Three Unicorn class carriers.

The maintenance carrier HMS Unicorn was ordered in 1939 and entered service in 1943. It was originally planned that she would be one of three sister ships, so what difference would it have made had all three been ordered at the same time and entered service at about the same time? It should be noted that HMS Unicorn served as a light fleet carrier during the invasion of Italy.
 

SwampTiger

Banned
The only reasonable choice is to alter two of the Colossus class CV's into the somewhat larger Unicorn design. The RN chose to convert two Colossus CVL's, Perseus and Pioneer, to maintenance carriers on the basic Colossus hull. This was the correct choice due to economies of scale. The RN needed lots of ships at the start of the war. Maintenance carriers were low on the list. They were a design for global support to the Armored Deck Carriers. GB needed ADC's for the Atlantic and Mediterranean until 1942. The Maintenance Carrier was best used in the Pacific and Indian Oceans.
 
The maintenance carrier HMS Unicorn was ordered in 1939 and entered service in 1943. It was originally planned that she would be one of three sister ships, so what difference would it have made had all three been ordered at the same time and entered service at about the same time? It should be noted that HMS Unicorn served as a light fleet carrier during the invasion of Italy.

From what I understand there was a great deal of Angst expended on commissioning Unicorn for fear that she would be seen as a proper carrier by the other major powers

Given that the class was a core part of the Armored Box carriers - ie acting as a floating reserve hanger and maintenance facility - and that it was intended that their would eventually be 10 Armored, 1 Ark and 3 Unicorns - the decision to not build the 2nd and 3rd units was foolish IMO and an additional 2 ships would have been very useful

As it was she was a fine carrier and her first job (despite all that Angst) was to act as a fleet carrier to support Seafires to cover the Selerno landings at a time when no other carrier based fighter was available that could match the latest German fighter and twin engine bombers.
 
Does their construction slow anything else, like the Implacables?
With two extra (if small) armoured carriers, with air groups equivalent to illustrious class carriers I could see the Implacables being reordered with full height hangers, so any delay would be worth it.

Now what difference do those two extra ships entering service in 1943 make? Can they be used to establish what becomes the British Pacific Fleet early for example?
 
The biggest problem with extra Unicorns arriving early was that they were slow to build compared to a Colossus class, and carried a similar number of aircraft on a considerably higher displacement.
I'm not convinced of their cost-effectiveness, the idea of a small armoured carrier had been disproved as it wasn't an efficient aircraft carrying ship, a full size fleet carrier carried more aircraft/ton
 
While I agree that for a light carrier the Colossus class is the better design, they weren't designed until 1942 or available before 1945. Here we have an existing pre war design that could have been ordered in 1939 alongside Unicorn and available for service years earlier.
 
From what I understand there was a great deal of Angst expended on commissioning Unicorn for fear that she would be seen as a proper carrier by the other major powers.
Have you any sources for that. She was ordered in the 1938-39 Navy Estimates and laid down in June 1939. Both dates were after the aircraft carrier tonnage quotas of the Washington and First London Treaties had expired. I did read in one of Friedman's books that the British didn't want to start an aircraft carrier building race. However, as they were also planning to build 10 "official" aircraft carriers between 1936 and 1943 I don't see why Unicorn would worry them.
Given that the class was a core part of the Armored Box carriers - ie acting as a floating reserve hanger and maintenance facility - and that it was intended that their would eventually be 10 Armored, 1 Ark and 3 Unicorns - the decision to not build the 2nd and 3rd units was foolish IMO and an additional 2 ships would have been very useful.
The history books and official documents that I've read were that there would be 10 armoured carriers, Ark Royal and the Three Follies by the middle of the 1940s. Is anyone able to quote some sources for a requirement for 3 Unicorn class aircraft carriers before September 1939?

While I agree that 2 additional Unicorns would have been useful in World War II I can also think of several other British warship classes were two more would have been useful too. The problem is that after September 1939 the shipyards were full and priorities were regularly changed, not on a whim, but because it was forced upon the British government by events. So, something else has to go to make room for them.

Another problem is people. Or more accurately a shortage of them. They Royal Navy was paying off older ships from 1943 onwards to find the crews for new ships. If the extra Unicorns were built, something else would have to go. The Unicorn was used as an aircraft carrier to support the Salerno landings IOTL. Her fictional sisters would probably have been used in the same way. So they would probably have taken the place (and the crews) of some of the escort carriers that supported the landings IOTL.
 
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Have you any sources for that. She was ordered in the 1938-39 Navy Estimates and laid down in June 1939. Both dates were after the aircraft carrier tonnage quotas of the Washington and First London Treaties had expired. I did read in one of Friedman's books that the British didn't want to start an aircraft carrier building race. However, as they were also planning to build 10 "official" aircraft carriers between 1936 and 1943 I don't see why Unicorn would worry them.The history books and official documents that I've read were that there would be 10 armoured carriers, Ark Royal and the Three Follies by the middle of the 1940s. Is anyone able to quote some sources for a requirement for 3 Unicorn class aircraft carriers before September 1939?

While I agree that 2 additional Unicorns would have been useful in World War II I can also think of several other British warship classes were two more would have been useful too. The problem is that after September 1939 the shipyards were full and priorities were regularly changed, not on a whim, but because it was forced upon the British government by events. So, something else has to go to make room for them.

Another problem is people. Or more accurately a shortage of them. They Royal Navy was paying off older ships from 1943 onwards to find the crews for new ships. If the extra Unicorns were built, something else would have to go. The Unicorn was used as an aircraft carrier to support the Salerno landings IOTL. Her fictional sisters would probably have been used in the same way. So they would probably have taken the place (and the crews) of some of the escort carriers that supported the landings IOTL.

Source for 3 Decks

Which also agrees with you

"But the RN decided not to press its luck: It ordered only one ship, not the three that were believed necessary to support the number of active fleet carriers. By 1939 the issue was moot anyway: All available ship production resources had already been allocated for emergency war program builds. There was no room for more aircraft auxiliaries."

Perhaps if the decision was made earlier?

Not sure what gives though?
 
Source for 3 Decks

Which also agrees with you

"But the RN decided not to press its luck: It ordered only one ship, not the three that were believed necessary to support the number of active fleet carriers. By 1939 the issue was moot anyway: All available ship production resources had already been allocated for emergency war program builds. There was no room for more aircraft auxiliaries."

Perhaps if the decision was made earlier?

Not sure what gives though?
I'll have to read that properly tomorrow.

I've had a look at my copy of Friedman's British Carrier Aviation. I admit that I only skimmed through the section on HMS Unicorn, but I didn't see him saying that there was a requirement for 3 ships of this type when her staff requirements were written or when she was being designed.

However, there is this passage from Pages 238 and 239 in Chapter 11, Emergency Fleet Carriers, which is about the Colossus and Majestic class light fleet carriers.
There were also other proposals for conversion. By early 1944 it was clear that the British Pacific Fleet would badly need new aircraft maintenance ships equivalent to HMS Unicorn, (see chapter 13 for the reasoning); the two candidates were an American supplied escort carrier and a Colossus. The escort carrier would be an equivalent to one-third of a Unicorn, the light fleet carrier to one-half. The new British Pacific Fleet would need up to three Unicorn equivalents by the end of 1945, that is, nine escort carrier hulls or six light fleet carrier hulls. By this time the first four ships (Colossus, Glory, Vengeance and Venerable) were too far along to convert, but the next four (Edgar, Mars, Warrior and Theseus) were viable candidates. Given an early enough decision, two ships (one unit) could be available at the end of 1944, followed by another in April 1945 and the third in the latter half of 1945. Another alternative, to build a new specialist ship, was rejected because it would have taken too long, even if shipyard capacity could be made available.

In the event, the light fleet carrier conversion was chosen. Ships selected well before completion could be altered internally, and time (up to two months) would actually be saved, because considerable electrical work and piping could be omitted, particularly if endurance was reduced to that required of a conventional fleet auxiliary (5,000nm at 12 knots). HMS Edgar and HMS Mars were chosen, and renamed Perseus and Pioneer respectively.
 
The question becomes what is sacrificed to allow these two ships to be built. One candidate is HMS Belfast, she was mined in November 1939 and declared a total constructive loss but the choice was made to rebuild her. This took two years, if she was scrapped, as she perhaps should have been, or had sunk, at least one of the extra Unicorns could be built using those resources in manpower, space and steel.
 
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