Lexington Class Battle Cruiser - Conversion For Two

Conversion For Two

Construction finally began upon the battlecruisers in 1920 and 1921, after a delay of almost five months. However, that July, U.S. Secretary of State Charles Evans Hughes called for a conference in Washington D.C. to be held that November. The stated goal was to curb the rapidly growing and extremely expensive naval construction programs. It was obvious to the General Board that the expensive new battlecruisers, which some thought were already obsolete, would be very attractive targets for cancellation. Accordingly, studies were done exploring the possibilities of converting one or more of the battlecruisers to different uses: one looked at a conversion to an aircraft carrier, while another contemplated a conversion to an Atlantic ocean liner.

Conversion of a Lexington to an aircraft carrier had both positive and negative aspects when compared with a "specifically designed carrier". While the conversion would have better anti-torpedo protection, larger magazines for aircraft bombs than a keel-up carrier and a more room for aircraft landings (the after elevator would be 28 feet farther up), it would also be a half-knot slower with less hangar space (about 16 percent less), less emergency fuel and "narrower lines" aft (pilots landing on the converted battlecruiser would not have as wide of a runway to aim for). Comparing costs, a brand-new aircraft carrier would cost $27.1 million, while a conversion of one of the Lexington class, not counting the $6.7 million already sunk into them, would cost $22.4 million.

Any debate over converting them was quelled by the signing of the Washington Naval Treaty. Under the terms of the treaty, any capital ships that were under construction by the five signatories (the United States, Great Britain, France, Italy and Japan) had to be canceled and scrapped. For battlecruisers, this encompassed the United States' Lexington class, Japan's Amagi class, and Great Britain's G3 battlecruisers. However, the treaty did allow the participating nations to take two of the capital ships they had under construction and convert them to aircraft carriers; the U.S. Navy decided to complete the two Lexington's that were closest to completion, Lexington and Saratoga.

The problem was that the tonnage cap for new carrier construction had been set at 27,000 tons, which was too low for any practical conversion of the battlecruisers. An exception, spearheaded by Assistant Secretary of the Navy Theodore Roosevelt Jr., was added to the treaty. This gave the five nations the option to convert no more than two capital ships that were under construction to 33,000 ton aircraft carriers. But even that increase of 6,000 tons (from 27,000 to 33,000) was almost not enough for a conversion—it took creative interpreting of a clause in the treaty to allow for the conversion without removing half of the power plant, which the General Board did not want to do. The clause (Chapter II, Part III, Section I, (d)):

No retained capital ships or aircraft carriers shall be reconstructed except for the purpose of providing means of defense against air and submarine attack, and subject to the following rules: The Contracting Powers may, for that purpose, equip existing tonnage with bulge or blister or anti-air attack deck protection, providing the increase of displacement thus effected does not exceed 3,000 tons (3,048 metric tons) displacement for each ship. No alterations in side armor, in calibre, number or general type of mounting of main armament shall be permitted except:

(1) in the case of France and Italy, which countries within the limits allowed for bulge may increase their armor protection and the calibre of the guns now carried on their existing capital ships so as not to exceed 16 inches (406 millimeters) and

(2) the British Empire shall be permitted to complete, in the case of the Renown, the alterations to armor that have already been commenced but temporarily suspended.

Without this clause, the two carriers would have likely been in serious trouble—1928 estimates for the two ships put Lexington at an actual tonnage of 35,689 tons and Saratoga at 35,544, though on official lists the number given was 33,000 tons with a footnote that stated " does not include weight allowance under Ch. 11, pt. 3, Sec. 1, art. (d) of Washington Treaty for providing means against air and submarine attack". This tonnage number was actually carried for their entire careers.