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[Bill Mangus]

"Good pix, gang - and agree, there is a 'bar' clearly enough (I like that term better than stringer, which it does not seem to be).  Purpose?  Something to do with Fred's celestial shots, maybe?  A way to open the upper portion perhaps, or to install a more optically correct panel in one-half (glass)?  Dunno."

Interior mount for sextant/octant?

[Bill Mangus]

"Second photo below
Taken in early September 1936 at Floyd Bennet Field in NY before the start of the Bendix Race.  No lavatory window. Stringer through the cabin window."

I don't think it is totally the hypothetical mid-window stringer.  Look how the streak in the window lines up perfectly with the line of brightest reflections on either side of the window.  It "could" be all reflection, especially if there is no interior piece to break-up the reflection and it is characteristic of a reflection off a curved surface.

[Greg Daspit]

It was apparently okay to have a gap in the Station 307 circumferential stiffener when the window was installed so there would be no need to replace and rivet the missing section of the stiffener.

I suspect if the circumferential stiffener cut ends were attached to horizontal stringers around the new window, then some loads collected by the circumferential stiffener could be transferred to the stringer. If the fuselage was stressed by severe bending, the cut 307 stiffener ends could pull or push on the horizontal stringer near the mid span of the opening and possibly make something like the first tear in 2-2-V-1.

[Ric Gillespie]

Purpose?  Something to do with Fred's celestial shots, maybe?  A way to open the upper portion perhaps, or to install a more optically correct panel in one-half (glass)?  Dunno.

Remember, the bar is there almost a year before Noonan comes on the scene and before Earhart was considering taking any navigator.  The plan, as late as November 1936 was AE to make the world flight solo.  The bar goes away in early 1937 when they start making mods for the first attempt.

[Ric Gillespie]

I don't think it is totally the hypothetical mid-window stringer.  Look how the streak in the window lines up perfectly with the line of brightest reflections on either side of the window.  It "could" be all reflection, especially if there is no interior piece to break-up the reflection and it is characteristic of a reflection off a curved surface.

The bar shows up in lots of photos taken in 1936.

[JNev]

It is possible that it is a structural member that was later deemed unnecessary (hence, gone later).  If so, it would not have likely been a 'stringer' per se, but some sort of compression-resistant (and tension bearing) 'strut' type device.  As such it could have well translated loads through any mid-window / mid-bay stringer arrangement that was otherwise interrupted by the windows.

But where does this go, how does it fit the lav window / patch scheme?  I guess it may be interesting as to why the window was skinned over and whether that had to do with some perception of fuselage weakness during heavy loading / rough field work that might have been encountered.  Interesting, but I'm not sure how relevant to identifying whether 2-2-V-1 is of NR16020?  Just a thought.

[Tim Collins]

What does Lockheed say about this "bar" across the window? If it is seen on the plane right up until modifications began being made for AE's extended flight purposes then, it may have been factory original to the plane? Of the fotos I've seen I get the impression that it wasn't structural to the plane but part of the window - ie, the window wasn't one piece of plexi.

[JNev]

Don't know what Lockheed can tell us today, or what prints of the window detail are around - but by the picture from Purdue that Greg Daspit linked to it appears that this is part of the removable window assembly / inner frame, IMO.  Take a close gander - and note what appears to be a single fastener visible at forward end of the 'bar' -

[Ric Gillespie]

Interesting, but I'm not sure how relevant to identifying whether 2-2-V-1 is of NR16020?  Just a thought.

I see no relevance at all. The bar through the window is a curiosity and a bit of a mystery. Nothing more.

The be all and end all in the question of whether 2-2-V-1 is the patch is whether the rivet pattern matches. For an answer we must turn to Jeff Glickman.  There will be one of three possible outcomes.
1. Jeff will not be able to discern the rivet pattern.  In that case we'll undoubtedly continue to explore the possibility that our artifact is the patch but it's hard to see how we'd ever get to a smoking gun level of certainty unless the engineering drawing for the patch (there had to be one) somehow comes to light.
2. Jeff will be able to confirm that the rivet pattern is different from what we see on 2-2-V-1.  In that case the hypothesis fails and we're back to square one with 2-2-V-1.
3. Jeff will be able to confirm that the rivet pattern on the patch matches 2-2-V-1.  In that case, just as with the Bevington Object, we would get a second, independent opinion  Maybe even a third.  The importance of such a match cannot be overstated and replicability of results is the essence of science.  If the match is confirmed we'll need to put together an airtight, peer reviewed research paper making the case that we have a conclusively identified piece of NR16020.

Meanwhile, there's no harm in continuing to think about how the structure of the patch may or may not match 2-2-V-1.  For example, the artifact is .032" sheet.  The sheet bordering the patch on three sides (top,rear, and bottom) is .025". The forward edge abuts a .032" skin.  Does it make sense for the patch to be .032"?

[Ric Gillespie]

Don't know what Lockheed can tell us today,

Today Lockheed Martin would say, "What's a Model 10?"

[JNev]

Interesting, but I'm not sure how relevant to identifying whether 2-2-V-1 is of NR16020?  Just a thought.

I see no relevance at all. The bar through the window is a curiosity and a bit of a mystery. Nothing more.

The be all and end all in the question of whether 2-2-V-1 is the patch is whether the rivet pattern matches. For an answer we must turn to Jeff Glickman.  There will be one of three possible outcomes.
1. Jeff will not be able to discern the rivet pattern.  In that case we'll undoubtedly continue to explore the possibility that our artifact is the patch but it's hard to see how we'd ever get to a smoking gun level of certainty unless the engineering drawing for the patch (there had to be one) somehow comes to light.
2. Jeff will be able to confirm that the rivet pattern is different from what we see on 2-2-V-1.  In that case the hypothesis fails and we're back to square one with 2-2-V-1.
3. Jeff will be able to confirm that the rivet pattern on the patch matches 2-2-V-1.  In that case, just as with the Bevington Object, we would get a second, independent opinion  Maybe even a third.  The importance of such a match cannot be overstated and replicability of results is the essence of science.  If the match is confirmed we'll need to put together an airtight, peer reviewed research paper making the case that we have a conclusively identified piece of NR16020.

Meanwhile, there's no harm in continuing to think about how the structure of the patch may or may not match 2-2-V-1.  For example, the artifact is .032" sheet.  The sheet bordering the patch on three sides (top,rear, and bottom) is .025". The forward edge abuts a .032" skin.  Does it make sense for the patch to be .032"?

Good points, good plan.

By all I know of aircraft sheetmetal work of this type, yes, it makes good sense that the patch would be .032".  It is often desireable to go up a gage in thickness, and in this case there may well have been a desire to restore some strength and rigidity to the area lost by the window aperture (conjecture - I don't know that, but it appears to be a reasonable idea).  An .032" skin would also still fair reasonably behind the lap just forward of the patch leading edge - except considering that the patch was likely simply applied over the mod-window coaming. 

What can be discerned of rivet pattern is of course crucial.  What is nice is that we have ample pictures of this area on the non-modified NR16020, so there could be some chance of showing a match at an original line on the base airframe compared to a margin (edge) arrangement on 2-2-V-1.  The mid-field stuff is the real crapshoot - no clear pix so far, but good to see what Glickman can do, I think. 

How 2-2-V-1 was braced (the mid-field lines of rivets that once attached to some underlying stucture, likely stiffeners in my thinking) is the grab bag - that's a very telling pattern, if only we can discern how it was actually done on NR16020.  The margins could, however, be enough.

Interesting that the upper edge of the mod-window cut right through a double-staggered row of rivets which likely had a substantial stiffener mounted behind it - and makes me wonder how that was compensated for, stress-wise.  Makes me wonder further about what was done when the patch was installed - was that stringer-line somehow re-established, even in rudementary form?  COULD account for some of the mid-field patterning we see on 2-2-V-1 at what may be the first row 'down' from the 'top' (a guess).  Just an example of traceable rivet patterns that might be tied to the mother ship yet.

Fascinating - very glad Miami Herald could provide some help.

[Tim Collins]

Don't know what Lockheed can tell us today, or what prints of the window detail are around - but by the picture from Purdue that Greg Daspit linked to it appears that this is part of the removable window assembly / inner frame, IMO.  Take a close gander - and note what appears to be a single fastener visible at forward end of the 'bar' -

I'm not entirely sure whether this exercise (about the "bar" and window) is in fact irrelevant or not.  If indeed the bar can be attributed to a structural function then clearly additional strengthening was deemed necessary at that point in the body of the craft. It also stands to reason that if it were to be replaced/filled in, that additional bracing to the replacement structure would also be needed as it wasn't an integral part of the whole surrounding structure, hence the additional rows of rivets indicating additional underlying bracing. Unfortunately, the fact that the bar disappears from later fotos suggests it might not have been structural.  I'm beginning to suspect that the "bar" may have functioned more to protect the plexi than to strengthen the structure. Just a guess though.

So much for that theory. But is it? Look at the skin to the fore and aft of the smaller window farther forward, where there are multiple longitudinal rows of rivets on either side of the window. Stands to reason that skinning over a hole where a larger window had been would would have been reenforced similarly.  Now we just need to see the rivet lines  to confirm.  Does 2-2-V-1 fit the pattern suggested by rivet lines on either side of the smaller window? 

Sorry if I stated the obvious.

[JNev]

I think the bar may have had a more basic intent - perhaps to protect the window with peeps moving around in the bird during flight or something.  It does not appear to be a structural member by what I am observing here.

It is true that a stiffener runs fore and aft at about mid-waterline to the windows - but it is not a stringer (not a major component) and is no doubt readily accounted for where interrupted by the structure of the window frames themselves.  That is fairly common in semi-monocoque construction like this.

That big window being punched out of the forward tail cone section in the lav area may have been another matter - it is big, and was partly cut right through a double row of rivets, implying some degree of structural interruption.  One would think the window frame there was also designed to compensate for that, and likely was - but we can't see how so far.

[Ric Gillespie]

That big window being punched out of the forward tail cone section in the lav area may have been another matter - it is big, and wasp cut right through a double row of rivets, implying some degree of structural interruption. 

You have to wonder why they did that.  Was it so important that the window be that big?  Important to whom?  Certainly not FN.  He wasn't on the scene until at least a month later.  Had to be Harry Manning, the navigator who turned to not know how to do celestial nav from an airplane.  The whole thing seems typical of the half-assness that plagued the entire Earhart/Putnam operation.

[Jay Burkett]

That looks like a temporary plug for that opening that was used only during production.  If could be that a lot of manpower was used to move the fuselage along the assembly line.  They may have preferred the door frame to be the hand-hold of choice and not the window frame which would be much more fragile.  The plug would have been removed just before the window was installed.  We have already seen evidence that electric drills were being used.  It would have been tempting for the guys on the assembly line to pass the extension cord through the window opening instead of through the door.  However, the window opening at that stage may not have been extension cord friendly.  The solution would be to install a temporary plug.  You see this kind of thing all the time today.  Temporary caps, plates, plugs and covers can be seen everywhere on today’s assembly lines.  It would not be a stretch of the imagination that they were in use when the Electra was being built.

Stringers adjacent to the windows …

Note that the window belt will have more longitudinal stringers, or intercostals, around the original window openings.  If a fuselage was to be built without windows in a particular area the additional intercostals would be left out to simplify construction and save weight.  If an opening was added at a later date this additional structure would have to be added. 

I can't recall if Tighar has access to an SRM for the Model 10.  If you do it might have a typical stringer diagram that might prove useful.  It might also have a skin, or plating, diagram.  The gold standard would be the actual production drawings, but, those may be hard to find.

Back to the patch …

What keeps bugging me is there is “no window”, then a “big window” which gets replaced by a “big patch”.  In all probability the patch was a field repair that was performed by a local mechanic using the standard practices that were in use at the time.  I’m a somewhat convinced that the window installation itself may not have been done by Lockheed.  This window-become-patched-opening looks to be larger than a typical window.  At least one more stringer would have to be cut and would require more structure to restore the load path around the opening.  If we were doing that today you would probably see an external doubler applied.  I don't see any evidence of an internal doubler or structure.  This may be due to the low resolution of the photos we have available.  An internal doubler could have been installed, but, this would have been a far more extensive installation since mold line of the skin would be stepped inboard by the thickness of the doubler.  You would have to remove and replace at least the frames on either side of the window opening and a bunch of the fasteners in the stringers.  I just cannot imagine them doing all of that.  At the same time there is no evidence of an external doubler.  A convincing argument could be made that the fuselage at the location of that window could have been weak enough so the flex experienced in a hard landing could have cracked the window.   It might have happened more than once --- hence the patch.  That piece of acrylic would have to be specially formed to match the fuselage contour at that location.  A patch just attached with fasteners around the periphery would have to be stiffened to keep it from oil canning.  The mechanic may have just looked at the rivet patterns around the other windows and used that as a rough guide.  One stiffener would probably have been fine.  He may have had to use three stiffeners, along with some “hand forming”, or bending, in order to get the “patch” to lay as flush as possible to the skin around the opening.  The result would have been somewhat rough.

I can’t figure out why they needed such a large window at that location.  The better question woud be:  If they thought that he large window was necessary, and obviously they did at some point, why would they have attempted the round-the-world flight without it?