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[Jeff Victor Hayden]

Here's some 24ST ALCLAD as it was called then or, 2024 ALCLAD as it is called now after 75 years submerged in sea water. Not all samples in the picture are aluminium but, they are all from an aircraft wreck. There are parts from the piston cylinders and some aircraft skin, steel rods and, aluminium instrument panel segment etc..

"The seven samples had been immersed in seawater for approximately 70 years and had a thick layer of calcareous material and barnacles attached to the surface. The calcareous deposits were very brittle, but strongly adhered to the surface. Barnacles attach themselves to surfaces by a cementitious secretion of insoluble polyphenolic protein complex, which acts as an excellent underwater adhesive. The combination of calcareous deposits and barnacle glue was difficult to remove and had to be subjected to a shearing force in order to disrupt the bond with the metal surface. A pneumatic scribe was used to dislodge the cementitious layers. Shear forces cause the thick layers to loosen their grip on the metal surface. The thick layer can then be chipped off easily."

The samples were recovered, restored and preserved and then photographed. Recognise anything that resembles aircraft? Neither do I. The rest of the wreckage is still submerged in seawater, only the engines and landing gear give you a clue as to what it used to be.
75 years actual.

[Ric Gillespie]

only the engines and landing gear give you a clue as to what it used to be.

Yep.  That may be what we're up against.  The degree to which 24ST corrodes underwater seems to be highly variable with location.  In general, the closer to civilization the site is, the greater the corrosion.  May have something to do with pollution in the seawater.

[Andrew M McKenna]

Ric Says

•  Glickman's landing gear debris field at about 61 meters (200 feet). Still plenty of ambient light and marine growth at that depth.

I think that is an overly optimistic assessment.

From Wikipedia

<<<<<<<
With increasing depth underwater, sunlight is absorbed, and the amount of visible light diminishes. Because absorption is greater for long wavelengths (red end of the visible spectrum) than for short wavelengths (blue end of the visible spectrum), the colour spectrum is rapidly altered with increasing depth. White objects at the surface appear bluish underwater, and red objects appear dark, even black. Although light penetration will be less if water is turbid, in the very clear water of the open ocean less than 25% of the surface light reaches a depth of 10 m (33 feet). At 100 m (330 ft) the light present from the sun is normally about 0.5% of that at the surface.
The euphotic depth is the depth at which light intensity falls to 1% of the value at the surface. This depth is dependent upon water clarity, being only a few metres underwater in a turbid estuary, but may reach up to 200 metres in the open ocean. At the euphotic depth, plants (such as phytoplankton) have no net energy gain from photosynthesis and thus cannot grow.
>>>>>

I also found this description that matches pretty well

<<<<<<<
At 300 ft (90 m), most of even the blue light (the most penetrating) has been absorbed, while below 650 ft (200 m), the only light comes from bioluminescent organisms, which produce their own light.

http://oceana.org/es/explore/marine-science/light-and-sound
>>>>>>

I would not expect much marine growth on an object that landed at 200 ft given the minimal amount of light down there. I haven't been able to find a formula, but clearly the light attenuates at an exponential rate.

Andrew

[Jeff Victor Hayden]

Whatever wreckage is down there started at the surface and progressively, over a number of decades, made its way to where it is today? So it has been subject to various levels of light penetration and marine growth over the decades?

[Chuck Lynch]

Well, something's down there, and it must be found and explored.

Let's cross our fingers this is it!

[Ric Gillespie]

Whatever wreckage is down there started at the surface and progressively, over a number of decades, made its way to where it is today? So it has been subject to various levels of light penetration and marine growth over the decades?

Maybe.  Of maybe it's right where it came rest in 1937.  How would we know?

[Jeff Victor Hayden]

Whatever wreckage is down there started at the surface and progressively, over a number of decades, made its way to where it is today? So it has been subject to various levels of light penetration and marine growth over the decades?

Maybe.  Of maybe it's right where it came rest in 1937.  How would we know?

We wouldn't know. If it is where it came to rest in 1937 then it will have saved itself 75 years of damage getting to where it is now and, could quite possibly be in better shape than we could hope for. Fingers crossed its like the lagoon wrecks we see so much of, although the side of a seamount looks a little more hostile. Be great if it is recognisable but, so far nothing has shown up as such on video, images or sonar.

[Ric Gillespie]

Be great if it is recognisable but, so far nothing has shown up as such on video, images or sonar.

True, but remember that the area covered by ROV video - 2010 and 2012 combined - is a tiny fraction of the logical search area and the side-scan sonar was demonstrated to be capable of totally missing objects much larger than a fully intact Electra.

[Jeff Victor Hayden]

Agreed, much experience of high tech gizmos not doing as specified and, you can't beat the good old eyes on approach to getting things done.

Example:

Bowman is the name of the tactical communications system used by the British Armed Forces.
The Bowman C4I system consists of a range of HF radio, VHF radio and UHF radio sets designed to provide secure integrated voice, data services to dismounted soldiers, individual vehicles and command HQs up to Division level.

Which when translated in the field became...

When Bowman was first introduced into service, the system was said to contain many faults to the extent that troops dubbed Bowman "Better Off With Map And Nokia".

They'll get it to work someday, in the meantime the carrier pigeons jobs are still safe 

[richie conroy]

Sure i posted on this a few minutes ago ?

quote: True, but remember that the area covered by ROV video - 2010 and 2012 combined - is a tiny fraction of the logical search area and the side-scan sonar was demonstrated to be capable of totally missing objects much larger than a fully intact Electra

Ric

Why did neither the 2010 or 2012 search Rov go straight to logical search area ?.

Just asking out of curiosity really ? 

[Ric Gillespie]

Why did neither the 2010 or 2012 search Rov go straight to logical search area ?.

They did, but in 2010 the long (300 meter) tether failed after just a few dives and subsequent dives were limited to 150 meters untlil the last week when a new long cable arrived, but then the cable for the navigation system got fouled in the ship's propeller so there was no record of exactly where the ROV was during its dives.  The infamous "wire & rope" video was shot without the benefit of nav info so we only know where the ROV was in a general sense.

In 2012 we started in the logical search area but soon got sidetracked chasing "promising" targets that turned up in the sidescan data collected by the AUV.  Between checking out sidescan targets and rescuing the SUV we reurned to "mowing the lawn" in the logical search area, but we ran out of time before we had covered any more than a small fraction.

[Monty Fowler]

[... but we ran out of time before we had covered any more than a small fraction.

And some of the time crunch, if I remember correctly, was due to mechanical/operational issues with the high-tech search wizzardry. Nikumaroro is a harsh taskmaster, and likes to deliver its lessons in a brutally direct fashion. I'm glad to see we're going to try and raise the money for a 30-day expedition - things are going to go wrong, just as sure as we're breathing, and that gives us somewhat of a cushion to search the maximum possible underwater area.

77 years is long enough to wait. Amelia and Fred deserve that.

LTM, who will be sending another check soon,
Monty Fowler, TIGHAR No. 2189 CER

[Ted G Campbell]

Ric,
Would you give us an idea of the amount of contributions each of us would need to pledge to make the next year program a go.

Ted Campbell

[Scott C. Mitchell]

It would be grand if the sea search mission of Niku VIII could be matched with a land search mission.  You have addressed this before, pointing out that there is limited space aboard the KOK, and the KOK is not designed as a shore-support vessel.  Yet a land party could work with a fraction of the hardware of the sea party, and could be funded by an incremental amount.  If a second vessel was necessary for the land party, it would not have to have the sophistication of the KOK.  Circumstances might develop where a second vessel might have a role to play in the sea search.  AE and FN had days to roam around the island, looking for sustenance, in between radio broadcasts.  Other castaways have tried to somehow leave a record of their plight.  Especially since they spent days flinging their distress calls to an unhearing world, AE and FN may have wanted to leave a testament to their fate.  Who knows what might be in plain sight in the deep bush of Niku? Having a land mission would also be a way to cover our bets for the limited targets of the sea search.  From your archaeology field courses, I bet you would have a pool of qualified volunteers.

Scott Mitchell
TIGHAR #3292

[Greg Daspit]

sea and land search link