentage of the total might be left in 1982 due to them being operated from a larger ship which might result in fewer aircraft being lost in accidents.

For what it's worth I know that the Super Etendards were intended to replace not augment the Skyhawks remaining in service, but presuming that they buy more than 14 to operate from the larger ship does that mean that more would have been delivered by April 1982? Does it also mean that more Exocets were ordered and more of them were delivered by April 1982?

For that it's worth what I've read on the net is that the weather was unusually calm so there wasn't enough wind-over-deck for the Skyhawks to take off with a full weapons load. However, Jordan wrote.
Problems with her catapult apparently hampered her participation in the campaign.
If that's true (and recent experience has told me not to believe what I read in books) maybe it was the faulty catapult that created the problem rather than the calm weather or even a combination of both.
 
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NOMISYRRUC

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Earlier in the thread I claimed that Hermes could be made to operate Phantoms and Victorious couldn't.

I might be wrong about this too.

This was based on information that I found in an RAF Air History Branch Narrative about the RAF from 1964 to 1970. It was discussing the events of 1965-66 that led to the February 1966 decision to abandon plans to build new strike carriers and withdraw the existing ones by the middle of the 1970s.

Amongst the options considered were some that reduced the number of ships from four to three, in which Victorious would be withdrawn, but Hermes would be retained and modified to carry the Phantom, such as this one from January 1966.
This would involved a major refit of Ark Royal between 1966 and 1969, and a limited purchase of Phantoms for the Fleet Air Arm. The Buccaneer would not be developed. Victorious would operate Sea Vixens until paid off in 1972, but the other three carriers would be modified to carry the Phantom F4K which would be deployed on Ark Royal from 1970, on Eagle from 1971 and on Hermes from 1973. Such an extension of the carriers until the mid 1970s would utilise the asset of the existing fleet and limit the gap in capability while political commitments continued.
If Hobbs information about the catapult capacities is correct (and I'm not sure that it is) Victorious and Hermes could launch aircraft of the same weight at the same end speed in spite of the former having shorter stroke catapults. Therefore, if Hermes could be adapted to operate Phantoms it looks like Victorious could have been too.

It's possible that Hermes was chosen instead of Victorious because she was newer. A secondary reason might have been that Hermes had a smaller crew of 2,200 against 2,400 for Victorious which is according to contemporary editions of Jane's Fighting Ships.
 
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zen

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In the end it comes down to g force limits on the airframe and pilot.
Normal quoted figures are predicated on not damaging to structure of the airframe.

Whereas we can see in Melbourne documentation that a 'warshot' option existed for launching the Skyhawk. But at a significant cost to airframe life. Such that it was effectively a one off act of desperation.

Between these extremes may lurk a low weight Fighter only F4K launch from Hermes.
 

NOMISYRRUC

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In the end it comes down to g force limits on the airframe and pilot.
Normal quoted figures are predicated on not damaging to structure of the airframe.

Whereas we can see in Melbourne documentation that a 'warshot' option existed for launching the Skyhawk. But at a significant cost to airframe life. Such that it was effectively a one off act of desperation.

Between these extremes may lurk a low weight Fighter only F4K launch from Hermes.
Is the g force determined by the stroke of the catapult?

145ft Victorious (both)​
151ft Hermes (port)​
151ft Ark Royal (bow)​
175ft Hermes (starboard)​
199ft Ark Royal (waist)​
The catapults on Victorious have a stroke that is only 6 feet shorter than the strokes of the port catapult on Hermes and the bow catapult on Ark Royal.
 

NOMISYRRUC

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Amongst the options considered were some that reduced the number of ships from four to three, in which Victorious would be withdrawn, but Hermes would be retained and modified to carry the Phantom, such as this one from January 1966.
This would involved a major refit of Ark Royal between 1966 and 1969, and a limited purchase of Phantoms for the Fleet Air Arm. The Buccaneer would not be developed. Victorious would operate Sea Vixens until paid off in 1972, but the other three carriers would be modified to carry the Phantom F4K which would be deployed on Ark Royal from 1970, on Eagle from 1971 and on Hermes from 1973. Such an extension of the carriers until the mid 1970s would utilise the asset of the existing fleet and limit the gap in capability while political commitments continued.
For what's its worth Hermes was deleted from this plan by 11th February 1966. Viz:-
The revised costed defence structure had meanwhile been prepared and was discussed by the DOPC on 11 February. Its main assumptions were retention of the existing carrier force, without CVA 01, as far into the 1970s as possible, provision of 50 F-111As, 55 Phantoms and 96 Buccaneers, preparation of Ark Royal and Eagle only to fly Phantoms, reduction of the Army to 176,000 and disbandment of the Gurkhas.
That's the plan they actually adopted in February 1966.

Except that another economic crisis led to Eagle not being Phantomised and the cancellation of the whole F-111A order, while the Phantom order was reduced from 55 to 48 and the Buccaneer order was cut from 96 to 84. (However, another 46 Buccaneers were ordered and built for the RAF while 4 more were ordered for the RAE, but only 3 of them were built.) Plus the Gurkhas weren't disbanded.

The 55 Phantoms did not include four ordered for the Ministry of Technology/Ministry of Defence (Procurement Executive) which produces the total of 59 YF-4K and F-4K that received British military serials. The actual number of YF-4K and F-4K built was 52.
 
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EwenS

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Indeed, how would a larger Veinticinco de Mayo have served Argentina in 1982...assuming no change elsewhere.
Link to Post 109.
In May 1982 25 de Mayo deployed with

8x A4Q Skyhawk
4x S2E Tracker
2x S3D Sea King
2x Alouette III.

While her capacity may have been more the ability of the ARA to fill those slots is questionable. For example of 16 A4Q Skyhawks acquired in 1972 only 10 remained in service in 1982. Of 5 S3D in service in May 1982 only 3 were operational. Of 6 S2E in service only 5 were operational with only 4 deploying on the carrier at any one time.

The Argentinians only ordered 14 Super Etendards which were intended to replace not augment the Skyhawks remaining in service.

So you can begin to see how some of the figures quoted in earlier publications are arrived at. But whether that represents the actual intended embarked air group or not I don’t know.

With regard to the ARA and the SUE, ISTR reading somewhere recently that although they trained on the carrier, for which there are videos around on the net, their ability to carry a full weapons load was limited. I’ll try to remember where I saw it and dig it out.
Fair enough.

Is it possible that they'd have acquired more than 16 Skyhawks in 1972 because the larger version of VdM could accommodate more aircraft so more would be left in 1982. And a greater percentage of the total might be left in 1982 due to them being operated from a larger ship which might result in fewer aircraft being lost in accidents.

For what it's worth I know that the Super Etendards were intended to replace not augment the Skyhawks remaining in service, but presuming that they buy more than 14 to operate from the larger ship does that mean that more would have been delivered by April 1982? Does it also mean that more Exocets were ordered and more of them were delivered by April 1982?

For that it's worth what I've read on the net is that the weather was unusually calm so there wasn't enough wind-over-deck for the Skyhawks to take off with a full weapons load. However, Jordan wrote.
Problems with her catapult apparently hampered her participation in the campaign.
If that's true (and recent experience has told me not to believe what I read in books) maybe it was the faulty catapult that created the problem rather than the calm weather or even a combination of both.
In “Carrier at Risk” Mariano Sciaroni quotes the ship’s Operations Officer and several pilots who all blame the lack of wind (and the lack of ship’s speed) with no mention of a faulty catapult.

The whole attack operation was planned around risk and reward. Taking off in the early morning, 6xA-4Q each carrying 4x500lb Mk82 bombs would launch plus one with a buddy refuelling pack in case someone needed more fuel to get back to the carrier. That left one spare in case of unserviceability. From that the expectation was that 2 would be lost penetrating the task force screen, 4 Bomb hits (25%) would be achieved and 2 more would be lost on the way out. And one carrier would be put out of action.

As the wind dropped, the proposed bomb loads fell to 3 and then 2 per aircraft. So the expectation was then 2 hits for the loss of 4 aircraft. At that point the risk was not felt to be worth the potential reward and the mission was scrubbed.

Added to that in the interim the 25 de Mayo had been discovered by the British so heightening the risk side of the equation further.
 

Archibald

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Yup I remember reading a British nuclear sub had it in its crosshairs and was ready to pull a Belgrano on VdM
(in passing: that accronym you use, VdM, amuses me to no end.
Reminds me of that website https://www.viedemerde.fr/ "Vie De Merde = shitty life.)
 

zen

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Is the g force determined by the stroke of the catapult?
To a degree yes, but acceletion is mostly limited by airframe strength and human factors.
Bear in mind to overcome inertia and friction, initial acceleration is +30g, and rapidly reduced to 4-5g in the course of less than a second.
 

Archibald

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I checked MTOW of the A-7E SLUF and it was 42 000 pounds, which is more or less exactly 19 metric tons.
I checked the A-7E landing speed: 139 mph is 120 kt.

Further search showed the Clemenceau / Foch 171 ft long BS-5 could throw a maximum of 20 mt to 110 kt.

It is not hard from these numbers to see how A-7E were at the edge of Clemenceau carriers capabilities... and Hornet, beyond them.
 

EwenS

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Yup I remember reading a British nuclear sub had it in its crosshairs and was ready to pull a Belgrano on VdM
(in passing: that accronym you use, VdM, amuses me to no end.
Reminds me of that website https://www.viedemerde.fr/ "Vie De Merde = shitty life.)
On 29th April Splendid detected the 2 Type 42s and the 3 A69 corvettes but not the carrier. He got to within 14,000 yards of them. But the RoE in place at that time did not allow him to attack. The real prize was the carrier however,

Then the RoE were changed on 30th April and he continued to track the escorts in the hope they would lead him to the big prize, the carrier. He was then ordered south (orders he initially ignored) towards a position where the carrier was supposed to be but it was over 100 miles to the north at the time.

Splendid didn’t locate the carrier and escorts on sonar until early on 3 May when they were well within Argentinian territorial waters, and heading north, which were out of bounds under the RoE. He trailed her, on sonar only, until late on 5th May when he had to withdraw to effect machinery repairs that couldn’t be put off any longer.

Funnily enough by that time the weather had changed and it was blowing a Force 12 gale with mountainous seas! So there was too much wind for a strike if the Argentinians had ever considered launching one.

See “The Silent Deep” by Peter Hennessy & James Jinks.

“Carrier at Risk” notes that Splendid actually spent part of her time chasing a tanker not the carrier! The Argentinian Trackers flew AS sorties throughout these few days, finally detecting a PROBSUB target on the 5th which they attempted to prosecute along with the Sea Kings, even launching a Mk.44 torpedo.

The mystery is that this doesn’t seem to have been Splendid but some other submarine operating in these waters. Splendid also detected this mystery sub.
 

BlackBat242

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Link to Post 109.
Link to Post 113.
Thanks for that.

If I'd looked at the drawings of Karel Doorman/VdM and Minas Gerias in my copy of Friedman before typing my post I'd have saved you a lot of work. For what its worth I know about Melbourne having her catapult lengthened in 1971.

Bearing in mind how extensively those ships were modified, what do you think they'd have done with them if they'd been Centaur class ships instead of Colossus class ships? Particularly the catapults and the lifts?

And have you acquired any information on the catapults on Clemenceau and Foch?

Well, I'm not sure what the Dutch (who were in charge of both modernizations in the 1950s) would have done with Centaurs, but I have done a similar modernization for an alternate-history Australia that picked up a pair of the Centaurs in the 1960s.

Here is my drawing for that... note the faint outline for the hangar and the drawing of the shops area to port of and forward of the fore lift (which I moved to starboard as per MG).

This narrowed the forward extension of the hangar from 62' to 47'.

The port bow cat looks unable to be lengthened past the 145' I made it... but the angle deck catapult could be lengthened (especially forward, if a bridle catcher extension is added) to at least 151'.

My drawing did not show any radar changes, but better radars with larger antennae would be fitted.

RAN mod Albion Bulwark 2af.PNG


And the class as historic in 1958:

Albion Bulwark Centaur 1958.gif


Note that my A-H included a slightly larger & heavier navalized Gnat and the Super Tiger both entering Australian service (along with the RAAF buying Drakens instead of Mirage IIIs).

I can post all of the write-ups in their own thread in the appropriate section if there is interest.
 

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Archibald

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Australia was quite interested in the Mirage G circa 1968, and so was the USN, who point-blank asked Dassault to build three more for an experimental squadron at Patuxent River. Dassault sadly did not thought the offer was serious (and it wasn't fully serious indeed).

Google books snipets of France interest in the A-7E, circa 1972 when the Jaguar M trials proved it was hopeless. Clearly the A-7E was too much for Foch and Clem', Skyhawk A-4M were prefered.

And now I found the reason why Etendard IV & Crusaders were not replaced together, circa 1972, by a multirole supersonic type.
The cash starved Aéronavale made a choice.
What mattered most for the carrier force was to strike targets in French Africa. There was no serious threat such as supersonic fighters there... in a few words, Crusaders could do the job. And that's the reason why Super Etendard happened (and the alternative: Jaguar M / A-7E / A-4M / Harrier).
 

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Hood

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There was another potential candidate for an earlier Large Light Fleet - adapting HMS Unicorn's design.

The hangars were:
Upper - 324 x 65 x 16.ft 6in
Lower - 360 x 62 x 16ft 6in
The aircraft capacity (ignoring the crated aircraft) was 7 aircraft (wings spread) in the upper and 20 lower (folded). As a training carrier capacity was 30 aircraft or 20x Albacores in wartime. She lacked sufficient cabin accommodation to embark two Albacore squadrons though but there was space to provide this. She had workshops and stowage for 50 spare engines (4x more than Ark Royal carried). She had magazines for 240x 250lb SAP bombs, 240x 100lb A/S bombs and 30x torpedoes (removed in final design for more workshops).

At 575ft WL length she was about 100ft shorter than the Colossus but 10ft wider, slightly slower at 24.75kts (24kts deep) on 40,000hp. Displacement was similar, Unicorn being 800 tons more but she did have 4.5in guns and 950s tons of armour, including 2in on the flight deck to resist 250lb bombs.
Two accelerators could have been fitted had some of the workshop space forward of the upper hangar been sacrificed.
Laid down 30 March 1939 at Harland and Wolff, on 25 April it was decided to complete her as a carrier with only a third of her planned maintenance facilities, launched 20 November 1941, completed 12 March 1943 = 49 months
In 1945 she was converted back to a maintenance ship for the British Pacific Fleet.
Her completion was evidently slowed due to her relatively low priority during the 1940 panic months until it was decided to complete her as a carrier.

So that gives the AH option of a 1941/42 order for more Unicorns with two accelerators and reduced depot ship facilities with around 20-30 aircraft.

A 'cut down' Unicorn with the upper hangar deck removed, 20 aircraft, 24.75kts, retaining 4in guns etc. and the 2in flight deck armour too, should be quicker to build and cheaper and might be possible but its hard to see what it brings over the 1942 Light Fleet in reality, especially given its 100ft shorter so ultimately has much less growth potential.
 
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NOMISYRRUC

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Dear gosh...

At the end of the day, with Victorious having the right size but wrong catapults, and Hermes being the opposite (!) the only valuable carriers were the Audacious. Unfortunately Ark Royal was crippled, so that leaves Eagle as the one and only carrier from 1945 to 1980 worth modernizing...
because it is the one and only
- big enough, unlike Hermes
- with the correct catapults, unlike Victorious
- and not an ailing wreck in poor material shape like Ark Royal
I listened to Drachinifel's Dry Dock Episode 198 last week.

About 30 minutes in he answered a question about Ark Royal and Eagle in which he clamed that the former's poor material condition was due to her hull not being preserved properly, when she was laid up after the war, which allowed a lot of water to get into places where it shouldn't, which in turn created a lot of issues that weren't entirely solved.

If that's correct Ark Royal's material problems would have been avoided by preserving her hull properly after the war.

If Drachinifel's claim is wrong and therefore my conclusion is wrong I'm sure we'll be corrected. And fair enough. Drachinifel got the dates of Ark Royal and Eagle's big refits wrong and he was also wrong about why Ark Royal was Phantomized and Eagle wasn't. If he was wrong about that he could also be wrong about this.
 

NOMISYRRUC

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Bottom line: shame they didn't build that third Audacious back in 1945. Because, you see, the Audacious (with perfect hindsight) were the one and only carriers able to go from F4U Corsairs and Seafires to... Phantoms (!) in merely twenty years (!!): 1946-1966 !
"I must decline your offer with thanks, for the child might have my beauty and your brains."

http://yquotes.com/george-bernard-shaw/131132/#ixzz7UmRZKscZ

What if the Third Audacious was completed? Is one of the great questions of alternative naval history.

However... What if the ship shared the material defects that plagued Ark Royal?

The alternative naval historians of that timeline might be writing treatises on how it should have been broken up on the stocks in 1946 and the money saved should have been used to build a new ship of similar capabilities or even to rebuild one of the older armoured carriers because they would not have known what we know about Victorious.
 

Archibald

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What if the ship shared the material defects that plagued Ark Royal?
"The horror, the horror"
and
"Be careful what you wish for"
 

GK Dundas

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What if the ship shared the material defects that plagued Ark Royal?
"The horror, the horror"
and
"Be careful what you wish for"
One of the reasons the RCN's midlife refit on the Bonnie went from roughly 4 million dollars to 17 million was they really opened her up.
And found an incredible amount of corrosion. Apparently the shipyards concept of corrosion management consisted of either a coat of paint over it or walling it up and hoping the Customer never noticed it.
During the fifties and sixties the phrase fine British craftsmanship in shipbuilding became an oxymoron it seems.
 
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H_K

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I have done a similar modernization for an alternate-history Australia that picked up a pair of the Centaurs in the 1960s.
RAN mod Albion Bulwark 2af.PNG

Amazing drawing… this is almost exactly what I had in mind for a « 3 Centaur » or « 4 Centaur » Royal Navy for the 1960s/70s!

(As opposed to Victorious rebuild, Eagle modernization + Ark Royal Phantomization).

I had wondered about moving the rear elevator to the starboard deck edge behind the island, Clemenceau style, but the benefits (larger hangar) may not be worth the effort.

I go back & forth on the optimal air group… either 2 types (e.g. 12 fighter + 8 bomber, e.g. Spey Twosaders + Buccaneers), or 1 multirole type. By the 80s with F/A-18s this would have looked good in RAN service.
 

zen

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Yes larger Centaurs were possible.
If they used two of the Malta sets of plant from 1944.
Or the decision to pursue such 40,000shp+ plant had been taken in 1938.
 

bobtdwarf

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There was another potential candidate for an earlier Large Light Fleet - adapting HMS Unicorn's design.

The hangars were:
Upper - 324 x 65 x 16.ft 6in
Lower - 360 x 62 x 16ft 6in
The aircraft capacity (ignoring the crated aircraft) was 7 aircraft (wings spread) in the upper and 20 lower (folded). As a training carrier capacity was 30 aircraft or 20x Albacores in wartime. She lacked sufficient cabin accommodation to embark two Albacore squadrons though but there was space to provide this. She had workshops and stowage for 50 spare engines (4x more than Ark Royal carried). She had magazines for 240x 250lb SAP bombs, 240x 100lb A/S bombs and 30x torpedoes (removed in final design for more workshops).

At 575ft WL length she was about 100ft shorter than the Colossus but 10ft wider, slightly slower at 24.75kts (24kts deep) on 40,000hp. Displacement was similar, Unicorn being 800 tons more but she did have 4.5in guns and 950s tons of armour, including 2in on the flight deck to resist 250lb bombs.
Two accelerators could have been fitted had some of the workshop space forward of the upper hangar been sacrificed.
Laid down 30 March 1939 at Harland and Wolff, on 25 April it was decided to complete her as a carrier with only a third of her planned maintenance facilities, launched 20 November 1941, completed 12 March 1943 = 49 months
In 1945 she was converted back to a maintenance ship for the British Pacific Fleet.
Her completion was evidently slowed due to her relatively low priority during the 1940 panic months until it was decided to complete her as a carrier.

So that gives the AH option of a 1941/42 order for more Unicorns with two accelerators and reduced depot ship facilities with around 20-30 aircraft.

A 'cut down' Unicorn with the upper hangar deck removed, 20 aircraft, 24.75kts, retaining 4in guns etc. and the 2in flight deck armour too, should be quicker to build and cheaper and might be possible but its hard to see what it brings over the 1942 Light Fleet in reality, especially given its 100ft shorter so ultimately has much less growth potential.
there is a lot of potential in a Unicorn variant or a ship based on an expanded Unicorn. She is as is a viable commando ship waiting to happen
 

BlackBat242

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I have done a similar modernization for an alternate-history Australia that picked up a pair of the Centaurs in the 1960s.
RAN mod Albion Bulwark 2af.PNG

Amazing drawing… this is almost exactly what I had in mind for a « 3 Centaur » or « 4 Centaur » Royal Navy for the 1960s/70s!

(As opposed to Victorious rebuild, Eagle modernization + Ark Royal Phantomization).

I had wondered about moving the rear elevator to the starboard deck edge behind the island, Clemenceau style, but the benefits (larger hangar) may not be worth the effort.

I go back & forth on the optimal air group… either 2 types (e.g. 12 fighter + 8 bomber, e.g. Spey Twosaders + Buccaneers), or 1 multirole type. By the 80s with F/A-18s this would have looked good in RAN service.
Unlike the Colossus/Majestic class, the hangar floor (freeboard) in the Centaurs was just barely high enough for the RN to agree to the deck-edge lift... 23' 6". Hermes had issues with this... here is a comment from a former crewmember of Hermes (hermes82 on Navweaps):
Hermes fwd lift was a deck edge side lift.
It was pretty dangerous in choppy weather nearly got washed over the side on at least 2 occasions, really thought I was a goner.
My mate was the lift driver at flight deck level he got submerged by one wave whilst we stuck a cab on it, you can imagine how wet we were.
The lift acted like a knife blade through the water when it was at hangar level damaged the cab as well.
An aft-mounted deck-edge elevator would be not quite as vulnerable to wave action (due to the greater flotation of the aft hull riding over the waves easier than the bow), but a low-freeboard can still cause issues.
For example, USS Midway lost her starboard deck-edge elevator (aft of the island) in early 1964:
During an underway replenishment, MIDWAY's number 3 aircraft elevator is hit and lifted by a large wave. Parts of the wave also wash over the elevator almost washing several crewmembers into the sea. A subsequent large wave lifts the elevator again and breaks it from its guides. As a result the cables snap and the elevator falls into the sea. MIDWAY got a new elevator in June 1964 during a yard period at Hunters Point Shipyard at San Francisco, Calif.


The issue with adding deck-edge elevators to the first 3 Centaurs is that the Centaurs were built with the hangar sides (out to the hull side) as an essential part of the hull girder - essential to prevent the hull from bending as the ship rides over waves in heavy seas.

That was the reason for Hermes' completion & modernization to take so very long compared to the others... they had to redesign and rebuild the lower port hull under, forward, and aft of the deck-edge elevator opening, to replace the lost hull strength from the elevator opening being cut out of the hangar side. Trying to do that with a completed Centaur, whether with the fore lift or the aft, would be more expensive & time-consuming than Hermes' work while still completing.

Centaur: Laid down 30 May 1944, construction delayed following WWII, launched 22 April 1947, commissioned 17 Sept 1953.

Albion:
Laid down 22 March 1944, construction delayed following WWII, launched 6 May 1947, commissioned 6 May 1954.

Bulwark:
Laid down 10 May 1945, construction delayed following WWII, launched 22 June 1948, commissioned 29 October 1954.

Hermes:
Laid down 21 June 1944, renamed 11/1945, construction suspended following WWII. Construction resumed 1952 and launched 16 Feb 1953 and work again suspended until resumed in 1957 to completely reworked design, commissioned 25 Nov 1959.
 
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Archibald

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That was the reason for Hermes' completion & modernization to take so very long compared to the others... they had to redesign and rebuild the lower port hull under, forward, and aft of the deck-edge elevator opening, to replace the lost hull strength from the elevator opening being cut out of the hangar side. Trying to do that with a completed Centaur, whether with the fore lift or the aft, would be more expensive & time-consuming than Hermes' work while still completing.

Okaaaay.... so that's the reason why Hermes evolved differently from its three siblings. Well noted...

And 1952-1959 rebuild ? Wow, nearly as long as Victorious. Just to get another one-shot finally unable to handle Spey-Phantoms. dear Gosh.
 

BlackBat242

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That was the reason for Hermes' completion & modernization to take so very long compared to the others... they had to redesign and rebuild the lower port hull under, forward, and aft of the deck-edge elevator opening, to replace the lost hull strength from the elevator opening being cut out of the hangar side. Trying to do that with a completed Centaur, whether with the fore lift or the aft, would be more expensive & time-consuming than Hermes' work while still completing.

Okaaaay.... so that's the reason why Hermes evolved differently from its three siblings. Well noted...

And 1952-1959 rebuild ? Wow, nearly as long as Victorious. Just to get another one-shot finally unable to handle Spey-Phantoms. dear Gosh.
Well, the info I posted does mention a second construction suspension from after her 1953 launch until 1957.

This was apparently the period where they did all of the detailed design work for the structural and equipment changes.
 

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The issue with adding deck-edge elevators to the first 3 Centaurs is that the Centaurs were built with the hangar sides (out to the hull side) as an essential part of the hull girder - essential to prevent the hull from bending as the ship rides over waves in heavy seas.

The Centaurs had a traditional RN closed hangar with the hangar itself fully contained with the shell of the hull. So the hull had a waterline beam of 90ft and the hangar was 62ft wide with compartments down both sides between the hangar walls and the outside plating of the hull. There are sectional drawings of Centaur as completed in Friedman's "British Carrier Aviation" showing this.


That was the reason for Hermes' completion & modernization to take so very long compared to the others... they had to redesign and rebuild the lower port hull under, forward, and aft of the deck-edge elevator opening, to replace the lost hull strength from the elevator opening being cut out of the hangar side. Trying to do that with a completed Centaur, whether with the fore lift or the aft, would be more expensive & time-consuming than Hermes' work while still completing.
In Hermes the hangar remained 62ft wide, so the cut required to install the side lift went through the hull side, the compartments inside that and then through the hangar wall. So yes substantial reinforcement was required. This was the same issue as arose with Ark Royal, where the side lift only served the upper hangar. Here is a photo of Viraat (ex Hermes) being broken up.

1653980953945.png
Centaur: Laid down 30 May 1944, construction delayed following WWII, launched 22 April 1947, commissioned 17 Sept 1953.

Albion:
Laid down 22 March 1944, construction delayed following WWII, launched 6 May 1947, commissioned 6 May 1954.

Bulwark:
Laid down 10 May 1945, construction delayed following WWII, launched 22 June 1948, commissioned 29 October 1954.

Hermes:
Laid down 21 June 1944, renamed 11/1945, construction suspended following WWII. Construction resumed 1952 and launched 16 Feb 1953 and work again suspended until resumed in 1957 to completely reworked design, commissioned 25 Nov 1959.
Photo of the islandless Centaur & Bulwark laid up at Harland & Wolff Belfast in late 1940s with Eagle on the other side of the pier during her completion.

1653981902829.png

Centaur was docked for a bottom clean and repaint in Oct 1949 and construction restarted in 1951 (McCart "HMS Centaur 1943-1972". But did it really restart so late?)

After launch Albion was laid up on the Tyne. She too got a bottom clean in 1949 (at Rosyth and suffered collision damage in the process) before construction restarted back at Swan Hunter in early 1950. At the time she was laid up she too was islandless and with gaping holes in the flight deck where the lifts would later be installed.

These ships were launched in order to clear the slips in the yards for construction of merchant ships.

According to McCart "HMS Hermes 1959-1984" all work on Hermes (ex Elephant) stopped at the end of the war. "On the date when work stopped on the Hermes the shell was up to middle deck level and the main internal bulkheads had been completed. For the next three years little other than maintenance work was done, including continuously coating the steelwork with oil."

There was then a decision in 1949 to complete her to the launching stage in order to clear the slip for merchant shipbuilding. She was launched on 16 Feb 1953. A new Staff Requirement for her was approved in 1954 and another, the final one, on 26 March 1957 before she completed in Nov 1959.

Famous photo of Ark Royal just befor her launch in 1950
1653984850446.png

This photo of Ark Royal shows just how far from the ship's side the side lift opening had to penetrate to reach the hangar side.
1653985222150.png
 

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Interestingly modernised existing or new build modified design Centaurs were on the RANs wish list in the early 60s, as was the CVA-01 and modernised Essex.
 

zen

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An intriguing thought occurs.
If one wanted more Hermes-like Centaurs.
Then having them stop work at a similar state of completion in 1945 is the theoretical mechanism for them to be completed like Hermes.
 

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Out of interest... What were the material defects that plagued Ark Royal?
built with wartime grade steel... she was a ball of rust waiting to happen at the very least and at the worst prone to early metal fatigue/cracking
There was this comment up thread about Bonaventure.
One of the reasons the RCN's midlife refit on the Bonnie went from roughly 4 million dollars to 17 million was they really opened her up.

And found an incredible amount of corrosion. Apparently the shipyards concept of corrosion management consisted of either a coat of paint over it or walling it up and hoping the Customer never noticed it.
During the fifties and sixties the phrase fine British craftsmanship in shipbuilding became an oxymoron it seems.
Do you know whether "being a ball of rust waiting to happen" was a problem faced by many British warships that were built with wartime grade steel?

As far as I know Albion, Bulwark, Centaur, Eagle and Hermes didn't have that problem, but as I know next-to-nothing about the subject it could be due to ignorance on my part. Hermes herself was an operational warship into the 2010s and some of the Colossus/Majestic class were in service for several decades.

What started this off was the statement made by Drachinifel in his Dry Dock Episode 198. That is Ark Royal's poor material condition was due to her hull not being preserved properly, when she was laid up after the war, which allowed a lot of water to get into places where it shouldn't, which in turn created a lot of issues that weren't entirely solved.

He attributed Eagle's better material condition to being launched relatively soon after laying down. (So were all but 2 of the British aircraft carriers that were laid down during the war. The exceptions were Ark Royal and Hermes). Eagle was launched 41 months after being laid down while Ark Royal was launched 84 months after being laid down which is twice as long. (Dates are according to Conway's 1922-46.)

However, Hermes was on the stocks for even longer than Ark Royal (104 months). If she did have severe corrosion problems they didn't stop her remaining in service for the thick-end of 60 years (1959-2017 according to Wikipedia). That or she didn't have them in the first place due to her hull being preserved properly and/or her hull had less wartime grade steel in it because she was laid down 14 months after Ark Royal which might have meant that her hull was less complete when she was laid up.

Ark Royal was built by Cammell-Laird, while Hermes was built by Vickers-Armstrong at Barrow-in-Furness. Could that have been a factor in the ships having better quality hulls? Was the latter have been better at preserving hulls than the former? The other Eagle was also being built by Vickers-Armstrong, albeit at their Tyne yard. If Vickers-Armstrong was better at preserving hulls than Cammell-Laird then the other Eagle might not have had the material defects that plagued Ark Royal.
 

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Interestingly modernised existing or new build modified design Centaurs were on the RANs wish list in the early 60s, as was the CVA-01 and modernised Essex.
For what its worth the files are available on the National Archives of Australia website. Amongst other things they discuss how large the crews will be and the extra men required ashore.
 

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Some questions for @BlackBat242 because I regard you as our resident catapult expert.

Earlier in the thread I suggested that Victorious had shorter catapults than Hermes, because the former ship didn't have enough space between the bow and the forward lift for anything longer.

Is that correct?

The reason I ask the question is that Victorious and some of the other aircraft carriers had hangar extensions between the forward lift and the bow. Did the hangar extensions limit the length of the steam catapults on these ships too? My guess is yes it does because you wrote the following in Post 131.
Well, I'm not sure what the Dutch (who were in charge of both modernizations in the 1950s) would have done with Centaurs, but I have done a similar modernization for an alternate-history Australia that picked up a pair of the Centaurs in the 1960s.

Here is my drawing for that... note the faint outline for the hangar and the drawing of the shops area to port of and forward of the fore lift (which I moved to starboard as per MG).

This narrowed the forward extension of the hangar from 62' to 47'.
Is my guess correct?

Finally... Do you have any statistics on the catapults fitted to Clemenceau and Foch? I.e. total length, stroke/shuttle run, the launch weights and end speeds?
 

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That would be welcome indeed, because "15 to 20 metric tonnes to 110 kt" is pretty vague... as far as throw weight is concerned.
 

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It may be a statement of the obvious but rust/corrosion of exposed steel is a chemical reaction that begins very very quickly. Check out the brake discs on you car if it is left sitting in damp conditions for a day or so. They will have turned a nice orange rust colour. Leave it for longer and the discs will begin to pit as the corrosion eats into them.

Looking at ships built in WW2 I have read that the build quality was not that of pre-war built ships. That applied across the board, not just to carriers. It has been referred to by various authors over the years. But the pressure was to get ships completed and into service quickly for this war without any real regard to their longevity. So, for example, the warbuilt cruisers of the Dido/Fiji classes did not fair so well as the Town class in the corrosion stakes in postwar years. I have a photo in a book of the WW2 destroyer Vigilant undergoing conversion to a Type 15 frigate (between mid-1951 and mid-1953). About the lowest one third of her underwater hull plates have been removed. That was in a ship laid down in Jan 1942, launched in Dec and completed in Sept 1943, so in the water for less than 10 years.

But severe corrosion was not confined to wartime builds. "Rebuilding the Royal Navy" by DK Brown and George Moore on p180 refers to the frigate Rothesay (built 1956-60) being found to "have fourteen longitudinals on one side and nine on the other so badly corroded as to be virtually useless - it was lucky she did did not break in half." He blames machinery spaces that were warm and moist in steam powered ships and many bilge spaces being almost inaccessible.

There were multiple problems. In some cases steel was not necessarily of the same quality as pre-war, containing less in the way of elements that aid corrosion resistance (eg chromium) due to wartime shortages. There were also issues arising from the quality of construction that varied from yard to yard. I recall reading a long time ago that the first CO of the new cruiser Bellona thought seriously about not taking delivery of the ship in Oct 1943 due to worries about some of the workmanship. With the pressure in the yards undoubtedly corners did get cut. And disgruntled workforces only added to the problems.

With regard to Hermes, note my comment about the metalwork being oiled while she remained suspended. I don't know if the same care was taken with the Ark Royal which was also left sitting on the slip for years. Certainly so long as the steel remained unpainted it remained in greater danger of the dreaded tin worm. And in that respect the other 3 had a distinct advantage. And again my notes about Centaur & Albion getting a bottom clean and repaint before construction restarted.

Brown/Moore note that significant developments in paint and the preparation for painting only begin about 1960 and add to the cost of the ship (2-3%). They point out that in 1982 Falklands War Hermes was the only ship originating in WW2 and was noticably more rusty that any other on her return.
 

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Some questions for @BlackBat242 because I regard you as our resident catapult expert.

Earlier in the thread I suggested that Victorious had shorter catapults than Hermes, because the former ship didn't have enough space between the bow and the forward lift for anything longer.

Is that correct?

The reason I ask the question is that Victorious and some of the other aircraft carriers had hangar extensions between the forward lift and the bow. Did the hangar extensions limit the length of the steam catapults on these ships too? My guess is yes it does because you wrote the following in Post 131.
Well, I'm not sure what the Dutch (who were in charge of both modernizations in the 1950s) would have done with Centaurs, but I have done a similar modernization for an alternate-history Australia that picked up a pair of the Centaurs in the 1960s.

Here is my drawing for that... note the faint outline for the hangar and the drawing of the shops area to port of and forward of the fore lift (which I moved to starboard as per MG).

This narrowed the forward extension of the hangar from 62' to 47'.
Is my guess correct?

Finally... Do you have any statistics on the catapults fitted to Clemenceau and Foch? I.e. total length, stroke/shuttle run, the launch weights and end speeds?
When Victorious was reconstructed the forward end of the forward lift space was moved aft by some 21 frames. The catapult rooms (immediately under the rear end of the catapults themselves) and catapult pump room (sandwiched between the two catapult rooms) were on the upper gallery deck, immediately forward of the lift, and took up most of the width of that deck at that point. Those compartments actually occupy space above the A hangar extension forward of the lift space.

So there would be two choices to extend the catapults. Move the forward lift even futher aft and letting it encroach on the landing area itself and not being just over the safety line. Or remove the two forward 3" gun turrets to allow the catapult rooms to be moved outboard, allowing the catapults to be angled down each side of the forward lift. You then run into the problem that the port catapult and its associated jet blast deflectors will encroach even further on the angled landing area while the starboard catapult will run closer to the front of the bridge so making it harder, if not impossible, to load aircraft and then where do you put the JBD because the bridge is in the way.. And you can't move the island back because of the funnel uptakes.

And that is before taking account of any structural weakening of the hull girder by having the lift opening nearer the centre of the ship. Victorious' hull was not deemed deep enough to fit a side lift. The problem being the height of the hangar floor above the waterline.

See all the boxes on the deck outlined in this photo.

1654000450536.png

The forward hangar extension itself is the same width as the main hangar - 62ft 6in. There are however obstructions along half the port side and the forward end for shelving.

See "Anatomy of the Ship The Aircraft Carrier Victorious" by Ross Watton.
 

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Do you have any statistics on the catapults fitted to Clemenceau and Foch? I.e. total length, stroke/shuttle run, the launch weights and end speeds?
From French sources, the stroke length was 157ft (47.85m).

In 1962, launch capability was quoted as 33,000lb (15t) @ 110kts / 3.6g or 40,000lb (18.15t) @ 100kts / 3g. This appears to include a safety margin of ~3 knots and translates to a launch energy of ~25MJ.

Later launch capability was quoted as 14t @ 125kts. This translates to 4.4g and ~29MJ, ie. a 15% increase, probably from increasing the steam accumulator pressure slightly.

 

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Archibald

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In 1962, launch capability was quoted as 33,000lb (15t) @ 110kts / 3.6g
That's 15 metric tons thrown at 110 kt
or 40,000lb (18.15t) @ 100kts / 3g.
18 metric tons at 100 kt.

Fits with my previous numbers but greatly refines them... downwards, unfortunately.

Also confirms that a 42 000 pounds (19 metric tons) MTOW A-7E was on the upper edge of these catapults capabilities.
Also makes Hornets looks even more marginal. Not even mentionning Phantoms.

And 14 tons thrown at 125 kts ? Mirage F1, Atar and ground-based could land at 125 kts but weighed 37 000 pounds, MTOW (16.5 metric tons)

Guess that explains why they stuck with Super Etendard and nothing bigger of faster: they instantly ran into the catapult limits: 125, 110 and 100 kt throw weights shrunk fast.

No surprise either the Crusaders were "hot" even with BLC. Out of 42 more than half were lost (bottom of that page).
 

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zen

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151ft is 46m
177ft is 54m
199ft is 60.7m
210ft is 64m
250ft is 76.2m

Pressure figures seem off.
I thought BS.4 and BS.5 used 450psi
Though the 1952 studies include 650psi.

157ft seems a curious figure.
 

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The RN carriers boilers were as follows:
Colossus, Majestic, Centaur, Audacious (Eagle & Ark Royal)
8 Admiralty 3-drum; 400 psi; 700°

Victorious (1958+)
6 Foster Wheeler; 440 psi; 750°

Here are the RN boilers for newer ships (the Darings are likely the standard considered for the 1952 carrier studies):
Daring (1949)
2 Y102A 1-drum (Foster-Wheeler); 650 psi; 850°

County (DDG)
2 Y102A 1-drum (Babcock & Wilcox); 700 psi; 950°



Clemenceau & Foch's boilers were:
6 Indret; 640 psi (45kg/cm), superheat 842°F (450°C).
 
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There was another potential candidate for an earlier Large Light Fleet - adapting HMS Unicorn's design.

The hangars were:
Upper - 324 x 65 x 16.ft 6in
Lower - 360 x 62 x 16ft 6in
The aircraft capacity (ignoring the crated aircraft) was 7 aircraft (wings spread) in the upper and 20 lower (folded). As a training carrier capacity was 30 aircraft or 20x Albacores in wartime. She lacked sufficient cabin accommodation to embark two Albacore squadrons though but there was space to provide this. She had workshops and stowage for 50 spare engines (4x more than Ark Royal carried). She had magazines for 240x 250lb SAP bombs, 240x 100lb A/S bombs and 30x torpedoes (removed in final design for more workshops).

At 575ft WL length she was about 100ft shorter than the Colossus but 10ft wider, slightly slower at 24.75kts (24kts deep) on 40,000hp. Displacement was similar, Unicorn being 800 tons more but she did have 4.5in guns and 950s tons of armour, including 2in on the flight deck to resist 250lb bombs.
Two accelerators could have been fitted had some of the workshop space forward of the upper hangar been sacrificed.
Laid down 30 March 1939 at Harland and Wolff, on 25 April it was decided to complete her as a carrier with only a third of her planned maintenance facilities, launched 20 November 1941, completed 12 March 1943 = 49 months
In 1945 she was converted back to a maintenance ship for the British Pacific Fleet.
Her completion was evidently slowed due to her relatively low priority during the 1940 panic months until it was decided to complete her as a carrier.

So that gives the AH option of a 1941/42 order for more Unicorns with two accelerators and reduced depot ship facilities with around 20-30 aircraft.

A 'cut down' Unicorn with the upper hangar deck removed, 20 aircraft, 24.75kts, retaining 4in guns etc. and the 2in flight deck armour too, should be quicker to build and cheaper and might be possible but its hard to see what it brings over the 1942 Light Fleet in reality, especially given its 100ft shorter so ultimately has much less growth potential.
From a pilot’s perspective trying to land on Unicorn was far from ideal due to her Aircraft Maintenance Ship origins. The shape of her hull and flight deck aft generated wind shear effects on aircraft crossing her stern. It has been described as like “dropping off a cliff”.

This “feature” added to the many problems Seafire pilots had to overcome at Salerno, where her larger deck, compared to the four CVE, does not seem to have conferred any advantage while that of the fleet carriers did. From her air group containing 30 Seafire IIc + 8 replacements she suffered 21 deck landing accidents resulting in Seafires with strained or broken undercarriages or wrinkled rear fuselages, that were either not repairable on the ship or not repairable in the timescale available.

The design process that led to the Colossus class saw the ship grow in length. One reason being the prospect, never fulfilled, of a much heavier fleet fighter, the Sea Typhoon, needing a longer free take off run. Useable flight deck length, was a limiting factor for RN carriers in the early war years due to the long round downs. At Taranto Illustrious was limited to a range of 12 torpedo laden Swordfish with overload fuel tanks for example. By 1941/42 the RN was coming to realise the importance of useable deck length.

I don’t know if chopping the upper hangar deck to give her a lower profile would help with the airflow or not. But the shorter flight deck length impacts on the ability to operate the USN style “deck load” strikes that became a feature of RN carrier warfare from 1944 and especially so with heavier aircraft.

Colossus during work up off Malta. The Seafires forward were not part of her official air group. Probably from a Malta based FRU. Barracuda TBR.II on the catapult.

1654070694496.jpeg
The extra 50ft of flight deck length ( 690ft v 640ft) makes more of a difference than an extra 15ft of flight deck width (75ft v 90ft)

In the Pacific in 1945 on Implacable it became common to catapult the first few aircraft, then allow the rest a free take off.
 
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