Discovery
On the afternoon of the fourth day of the NIKU III
Preliminary Expedition, team member Veryl Fenlason (#0053CE) noticed
an object lying on the jungle floor in the “old village” and
thought it might be a piece of Plexiglas.
Veryl brought the artifact to the attention of the
expedition leader and other team members in the area and it was discussed
as a candidate for collection. It was clear that this was part of
a larger object made of fairly sophisticated 20th century material
from which pieces had been crudely cut and broken. Its surface exhibited
a slight but uniform curvature. No source of such material had been
encountered elswhere in the village and the location was too far
inland for it to have washed in from the sea. Other debris in the
same location exhibited similar evidence of having been cut apart,
suggesting that whoever lived here was something of a craftsman or
tinkerer. A further search of the spot turned up another smaller
shard of the same material which fit a break in the first piece.
Because known aircraft parts had been found in the vicinity it seemed
reasonable to speculate that this might indeed be plexiglas and to
have come from an aircraft. The expedition leader made the decision
to collect the two pieces for testing and cleared their recovery
with the Kiribati government representative as Artifact 2-3-V-2.
Initial Testing
Upon our return to the United States the first step
was to conclusively identify the material. This was accomplished
by contracting with a reputable conservation laboratory for a compositional
analysis. A series of tests confirmed that the material is polymethyl
methacrylate (PMMA), also known by the trade name Plexiglas. So
far so good, but that didn’t make it an airplane component, much less
part of the Electra. We next contacted Rohm & Haas, the company
which first produced Plexiglas in the U.S., and got some history
on the product. Polymethyl methacrylate was first produced in Germany
by the Rohm company in 1927. In 1936, Rohm & Haas began producing
it in the U.S. under the trade name “Plexiglas.” DuPont
also made PMMA and called it “Lucite,” while in Britain,
ICI Ltd offered the same product under the name “Perspex.” The
new material was far superior to earlier cellulose-based products
(Pyralin and Plasticele) used in airplanes where a curved transparent
surface was needed, and by 1937 aviation maintenance manuals included
instruction on how to work with plexiglas. Because it was relatively
expensive, pre-war use of PMMA was limited to aviation applications
and the manufacture of jukeboxes. During and immediately after the
war it was almost exclusively an aviation product and didn’t come
into common civilian use until the early ’50s. Because the ”old
village” on Nikumaroro was abandoned in 1949 and (as far as
we know) had no jukebox, we concluded that the artifact had probably
come from an airplane. But what airplane?
Matching
the Windows
All of the airplane parts found on Nikumaroro so far seem to fall
into two categories, B-24 and Lockheed Electra. Since both aircraft
could have had Plexiglas windows the next step was to look at the
artifact’s curvature and thickness. Plexiglas, to be formed, must
be heated to at least 90¡C-a far higher temperature than could be
reached just lying on the ground (even on Nikumaroro), so the curvature
of the artifact is almost certainly original. To see if it is the
same curvature as a Lockheed Electra cabin window we asked our friends
at the New England Air Museum in Windsor Locks, Connecticut to send
us one from their under-restoration Electra c/n 1052 (Earhart’s was
c/n 1055). The exterior surface curve of the artifact and the window
appeared to be identical. The glass from 1052, however, was tinted
and twice as thick as the artifact (1/4 inch versus 1/8 inch). Early
photos of 1052 show that it was not delivered with tinted windows
so this must be a later replacement. The real question, of course,
was how thick were the windows in Earhart’s airplane?
Back
to the Drawing Board
A search of microfilmed engineering drawings for the Lockheed Model
10 at the National Air & Space Museum’s Garber Facility
in Suitland, Maryland, proved revealing. The drawing for “Part
Number 40552 – Window Glass, Fuselage, Cabin” shows that
a number of changes were made to the material and thickness specifications
over the production life of the design (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 significant 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.
But what about the B-24? A search of engineering drawings for the
Consolidated Model 32 show that the fuselage windows of the Liberator
(Part No. 32B1198) were 1/10 inch thick and had no curvature at all.
The Plexiglas used in the nose and turrets was, of course, much thicker.
Our conclusion is that Artifact 2-3-V-2 is consistent in all known
respects to Lockheed Part Number 40552 and is not consistent with
the only other known source of airplane parts found on Nikumaroro,
the Consolidated B-24.
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