Volume 12 Number 2/3
October, 1996
earhartlogoearhartlogoFound Objects
Navigator’s Bookcase Sheet of aluminum with red paint Cut Strip of Aluminum Aluminum Plate
Dado Aircraft Skin Aluminum Comb Riveted Assembly
Channel Section Cables Plexiglas Aircraft Safety Wire
Thermometer, broken Threaded metal cap Shoe parts Artifact 2-2-G-8, Shoe heel
[L10] Plexiglas (TIGHAR Artifact 2-3-V-2)
Date Found: February 1996 during TIGHAR’s NIKU III Preliminary expedition. plexi
Materials analysis: Winterthur Museum Analytical Laboratory
Report date: February 22, 1996
Description: This is an irregularly shaped sheet of transparent polymethyl methacrylate (PMMA), trade name Plexiglas. It measures nominally 4.75 inches long by 2.5 inches wide and is 1/8 inch thick. A second fragment is roughly 1.75 inches long by 1.5 inches wide and fits a fractured edge of the larger piece. Both pieces exhibit a slight but uniform curvature over the surface.
Condition: The convex surface of the sheet exhibits a number of shallow scratches, while the concave surface has only a few. One edge appears to be an original manufactured edge. The others exhibit saw marks. There is no evidence of heat damage. Because PMMA must be heated to at least 90°C to be formed, the curve of the surface on this sheet is probably original.
Identification: This appears to be a scrap from Lockheed Model 10 Part Number 40552 – Window Glass, Fuselage, Cabin.
Commentary: Lockheed engineering drawings show that the material, the curvature, and the thickness of the artifact match those specified for the cabin windows of the Electra. A number of changes were made to the material and thickness specifications for the windows over the production-life of the Model 10 (1934 to 1941). Of particular interest is a change specified for January 15, 1937 at which time the window thickness was reduced from 5/32 to 1/8 inch. The date is of special interest because it was just at that time that the cabin windows in Earhart’s airplane were replaced and additional special windows were installed as part of her world flight preparations. The curvature and thickness of the Plexiglas found on Nikumaroro exactly matches Lockheed’s specifications for Electra cabin windows at exactly the time Earhart’s new windows were installed. They do not match any window on the B-24.
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