Is 2-2-V-1 Piece of the Sydney Island C-47 Wreck? Update #2

Tom Palshaw’s report that TIGHAR Artifact 2-2-V-1 matches a section of the upper wing of a C-47 transport plane has elicited some interesting responses at TIGHAR’s discussion forum. A TIGHAR member stated that Tom had made a good case that a C-47 wing was the source of TIGHAR artifact 2-2-V-1 but suggested that Tom should further document his findings. He also suggested that Tom provide photographic evidence of C-47 wing features, such as the spacing between rows of rivets and the rivet pitch, i.e., the distance between rivets in each row. This led Ric Gillespie to make a post on the forum, the key points of which I’ll quote below:

If 2-2-V-1 is from the wing of a C-47, all aspects of the artifact must match. Beyond row spacing and pitch, the following must also match:

• Rivet size (shaft diameter):
The rivet on 2-2-V-1 has a shaft diameter of 3/32 inch - source NTSB Laboratory.

• Rivet length (shaft length):
The rivet on 2-2-V-1 has a shaft length of 3/16 inch - source NTSB Laboratory.

• Rivet material:
The rivet on 2-2-V-1 has a dimple in the center of the head, signifying it is made of A17ST alloy - source "Aircraft Maintenance and Repair" Northrop Aeronautical Institute, 1955. See attached PDF of rivet coding.

• Rivet head type:
The rivet on 2-2-V-1 is a "brazier" head. A brazier head rivet has a low profile, minimizing drag. There are two kinds of brazier head rivets,  the "full brazier head" and the "modified brazier head".  As early as 1930 and as late as 1941and possibly later, the "modified brazier head" was known as the "mushroom head."  The rivet on 2-2-V-1 is what is now known as a "full brazier head" rivet. Lockheed Electras had dimpled "full brazier head rivets" identical to the rivet on 2-2-V-1.  See photo below.

• Sheet thickness
The 2-2-V-1 sheet has a thickness of 0.032" - Source NTSB Laboratory

Tom saw these comments and in response wrote a detailed explanation of how various measurements he made were done. This additional information now appears in Tom’s report as Appendix II.

In this post, I’ll provide what I hope is a summary of Tom's Appendix II that will be helpful to layman like me out there who are following the 2-2-V-1 story. I’ll also provide additional information on how 2-2-V-1 appears to match the NEAM C-47 wing that Tom only became aware of after his report was published online.

The first bullet item is about rivet shaft diameter.  During Gillespie and Palshaw’s joint examination of the NEAM C-47 wing, Ric Gillespie questioned whether certain rivets were -4 rivets rather than -3 rivets. One of the main points Tom makes in his report is that the rivets in question are indeed -3 rivets. Appendix II of Tom’s report explains how  this was determined. Tom removed a rivet from the C-47 wing and inserted a drill that matched the rivet hole. This was a number 40 drill, the recommended drill size for -3 rivet holes. The matching drill for a -4 rivet hole is a number 30 drill, which does not fit into a -3 rivet hole. Tom provided a table from the Canadair Challenger Structural Repair Manual (1981), 51-42-11, page 6, figure 4, reproduced below, showing the correspondence between drill numbers and rivet hole sizes. Tom verified the -5 rivets on the C-47 wing using this same drill matching method.

Interested readers can check the photo below to see where Tom removed -3 rand -5 rivet removed from the C-47 wing to verify their sizes.

The second bullet item about rivet length states: “The rivet on 2-2-V-1 has a shaft length of 3/16 inch - source NTSB Laboratory.” I checked the NTSB report on TIGHAR’s web site [1] but see nothing there about rivet shaft length, so I will set this bullet item aside.

The third bullet item is about rivet material. Gillespie states:

“The rivet on 2-2-V-1 has a dimple in the center of the head, signifying it is made of A17ST alloy”

The photos included in Tom’s report aren’t sharp enough to show whether the rivet heads have dimples, so I asked Tom about the rivet heads, and he confirmed that they do in fact have dimples. He sent me the photo below of -3 rivets on the C-47 wing that demonstrates this to be the case. The ruler laid alongside the -3 rivets makes clear that the 1 inch pitch of the -3 rivets. Thus, in terms of the material type and rivet pitch the NEAM C-47 wing matches TIGHAR artifact 2-2-V-1.

The fourth bullet item about rivet head type states that the one -3 rivet still attached to 2-2-V-1 is a brazier head rivet. The Matching Characteristics section of Tom’s report states that the  C-47 wing -3 rivets are also brazier head rivets. Tom confirmed in an email exchange with me that that the C-47 wing -3 rivets are brazier head rivets, not modified brazier head rivets.  The table below indicates that -3 brazier head rivets and -3 modified brazier head rivets have quite different head diameters and so can be readily distinguished from one another based on their size. Readers can check the photo above against the table below to confirm that diameter of the -3 rivet heads on the C-47 wing are correct for -3 brazier head rivets, not modified brazier head rivets.

Gillespie’s fifth bullet item concerns sheet thickness.  The ALCLAD sheet that 2-2-V-1 is made of is 0.032 inches thick. The ‘What on Artifact 2-2-V-1 Matches the Wing of a C-47B?’ section of Tom’s report states that the thickness of the NEAM C-47 wing in the area of interest is also .032 inches. The excerpt below from Appendix II of Tom’s report states:

To determine the grip length it was necessary to first measure the skin thickness. This was done by using a micrometer at the edge of the skin. To measure the grip length a "calibrated" cleco was used to compare a known stack up of aluminum to that of the wing. The result was a skin thickness of 0.032" and a stringer thickness of 0.060". This is similar to the NTSB Report.

Some of this is a little over the head of a layman like me, but what’s clear is that Tom determined the 0.032 inch skin thickness of the NEAM C-47 wing skin in the area of interest by using a micrometer to measure the skin edge.  Note also that in the above excerpt Tom points out another matching point between the C-47 wing and 2-2-V-1: in both cases, the underlying stringer the skin is attached to was 0.060 inches thick.

That is my layman’s summary of Tom Palshaw’s Appendix II.

I also mentioned that after Tom’s report was published he realized that there was yet another way in which the C-47 wing and 2-2-V-1 match. This new information has to do with 2-2-V-1’s ‘Tab’ feature. A line of –5 rivet holes runs along one edge of 2-2-V-1, and a ‘Tab’ of material juts out from that same edge (see photos below).  At the far edge of the ‘Tab’ are what appear to be partial holes of another line of rivets. I sent Tom a close-up photo of the Tab with measuring tape laid over it (see photos below) that indicates a 1 5/16 inch spacing between 2-2-V-1’s line of -5 rivets and the rivet line at the far edge of the Tab. On the NEAM C-47 wing the line of -5 rivets that corresponds to the -5 rivet line on 2-2-v-1 has a line of -6 rivets running adjacent to it, separated by 1 5/16 inches (see photo below). Thus, the spacing between these two rivet lines on the C-47 wing matches the spacing of the rivet lines seen on 2-2-V-1's Tab. Tom thinks the partial rivet holes on the Tab’s edge are for size -6 rivets, but none of the holes is complete, so this is unclear.

2-2-V-1. The Tab is at the lower edge. The line of -5 rivet holes runs across the lower edge of 2-2-V1 and through the Tab

Spacing between rivet hole lines on the Tab

Spacing between -5 and -6 rivet hole lines on the NEAM C-47

Ric Gillespie's remark that the C-47 wing is "not even close" to a match for 2-2-V-1, as he put it, just does not seem to hold up, given what Tom Palshaw has reported.  If clearer documentation of the C-47 wing's features are needed, I think Ric Gillespie knows how to obtain it.

Comments, corrections, additional relevant facts, differing viewpoints, etc., are always welcome.  Send to gardnersghost@gmail.com

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References

[1] https://tighar.org/Projects/Earhart/Archives/Documents/NTSB_Report/ntsbreport.html