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  #1  
Old 09-11-2014, 05:10 PM
dick seiders dick seiders is offline
 
Join Date: Jan 2006
Posts: 885
Default fuel residue in tank

I am in the process of upgrading my fuel tank to the latest frangible bolt mod. (13-12-19 I think). I had completed my 2013 Cond. Insp. just prior so am catching up now. I decided to remove the top skin as someone in the forum suggested some time ago so I wouldn't have to go nuts trying to do the work thru the sending unit door.
After removing the skin I noticed a gray colored coating on the bottom of the tank. I can easily wipe it off, but I am curious as to it's identity. The coating showed fuel trace marking from draining the tank yesterday which suggests the stuff is moving around with the fuel, but it dried as the fuel evaporated after draining tank. Now that it has dried it will stick to your fingers if you rub them on the tank bottom skin and the dried material is very fine powder in appearance. Very interesting. Does this residue burn with the fuel? If so is that a good thing? I guess the answer there is it depends what it's from. Do any of you know what it might be? Has anyone else seen the stuff?
Thanks for any feedback.

note: If there are more out there that have not yet done the upgrade, and you decide to remove the top skin as well be sure to order a new T 1204B flange for the tank. The skin holes are all pre-punched and it's very likely your flange hole pattern will not match up to the top skin. Ask me how I know.
Dick Seiders
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  #2  
Old 09-11-2014, 07:01 PM
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KALEWIS KALEWIS is offline
 
Join Date: Nov 2009
Location: Jackson, OH
Posts: 468
Default

Are you using 100LL with decalin?
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  #3  
Old 09-11-2014, 07:32 PM
dick seiders dick seiders is offline
 
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Sorry, I should have mentioned that I burn almost 100% premium auto fuel. I did use 100ll p[us Decalin two yrs ago during a trip to Oshkosh, but none since.
Dick Seiders
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  #4  
Old 09-11-2014, 09:31 PM
Slane Slane is offline
 
Join Date: May 2008
Location: Hillsboro, OR
Posts: 154
Default Me too, regarding residue

I found the same residue on the bottom of my tank too. Only premium auto gas in my tank at this point and only 17 hours on the hobbs, so not many gallons through the system.

I'm curious to know more...

Slane
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  #5  
Old 09-12-2014, 08:05 AM
dick seiders dick seiders is offline
 
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Posts: 885
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Typed in a post and lost it. basically what I said was based on what Slane saw in his tank with only 17 hrs on the engine and mine with the same thing at 240 hrs the premium auto fuel must have the gray matter in it's formulation. Probably the only reason more have not seen it is not many take the top skin off and so don't get the view. There you go. Probably we all have it and don't know it So it apparently not a problem , right? For one I would like to know what it is. Are there any chem-people in the forum who could provide some intelligence on this? After all if we all have it there must be some additional curiousity out there.
Dick Seiders
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  #6  
Old 09-12-2014, 11:12 AM
DHeal DHeal is offline
 
Join Date: Sep 2006
Location: Windsor, California
Posts: 692
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Could the residue in the tank be a product of mogas storage in plastic 5-gallon containers? I have noticed that if I store mogas (Premium 91 auto gas) in red plastic 5-gallon containers for more than a couple of days, the fuel takes on a pinkish hue which may be a product of the fuel's (ethanol's?) interaction with the red plastic? Or, it may be some initial form of "phase separation"?
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Last edited by DHeal : 09-12-2014 at 12:26 PM.
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  #7  
Old 09-12-2014, 12:49 PM
bobnoffs bobnoffs is offline
 
Join Date: Jul 2012
Location: n. wi
Posts: 505
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for the past 130 hrs i have burned only premium no lead auto gas.the aluminum wing tanks in my dakota hawk are only 6 gallons so i get a good look at their insides with a flashlight every time i add fuel.......the inside bottoms are spotless and shiny.
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  #8  
Old 09-12-2014, 06:04 PM
RFSchaller RFSchaller is offline
 
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Location: Phoenix, AZ
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At next annual I might stick a bore scope down the filler neck and check this.
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  #9  
Old 09-13-2014, 08:35 PM
dick seiders dick seiders is offline
 
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David, my gas cans are yellow and I see no tint after 4 years of use. Don't know what we are looking at, but doubt is bleed-off from the gas bottles. I am trying to get some assistance from Tony T. on posting a photo of the material in the tank to this thread. The only guess I have thus far is the gray stuff in it's dry form bears a resemblance color-wise to the fuzz I find each condition inspection on my gascolator screen. Another possibility is IF the ethanol is slowly degrading the tank sealant the residue could be very fine particles of the partially dissolved sealant. The gray color is a very close match to the sealant we use. I never had this material show up in my RV6A, but I also never had autogas with ethanol in the tanks. Interesting? I may contact Flamemaster and ask if they would like to analyze a sample of the powder recovered from the tank. Now THAT would be ineresting.
Note to Bob Noffs in the Dakota Hawk comment. Are your tanks sealed with the same material we are using on the RV12's? (Flamemaster 3204 class B2)
Thanks for any feedback.
Dick Seiders 120093
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  #10  
Old 09-14-2014, 05:49 AM
bobnoffs bobnoffs is offline
 
Join Date: Jul 2012
Location: n. wi
Posts: 505
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forgot to mention my mogas is ethanol free and i have no sealant in my tanks, they are welded.
so maybe the alcohol is reacting with something?
i guess the end point would be to have a sample analyzed which seems reasonable because at what point can this stuff cause a problem somewhere?
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