TIGHAR

Amelia Earhart Search Forum => Artifact Analysis => Topic started by: Matt Revington on January 21, 2014, 01:21:54 PM

Title: Grand Rapids trip (2-2-V-1)
Post by: Matt Revington on January 21, 2014, 01:21:54 PM
On the Facebook page Ric has posted that he is going to Grand Rapids to discuss an artifact recovered from Niku in 1991 with an FAA expert.  Which artifact is it and has something new come to light?
Title: Re: Grand Rapids trip
Post by: Russ Matthews on January 21, 2014, 01:40:14 PM
Which artifact is it ... ?

This one ...

http://tighar.org/wiki/2-2-V-1
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on January 21, 2014, 01:46:43 PM
This is a tremendously complicated artifact containing tons of information about where it came from and how it ended up looking the way it does now. It fits best on the belly opposite the cabin door but the rivet pattern is just a wee bit off - and that's an absolute disqualifier UNLESS there is rational explanation for why the rivet pattern is the way it is.
Title: Re: Grand Rapids trip
Post by: Chuck Lynch on January 22, 2014, 08:16:02 AM
Good luck. This seems very exciting all of a sudden.
Title: Re: Grand Rapids trip
Post by: Patrick Dickson on January 22, 2014, 09:02:29 AM
This is a tremendously complicated artifact containing tons of information about where it came from and how it ended up looking the way it does now. It fits best on the belly opposite the cabin door but the rivet pattern is just a wee bit off - and that's an absolute disqualifier UNLESS there is rational explanation for why the rivet pattern is the way it is.

Could the variation in the rivet pattern be exclusively due to the extent of the damage suffered by the Electra in the Luke Field "incident" ?  Is it possible that the supporting framework behind the repair panel was distorted or deformed enough to cause the variation in the rivet pattern ?   Would Lockheed repair technicians consider this area "non-critical" and allow the slight deformation of the ribs in the effort to make a quicker repair ?
 
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on January 22, 2014, 06:11:49 PM
Whatever was done had to conform to approved practices.  Aircraft repairs, then as now, were closely regulated and had to pass government inspection.  The question I hope we can answer is whether there were approved repair techniques that would result in the rivet pattern we see on the artifact.
Title: Re: Grand Rapids trip
Post by: JNev on January 23, 2014, 10:04:52 AM
Whatever was done had to conform to approved practices.  Aircraft repairs, then as now, were closely regulated and had to pass government inspection.  The question I hope we can answer is whether there were approved repair techniques that would result in the rivet pattern we see on the artifact.

I wish you luck with this effort, whatever is being done to identify the origins of this metal panel.  "Approved Practices" and vigorous inspection requirements certainly did apply and were taken seriously, so I personally doubt that an impromptu repair of lessor skin thickness and smaller rivet size would have been employed in an area of primary stressed skin (see Airworthiness Bullitin 7H  (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgccab.nsf/0/ea3191905e8c1a5a86256d89006aa55d/$FILE/Aeronautics%20Bulletin%20NO.7H.pdf) from the "Air Commerce Regulations" days of Earhart's time).

That does not preclude that 'anything is possible', or that exceptions could have been made, of course.  I also understand and appreciate how the 'best fit' was determined by having read of the effort on this site, but have doubts about that location.  This is due to the thickness (.032 being less than the original .040 skin in that area) and the irregular "#3" rivet hole pattern evident on the piece (which are also undersized compared to the 1/8th inch "#4" rivets originally used in that area of primary structure).  For another thing, #3 rivets have long been considered less-than adequate for primary structure and generally are not used in stressed skin situations (this taught me from early days in A&P school, granted some years after Earhart's time - but a long-standing practice).

On the positive is the era of this 'skin' - the markings suggest pre-WWII production and the remains of brazier head type rivets also suggests an older craft, pre-dating the war-time AN470 universal-type head (both in terms of production and any repairs).

As to a 'likely fit' I am more biased toward the curious covering that was installed over the Electra's large, one-off 'navigation window' in the head while the ship was in Miami, prior to the last world flight attempt (http://tighar.org/smf/index.php/topic,717.0.html).  This window was located on the right side of the fuselage - cut out and braced for a larger aperture than the other cabin windows, and actually placed in the lavatory area.  This large window was in a zone of .032 skin since it was AFT of the station where ".040" skins stopped and .032 was the norm.

Of further interest to me is the general layout of the rivets - the interim "#3" rivet layout is as if done "free hand" by someone in a hurry to address an oil canning effect over a large, secondary 'cover'.  What is 'suggested' by what I see is a rapid attempt to cover a large aperture simply for security / weather protection, but where structural considerations were not paramount; perhaps after a flight it was realized (or simply 'predicted' and addressed) that oil canning might be an issue: hence light-weight secondary rivets that could have attached light-weight stiffeners to prevent that.

Earhart was weight conscious; someone decided that window was no longer needed and it was covered while in Miami (details of that unknown).  The larger rivet holes on the periphery of the 'skin' suggest attachment to established, well-braced structure (such as the peripheral bracing of the described window); the interior rivet patterns appear 'hand laid' and are light-weight in character, i.e. secondary consideration - weight savings but adequate for light bracing.

Of course all of this is speculation on my part - but based on the reasons I've given, which are based on a career in maintenance, alteration and design.  The practices I've described are also consistent with the earliest guidance we have (see the "Aeronautics Bulletins" of old on FAA's Regulatory and Guidance Library site (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgCCAB.nsf/MainFrame?OpenFrameset)), right through current sheet metal practices (actually little has changed in eight decades as to those practices except materials and fastener types, e.g. brazier head giving way to universal, etc.).

So in my thinking there is no way to know this for sure short of having NR16020 to hold this up against for an absolute match - belly or window covering, or something else - but the 'window cover' came to make sense to me after seeing the artifact in D.C. June of 2012 and learning something of the Miami window covering exercise, and more about the structure in that area.

Best of luck with whatever investigative effort is going on - I agree it is loaded with information, if it can be teased out somehow.  I've always wondered if it might be a silent witness to this loss and somehow finally a key: there should not have been a great surplus of that kind of pre-war Dural with brazier rivets in it lying about in that part of the Pacific IMO, however it got there.
Title: Re: Grand Rapids trip
Post by: Greg Daspit on January 23, 2014, 01:00:37 PM
This is due to the thickness (.032 being less than the original .040 skin in that area) and the irregular "#3" rivet hole pattern evident on the piece

Jeff
Was the skin for 35R originally .032 or .040?
I thought the original skin in that area matched the artifact from 1992 Tighar Tracks Vol 8 (http://tighar.org/Publications/TTracks/1992Vol_8/0801_2.pdf)?
“• Skin thickness: Identical to Skin #35R.”
 
In regards to the 35R:
Is there something that shows the discrepancy ?
Which row or rows are off, how much and to which side are they not aligned?
(I could only find a comparison of the panel on top near the air vent)
Title: Re: Grand Rapids trip
Post by: JNev on January 23, 2014, 02:23:58 PM
This is due to the thickness (.032 being less than the original .040 skin in that area) and the irregular "#3" rivet hole pattern evident on the piece

Jeff
Was the skin for 35R originally .032 or .040?I thought the original skin in that area matched the artifact from 1992 Tighar Tracks Vol 8 (http://tighar.org/Publications/TTracks/1992Vol_8/0801_2.pdf)?
“• Skin thickness: Identical to Skin #35R.”
 
In regards to the 35R:
Is there something that shows the discrepancy ?
Which row or rows are off, how much and to which side are they not aligned?
(I could only find a comparison of the panel on top near the air vent)

I can't authoritatively dispute the TIGHAR Tracks bulletin regarding 35R. 

My understanding has been that the skins were .040" thick back to Sta. 293, where it transitioned to .032" thick; that would be consistent with this sort of stressed skin design - the forward section of the fuselage being relatively reinforced to carry passenger and other direct loads, tapering to less structure some distance out by moment / arm. 

But TIGHAR may have better information on the original skins than I do.  The drawings "know", if any can be found for this area - and TIGHAR has examined other Electras and may have direct knowledge of this as gained from other airplanes like Earhart's.

I wish Ric luck on this - the 'skin' has long fascinated me as a possible 'grail' item if a firm match could be made somehow.
Title: Re: Grand Rapids trip
Post by: Greg Daspit on January 23, 2014, 03:28:35 PM
Another reason it can be thinner is as the ribs get closer together as the fuselage tapers, there is less distance to span for the skin.
I like this artifact too. The dating of the type of aluminum used is significant and the 2-2-V-1 wire (http://tighar.org/Projects/Earhart/Archives/Documents/NTSB_Report/ntsbreport.html) found entangled in it. I think the dating of aluminum and the wire suggest possible 1937 aircraft debris nearby. Pretty exciting stuff all together. I look at where the aircraft skin was found, combined with Emily's seeing aircraft debris and the Bevington photo and the data from the last trip and think TIGHAR is closing in on it!

Title: Re: Grand Rapids trip
Post by: Tim Mellon on January 23, 2014, 07:26:01 PM
Greg, it's a shame Ric won't allow you to see the three landing gears, the cockpit, the propeller blade and the various cylinder, intake and exhaust valves.

I guess it's all in the name of "scientific method."

Title: Re: Grand Rapids trip
Post by: Greg Daspit on January 23, 2014, 09:36:50 PM
#3 rivets have long been considered less-than adequate for primary structure and generally are not used in stressed skin situations (this taught me from early days in A&P school, granted some years after Earhart's time - but a long-standing practice).

Jeff
That is interesting. Could the #3 rivets also be used to fasten a large patch to a damaged piece that may have a few small holes or abrasions but not damaged enough to take off and replace?(probably not). Then the patch rows might be parallel to where the original rows were because they only went through the skin. I wonder if the patch rivets may need to be close to the ribs but not have to go thru the rib. And if the top of the original heads may have left a scar on the inside of the patch if that were the case(probably not a good way to laminate two pieces). I'm very interested in what the results of the trip are for repair practices. The more details you point out about it, the more interesting this piece becomes. I'm glad you mentioned the rivet type. (pre war type from what I read). So much about this fits the era of the plane even if an exact fit can't be found. And why would a patch or repair "fit" exactly anyway?
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on January 24, 2014, 09:46:27 AM
Productive meeting in Grand Rapids yesterday.  Aris Scarla is Manager of the FAA District Flight Standards Office.  He has 30+ years of experience as an accident investigator and repair/modification inspector.  He also has an interest in the history of aircraft construction and repair regulations and practices.  Of course, Mr. Scarla's observations and opinions were offered as an individual, not as an FAA spokesperson.

I'll be writing up a full report but, to cut to the chase:
Previous dismissals/disqualifications of Artifact 2-2-V-1 as being from NR16020 were based upon comparisons of the rivet pattern with existing Model 10s - but we know that the area on NR16020 that best matches the artifact did not look like standard Model 10s.  We have the repair orders that describe, in general terms that work that was approved to be accomplished.  The final report of what was actually done is missing and may or may not still exist.  In any case, there are a number of factors and common repair techniques that could account for the slight discrepancy in the rivet pattern between the artifact and a standard Model 10.  In other words, the artifact cannot be disqualified based on the rivet pattern. All other aspects of the aluminum sheet and surviving rivet exactly match a particular location on the belly of NR16020. In addition, the way the structures failed and the present condition of the artifact are entirely consistent with the Electra's hypothetical breakup in the surf.   

Bottom line:  Unless the missing report turns up, 2-2-V-1 cannot be considered a "smoking gun," but neither can it be dismissed.  We've not been able to find any place on any other aircraft that even comes close.  Like so many other aspects of our investigation, there seems to be no conclusive connection to Earhart but neither does there seem to be a viable alternative explanation for its presence on the island.
Title: Re: Grand Rapids trip
Post by: Tim Gard on January 25, 2014, 12:53:50 AM
neither does there seem to be a viable alternative explanation for its presence on the island.

Encouraging news.
Title: Re: Grand Rapids trip
Post by: Monty Fowler on January 25, 2014, 07:20:34 AM
The report is out there, somewhere ... and it will turn up at the most opportune moment. Look at all the other bits of paper and whatnot that are STILL turning up about Amelia and Fred - the Chater Report, the New Zealand photos, Betty's notebook ...

If it had Amelia's name on it, someone, somewhere, probably kept it.

LTM, who pushes paper for a living,
Monty Fowler, TIGHAR No. 2189 CER
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on January 25, 2014, 08:09:21 AM
If it had Amelia's name on it, someone, somewhere, probably kept it.

That seems like a logical assumption, but Earhart's name was probably not on the documents we're looking for. 

We know this much:
The FAA periodically destroys old records. Some time in the 1970s an order came down to destroy records from the period that included the spring of 1937 when NR16020 was repaired.  There is a notation in the FAA file indicating that the Smithsonian (presumably NASM) asked that certain boxes of records be given to them rather than being destroyed.  This request was apparently honored because Lockheed Report #490, dated 4-16-37, which describes modifications to strengthen the nacelle ribs on NR16020 ended up in the NASM Library Special collections section.  Neither Earhart's name nor the plane's registration number appear anywhere in that report.  The plane is referenced only as "Serial No. 1055". 
It appears that when people at NASM (archivists, librarians, interns?) were reviewing the contents of the boxes, whoever snagged that report happened to know that Earhart's Electra was c/n 1055.  It's possible that other reports detailing changes made during the repairs were not recognized as Earhart-related documents.  For that matter, we don't know whether all of the boxes of saved documents were ever examined and cataloged.  Budget cuts have meant that a lot of work like that has been on hold.  In any event, we intend to find out.
Title: Re: Grand Rapids trip
Post by: Jennifer Hubbard on January 25, 2014, 06:18:24 PM
On the destruction of FAA records:

Government records are generally controlled by specific record retention schedules. For example, the FAA's current schedules are posted here:

FAA record retention schedules (http://www.faa.gov/about/initiatives/records/schedules/faa_schedules/)
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on January 25, 2014, 06:35:35 PM
Further research today suggests that there is no missing record describing repairs to NR16020 but there are indications that undocumented shortcuts may have been made.
Title: Re: Grand Rapids trip
Post by: Randy Conrad on January 25, 2014, 11:58:13 PM
In conjunction with your recent trip to Grand Rapids Ric...I've been very curious since the D.C. Conference on how this certain piece of metal that you had on display and mentioned in the recent news release...was rather in somewhat of a perfect condition. What I'm driving at here is I was taken by the near mint condition of the rivet holes and how over this long period of time we really don't see that much deterioration on this metal. I used to roof for many years and know what riveting does to sheet metal if it gets torn off or pulled off of an object. I find it rather interesting that these holes on this metal are still "perfect" per say. Usually, when that type of metal gets torn off or ripped off...the holes usually go with it. Not this case...So the question is WHY? I'm trying to fit Earhart and Noonan into the picture of stomping on the sheet metal trying to get out of the bottom or the sides of the plane. I guess I don't see them getting out with all the rivets just falling out of the holes with that "JUST LIKE THAT" philosophy. Or such is the case that islanders just pulled the skin right off the plane. There had to be some explanation!!!  Anyway, someone fill me with their ideas on this scenario. Thanks!!!!
Title: Re: Grand Rapids trip
Post by: Martin X. Moleski, SJ on January 26, 2014, 04:55:13 AM
I guess I don't see them getting out with all the rivets just falling out of the holes with that "JUST LIKE THAT" philosophy. Or such is the case that islanders just pulled the skin right off the plane. There had to be some explanation!!!  Anyway, someone fill me with their ideas on this scenario. Thanks!!!!

The supposition about the deformation seen in the artifact was given in the very first reports about it.

2-2-V-1 (http://tighar.org/wiki/2-2-V-1)

Research Bulletin 32 (http://tighar.org/Projects/Earhart/Archives/Research/Bulletins/32_SatPhoto/Nikusatphotopage2.html)

Found Objects - Aircraft Skin (http://tighar.org/Publications/TTracks/12_2/obj6.html)

I'm three-for-three right now.  Every reference to the artifact on TIGHAR's website mentions a theory of how it might have come to be in its current condition.

Any one of those will answer your question.  Or you could search for more (http://tighar.org/news/help/82-how-do-i-search-tigharorg).
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on January 26, 2014, 08:07:33 AM
What I'm driving at here is I was taken by the near mint condition of the rivet holes and how over this long period of time we really don't see that much deterioration on this metal.

There are many remarkable things about this artifact.  The mint condition of most of the rivet holes is conclusive evidence that they were not drilled out or pried out.  A fluid force (air or water) struck the interior - that is, inside the airplane - surface of the skin with sufficient force to blow the heads off the rivets and fracture the sheet.  The artifact was obviously once part of a larger sheet of aluminum. The force that caused the failure was so strong and so narrowly focused that, rather than the entire sheet separating from the aircraft, the aluminum fractured and tore in this one section.  None of the four edges of the artifact is a manufactured edge. This thing busted out of the middle of a larger sheet.  Think about that.

As for the present condition of the metal, there is minimal corrosion.  Most of the aircraft aluminum we've found in the village shows very little corrosion.  Aircraft aluminum holds up well on land at Nikumaroro. The artifact, unlike other aircraft metal found in the village, has remnants of marine growth suggesting that it spent some period of time underwater.   
Title: Re: Grand Rapids trip
Post by: John Joseph Barrett on January 26, 2014, 06:23:12 PM
Ric,

A couple of thoughts about this artifact. Once in my misspent youth we decided that it would be fun to toss a 1/4 stick of dynamite in my mother's newspaper mailbox (the plastic kind). While the explosion was quite intense and the mailbox displayed an amazing amount of hangtime, the part I remember the most was the pole still standing and swaying back and forth, with the bolt that had held the bracket to the box still intact, complete with washer. Why this is noteworthy is that when I looked at the bracket itself, it was perfectly fine as well, the bracket having been popped right over the washer and nut with no damage to any of the parts. The box was not nearly so fortunate. Depending on the force applied, I think it quite possible for an aluminum sheet to pop off of rivets without distorting the sheet. Also, keep in mind that rivet heads tend to be very thin. I can envision the heads bending up or shearing from the shaft before the sheet would distort. Lastly, in the location where this panel would have been if it were part of the plane, is there any structure that would tend to concentrate the hydraulic force in such a manner to create the artifact as we see it? I'm picturing an access panel in the floor or similar that, if open, could allow a sudden blast of water in to create the artifact.

LTM- Who is still mad about the wanton destruction to this day.
Title: Re: Grand Rapids trip
Post by: Greg Daspit on January 26, 2014, 07:25:31 PM
If the tail section broke at the cabin door (weak point) then could one tear be from that failure and the other 3 tears from a water blast slamming thru the now open end, hitting that section at the right angle?

 I was thinking the piece that looks like a leading edge of a wing in the Glickman Debris Field may have had a similar failure. A blast of water thru the wheel well that blew out the leading edge of a wing.
Title: Re: Grand Rapids trip
Post by: Tim Mellon on January 26, 2014, 07:34:26 PM

 I was thinking the piece that looks like a leading edge of a wing in the Glickman Debris Field may have had a similar failure. A blast of water thru the wheel well that blew out the leading edge of a wing.

Is the narrative changing? I thought the anomaly from the Glickman Debris Field was supposed to be a fender.

In any case, a blast of water through the wheel well would end up in the engine compartment where there is no leading edge of a wing. Just an engine mounted on a frame, surrounded by a nacelle.

Title: Re: Grand Rapids trip
Post by: Greg Daspit on January 26, 2014, 08:23:29 PM
In any case, a blast of water through the wheel well would end up in the engine compartment where there is no leading edge of a wing. Just an engine mounted on a frame, surrounded by a nacelle.
I was only speculating Tim but I don't think you are right about no skin behind the engine. See this picture from the Purdue Archives (http://e-archives.lib.purdue.edu/cdm4/item_viewer.php?CISOROOT=%2Fearhart&CISOPTR=529&DMSCALE=25&DMWIDTH=600&DMHEIGHT=600&DMMODE=viewer&DMFULL=0&DMX=460&DMY=223&DMTEXT=&DMTHUMB=1&REC=11&DMROTATE=0&x=479&y=362)
I think the skin should be there because it is stressed skin (http://en.wikipedia.org/wiki/Stressed_skin) and removing skin there would weaken the wing even though there is a main beam there.
Does anyone know if the 4 or 5 pulleys in that picture stayed there after the plane was finished?
Title: Re: Grand Rapids trip
Post by: Tim Mellon on January 27, 2014, 03:57:09 AM
All those holes essentially makes that entire engine area immune to the types of water pressure you are conjecturing. Also, water would pour in through the front of the engine in even greater volume.
Title: Re: Grand Rapids trip
Post by: Tim Collins on January 27, 2014, 07:18:39 AM
...
The mint condition of most of the rivet holes is conclusive evidence that they were not drilled out or pried out.  A fluid force (air or water) struck the interior - that is, inside the airplane - surface of the skin with sufficient force to blow the heads off the rivets and fracture the sheet. 

I find that hard to believe, frankly, that so many of the rivets would give way with such little little or no evidence of resistance on the skin. And I can't imagine that rivets used in aircraft construction, or repair for that matter, were meant to be "break away" elements. 

...The force that caused the failure was so strong and so narrowly focused that, rather than the entire sheet separating from the aircraft, the aluminum fractured and tore in this one section.  None of the four edges of the artifact is a manufactured edge. This thing busted out of the middle of a larger sheet.  Think about that.
...

Ok, so back up about three feet. How and why would said force be so narrowly focused at that particular spot? 

Title: Re: Grand Rapids trip
Post by: John Ousterhout on January 27, 2014, 07:38:41 AM
Greg - the pulleys are for the controls for the engine (throttle, mixture, carb heat, mags, maybe cowling flaps, maybe prop).  The cables that operate the pulleys are routed from the cockpit.  As you can see, the cables are fairly small diameter - they don't have to handle much load, need to be lightweight, and need to be flexible.  They would even make good fishing line in some cases.
Title: Re: Grand Rapids trip
Post by: Monty Fowler on January 27, 2014, 07:43:09 AM
I'm not a materials expert, but I would expect TIGHAR is well on the way to finding one to contribute to the overall body of knowledge.

LTM,
Monty Fowler, TIGHAR No. 2189 CER
Title: Re: Grand Rapids trip
Post by: Greg Daspit on January 27, 2014, 08:01:02 AM
The force I am conjecturing would be equal to what would throw boulders the size of bull dozers up on the reef as seen in this aerial tour of Nikumaroro (http://www.youtube.com/watch?v=DL9FGsvB3E8) (at 16 minutes). 
If this force hit the plane that was wedged in a reef goove and the force was blocked by some other part of the plane, then it could become focussed and blow part of a panel out. Also consider that a large panel could be over a hole or groove. That surf force hits the full panel and possibly only the unsupported part of the panel fails even though the whole panel gets hit.
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on January 27, 2014, 08:36:05 AM
I was only speculating Tim but I don't think you are right about no skin behind the engine.

There is a massive firewall behind the engine.  The wheel well is under the nacelle, behind the firewall.
But none of this is anywhere near where we think the artifact came from.
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on January 27, 2014, 08:37:02 AM
I'm not a materials expert, but I would expect TIGHAR is well on the way to finding one to contribute to the overall body of knowledge.

Trust me.   ;D
Title: Re: Grand Rapids trip
Post by: Greg Daspit on January 27, 2014, 09:09:58 AM
I was only speculating Tim but I don't think you are right about no skin behind the engine.

There is a massive firewall behind the engine.  The wheel well is under the nacelle, behind the firewall.
But none of this is anywhere near where we think the artifact came from.

I understand the artifact is suspected of being located in the belly, roughly opposite the cabin door. The water may have just come blasting thru the cabin door opening.
In reply 22, I also referred to  an image in the Glickman debris field that may have failed in the same way as the artifact may have failed.
The picture (http://e-archives.lib.purdue.edu/cdm4/item_viewer.php?CISOROOT=%2Fearhart&CISOPTR=529&DMSCALE=50&DMWIDTH=600&DMHEIGHT=600&DMMODE=viewer&DMFULL=0&DMX=1822&DMY=994&DMTEXT=&DMTHUMB=1&REC=11&DMROTATE=0&x=384&y=380) from the Purdue archives has 5 pulleys in that same area as the wing’s  leading edge behind the engine. There is a pulley shape next to the Glickman Debris Field “fender” shape and this shape has evidence of holes like the leading edge of the wing. I was suggesting the possible “fender’ shape could be a leading edge of a wing that kept its shape due to fluid pressure on it, similar to what may have happened to the artifact.
Apologies  if I got off topic
Title: Re: Grand Rapids trip
Post by: Greg Daspit on January 27, 2014, 10:22:02 AM
Sketch attached to show some possiblities/ speculation
(edited to correct 2-2-V-1 labeled and location)
Title: Re: Grand Rapids trip
Post by: Jon Romig on January 27, 2014, 11:44:45 AM
The Missing Rivets:

I have trouble understanding why all the smaller rivets are missing and the artifact shows no damage around the rivet holes. If the piece is blown off the aircraft frame (or off stiffeners), and there is no damage from rivet pull-through on the artifact, then every single rivet must have instantaneously reverted to nearly its original diameter, pulled through the frame, and fallen off. This seems somehow unlikely to me.

Why should the rivet pull through the frame, when the artifact must have been the lighter gauge material? Is the non-factory end of the rivet so much weaker - how does that align with the overall design strength for the rivets, which would mandate a rivet design where the two ends have near equal strength?

Is it possible that we are not looking at holes for rivets used on aircraft skin, but for some other use, where another rivet type (like a split head rather than a compressed head) may have been used?

Or that the holes were not for rivets at all, but rather for something else (tacks, nails, screws, thread, ventilation, RF, light, glue, etc.)? I've drilled plenty of 3/32 holes in my days for things other than rivets.

Jon
Title: Re: Grand Rapids trip
Post by: Jon Romig on January 27, 2014, 11:57:53 AM
The Missing Rivets:

I have trouble understanding why all the smaller rivets are missing and the artifact shows no damage around the rivet holes. If the piece is blown off the aircraft frame (or off stiffeners), and there is no damage from rivet pull-through on the artifact, then every single rivet must have instantaneously reverted to nearly its original diameter, pulled through the frame, and fallen off. This seems somehow unlikely to me.

Why should the rivet pull through the frame, when the artifact must have been the lighter gauge material? Is the non-factory end of the rivet so much weaker - how does that align with the overall design strength for the rivets, which would mandate a rivet design where the two ends have near equal strength?

Is it possible that we are not looking at holes for rivets used on aircraft skin, but for some other use, where another rivet type (like a split head rather than a compressed head) may have been used?

Or that the holes were not for rivets at all, but rather for something else (tacks, nails, screws, thread, ventilation, RF, light, glue, etc.)? I've drilled plenty of 3/32 holes in my days for things other than rivets.

Jon

It would be useful to obtain the design pull-out strength of the rivet we presume would have been used, and calculate the total force (and PSI since we know the panel size) required to simultaneously pop them all at the same time.
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on January 27, 2014, 12:25:25 PM
Sketch attached to show some possiblities/ speculation
(edited to correct 2-2-V-1 labeled)

The hypothetical position of 2-2-V-1 is on the belly directly opposite the cabin door on the starboard side of the aircraft.
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on January 27, 2014, 12:33:48 PM
If the piece is blown off the aircraft frame (or off stiffeners), and there is no damage from rivet pull-through on the artifact, then every single rivet must have instantaneously reverted to nearly its original diameter, pulled through the frame, and fallen off.

The rivets did not pull through.  The rivets apparently fractured at the base of the head.  The force of the water on the interior surface of the skin literally blew the heads off the rivets.  There is one surviving rivet that pulled through the stringer because it was improperly bucked.

Is it possible that we are not looking at holes for rivets used on aircraft skin

No.  There is no question that this is a section of aircraft skin. 

Title: Re: Grand Rapids trip
Post by: Chris Johnson on January 27, 2014, 02:10:23 PM
How does this sheet differ from military aluminium from WW2?
Title: Re: Grand Rapids trip
Post by: JNev on January 27, 2014, 02:16:43 PM
If the piece is blown off the aircraft frame (or off stiffeners), and there is no damage from rivet pull-through on the artifact, then every single rivet must have instantaneously reverted to nearly its original diameter, pulled through the frame, and fallen off.

The rivets did not pull through.  The rivets apparently fractured at the base of the head. 

Seems clearly the case - and not unusual for such small rivets (one good reason #3 (3/32") rivets are not normally used for primary structure: the skin's bearing strength far exceeds the rivet's in tension.

Here's some good information from FAA (see Section 4 - paragraphs 4-50 - 4-59 in particular) (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/99c827db9baac81b86256b4500596c4e/$FILE/Chapter%2004.pdf) - which has changed very little over the many decades except for the introduction of modern fasteners like blind rivets, etc.  Note how relatively few 3/32" rivets were used per-inch in the artifact compared to the number recommended in table 4-9, for instance.  This suggests IMHO that the artifact's intermediate rivets were for very light secondary bracing, or done by an unknowing novice if for primary structure (can you say i-d-i-o-t).

Quote
The force of the water on the interior surface of the skin literally blew the heads off the rivets.  There is one surviving rivet that pulled through the stringer because it was improperly bucked.

Granted, whatever the force that was applied was from does appear to have been somewhat uniformally hydraulic in nature (not a pick-ax to the middle of the membrane, for sure) - there is plenty of water there, and we do know it can act with a great deal of force - even concentrated force, but many things are possible...

Is it possible that we are not looking at holes for rivets used on aircraft skin

Quote
No.  There is no question that this is a section of aircraft skin.

I certainly agree - and that of a pre-WWII vintage as TIGHAR has pointed out.
Title: Re: Grand Rapids trip
Post by: Chris Johnson on January 27, 2014, 02:28:30 PM
What am I missing, what makes it 100% non military pre WW2 vintage?
Title: Re: Grand Rapids trip
Post by: JNev on January 27, 2014, 03:56:35 PM
What am I missing, what makes it 100% non military pre WW2 vintage?

I don't know that it can be said that it is "100% non military", but as to "pre WWII vintage" -

The way the metal is marked, as said here (http://tighar.org/Publications/TTracks/12_2/obj6.html) (and quoted below, in excerpt, emphasis added) at the very least strongly suggests pre-war, certainly consistent with metal markings of Earhart's era -

Quote
...The aircraft was of all-metal construction and was manufactured in the United States, probably before 1939. The surviving rivet is an AN 455 AD 3/3. The head style, known as the “brazier” head, was replaced in most applications by the “universal” head (AN470) sometime after 1940. The letters “AD” noted on the exterior (convex) surface are the last two letters in the word ”ALCLAD” which was stamped onto the aluminum in red ink at the time of manufacture by Alcoa Aluminum as part of the product labeling. Complete examples of this same size and style of lettering (ALCLAD 24S T3) have been noted on aluminum used in repairs or modifications to two surviving Lockheed 10s: c/n 1015, recently rebuilt as a replica of Earhart’s aircraft and currently registered NX72GT, and c/n 1052 in the New England Air Museum collection. Similar labeling has also been found on a small patch on the nose of a Douglas C-47 in the Dover AFB Museum collection. The font, or type style, of the lettering does not appear to match any of the styles used by Alcoa for aluminum manufactured during or after World War II. The fact that the lettering is not aligned with the grain of the metal indicates that the labeling was hand-stamped, a practice replaced by rolled-on labeling when aluminum production boomed after 1939.

As has been said - none of this makes the piece a 'smoking gun', but it is somebody's rusty pistol and it is consistent with something one could reasonably expect to find on the Electra. 

TIGHAR seems to have a good idea 'where from' if from the Electra, I happen to have my own notion of that possibilty (merely a different area of the same airplane) as many have seen I'm sure.  I've certainly not spent the time pouring over metal and rivets on a real Electra that TIGHAR has, of course.  Either way it would be awfully nice to find a 'fit' if it can be done.  That metal can tell a lot if it's its figurative tongue can be loosened...
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on January 27, 2014, 03:58:31 PM
What am I missing, what makes it 100% non military pre WW2 vintage?

Nobody said it's not military.  Both pre- and during WWII the aluminum used in civil and military aircraft was identical. 
What makes it not WWII is the use of small 3/32 rivets in primary load-bearing contraction.  As Jeff pointed out, you won't see that on any American WWII aircraft.  Also, the style of rivet (AN455AD 3/3 or AN456AD 3/3 flat brazier head) was largely obsolete by WWII.  We can say with some certainty that the aircraft this skin came from was pre-WWII vintage - and when you can say that about an artifact that was found on Gardner Island you've said a mouthful.
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on January 27, 2014, 04:01:36 PM
I happen to have my own notion of that possibilty (merely a different area of the same airplane) as many have seen I'm sure.

I'm certainly open to other suggestions.  The tricky thing is finding a span of .032 skin that long (24 inches) with no crossing line of rivets.
Title: Re: Grand Rapids trip
Post by: John Ousterhout on January 27, 2014, 05:45:22 PM
Were the wheel wells lined?  I couldn't find any photos with an appropriate view.  (I'm also sure that you've already looked into it.)
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on January 27, 2014, 05:47:00 PM
Were the wheel wells lined?  I couldn't find any photos with an appropriate view.  (I'm also sure that you've already looked into it.)

No, the wheel wells in a Model 10 are not lined and, of course, there are no gear doors.
Title: Re: Grand Rapids trip
Post by: John Ousterhout on January 27, 2014, 06:06:43 PM
Thanks, that's what I expected to hear.
The object appears to have encountered something else during it's life, beyond a simple hydraulic blow. There appears to me to be a large witness mark across it's narrow dimension near the "bottom" end as viewed in the picture.  The deformation appears to me to have been caused by impact with a generally curved surface.  The aluminum is bellied-out above the witness mark on the right, and bellied-out below the witness mark on the left.  There is also what appears to be a second impact mark above the primary one on the right, and angled from it, as though the piece encountered the same impactor a second time at a different angle.  This make it look a bit "funnel" shaped at the bottom end.
Am I just seeing things, or are these clues to the dynamic event that failed this piece of metal?
Title: Re: Grand Rapids trip
Post by: Jeff Victor Hayden on January 27, 2014, 06:24:58 PM
A link to aircraft rivets/fasteners and their use in repairs to aircraft structures and skin to maintain integrity and strength.

http://aviation.spenner.org/AircraftRivetsandSpecialFastners.pdf (http://aviation.spenner.org/AircraftRivetsandSpecialFastners.pdf)



Title: Re: Grand Rapids trip
Post by: Dave McDaniel on January 27, 2014, 10:55:59 PM
My guess is that it was more than just one hydraulic event that caused the delamination of the artifact piece (2-2-V-1 Sheet). The repeated cyclic torsional stress (twisting) applied to the airframe by wave action most likely caused a failure of the structural panel it was attached to. This might account for some of the plastic deformation of the artifact piece that was discussed in the NTSB report. Oil canning of the structural panel, and its movement under load, would be more than enough over a relatively short period of time to cause failure of the rivets holding 2-2-V-1 in place. Having one landing gear fixed in place (stuck in reef) would certainly aggravate the torsional forces applied to the airframe by wave action. In concert with this, the tension and compression forces acting on various parts of the airframe due to the lifting effect of the waves acting under (and maybe over) the wings, and more particularly the empennage. Due to its position relative to the reef it was most likely the part of the airframe that was subjected to most movement due to its surface area, configuration, light weight and long arm/moment. And then there was that one last wave. It's a wonder that the airframe held together as long as it did. Just my 2cents worth. They'll get it figured out!

LTM,
Dave
Title: Re: Grand Rapids trip
Post by: Tim Collins on January 28, 2014, 05:47:40 AM
The rivets did not pull through.  The rivets apparently fractured at the base of the head.  The force of the water on the interior surface of the skin literally blew the heads off the rivets.  There is one surviving rivet that pulled through the stringer because it was improperly bucked.

Has this been tested in any way - that so many rivets could have their heads blown off all at once with seemingly little or no external evidence of stress?
Title: Re: Grand Rapids trip
Post by: JNev on January 28, 2014, 06:40:41 AM
I happen to have my own notion of that possibilty (merely a different area of the same airplane) as many have seen I'm sure.

I'm certainly open to other suggestions.  The tricky thing is finding a span of .032 skin that long (24 inches) with no crossing line of rivets.

Anything is possible - including any number of source locations on the Electra, of course.  But what you've pointed out, actually seeing the artifact in person and the Harney drawings are all what got me looking at the lavatory window covering that was installed as a field effort in Miami. 

That window was very large - at least 24 inches in fact fore-aft (from just aft of Station 293 5/8 to roughly Station 320 - a bit over).  As evidenced in the pictures of the window in its open condition, there was no intermediate bracing - the outer frame was substantial.  To cover that would not require crossing rows / intermediate bracing (across the rows we see).  But some form of bracing to offset oil-canning / timpanic effect would be advisable, hence the rows of small rivets, IMO, as a possibility.

Prior to seeing Harney's drawings at the symposium in June 2012 I had not realized that this window had been cut into the Electra, then covered over later as decided unnecessary by Earhart and Noonan, apparently.  It would not take much in the way of 'structure' to effect such a cover - just light guage metal, as we see (which also happens to be consistent with skins aft of Station 293 5/8 I'm told).  The use of 3/32" rivets for light stiffening would be ideal, especially if the owner was fretting over weight concerns; there would be no primary structural challenge - the outer frame for the previously installed window would continue to bear those loads quite effectively.

See pictures here of the window prior to covering, then covered as done prior to departing Miami.  Finally, I've illustrated the conjectured use of light stiffeners spanning the panel fore-to-aft, which would reasonably fit what we see - light (3/32") rivets in slightly irregular rows, as if hand-drilled in field as after-thought or perhaps just an improvised / expedited effort to stiffen the rather large tempanic covering. 

This is all just an idea of course, but it made a lot of sense to me as a possible source for such a large, light-guage panel with evidence of light stiffening having been attached in the past (my read of the rows of 3/32" rivets). 

One other aspect of the cover being in this area is that it might be particularly vulnerable to any explosive force (water?) that was trying to escape the cabin / lav / tail area of the bird.  The large surface area covering a fairly large compartment with little baffle effect to stifle the force could leave the cover easy prey to overt force like that; it could be largely knocked out, and any remaining fasteners / seams then subject to rapid fatigue as the panel might shift to and fro with nature's forces (or someone salvaging an opportune piece of metal).  That may fit what you've described as forceful removal of this item from the craft.  A belly skin might be problematic in that way, considering that the flooring might serve as a baffle against the offending forces, just a thought.

Is there more information on the window covering effort that was done in Miami?  That might be an additional area of study to see what can be learned.  It is entirely possible that the photos are the only evidence we have - as a minor alteration done in haste, it is possible that no record was made of this effort.  But, with the artifact in-hand, that area of an existing Electra might be studied for similarity to rivet patterns along the edges - realzing Earhart's was altered with a substantial window frame, of course.  But maybe there is some additional information somewhere on that mod as well. 

In my mind, the lav window covering could be a real link to this mysterious large, thin piece of metal - that sort of thing would not turn up too many places, certainly not as a sister member in primary structure IMO.
Title: Re: Grand Rapids trip
Post by: Albert Durrell on January 28, 2014, 07:25:01 AM
Could this part have come off the plane as part of a bigger piece, then have the rivets removed by human hands so as to not have any damage to the skin?
Title: Re: Grand Rapids trip
Post by: John Ousterhout on January 28, 2014, 07:38:54 AM
Jeff - your "L10E Lav Window..." photo includes an excellent view of the antenna lead pass-through (likely a white ceramic insulator) and connection point to the Ventral V antenna.
Albert - anything is possible, but it is unlikely that hand-removal of individual rivets would leave the deformation seen in the artifact.  The sheet metal is ballooned-out a little bit between the lines of rivets, and each rivet location has a small dimple where the rivet heads resisted the force that  caused them to fail, essentially in a single event rather like a zipper unzipping.  If each had been drilled out or sheared off, there would be no reason for the dimpled deformation.  If each had been chiseled off, there would likely be tool marks and no similar deformation.  If a person had intentionally removed the rivets, so as to obtain a workable piece of sheet metal for a project, why leave one rivet that appears to have been improperly upset during assembly?  The removal process did damage the skin.
Something implied by the deformation is that the structure the sheet was riveted to was quite strong (0.060 is pretty thick, implying a structural shape, such as stringers (http://tighar.org/wiki/File:NEAM_04.JPG)) and obviously supported by some additional structure that resisted the pressure applied to the large area of the sheet (like a window frame or other substantial structure).  The necessary pressure to fail the rivets could be calculated, and the resulting force resisted by the underlying structure would likewise be estimated, giving a rough idea of the sizes of structural elements (and a hand full of additional assumptions).
Title: Re: Grand Rapids trip
Post by: Tim Collins on January 28, 2014, 08:39:43 AM
...and each rivet location has a small dimple where the rivet heads resisted the force that  caused them to fail, essentially in a single event rather like a zipper unzipping.  If each had been drilled out or sheared off, there would be no reason for the dimpled deformation.  ...

Before making that conclusion spend a few moments with the link that Jeff gave above, in particular p.p. 19ff:

A link to aircraft rivets/fasteners and their use in repairs to aircraft structures and skin to maintain integrity and strength.

http://aviation.spenner.org/AircraftRivetsandSpecialFastners.pdf (http://aviation.spenner.org/AircraftRivetsandSpecialFastners.pdf)
Title: Re: Grand Rapids trip
Post by: JNev on January 28, 2014, 10:33:52 AM
...and each rivet location has a small dimple where the rivet heads resisted the force that  caused them to fail, essentially in a single event rather like a zipper unzipping.  If each had been drilled out or sheared off, there would be no reason for the dimpled deformation.  ...

Before making that conclusion spend a few moments with the link that Jeff gave above, in particular p.p. 19ff:

A link to aircraft rivets/fasteners and their use in repairs to aircraft structures and skin to maintain integrity and strength.

http://aviation.spenner.org/AircraftRivetsandSpecialFastners.pdf (http://aviation.spenner.org/AircraftRivetsandSpecialFastners.pdf)

It is tempting to simplify the failure mode (or removal mode) of whatever was attached via the small rivets, but in fact that could have been a separate event from the intial web failure / separation from the mother structure.  Note I didn't say "was", but could have been separate events.

The panel as a whole (with intermediate light bracing) could have been 'blown off', i.e. mechanically or hydraulically expressed from the parent structure in some manner so as to leave the bulging effect, etc. that is observed; were simple, light stringers still attached, a secondary action could have removed those - deliberately or not.  Or, the 'skin' could have blown away in some fashion from ALL attachments - provided the underlying bracing was more substantially attached to the parent structure than to the skin.  I have doubts about the latter, mainly because intuition suggests to me (OPINION, CONJECTURE) that the 'underlying' attachments were very possibly very light structure.  My bias rests on the size of the rivets, and the slightly irregular alignment of the holes suggesting a somewhat impromptu arrangement.  I could be wrong - the skin could have been fully attached to heavier stringers in some way yet.

Point being that while the more defined the failure mode might be made and thereby more telling of the possibilities, what really matters is that we appreciate how much this panel might tell us, especially as to what 'mother ship' this item came from. 
- Are we looking at something that experienced an initial, partial separation due to brutal natural forces, e.g. crashing surf against an open structure that was pinned against a reef, and then failed and fully separated due to subsequent cyclic fatigue?  Or -
- Are we looking at something that was manually removed by man's hand from a wreck? 
- What were the opportunities for each of those events (where was the bird and when)?

The artifact was found in the village at Niku - does that mean it was originally harvested there on the island?  I'd like to think so, but a sniff test must include where else might Gardner Islanders might have gotten their hands on pre-war dural and perhaps imported it, if they were given to such as that sort of activity?  At face value it is easy to suppose they must have found it there - especially coupled with anecdotal material regarding an old wreck.

Then we have other odd pieces that TIGHAR has been able to rule out, I believe, such as the navigator's bookcase (http://tighar.org/wiki/2-1#A_TIGHAR_Campfire_Tale).  So we have some evidence, I believe, of some imported stuff.  It leaves us with a challenge - but finding a pre-war piece such as this artifact on that island does make for a pretty hot trail marker IMO.
Title: Re: Grand Rapids trip
Post by: Walter Runck on January 28, 2014, 12:00:57 PM
I'm having a hard time accepting the theory that the rivet heads were blown off without putting a lot of "belly" in the material between the rivet lines, so I went back to the original reports and started modeling the skin, rivets and possible stiffeners.  I'm not sure how far I'll go with this, but it helps me to sort through my ideas and the others posted here.  I have a couple of questions and comments for the Forum.

1.  It looks like there is a typo in the original FAA report (http://tighar.org/Projects/Earhart/Archives/Documents/NTSB_Report/ntsbreport.html) regarding the hole/rivet sizes.  The small holes are for 3/32 diameter rivets, not 3/16 as stated in the second sentence of the paragraph describing 2-2-V-1.  This allows the top row of 5/32" holes to be the "big" ones.

2.  The FAA analysis of the surviving rivet claims an indicated thickness of the member it was attached to of .060 inches, roughly 1/16".  This is just twice the nominal thickness of the skin itself.  I'm not an airframe mechanic, so I'm wondering what the likely shape and size of the siffener would be?  How would it have been attached to the existing airframe?

3. I like Jeff's idea about 2-2-V-1 coming from the window skin.  If we wanted to recreate the modification electronically, do we know how the original window and surrounding structure was configured?  Could some of our resident aviation tinknockers offer thoughts on how the job is likely to have been done in Miami?

4.  Would the covering over of the window have required FAA approval?  I'm guessing so, but I haven't seen anything here regarding a Miami FAA records search.

Now it's time to go watch snow in the Deep South.  Always worth the price of admission.
Title: Re: Grand Rapids trip
Post by: Tim Collins on January 28, 2014, 01:46:29 PM
- for an aircraft "skin" to have flush mounted rivets, that skin would need to be dimpled to begin with wouldn't it? See the above link re: rivets.
 
- to remove said "skin" from stiffeners to which it is mounted wouldn't the butt end of the rivet need to be removed/chiseled off?  In which case tool marks would be on the [missing] stiffeners not the skin wouldn't they?  Otherwise the external side would show evidence of forceful removal or resistance.

I just can't see how the rivets could all pop off without leaving signs of force to the holes, beyond mere dimpling, than observable (at least as I can see) on the item. Unless of course the rivets were made of something ridiculously soft.  Has anyone done any experiments on similar materials?   

I am of the opinion that suggesting that all the rivets just popped of as a result of some focused force, be it water or air, is akin to pulling a table cloth off a table set with fine china and crystal and expecting nothing to move. 
Title: Re: Grand Rapids trip
Post by: Chuck Lynch on January 28, 2014, 02:19:48 PM
In addition to any common rivet pattern alignments, could there be any photographic similarities between the artifact and the 1937 image? Maybe bends or shadows that appear in both photos?  The window "patch" in the photo seems to look less flat and less contoured than the rest of the plane's skin. And if it is a window "patch," then possibly it was not fastened as secure as the original airplane structure, allowing it to be blown off or removed easier..

Just a thought.
Title: Re: Grand Rapids trip
Post by: John Ousterhout on January 28, 2014, 05:24:45 PM
I think I can answer a couple of the points presented above, but not all:
For Tim - the rivets weren't flush, they had shallow domed heads, that wouldn't cause much drag in designs of the era. The heads of the installed rivets looked rather like the heads of modern-day thumbtacks, but smaller - a low rounded profile with a wide contact area. There was no dimple or countersink involved in the process.  The rivets were made of soft aluminum.  3/32" is the shank diameter, which is quite small.
For Walter - the underlying structural shape might have been in the shape of an "L" or "Z", with 90-degree bends, perhaps only 1/2 inch tall, although I've seen them more commonly about an inch tall. Using material twice as thick as the skin is about right for most stiffeners - the skin provides stiffness at a right angle to the stiffness of the structure, but the combination is still flexible across the structure (the 3rd angle),which would be consistent with a non-load-bearing piece that spanned a relatively narrow space.  The small diameter (3/32") also indicates non-load-bearing use.
The Van's Aircraft Site (http://www.rv7-factory.com/?cat=11) has lots of very nice photos and descriptions of modern riveting.  Note that they use lots of flush rivets and "pop" rivets, not the domed rivets used on the artifact.
Attaching the stiffeners to surrounding structure could have been done in a variety of ways.  I think Ric or others might be able to offer insight into the methods used in the 1930's.  Otherwise there are a variety of examples to be seen in the Van's aircraft photos.
Jeff's conjectures and caveats are appropriate and well put.  We don't know the sequence of events that resulted in this artifact becoming separated from its aircraft.  I understood that it wasn't found "in the village", but "near the village" on the beach (quotes mine).  It hadn't been seen the previous expedition that looked quite thoroughly in that area, and there were clear indications of wave damage to village structures, leading to the idea that it got washed up there in the recent past.  From where?  An intriguing question.
Also for Tim - the "dimpling" I mentioned was described in the NTSB report (http://tighar.org/Projects/Earhart/Archives/Documents/NTSB_Report/ntsbreport.html):"The skin around these holes was, in general, dimpled inward toward the concave side of the sheet suggesting that the sheet had been area loaded from the concave side while the rivets and underlying structure were intact."
More later...
(added later: the photos (http://tighar.org/wiki/File:NEAM_04.JPG) of another Lockheed show that the common stringer shapes were C-shape channels]
Title: Re: Grand Rapids trip
Post by: Ted G Campbell on January 28, 2014, 07:19:19 PM
Jeff Neville,
Do you have any diagrams/pictures that you can share with the forum on how we rivet two sheets of aluminum together?

For example, on a flush rivet we have to countersink the hole before the rivet is put into place and then bucked.  Whereas a brazier head rivet is put into an uncountersunked hole and then bucked into place.
 
When you remove a flush riveted piece of skin there are the countersink marks left behind but when you remove a piece of brazier head riveted skin there is not a noticeable indentation on the skin of the panel – maybe a little depression, which is dependent on the force of the bucking process.

I am thinking that basis the pictures of 2-2-V-1 that I have seen it is suggested there was some type of explosion that caused the panel to come lose i.e. was there a battery in the area were we suspect the panel was installed e.g. subject a lead acid battery to submersion in sea water and what do you get?

I agree with you Jeff, there was something there that caused them (AE/FN) to block out the lavatory window, what could it have been?  Is this where the panel came from I don’t know.

Ted Campbell
Title: Re: Grand Rapids trip
Post by: Walter Runck on January 28, 2014, 07:31:49 PM
- for an aircraft "skin" to have flush mounted rivets, that skin would need to be dimpled to begin with wouldn't it? See the above link re: rivets.
   

Kind of.  To have the head of the rivet end up flush with the skin, you have to use a countersunk style of rivet and either drill or dimple the skin before you set the rivet.  There are some drawings here (http://www.vansaircraft.com/public/Specs.htm), but not a lot of detail on installation technique.  I'm not aware of any use of this style on the Electra.  It's more expensive and only makes sense if you're more interested in performance than cost.

.
For Walter - the underlying structural shape might have been in the shape of an "L" or "Z", with 90-degree bends, perhaps only 1/2 inch tall, although I've seen them more commonly about an inch tall. Using material twice as thick as the skin is about right for most stiffeners - the skin provides stiffness at a right angle to the stiffness of the structure, but the combination is still flexible across the structure (the 3rd angle),which would be consistent with a non-load-bearing piece that spanned a relatively narrow space.  The small diameter (3/32") also indicates non-load-bearing use.
The Van's Aircraft Site (http://www.rv7-factory.com/?cat=11) has lots of very nice photos and descriptions of modern riveting.  Note that they use lots of flush rivets and "pop" rivets, not the domed rivets used on the artifact.
Attaching the stiffeners to surrounding structure could have been done in a variety of ways.  I think Ric or others might be able to offer insight into the methods used in the 1930's.  Otherwise there are a variety of examples to be seen in the Van's aircraft photos.
Also for Tim - the "dimpling" I mentioned was described in the NTSB report (http://tighar.org/Projects/Earhart/Archives/Documents/NTSB_Report/ntsbreport.html):"The skin around these holes was, in general, dimpled inward toward the concave side of the sheet suggesting that the sheet had been area loaded from the concave side while the rivets and underlying structure were intact."
More later...

Thanks John, I get the sense that the FAA is implying that the dimpling came during whatever event caused them to separate from the sheet, rather than during installation.  I'll do a sketch to show what I mean when I get back to the office.


I just can't see how the rivets could all pop off without leaving signs of force to the holes, beyond mere dimpling, than observable (at least as I can see) on the item. Unless of course the rivets were made of something ridiculously soft.  Has anyone done any experiments on similar materials?   


It's the worst explanation for what we're looking at, with the exception of everything else.  There are rivets made of 1100 series aluminum that are much softer, but the FAA claims there is a dimple on the surviving rivet which should indicate a much stronger 2117 T4 material.  This could be settled by chemical or metallographic analysis if desired.
Title: Re: Grand Rapids trip
Post by: Jon Romig on January 28, 2014, 07:59:18 PM
A link to aircraft rivets/fasteners and their use in repairs to aircraft structures and skin to maintain integrity and strength.

http://aviation.spenner.org/AircraftRivetsandSpecialFastners.pdf (http://aviation.spenner.org/AircraftRivetsandSpecialFastners.pdf)

I am interested in understanding what level of force would accomplish this.

The linked document suggests that the reference 3/32 rivets will fail in "sheer" at a force of 200-300 pounds. It is unlikely that these alloy rivets are the same strength as the "soft aluminum" rivets that may have been used in the 1930s, in fact they are very likely to be stronger.

But assuming 200 pounds to failure for each, simultaneous failure of all the rivets would have required 83 (my rough count of rivet holes) x 200 pounds = a force of 16,600 pounds, spread over about 437 square inches, or 38 PSI.

Bernoulli's equation: P = 0.5 * rho * v^2 where rho is density of water at 1000 kg/m^3 (metric units)

38 PSI = 261 kPa

Solving: V = 47 MPH

That is a pretty fast-moving wave, even assuming some hydraulic focussing, which would likely be minor considering the geometry of the fuselage.

It makes me wonder if the artifact popped loose in a crash into the sea, not in wave action. Or in the fuel explosion discussed in the report.

Could somebody please check my work?

Thanks!

Jon
Title: Re: Grand Rapids trip
Post by: John Ousterhout on January 28, 2014, 10:28:19 PM
Jon - Bernoulli would apply if the pressure were a difference being created by high velocity flow on one side of the panel and none on the other.  I think the more likely event was impact(s) by waves, which would abruptly pressurize one side of the panel due to a change in momentum.

Start with a quantity of water moving at normal wave velocity encountering the panel - tons of mass x some velocity, that is forced to a halt or change direction in a short distance.  If there is no room for the mass of water to splash sideways then it acts like a hammer, and more of the mass is brought to a halt which increases the hydraulic pressure on the panel momentarily.

A quick google search didn't provide me with more useful calculations, and I'm 600 miles from my reference books at present, so I hope this arm-waving explanation helps.
Title: Re: Grand Rapids trip
Post by: Walter Runck on January 28, 2014, 11:30:53 PM
With apologies to Jon and Cool Hand Luke, what we have here is failure to orientate.  We're dealing with tensile loads, not shear.

Imagine a rivet looking kind of like a muffin with a top and a stump (http://en.wikipedia.org/wiki/The_Muffin_Tops). 

The published numbers for shear strength are based on loading a rivet in the manner they were intended to be loaded - sideways.  It's the amount of force necessary to knock the muffin top off of the stump by pulling sideways on the top while holding the stump in your hand.

The type of failure we're suspecting here is tensile rather than shear.  Pulling the muffin top off of the stump by prying it up out of the baking pan after we forgot to put the little paper thing in to keep the batter from baking itself into the pan.  Rivets as used in stressed skin construction aren't intended to carry a lot of load in this direction.  If you know something is going to be carrying a longitudinal load like a pulley in a control cable, you don't attach the pulley to the bulkhead with rivets, you use machine screws (bolts).

Other than that, Jon's exercise is similar to what I'm pursuing.  Figure out the tensile load necessary to pop the head off of one rivet.  Figure out how much skin each rivet would be holding in place (by dividing total area by number of rivets).  Don't forget to account for the area shielded by the stiffeners (this is problematic if you don't know what the stiffeners were).  Figure out what kind of pressure loads your presumed cause of failure (hydraulic, explosive, coconut crabs, etc.) placed on the inside and outside of the structure.  Pressure times area equals force.  Once you have the amount of force per rivet, compare it to the tensile yield load and see whether your structure is still in one piece or not.

I've attached a stress distribution diagram of how a tensile load resulting from pressure on the skin would resolve itself within the rivet body.  The red areas indicate the highest stresses and location of probable failure.  If you glue the muffin stump to the counter and lift up on the bottom lip of the top, it will eventually separate right at the junction of stump and top.  This is simulated by fixing the end of the shaft and applying a uniform pressure to the underside of the head. 
Title: Re: Grand Rapids trip
Post by: Tim Gard on January 29, 2014, 01:41:26 AM
There is evidence of intense wave action at Nikumaroro.

As Ric explains in "Aerial Tour of Nikumaroro", sections of reef the size of bulldozers were broken off and flung around like so many basket balls. Sections of steel hull have been frisbeed.

http://www.youtube.com/watch?v=DL9FGsvB3E8
Title: Re: Grand Rapids trip
Post by: Jon Romig on January 29, 2014, 07:01:01 AM
With apologies to Jon and Cool Hand Luke, what we have here is failure to orientate.  We're dealing with tensile loads, not shear.
Walter, thanks. I agree we are looking at tensile failure, not sheer. I could not find any data on tensile load capacity, so I used sheer as a surrogate. I did NOT know that rivets are much stronger in sheer, but it makes sense once you think about it. I assume we can do a failure calc based upon known characteristics of the material (soft aluminum or an alloy).

John: I was motivated to use Bernoulli based upon some sources on the web that were calculating the pressure (in PSI) of a "jet" of water based on a known velocity. The weight or amount of the water (in our problem the size of the wave) was considered irrelevant in this calculation as the force is considered instantaneous. The jet must be absolutely normal to the surface being measured, or the pressure will be less (or the velocity must be higher). Believe me, I am no hydraulic engineer so that may be all wrong ;-]

Tim: I agree that there is intense wave action on Niku, and that water in one of these waves could very well have been moving at 47 MPH. I have tried to research water velocities within waves of various sizes, but cannot find a source.

It is worth noting that a wave pressure of 38 PSI, or even less, adds up quickly (for example 16,000 pounds on our <3 SF artifact) so I am not at all surprised that large heavy objects get tossed around.

Jon
Title: Re: Grand Rapids trip
Post by: John Ousterhout on January 29, 2014, 07:10:35 AM
A 1944 NACA report  (http://naca.central.cranfield.ac.uk/reports/1944/naca-tn-930.pdf)gives tensile failure numbers for AN456 3/32 inch Brazier head rivets in a variety of sheet thicknesses, and describes the heads failing at around 200 pounds force.
Note that that works out to Jon's 37psi to fail the rivets in tension, given that each rivet supported about 5.3 square inches.
If you applied a bit more than 37 psi to the whole sheet at once (as if a wave smacked into it), then there will be one rivet somewhere to fail first, which increases the load on the neighboring rivets, so they fail, and away we go...
Title: Re: Grand Rapids trip
Post by: John Ousterhout on January 29, 2014, 07:19:32 AM
The 2-2-V page  (http://tighar.org/wiki/2-2-V-1) has some nice photos showing the C-shapes (sometimes called "channel" or "U" shaped, but I don't know what they were called back then) of structural stringers in the fuselage, clearly showing the rivets from the interior and exterior. Some of the photos show how the stringers were connected to other structural elements.  It's hard to imagine the connections between the stringers and the main structure being capable of resisting an impact load without coming loose.  The "bellying" of the aluminum and dimpling around the rivet heads may well have been all that happened while the assembly tore loose from the aircraft, and only later were the stringers removed from the skin by removing the rivets (as proposed above by Walter, Jon and probably some others I've overlooked).
Title: Re: Grand Rapids trip
Post by: Walter Runck on January 29, 2014, 09:32:27 AM
A 1944 NACA report  (http://naca.central.cranfield.ac.uk/reports/1944/naca-tn-930.pdf)gives tensile failure numbers for AN456 3/32 inch Brazier head rivets in a variety of sheet thicknesses, and describes the heads failing at around 200 pounds force.
Note that that works out to Jon's 37psi to fail the rivets in tension, given that each rivet supported about 5.3 square inches.
If you applied a bit more than 37 psi to the whole sheet at once (as if a wave smacked into it), then there will be one rivet somewhere to fail first, which increases the load on the neighboring rivets, so they fail, and away we go...

Nice find John.  Kind of funny to see that a report about popping the heads off rivets was classified during WWII.

We still need to account for interior surface area covered by the stringers.  Commercial sizes for 1/16 thick aluminum channel (http://www.factorysteel.com/aluminum-angles-bars-channels-pipe.htm#channels) seem to range from 3/8 to 3/4" wide , so you have to debit the overall surface area by something around 12% (assuming 1/2 wide channel on 4 inch centers) and rerun the pressure calculations.

Personally I think modeling the dynamic effects of crashing waves or exploding batteries is a step or two beyond the current state of this investigation.  There are too many unknowns to develop any knowledge with a reasonable level of confidence.  Without knowing the structure behind the skin or even where the skin was located, we can't even do a decent static analysis (if you filled the Electra up with water, would the window blow out?), let alone a dynamic one.  It's a good mental exercise to work through the process, but don't expect any conclusions.
Title: Re: Grand Rapids trip
Post by: John Ousterhout on January 29, 2014, 10:50:30 AM
Walter sez: "...It's a good mental exercise to work through the process, but don't expect any conclusions."
Well put.  The same general statement applies to a lot of TIGHAR's work.
Not only don't we know much about what happened, we also don't know what we don't know, so to speak.
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on January 29, 2014, 12:30:04 PM
It's the worst explanation for what we're looking at, with the exception of everything else.  There are rivets made of 1100 series aluminum that are much softer, but the FAA claims there is a dimple on the surviving rivet which should indicate a much stronger 2117 T4 material.  This could be settled by chemical or metallographic analysis if desired.

The surviving rivet is an AN455 or AN456 3/32 inch Brazier head made of 2117 T4 aluminum.  That was confirmed long ago by the NTSB lab.

Also, please note, Aris Scarla works for the FAA but his observations and opinions regarding this artifact are offered as an individual, not as a representative of the FAA.  So let's not say "the FAA says."
Title: Re: Grand Rapids trip
Post by: Greg Daspit on January 29, 2014, 12:35:11 PM
Assume a plane part is stuck in a groove at the steep edge of the reef like has been speculated. There is a storm.  Between the waves the plane may be exposed. (The water level of the wave below sea level about the same as the wave height above sea level) Then a fresh wave comes in. What happens to the water pressure of the next incomming wave in the groove?
And what happens to the velocity?
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on January 29, 2014, 12:58:26 PM
Aris Scarla, Bob Brandenburg and I are designing an experiment to confirm how much and what kind of force is needed to cause the damage we see on the artifact.  Aris can build a reproduction of the belly of the Electra in the area where we think the failure occurred. The same aluminum sheet and stringers are commonly available today but finding the old-style brazier head rivets might be tricky.  Bob can calculate the required force.  We'll need to partner with a university or research facility that has the capability to generate the kind of fluid force we need.

Knowing what it takes to cause this kind of damage will tell us a great deal about what circumstances the aircraft the artifact came from must have experienced. That, in turn, should enable us to refine our hypothesis of what happened to NR16020 and how much of it is likely to be left to find.

Title: Re: Grand Rapids trip
Post by: Walter Runck on January 29, 2014, 01:04:41 PM
It's the worst explanation for what we're looking at, with the exception of everything else.  There are rivets made of 1100 series aluminum that are much softer, but the FAA claims there is a dimple on the surviving rivet which should indicate a much stronger 2117 T4 material.  This could be settled by chemical or metallographic analysis if desired.

The surviving rivet is an AN455 or AN456 3/32 inch Brazier head made of 2117 T4 aluminum.  That was confirmed long ago by the NTSB lab.

Also, please note, Aris Scarla works for the FAA but his observations and opinions regarding this artifact are offered as an individual, not as a representative of the FAA.  So let's not say "the FAA says."

My mistake.  I conflated the NTSB and the FAA.  The NTSB report does contain the rivet ID I was thinking of, so that would seem to be pretty official.  As far as the FAA goes, I'm grateful that people with expertise in this area are willing to donate their time and energy to the project. 

I am curious if the FAA has released any engineering analysis regarding the effects of internal explosions on stressed skin.  I'm sure they've done the work, but could understand it not being publicly available.

Once you have the solid models, it's not a huge amount of extra work to do the stress analysis if you have the software.  Plus it's a good clean fun way to stay in practice.
Title: Re: Grand Rapids trip
Post by: Ted G Campbell on January 29, 2014, 01:24:35 PM
The FAA and the NTSB did a lot of work on explosions re the TWA 800 incident and I would think they may have some data they could share concerning effects on aircraft skins.
Ted Campbell
Title: Re: Grand Rapids trip
Post by: Tim Collins on January 29, 2014, 05:24:42 PM
For Tim - the rivets weren't flush, they had shallow domed heads, that wouldn't cause much drag in designs of the era. The heads of the installed rivets looked rather like the heads of modern-day thumbtacks, but smaller - a low rounded profile with a wide contact area. There was no dimple or countersink involved in the process.  The rivets were made of soft aluminum.  3/32" is the shank diameter, which is quite small.

I defer to your knowledge on the subject. I was clearly wrong about flush mounted rivets. However, looking for pictures of the Electra that have good views of the riveting I came across this: http://explorerworld.hu/wp-content/uploads/2012/08/earhart-cockpit-1024x817.jpg (http://explorerworld.hu/wp-content/uploads/2012/08/earhart-cockpit-1024x817.jpg). Sure seems like there's a lot of dimpling going on with those rivets. Granted not all of them, but certainly more than just a few.
Title: Re: Grand Rapids trip
Post by: richie conroy on January 29, 2014, 08:02:03 PM
Hi All

Just thinking aloud here, Is it possible this artifact is a result of the landing on the reef giving it's location seem's to fit with hypothesis of landing ?

If say the artifact is a part of a bigger piece that would explain why so little damage to rivet holes 2 things can happen either the rivet head thinness can buckle or due to rivets having the hole in middle they can sort of implode at certain pressure, Bare in mind temperature in cabin at touch down and temperature on outside

sort of makes sense to me like ? 
Title: Re: Grand Rapids trip
Post by: Jeff Victor Hayden on January 29, 2014, 08:40:39 PM
Something that might have contributed to the rivet heads shearing off? The amount of tensile force needed would be significantly reduced under these circumstances...

"Ferrous metals placed in contact with moist salt air will rust if not properly protected. Nonferrous metals, those without an iron base, do not rust, but a similar process known as corrosion takes place. The salt in moist air (found in the coastal areas) attacks the aluminum alloys. It is a common experience to inspect the rivets of an aircraft which has been operated near salt water and find them badly corroded.
If a copper rivet is inserted into an aluminum alloy structure, two dissimilar metals are brought in contact with each other. Remember, all metals possess a small electrical potential. Dissimilar metals in contact with each other in the presence of moisture cause an electrical current to flow between them and chemical byproducts to be formed. Principally, this results in the deterioration of one of the metals.
Certain aluminum alloys react to each other and, therefore, must be thought of as dissimilar metals. The commonly used aluminum alloys may be divided into the two groups shown in figure 6-32.

Aluminium groupings

Group A       Group B

1100            2117
3003            2017
5052            2124
6053            7075

figure 6-32

Members within either group A or group B can be considered as similar to each other and will not react to others within the same group. A corroding action will take place, however, if any metal of group A comes in contact with a metal in group B in the presence of moisture.
Avoid the use of dissimilar metals whenever possible. Their incompatibility is a factor which was considered when the AN Standards were adopted. To comply with AN Standards, the manufacturers must put a protective surface coating on the rivets. This may be zinc chromate, metal spray, or an anodized finish."

Now Ric's rivet is a AN455 or AN456 3/32 inch Brazier head made of 2117 T4 aluminium, Group B.
The skin is a sheet of 0.032 Alclad which is a 2024 alloy? Group A doesn't include 2024 aluminium but, on checking the aluminium alloy composition limits (% weight) table it is of remarkably similar composition to series 1100 and series 3003 aluminium alloys.

http://avstop.com/ac/apgeneral/rivets.html (http://avstop.com/ac/apgeneral/rivets.html)

The rivets may well have been weakened significantly by the environment the aircraft ended up in.
Title: Re: Grand Rapids trip
Post by: John Ousterhout on January 29, 2014, 10:57:06 PM
Tim - yes, that photo does clearly show a little dimpling around many of the rivet heads.  I've seen similar in other photos and also in other aircraft, especially when the rivet was driven with an airgun from the factory-head side, and supported with a buck on the back side.  When such rivets are drilled out, it is common in my experience to see an imprint of the head on the surface of the aluminum sheet, but the dimple doesn't abruptly start at the edge of the head - it's more of a subtle buckling between rivets as the slight excess material gets pushed up.  The amount of deformation seen in the artifact may be a difference in degree.
Having thought about it for a day, I am now of the opinion that the rivets likely survived the initial expulsion of the sheet from the surrounding structure, with the stringer intact.  I find it hard to believe the stringer would have been strong enough to remain connected to the aircraft structure, considering the apparent light-duty the panel seemed designed for.
Title: Re: Grand Rapids trip
Post by: Walter Runck on January 30, 2014, 08:55:36 AM
The 2-2-V page  (http://tighar.org/wiki/2-2-V-1) has some nice photos showing the C-shapes (sometimes called "channel" or "U" shaped, but I don't know what they were called back then) of structural stringers in the fuselage, clearly showing the rivets from the interior and exterior. Some of the photos show how the stringers were connected to other structural elements. 

It looks like some of the channels on the NEAM aircraft were formed by folding thinner stock over onto itself (http://tighar.org/wiki/File:NEAM_11.JPG).  Other than not having thicker material or preformed channel around, why would you do this?  It looks like a lot of work.  I'm guessing that the approximately .06 of phantom material behind the surviving rivet might have been two layers of .032?  Just can't figure out why.

I don't have an aircraft museum around here, so I'm stuck looking at pictures.  Any help or practical experience?

Title: Re: Grand Rapids trip
Post by: John Ousterhout on January 30, 2014, 09:06:26 AM
Walter - you've got sharp eyes. I hadn't noticed that before, but it looks to me to be a double-image rather than two layers of metal.  Cheap camera optics, such as from a cell phone, tend to create that sort of problem at the edges of the field of view.  Looking further to the right the visual effect is more pronounced and looks less like two layers and more like an even more distorted image.

If someone found the bulged assembly on the beach, they might cut off the rivet shanks flush with the stringer then punch out the rivet remnant, leaving no mark on the sheetmetal.  The one intact rivet was left because it wasn't well attached to the stringer and came out as one piece.  Perhaps the  person doing such work thought the channel was more valuable than the sheet at the time.  It's a curious piece of a puzzle.

Sometimes I feel as though TIGHAR were compiling one of the most thorough histories of a randomly picked island.
Title: Re: Grand Rapids trip
Post by: Walter Runck on January 30, 2014, 10:51:33 AM
I am trying to work up a cross section for likely stiffener shapes and haven't had much luck.  Without artifacts or drawings, my preference would be to measure some similar, original structure on an Electra, but they're kind of thin on the ground around here.
Title: Re: Grand Rapids trip
Post by: Jon Romig on January 30, 2014, 09:19:16 PM
Assume a plane part is stuck in a groove at the steep edge of the reef like has been speculated. There is a storm.  Between the waves the plane may be exposed. (The water level of the wave below sea level about the same as the wave height above sea level) Then a fresh wave comes in. What happens to the water pressure of the next incomming wave in the groove?
And what happens to the velocity?

I have found some good sources for speed of waves, but not much for the speed of water in a breaking wave.

A wave caused by a 92 MPH wind with a fetch of 1,633 miles (!) will be 49 feet high and will be traveling at (coincidentally) 49 FPS. I think this should be considered an extreme boundary condition. With little or no shallows at the edge of the reef, I don't think we have to consider the slowing and heightening that would be experienced by a wave approaching a normal shore that has a shoaling bottom. So our wave hits the Niku reef at its deep-ocean speed and height.

A "plunging" wave would have to be about 72 feet high to dump water on our artifact at our calculated 47 MPH, so I think we can discount the cresting of a wave as the source for this speed.  It is the horizontal speed of the wave that we have to consider.

Our giant 49' wave traveling horizontally at 49 FPS is moving at 33.4 MPH. Compare this to the 47 MPH minimum (not considering the protection provided by the stringers) required to pop all the rivets and you are not too far off. If this wave were further focused by one of the reef grooves it could achieve the 47 MPH, although a wave that big will feel the groove only on its underside, where its speed is considerably reduced, even negative.

A much smaller wave arriving at low tide could experience considerable focusing in a reef groove, but smaller waves travel much slower. For example, a much smaller but still decent-sized 14' wave is only traveling at about 20 MPH. The geometry of the groove becomes increasingly important as you consider the even smaller waves that would be well-focused by the reef groove.

My sense is that reef grooves do not widen a lot towards deeper water, but I may be wrong.

Jon
Title: Re: Grand Rapids trip
Post by: Jon Romig on January 30, 2014, 09:35:45 PM
....
"The salt in moist air (found in the coastal areas) attacks the aluminum alloys. It is a common experience to inspect the rivets of an aircraft which has been operated near salt water and find them badly corroded.
....
The rivets may well have been weakened significantly by the environment the aircraft ended up in.

Re dissimilar metals:
If the rivets were weakened by corrosion caused by the galvanic action between two dissimilar metals, then I would expect to also see corrosion on the skin that they were in contact with. Or does only one of the two dissimilar metals experience the corrosion?

Jon
Title: Re: Grand Rapids trip
Post by: Jon Romig on January 30, 2014, 10:01:22 PM
....
I find it hard to believe the stringer would have been strong enough to remain connected to the aircraft structure, considering the apparent light-duty the panel seemed designed for.
If the artifact were subject to 16,000 pounds of force that I calculated is necessary to pop out all the rivets, I too find it difficult to believe that light stringers remained attached to the frame of the Electra. Do we know from the thickness of the stringer material that these were in fact secondary framing members?

Jon
Title: Re: Grand Rapids trip
Post by: Tim Gard on January 31, 2014, 02:52:33 AM
The FAA and the NTSB did a lot of work on explosions re the TWA 800 incident and I would think they may have some data they could share concerning effects on aircraft skins.
Ted Campbell

Agreed, and it's spawned a great deal of concern about the potential involvement of missiles.

On another note, I can't help feeling that the forces that may have acted on the aircraft skin may have acted uniquely, as does directed explosive. See 43:00 at this video ...

http://www.youtube.com/watch?v=01pjt_K-94M

Title: Re: Grand Rapids trip
Post by: Monty Fowler on January 31, 2014, 08:26:47 AM
I'm going to nose around with my contacts and see who might have a good fluids lab that is looking for a really cool historical research project.

LTM,
Monty Fowler, TIGHAR No. 2189 CER
Title: Re: Grand Rapids trip
Post by: Todd Attebery on January 31, 2014, 12:30:14 PM
I mostly lurk in the forum during my lunch hour.  This topic does relate to my area of expertise as an aircraft structural engineer.

Rivets installed in thin sheet and loaded in tension will often fail by other mechanisms other than head failure... though that is the maximum possible value.    A modern universal head 2117 fastener will fail in tension in 0.032" sheet at approximately 175 lbs.  The same countersunk fastener will fail at about 90 lbs.  A brazier head would likely be somewhere in between those values and the fastener "pulling out" could account for the dimpled appearance.  Adjust your wave speed calculation accordingly.  I am NOT a fluids expert, but your calculations seem reasonable.

LTM 
Title: Re: Grand Rapids trip
Post by: Randy Conrad on January 31, 2014, 02:14:06 PM
This is a question for Ric, Richie, and Jeff.....Let's say your leaving New Guinea...things are going great....and something breaks from being pulled from the tail of the plane...such as an antenna cable. My question is in the vintage WWII days, and in this case the Electra...Can an aircraft continue flying if part of the skin or plane comes loose due to some form of damage?
Title: Re: Grand Rapids trip
Post by: Walter Runck on January 31, 2014, 02:50:31 PM
Can an aircraft continue flying if part of the skin or plane comes loose due to some form of damage?

 I'm gonna say yes (http://www.eaa.org/warbirdsbriefing/articles/1110_midair.asp).
Title: Re: Grand Rapids trip
Post by: Jerry Germann on January 31, 2014, 05:13:34 PM
I believe it was reported that Earhart hit a small ridge of dirt at the end of the runway at Lae ( leaving dust hanging in the air for sometime). Damage due to this????
Title: Re: Grand Rapids trip
Post by: Martin X. Moleski, SJ on January 31, 2014, 05:29:15 PM
I believe it was reported that Earhart hit a small ridge of dirt at the end of the runway at Lae ( leaving dust hanging in the air for sometime). Damage due to this? ???

The fact that "it was reported" does not mean that the report is reliable.

Ric Gillespie, "Forum Highlights": (http://tighar.org/Projects/Earhart/Archives/Forum/Highlights81_100/highlights99.html)

Subject: Earhart's takeoff from Lae
Date: 8/2/00

>What we saw in the TIGHAR film clip was Bertie Heath's description of
>Earhart's take-off related to Pellegreno in 1967. Pellegrino, page 144 ---

He sat quietly a moment. "I wanted to see them off, but couldn't just stop working. The rest of that day I flew back and forth to the mines. The following day when returning from my first trip, I saw her silver plane moving slowly down the unpaved runway. It must have been 3000 feet long at that time. When her plane reached the road that had a high crest and ran across the runway near the seaward end, it bounced into the air, went over the drop off and then flew so low over the water that the propellers were throwing spray." He paused and took a sip of beer. "Always have a couple of beers every day." "She continued straight out to sea for several miles before climbing on course slowly. That was the last I saw of her." He thought for a moment. "The wind was calm and the dust from where she hit the crown of that dirt road didn't disperse quickly, just sort of hung there." 

Neither the takeoff film nor aerial photos of the airfield taken during that period show a dirt road crossing the runway. The film clearly shows that the rather abrupt rotation of the aircraft was the result of the pilot's actions, not an impact with a perturbation in the runway surface. Smoke from a brush fire on the far side of the runway also shows that the wind was not calm, and the only dust raised during the takeoff run was the puff described in my earlier posting. It occurs not at the moment of rotation as Heath alleges, but several seconds earlier in the takeoff run. The accurate parts of Bertie's recollections 30 years after the fact can be summarized as:
Title: Re: Grand Rapids trip
Post by: Jon Romig on January 31, 2014, 06:59:11 PM
....
"The salt in moist air (found in the coastal areas) attacks the aluminum alloys. It is a common experience to inspect the rivets of an aircraft which has been operated near salt water and find them badly corroded.
....
The rivets may well have been weakened significantly by the environment the aircraft ended up in.

Re dissimilar metals:
If the rivets were weakened by corrosion caused by the galvanic action between two dissimilar metals, then I would expect to also see corrosion on the skin that they were in contact with. Or does only one of the two dissimilar metals experience the corrosion?

Jon

OK, OK, I did the research. Wikipedia says that in galvanic corrosion, the anodic metal will be corroded and the products of the corrosion will be deposited on the cathodic metal. So it seems that the artifact would show evidence of this process if it had occurred.

Conclusion: this type of corrosion did not occur to any great extent before the event that removed the rivets.

This is a nice piece of negative evidence that supports the primary narrative: given that we are pretty sure that these were dissimilar metals (the rivets and the skin), the artifact was not subject to extended exposure to the elements (including the necessary air) before the event that removed the rivets.

Jon
Title: Re: Grand Rapids trip
Post by: Jon Romig on January 31, 2014, 07:08:47 PM
Assume a plane part is stuck in a groove at the steep edge of the reef like has been speculated. There is a storm.  Between the waves the plane may be exposed. (The water level of the wave below sea level about the same as the wave height above sea level) Then a fresh wave comes in. What happens to the water pressure of the next incomming wave in the groove?
And what happens to the velocity?

A much smaller wave arriving at low tide could experience considerable focusing in a reef groove, but smaller waves travel much slower. For example, a much smaller but still decent-sized 14' wave is only traveling at about 20 MPH. The geometry of the groove becomes increasingly important as you consider the even smaller waves that would be well-focused by the reef groove.

My sense is that reef grooves do not widen a lot towards deeper water, but I may be wrong.

Jon

Ric, could you describe the approximate shape and size of the reef grooves, especially the parts visible only at low tide? Do we have any photos?

Thanks!

Jon
Title: Re: Grand Rapids trip
Post by: Jon Romig on January 31, 2014, 08:18:00 PM
Pressure

There have been occasional references to pressure (of water) in this thread. It is important to recognize that pressure (from the weight of the water column alone) is unlikely to have been the prime cause of the rivet failures. Consider:

Atmospheric pressure at sea level is 14.7 PSI.
The approximate pressure to cause the rivets to fail was 38 PSI minimum.
38 PSI is about 2.59 atmospheres.
Water pressure increases by 1 atmosphere for every 33' of depth. A water column tall enough to cause this pressure would be 85' high.

You could stand the Electra on its tail and fill it with water and never have near enough force to pop a panel off.

So we need to be looking at water in motion, unless we are modeling the event in a lab, where I believe that a static pressure experiment would be much safer than a 2' x 2' jet of water moving at 47 MPH....;-)

Jon
Title: Re: Grand Rapids trip
Post by: Jerry Germann on January 31, 2014, 09:01:48 PM
Regarding artifact 2-2-V-1....As per the Al-clad lettering stamped in ink....the artifacts physical description state that the letters AD remain, on the convex/ rivet head bearing side....that said, can we conclude that if this panel was installed on the under belly or fuselage window opening , that this lettering would be visible looking upon the exterior of the plane? In 1937 the Electra had a value of roughly $80,000 dollars during the depression ...all photos give the appearance of it being a highly polished vessel.Photos of earhart and others captured under the wings and underbelly show mirror like quality reflections . During the reconstruction of the Electra after the Luke field incident, I came across photos of personal being shown x-raying the structural portions of the plane. To me it appears that quality and value was put into it's repair. With all this said, I wonder as to why lockheed or anyone ..(Miami) would place a panel in such fashion? It is my opinion ( though others may not agree) that any such repairs would have been buffed to like quality.....would Putnam and Earhart insist on this considering the electra's value? I don't know that answer. If this panel were part of the Electra, what panel /panels left unbuffed at the factory could provide the source of this artifact ? 
Title: Re: Grand Rapids trip
Post by: Walter Runck on January 31, 2014, 10:35:50 PM
Pressure

There have been occasional references to pressure (of water) in this thread. It is important to recognize that pressure (from the weight of the water column alone) is unlikely to have been the prime cause of the rivet failures. Consider:

Atmospheric pressure at sea level is 14.7 PSI.
The approximate pressure to cause the rivets to fail was 38 PSI minimum.
38 PSI is about 2.59 atmospheres.
Water pressure increases by 1 atmosphere for every 33' of depth. A water column tall enough to cause this pressure would be 85' high.

You could stand the Electra on its tail and fill it with water and never have near enough force to pop a panel off.

So we need to be looking at water in motion, unless we are modeling the event in a lab, where I believe that a static pressure experiment would be much safer than a 2' x 2' jet of water moving at 47 MPH....;-)

Jon

You're correct Jon.  It doesn't matter how fast a stream of water is moving in air - it is at atmospheric pressure.  In fluid dynamics it's called free surface or open channel flow. 

It's easy to jumble the concepts of pressure and momentum when thinking about this stuff because it requires an external force to either balance (in the case of pressure) or change (in the case of momentum) the energy contained in the fluid.  The energy in an impacting wave that would blow out a window cover or other section of skin comes in the form of momentum, not pressure.  The reaction force is changing the momentum of the incoming stream by changing its direction.  It could be going as fast as ever, but if it is running parallel to the skin or some other surface, there is no net force on either the skin or the water.

While we're waiting for the lab work to come back, I found some flow modeling software that I'm going to play around with.  I'll post the results if I get anything that isn't obvious rubbish.
Title: Re: Grand Rapids trip
Post by: Bill de Creeft on February 01, 2014, 01:20:32 AM
Jon...not sure i understand what you are saying...but the skin and rivets are not dissimilar metals; they are both aluminum...for that reason!'
They become "dissimilar" when located near a steel structure, for instance, particularly in water.

Have seen stainless steel skins over aluminum skins (in this case installed at exhaust ports for on board gas heaters to protect the aluminum skins ) that completely corroded away the aluminum on a seaplane exposed to salt water in normal operations...
But any airplane submersed in seawater with lots of steel structure and aluminum skin is going to result in deterioration...in fact it is a source of constant care and maintenance in normal operations around saltwater.
Engine cylinder heads are aluminum and the cyl. barrels are steel, and underwater the heads disappear in time when submerged as in the case of the radial engines on the Electra.

As to the earlier question by someone about the effect of loose or separated skin from the plane, as in the loss of a panel...it entirely depends on the location....A lost panel on the belly could be no worse than opening a camera hatch ( or a Bomb Bay)... on the wing, it could result in loss of lift on that side; resulting in a roll-over.

My feeling is it would not be a cause of the accident if the plane landed successfully...but if identified as apiece of the plane, would help identify the plane, obviously...
And therein lies the value.
I think this has been previously discussed.

Bill
Title: Re: Grand Rapids trip
Post by: Tim Gard on February 01, 2014, 02:05:31 AM
It occurred to me that if water from an ebbing wave acted on one side of the skin, while water from a waxing wave acted on the other side of the skin the available forces might combine, doubling the available wave force .

Title: Re: Grand Rapids trip
Post by: Ric Gillespie on February 01, 2014, 07:29:31 AM
Regarding artifact 2-2-V-1....As per the Al-clad lettering stamped in ink....the artifacts physical description state that the letters AD remain, on the convex/ rivet head bearing side

To be clear, no ink remains on the aluminum.  What we see is the imprint of the letters etched onto the surface. Not sure why the etching occurred on only some of the letters.

 
....that said, can we conclude that if this panel was installed on the under belly or fuselage window opening , that this lettering would be visible looking upon the exterior of the plane?

Forget the "window opening."  The rivet pattern is all wrong.  The repaired skin was installed with the labeling on the exterior surface.  No way to tell whether the ink of the labeling was then buffed off.

In 1937 the Electra had a value of roughly $80,000 dollars during the depression ...all photos give the appearance of it being a highly polished vessel.

They do?  The attached photo shows the plane at Burbank on May 20, 1937 - the day after it came out of the repair shop, being loaded for the departure of the second attempt.  I would call that normally shiny bare aluminum but not highly polished.  The second photo shows the c/n 1015 Finch/Kammerer replica now at the Museum of Flight.  That's what highly polished looks like.  Earhart's Electra never looked that good.

During the reconstruction of the Electra after the Luke field incident, I came across photos of personal being shown x-raying the structural portions of the plane. To me it appears that quality and value was put into it's repair. With all this said, I wonder as to why lockheed or anyone ..(Miami) would place a panel in such fashion?

The quality of the repairs was governed by Lockheed and the Bureau of Air Commerce inspectors, not Earhart and Putnam.  Official correspondence related to the repairs shows that it was a rush job.  Earhart was pushing to get a new letter of authorization from the State Dept. to do the second attempt.  On May 14,  Putnam told the State Dept. the plane had been thoroughly repaired but the day before, the inspector in California said that it would take another ten days to complete repairs and inspections.  In fact, the work was completed in five days.

It is my opinion ( though others may not agree) that any such repairs would have been buffed to like quality.....would Putnam and Earhart insist on this considering the electra's value? I don't know that answer.

The photos and documents provide the answer.  The repairs were a rush job and cosmetics do not seem to have been a major concern.  The skin in question may or may not have been buffed. No way to tell, and it doesn't matter.  The presence of the etched A and D on the artifact could well have remained on a buffed surface.
Title: Re: Grand Rapids trip
Post by: Tim Collins on February 01, 2014, 08:52:13 AM
...the fastener "pulling out" could account for the dimpled appearance.  ...

My point has been that I think there should be more than mere "dimpling" should be considerably more pronounced given the scenerio of rivet heads popping off that has been suggested.   
Title: Re: Grand Rapids trip
Post by: Jon Romig on February 01, 2014, 11:28:38 AM
Jon...not sure i understand what you are saying...but the skin and rivets are not dissimilar metals; they are both aluminum...for that reason!'
They become "dissimilar" when located near a steel structure, for instance, particularly in water.
....
Bill

Hi Bill,

"Dissimilar metals" is a term that seems to be used generally to describe both dissimilar metals and dissimilar alloys, and I used it in that sense. The skin and the rivets were different alloys of aluminum.

Per Jeff Hayden's excellent and well-researched post above (#77), the rivets and the skin were dissimilar, meaning that they were well-separated on the galvanic series and thus would both experience corrosion by the same galvanic action that occurs between steel and aluminum.

Because we see no signs of galvanic corrosion on the artifact, I think we can conclude that it was not exposed to corroding condition (salt air and wetting?) for very long with the rivets in place.

It is also of interest that the one remaining rivet, shown in the NTSB report at Figure 1 (a very nice close-up photograph of the rivet) shows only minor corrosion, not what I would expect from long-duration galvanic action.

It would be very helpful to know if there is more corrosion under the head or in the rivet hole in the skin.

Jon
Title: Re: Grand Rapids trip
Post by: Jon Romig on February 01, 2014, 11:56:34 AM
It occurred to me that if water from an ebbing wave acted on one side of the skin, while water from a waxing wave acted on the other side of the skin the available forces might combine, doubling the available wave force .

Yes, that is a possibility.

The most likely condition is normal atmospheric pressure of 14.7 PSI on the "other" side. I am not certain if I should be adding that 14.7 PSI to the required pressure to cause the rivets to fail - after all atmospheric pressure is providing some significant support to the skin.

In your scenario, Tim, I think that the maximum "pull" from an ebbing wave would be a pure vacuum or 0 PSI (because vacuum is always zero, never negative), thus removing the pressure of air or water on the other side. My calculation (that indicated a required pressure of 38 PSI to fail the rivets) unintentionally assumed vacuum on the "other" side.

Jon

EDIT: After more though about whether I should be adding 14.7 PSI to the failure load, I believe I should not, as both the wave and the "other" side would be under that same pressure.
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on February 01, 2014, 01:25:11 PM
It would be very helpful to know if there is more corrosion under the head or in the rivet hole in the skin.

There is no apparent corrosion under the head or in the hole.
Title: Re: Grand Rapids trip
Post by: Gary L Kerr on February 01, 2014, 01:46:21 PM
If there was air and water moving around then the pressures could exceed 15 lbs.
Think of a pressure tank for a well system - anywhere pockets of air get compressed
by adding water (waves), the water and air pressure goes way up.
Title: Re: Grand Rapids trip
Post by: Jerry Germann on February 02, 2014, 12:00:33 PM
 

 
 
 
Earhart Project Research Bulletin #54
 8/1/2009 
A Piece of the Grail?

Abstract





A piece of bent sheet metal alleged to be a souvenir from the March 20, 1937 accident in Hawaii that ended Amelia Earhart’s first world flight attempt appears to match a specific feature on her aircraft.
 
Background

On September 19, 2008 TIGHAR received a request from the television production company that films the PBS series “History Detectives” for assistance in evaluating an artifact alleged to be a piece of Amelia Earhart’s Lockheed Electra. According to a document submitted with the artifact, it was obtained as a souvenir by a member of the U.S. Army Air Corps 50th Observation Squadron at Luke Field, Oahu on March 20, 1937 following the accident that ended Earhart’s first world flight attempt. The serviceman sent the piece of debris home to his mother who received it on April 3, 1937. She kept it “as a reminder of her admiration for Amelia Earhart.”

There is, of course, no way to be certain that the artifact came from NR16020, but photos sent by the production company showed several distinctive features. TIGHAR agreed to investigate further to determine whether the piece is consistent with its alleged origin. The artifact arrived at TIGHAR’s offices on October 20, 2008 and, for administrative purposes, was assigned TIGHAR artifact number 2-9-L-1.
 
General Description
Artifact photoArtifact 2-9-L-1 is a fragment of severely deformed sheet metal measuring nominally 5.25 inches (13.3 cm) by four inches (10.2 cm) with a thickness of .032 inch.

A.   Both edges of the long axis of the piece are fractured.

B.   One short edge features a .75 inch (1.9 cm) wide reinforcing strip of what appears to be anodized aluminum. The strip is attached to the sheet with flush rivets. Set into the reinforcing strip is the female component of a Dzus fastener – a closure device in which a slotted post (the male component) engages a wire (the female component) and, with one quarter-turn twist, draws the two components tightly together.

C.   The reinforcing strip ends with a finished corner after which the sheet features the rolled lip of what appears to have been a circular opening roughly five inches (12.7 cm) in diameter.

D.   The other short edge appears to have been cut using snips.

E.   Near the cut edge the sheet fractured through what appears to have once been a .125 inch (.3 cm) rivet.

The aluminum exhibits no sign of corrosion and appears to have been polished before, but not after, the event that resulted in its deformation. The exterior surface (based upon the orientation of the Dzus fastener) exhibits evidence of impact and abrasion.
 
Clues

Polished Electra
Earhart’s technical adviser Paul Mantz with the Electra on March 19, 1937, the day before the accident.
1.The sheet metal is consistent with 24ST (known today as 2024) Alclad, the type of aluminum used in the construction of Earhart’s Electra. Polishing Alclad to a shiny finish is a labor-intensive process and is usually done purely for show. Photographs of Earhart’s Electra prior to the accident show that the aluminum was polished.2.The metal shows no sign of weathering, suggesting that it has been in a protected, dry environment. It is unusual for aircraft wreckage to be carefully preserved. The artifact’s condition is consistent with it being kept as a treasured souvenir.
3.Dzus fasteners are usually used on aircraft to close access doors and to attach panels that need to be easily removable for maintenance. The female component of the fastener is naturally mounted to a stable surface, often a bulkhead or the reinforced frame around an access door. In this case, the female component of the fastener is mounted on sheet aluminum with no nearby line of reinforcing rivets – an unusual application.
4.The strip in which the Dzus fastener is mounted ends in a finished corner. Beyond the corner, the edge of the metal sheet is rolled to form the lip of a circular opening.
 
Comparison to C/N 1052

C/N 1052
Lockheed Electra 10A c/n1052 at the New England Air Museum, Windsor Locks, Connecticut.
AE and plane
Earhart’s Lockheed Model 10E Special, c/n1055.
Luke Field wreck
 On November 19, 2008, TIGHAR Executive Director Ric Gillespie made a direct comparison of Artifact 2-9-L-1 to Lockheed Electra 10A constructor’s number (c/n) 1052 at the New England Air Museum in Windsor Locks, Connecticut. Although only three serial numbers from Earhart’s c/n 1055, the airplane in Connecticut is a 10A, equipped with 450 hp Pratt & Whitney R985 Wasp Junior engines. Earhart’s Electra was a 10E equipped with 550 hp Pratt & Whitney R1340 S3H1 Wasps of slightly larger diameter.

No location on c/n 1052 matches artifact 2-9-L-1. However, there are double-sided doors on the underside of each engine nacelle that provide access to the carburetor.

Doors on 1052
Double-sided access door on underside of engine nacelle, Lockheed 10A c/n1052.
Nacelle
Artifact 2-9-L-1 overlaid on drawing of underside of
 left engine nacelle of Earhart’s Electra
 The doors are secured closed by means of Dzus fasteners. Because the female components of the fasteners are mounted on half of the door, rather than on a stable structure, they match one of the distinctive features of the artifact – a female Dzus fastener set in a piece of plain metal sheet.

Photos of the same area on Earhart’s 10E c/n 1055 reveal a similar double-sided door closed with Dzus fasteners, but of somewhat larger dimensions and with different cut-outs.

A photo of the Luke Field wreck taken during salvage operations shows extensive damage to the area in question on the underside of the left engine and may show a hinge where the door was torn off.
 
Conclusion

There appears to be a high probability that Artifact 2-9-L-1 is as represented – a souvenir piece cut from Earhart’s wrecked Lockheed Electra.


 
Archived Research Bulletins Earhart Project Home Page
 
My conclusion as to polishing was derived from documents such as this , as well as photos in the Purdue archives,... if one goes to the quick search box at the Purdue e archives Earhart collection site .... type in Electra, ( numbering will change if other entries are submitted)... the following photos seem to indicate polishing, ..some photos estimate dates as being pre Luke field incident , some final flight....Numbers 20,30,35,83,93,94,135,and 169.are examples.
In my opinion black and white photographs do not give a proper representation of an objects reflective properties. An example would be the Cord /Electra photo...the hubcaps/bumpers/windshield frame/etc., don't appear all that much brighter than the Electra's skin in the background, and they are brand new chrome. The Finch replica is what we antique auto enthusiasts would label an OVER restoration. Numerous examples exist today in the automobile field due to improvements in paints, methods of application, and burnishing procedures. (Henry Ford's Model T never looked that good new). Can other factors contribute to an objects captured appearance? Time of day the photo was taken, film/dust on the object / angle of photo as compared to object could be some. It is my belief that Earhart's plane was polished as per the method of the day...no, not as brilliantly as today's techniques would produce...what method would be required to remove the ink stamp on the panel, a simple solvent wash or??? Also during Luke field repairs was this the only panel installed in this manner , what if several were done this way, I just can't agree with the thought that Lockheed or others wouldn't be conscientious enough to pay attention to this detail ...after all  Earhart and her plane were to go before a worldwide audience?
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on February 02, 2014, 04:11:28 PM
It is my belief that Earhart's plane was polished as per the method of the day...no, not as brilliantly as today's techniques would produce...what method would be required to remove the ink stamp on the panel, a simple solvent wash or???

As I have tried to communicate, apparently in vain:
We don't know how the letters A and D became etched on the sheet.  There is no sign of the rest of the labeling. The letters are only discernible if you catch the light just right. In short, there is no way to tell whether the original inked labeling was buffed off or not.

Also during Luke field repairs was this the only panel installed in this manner , what if several were done this way, I just can't agree with the thought that Lockheed or others wouldn't be conscientious enough to pay attention to this detail ...after all  Earhart and her plane were to go before a worldwide audience?

No one is suggesting that Lockheed did not pay attention to this detail.
Title: Re: Grand Rapids trip
Post by: JNev on February 03, 2014, 07:13:38 AM
....that said, can we conclude that if this panel was installed on the under belly or fuselage window opening , that this lettering would be visible looking upon the exterior of the plane?

Forget the "window opening."  The rivet pattern is all wrong.  The repaired skin was installed with the labeling on the exterior surface.  No way to tell whether the ink of the labeling was then buffed off.

Which rivets - along the edges?  The intermediate rivets seem like afterthought but the peripheral / larger rivets must be what you are referring to.  Is there enough evidence available to us as to the spacing to eliminate a possibility as to attachment to that part of the Electra? 

What about the 'large' window frame - upper edges - may well not have matched original pitch on the stock L10E; do we have details on rivet pitch for that area?

Good if we can eliminate a particular area, but it would be good to substantiate how we know this before doing so.
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on February 03, 2014, 09:36:39 AM
The intermediate rivets seem like afterthought but the peripheral / larger rivets must be what you are referring to.  Is there enough evidence available to us as to the spacing to eliminate a possibility as to attachment to that part of the Electra? 

I'm not sure what you mean by "intermediate rivets."  All of the rivets holes on the artifact are 3/16ths shaft diameter except for the line along edge that are 5/16ths.  The sole surviving rivet is a 3/16ths  brazier head. 

What about the 'large' window frame - upper edges - may well not have matched original pitch on the stock L10E; do we have details on rivet pitch for that area?

There is a photo of the plane in Miami with the freshly-installed (shiny) patch where the large window used to be.  I have a print of it but I can't put my hands on it at the moment. (Still sorting out boxes from the move.) The photo gives a good idea of the rivet pattern on the patch.  Nothing like the artifact.
Title: Re: Grand Rapids trip
Post by: JNev on February 03, 2014, 09:58:30 AM
The intermediate rivets seem like afterthought but the peripheral / larger rivets must be what you are referring to.  Is there enough evidence available to us as to the spacing to eliminate a possibility as to attachment to that part of the Electra? 

I'm not sure what you mean by "intermediate rivets."  All of the rivets holes on the artifact are 3/16ths shaft diameter except for the line along edge that are 5/16ths.   The sole surviving rivet is a 3/16ths  brazier head. 

Thanks Ric.  'Intermediate' = 3/32" (not 3/16"?) lines lying well within sheet boundaries in my meaning.  My thought has been that those may be a crap-shoot - not necessarily patterned after existing holes on Electra, whereas those along the edge might coincide with something we could identify as an original pattern on the Electra.

What about the 'large' window frame - upper edges - may well not have matched original pitch on the stock L10E; do we have details on rivet pitch for that area?

Quote
There is a photo of the plane in Miami with the freshly-installed (shiny) patch where the large window used to be.  I have a print of it but I can't put my hands on it at the moment. (Still sorting out boxes from the move.) The photo gives a good idea of the rivet pattern on the patch.  Nothing like the artifact.

That information is very much appreciated, especially if you can find that picture (I believe you of course, but it would be cool to see if / when you can find and post - many other priorities I realize).  Good photographic evidence of what that patch really was is something I've been looking for to do a comparison and it is good to know there is some of course, even if it rules the lav window area out.

The only remaining question I might have is whether we have enough edge-pattern evidence for a conclusion to that - but I take it you have been able to see that the edge-rivet pattern on the artifact distinctly does not match what can be observed in that photo - well enough.

Perhaps a breakthrough will come for the belly or elsewhere yet - this 'skin' is still a great find as I see it.
Title: Re: Grand Rapids trip
Post by: Walter Runck on February 03, 2014, 10:15:50 AM
Do we have anything that shows the "before and after" of the window installation?
Title: Re: Grand Rapids trip
Post by: Martin X. Moleski, SJ on February 03, 2014, 10:23:40 AM
Do we have anything that shows the "before and after" of the window installation?

From a small gallery of photographs (http://tighar.org/wiki/NR16020#Gallery) hidden on the website where no one can find them:

(http://tighar.org/aw/mediawiki/images/e/ea/Wheeler_Field%2C_Mar_19%2C_1937_Hawaii_Aviation.jpg)


(http://tighar.org/aw/mediawiki/images/1/19/Electrairb.jpg)
Title: Re: Grand Rapids trip
Post by: JNev on February 03, 2014, 10:30:21 AM
Do we have anything that shows the "before and after" of the window installation?

From a small gallery of photographs (http://tighar.org/wiki/NR16020#Gallery) hidden on the website where no one can find them:
...

Clarification: I realize this post of Marty's was in response to Walter Runck - was just adding a sidebar; re-worded [in barckets] to clear that up -

Thanks Marty [for posting these for Walter - and all our benefit] - I think I've already posted similar (http://tighar.org/smf/index.php/topic,717.msg14267.html#msg14267) myself, as obtained from this very site as you cite [meaning, tongue-in-cheek - we have a wealth of such stuff on TIGHAR site - just takes a bit of digging to get at it sometimes]...  ;)

What I still hope to see is the photo Ric mentioned that provides greater photographic detail of the window covering installation.  That is something long longed-for.

[And now on to the later post by Ric as to the belly area - fascinating.]
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on February 03, 2014, 11:09:43 AM
'Intermediate' = 3/32" (not 3/16"?) lines lying well within sheet boundaries in my meaning.  My thought has been that those may be a crap-shoot - not necessarily patterned after existing holes on Electra, whereas those along the edge might coincide with something we could identify as an original pattern on the Electra.

Yes, 3/32".  My bad. 
From the NTSB report: "The remains of a solid brazier-head rivet were found in the hole denoted by arrow "R" in
figure 1. The manufactured head of the rivet was on the convex side of
the sheet and was marked with a single round dimple in the center of the
head, as shown in the right center photograph of figure 1. The dimple
usually signifies a 2117 aluminum alloy rivet. The length of the
undeformed rivet shank (distance between the manufactured head and the
formed head) indicated that the skin had previously been attached to an
approximately 0.06 inch thick underlying member."

In other words, those "intermediate" rivet holes indicate the former presence of underlying members, presumably stringers.
 
Perhaps a breakthrough will come for the belly or elsewhere yet - this 'skin' is still a great find as I see it.

The breakthrough has already broken through. All aspects of the artifact, including the rivet pattern, fit closely with a section of the belly on the right hand side of the aircraft between stations 269 5/8ths and 293 5/8ths.  The apparent discrepancy in the spacing between stringers may be due to distortion due to the deformation of the fragment of skin when it blew out of the belly.  The one known discrepancy between the rivet holes in the artifact and standard Electra construction is the line of 5/32" holes along the one edge.  The standard airplane has a double row of staggered 3/32" rivets along the keel where the skins overlap.  The artifact shows evidence of a double row of staggered 5/32 rivets.  Aris Scarla sees the use of larger rivets along the keel in the repair as a reasonable possibility in the repair of NR16020.
Title: Re: Grand Rapids trip
Post by: Monty Fowler on February 03, 2014, 11:43:01 AM
*points up to photo* If that's not a case of "A picture is worth a thousand words," then I don't know what is.

LTM,
Monty Fowler, TIGHAR No. 2189 CER
Title: Re: Grand Rapids trip
Post by: Walter Runck on February 03, 2014, 11:47:45 AM
Do we have anything that shows the "before and after" of the window installation?

From a small gallery of photographs (http://tighar.org/wiki/NR16020#Gallery) hidden on the website where no one can find them:


I should have been more specific.  By "installation", I meant the details of how the hole was cut, framed and glazed, so for me, interior shots would be much more helpful. 

I'm using the window as a homework project for some CAD work I'm doing.  In general, I want to model that section of the fuselage "as built", then modify it to show the window "as installed", then add the "as covered" details.  Finally, the model will be subjected to hydraulic loads to see what happens and/or breaks.   

I don't expect any relevations concerning the Electra, artifact or Niku.  The goal for me is to improve my skills with this kind of software. It's just more fun to use an example from something you're interested in than a generic widget.

That said, any info regarding the shape and size of the fuselage components in this area would be appreciated.
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on February 03, 2014, 11:49:30 AM
*points up to photo* If that's not a case of "A picture is worth a thousand words," then I don't know what is.

A word of caution.  The overlay in that photo cannot be considered exactly to scale.  There are problems with perspective.  The photos of the artifact was taken from almost directly overhead and the photo of the belly structure of c/n 1052 is slightly oblique.  There is also the problem that the artifact was deformed when it was blown out.   The photo does show, however, that we're in the ballpark.  The actual match up might be even better.
Title: Re: Grand Rapids trip
Post by: Monty Fowler on February 03, 2014, 11:58:54 AM
I'll settle for  ballpark for the moment. I can see all the edges in a ballpark.

LTM, who thinks 2014 will be homerun time for TIGHAR,
Monty Fowler, TIGHAR No. 2189 CER
Title: Re: Grand Rapids trip
Post by: Walter Runck on February 03, 2014, 12:42:26 PM

A word of caution.  The overlay in that photo cannot be considered exactly to scale.  There are problems with perspective.  The photos of the artifact was taken from almost directly overhead and the photo of the belly structure of c/n 1052 is slightly oblique.  There is also the problem that the artifact was deformed when it was blown out.   The photo does show, however, that we're in the ballpark.  The actual match up might be even better.

Match up to what?  If the stringers were replaced as part of the repair, might they not have been offset?  I can't tell how the originals were attached, but new ones may have required fresh locations.  If so, the rivet pattern of the replacement skin wouldn't be expected to match the original stringers.
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on February 03, 2014, 01:10:44 PM
Match up to what?  If the stringers were replaced as part of the repair, might they not have been offset?  I can't tell how the originals were attached, but new ones may have required fresh locations.  If so, the rivet pattern of the replacement skin wouldn't be expected to match the original stringers.

Any major repositioning of stringers would require special engineering drawings mentioned in the Repair Orders and approved by the Bureau of Air Commerce. Such drawings were mentioned in the Repair Orders for strengthening splices on the nacelle ribs (where the landing gear had failed) and the subject special engineering drawings are part of the repair record.  The Repair Orders call for replacement of the skin of which 2-2-V-1 seems to be a part but no drawings are mentioned, so we must presume that the stringers didn't move much, if at all.
Title: Re: Grand Rapids trip
Post by: JNev on February 03, 2014, 01:12:35 PM
'Intermediate' = 3/32" (not 3/16"?) lines lying well within sheet boundaries in my meaning.  My thought has been that those may be a crap-shoot - not necessarily patterned after existing holes on Electra, whereas those along the edge might coincide with something we could identify as an original pattern on the Electra.

Yes, 3/32".  My bad. 
From the NTSB report: "The remains of a solid brazier-head rivet were found in the hole denoted by arrow "R" in
figure 1. The manufactured head of the rivet was on the convex side of
the sheet and was marked with a single round dimple in the center of the
head, as shown in the right center photograph of figure 1. The dimple
usually signifies a 2117 aluminum alloy rivet. The length of the
undeformed rivet shank (distance between the manufactured head and the
formed head) indicated that the skin had previously been attached to an
approximately 0.06 inch thick underlying member."

In other words, those "intermediate" rivet holes indicate the former presence of underlying members, presumably stringers.

Good stuff - and .060" is substantial thickness for an 'underlying member' - which could easily be an underlying skin and stringer flange combined.  That suggests an external doubler to me rather than a replacement skin - one that would pick-up all thicknesses underlying the outer doubler. 

That would not be unheard of where a rapid repair scheme was employed - not the neatest approach (in essence a large 'scab patch') but effective enough if  the area had relatively mild damage and a quick reinforcement was decided upon in lieu of a more complex removal / replacement.  The use of such small rivets (in the 'intermediate' rows) is odd - the expected norm would be 1/8" or larger diameter - but again, in a rapid repair situation this could certainly happen.  in the context of so many things we know about Earhart and Putnam, their priorities (and lack of on certain things) and that it is not a perfect world, that kind of stuff can easily happen.
 
Perhaps a breakthrough will come for the belly or elsewhere yet - this 'skin' is still a great find as I see it.

Quote
The breakthrough has already broken through. All aspects of the artifact, including the rivet pattern, fit closely with a section of the belly on the right hand side of the aircraft between stations 269 5/8ths and 293 5/8ths.  The apparent discrepancy in the spacing between stringers may be due to distortion due to the deformation of the fragment of skin when it blew out of the belly.  The one known discrepancy between the rivet holes in the artifact and standard Electra construction is the line of 5/32" holes along the one edge.  The standard airplane has a double row of staggered 3/32" rivets along the keel where the skins overlap.  The artifact shows evidence of a double row of staggered 5/32 rivets.  Aris Scarla sees the use of larger rivets along the keel in the repair as a reasonable possibility in the repair of NR16020.

I'm surprised that the original stock keel skin lap joint had 3/32" rivets - if that is accurate then it reveals something that might be even more supportive.  I'd double-check that figure - surprised to hear of rivets smaller than the typical 'no smaller than' no. 4 (1/8") rivets commonly expected for primary structure.  Nonetheless, 5/32" may be the rational 'next size' replacement so common where repairs are concerned.

The distortion is significant looking - that outboard row / edge diverts noticeably from the standard stringer location.  But we don't know for certain that N16020 did not have a mod in that local area for some reason - there was a nav station in that area of the floor and there could have been a sub-floor alteration to accomodate some installation we don't know anything about yet.  And as you've pointed out, the destructive force of whatever took that member out of the parent structure could well have imparted some degree of stretching or distortion as well.  That is a lot for heat-treated dural to endure without splitting, but between that possibility and that of a modified structure it could easily be.

Very interesting, and a picture is a worth many words.  I appreciate Mr. Scarla's comments on the matter - I'm sure he's seen many real-world repair and alteration schemes and knows his analysis well.
Title: Re: Grand Rapids trip
Post by: Friend Weller on February 03, 2014, 01:26:56 PM
A thought:  what if the artifact was not "blown out" by hydraulic forces or wave action?  Since it corresponds closely with the floor section opposite the cabin door, what would be the possibility that as NR16020 was going over the reef edge that the airframe crumpled/buckled on the door side, this being a "weaker" point compared to other more continuous portions of the fuselage (no "large" openings), causing the skin on the starboard side of the aircraft to "expand", stretching and tearing free?  As the artifact appears to be from closer to the "keel" of the airframe, this might result in less deformation of the artifact compared to a location higher up on the side of the fuselage where more drastic tearing would take place (starboard) or crumpling/buckling (port).  I can envision that if the aircraft were to buckle laterally at this station, the floor skin could be torn and popped out from it's installed position.  Not being an airframe engineer but having worked closely on a small all-aluminum airplane project years ago, my experience causes me wonder if this area of the Electra was not particularly resistant to side-to-side forces but designed more for vertical loads and moments between the wing and the empennage.    Just a thought.....

Friend
Title: Re: Grand Rapids trip
Post by: Ted G Campbell on February 03, 2014, 02:57:15 PM
Ric,

If one would lay a thin layer of Mylar over the inside and outside of 2-2-V-1 – matching the bulge (deformation) as best as one can – then cut the Mylar along the edges to trace the outline of 2-2-V-1 could we then see how the flatten template might match the original skin?  I guess where this template might deviate from the original skin is if 2-2-V-1 underwent stretching and thinning significantly in the bulged area.  Low cost exercise I would think.

Ted Campbell
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on February 03, 2014, 03:33:27 PM
If one would lay a thin layer of Mylar over the inside and outside of 2-2-V-1 – matching the bulge (deformation) as best as one can – then cut the Mylar along the edges to trace the outline of 2-2-V-1 could we then see how the flatten template might match the original skin?  I guess where this template might deviate from the original skin is if 2-2-V-1 underwent stretching and thinning significantly in the bulged area.  Low cost exercise I would think.

That has been done and it is that exercise that seems to have resulted in the distorted impression that caused us to see discrepancies that might not be there.  It turns out to be a very tricky thing to take a piece of deformed wreckage and determine it's exact dimensions and features when it was undamaged.  Aris Scarla assures me there are ways to do it.  I await his advice and  assistance.
Title: Re: Grand Rapids trip
Post by: Friend Weller on February 03, 2014, 09:49:45 PM
After taking another look at the overlay photo of the artifact and the Harney drawings on the site, I noticed the proximity of the aft ventral antenna mast to the area of the the artifact.  If we accept the theory of the loss of the antenna upon takeoff from Lae, would it be reasonable to postulate that during the loss of the mast, the underside of the aircraft in the vicinity of the artifact may have been damaged just enough to crack stiffeners or pop rivets creating a weakened area?  This could have been either from the sudden forcing upward and aft of the mast upon contact with the ground surface while taxiing or the hammering of the underside of the aircraft as the mast bounced along during the takeoff roll prior to the antenna separating from the plane.  If enough rivets were popped from the deformation of the skin and stiffeners, this may have resulted in 20+ hours of "oil-canning" during the flight or perhaps severe weakening during the landing fatiguing the skin in that area making it easier for it to fracture/tear/pop when NR16020 went over the reef edge.

Random thoughts?   Cabin fever?  If this scenario has been discussed and decided before, my apologies!
Friend
Title: Re: Grand Rapids trip
Post by: Walter Runck on February 03, 2014, 10:55:26 PM
It turns out to be a very tricky thing to take a piece of deformed wreckage and determine it's exact dimensions and features when it was undamaged.  Aris Scarla assures me there are ways to do it.  I await his advice and  assistance.

There is design software that does exactly that with sheet metal.  You create a model of the end product and then it figures out where the bends would have to be placed to get that result.  One of the outputs is the flattened shape that you would need to start with to make the (de)formed part.

It works very well for things with clean features like straight lines and right angles.  The difficulty with more complex shapes comes in the fidelity of the model.  You can either build a math model and try to create the shape using geometric building blocks or run the part through a 3D scanner and work with a numerically defined shape model.

I expect there are versions of software customized for forensic work that I don't have access to, but the  standard stuff might provide at least a rough answer.  It would, however, require a higher level of measurement fidelity than I have seen for this part.
Title: Re: Grand Rapids trip
Post by: Greg Daspit on February 04, 2014, 02:21:29 PM
The scratches/ suggestive pry marks noted in the initial summary of 2-2-V-1 (http://tighar.org/Publications/TTracks/12_2/obj6.html) and how this aircraft skin was found tangled with the antenna lead are a puzzle to me. The possible pry marks suggest salvage but the tangled wire and good condition of the aluminum do suggest wash up and temporary cover by sand. It could be the aircraft skin was salvaged and abandoned.
Also a tear on one side of 2-2-V-1 being folded in, not out. (I think I am seeing that right?) Could the popped rivets, the fold-in and the pry marks be part of a process including isolated wave force, fuselage break-up and then salvage?
Also why the Bevington object stayed on the reef and the little wheels I see in the debris field (http://tighar.org/smf/index.php/topic,1014.0.html) could all be related to the fisherman John Mims (http://tighar.org/wiki/John_Mims) saw and control cable. This fisherman could have cut the control cable holding the landing gear and other stuff on the reef and salvaged the 2-2-V-1 aircraft skin. Some of the other control cable may have held a pulley to the wing edge and continued down the reef slope possibly seen in the debris field.
See sketch
Title: Re: Grand Rapids trip
Post by: Jerry Germann on February 04, 2014, 03:02:27 PM
The scratches/ suggestive pry marks noted in the initial summary of 2-2-V-1 (http://tighar.org/Publications/TTracks/12_2/obj6.html) and how this aircraft skin was found tangled with the antenna lead are a puzzle to me. The possible pry marks suggest salvage

Question; ....is it still the concensus that the scratch marks noted on the panel when initially found, were the result of the use of a prying tool ? If so, wouldn't that indicate that either ( stringers/supports) or parts thereof were attached to this panel before said prying action.... becoming separated later by this prying means? If that is true, then what force /action would separate not only this panel from the larger sheet, but possibly detach one or more supports along with it as well? 
Also, may this artifact have been repurposed, and the resulting damage sustained then? 
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on February 04, 2014, 06:31:23 PM
Question; ....is it still the concensus that the scratch marks noted on the panel when initially found, were the result of the use of a prying tool ?

Yes.

If so, wouldn't that indicate that either ( stringers/supports) or parts thereof were attached to this panel before said prying action.... becoming separated later by this prying means?

Yep.

If that is true, then what force /action would separate not only this panel from the larger sheet, but possibly detach one or more supports along with it as well?

Breaking waves.
 
Also, may this artifact have been repurposed, and the resulting damage sustained then?

The sheet may very well have been repurposed but after it sustained the damage. The fragment of sheet seems to have separated from the aircraft with pieces of stringers still attached (only a few of the rivet holes show evidence of prying).  The sheet later washed up and was found by a local who saw its potential usefulness as a griddle for cooking.  The local pried off the surviving pieces of stringer.  This hypothesis is supported by ALCOA's finding that portions of the sheet have lost ductility due to being heated and anecdotal accounts from former Nikumaroro residents who describe just such a piece of aluminum with rivet holes being used to cook fish.
Title: Re: Grand Rapids trip
Post by: JNev on February 05, 2014, 12:26:27 PM
I need to share that this artifact has created a major tipping point in my view of the Niku landing hypothesis -

In my opinion as an A and P Mechanic / IA of some 36+ years - 33 of those in various roles at a major airframer including maintenance, repair, inspection and engineering, I find this surprisingly complex artifact to be  compelling: this skin truly could have originated from the belly repairs done to NR16020 prior to the world flight.  In fact, it represents such a unique slice of potential that to me it cannot be just "anything": too much is now realized about the character of this item and where it lies in the aviation timeline for material, construction practices and the circumstances of the belly repairs done on NR16020 to ignore the potential. 

Couple that with the strong context of so many other things shared here - including other 'odd' things like plexiglass matching in thickness and contour to that of L10 Lockheed windows  (http://tighar.org/Publications/TTracks/1996Vol_12/40552.pdf?wwparam=1380630369) and the case only gets stronger. 

The Lockheed L10 has proven herself a stand-out in yet another new way to this old mechanic: her belly skins do include a large number of no. 3 rivets as primary strucural fasteners.  This had been a hard sticking point with me for some time and threw me into the "could be anything" camp for quite some time.  Now I realize the first all-metal transport used some arcane features as it pioneered so much taken for granted today - the Lockheed engineers mastered the reduction of material to build a light but durable stressed-skin bird before the onset of later guidance that tended toward heavier building practices.  I now believe we are seeing an example of repair to none other than one such craft.  I also know of only one such example that would have borne such light work in that part of the world. 

Are there other possibilities?  Of course - but a time has come for me to seriously suggest that they are very limited indeed: AN 455 brazier rivets of no. 3 size coinciding with a similar feature in the L10 is not so common, nor are the pre-war markings we find on this sheet.

One realizes that this sheet of ruined metal 'could be anything' to many eyes and minds - but training, experience and now observation and acceptance of some hard data make this complex item very pointed in its meaning.  The scales have tipped IMO - if there is a better explanation as to where this came from given the web of circumstantial (but substantial to this writer) evidence we have - including plexiglass of correct curvature and thickness, etc. - I would respectfully ask the challenger to provide evidence of it.

This is of course my humble opinion, but I suggest the skeptic study and look hard if they'd offer a better idea of what became of the flight.  As to where found and how it got there - a worthy consideration, consider what now appears to be strong provenance as to this part: if it came from the Electra, but not at Niku - then where else?

I merely (but now strongly) suggest that there is not a wealth of other possibilities.  The reader must of course draw his own conclusions.  But mine, after quite a journey, is that somehow a unique piece of aviation repair history managed to beach itself on the shores of Niku - among other nested things that support the circumstance of a stranded L10E belonging to Amelia Earhart.

This is my own opinion - others may of course play the odds as they will, but I submit that TIGHAR's pain-staking efforts have produced plausible material that reaches beyond reasonable doubt. 

This is reason itself for me after a long journey - I can think of no better notion of where this piece of history came from given all we know to-date - and now what I discern in this part is just too specific to ignore.  The full context as underpinned by the specifics of this part and others like the plexiglass tells me that Earhart found Gardner in 1937.

Hats off to all those who care about and search for the lost aviators, whether they agree or not - may they always be reasoned and reasonable in their arguments.  TIGHAR's reasoning after much labor tips the case strongly to Niku IMO - I respect that a great deal.  It is my hope that further searching will produce the airplane, but short of that and barring something more weighty than we have here (not expected, frankly), the circumstances of what has been found point to Gardner as host to a certain famous L10E in 1937.  Thanks to Ric and TIGHAR for the vision of it, and the hard work to reveal all that can be found to prove it.
Title: Re: Grand Rapids trip
Post by: Jerry Germann on February 09, 2014, 12:41:59 PM
Aris Scarla, Bob Brandenburg and I are designing an experiment to confirm how much and what kind of force is needed to cause the damage we see on the artifact.  Aris can build a reproduction of the belly of the Electra in the area where we think the failure occurred. The same aluminum sheet and stringers are commonly available today but finding the old-style brazier head rivets might be tricky.  Bob can calculate the required force.  We'll need to partner with a university or research facility that has the capability to generate the kind of fluid force we need.

Knowing what it takes to cause this kind of damage will tell us a great deal about what circumstances the aircraft the artifact came from must have experienced. That, in turn, should enable us to refine our hypothesis of what happened to NR16020 and how much of it is likely to be left to find.
Was wondering how this experiment was progressing, and in doing this procedure , does one perform this test with a replica of the wooden floor walkway panel in place above this area? Further,.. if this panel fits this area of the underbelly, (and we assume the area aft of this location was detached from the rest of the plane),... would the remaining length of the surviving nose to suggested separation point of the structure duplicate the anomaly's size?
Title: Re: Grand Rapids trip
Post by: Tim Mellon on February 09, 2014, 02:05:50 PM

Further,.. if this panel fits this area of the underbelly, (and we assume the area aft of this location was detached from the rest of the plane),... would the remaining length of the surviving nose to suggested separation point of the structure duplicate the anomaly's size?

It very well might, Jerry, but since the entire center section of the fuselage (aft of the main beam back to the lavatory) lies elsewhere at a depth of 1046 feet, the coincidence would hardly matter.
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on February 09, 2014, 04:03:43 PM
Was wondering how this experiment was progressing, and in doing this procedure , does one perform this test with a replica of the wooden floor walkway panel in place above this area? Further,.. if this panel fits this area of the underbelly, (and we assume the area aft of this location was detached from the rest of the plane),... would the remaining length of the surviving nose to suggested separation point of the structure duplicate the anomaly's size?

We're not making any assumptions at this point and we're still discussing the design of the experiment - and it's waaaay too early to worry about how all this might fit with the anomaly.  The first step is to confirm that the artifact is from NR16020.  If it's not then we don't much care how it got the way it is.
Title: Re: Grand Rapids trip
Post by: Tim Mellon on February 09, 2014, 06:15:29 PM
Ric, a suggestion:

If you ever get back to Niku with an ROV, why don't you dive down 1046 feet and see if the 2-2-V-1 artifact is actually missing from the bottom of the fuselage near the main entry door.

As to why it became detached, why not take the advice of your colleague, the former Secretary of State, Hillary R. Clinton:

               "What difference does it make?"

Title: Re: Grand Rapids trip
Post by: Tim Mellon on February 09, 2014, 06:35:04 PM
Oh, here is a capture of the Main Beam from the 2012 Standard Definition Video showing the cutouts in comparison to a photograph of the construction of the Electra.


Title: Re: Grand Rapids trip
Post by: Jeff Lange on February 09, 2014, 09:13:48 PM
I'm sorry, but once again, I just don't see what Tim sees.

Since my mother taught me that if I had nothing nice to say, then say nothing at all, I will hold further comment.
Title: Re: Grand Rapids trip
Post by: JNev on February 10, 2014, 06:16:51 AM
I see rocks personally but then I've already confessed being in the 'blind idiot' camp most likely when it comes to these underwater photos.

Tim, how is it that none of the rest of us can see what you do?  It appears it will take another close look-see to verify it for public consumption, and since you are very convinced it would be really cool if you backed that effort, IMO.  I'll pitch in what I can in the spirit of that.
Title: Re: Grand Rapids trip
Post by: THWWallace on February 10, 2014, 08:38:23 AM
I'm sorry, but once again, I just don't see what Tim sees.

Since my mother taught me that if I had nothing nice to say, then say nothing at all, I will hold further comment.

Jeff,

A.)  There's a reason that you (and I, and many, many others) don't see what Tim sees. 
B.)  My prediction:  They'll be much less debate about the 2015 images.  In fact, they'll be no debate whatsoever.   
C.)  I too with withhold further comment, my father having taught me what your mother taught you. 

Title: Re: Grand Rapids trip
Post by: Monty Fowler on February 10, 2014, 09:37:59 AM
I will have to side with Ric on this one, first we have to figure out if this large piece of aluminum sheet is from our own very special Electra, before we expend time, very scarce funds and almost as scarce effort in trying to figure out how it got the way it did.

With this riddle, as with so may others in the Amelia and Fred saga, I am reminded of the term they use in psychology, where the tendency for the mind to find coincidences, patterns and connections in random data is called apophenia.

LTM, who tries to keep his patterns simple,
Monty Fowler, TIGHAR No. 2189 CER
Title: Re: Grand Rapids trip
Post by: John Ousterhout on February 10, 2014, 10:07:13 AM
The bulged deformation of the sheet might be explained, not by an unusual high-speed wave impacting a stationary aircraft on the reef, but by an aircraft impacting water at high speed, as in a crash or forced landing.  Ric or others might have some experience seeing the kind of damage caused by aircraft crashing into water and could advise us how the artifact differs in appearance.
Title: Re: Grand Rapids trip
Post by: JNev on February 10, 2014, 10:27:08 AM
The bulged deformation of the sheet might be explained, not by an unusual high-speed wave impacting a stationary aircraft on the reef, but by an aircraft impacting water at high speed, as in a crash or forced landing.  Ric or others might have some experience seeing the kind of damage caused by aircraft crashing into water and could advise us how the artifact differs in appearance.

Don't forget that it may have been the same as described being used over a fire to cook fish.

"How the sheet got this way" may be an extremely complex determination, whereas just the fact of its having separated by fatigue (whether high or low cyclic) and being weather-beaten by a number of island conditions should tell us much, even without super-specifics.

Bottom line to me with great respect for others who differ - 'where did it come from' is first, yes - and the signatures on this complex piece point strongly now to the belly of a certain L10 due to metal type, pattern of fasteners which while not perfect is very close to at least one known Electra, and rivet type, plus vintage clearly established by method of factory marking, and now even possibly the habit of turning markings outward (on convex surface) as did Lockheed (as in picture provided by Ric).

The Airacobras 200 miles away were worth looking at, but now having looked at that type I don't see a match: they were of more robust military-style construction and exhibit largely flush-fastened skins.  Could it have been an interior piece?  You'd have to find something with stringers that are much more commonly associated with exterior skins, but yes.  Apparently we'd need to look for something with a contour too - odd for interior appointments.
Title: Re: Grand Rapids trip
Post by: Tim Mellon on February 10, 2014, 11:30:13 AM

Tim, how is it that none of the rest of us can see what you do?

That's a really good question, Jeff. All three of the forensic guys working on these images have no problem at all seeing what I can see. (Also, we have no idea what proportion of the 300+ folks that have now looked at this image can see it).

Maybe the attached annotation will be of assistance in identifying the details of the image. A clean copy is also provided. The fuselage hulk (without roof) stretches from the Main Beam towards the upper left corner of the picture.

Title: Re: Grand Rapids trip
Post by: JNev on February 10, 2014, 11:50:38 AM

Tim, how is it that none of the rest of us can see what you do?

That's a really good question, Jeff. All three of the forensic guys working on these images have no problem at all seeing what I can see. (Also, we have no idea what proportion of the 300+ folks that have now looked at this image can see it).

Maybe the attached annotation will be of assistance in identifying the details of the image. A clean copy is also provided. The fuselage hulk (without roof) stretches from the Main Beam towards the upper left corner of the picture.

For the door to be juxtaposed to the windows in that manner, it would have to have been on the right-side of the fuselage, I believe.  Earhart's bird did not have that many windows - the normal cabin windows were rather permanently closed-in as I recall, except for the RH aft window (across from door) and the door itself still having a window. 

Were the fuselage on its back then I guess they would be juxtaposed as you suggest, except that the water lines are all wrong - the windows would be 'below' the door level - or so it looks to me by what you've illustrated.

I would like to know how your experts are going to convince the public, who does not so far in all these years seem interested in rolling over to accept someone else's view of what's what out there... with all due respect, I remain unconvinced that we're seeing Lockheed Electra wreckage at all, as much as I'd love to see it (and I'm quite capable of acute apophenia where these images are concerned without a doubt). 

If it were me I'd be sure my experts weren't using a bit of license at my expense, Tim - just MHO.  People do so like to please...
Title: Re: Grand Rapids trip
Post by: Scott C. Mitchell on February 10, 2014, 12:13:42 PM
How does one determine scale in an image like that?  How do you know if what you are looking at is 20 feet long or 2 feet long?  Maybe there's a formula based on field-of-view, focal plane of lens, assumed standardized depth, etc.  Otherwise you'd be like the poet William Blake, trying ". . . to see a World in a grain of sand. . . ".

Scott Mitchell
#3292
Title: Re: Grand Rapids trip
Post by: richie conroy on February 10, 2014, 12:17:52 PM
Tim

Only because rock formations replicate uncannily with Electra skin and structure, Don't mean it is actually part of the Electra for instance Pic 1 look were yellow arrow is pointing looks like a skull lying on it's right cheek and were observing the left cheek very life like.

Pic 2 what is the odd white ball object ? a bulb, a plant, a deep sea creature ?

The difference is i am saying what they resemble not what they actually are, For the sake of your own reputation even if you just explain why you believe it is part of the Electra, You are not exposing your self to abuse or insults, Not that you will recieve that here but in England you would be sent the mad house making claims like that  :)

Thank's Richie
Title: Re: Grand Rapids trip
Post by: JNev on February 10, 2014, 12:23:03 PM
How does one determine scale in an image like that?  How do you know if what you are looking at is 20 feet long or 2 feet long?  Maybe there's a formula based on field-of-view, focal plane of lens, assumed standardized depth, etc.  Otherwise you'd be like the poet William Blake, trying ". . . to see a World in a grain of sand. . . ".

Scott Mitchell
#3292

This has been an eternally infernal part of the problem for me (a minor part since I just don't see the same things as some others anyway).  Short of having a known object to scale by, I don't see how one can scale these.  Tim's 'fuselage' may only be inches long so far as I can tell.

Now someone could make the leap that they are scaling against a 'known' because they believe the SEE and KNOWN object - but that'a a bit boot-strapped to me.
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on February 10, 2014, 01:06:14 PM
The bulged deformation of the sheet might be explained, not by an unusual high-speed wave impacting a stationary aircraft on the reef, but by an aircraft impacting water at high speed, as in a crash or forced landing.  Ric or others might have some experience seeing the kind of damage caused by aircraft crashing into water and could advise us how the artifact differs in appearance.

I've never seen damage like that in a ditching or crash into water but I can image that it would be possible.  Just find an American airplane with .032 skin and #3 size rivets that ditched or crashed within a thousand miles of where the artifact was found.
Title: Re: Grand Rapids trip
Post by: Tim Mellon on February 10, 2014, 01:06:54 PM

This has been an eternally infernal part of the problem for me (a minor part since I just don't see the same things as some others anyway).  Short of having a known object to scale by, I don't see how one can scale these.  Tim's 'fuselage' may only be inches long so far as I can tell.



You can't judge scale, Jeff, because you don't have the tools at your disposal that I do. The subject is visible in both High Definition and Standard Definition videos (neither of which is yet available to you for this portion of the July 14, 2012 dive). While neither video has a built in scale, as such, the Standard Definition video does have a calibrated depth meter displayed (in feet and tenths). As the camera moves inexorably downhill, one quickly learns how to judge the change in depth relative to the passing scenery displayed. Since the slope approximates 45o, then a horizontal movement is essentially the same as a vertical movement, thus giving approximate scale in two dimensions (dividing by 1.414, of course).

In addition, the subject picture was captured from a much larger landscape, which contains other items related to the Electra (viz. engine components, a propeller blade, both pitot tubes, and possibly part of a wing). All these items seem to scale well against each other. Also, the 2012 High Definition video contains 1929x1080 pixels per frame, which my monitor and software can handle, but that may not be true for everyone.

You learn to live with the tools you have. Maybe next time Ric will demand to have parallel lasers pointing out from the ROV to create a meter-long scale between the two red dots cast onto the landscape.

Title: Re: Grand Rapids trip
Post by: Ric Gillespie on February 10, 2014, 01:16:27 PM
The difference is i am saying what they resemble not what they actually are, For the sake of your own reputation even if you just explain why you believe it is part of the Electra, You are not exposing your self to abuse or insults, Not that you will recieve that here but in England you would be sent the mad house making claims like that  :)

Not knowing whether Tim has any plans to travel to England, and rather than expose him to abuse or insults, we'll have no further discussion of what he thinks he sees in the underwater imagery.
Title: Re: Grand Rapids trip
Post by: richie conroy on February 10, 2014, 04:42:20 PM
Hi Ric

Fair enough if you think Tim's images do not further The search for Amelia, I was merely suggesting that he refrain from the IT IS, To Possible Candidate Or Maybe Resembles Even.

Thanks Richie
Title: Re: Grand Rapids trip
Post by: Ric Gillespie on February 10, 2014, 05:46:12 PM
Fair enough if you think Tim's images do not further The search for Amelia, I was merely suggesting that he refrain from the IT IS, To Possible Candidate Or Maybe Resembles Even.

For the record, I do not think that Tim's images, observations, comments, or lawsuit further the search for Amelia Earhart.
Title: Re: Grand Rapids trip
Post by: Monty Fowler on February 11, 2014, 07:05:54 AM
2014 is TIGHAR's year. Amelia and Fred deserve no less.

LTM,
Monty Fowler, TIGHAR No. 2189 CER
Title: Re: Grand Rapids trip
Post by: JNev on February 11, 2014, 03:42:13 PM
This is a question for Ric, Richie, and Jeff.....Let's say your leaving New Guinea...things are going great....and something breaks from being pulled from the tail of the plane...such as an antenna cable. My question is in the vintage WWII days, and in this case the Electra...Can an aircraft continue flying if part of the skin or plane comes loose due to some form of damage?

Sorry didn't catch this sooner -

Most likely yes, if we're talking about something on the order of an antenna mast being jerked loose, etc.  Most likely a skin wouldn't be torn loose, however, from impact or even tearing away of something like that, just bent and damaged and maybe a few fasteners strained or pulled loose.

In terms of what we see with 2-2-V-1 all kinds of things are possible - relatively minor damage to start with could have set it up for worse destruction later in surf or wind, etc.  It could have also made it a target for someone trying to harvest metal from a part of a hulk, etc.
Title: Re: Grand Rapids trip
Post by: Friend Weller on February 11, 2014, 05:14:11 PM
Sorry didn't catch this sooner -

Most likely yes, if we're talking about something on the order of an antenna mast being jerked loose, etc.  Most likely a skin wouldn't be torn loose, however, from impact or even tearing away of something like that, just bent and damaged and maybe a few fasteners strained or pulled loose.

In terms of what we see with 2-2-V-1 all kinds of things are possible - relatively minor damage to start with could have set it up for worse destruction later in surf or wind, etc.  It could have also made it a target for someone trying to harvest metal from a part of a hulk, etc.

This is what I was trying to express a week ago.....

After taking another look at the overlay photo of the artifact and the Harney drawings on the site, I noticed the proximity of the aft ventral antenna mast to the area of the the artifact.  If we accept the theory of the loss of the antenna upon takeoff from Lae, would it be reasonable to postulate that during the loss of the mast, the underside of the aircraft in the vicinity of the artifact may have been damaged just enough to crack stiffeners or pop rivets creating a weakened area?  This could have been either from the sudden forcing upward and aft of the mast upon contact with the ground surface while taxiing or the hammering of the underside of the aircraft as the mast bounced along during the takeoff roll prior to the antenna separating from the plane.  If enough rivets were popped from the deformation of the skin and stiffeners, this may have resulted in 20+ hours of "oil-canning" during the flight or perhaps severe weakening during the landing fatiguing the skin in that area making it easier for it to fracture/tear/pop when NR16020 went over the reef edge.

Friend

Maybe not loss of aluminum but a weakening of a portion of the skin due to damage incurred at the time of the loss of the antenna.

Friend
Title: Re: Grand Rapids trip
Post by: Greg Daspit on February 11, 2014, 06:26:14 PM
The artifact is a piece busted out of the middle of a panel. No manufactured edges on it. That suggests a focussed force where the edges held better than the middle. If the antenna mast was not on one of the torn edges, I don't see how its loss relates to the failure of the artifact.
(edit: though the antenna loss probably contributed to the string of events that led to its failure)
Title: Re: Grand Rapids trip
Post by: Friend Weller on February 11, 2014, 07:44:18 PM
(edit: though the antenna loss probably contributed to the string of events that led to its failure)

That's exactly what I was driving at.....the loss of the antenna was not necessarily the cause of the failure of 2-2-V-1 from it's parent panel but it is a piece of the puzzle (material, location, and causal forces) from which the artifact may have been created.

Like I said to Ric in an interview a few years ago:  We've got the smoke from the smoking gun....now to find that smoking gun!

Friend
Title: Re: Grand Rapids trip
Post by: Jerry Germann on February 11, 2014, 08:54:44 PM
http://i.imgur.com/iwjCU6r.jpg
http://i.imgur.com/cAdDuN4.jpg
http://i.imgur.com/OdDawew.jpg

A friend of mine sent me these ...the T-6 Texan used brazier rivets ( aft skin of fuselage) and 0.32 AL clad skin with 3/32nds and 5/32nds rivets ....so we found one example thus far of the 3/32ds / 5/32nds rivet use combination.
Title: Re: Grand Rapids trip
Post by: Martin X. Moleski, SJ on February 11, 2014, 09:47:43 PM
http://i.imgur.com/iwjCU6r.jpg (http://i.imgur.com/iwjCU6r.jpg)
http://i.imgur.com/cAdDuN4.jpg (http://i.imgur.com/cAdDuN4.jpg)
http://i.imgur.com/OdDawew.jpg (http://i.imgur.com/OdDawew.jpg)

A friend of mine sent me these ...the T-6 Texan used brazier rivets ( aft skin of fuselage) and 0.32 AL clad skin with 3/32nds and 5/32nds rivets ....so we found one example thus far of the 3/32ds / 5/32nds rivet use combination.

The third image says, "Aluminum sheets may be easily identified by the markings plainly stenciled in rows approximately 3 inches apart on each side of the material."  That means that the markings would be visible on the outside of the repaired area until they were removed--it appears that there was no unmarked side of the material.  For me, that dissolves all anxiety about how highly buffed the aircraft was.  There would be markings on the exterior to begin with. 
Title: Re: Grand Rapids trip
Post by: Jerry Germann on February 11, 2014, 10:27:31 PM

..which was consistent with standard Lockheed practice.  The attached photo shows an Electra being built with the labeling on the exterior side of the sheet.  Other manufacturers such as Boeing and Douglas seem to have put the label-side on the interior.  It may be that the presence of the labeling on the exterior side of the artifact is another indication that it came to Nikumaroro via Burbank.

I stand corrected as per the panel installation procedure per Lockheed , regarding which side the alclad stamping was on after attachment ....I made several references before as to what I thought was a backwards installation , however my thought was never corrected.

Consider the installment ....labeling stamp alclad was on exterior of sheet/


The third image says, "Aluminum sheets may be easily identified by the markings plainly stenciled in rows approximately 3 inches apart on each side of the material."  That means that the markings would be visible on the outside of the repaired area until they were removed--it appears that there was no unmarked side of the material.  For me, that dissolves all anxiety about how highly buffed the aircraft was.  There would be markings on the exterior to begin with.

Ric and I have sorted this out....al-clad was on the outside ....It is the quality of finished product that I muse about. It is my belief that all such exterior lettering was removed ( by solvent wipe) , my conclusion based on pre/ post luke field photos and reports by her regarding her plane's appearance. Yes, a spot might have been somewhat missed, people aren't perfect, but so far it seems to be found just on that one panel 2-2-V-1,  if more are found elsewhere , I will concede .....the tidy up crew....well,.... didn't.
Title: Re: Grand Rapids trip
Post by: John Ousterhout on February 12, 2014, 12:43:28 AM
I stopped by the airport today to take a closer look at a Beech B-18 (introduced in 1937).  Walking up to the nose I could see flush rivets everywhere, but the aft end and belly were covered with shallow-dome-headed rivets, some quite small.  The belly was especially interesting to me - the lines of rivets weren't all straight, giving the appearance of either a "saw horse" repair (wheels-up landing rash?), or intentionally jogging around some hidden feature, or perhaps it didn't matter much in that location?  I don't know the exact year of this particular example, but suspect it was built during the war.  I'll try to get photos next time I'm over there.
Please note that I'm not trying to imply that a B-18 was the source of 2-2-V-1.
The owner also owns a Lockheed model-12 that I am anxious to look at.  Can anyone comment on commonalities between the -12 and Amelia's -10?  Would there be anything useful to learn from studying a model -12?
Title: Re: Grand Rapids trip
Post by: Martin X. Moleski, SJ on February 12, 2014, 05:59:33 AM
It is my belief that all such exterior lettering was removed ( by solvent wipe) ...

There is no ink on 2-2-V-1.

The lettering is visible only under oblique angles. 

It would not show in pictures.

FWIW, if we're just matching creeds, I do not share your belief that your suppositions about how the piece would have been treated if it had been part of AE's Electra disqualify this from being a piece of AE's Electra.
Title: Re: Grand Rapids trip
Post by: JNev on February 12, 2014, 07:04:09 AM
I stopped by the airport today to take a closer look at a Beech B-18 (introduced in 1937).  Walking up to the nose I could see flush rivets everywhere, but the aft end and belly were covered with shallow-dome-headed rivets, some quite small.  The belly was especially interesting to me - the lines of rivets weren't all straight, giving the appearance of either a "saw horse" repair (wheels-up landing rash?), or intentionally jogging around some hidden feature, or perhaps it didn't matter much in that location?  I don't know the exact year of this particular example, but suspect it was built during the war.  I'll try to get photos next time I'm over there.
Please note that I'm not trying to imply that a B-18 was the source of 2-2-V-1.
The owner also owns a Lockheed model-12 that I am anxious to look at.  Can anyone comment on commonalities between the -12 and Amelia's -10?  Would there be anything useful to learn from studying a model -12?

I hope you can get access and learn and share all you can from this, what a great oppportunity.

The twin Beech is a near-contemporary to the Electra with somewhat similar construction (wonder where Beech got the idea...).  It also enjoyed an extremely long production run - from around the time you mention (1937) until about 1968 if my memory is good.  As such it was produced in many variant forms - and the flush riveting up forward may be a later effort that was not present on earlier models of the 18 (I do not know this - it can of course be found out). 

If this airplane is in service then it should have an external I.D. tag - left side of fuselage, somewhere aft of the door (and possible tucked under the horizontal stabilizer nearly out of sight to the casual observer if a restored warbird, etc.).  That would be the easiest way to get a full model and serial number so that vintage and other details can be determined.  That might tell something of how the flush rivets got there (likely production of course, but question being was it cut-in for a later variant, or has the twin Beech always had that feature - I don't recall it on our old C-45's in A&P school).

As to the irregular rivet patterns - I'm not surprised, there are all kinds of reasons for that to occur - but most of them would have to do with 'post production'.  As you mention, 'rash' from many things bring that about on many decades-old airplanes - and belly landings certainly occur, among other calamities (ask Ric, he's seen plenty of them as an investigator).  Something could be learned if the records are there: oddly enough, repairs and modifications in today's world (since Federal Aviation Act of 1958, and possibly earlier CAA records as well) go into a public folder - forms 337 document major repairs and alterations. 

Major alterations remain on record indefinitely ("forever") but major repairs may be dropped after one year - the presumption being that a proper repair 'restores' the airplane to an approved condition.  That's a tall assumption on FAA's part because there's a wiggly line in there - very often a literal wiggly line: original fastener patterns often are altered.  Not so bad - as long as pitch and size requirements are obeyed and within approved repair limits that's fine - but it can easily result in irregular lines as you see.

Of course an 'alteration' of some sort (a modification) can be the reason - but those are usually distinct, offset rows (and such could account for the offset we see in 2-2-V-1 compared to at least one museum bird.  If you are seeing somewhat erratic rows then the suggestion to me at this point is you are seeing field-replaced skins that were hand-drilled into repaired flanges on belly members or perhaps replacement stiffeners, etc.  It would not be the normal product of match-drilling to healthy, original stringers and stiffeners.

Interested in what you can learn from the L12, but it is a different (and smaller) airframe than the L10.  On the surface they bear a strong resemblance, but I think there are many nuanced changes within the scaled-down structure that probably prevent it from being a direct model for us to consider.  It is also a later model so some modernized features would be expected by comparison to the more antique L10.  For one, look at the gear - there was an obvious advance in technology on the L12 over the L10 - the double-fork welded assembly is replaced by a forged, single-offset leg at the wheel.

I hope you can meet the owner and get a tour and his interest in some of this - great source of information.
Title: Re: Grand Rapids trip
Post by: JNev on February 12, 2014, 08:18:37 AM
A couple of examples of what I take to be fairly early model Beech 18's (twin Beech) do show apparent flush riveting up front.  If I had ever noticed that before I'd forgotten it.  Leave it to Beech to drive (pardon pun) that kind of detail into something... especially something as blunt as their famous 'Bug Smasher': not sure how much benefit that really gave, what with rather blunt round engines, etc.

Title: Re: Grand Rapids trip
Post by: Jerry Germann on February 12, 2014, 12:16:42 PM
It is my belief that all such exterior lettering was removed ( by solvent wipe) ...

There is no ink on 2-2-V-1.

The lettering is visible only under oblique angles. 

It would not show in pictures.

FWIW, if we're just matching creeds, I do not share your belief that your suppositions about how the piece would have been treated if it had been part of AE's Electra disqualify this from being a piece of AE's Electra.


I haven't as yet ruled it out, I can only make assumptions based on the material that I can access here on this site ( which I find highly informative) and other internet sites,...nothing is certain. I am in a way testing the hypthesis, ...others may ask similar questions later on ( or have already in the past). For now, I observe what appears to be a detailed plane, pre and post Luke field,...post Luke repairs seem to indicate freshly painted leading wing edges, possibly the repainting of the numbering under the wings, and a seemingly highly burnished skin exterior, void of all factory ink markings, along with comments by earhart,.... some which give a gender attachment to it , which usually indicates a somewhat emotional attachment ......she refers to the plane as she/ her, etc ...