Enola Gay Question

[Kyleb]

I visited Udvar Hazy a week ago and was surprised that what I'll call the top of the wing box structure and the top of the fuselage that spans the wings was painted grey as opposed to the rest of the aircraft which is in polished aluminum. Is that normal? I've never noticed that before on any of the B-29's I've seen.

[Thomas_Mac]

Was it like Doc? I've also always been curious why its like that.

Boeing B-29 Superfortress ‘469972’ “Doc” (N69972) by Alan Wilson, on Flickr

[Kyleb]

The fuselage did look like Doc. The paint on the wings was much more obvious than on Doc. Anyone know why that area is painted/primed?

[Matt Gunsch]

it is a different alloy of Aluminum, you will see panels of various shades on bare metal planes

[Kyleb]

it is a different alloy of Aluminum, you will see panels of various shades on bare metal planes

Is it a different alloy or a different alloy that has been painted (possibly for corrosion resistance)?

[Edward Sheetmetalhands]

[quote="Thomas_Mac"]Was it like Doc? I've also always been curious why its like that.

The main wing skins (with the exception of the trailing edge above the flaps) on B-29 Doc were already painted silver when it arrived in Wichita after its long desert storage. Whether that happened at the factory or as a T.O. while still in service I cannot say for sure. It is my opinion that was done during the original build.

B-29 Doc arrived with unpainted, polished Alclad skins at the outboard side of the outboard wing panels (the outboard wing panels are not part of the main wing, and are roughly the last 26 feet of wing), just like the common B-29 publicity photos taken when new. So, on a stock B-29 you will see Alclad main wing trailing edges, painted main wing skins above the fuel cells (in between the forward and aft spars). And a mixture of both on the outboard wings. The heavier outboard wing skins that have the 82 degree countersink angle are painted, and the furthest outboard skin that are thinner and utilized a 100 degree countersink angle was Alclad.

They painted those few Alclad skins during restoration probably for maintenance and durability.

If the main wing skins are not painted, there are fuel cells underneath each one, and any rain seeping past rivets will collect and be trapped in the fuel cell compartments. Keep in mind, too, that the wing does not shed rain water as quickly as the fuselage does.

The B-29 was not a completely bare airplane, it just seemed that way. Inside of the main wing amongst the fuel cells was zinc chromate primer. Inside of the outboard wings the spars and stringers got painted gray lacquer, with the trailing edge formers were bare. The horizontal stabilizer was similar with the gray lacquer on the spars and stringers (the most important parts).

[JohnB]

Edward SMH...

Was there a difference in the paint/finish between the B-29 and B-29A (due to their wing structure differences)?

[Edward Sheetmetalhands]

Edward SMH...

Was there a difference in the paint/finish between the B-29 and B-29A (due to their wing structure differences)?

Paints and finishes for each part are called out on the engineering drawings. The same goes for whether engineering wanted that particular sheet to be Alclad or bare. Some of the planning documents (Parts LIsts) would have four vertical columns; one each for the 4 B-29 plants. Renton, Wichita, Atlanta, and Omaha. Then a box would be checked if that assembly or part was effective for say a Wichita built B-29. The Renton B-29's were a completely different animal in terms of how you go about the whole wing to body attachment. I read that there was little difference in how they flew. Post war, the Renton design won out, and the Wichita method became an evolutionary dead end. The Renton design was different because their factory building was different (because it was originally intended to build flying boats). They did not want to do the main wing drop into the body using the overhead crane.

If you go down the rabbit hole of trying to find specific information in a drawing set it can be hard because the microfiche was done out of order. The ones I worked from, they must have thrown all the different drawings in a pile and then copied them in whatever order. So you can search a very long time; even though you know what you want. Luckily, we had people that specialized in that.

Last edited by Edward Sheetmetalhands on Sun Oct 13, 2024 12:40 am, edited 2 times in total.

[JohnB]

I think I answered my own question...
I checked the serial of the AC above: 42-24812...
and it is a B-29-50 BW, not a B-29A.

With its different wing box, the Renton built B-29As may not have had that panel color differential.

[JohnH]

Great timing on this post, I had not noticed this on Doc before and was looking at it the grey part the same day of this post at Miramar.