Ric,
Again, thanks for your thoughtful reply on this. I appreciate the continuing emphasis on Glickman's work toward interpretation of the photo data. I think there is value, however, in a more direct review of the Wichita exercise, given -
...I agree that the forward edge of certainly the window coaming and apparently the subsequent patch were set back from Station 293 5/8. Based on the known 1.5 inch rivet pitch on the skin forward of the window/patch, the window coaming looks to have been riveted about an inch and a half aft of the edge of the skin.
I agree and was able to validate it by scaling landmarks on the very clear Wichita picture against similar landmarks on the Earhart Electra in the Nilla-Amelia picture, namely the rivet row at STA 320, and distance to the aft edge of the skin near STA 293 5/8. I used the direct measurements available in the form of your measuring tape on the Wichita image as a starting point by which to establish some actual datum references - rivet line and skin edge displacements, namely.
By direct measurement thus it is 12" from the rivet line at STA 307 to the aft edge of the skin near STA 293 5/8 - see picture. The forward coaming vertical rivet line lies approximately 1.5" aft of the aft edge of the skin ending near STA 293 5/8. The forward coaming rivet line - and assuming the patch is similar - as it does appear to be, lies therefore 10.5" forward of the rivet line at STA 307.
See attached mark-up of your Wichita photo and reference the scale you and Glickman applied thereon, please.
...we can place the forward edge of the patch at 295 1/8.
This citation of a station may be an indicator of an assumption that has introduced error - there can be a hazard in using assumptions about rivet lines lying faithfully along stations. Deriving distances this way may have swayed your calculations.
Visible rivet lines and skin edges can be and often are actually offset from 'stations', which are in fact more theoretical at times than easily pinpointed physical landmarks. A station more often is one face or the other of a bulkhead, etc. as laid-up in the jig, but seldom directly in alignment with a rivet line. A study of the Wichita photo, with the measureable scaling you provided there, shows this to be the case on the Lockheed, in fact.
Therefore I submit that a direct observation of the tape measure in your Wichita photo is the more reliable method: I get 23" from the forward coaming / patch rivet row, as we've assumed it to be placed, to the rivet row at STA 320, if that was used as you've assumed for this exercise. Please again see attached.
...So the horizontal dimension of the patch would be 24 7/8 (320 minus 295 1/8).
This is what I just described - it does not appear to be a good way to derive this distance. Consider what you can observe against the tape measure in the Wichita photo instead and forget 'stations' for a moment - see if you get closer to 23" from the forward coaming / patch rivet line to the rivet line at (or near) STA 320 by actual measurement as I did.
The horizontal length of the artifact is 24 3/8 so the artifact fits within the horizontal dimension of the patch with half an inch to spare - assuming all of our assumptions are correct.
I think those assumptions are measurably off for reasons cited. It appears now to me, that the horizontal dimension of the patch, if STA 320 was picked up and if the forward row of rivets is as we've believed it to be, would be closer to just under 23 1/2". This is because the two rivet rows, being 23" inches apart, would normally have an edge distance for the fasteners (fore and aft rows) from hole center to the edge of the skin of 2 1/2 to 3 rivet diameters: 3/32nds rivets x 2.5D x 2 edges = min. edge distance of 15/32nds / or round up to a half inch if you prefer - call it a patch length of 23 1/2".
If the assumptions are correct, the line up of the tear and "ghost" vertical stiffener with Station 307 is problematic. 307 minus 295 1/8 = 11 7/8 but the distance on the artifact from the edge that presumably failed against an underlying structure at 295 1/8 is 13 inches from the line of the "ghost" vertical and tear - an inch and an eighth too much to line up with Station 307. Maybe the tear and "ghost" stiffener are not associated with Station 307, or maybe our assumptions are off - but it certainly doesn't disqualify the artifact as the patch.
I'm not sure what that vertical mark is from but it does not appear to relate to the STA 307 structure, given how the artifact would have to be laid on to work at all. It has always been odd to me that if of the Electra that it was never riveted. I think it has to be thrown out somehow as irrelevant to fitting the Electra. It is interesting, but more as some enigmatic fact of something we've yet to understand, if we ever do. In of itself it is not disqualifying, nor is it qualifying at all in my view.
I have a far deeper concern with the overall dimensions as I've found them on the Wichita photo by the scaling applied there and regret that I did not look more closely at the time:
- The photo tape appears reliable as it also accurately reflects the 1 inch spacing that we know of on the artifact in various places.
- The tape applied directly to the Electra skin above the artifact clearly validates the measurements I've given here from skin aft edge near STA 293 5/8 to STA 307 rivet line to STA 320 rivet line (visual actuals - not presuming to use station assumptions) - count the 'ticks'. The tape is a little fuzzy there, but the 320 line may be a smidge over 12.5" from the 307, so add 1/4" perhaps.
- If the patch picked up the same forward row as the coaming, and picked up STA 320 rivet line, the distance is only 23" (or 23 1/4" with a nod to the fuzzy tape around 320).
If this is the case - and I invite you and others to inspect this work, of course - then it may be more problematic to 2-2-V-1 that we're not seeing a few surviving rivet holes remaining from those rows somewhere near one extreme end or the other of the artifact.
I am concerned that this may be a disqualifier.
I still have doubts about the patch having picked up STA 320, but we may never know and I now don't think it matters, given what I have been able to share here. But perhaps we'll learn more.
