Re: US Navy Floating Dry Docks
Re: the controversy over ARD 4, my research indicates that ARDs 3 & 4 were never built. ARD 2 is still in Mexican service as ADI-1 as is ARD 5 as Talcahuano and ARD 11 as ADI-2. I believe the ARDs were "Camel" docks.
As an aside, the official designation AFDL is Small Auxiliary Floating Drydock [non self propelled]. They were, before 1946, classified as AFD - Mobile Floating Drydocks. For all of its purported logical basis, USN classification sometimes takes off for left field.