Half painted Fw 190 wing undersides - the purpose?

[Crumpp]

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.

Interesting discussion!

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

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 .

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

[Franek Grabowski]

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.

[Crumpp]

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.

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:

In case of needed puttying, (aircraft putty 7270.99) it should be applied on bare metal beyond the border lines of the paint scheme and the bare metal should be polished in the usual way but no camouflage on top of the putty.

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

[Graham Boak]

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.

[Franek Grabowski]

Originally Posted by Crumpp

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.

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.

Remember too, using the Oberflächenschutzliste 8 Os 155:
It is very doubtful bare metal would have just been left in a rough surface.

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.

[O.Menu]

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...

[John Beaman]

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.

[Franek Grabowski]

Originally Posted by O.Menu

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

No, it was only to speed up production.

[Crumpp]

No, it was only to speed up production.

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:

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.

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

All the best,

Crumpp