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Author Topic: Artifact 2-3-V-2  (Read 3284 times)

Matt Revington

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Artifact 2-3-V-2
« on: January 02, 2020, 12:26:21 PM »

This just something I have been thinking about lately, it is speculative , feel free to criticize it.

As noted in (https://tighar.org/Publications/TTracks/12_2/obj11.html) the plexiglass pieces found on Niku in the 1990s (2-3-V-2) were consistent with Lockheed's specifications for the Electra windows however, similarly  to 2-2-V-1 , it is difficult to absolutely rule out that it potentially came from later sources, particularly WWII aircraft where the canopies were commonly made of plexiglass.  The 1996 research bulletin (https://tighar.org/Publications/TTracks/1996Vol_12/40552.pdf) indicates that plexiglass was a relatively expensive and rare material (apparently only used for aircraft windows and jukeboxes) prior to WWII and production was only scaled up due to the war effort.  Testing done by a lab hired by TIGHAR  indicated that it composed of polymethyl methacrylate as plexiglass is but I see no further  details of the testing.   While the basic structure of plexiglass from before and during  the war would have been the same  I wonder if the industrial processes changed such that small contaminants from manufacture would be different and therefore prewar plexiglass could be differentiated from wartime or later plexiglass.  I have tried to sort through the chemistry literature on this but I have found nothing , but that is not totally surprising since as part of the war effort it is unlikely that improved manufacturing processes would have been widely published.  Testing (chemical or elemental analysis) of known prewar samples vs wartime samples (if available ) might be able to date these pieces as prewar. given the rarity of prewar plexiglass it would be hard to conceive of another source on Niku than the Electra.  It would still be short of the "smoking gun" level but given the difficulty in firmly dating 2-2-V-1 this might be another path to dating an existing artifact to the prewar period.

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Ric Gillespie

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Re: Artifact 2-3-V-2
« Reply #1 on: January 02, 2020, 04:06:01 PM »

Testing (chemical or elemental analysis) of known prewar samples vs wartime samples (if available ) might be able to date these pieces as prewar.

Interesting thought.  The trick would be getting our hands on documented specimens of pre-war and WWII Plexiglas for destructive testing.  (Excuse me sir.  Would you mind if we cut a small piece out of your B-17 top turret?)
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Matt Revington

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Re: Artifact 2-3-V-2
« Reply #2 on: January 03, 2020, 10:29:54 AM »

You probably wouldn't need to cut pieces of plexiglass out, the paper that I link to below looks at aviation plastics (in goggles and canopies) from pre WWII until more recent times using a portable (raman) spectrometer that could be brought to the sites and test non-destructively.

https://repository.si.edu/bitstream/handle/10088/25565/mci38408.pdf?sequence=1&isAllowed=y

The downside of this is that I am not sure this technique would identify subtle manufacturing differences, at least with the way it is used here it just identifies characteristic spectral fingerprints of the type of plastics used but it may be possible to get more specific
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Bill Mangus

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Re: Artifact 2-3-V-2
« Reply #3 on: January 03, 2020, 11:19:40 AM »

One source might be NMUSAF in Dayton, OH.  When the group of us visited the Museum's Restoration Facility with 2-2-V-1 we were given a walkthrough of the work then being done on Memphis BellI have an admittedly vague memory of us being show work done on the top turret in a separate room and our guide mentioning how they needed to replace some/most of the plexiglass panels in the turret and found someone who had a partial turret in his barn, I think.  Upshot is, there may still be some out there is one is committed to finding it.  The Museum may have some leftover scraps also.

I'm wondering how Lockheed would have sourced the plexiglass for the cabin/door windows.  Who was making it then and how close to the Lockheed factory were they/  Are they still around in some form?
« Last Edit: January 03, 2020, 11:36:15 AM by Bill Mangus »
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Ric Gillespie

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Re: Artifact 2-3-V-2
« Reply #4 on: January 03, 2020, 11:28:48 AM »

Who was making it then and how close to the Lockheed factory were they/  Are they still around in some form?

Rohm & Haas held the patent on PMMA (tradename Plexiglas) in the U.S. 
They're in Philadephia, but they weren't much help when I contacted them back when we were first researching the artifact.
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Ric Gillespie

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Re: Artifact 2-3-V-2
« Reply #5 on: January 03, 2020, 12:16:22 PM »

The downside of this is that I am not sure this technique would identify subtle manufacturing differences, at least with the way it is used here it just identifies characteristic spectral fingerprints of the type of plastics used but it may be possible to get more specific

I guess the thing to do would be to contact the people who did the survey and describe what we're hoping to learn.
A perennial problem in doing this kind of analysis is making sure the sample is original to the aircraft and not part of a restoration.
« Last Edit: January 03, 2020, 06:09:53 PM by Bruce Thomas »
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Bill Mangus

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Re: Artifact 2-3-V-2
« Reply #6 on: January 03, 2020, 12:55:47 PM »

Wonder if any scraps of plexiglass would still be at the site of the Electra crash in, I think it is, Idaho?
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Ric Gillespie

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Re: Artifact 2-3-V-2
« Reply #7 on: January 03, 2020, 02:13:17 PM »

Wonder if any scraps of plexiglass would still be at the site of the Electra crash in, I think it is, Idaho?

We didn't see any.  Most of that wreckage was salvaged out during WWII. That airplane flew full-tilt into the mountain so there is probably shattered Plexi there if you look hard enough.  Gotta be an easier way.
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Walt Holm

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Re: Artifact 2-3-V-2
« Reply #8 on: January 03, 2020, 04:35:36 PM »

There's also the Electra wreck in the Misty Fjords area SE of Ketchikan, though revisiting this site would hardly qualify as "an easier way".  It could, however, be an excellent source of Plexiglas from the original Electra production line.

I pulled out my photos of the visit from 2004, and there wasn't any plexi apparent.  But my photos were mostly promo shots of people. 

John Clauss did the photo documentation on that trip.  I've called him and he's going to look through his stash of photos to see if there's anything there.

A revisit of this site might be something to keep in mind if indeed there's a test that can distinguish between different plexi formulations.
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Ric Gillespie

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Re: Artifact 2-3-V-2
« Reply #9 on: January 03, 2020, 04:58:02 PM »

I pulled out my photos of the visit from 2004, and there wasn't any plexi apparent. 

I looked at the photos I have and the only one that should show a window doesn't.  I can only think the wrinkling of the fuselage during the crash caused the window to pop out or shatter (Plexiglas doesn't wrinkle).
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Bill Mangus

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Re: Artifact 2-3-V-2
« Reply #10 on: January 03, 2020, 07:25:36 PM »

Actually, I think there may be plexiglass present in that picture.  Look at the bottom of the window frame just above the horizontal stringer.  Is that a portion of  plexiglass sort of sandwiched between the stringer and frame?
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Ric Gillespie

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Re: Artifact 2-3-V-2
« Reply #11 on: January 04, 2020, 09:40:24 AM »

Is that a portion of  plexiglass sort of sandwiched between the stringer and frame?

I think that's skin.  One interesting thing about the Electra wreckage in Alaska and Idaho is the blue coating on the aluminum, a corrosion inhibitor that preceded the greenish/yellow zinc chromate that came into use in 1939.  Unfortunately, there is no trace of any kind of coating or paint on 2-2-V-1.
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Bill Mangus

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Re: Artifact 2-3-V-2
« Reply #12 on: January 04, 2020, 09:54:29 AM »

Seems a little thick for skin.  What I'm looking at is at the corner formed by the vertical window frame/skin and the top of the largely intact left section of the horizontal stringer running across the bottom of the window.  There isn't much of it and it barely comes out higher than the corner junction and it covers only about the middle part of the vertical piece of skin.  On the right side where the stringer is badly deformed, there's nothing showing above the corner junction.

See the right end of that moss covered rock/wood where the green leaves start.  It's straight down from there.
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Matt Revington

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Re: Artifact 2-3-V-2
« Reply #13 on: January 04, 2020, 10:01:40 AM »

Do you mean the material in the yellow circle?
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Ric Gillespie

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Re: Artifact 2-3-V-2
« Reply #14 on: January 04, 2020, 10:05:43 AM »

See the right end of that moss covered rock/wood where the green leaves start.  It's straight down from there.

Me too.
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