As I've mentioned before, I spent a few years working as a mechanic on F-16's in the USAF.  I observed these (at that time) brand new aircraft as the surface finish changed over time, this little "article" is intended to describe the "weathering" process for a modern fighter plane (not a Japanese Zero in 1944).

The undersurface of an aircraft gets dirty quickly,  All kinds of oil and good amount of soot just works its way down due to gravity, and seeps out onto the lower surfaces of the fuselage.  It's quite filthy looking and the crew chief is usually happy that's it's underneath and not easily seen.  But you can get "in flight" photos that show the mess.  The longer an aircraft is just allowed to "sit" without a good cleaning, the dirtier it gets.  For modeling purposes, this takes the form of "black streaks" that show up, tending to originate at a panel line and then the force of the airflow blows the gunk back across the panel.

Aircraft are, in fact, washed regularly.  After a good wash the plane looks very "new" again.  The wheel wells on most aircraft since the 60's are gloss white.  It's white to show any tell-tale "pink" that would indicate a hydraulic leak.  These things can be hard to spot, as they may only leak under pressure and when the red-tinted hydraulic fluid leaks out at 3000 psi the result is a pink fog that may not be noticed immediately, but this type of leak is particularly dangerous since it means the hydraulic fluid could actually be lost, followed by the aircraft!  Hence the bright white color.  It's glossy because if you DO get hydraulic fluid on it, the stuff is sticky and dries like maple syrup, and has to be removed somehow.  The gloss surface makes it easier to remove the dried fluid.

Most hydraulic leaks on real aircraft do not leak under pressure.  They create "slow leaks" that just ooze the red fluid out along panel lines and then maybe drips off onto the ramp.  The stickiness of the fluid contributes quite a lot to the overall filthiness of the aircraft when it finally gets washed.

In between washes, the crew chief is supposed to get "a rag" and "spot clean" the plane.  This is not always so easy to do,and the cleaning fluid is jet fuel that can be accessed from any of a number of "drains" that allow the fuel to be checked for water or other contamination.  This is not a particularly good cleaning method, but the aircraft can be kept reasonably clean most of the time.

The type of paint used to paint modern aircraft is incredibly tough.  It doesn't chip off or wear away, unless the refueling boom on the tanker actually rips a big old scratch in the surface near the refueling receptacle.  However, on occasion a new part may be installed (like a vertical stabilizer) and be painted in a "less than stellar" fashion.  Then the paint may "tear off" but you won't see bare metal.  You see the zinc chromate yellow  primer where the gray paint came off.

Over time, the orginal "dead flat" paint will begin to grow more and more shiny, as the plane is washed over and over again.  After a year or so, a plane will take on a definite "semi-gloss" appearance.  New planes tend to be "dead flat" and older ones are "semi-gloss."  

Eventually, however, all planes are sent to the "depot" where they are torn apart, re-built and re-painted.   So an old plane comes out looking like new.

In recent years, experiments with "radar absorbing" paint on F-16's (and others) have resulted in some really, really funky looking jets.  This type of flat, rubber-y paint is very difficult to clean and so it gets dirty and stays that way.  Some photos you may see of really "beat" looking fighters are probably wearing this type of "stealth" coating.

On F-4 Phantom aircraft, the area around the exhaust nozzles is usually black from the soot that the engines pour out.  However, as we modelers know, there is this mysterious "shiny metal" area right next to the soot-blackened area right behind the exhaust nozzles.  You may have wondered what causes this peculiar effect, especially in those cases where the soot if really black and the bare metal looks chrome plated.  Well, the answer to the riddle is that the crew chief was to get out there every day and polish that metal.  That's why it is so shiny and doesn't get sooty.  

On World War II planes, we see the paint actually worn off by the feet of the crew walking on the wing.  On a modern aircraft this doesn't happen unless something is seriously wrong.  But, you do get nice dirty footprints on the nice clean airplane.  I've been looking, and I have yet to see a 1/48th Phantom or Viper with some in-scale footprints on the wings or fuselage even though you can clearly seem these on the real thing.  (I have to admit that I have seen at least on Spitfire model that had some footprints on it).

Finally, when I was at Kunsan Air Base, Korea in 1983, the F-16 that I was assigned to collided with a Marine Corps F-4 during "dissimilar air combat training."  The F-16 pilot ejected safely but Marine Phantom flew back to Kunsan and landed, with some holes in its tail where it sliced the wing off of the F-16.  Later the Marines patched those holes with soda-pop cans.  When the Phantom left Kunsan, you could clearly see the bright labels of "Coca-Cola" etc.-- I know this sounds like absolute nonsense but I saw it and I remember it precisely because it was so amazingly weird.  All I can assume is that this was an attempt to practice some kind of "battlefield" repair technique.

I've always thought that would make a very interesting model...

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Ayup Dan...

Thanks for that amazing insight. It certainly gives one food for thought. I think where the 'Problem' with modern jets is that it's not so much a wish to dirty the surface as to highlight the panel lines, and that's a really DIFFICULT thing to do. Especially, 'In Scale'. Modellers just don't seem to grasp the concept of scale panel lines, which are, of course, Invisible, or the Manafacturers come to think of it !

This 'Misunderstanding' i think, is what has given rise to the finishes one sees in Magazine builds, good as some no doubt are, but as you've described, are utterly wrong. Which is something ALL of us should think about when building them.

Thanks again, Dan.

Your posts have an excellent signal to noise ratio Dancho!

But how about some photos to illustrate the points?

Paul

Hey all

An excellent read dancho really good to get some hands on perspective on weathering.  Nothing like the experience of someone who's done it, and the article was really well writen .  Now which a/c I'm to do will get footprints... .

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Great info Dancho.  That was really a well constructed article which I find far more informative than most I read in those modelling magazines.  I really only have one comment concerning the appearance of base metal on an aircraft.


I've got a handfull of hours in F-16's, spent in the back seat of a D-Model, and I've seen countless other fighters up close.  Always I look at them with my model builder's eye, and I have to say your comments are exactly right when it comes to fighters.  I have never seen bare metal showing on them anywhere, and only rarely have I seen the yellow zinc-chromate.  But I fly B-52's, and those old workhorses do have a surprising amount of bare metal showing.  It usually forms around the leading edges of the wings, stab, fin, nose of the tip tanks and engine nacelles.  As you might expect the bare metal areas are typically surrounded by a thin ring of yellow zinc chromate, showing that in those particular areas the paint fist wore through to the primer, then eventually to the bare metal.  Now the bare metal is only in small patches, even on an aircraft the size of the Buff.  Like you said when the jet goes to depot, it comes back all nicely painted again, but those with a lot of hours on them tend to look a little beat up.  The patchs on a Buff could be modeled in something as small as 1/72, but even then I wouldn't do too much.

My personal experience is with the B-52, however I'd be willing to bet there's similar wear issues with the other heavies.  (Except for the obvious ones like the B-2, C-17 etc.)

Anyway, I just figured I'd throw in my observations.

Great insights chaps  :thumb:

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I do wish that I had taken more photographs!  The few I have are pretty mundane (no photos of a USMC F-4S with Coke cans riveted to its tail ).

Here's a photo that shows the "sheen" that F-16's acquire over time.

http://kalaniosullivan.com/KunsanAB/8th ... alcon2.jpg

...and here's an interesting read about the plane that I was assigned to for a very brief time (before it failed to return one day).  "My" version differs from this one slightly because what I knew of it came "down the grapevine" and not through official channels.  Also, the Marine jet DID have a patched  up tail, so just how that happened I don't know (but we can assume that the damage to the tail was minor, hence the "soda can" repairs!)

http://www.ejection-history.org.uk/proj ... _Daryl.htm

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Here's something about prop planes that most modelers just aren't aware of-- but if you study to get the FAA Airframe and Powerplant Certificates you get to learn this amazing fact.

The part of the propeller blade that faces aft (relative to the airplane) is the FRONT of the prop.  The part that faces forward is the BACK of the prop.  Think about it. The front of the prop moves into the air and the "back" follows it.

Keep thinking...

Anyway, here are some images of how this causes the paint on the front of the prop blade to wear off--

http://www.warbirdphotographs.com/LCBW/Me109-D0-49.jpg

http://farm4.static.flickr.com/3021/294 ... 0a.jpg?v=0

The sand in North Africa really seemed to remove the prop paint!

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Remember aswell as wind hitting props stones do, and stone chips have to be filed out so you could slightly file one prop blade off and show some bare metal, but dont go mad otherwise it looks silly and in real life would unbalance the prop

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dancho

I, too, worked in an airforce in the late 70's/early 80's.  you are correct about the state that aircraft get into.  Our F4s smoked far less than yours and we were not compelled to polish the bare metal bits (actually Titanium).  Also bringing back memories was the cola can repairs.  This, we called BDR (Battle Damage Repair).  Broom handles could be used as control pushrods etc.  

Did you ever come across 'Speed Tape'?  This may be worth considering when weathering an F4 era jet (not sure if it is still used).  This was an aluminium foil in quite a heavy gauge.  This was backed by a strong adhesive and was appied to the skin to cover damaged areas.  It you used to stay on even after supersonic flight.  It would look like a bare metal patch that would dull down and become matter with age, like a bare ali skin.

I always thought that that shineyness was as an accumulation of oils and greases that was engrained in the finish.  Our F4s were washed about once a week and I had a broken wrist slipping off a Sgt Fletcher tank once during one of these washes.

I would add, that personally, I always aim for a semi matt finish for my models.  I feel that matt is far too matt and gloss is far to gloss for most scales.

Brilliant article and I should think that it will help a lot of modellers.

Thanks for stirring some great memories.

Ian

Cannot thank you enough for that post!

Fascinating and insightful, thanks guys!

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A really brilliant article, read and thread, nice to hear from some real Pros about the REAL thing !

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In case anyone has wondered, the above is a direct quote from an Irish MP who was stunned to find out that the Irish Air Corps had no jets.

It was a great read.



An old German Phantom II.
I took these two pictures some years back at a show here in Denmark.
It shows clearly a paintjob far from uniform or prestine.

Jesper.

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Great article and thread with loads of info.  8-)
Thanks guys.  :thumb:

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You want to see the dirt you get on a Skyraiders exhausts!
I've seen a perfectly clean one take off from Duxford and within a few hours is streaked with black and brown exhaust.

This one is positively clean



Can only imagine what they would look like after an 8 hour mission, or several 8 hour missions.

BTW what causes ww2 Japanese aircraft to weather so badly. Is this inferior paint? I've seen images where they are pretty much back to bear metal.

I want to thank you guys for resurrecting this old thread.  I must have been feeling very energetic when I wrote that!  I think it's all true, but I've seen all kinds of photos of all kinds of weird stuff so the only way to go is to either get some good photos of the airplane/ship/tank you're trying to mimic or just admit (as I do, usually) that it's an artistic representation or something.

Now about those Japanese paint jobs.  I have my own crackpot theory about it that I would love to share.  I've read  "The Rising Sun" by John Toland WAY too many times.  From Toland's analysis of the Japanese mentality during World War II, it appears that it may have been common in the Japanese Army Air Force to think of camouflage as cowardly.  To attempt to hide one's aircraft would have violated the bizarre version of bushido that held sway in those days.

So... I think that, in addition to all the other very good theories out there, the Japanese Army felt that having the paint peel off was "good and proper" because it tore off the despised "cowardly" camouflage and revealed the true samurai bare metal and bright red hinomaru that bushido demanded.

That's my theory.  They gave them lousy paint jobs because the lousier the paint job the braver the dude that was going to be spotted in the air due to shiny metal and then sent to visit his ancestors by an F4U.

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Ayup Dan...

I LIKE that Theory Mate. Top stuff.

Great thread with lots of interesting stuff from the guys who have been there

Many thanks Dan and others for this

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Its all do to with the primer coat.
Aluminium needs a special paint which contains a large amount of acid. Its called an 'etch' primer. It eats through the microscopic layer of aluminium oxide that is always on the surface of the aluminium. Try polishing a bit of aluminium and see how dark the cleaning cloth gets, then do it again the next day, and you'll see how quickly the oxide forms.
Up to the mid-war period etch primer was not invented, and when it was it was expensive to make and used vital resources - the acid. That acid could be used in other industries.
Also, the metal used in paint was lead, used for helping the paint to 'grip' the surface. As the war went on lead became scarce and again was needed for other items, such as bullet cores, or as additive to petrol [gasoline] to increase the octane rating.
Without the lead, and not having etch primer, the paint on aluminium surfaces had little chance of adhereing to the surface, thus quick wear and chipping off.
QED.