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Royal Navy new-build Carriers 1920-24

JFC Fuller

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The opening British position at Washington was for a 25,000 ton individual ship limit and a 125,000 ton total tonnage limit for aircraft carriers that would allow the RN to possess five 25,000 ton carriers. The ultimate agreement was very close to this. The figure of five for the RN came from July 1920 Admiralty conference report that called for three in the Home Fleet and two for overseas commitments and refitting though I have also seen it expressed as two for each of two main fleets and one refitting. To my knowledge no specific RN 25,000 ton design study from 1920/21 has ever been found but DNC was well aware that new build ships would be much more efficient at carrying aircraft than the conversions, it was estimated that building new from the keel up would have produced weight savings as follows:

Furious: 22,000tons, new build 18,000 tons for a saving of 4,000 tons (30 knots)
Eagle: 23,000tons, new build 15,000tons for a saving of 8,000 tons (24 knots)

The conversions were less efficient than new construction in terms of aircraft carriage, an even more significant issue in light of the tonnage caps enshrined in the Washington Treaty, but they had the advantage of being about half the cost (£3m versus £6m) of new construction so proceeded.

Whilst no 1920/21 25,000 ton new build RN design has been found there are three design proposals for new build ships from 1923:

Scheme A: 10,000 tons, loosely based on Hermes with a flush deck, 5x 5.5" + 3x4" AA guns and 24 (or 27?) knot speed (27 aircraft)
Scheme B: 16,500 tons, double hangar with near Furious aircraft capacity, 6 x 4.7" AA guns and 34.5 knot speed (35 aircraft)
Scheme C: 25,000 tons, 6x8" guns (50 aircraft)

I find Scheme C most interesting as it maps to the pre-treaty thinking. However, Scheme B was chosen for development and grew in weight to 17,200 tons before being abandoned, hangar height was 15ft. This design was preferred as the Washington Treaty meant allowable tonnage was at a premium and it had been in intended for the 1925/26 programme but was progressively deferred - first to 1929 and then to 1932. John Jordan has a sketch (attached) of this design in his book Warships after Washington and gives the following additional specs:

Dimensions: 765ft x 80ft
Machinery: four shaft geared turbines, 120,000 SHP
Armour: Belt 2" deck 1"
 

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PMN1

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Any drawings of Scheme C?
 

zen

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Wasn't Scheme C ?
LBP 780ft, LOA 820ft
Beam 92ft
Draught fed 23.5ft, aft 25.5ft
Displacement 25,000tons
Deep 29,500tons
SHP 180,000shp
Speed 34.5kts
Deep 33kts
Fuel 4,000tons
Endurance 6,000nm
Complement 1200

47" by 6
4" by 6
Aircraft 36 spotters, 50 fighters, recce 42, amphibious 42

On the face of it a much better proposition.
 

TomS

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Aircraft 36 spotters, 50 fighters, recce 42, amphibious 42

On the face of it a much better proposition.
The aircraft complement is a list of alternatives, right? No way a ship of this size could carry 170 aircraft.
 

Tzoli

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you mean 6x1 4" and 6x1 4,7" Guns?
 
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zen

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So found the reason for why this 25,000ton sketch isn't attractive. It's not 6 by 4" guns, they are 8" guns!

No wonder this impacts internal space and aircraft numbers.
 

PMN1

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The opening British position at Washington was for a 25,000 ton individual ship limit and a 125,000 ton total tonnage limit for aircraft carriers that would allow the RN to possess five 25,000 ton carriers. The ultimate agreement was very close to this. The figure of five for the RN came from July 1920 Admiralty conference report that called for three in the Home Fleet and two for overseas commitments and refitting though I have also seen it expressed as two for each of two main fleets and one refitting. To my knowledge no specific RN 25,000 ton design study from 1920/21 has ever been found but DNC was well aware that new build ships would be much more efficient at carrying aircraft than the conversions, it was estimated that building new from the keel up would have produced weight savings as follows:

Furious: 22,000tons, new build 18,000 tons for a saving of 4,000 tons (30 knots)
Eagle: 23,000tons, new build 15,000tons for a saving of 8,000 tons (24 knots)

The conversions were less efficient than new construction in terms of aircraft carriage, an even more significant issue in light of the tonnage caps enshrined in the Washington Treaty, but they had the advantage of being about half the cost (£3m versus £6m) of new construction so proceeded.

Whilst no 1920/21 25,000 ton new build RN design has been found there are three design proposals for new build ships from 1923:

Scheme A: 10,000 tons, loosely based on Hermes with a flush deck, 5x 5.5" + 3x4" AA guns and 24 (or 27?) knot speed (27 aircraft)
Scheme B: 16,500 tons, double hangar with near Furious aircraft capacity, 6 x 4.7" AA guns and 34.5 knot speed (35 aircraft)
Scheme C: 25,000 tons, 6x8" guns (50 aircraft)

I find Scheme C most interesting as it maps to the pre-treaty thinking. However, Scheme B was chosen for development and grew in weight to 17,200 tons before being abandoned, hangar height was 15ft. This design was preferred as the Washington Treaty meant allowable tonnage was at a premium and it had been in intended for the 1925/26 programme but was progressively deferred - first to 1929 and then to 1932. John Jordan has a sketch (attached) of this design in his book Warships after Washington and gives the following additional specs:

Dimensions: 765ft x 80ft
Machinery: four shaft geared turbines, 120,000 SHP
Armour: Belt 2" deck 1"
Any indication where the 8" guns were mounted....all down the sides or some in bows or stern?
 

zen

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Logic suggests along the sides, where they would impact hanger space as Friedman stated.
 

Tzoli

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Yes on 25.000tons that is a large ship and twin turrets seems accurate for RN thinking. RN 8" casemates seems weird in the 1920's, except if they wished to mirror the Japanese Akagi and Kaga
 

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JFC Fuller

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The only clues I have seen to Scheme C's layout are that the the 8 inch guns were in three twin turrets and that they ate into hangar space. I would speculate that it would have looked like an enlarged version of Scheme B with two twin turrets forward of the funnels, the aft super firing over the forward, and one aft of the funnels. That way the forward magazines could have been forward of the boiler rooms. The location of the aft 8 inch magazine is an interesting question though?

The 8 inch battery would have needed fire control arrangements so it seems logical that the square faced tower and director used on the early counties would have been somewhere between the fore and aft turrets, perhaps between the forward funnel and forward turrets?
 
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PMN1

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What was the planned order of replacement for the existing carriers?
 
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