The Question of 2-2-V-1

[Jeff Carter]

"If the AN-A-13 designation did not appear until the early 1940s either our interpretation of the AD on the artifact is incorrect or the artifact dates from not-earlier-than the 1940s..."

Page 9 of the document refers to "...the recently issued specification AN-A-13..." So I guess it depends in what time frame "recent" falls...

Yes, AN-A-13 is mentioned several times on different pages.  One of the tables is footnoted as needed updating.  It doesn't mean older aluminum might not have met the standard, just that aluminum marked before the standard would have not had the stencil marking AN-A-13.  Also, I do not believe "AN-A-13" means anything else about the type of stock and the intended purpose other than the Army-Navy specification.

[Jeff Carter]

Some B-24's had large skin panels with seven vertical rivet rows on the starboard side above the rear bomb bay doors.  A clear example is on this page http://www.grubby-fingers-aircraft-illustration.com/liberator_A72-176_walkaround.html in the image http://www.grubby-fingers-aircraft-illustration.com/images/Liberator_A72-176_051_med.jpg.

The panel size is approx. 2 1/2 feet x 3 feet which would place the rivet rows approx. 3 1/2" - 4" apart.  There are no crossing patterns of rivets. 

This particular example is a B-24M, and a B-24M was damaged landing at Topham Field on Canton Island in 1945.  Some sources show a similar rivet pattern on B-24Js, but I have not been able to confirm or deny.  (http://www.flickr.com/photos/34076827@N00/5717863344/in/photostream/)

I do not have B-24 repair/structural manuals or blueprints to identify skin thickness or rivet size, but I do have factory photographs showing at least some B-24s/C-87s used .032" skin on the fuselage sides.

This rivet pattern does not appear on all B-24s.

These photos show the same rivet pattern on original B-24s (not restorations), so the pattern is not just a mistake in restoration  (http://www.flickr.com/photos/34076827@N00/5717863286/in/photostream/ and http://www.flickr.com/photos/34076827@N00/5717863344/in/photostream/).

[C.W. Herndon]

Good find Jeff. Great pictures!
Thanks.

[Ric Gillespie]

Some B-24's had large skin panels with seven vertical rivet rows on the starboard side above the rear bomb bay doors.

It was a long time ago now, but I'm sure we looked at that pattern on B-24 bomb doors she we were looking for an alternative match to 2-2-V-1.  I think you'll find those are #4 or larger rivets.

[John Ousterhout]

The "AN-A-13" stamp is clearly legible on the photo of the Japanese "Mavis" wreckage I posted on the previous page.  Does that help narrow the time window in which the stamp became common?  The Japanese were almost certainly unable to directly import "AN-A-13" after the start of the war, so the presence of the markings on the Japanese plane would indicate the stamp was used at least prior to December 1941.
I doubt there are sufficient records to clearly indicate when the last shipment of ALCLAD left for Japan.  Alcoa indicated to me that it could have been sold through a 2nd party distributor.

[John Ousterhout]

"Do you have a hypothesis for how a piece aluminum from an aircraft shot down 70 miles south of Baker ended up on Gardner island?"
No, only guesses.  One guess is that the piece found on Niku is NOT from one of these three Japanese aircraft.  It makes more sense to me that the piece came from some aircraft that made its way to Niku at some time, and broke apart there.  Another guess is that it was salvaged from a wreck on a different island and was brought to Niku by islanders.  The presence of Japanese aircraft getting shot down in the general area was previously considered unlikely, yet here are 3 examples.   I think this is enough evidence to consider Japanese aircraft wreckage, either having crashed on Niku, or imported from islands nearer than we thought possible.

[Ric Gillespie]

The "AN-A-13" stamp is clearly legible on the photo of the Japanese "Mavis" wreckage I posted on the previous page.  Does that help narrow the time window in which the stamp became common?  The Japanese were almost certainly unable to directly import "AN-A-13" after the start of the war, so the presence of the markings on the Japanese plane would indicate the stamp was used at least prior to December 1941.
I doubt there are sufficient records to clearly indicate when the last shipment of ALCLAD left for Japan.  Alcoa indicated to me that it could have been sold through a 2nd party distributor.

Although I haven't found aluminum specifically mentioned, the Export Control Act of July 2, 1940 almost certainly shut down all export of aircraft aluminum to Japan, even from 2nd party distributors.  The AN-A-13 labeling on the Mavis (Kawanishi HK6) appears to be "rolled on" (aligned with the edges of the sheet) whereas the labeling on 2-2-V-1 was (in the opinion of Alcoa engineers) was hand-stamped and probably from an early and/of small production run. 
So it looks like the AN-A-13 designation predates December 7, 1941 and probably predates July 2, 1940, and the artifact was probably hand-stamped earlier than that.  I think our hypothesis is okay. (whew!)

[James Champion]

The AN-A-13 Alcad on the Mavis could a repair to the Mavis. The repair material could have come from stock left behind at a US or commercial airfield as the Japanese advanced. That could make the material as old as early 1942.

[Ric Gillespie]

The repair material could have come from stock left behind at a US or commercial airfield as the Japanese advanced.

Yes, who's to say that could not have happened?  But how realistic is it?  Did the Japanese really have to scrounge metal from captured American airfields to repair airplanes early in the war?  I think its a good sign that we have to get that imaginative and speculative to make a case for post-Pearl Harbor metal on a Mavis.

[C.W. Herndon]

So it looks like the AN-A-13 designation predates December 7, 1941 and probably predates July 2, 1940, and the artifact was probably hand-stamped earlier than that.  I think our hypothesis is okay. (whew!)

It sounds better with each passing day :)

[Ric Gillespie]

Also, I do not believe "AN-A-13" means anything else about the type of stock and the intended purpose other than the Army-Navy specification.

What do you believe it means?  Not all 24ST ALCLAD carried that designation.

[Jeff Carter]

Some B-24's had large skin panels with seven vertical rivet rows on the starboard side above the rear bomb bay doors.  A clear example is on this page http://www.grubby-fingers-aircraft-illustration.com/liberator_A72-176_walkaround.html in the image http://www.grubby-fingers-aircraft-illustration.com/images/Liberator_A72-176_051_med.jpg.

The panel size is approx. 2 1/2 feet x 3 feet which would place the rivet rows approx. 3 1/2" - 4" apart.  There are no crossing patterns of rivets. 

This particular example is a B-24M, and a B-24M was damaged landing at Topham Field on Canton Island in 1945.  Some sources show a similar rivet pattern on B-24Js, but I have not been able to confirm or deny.  (http://www.flickr.com/photos/34076827@N00/5717863344/in/photostream/)

I do not have B-24 repair/structural manuals or blueprints to identify skin thickness or rivet size, but I do have factory photographs showing at least some B-24s/C-87s used .032" skin on the fuselage sides.

This rivet pattern does not appear on all B-24s.

These photos show the same rivet pattern on original B-24s (not restorations), so the pattern is not just a mistake in restoration  (http://www.flickr.com/photos/34076827@N00/5717863286/in/photostream/ and http://www.flickr.com/photos/34076827@N00/5717863344/in/photostream/).

I am interested in the labelled area on the attached picture (not the bomb bay doors).


I am not aware of any museum B-24s in the U.S. with this pattern that could be inspected, but I admit I have not found good pictures of this area on all of them, since it is usually obscured by the shadow of the wing.

[Ric Gillespie]

I am not aware of any museum B-24s in the U.S. with this pattern that could be inspected, but I admit I have not found good pictures of this area on all of them, since it is usually obscured by the shadow of the wing.

There's a B-24M at the Castle Air Force Base Museum in Atwater, CA./

Multiple rows of rivets roughly 3 to 4 inches apart with no crossing line for at least 24 inches are not that hard to find on WWII aircraft.   There's an area on the underside of a C-47 wing that fit that description. What is harder to find is a .032 skin with #3 brazier rivets in lines that taper.

[Ted G Campbell]

Ric,
I recall you were going over the Hartford (?) museum on 2-16-2014.  Did you make it? What did you learn?
Ted Campbell

[Ric Gillespie]

I recall you were going over the Hartford (?) museum on 2-16-2014.  Did you make it? What did you learn?

We had to cancel due to runway conditions.  The weather was okay but when we got to the airport we found the taxiways and runway were a sheet of ice.  You could barely stand up, let alone taxi. Bummer.  This winter has been unbelievable.  We'll reschedule.