"That said, I doubt it is likely. It did first fly in 1938 and was introduced in 1942, but its construction - by what I've found so far, appears to be more typically flush, heavier military. I found a few pictures on Wiki so far - lots of flush rivets on outer skin.
It did have lovely lines despite other challenges to its performance."
Quite an innovative design for a pre-WW2 plane Jeff, mid engine to allow for the machine guns to be installed forward of the cockpit, tricycle undercarriage but, shame about the performance and inherent problems with the skin stress. Fully flush riveted as you noticed and nice streamlined lines as well, good looking plane.
From a recovered P-39 project regarding problems with the skin
During testing and combat reports, the one thing the Soviets were discovering was that the P39 suffered a structural weakness of the rear fuselage. After thorough testing, the Soviet LII (Flight Research Institute) and TsAGI (Central Aero and Hydrodynamic Institute) recommended a number of improvements to be undertaken at repair workshops from mid 1944.
These were recorded as: -
Defect and modification. - Twisting of rear fuselage and skin deformation.
All Q models up to and including the Q21 to have the following.
a. Two additional skins around radio compartment hatches.
b. fuselage longeron reinforcing member
c. two supports to forward tailplane spar attachment joints
d. two plates to reinforce the port forward fuselage beam.
Items a and c are clearly visible on ‘White 23’. These skins have been added over the red star and have covered segments of it. Whether or not it was deemed important, the star was not repainted.
All Q series models were to have the following work undertaken to the fin.
a. reinforce fin leading edge with additional skin.
b. add third fin/fuselage attachment point.
c. reinforce the forward and rear post with additional profiles.
d. additional plates at the middle of the rudder hinge.
http://lend-lease.airforce.ru/english/articles/sheppard/p39/
I was aware of these problems as I have read up on this model many years ago and wondered if the problems were due to the mid engine arrangement adding unexpected stresses along the length of the fuselage when manoeuvring.
From a P-39 restoration project regarding the riveting
"In fact, what shines through every facet of this 28+ year project is the ingenuity Ian applied not just to replicating the work of "Mr Bell and his many thousand work force of WW2" but to the very design and building of numerous tools. The P-39 features an external skin flush riveted throughout. These rivets require 'countersinking' and when holding thin metal STRESSED skin in place, this means deforming the inner edge of the hole - an operation called "dimpling".
http://www.qaww2.com/p39-project.html
Good find, Jeff Victor - and very interesting history on the Airacobra.
By some contrast to the Airacobra story on structures, attached is a close-up of the wing root / forward fuselage / engine ring cowl on a Spartan Executive. The Spartan was a product of roughly the same period in airframe development as the Electra (Lockheed Electra model L10E TC is number 590, the Spartan Executive model 7W TC is number 628). In studying this I see 'conventional' metal construction similar to what we'd see today - with some fine-point variations: rivet size in primary structure, and rivet type. Note that the Spartan displays some distinctly similar features to the Electra in terms of construction, right down to brazier rivets (smooth dome appearance, constant radius head vs. the double-radius semi-flattened top of the more modern universal head rivet). This includes a consideration of sizes used in primary structure - #3, #4 and #5 braziers being evident in various different rows (#3 rivets not so common on later war-era types).
This exercise has gotten very educational for me, I'm finally getting to use some of that boring old stuff from Embry-Riddle days about aviation regulation and the history of, and what it really did at the 'nuts and bolts' level (literally): both the Lockheed Electra and Spartan Executive were built under the old
Department of Commerce - Aviation Bureau (1926 - 1938) 'Aero Bulletin 7A' standards, so no wonder we see the shared features in construction. The bulletin itself does not prescribe exacting information as to rivet size, etc. - but the practices used by industry then to meet the strength criteria of the day are clearly common, much as they remain today albeit with newer materials and fastenings (and updated regulations and guidance). By all this we can tell a great deal about design and construction practices during early-to-mid 1930's for all-metal airplanes such as the Electra and Executive, all prior to the war and emergence of the CAR standards that were introduced in 1938.
Now I realize the real import of the introduction of the more modern Civil Air Authority in 1938: it just 'happened' to coincide with a major effort to modernize for war production. Things like tougher strength and fatigue standards (including practices with regard to common fastener sizes and how to build more robust airframes) were taken up; efforts to standardize and reduce complexity in production were undertaken; we have seen that sheet metal production took-off and the markings were modernized to an automated roller operation in lieu of hand-stamping of the past. The AN470 universal head rivet emerged at some point in this transition as an acceptable replacment for the older brazier, round head, flat head style rivets previously used in specialized areas of the airframe - such as seen in the L10E and Spartan Executive (braziers being common to air-passage external areas where flush-riveting was not necessary). Tooling and inventories were thus simplified and airframes became more robust as experience was gained and applied through new standards.
In the teaching I was subject to in the 1970's, #3 rivets were considered inferior for fatigue reasons - it is just a diminutive fastener with limited capabilities - and as I look back I realize experience came to bear: the next size #4 is far superior in strength and simply a better choice for resistance to destructive forces, hence no doubt the teachment of "do not use #3 rivets in primary structure" that I have cited so many times before. It was not part of the knowledge in the mid-thirties, nor is a well-designed and built airplane a death-trap because of its use - but time moves on and realities set some things toward robust improvement. War is a great catalyst as well. So we see pre-war machines that were elegantly and lightly-enough built, but we also see a standard that has disappeared with time and experience: they could not be certified in today's environment.
All of this further underscores for me just what a unique piece of aviation repair history we are looking at in 2-2-V-1 - it is nearly certain to be from your grandfather's Oldsmobile, not from your dad's (speaking for my generation...). More clearly now it would be an extremely odd-ball item to have occurred on any of the wartime birds known to have been in the Niku area. As has been noted, it is also American - the AN standards were distinctly such.
The B-24 (
see 'Crash at Sydney Island') has already been discussed as a possible donor and I among others do not see it as a likely source for 2-2-V-1 for reasons already discussed. But, the DC-3 was a product of the same era as the L10E and Spartan Executive - and as a later variant was larger and more modern than the predesessors DC-1 and -2. Especially so for the war-time produced C-47. Our greatest potential donor may be the
crashed C-47 at Sydney Island (another TIGHAR bulletin), which had been built only in October of 1943 (which the bureau number of that airplane, C-47A-60DL serial (bureau) number 43-30739 bears out); that makes this candidate a distinctly 'war time production' airplane which was well past the era of older rivet styles and construction practices of the mid-thirties.
Also, consider the newness of the airplane at the time of the loss - not even two months old; other than the known repair to a wing-tip, it is probably reasonable to surmise that it was not a great candidate to have had such a repair skin present. Further, any shop in the area doing sheet metal repair would have by default likely been supplied with later materials than we see in 2-2-V-1 due to more modern war mobilization efforts to place facilities and materiel in the field.
I've gone on too long - again - but consider these points and how they point further into the unique nature of 2-2-V-1; the potential for parent / donor airframes gets distinctly slimmer. The nature of what we see points to a repair of a fairly large area - such as very much consistent with a belly skin on NR16020. Short of import from far away Australia / New Gunea / New Zealand / Japan, there just are not a large number of potential donors in that part of the world for this combination of features - size, vintage, material type / style - it was a unique period and practice of aircraft building and repair that produced what we see now.
Enjoy the picture of the Executive - and more at
this link.