Stained Bottom

[skippydiesel]

I have been meaning to ask theses two questions for some time -

 

• How to prevent exhaust staining of my little beauties under side ? and
   
  
• Best way of removing said stain?
   
  

 

My aircraft is drawn through the upper regions by a Rotax 912 ULS, that drinks mainly ULP 98 RON and on occasions 95 RON. Uses so little oil, non is added between services. Aircraft is white (yellow may not show the stain).

 

I have tried;

 

• An extended exhaust pipe - very little difference
   
  
• Cleaning with truck wash gets the bulk off but a slight yellowing remains.
   
  
• Have tried paint thinners - some benefit. Iso - negligible, turps - also neg, metho - ditto and polish (not cutting) the same.
   
  

 

Hit me with your suggestions!

 

 

[spacesailor]

I want to say !.

 

A big nappie

 

there said it.

 

But is that stain on alloy or paint ?. could try a small baffle/ deflector to throw the exhaust gas off the surface.

 

spacesailor

 

 

[Thruster88]

Hit me with your suggestions!

I would look at the stain as a badge of honour, a battle scar, proof that you get out and enjoy your aircraft. If you want a hanger queen dont start the engine. Hope this helps.

 

 

[Marty_d]

Jeez, I'm glad you explained the situation... from the thread title I thought you'd had a near miss.

 

 

[pmccarthy]

Sometimes kerosine gets stains off that other solvents don’t. It doesn’t harm paint. Wash off with water.

 

 

[Blueadventures]

I use a wax and polish. Removes the muck and leaves a wax coating. Fuse is white fibreglass. Cheers

 

 

[skippydiesel]

I want to say !.

 

A big nappie

 

there said it.

 

But is that stain on alloy or paint ?. could try a small baffle/ deflector to throw the exhaust gas off the surface.

 

spacesailor

Paint (white) over composite.

 

Have tried extended exhaust - may have moved the commencement point of stain further aft but otherwise no benefit.

 

 

[skippydiesel]

Sometimes kerosine gets stains off that other solvents don’t. It doesn’t harm paint. Wash off with water.

Will give it a go - thanks.

 

 

[skippydiesel]

I use a wax and polish. Removes the muck and leaves a wax coating. Fuse is white fibreglass. Cheers

Have used high quality polish repeatedly - may have slowed development of staining but not stopped it.

 

Even tried leaving polish on (as a coating) again may have had some slight benefit.

 

 

[skippydiesel]

Just in case it may have a bearing - paint is Stewart System

 

 

[old man emu]

Have you considered that the stain is not actually a deposit of combustion products, but actually the fibreglass being overcooked by the exhaust gasses?

 

 

[johnm]

skippyd

 

try sunlight soap - you can buy a box of 4 cakes for about $ 4 ? (cheap, cheap)

 

use a cloth and soap on liberally to soak - wait say a few minutes and then get stuck in with the elbow grease - works a treat

 

the bloke that told me this said that if your having marital problems - give the spouse a soaping in sunlight soap - had no need to try this yet

 

 

 

[skippydiesel]

Have you considered that the stain is not actually a deposit of combustion products, but actually the fibreglass being overcooked by the exhaust gasses?

No I hadn't however, if I leave it long enough, staining starts about mid cockpit and extends aft to base of rudder - dont think there is a temperature issue, do you?

 

 

[skippydiesel]

skippyd

 

try sunlight soap - you can buy a box of 4 cakes for about $ 4 ? (cheap, cheap)

 

use a cloth and soap on liberally to soak - wait say a few minutes and then get stuck in with the elbow grease - works a treat

 

the bloke that told me this said that if your having marital problems - give the spouse a soaping in sunlight soap - had no need to try this yet

 

Great comment/advice - more serially, does "Sunlight" have characteristics much different to any other detergent/soap??

[Blueadventures]

Skippy you may have to consider a bottom repaint coat. In the past on boats I ran, say with Detroit diesels the soot would eventually eat into the transom paint. No end of trying all available cleaners and polishes would clean it up. The paint system was Stirling two pack. A top shelf product. I then had to repaint every 18 months or two years. Other vessel owners did the same if they were a good keen outfit.

 

 

[old man emu]

If the stain is extending that far back, then it's probably not heat. You'd expect the hot air to be dispersed by the time it gets that fat back

 

Sunlight household soap was introduced by the British company Lever Brothers in 1884. The Sunlight soap formula was invented by chemist named William Hough Watson, who also became an early business partner. Watson's process created a new soap, using glycerin and vegetable oils such as palm oil rather than tallow (animal fats).

 

Soap solubilizes particles and grime, which can then be separated from the article being cleaned. The insoluble oil/fat molecules become associated inside micelles, tiny spheres formed from soap molecules with polar hydrophilic (water-attracting) groups on the outside and encasing a lipophilic (fat-attracting) pocket, which shields the oil/fat molecules from the water making it soluble. Anything that is soluble will be washed away with the water.

 

Structure of a micelle, a cell-like structure formed by the aggregation of soap subunits (such as sodium stearate): The exterior of the micelle is hydrophilic (attracted to water) and the interior is lipophilic (attracted to oils).

 

 

[spacesailor]

Or you could try a little 1/2"baffle" attached to the exhaust top to deflect the gases down. (just like a water-hose, when putting finger at the tip,) Wouldn't need much.

 

or a small half moon filed into the bottom of the exhaust end, will have a similar effect.

 

Every other option is "after the event" procedure.

 

spacesailor

 

 

[Downunder]

I have the same staining (yes, yellow does stain). All I have found to get it off is acetone. (Carb cleaner)

 

Harsh? Yes, but I've not found anything else....

 

And then apply polish....

 

 

[spenaroo]

no experience here,

 

but what about a clear paint protection film.

 

we use it all the time on bikes and cars to prevent scratches and stone chips etc...

 

peel off, and apply a new one when it gets too stained.

 

I wonder if they will apply a ceramic coating to planes. that stuff is awesome

 

 

[FlyBoy1960]

Vortex generators, try to disturb the air flow to remove the laminar flow under the belly. Its (the airflow on the bottom - with contaminants) probably 'sticking' to the plane as it passes along. i have seen this on some other planes a few times.

 

 

[corvairkr]

Skippy, have you got a close up photo of the Staining ?

 

If the Chemicals you have tried have had little effect, I would start doing test spots starting with a light Polish/Pad Combo gradually moving up to a heavy Compound and even Wet Sanding if required. Sometimes there just isn’t enough Paint to remove the defects and repainting is the only option.

 

It would probably be easier and cheaper for you to get a GOOD local Detailer to have a look at it for you ( I may know someone in your area )

 

For protection you can’t go past a good quality Professionally applied Ceramic Coating although there are consumer grade coatings available prep is key to a good result.

 

Jason

 

 

[skippydiesel]

Skippy, have you got a close up photo of the Staining ?

 

If the Chemicals you have tried have had little effect, I would start doing test spots starting with a light Polish/Pad Combo gradually moving up to a heavy Compound and even Wet Sanding if required. Sometimes there just isn’t enough Paint to remove the defects and repainting is the only option.

 

It would probably be easier and cheaper for you to get a GOOD local Detailer to have a look at it for you ( I may know someone in your area )

 

For protection you can’t go past a good quality Professionally applied Ceramic Coating although there are consumer grade coatings available prep is key to a good result.

 

Jason

Thanks Jason - I can remove most of the exhaust marking but over the two + years since refurbished the aircraft (complete paint job amongst other things) the stain, although very light after a good clean, now seems to be ingrained.

 

The use of any sort of cutting compounds will remove the stain, damage the paint in the process and not prevent its re-occurrence.

 

I can live with the very light staining I have now, if I must but would like to prevent further staining (darkening) if possible.

 

I will not be repainting in the foreseeable future - a major costly in time & $$ proposition.

 

I am interested in this "Ceramic Coating" please tell me more.

 

 

[Mewp]

A vinyl wrap on the area may protect the skin and can be easily removed when necessary

 

 

[old man emu]

I wonder if the cause is some additive in the fuel. Which brand of fuel do you use regularly? Maybe it's the stuff that BP and Shell add as a cleaner and the stain is an accumulation over time of the cleaner and anything it has removed from tth engine.

 

 

[skippydiesel]

I wonder if the cause is some additive in the fuel. Which brand of fuel do you use regularly? Maybe it's the stuff that BP and Shell add as a cleaner and the stain is an accumulation over time of the cleaner and anything it has removed from tth engine.

At "home" mostly Mobil, on occasions Caltex, my nearest BP is about 30-40 minutes drive away Shell similar but always more costly. When away the most accessible main brands 98/95 RON (BP/Caltex/Shell/Mobil) on vary rare occasions have loaded no name 95 and on 2 trips away, topped up with AvGas.