Question: aluminum lacquer paint overcoat B-29s

[28ZComeback]

Hi everyone, 

 

A number of sources state that B-29's and B-50's were painted with an aluminum lacquer overcoat to protect the bare metal from corrosion.  Yet period pictures clearly show lack of uniformity in the surface color of these aircraft.  Was the overcoat largely translucent with some aluminum powder mixed in, or was it more opaque?  Many thanks for your response.

[Work In Progress]

That's basically what aluminium dope is: clear dope with finely ground auiminium powder stirred in. Every WW2 and early post war Allied maintenance facility would have it in stock for use on fabric covered control surfaces.

[tomprobert]

I suspect this may have been the central spar box. 

 

This area is a noticeably different shade and appears darker than the surrounding natural metal and untreated areas. An early form or corruguard, perhaps. 

[old thumper]

7 minutes ago, tomprobert said:

I suspect this may have been the central spar box. 

 

This area is a noticeably different shade and appears darker than the surrounding natural metal and untreated areas. An early form or corruguard, perhaps. 

 

This area does look to be as you say in most of the pictures which I have seen, as do the engine cowlings.

Additionally the rudder was fabric covered and appears to be a much different colour to the rest of the aircraft, suggesting the rest of the aircraft was not painted.

I'm not an expert in the B-29 but just by coincidence i am currently doing research for an Airfix Eddie Allen build. 

[Chuck1945]

WWII era B-29s were just natural metal. Don't know about post-war.

[Don149]

Post war B 29s in RAF service were aluminium painted . I have two pics of one which staged

through Malta in early 54 .It must have been an early production ex USAAF as it had all the

turrets and black de icer boots on all the leading edges , if this is of any interest .

[72modeler]

21 hours ago, tomprobert said:

I suspect this may have been the central spar box. 

 

This area is a noticeably different shade and appears darker than the surrounding natural metal and untreated areas. An early form or corruguard, perhaps. 

IIRC, I seem to recall reading an article by Dana Bell regarding this, as well as some other written references, which I can't remember at the moment. I think the upper wing spar coverings on the B-29 were not alclad, but anodized aluminum that was painted with zinc chromate primer and then aluminum paint, which gives that area a noticeably darker and duller finish than the surrounding metal panels. You can really see this in photos of factory fresh B-29's. Hopefully Dana will log on and either confirm or document my ignorance/bad memory! I have attached a link to a photo that shows this finish pretty well- note that the anodized area includes the fuselage center section stub, which was built integral with the fuselage and to which the wings were attached; I think this method of attachment was altered during production so that B-29A's had a slightly different wingspan than earlier examples...have to check my William Wolf B-29 book on that one, so don't quote me just yet!.

Mike

 

https://s-media-cache-ak0.pinimg.com/736x/3d/38/9a/3d389ab7be00b78c271b9b4112ebec82.jpg

 

 

[Graham Boak]

As I recall, the aircraft with the slightly larger wingspan were those built by Bell.  I don't think that this method was adopted by Boeing for later B-29 and B-50 production.

[Dana Bell]

Hi all,

 

Sorry I haven't been logging in as often as usual - busy days at the archives and all.  As was noted in one of the posts above, most of the aircraft was skinned in Alclad, an Alcoa proprietary name for aluminum alloy sheet coated with a thin layer of nearly pure aluminum.  While the pure aluminum coating added the best available corrosion control, it lowered the overall strength of the sheet when compared to a 100% alloy sheet of the same thickness.  It wasn't much of a problem on most areas of the aircraft, but the extra strength was needed on the central wing box, which was then primed and painted with aluminized lacquer to add corrosion protection.

 

Of course, this was not an issue on early B-29s that had been camouflaged, and there are photos of at least one aluminum B-29 (serial unknown) rolling out of the factory with vertical tail, rudder, stabilizers, and outer wing panels still in OD/gray camouflage.

 

In short, for any aluminum-finish B-29, photos should show the slightly different tone and reflectance of paint on the central wing box.

 

Cheers,

 

 

Dana

[72modeler]

I just now found a B-29 website that I think some of you might find useful or informative; many of the photos show the center wing spar areas very well. Enjoy!

Mike

 

http://www.b29-superfortress.com/b29-superfortress-production-assembly-plants.htm

 

Graham,

If you go to the website and click on the developments and models tab, you can read about the B-29A and its different wingspan. How are you doing? ( I sure have learned a lot from reading your posts, by the way!)

Mike

Edited February 23, 2017 by 72modeler
added comment

[KRK4m]

On 22.02.2017 at 5:05 PM, Graham Boak said:

As I recall, the aircraft with the slightly larger wingspan were those built by Bell.  I don't think that this method was adopted by Boeing for later B-29 and B-50 production.

 

IIRC the Bell machines (B-29B) were deprived of all four gun turrets above and under fuselage while retaining the original B-29 four-piece wing. Those with different wing construction (B-29A) were built solely by Boeing Renton plant.

Boeing has claimed this modified five-part wing the "big step ahead" for improving the B-29 serviceability and simplifying the production process. I'm still not sure, whether this B-29A wing featured longer span (Joe Baugher says, that - contrary to popular belief - the total span was identical).

Another question is whether the main Boeing Seattle plant adopted this "better" method of wing assembly for their B-50 and C-97 (>1300 built) or did they retain the original Wichita (ex-Stearman)-built B-29 layout. The clou is that the sole XB-44 started her life as B-29A while the span of B-50/C-97 is always given the same as the original B-29...

However it appears clear that Soviet-built Tu-4 reverse-engineered Superfortress-clone followed the original pattern, as all three "pattern" aircraft the Russians intercepted belonged to the early B-29-5BW and B-29-15BW batches, while the fourth one (incidentally the B-29A) has been totally destroyed when hitting the mountains after the USAAF crew had bailed out. 

BTW Academy 1/72 kits of B-29 (#2111, 2113, 2154, 2173, 12413 and 12528) and B-29A (#12517) feature exactly the same wings. Do they follow original B-29 panelling or the modified B-29A one? Does anybody know? I don't...

Cheers

Michael