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  #11  
Old 08-06-2014, 06:51 PM
crabandy crabandy is offline
 
Join Date: Jan 2010
Location: Ottawa, Ks
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I let my friend run my 7 hrough the aerobatic portion of testing, all the various basic aero maneuvers (spins/loops/Immelmens/humpty's/clover leafs/split S/Cuban 8/hammerheads) and +6/-1 G's (no inverted systems and carb). The engine actually quit on the hammerheads. I gave the airplane to him with 6.5 quarts of oil and he returned it an hour later with 3 3/4 quarts. I cleaned the airplane/FWF/belly etc the next day and I'm still finding oil by the rudder and tailwheel 30 hours later.
I've found that I won't lose much/any oil out the breather doing loops and rolls, but anything that starts flirting with >1 G burps it out pretty quick.
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  #12  
Old 08-07-2014, 08:32 AM
RV8N RV8N is offline
 
Join Date: Mar 2006
Location: Sandpoint, Idaho
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As others have stated, it only takes a very short time at close to 0 G to get oil in the breather tube. It will then take several hours of flight time for all the oil to work its way out.

When I was flying my -8, I hated a dirty belly more than I enjoyed the aerobatics. My rolls were always barrel rolls and my loops were egg shaped to maintain at least 1/2 G at the top. I still has some oil on the belly at times.

FYI, I had a strait breather tube with no separator.

Karl
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  #13  
Old 08-07-2014, 09:44 AM
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donaziza donaziza is offline
 
Join Date: Jun 2007
Location: Atlanta
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Quote:
Originally Posted by RVG8tor View Post
I had the same issue, went slightly negative recovering from a botched loop (1st one this plane) and dumped a 1/2 qt of oil. I had oil on the belly and inside the fuselage floor all the way back to the tail.

My theory is that it entered by the aft corners of the exhaust ramp. I pro sealed the side to help prevent cracking put left the corners open in order to allow moisture to escape.

I washed down the inside with mineral spirits. There was oil in between the front floor sections and every flight I get oil at the aft edge rivet line where the double floor becomes a single floor. This decreased with time, but I still get a tiny bit after a longer flight.

So I would say a big slug of oil came out and some made its way to the inside.

Cheers
I washed down the inside with mineral spirits. There was oil in between the front floor sections and every flight I get oil at the aft edge rivet line where the double floor becomes a single floor. This decreased with time, but I still get a tiny bit after a longer flight.

Hi Mike, Just read you reply about the mineral spirits. How did you do this? Did you put the mineral spirits in a pump sprayer and then spray the floor of the aft fuselage as best you could reach? A sponge attached to the end of a long pole perhaps?
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  #14  
Old 12-28-2014, 09:12 AM
maus92 maus92 is offline
 
Join Date: Nov 2013
Location: Annapolis MD
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I have clean oil under the floor of my RV-8A, all the way aft from the pilot's seat back to the tail - can't figure out how it got there. I first noticed it from little oil drips on the hanger floor under/near seams, and when I disassembled the plane to install its avionics MLU, I found a film of oil in the belly. I don't fly aerobatics. At first, I thought the previous owner may have spilled oil from a spare quart in the front baggage compartment. But after reading this thread, I am becoming suspicious. I *believe* the builder installed an oil breather / separator high on the firewall - it's a black oil filter shaped can with several hoses attached. No labels on it. One of the attached hoses dumps overboard, routed down the firewall and porting whatever through the exhaust opening in the cowling. Yesterday, I did find a hole in that hose where it rubbed against a structural member - now I'm thinking that is the source....?
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  #15  
Old 12-28-2014, 11:22 AM
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RV8iator RV8iator is offline
 
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Location: Saint Simons Island , GA
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After a couple thousand hours in my 8, I can attest that without an inverted system you will get oil in the fuselage if you do hammers, negative, or zero g stuff.

Heck, I have an inverted system and I still get a little. Going from inverted to inverted when practicing slow rolls that stuff still finds its way out of the engine.

As to running down the fuse floor, don't know how it knows, but it does. I think the Thermos folks invented the system. It just know..

I love acro, and cleaning!
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  #16  
Old 12-05-2015, 09:43 PM
mlwynn mlwynn is offline
 
Join Date: May 2005
Location: San Ramon, CA
Posts: 402
Default Oil in the Fuselage

I had my rear baggage floor off for annual and found a thin stream of oil going back. This thread helps me see that it is not all that unusual. I prosealed the front of the fuselage bottom skin components but don't think I prosealed the junction of the rear tail skin with the mid fuselage. That seems to be where the oil is sneaking in. Anyone with ideas about how I might seal that joint?

Right now, it's full of oil. Can't imagine how I could get it clean enough to effectively seal. Shame aerobatics are so much fun....
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  #17  
Old 12-05-2015, 10:25 PM
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RVTrumpet RVTrumpet is offline
 
Join Date: Jun 2012
Location: Hillsboro, OR
Posts: 63
Default Pressure!

The air inside the fuselage and tail cone is at a much lower pressure than the air flowing past outside. The pressure delta effectively creates a vacuum inside the tail cone which sucks in the oil flowing on the belly when it tries to cross the fay seams.
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