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Title Picture: B-29 Superfortresses undergoing the U.S. Air Force's initially developed cocooning process at Davis-Monthan AFB.
Photo from the Colonel Schrimer Collection.


November 15th, 1945 to August 28th, 1948

On November 15, 1945 the 4105th Army Air Force Base Unit was established at Davis-Monthan Air Force base, Tucson, Arizona, one of the thirty depot units set up by the Reconstruction Finance Corporation. The unit received its first aircraft for storage on January 10, 1946 and it wasn't long before the base was holding seven hundred B-29s and over three hundred C-47s. A small museum collection had also been formed at the site which held some of the more notable aircraft deemed historically important enough to be saved from the mass disposals underway. Included in the collection were also a number of captured German aircraft, some of which would eventually end up at the United States Air Force Museum at Wright-Patterson AFB, OH.

On October 24, 1946 the center was renamed to the 4105th Army Air Force Base Unit (Aircraft Storage), a title which better reflected the units mission of receiving and preparation of aircraft for storage.

During these early years a very basic storage process was established. Following the arrival of an aircraft a limited inspection was carried out which assessed the condition of the airframe and which produced a list of equipment being carried by it. It would then be moved onto one of the designated storage areas and placed on wooden blocks to hold it off the ground to help preserve the condition of the tires. Only a periodic check was made to monitor how the aircraft was fairing in its pretty much unprotected state.

By the end of 1946 the resident museum collection had been expanded considerably. The two atom bomb dropping B-29s, the 'Enola Gay' and 'Bockscar', had arrived as had the famous B-24D Liberator 'Strawberry Bitch' and the Presidential Douglas C-54A Skymaster, 'Sacred Cow'. However, during 1947 and 1948 some of the aircraft were dropped from the collection and were scrapped, including examples of Waco XCG-15A and Douglas XCG-17 assault gliders, the Douglas XC-53A Skytrooper and TB-29 Superfortress. During 1949 the unique Douglas XB-19A 38-471 (see picture to left), the largest US aircraft built before the XB-36 in 1946, was unfortunately also scrapped.

It was recognised that the large number of stored B-29s could still provide an effective bombing and reconnaissance capability, as a result a more effective method of protecting these valuable assets for future operational use were investigated.

Davis-Monthan History_1
Davis-Monthan History_2
Davis-Monthan History_3

A cocooning process, similar to the process which is still in use by AMARG today was developed. After receipt at the base and the cataloguing of carried equipment the aircraft were sealed by the application of an air tight plastic skin called Insulmastic No.4500. The Fort Pitt Packaging Company, which had been incorporated on 10 November 1947, was awarded a contract to preserve a total of 486 B-29s and work towards this was commenced in July 1947. After being thoroughly washed down each aircraft had bags of moitsure absorbing dessicant material loaded into the airframe, and then masking tape was used to seal gaps and cover the propellers and engine cowls.Spray equipment was then used to apply three thick coats of Insulmastic, the first colored yellow, second colored red and the last colored black. The changing colors made it easy to ensure that the coats were applied evenly and to the correct thickness. The plastic was colored by a layer of aluminum paint to help reflect the heat of the Arizona sun.

However, in May 1948, with only 41 B-29s left to process, the project was cut short. Several problems with the cocooning method had been discovered which made the solution impractical to proceed with. Firstly blistering had occurred on a number of aircraft where air trapped underneath the plastic coatings had expanded in the scorchoingly high temperatures experienced in the area. Secondly the Insulmastic layers were becoming very brittle when their temperature exceeded a certain level. This made their removal a very time consuming exercise, requiring some 600 man hours to remove from each aircraft. This problem could, to a certain extent, by reduced by stripping the plastic under shelter where the air temperature could be significantly reduced but this was far from ideal.

The cancellation of the cocooning project did not bode well for the Fort Pitt Packaging Company, by 19 November 1948 the company had ceased trading.

>> 3040th Aircraft Storage Depot