This gets more into the politics than the technical aspects but could an adjustment to carrier tonnage not have been gained if desired?
The escalation in battleship gun calibre was built into Second London, IIUR. And the escalation to Battleship tonnage from 35,000 to 45,000 was negotiated between the remaining powers by March 1938 after both the RN and USN designers ran into the sacrifices that would be required to mount 16” guns on a 35,000 ton hull.
If the RN was serious about an Audacious sized carrier (which is, I suppose, a whole other issue) then could not an increase in allowable carrier tonnage be negotiated with the US?
Which suggestion ignores the difference between capital ships and carriers in the eyes of the world's navies. The capital ship was still the pride of the fleet by which a navy's power was measured.
The USN & RN were fairly sure that the IJN would build battleships larger than laid down in the 1936 Treaty (to which they were not a signatory). The RN thought maybe 46,000 tons with 16in guns. Hence all the efforts to pin them down diplomatically and have a specific provision in relation thereto in Article IV as well as the general protection of Article XXV.
Article IV
"(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.)."
All other categories of ship had to depend solely on Article XXV.
"Article XXV
(1) In the event of any vessel not in conformity with the limitations and restrictions as to standard displacement and armament prescribed by Articles 4, 5 and 7 of the present Treaty being authorised, constructed or acquired by a Power not a party to the present Treaty, each High Contracting Party reserves the right to depart if, and to the extent to which, he considers such departures necessary in order to meet the requirements of his national security;
(a) During the remaining period of the Treaty, from the limitations and restrictions of Articles 3, 4, 5, 6(1) and 7, and
(b) During the current year, from his Annual Programmes of construction and declarations of acquisition.
This right shall be exercised in accordance with the following provisions:
(2) Any High Contracting Party who considers it necessary that such right should be exercised, shall notify the other High Contracting Parties to that effect, stating precisely the nature and extent of the proposed departures and the reasons therefore.
(3) The High Contracting Parties shall thereupon consult together and endeavour to reach an agreement with a view to reducing to a minimum the extent of the departures which may be made."
http://www.ww2ships.com/documents/doc0004-london1936.shtml
That requires knowledge of what the other countries were doing. So the USN & RN were pretty sure that the IJN were building bigger battleships because Japan wouldn't give them the assurances about compliance that they sought, so Article Article IV authorised the increase in gun calibre back to 16in while Article XXV allowed them to negotiate a higher tonnage limit.
The problem was that the USN & RN had no real clue what the IJN were doing with regard to carriers. They knew about the Soryu and Hiryu as they had been laid down before Japan left the Treaty system.down
While it is true that the IJN laid down the two Shokakus of about 27,000 tons standard in Dec 1937 & May 1938, until 1942 when the pair were photographed at Coral Sea, they were believed to be simply an improved Soryu of c17,000 tons. Even the USN ONI book on IJN ship characteristics of late 1942 had to admit that lack of knowledge, but had corrected some of what had previously been assumed based on the photographic evidence (like the increased AA armament).
So without knowledge of a breach on carrier size I can't immediately see how Article XXV can be triggered with respect to carriers.
Then there is the US position. It incorporated the 1922 Treaty carrier tonnage of 135,000 tons into its domestic law. It used that up building CV-2 to CV-7. After the Lexingtons, the largest it built were the 19,800 ton Yorktowns. When it increased the carrier tonnage limit in the 1938 Second Vinson Act, it did so by the specific amount of 40,000 tons, enough for two more Yorktown sized carriers. Half that went to build Hornet and the rest was the starting point for the Essex design starting in summer 1939. As experience with the Yorktowns became available in1939 (Only commissioned in Sept 1937 & May 1938) and with the prospect of a new generation of larger, thirstier aircraft it was only with the Treaty system collapsing in Sept 1939 that the USN moved to a larger ship.
So clearly, in 1938 it was happy with 20,000 tons per carrier. I'm not aware of any attempts at that point to even fully exploit the 23,000 ton limit of the 1936 Treaty.
Moving to the larger Essex of 27,100 tons standard, allowed the air group to be expanded back to the 90 planned for the Yorktowns, but which had been eroded by increasing aircraft size. It also allowed an increase in avgas capacity from 178,000 USG to 232,000 USG, as well as better protection.
Another point to bear in mind about the 1936 Treaty with regard to carriers, is that it removed the overall carrier tonnage limit of 135,000 tons for the USN & RN. So, finances permitting, they could each have built as many 23,000 ton carriers as they wished. That they didn't leads us back to the first paragraph in this post.
