Engine exhaust stains with an airbrush help.

[viking73]

Hi,

I am building the new tool 1/72 Revell F4U-4 Corsair and I've been thinking I'd like to try my hand at simulating the exhaust stains with my airbrush. I've never attempted this before since I've usually a jet guy.

My question is, how do you guys go about this? Really thin paint and low air pressure I'm assuming? What color(s) are best? From photos, I'm thinking of a light sand or light gray color - or maybe both? And then when it comes time to paint the stain, do you start at the end of the stain and work your way back to the stacks where it's the heaviest amount of staining? I'm thinking that tape over the cowl flaps will keep the stain where it needs to be.

Any light you can shed on this would be great, thanks in advance!

-Derek

Edited August 19, 2016 by viking73

[habu2]

1 - light thin coats built up slowly

2 - practice on a junk model or even a plastic water bottle

[Thommo]

Yeah, it can be tricky, esp if using acrylics where different colours seem to behave differently in my airbrush.

On this Corsair (1/48) I pretty much did what Habu said - light coats, numerous passes with a light grey but then created some downward steaks like on th real thing by quickly brushing downward with a paintbrush dipped in thinner straight after painting.

On this 1/72 Corsair, same method but added a tiny bit of grey-brown right by the exhaust outlet (again, very thin paint, very slowly added).

Edited August 21, 2016 by Thommo

[jfmajor60]

IT takes some practice, I use MM enamels so what I do to safeguard against me screwing it up is over coat the area with a coat or two of future, this way if I do make a mistake I can remove it with a cotton swab and some mineral spirits without harming my finish paint.

[viking73]

Thanks for your comments gents. I was wondering about the vertical streaks I see in the photos of the real thing, very good idea Thommo. Nice Corsairs!

I'm itching to give it a try. When I do, I'll be sure to post some results. My little Corsair is just about all build up and ready for its first primer coat.

-Derek

Edited August 21, 2016 by viking73

[TheRealMrEd]

A short discourse on exhaust stains left by reciprocating engines on dark-painted (U.S.) aircraft -- first, the light grey --almost white, makes up most of the stain. Depending upon fuel type and length of time on the engine since last overhaul, there will be anywhere from a little to a lot of light tan, but not extending as far back as the grey. Lastly, we have the black soot effect. Not seen much on fairly new, good-running engines, it can be really bad on old warhorses at nearly the end of their useful flying time before overhaul. This 3-tone effect is especially prominent on land-based F4U Corsairs during WWII, but not as bad as on carrier-based or training aircraft.

Of course, the pattern of the exhaust stain will be unique to each type of aircraft. Also, different fuel used by the Germans in WWII would result in slightly differing colors of exhaust.

The best way to determine what colors are best used, it would be illuminating for you to examine spark plugs taken out of various engines, even lawn mower types, and you will eventually see all these colors, and the conditions of combustion which cause them.

The following photo offers one example; please excuse the dust:

Ed