The Question of 2-2-V-1

[Walter Runck]

Glad to see you out here on the trail Bill.

The current discussion is about how to determine rivet size (specifically shank diameter with the number size of the rivet representing the shank diameter in 32 nds of an inch so a #3 = 3/32") by looking at a picture or at an assembled aircraft.  Unless the parts have been separated, you can't see the hole or the shank because they're all smashed together.  So you're left trying to draw conclusions  by looking at the head or at the bucked side where the shank was smashed down over the hole.  The problem is we have two different sized rivets (#3 brazier and #4 modified brazier) with virtually the same head.

X-ray vision would probably answer the questions if you had a real aircraft to look at, but it even that doesn't work on pictures and for some of the candidates we're considering, that's all we have. 

Enjoyed looking at the pictures of the lodge.  Alaska is on my bucket list.

[Ric Gillespie]

Photos show many areas that might match up with the rivet pattern on 2-2-V-1.

I say again, parallel rows of rivets are not hard to find on many aircraft. We can check the Coronado in Pensacola but I'll be very surprised if there are any #3 rivets in a .032 skin.  Flying boats had to be built like tanks to withstand the force of water landings.

[Bill de Creeft]

Ahhh!!
I understand the question now !

From that point of view the question makes good sense...
Thank you !

As an aside, I've got an old  DHC Beaver Engine Cowling (R985) in my back yard that is dragging me in because it is close to the right pattern, small rivet size  etc. (even to the bulge in the metal and no stringers) but of course dates from late '40's as a design...it calls me, but I know it's not relevent....but still, the pattern is correct to the point where I phoned Ric about it...so if it's not The One, we should keep in mind other parts easily installed and removed...like cowling.
(While yer standing there looking at the Electra , what does it look like !?!)

Bill
(Still on the scent, but getting distracted)

[richie conroy]

Would you use #3 in double .032 skin ?

[richie conroy]

The reason i ask if it is possible ?

I found this ugly repair panel after mishap on Luke runway, and it is obvious that the repair skin is slid under original skin an the hole's drilled out to match

[Ric Gillespie]

I found this ugly repair panel after mishap on Luke runway, and it is obvious that the repair skin is slid under original skin an the hole's drilled out to match

That's not a repair patch.  It's a standard skin.

[Randy Conrad]

We wanted to know if anyone could tell us how the sheet of aluminum got bowed out.  Did somebody hammer on it?  Was there an explosion? So we took the artifact to the best expert we could find.  Walter Korsgaard was the lead FAA investigator on the 1988 PanAM 103 Lockerbie crash.  In 2004 he was recently retired so he was able to give us his opinion without bureaucratic concerns.  We showed him the artifact in his suburban Washington, DC home.  After examining the piece closely he said that it was part of an airplane skin that had been struck on the interior surface by a fluid (i.e. air or water) force sufficient to blow the heads off the rivets but not focused enough to punch a hole in the metal - a big blunt push.  We asked if it could have been caused by an explosion.  After looking at it with a magnifying glass he said, "No. There is none of the telltale pitting from pinpoint pyrotechnic projectiles."   We asked him what kind of accident might cause such damage.  He said, "In flight breakup of an aircraft at very high speed, but these materials are not consistent with an aircraft capable of those speeds, or an airplane that was broken apart by moving water."

The "push" of a fuel/air explosion is essentially the same as the "push" of a volume of water and my mind changed the memory to fit our current thinking. 




In reference to this quote.....My biggest question for you and others Ric...is let's say for example that this piece of metal is indeed from the Electra...Will it? or Will it not float in sea water with/ without rivets? I guess the reason I am asking this and in reference to the comment of having a explosion caused by moving ater...Is it possible that pieces of airplane skin could float to the surface after the aircraft going over the reefs edge and plundering thousands of feet at a high rate of speed. Kinda of like a submarine sinking, but going beyond the pressure she can endure. Basically, what I'm asking is...can this piece of metal survive floating from great depths after being imploaded by the pressure from within the plane? Love to hear your feedback...thanks!

[Ric Gillespie]

I think I can state with absolute confidence that sheet metal - with or without rivets - does not float.

[Ric Gillespie]

I've been thinking about the rivet inspection conundrum - that being:  the head of a 3/32" AN455 brazier rivet is indistinguishable from the head of a 1/8" AN456 modified brazier. That would seem to mean that - as we stalk the hangars of the National Museum of the United States Air Force, micrometers at the ready, we won't be able to test our hypothesis that the scale of materials used in 2-2-V-1 (3/32" AN455 brazier rivets in a .032 skin) is not found on WWII aircraft that served in the Pacific UNLESS we are unable to find any rivet heads of the "right" style and diameter. 

If we do find rivets that could be 3/32" AN455s or 1/8" AN456s, we might be able to judge the thickness of the surrounding skin by a simple "thunk" test.  A .032 skin "thunks" very differently from, say, a .040 skin.  Not high science but what we're looking for is a sense of scale in how aircraft of a given time and size were constructed. 

Of course, we're also looking for more than rivet type and size.  We're looking for patterns that might match the artifact.  If we find a location on an aircraft that might match the artifact we can dig deeper and find out whether the materials actually do match.

[Walter Runck]

I've been thinking about the rivet inspection conundrum - that being:  the head of a 3/32" AN455 brazier rivet is indistinguishable from the head of a 1/8" AN456 modified brazier. That would seem to mean that - as we stalk the hangars of the National Museum of the United States Air Force, micrometers at the ready, we won't be able to test our hypothesis that the scale of materials used in 2-2-V-1 (3/32" AN455 brazier rivets in a .032 skin) is not found on WWII aircraft that served in the Pacific UNLESS we are unable to find any rivet heads of the "right" style and diameter. 

It seems like we haven't answered the question of why you would use one style over the other.  That might not be conclusive, but it should help narrow the search.  In other words, if the modified brazier was developed for a specific purpose, it should have been used in some specific applications and not used in others.  Therefore, we should be able to eliminate candidate aircraft and/or areas before we start crawling around.

To put it simply, if you're designing an aircraft in the mid-1930's, why would you specify AN455s in some places and AN456s in others? 

[Greg Daspit]

Maybe the different grips of the heads make different dimples. A head that pinches more area of skin might make a wider flatter dimple and one that pinches a smaller area might make a deeper steeper dimple. Nothing that would provide a clear answer but just a theory.

[Ric Gillespie]

Maybe the different grips of the heads make different dimples. A head that pinches more area of skin might make a wider flatter dimple and one that pinches a smaller area might make a deeper steeper dimple. Nothing that would provide a clear answer but just a theory.

I think we have some confusion in our use of the term "dimple."  All American 2117 alloy rivets regardless of head type or shaft size are marked with a small indentation, known as a "dimple," in the center of the rivet head. We should probably use a different term to refer to the concavity in the skin on 2-2-v-1 around the holes where the rivet heads once were.

[Greg Daspit]

Maybe the different grips of the heads make different dimples. A head that pinches more area of skin might make a wider flatter dimple and one that pinches a smaller area might make a deeper steeper dimple. Nothing that would provide a clear answer but just a theory.

I think we have some confusion in our use of the term "dimple."  All American 2117 alloy rivets regardless of head type or shaft size are marked with a small indentation, known as a "dimple," in the center of the rivet head. We should probably use a different term to refer to the concavity in the skin on 2-2-v-1 around the holes where the rivet heads once were.

True, I wasn't thinking about the marker on the head when using the term dimple and it may be the wrong term for describing the concavity made in the skin.
Maybe if the light source was at a shallow angle the concavity in the skin made by different rivets may be more evident.  I doubt it will help and maybe only someone with a lot of experience could even tell something like this(to clarify this thought is applicable in looking at museum aircraft and not the artifact).  See sketch attached to help explain the thought better.
The one on left represents the 3/32" shank and the one on right the 1/8" shank

[Ric Gillespie]

It seems like we haven't answered the question of why you would use one style over the other.  That might not be conclusive, but it should help narrow the search.  In other words, if the modified brazier was developed for a specific purpose, it should have been used in some specific applications and not used in others.  Therefore, we should be able to eliminate candidate aircraft and/or areas before we start crawling around.

To put it simply, if you're designing an aircraft in the mid-1930's, why would you specify AN455s in some places and AN456s in others?

Or the mid-1940s for that matter.  Intuitively it seems like the only virtue of the AN456 is lower drag, so I'd use an AN456 in places where minimizing drag is more important than "grip."  Seems like there must be guidelines for designers.
I wonder when the AN456 modified brazier was introduced. Logically it had to be later than the AN455.

[John Ousterhout]

Richie asks "Would you use #3 in double .032 skin ?"
"A rivet should have a diameter of at least three times the thickness of the thickest sheet being joined." (Aircraft Rivets and Special Fasteners) appears to be much newer than 1937, but if the rule was being applied when any particular aircraft seen in a museum was made, then the "thickest sheet" joined using 1/8th inch (dash-4) rivets would be no more than 0.042 inch, and a -3 would be used for skins no thicker than 0.031 inch.