OK question is out of the current stream but is there evidence that warbirds were manufactured or patched with un painted aluminium during WW2?
I'm sure I've seen somewhere that it was a practice in the later stages of the war.
Well, ALL warbirds were manufactured with unpainted aluminum...
All warbirds in "hot zones" (i.e. areas of potential conflict in the 1930s, even if there was no official war) were painted with service branch or even local camouflage schemes. "Squadron Signal Air Force Colors Vol. 1 1926-1942" by Dana Bell is a great resource showing the evolution of Army Air Force paint schemes in the pre-war/early war period. The Navy was experimenting during this period as well, of course.
It was not until 4 months after Pearl Harbor in March 1942 that the Joint Aircraft Committee had issued its standardized color schemes for the Army, Navy and RAF (including RAAF and RCAF) ... all aircraft in theater not conforming to these schemes were stripped and repainted by the end of June, 1942, with all aircraft rolling off the assembly lines painted in these schemes at the factory until January 1944. The one lone exception I am aware of was in the Aleutians, where the enemy air strength was so weak as to not pose more than a nuisance, and operational losses were the primary driver of aircraft attrition, so with air superiority and a greater concern for reducing the weight of aircraft to improve performance (particularly on treacherous takeoff and landing roll-outs in consistently poor flying conditions), many American aircraft in the Aleutians were unpainted. There was also the occasional C-47 General's transport that was unpainted, thought more attractive by the ground crews who maintained them and more "ballsy" by the Generals who flew around in them.
In December 1943, the War Department announced the removal of paint from aircraft to save weight, which primarily affected army aircraft rolling off the assembly lines beginning in 1944. By mid-1944, you see photos of B-17 squadrons where half of the planes are painted and half are in "naked" aluminum finish, and the prevalence of unpainted aluminum aircraft becomes very noticeable ... especially P-51s, P-38s and B-29s. Of course the Navy painted all of their aircraft through the end of the war, and even with the War Department announcement, many local army units preferred to continue with painted aircraft to the end of the war.
