Half painted Fw 190 wing undersides - the purpose?
 

Hello!

I'm wondering about the Fw 190 wing undersides where the leading edge was painted with some colour (grey or light blue) when the rest was left unpainted. Period of time latter half of 1944 and on.

The books I have read explain the thing as camouflage against low flying strafers. Can't help myself of the nagging thought that Luftwaffe was at the time abandoning the underside camouflage alltogether. Why there suddenly arose a new need for underside camouflage at that same point of time? Plus one doesn't see the half-painted wing undersides on other LW a/c types (or any other Air Force of any period for that matter).

Related question: what colour is the Warnecke & Böhm filler 119 D? It is somehow related to the unpainted Fw 190 wing undersides.

It is this filler thing which makes me to propose another hypothesis. What if the half-painted area is actually area aerodynamically smoothed with filler? Germans were still in 1944 trying to make the most out of their planes. Why not copy the P-51 Mustang wing surface finish (= wing forward half smoothed with filler)? The smoothing of Fw 190 wing leading edge would make at least some aerodynamic sense as it did not have slats like Bf 109 (disruption at slat trailing edge makes the flow turbulent no matter what). IIRC Hoerner in his aerodynamics book (title escapes my mind now) complained about the uneven finish of German planes (Bf 109) and the resulting drag and drop in performance.

The proof would lie in finding if the Fw 190 wing upperside has the same paint/filler as the leading 50% of the underside of "unpainted" wings.

So there. Antitheses, other hypotheses and especially syntheses welcomed.


Regards to every researcher on this field,
Kari

Re: Half painted Fw 190 wing undersides - the purpose?
 

Hello Kari,
One reason may be that at that late stage of the war it was more important to save time and resources. It was probably thought that it was more importent that the aircraft be better camouflaged on the ground than in the air. Filling and rubbing back imperfections is a very time consuming job and would add greatly to construction time.
Kindest regards,
Don.

Re: Half painted Fw 190 wing undersides - the purpose?
 

I would go with your hypothesis that the metal surfaces were becoming so poor that a coat of paint (perhaps with filler, perhaps not) was put over the leading edge of the wing to smooth the airflow over that part of the wing.

The Me 262 also got that treatment, ie. some paint on the leading edge of the wing, but with most of the underwing left unpainted.

Interestingly enough, in a report comparing wing structures on Allied and German a/c, the leading edge slats on the 109 were criticized, as were the larger rivets on German a/c. They needed more effort to insert, and caused surface buckling.

Re: Half painted Fw 190 wing undersides - the purpose?
 

Hello all of you

The purpose of half-painted undersurfaces is twice , save material and save time during the production process . This is clearly explained in our book dedicated to Fw 190Ds camouflages and markings .

On summer 1944 , Focke Wulf did test on 50 production machines (Fw 190A ) to test the efficency of this process at Sorau .

If the purpose is clear the reasons of this process are clear also .

First there was no need at that time to hide aircraft viewed from ground , as for several months the Luftwaffe turned to defensive actions , so underwing painting was not a priority .

Seconds the breakdown of the communications ( this was the major effect of strategic bombing , ie Allied reports in summer 1945 ) make supply in raw material more difficult , so anything that could be save had to be saved . For instance , you can ee several wodden part in the list of pieces of FW 190D-9.

Thirds the lifetime of a fighter at the end of the war was very short , please have a look to J.Y.Lorant & R.Goyat book dedicated to JG300(volume II) , and you will have several examples when pilots bailed out their machines and picked up very soon brand new ones. They were consumables .

I have several pictoral examples of rows of wings of Fw 190D-9 , waiting their assembly at Fiersler Kassel , half painted .

Now the question concerning the leading hedge . It was painted , two purposes , thirst protection of the metal , Seconds(just a guess for Fw 190) is try to limit the reflexion of the light when seen from the air . Do not forget that several Fw 190 at the end of the war had their landing gear covers oversrpayed with camouflage paint (they can be see from the air as they are not hidden with the wing completelly) .

Last point the colour applied on leading hedge , for us it is the colour avaliable , RLm 76 , Blue-Green , RLM 75 . Dont forget that RLM 75 was abandonned early on production batches (Nov 1944) and should be available in quantity .

All the best

Eric Larger

Re: Half painted Fw 190 wing undersides - the purpose?
 

Seconds(just a guess for Fw 190) is try to limit the reflexion of the light when seen from the air .

This purpose is described in Ken Merrick´s book volume one. There is mention that during testing of unpainted wings there was a strong reflexion on the parked aircraft so the area around leading edge and wheel covers were painted to reduce it.

Re: Half painted Fw 190 wing undersides - the purpose?
 

Hello all!

I do have the Merrick opus, but didn't have noticed his explanation for the half-painted undersides (found in the photo caption on p. 103 and in text on p. 104).

But quoting the very same Merrick book:

(of the first 50 Fw 190 with unpainted undersides, page 102)
"... only the primer filler has to be applied on the bare sheet metal ... the deletion of camouflage paint has to be particularily noted."

(the first communication letter dated 4.7.44 - "Fw 190 abolition of camouflage paint on the aircraft underside", page 102):
"... For the priming of bare sheet metal we have considered the putty 119 D from the Warnecke & Böhm company, which we ordered on 16.7.44 by telex..."

(the second document on page 103):
"...Therefore it is not necessary to obtain special paints for this large-scale test other than the already quoted putty 119 D from the Warnecke & Böhm company"


I think we can all agree that filler/putty/primer 119 D was indeed used on the mentioned Fw 190 with unpainted undersides. Question is where and why?

If the deletion of camouflage was done because of saving raw material and time it makes no sense to putty the airframe only for cosmetic reasons. My guess is that the filler was used to make the airframes smoother and more aerodynamic.

On single-engined planes with tractor propeller the whole fuselage is in turbulent flow. Would puttying the fuselage seams bring any noticeable effect? I do not know for sure, but my guess is the effect would be neglible.

Making the wing leading edge smoother (especially on the 1/3 - 1/2 chord on upperside) would instead make a noticeable difference if the starting point was far from perfect.

This is my reasoning for suggesting the half-painted wing could be result of using putty surfacer.

Many authors also write about Fw 190 having upperside camouflage of consisting of some light grey primer (sometimes identified as RLM 77) and green/grey paint. Like mr. Hopp already wrote also Me 262 used primer. This type had podded engines (= fuselage in smooth airflow) and the fuselage seams were puttied and taped over to make it more aerodynamic (on NASM "Yellow 7" the primer on fuselage sides has been identified as Munsell 10 Y 7/1 - I don't have any FS for it). Was this finish on Me 262 waste of time and material? Why would it be that on making Fw 190 perform better?


For me this is all about getting an explanation which makes sense. I can't help myself thinking that the current explanations for the half-painted wing undersides (=special camouflage on wing undersides which are supposed to be uncamouflaged) are a bit exotic. I really hope that I am not getting anyone angry and apologize if this is the case.


With Respect,
Kari

Re: Half painted Fw 190 wing undersides - the purpose?
 

Hello

first do not forget that these documents are attached to tests done in summer 1944.

Effectively if putty is used to smooth the under surface , it has also a function of protection . This putty was probably useed to seam the panel lines and to avoid anything (mud, oil, dirt...) to come into the space left between two aluminium panels. I think that first they tried to test if undersurfaces puttied can resist to airflow . This , in anyway, save material as no paint was applied over . And it saved a lot of time .

Now the reality and the use at a large production scale is different . Please look carefully to several pictures of Fw 190D-9 , this is the example I know the best , and look carefully at the state of the surfaces (fuselage , wings , tail) , you can notice that on any of these surfaces , no putty was applied to seam panel lines or to cover rivets . So the request in the test of using putty was abandonned .

At that time , as I said previously , there was no need to do it , due to the very short lifetime of an aircraft . The term of performances should not be taken in account , the purpose was to produce as fast as possible war machines .

Now concidering the used of light paint on upper surfaces . We think that the undersurfaces paint (RLm76, Green-blue, or RLM75 ) was also applied on uppersurfaces , on some pruction batches .This paint could also act as a primer on upper surfaces ( the most important surface to hide the aircraft from the air ) and then a full or partial camouflage scheme (RLM82 , 81 , 83 or rlm75 ) was applied producing examples well identified like RLM 76/83(W.nr 211939) , or RLM 75/83 (210051), or RLM82/83 (210102).

The some paint can be applied at unit level to cover repairs , the best example is W.Nr 211934 ( initial painting scheme W2 undersurfaces (metal + rlm76), RLM83/82 uppersurfaces .One wing has repainted undersurfaces (starboard wing ) with rlm76 (balkenkreuz area) and uppersurfaces (same wing) with RLM75 see pages 160 to 164.

This is just guess as no document so far (known to me ) has been found to confirm this .

On the other hand RLm 76 or RLm75 can be used on the undersurfaces to mask some minor repairs see page 40 (photo in the middle) of our book it is clearly visible .

We do not think that RLm77 was used but more probably a new variant of RLM76 called 'Weissblau" , containing less cobalt blue pigments .

hope that helps

Eric Larger

Re: Half painted Fw 190 wing undersides - the purpose?
 

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."

Re: Half painted Fw 190 wing undersides - the purpose?
 

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

Re: Half painted Fw 190 wing undersides - the purpose?
 

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.

Re: Half painted Fw 190 wing undersides - the purpose?
 

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.

Re: Half painted Fw 190 wing undersides - the purpose?
 

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.

Re: Half painted Fw 190 wing undersides - the purpose?
 

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

Re: Half painted Fw 190 wing undersides - the purpose?
 

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

Re: Half painted Fw 190 wing undersides - the purpose?
 

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

Re: Half painted Fw 190 wing undersides - the purpose?
 

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

Re: Half painted Fw 190 wing undersides - the purpose?
 

Interesting discussion!

I say I have to agree with the aerodynamic reasons for the leaving the leading edge bare.

Painting an aircraft is essentially a bad thing aerodynamically. It adds significant weight and additional surface imperfections that can rob performance.

In our restoration of White 1, we are using actual RLM paints. It takes just as much skill to paint an aircraft as it does to paint a car. The RLM paints are very sensitive to reducer ratios. Little too much or too little and the paint does not apply. It takes skill to prepare the aircraft, operate the equipment, and apply the paint. Granted these factories were not trying to turn our show quality finishes. Nevertheless it takes training to apply the paint.

"Surfacing" or "filled and polished" on the other hand can range from simple laborer work to being just as complicated as applying the paint. Depending on the method used of course.

So I would think it is rather a mute issue on the skilled labor.

By not painting these surfaces several things appear to be accomplished:

1. Aerodynamics is improved
2. Production times and cost is reduced

You guys should come check out the Museum and the Restoration.

http://www.white1foundation.org/parts/shop1.jpg

http://www.white1foundation.org/index.htm

All the best,

Crumpp

Re: Half painted Fw 190 wing undersides - the purpose?
 

Actually, when properly done, painting improves aerodynamics, as all the imperfections are covered by a layer of paint. Painted and polished aircraft will have a better aerodynamics than a bare metal one.

Re: Half painted Fw 190 wing undersides - the purpose?
 

Sure I will buy that for the first couple of hours of flight.

When the paint cracks, scratches or chips from aeroelasticity though you will lose performance.

Remember too, using the Oberflächenschutzliste 8 Os 155:


It is very doubtful bare metal would have just been left in a rough surface.

Re: Half painted Fw 190 wing undersides - the purpose?
 

If I may drop back to an earlier point that wasn't addressed.

It is important to add filler to gaps along the fuselage. Every gap and step will add drag, regardless of whether the flow is laminar or turbulent. The thicker the boundary layer, the smaller the penalty, but penalty remains.

Re: Half painted Fw 190 wing undersides - the purpose?
 

Well, this couple means some months, depending on groundcrew of course, and it was longer than an ordinary period of service in a combat unit.
This was because of specifics of new camouflage coat, extremally thin. Puttied, painted and polished aircraft will always have better aerodynamics rather than the bare metal one.

Re: Half painted Fw 190 wing undersides - the purpose?
 

But didn't the U.S. stop painting their planes because they got better range and better max speed than the previously painted ones?

Imho Germans simply lack of paint in the last months of the war (dont forget that you need petrol derivatives to thin the paint) but contrary to the U.S. they absolutely need to keep their camo not to be destroyed in the minutes with all those ennemy airplanes over their heads...

Re: Half painted Fw 190 wing undersides - the purpose?
 

Hi Oliver:

IIRC, the US decision to drop painting was based on a significant manpower savings during production combined with the fact they no longer needed the camouflage when on the ground. Also, the P-51 did have painted wings. Most NM aircraft had clear protective coating, so there was some smoothness there. I do not recall the exact amount but the paint on a B-17 weighed in the 300 pound range, so that helped as well. Lastly, some units made the decision to paint their NM machines, notably the 55th, 56th, and 357th Fighter Groups. Some 9th AF units did, but strangely, in view of their nearness to German lines, most kept their NM finishes.

Re: Half painted Fw 190 wing undersides - the purpose?
 

No, it was only to speed up production.

Re: Half painted Fw 190 wing undersides - the purpose?
 

Actually according to sources at the USAF Museum at Wright Patterson it was due to performance. This is also backed up by the experience we have in using original finishes.

The paints used by the USAAF in WWII were all contracted from the same company out of California. Proper application took at least one coat of primer, 2-3 coats of paint, and clear coat. This adds almost 200 lbs to the weight of a P51D fighter. Using the original paints, in just 2 hours in the air, the paint begins to crack and chip. Faster if the aircraft is maneuvered hard. This adds drag and degrades performance. Both shedding weight and reducing drag improve an aircraft.

These T6 Texans are painted with WWII USAAF paints and the B17 had the late war USAAF finish:

http://theotherorlando.com/contents/...ingtigers.html

http://www.warbirdmuseum.com/

Now the RLM finishes are slightly different. The granulation is much smaller than what was produced in the US. In fact, the finishes seen on modern USAF fighters are a direct descendant of the RLM paints according to the USAF Museum at Wright Patterson, AFB Ohio.

This can be seen immediately on any actual RLM finish.

These drop tanks and many of our skins still have original RLM paints applied:

http://www.white1foundation.org/parts/droptank.jpg

Here is a close up of an original leading edge:

http://www.white1foundation.org/parts/leadingedge2.jpg

Our pilots chair has a new coat of original RLM paint:

http://www.white1foundation.org/parts/pilotseat2.jpg

If you look closely you will see paint is not "chipped" but rather worn. This is typical of the RLM finishes we find. The paint is chalky and while it does wear the edges tend to feather or smooth as opposed to being as thick and sharp as the US paints. The RLM finishes cover in one coat as well. When mixed correctly there is no tendency to fisheye, orange peel, or run. One coat of primer, one coat of paint, and one of sealer is all that is normally required. This means the finish is lighter. About 60 lbs for a Bf-109 on average. Much less surface area and paint which weighs less than what goes onto a P51.

I tend to think the Germans did not go to bare metal completely because with their finish technology it was not the problem it was for the allies.

Not painting the leading edge would improve performance, save production materials, and time.

So this is correct for the RLM finishes:

But I do not think it is applicable for all aircraft finishes for all combatants during WWII.

All the best,

Crumpp

Re: Half painted Fw 190 wing undersides - the purpose?
 

This is very interesting information: do your sources cover British paints? My understanding is that the 1940 switch to the S or smooth paints with finer pigmentation meant that the British paints were equivalent to the smooth German ones: it is a bit of a surprise to find that the US lagged behind in this matter. This perhaps casts new light on the habit of some US fighter groups to use British paints.

Certainly the difference between a rough and a smooth paint finish could give a significant performance penalty: however I'm very surprised to see you discount the production story. Other steps taken at the same time, such as not painting the interiors with anti-corrosion paint, were certainly made in the direction of cutting production time and costs.

Re: Half painted Fw 190 wing undersides - the purpose?
 

Well, British findings following investigation that started when first such US aircraft appeared stated that there were no performance gains, and although finish was much easier to maintain, there were several drawbacks. There was a pressure from US industry to drop the camouflage, but decision was not taken until late 1944. This is discussed in Paul Lucas book on RAF markings 1945-50.
Another point is that Mustangs had their wings puttied and painted even in NM finish - certainly not without reason. Puttying was quite common, at least at some point during WWII, eg. Spitfire was puttied, although it is not often visible.
Certainly there were differencies between US (Du Pont?) finishes, British ones and German ones but I think you overestimate the effect. The bits in original paint I have sen or I owe are not representative but judging by photos, if RAF aircraft were properly maintained, there were no dents but some on walkways and movable panel edges plus a lot of discoloration, this after months of flying.
Regards

Re: Half painted Fw 190 wing undersides - the purpose?
 

I don't know much about the British paints. It sounds very interesting. From what Graham relates and the findings of the RAF I would say they did not have the problems the USAAF experienced. They sound very similar to the RLM finishes and probably did not have the need to change their finishes.

To me those kind of cutbacks make perfect sense. Most of these airframes were not lasting long enough to risk corrosion. However as someone stated earlier, when at their best the Luftwaffe designs were equal to the allied fighters in performance. A force made up largely of inexperienced poorly trained pilots was also flying them. The only hope the Jadgwaffe had was to have these new pilots gain enough experience to be effective. To do that they needed every once of performance they could muster. As the RAF found out in 1940 the airframe is replaceable, the pilot is not.

Not saying every airframe was a pampered formula one racer, I just think they did the most practical things they could to improve performance AND improve the logistics.

All the best,

Crumpp

Re: Half painted Fw 190 wing undersides - the purpose?
 

From "The Mighty Eight Warpaint & Heraldy" by R.A.Freeman, p14:

"The main benefit derived from discontinuing camouflage painting was the saving in production cost and time. Comparison test had shown a gain of between 4 and 7 mph, with weight saving dependent on the aircraft size and model"..."between 70 and 80 lb on heavy bombers and 15-20 lb on fighters"..."in combat service, there was no appreciable difference in performance"..."some fighters pilots claimed that polished and beeswaxed camouflage finishes gave greater speed than bare metal finish."

Re: Half painted Fw 190 wing undersides - the purpose?
 

Well, judging by samples of US paint coming from P-39Q that crashed some 62 years ago, the finish still looks fine and is quite smooth. Naval aircraft continued their finishes, so perhaps there is still something to dig out in this regard?
The German problem started elsewhere, I think discussing camouflage leads to a wrong track.

Re: Half painted Fw 190 wing undersides - the purpose?
 

I think something got confused here. They have to be talking about per coat of paint on a small fighter.

Either that or our paint guy was refering too the total weight of the paint before he put it on the aircraft. I will find out.

Good stuff. So bare metal was the better of the finishes for US Aircraft. This would not be the first time US results were different from British results in aircraft testing.

Certainly. The ocean is the harshest enviroment on earth especially for metals. Corrosion protection is probably on a different priority level in comparision to land base aircraft. Painting and scraping is a career in the Navy.

http://www.gim.bnl.gov/misc/envtest/...corrosion.html

I imagine life on a Carrier Deck is very tough on metal airframes.

All the best,

Crumpp

Re: Half painted Fw 190 wing undersides - the purpose?
 

I remembered to talk to Gary about this issue. I was confused. The paintjob added roughly 800lbs including interior finish to a B17. However on a P51 it only takes 4 gallons to completely paint the airplane.

Both the RLM and the USAAF used cellulose-nitrate based lacquers and the USAAF used Zinc Chromate Primer which is extremely heavy. The finish is thick and chips easily increasing drag.

While the milling of the German paints was much finer, it was their chemical engineering of the fillers that allowed the thinner, lighter, and equally smooth finish, combined with the fact they did not use a heavy metal based primer.

All the best,

Gene