Originally posted by Cobra412
It'll take less than a day or two in the right conditions for an aircrafts panel lines and rivets to start showing up. Reason being is fuel, hydraulic and oil leaks. Look at some F-15's from the middle east and you'll see how visible high leak areas are. Plus washing the aircraft weren't accellerated due to the area even though they got dirty extremely quick.
Leaks are entirely different things from panel lines and rivets. While leaks can effect panel line and rivet visiblity, they do so in different ways depending on the type of leak, and then only in their immediate area, not all over the plane.
Sure, any time you refuel the plane, check the oil, grease a control cable pulley, or whatever, you're going to make at least a little bit of a mess. And then the wet stuff attracts dust and dirt, so you end up with a dirty or clean area, depending on the type of fluid and where it is on the plane, how much got spilled, and how many times it's been spilled before.
Gasoline is a solvent and evaporates quickly, so it usually makes a clean spot in the general dustiness. It flushes away the crap that was there to begin with, and then evaporates before anything new can stick there. However, it can also damage paint over time, kinda melting it and eventually, over a fairly long time, working down to primer and then bare metal in the area right around the fuel filler cap. If the gasoline had dye in it, sometimes that gets left behind as the gas evaporates, too, staining the area with a light tinge of the dye color.
Gasoline usually makes panel lines and rivets LESS visible, at least for the first few months. This is because over time, fine grime collects in surface irregularities, even tiny ones, so rivets and panel lines show up a little more as the plane gets grimier. But the gasoline washes this away so the panel lines disappear again in the area of the spill. But this effect wouldn't have much "blow back" because any spillage would probably evaportate before engines even started. However, over a long enough time, constant gasoline spillage will eat away at the paint (if there is any there) at different rates for skin, rivets, and gap putty. In its most advanced stage, this really makes these features visible as some are down to bare metal but others are still painted. However, this takes a very long time, much longer than most WW2 planes lived.
Oils (including hydraulic fluids) and grease are just the opposite. These things are don't evaporate much at all, are sticky, and seem to have been designed to make a mess. Thin, tacky films of them remain long after the leak has been fixed, and all kinds of dirt, dust, and insects accumulate there. Beads of fluid can slowly blow back for considerable distances along the airstream, because they are in the boundary layer that doesn't move very fast. So you end up with these long, usually very narrow, but pretty visible streaks. Depending on where they are on the plane, they can be either the color of the local dirt or black with exhaust soot or brake pad scrapings, plus any dye color that was in the fluid.
Stains like these also have the opposite effect on panel lines and rivets as gasoline. Early on, the grime adhering to the fluid isn't very thick and usually is more than on the rest of the plane. Thus, panel lines and rivets tend to be more visible where the gunk goes. But after a while, the grime gets so thick that it becomes an opaque layer that obscures any feature below it. So if you start with a new plane, most rivets and panel lines will be very faint, but the stains will accentuate them in a few areas. Then over time, as grime accumulates all over the plane, the rivets and panel lines all over become more visible, except in the area of the oil leaks, where they get blotted out be extra-thick gunk.
