Half painted Fw 190 wing undersides - the purpose?

[Kari Lumppio]

Hello again!

This shall be my concluding post on this topic if nothing new surfaces.

The first thing I don't understand is how much time or raw material could be really saved by painting only half of the underside wing? Ailerons and flaps were painted as was the upperside. The downtime because of paint drying (hardening) is the same and painting the whole wing would have taken some 15 minutes more (my guess based on (little) experience).

Second thing I still don't understand is why no other type had this type of camouflage? For example ground angle of Ju 88 is more or less the same as Fw 190 judged from pictures.

Third thing I don't understand is that camouflage (glare prevention) would take preference over aircraft performance. No colour can prevent shadow etc. revealing the form of aircraft shape. Tarpaulins, camo nets, tree branches etc. would do that. I don't see surface colour as the only option of camouflaging an aircraft.



Smoothing the wing surface can reduce the profile drag coefficient to half*. Even if the wing profile drag is only a portion of total drag in the high-speed end (where induced drag decreases) this can make a real difference. I think any novice LW pilot would find use for extra 20-30 km/h (pure guess, someone with real numbers?) or so for the top-speed of their mounts.

Where my hypothesis in on weak ground is that on the underside there would be no need to smooth the surface further than some 10% from leading edge. The only other wing I know which also has this half-chord treatment is the P-51 Mustang. This was also the original trigger for thought together with the 119 D filler mentioned in the Fw 190 documents.

Surfacer - if used - would also be beneficial over the rivet lines on the leading edge (upperside). This is where the difference in smoothness would be really felt. The photos I have looked are not of such quality to see if the rivet heads are covered or not. The ones showing undersides clearly are usually crashed wrecks and panel lines on them are not 100% counter proof against surfacer use.

Surfacer (filler) does not have to be some thick stuff spread with spatula. There are very fast drying nitroputties which can (and could) be shot with sprayguns. I've been involved in couple of repainting projects of glassfiber wings (a glider and a motorplane (twice)) and do know what the sanding entails. I also know that with right tools the sanding can be done quickly and efficiently especially as on the metal wing there are no fiber reinforcements ("sand-throughs") to be worried about.



Thanks for the responses and would love to see more of them.

Regards to all,
Kari



* Ref: NACA report 667 "Determination fo the profile drag of an airplane in flight at high Reynolds numers" http://naca.larc.nasa.gov/reports/1939/naca-report-667/
Quote from the abstract: "... the surface irregularities on the original wing increased the profile-drag coefficient 50 percent above that of the smooth wing."

[Eric Larger]

Hello again again,

My point of view is strickly based on Focke Wulf Fw 190D and Ta 152 production , I do not know enough about other machines to pretend to be able to write something concistent about their painting scheme and to wonder about the reasons to apply such or such paints .

The camouflage study cannot be separated from the production of the machine itself , it is a part of the industrial process .

The ratio, between production time , amount of raw material, and lifetime of a machine has to be taken in account too .

German do not build machines to be used for years(or they will be dangerous with so much wooden parts on such basic airfields) , but for at least months , and more often for just hours .

The production situation

Some sentences extracted from an American report done in May 1945 and issued in September 1945 ,about Focke Wulf Bremen ...

" ...By 1945 , conditions became chaotic as a result of plant bombing, non-delivery of components parts and the collapse of the german transportation system. Production fell 66 percent , a denial of 795 aircraft, during the first three months and production virtually ceased by March , when only 30 aircraft were delivered . "

" However , the choice of final assembly and flight hangars as target was not as damaging to production as would have been the jig manufacturing plant at Gassen" .

So the terms are clearly established , the problem the german plant at Bremen had to cope with , are the components for the aircrafts , raw materials and their supply , the term of performance is far far behind .

Production of Fw 190D-9

Now back to Fw 190 . Focke Wulf , since 1943, try to simplify as far as possible the production of this machine , try to save as many raw materials as possible , and try to split the production into many small plants not easy to detect and destroy .

This of course produced a problem , the gathering of all components .

On the other way simplification , enables the production of components to be maintained at a certain level with less skilled workers .(to simplify)

Concerning FW 190D , this can be observed in the Ersartzteilliste istself , where optional parts are mentionned like :

Fuselage access door , 2 main variants one in metal one in wood , the same for radio access hatch, or flaps ....

We can divide the main airframe in 4 major components , all of them composed of several sub-components (I choose the one having an influence on camouflage )

1) engine : including engine cowling not produced by focke wulf and delivered painted
2 ) fuselage : windscreen and blown canoy often delivered perpainted
3) tail unit at least 5 sub components indentified , top of the fin (wood or metal) , rudder, extension part , tail
itself and horizontal stabilizators
4) wings at least 9 sub components , 2 wing tips , 2 flaps (wood or metal) , 2 landing gear doors (wood or
metal) , the wing themselves, and 2 ailerons .

All sub-components were probably delivered at the sub-assembles assembly location ( for exemple the 9 sub components for the wings) , still painted .

Focke Wulf issued also painting directives for Ta 152 A (abandonned) , that may have been used for Fw 190D-9 , where it is clearly mentionned that the undersurfaces should not be painted.

Camouflage is the visible result of all these simplifications and changes in the production process and of the supply problems

first effect

- the general painting process was revised , no putty , no primer , less paint

- on several wrecks recovered the camouflage paint was applied simply on bare alluminium (some produced at Fall 1944)
- No putty can be seen on FW 190D .
- Avoid to paint the surfaces that do not need to be painted ,undersurfaces and interiors (except cockpit)



As you said you need a certain skill to apply correctly and quickly fast putty on a wing, but on the other hand you do not need to have any skill to handle a spray-gun .

Second effect ,

the use of the advantage of having pre_painted components , for instance the engine cowling was often left in his delivery paint , we call it factory painting scheme (RLM83 or RLM71 and Rlm76) , or often the ailerons can be seen in one solid colour .

Third effect

The application of the "official" painting scheme produced by the manufacturer . Unpainted under surfaces , the scheme was revised ( for the reasons exposed in a previous post) , application of more defensive paints as RLM81 /RLM82 and RLM83 . The colour were probalbly not availabe at the same time explaining why some intermedaite painting scheme existed .

Other manufacturers and aircrafts

Why this scheme was not applied on other aircrafts is good question , but Me 262 and Bf 109 G-10 ot bf 109K-4 are known to have unpainted under surfaces . perhaps someone could explain it to us .


So it is clearly visible that the question of the performances and top speed was not to the first purpose , don't forget also that Fw 190D-9 was an intermediate solution , before producing in mass Ta 152. Would it be also important when in March- April 1945 the fighters were often used for ground attack ?

Camouflage do not take the advantage on performances , this took his place , in the industrial process of building a war machine , concidering the war and industrial situation.

German were not producing Formula 1 , they were producing consumable war machines in mass . This is not really the same production and purposes and also not he same workers required.

I may wish that other luftwaffe enthusiasts could discuss about other late war machines , it will be very interesting to read their conclusions or observations .

All the best

Eric Larger

[Dick Powers]

Eric,
I am presently working my way through your 190 book. It's very impressive. Thorough, well produced and a beautiful end product.

Throughout, your assumptions are given, some with sources, and conclusions stated along with qualifications. This book reinforces your statement that the camouflage and markings cannot be separated from the historical context.

One of the best books I've seen in a while. And I'm not even a modeler.

[CharlesMetz]

Originally Posted by Kari Lumppio

--snip--
Where my hypothesis in on weak ground is that on the underside there would be no need to smooth the surface further than some 10% from leading edge. The only other wing I know which also has this half-chord treatment is the P-51 Mustang.
--snip--

Kari,

One potentially relevant factor here is that the Mustang's wing was unusual in having a laminar-flow airfoil, the benefits of which were substantially reduced by any suface imperfections.

[Graham Boak]

Charles: the use of the term "laminar flow" for the Mustang wing has always been somewhat misleading. It did not create true laminarity - which would indeed be spoiled by the slightest imperfection. The term was applied to a family of aerofoils where the maximum thickness was moved from about 25% chord to about 40% chord. Even North American's high production standards and this section did not give laminarity beyond the 10% of chord quoted by Kari.

Eric: I think Kari's point is not why undersides and other parts were not painted. It is why the leading edges were. The only suggestion that makes sense to me is the aerodynamic one. I agree that the pressing need for aircraft- any aircraft - would eventually overrule even the most important aerodynamic principles, and that top speed was less important to a fighter-bomber. However, this makes the production line just one more enemy of the much-harried fighter pilot. The German aircraft at their best were equivalent to their Allied equivalents - a second-rate version was a death sentence. As we see in the casualty lists.

[Eric Larger]

Yes I undertand very well what do you mean , but again I am not sure that reaching the best performance was the highest priority.

Several machines , as you can see when reading for example J.Y Lorant 's book on JG300 , were produced but were not efficient war machines , tabs not tuned , undercarriages misfunctionning , engines overheating ....

The report written by Barhorn , when commanding JG6 , issued on 23 march 1945 , is very instructive on these points (from memory, problems with wooden landing gear covers , engines ...) .

So to conclude , of course this production and finition processes could have influence on the machine performances . And of course the fact of painting the leading hedge could have also an influence on airflow , but according to me the aerodynamic aspect is far from being the sole one to take in account .

Nice to read your point of view in anyway.

Eric Larger

[pstrany]

Keep in mind that a large percentage of the laborers that built these aircraft were slave labor. They were not inspired by patriotic ferver, but rather by the idea that if an aircraft did not roll out the door on a specific schedule, they could well be pulled out of the line and shot. Add to this that a lot of the laborers were foreign nationals who did shoddy work on purpose as a form of revolt against their taskmasters, and the poor quality of late-war German aircraft is hardly surprising.It is interesting that in the Fw 190, the front half of the underside of the wing was painted. in the Me 262, the entire underwing surface was left unpainted - which makes more sense. Certainly paint would have been at a premium in the closing days of the war, remembering that petroleum products go into paint manufacture. The quality of the paint used on the Me 262 was terrible. If you look at pictures of Wnr 500200, Black "X" of KG 51 after the war, where excess fuel had spilled down the fuselage it almost completely washed away all traces of paint (Classic Pub Me 262 Part 4, Pg 793 is clearest.) This was a not unusal pattern to see on Me 262 aircraft.The only suggestion I would have would either be a perceived aerodynamic advantage (helping to smooth the leading edge of the wing) or to make the absence of paint on undersurfaces less visible. To be added here is the fact that not just undersurfaces of the wings received this treatment, but also the undersurfaces of the fuselage in many cases as well. Going back to Black "X", the undersurfaces of the nose were painted (it was manufactured as a separate part) but the rest of the fuselage was not (per Green/Evans in Eagle Publications' "Stormbird Colors".)Paul

[cproyston]

I keep looking at the points raised in this discussion and can't help returning to the thought presented by the proposed OS-liste scheme (issued in Sept 1944) for the Bv 155 which states:

"...The fuselage sides, side of the vertical tail and leading edge of the wing and horizontal stabilizer should be painted in colour 76. Hereafter, except for the wing and horizontal stabilizer’s leading edge, the aircraft should be then in a cloudy overspray with colour tones 81 and 82. Also, we look ahead to simplify the paint schemes which we should know shortly and will publish. Afterwards, the above mentioned aircraft which will be used for day service, camouflage on the undersurfaces should be deleted..."

(Quoted from David E. Browns Excellent article, http://www.clubhyper.com/reference/luftcamdb_3.htm, published on Hyperscale.com)

The bold highlights are mine to emphasise my point - perhaps a similar order was issued for the Fw 190D?

Just my thoughts on the matter,

Chris

[Micke D]

I have found two photos, possibly three, that show that the upper wing was painted the same way, front part RLM76 or 75, and covered with a thin layer of camouflage paint on top of the wing.

It's shown in a photo, taken by Jerry Crandall? in the 60's, of the wing from Fw 190D-9, W.Nr. 601088, Black <1 + ~, Stab IV. /JG 51, in Eagle Editions about Fw 190D-13 Yellow 10. Most of the camouflage paint seems to have weathered away by then, leaving the RLM 76 that covers the front of the wing.

It's also shown on Fw 190D-9, W.Nr. 211939, Black 4 + -, 6. /JG 6, in "Focke-Wulf Fw 190D camouflage & markings Part 1" from JaPo. It's the photo that shows the repair/repaint of the left wingtip. The camouflage paint seems very thin and the RLM76 shows trough.

The third one is possibly Fw 190D-9, W.Nr. 400xxx, Yellow 11 + -, II. /JG 2 in Carl Hildebrandt's booklet Broken Eagles 1. This plane seems to have a broad dark coloured band under the camouflge paint, on top of the wing spar. But this could of course be paint, or putty, to cover the rivets on a repaired wing spar.

At the moment I can't say on which sides these photos are, as I'm at work.

/Micke D