[RVG8tor]

Okay, I am in my initial flying and I have to admit that I was surprised how how much pull I need to complete a loop, I was getting right into 3 G but then backing off for fear I would bleed to much energy, well the stick needs to be held and actually brought back more, great fun once I understood what to do. In working up to this discovery I manged to get slow at the top 45kts and thought the prudent thing to do was to unload and let her seek her own nose down trajectory, about .125 G. All this did not take but a few seconds. So once back home I spend a nice bit of time cleaning the oil off the belly, it went all the way back to the rudder!! It was only a 1/2 quart low but it sure looked like I emptied the sump. A day later I notice an oil drip coming from the seam of the belly skin, it was at the low spot just in from of the rear seat. Looking at the inside I have oil on the inside. I also have a stream of oil on the inside the entire run of the belly.

I am wondering how it got there, is there enough pressure difference that the oil will wick between the lap joint in the skin! Could it migrate from the tail forward. My QB fuselage has a hole in the tail for the tail wheel setup that I never plugged, I figured it would just be a drain.

I have heard guys talk about oil on the belly from zero "G" but never have I read about it getting inside. Any tips on cleaning this up, I am sure the painter will not be please to have oil seeming out of the lap joints. I am thinking some mineral spirits will thin the oil enough to get it to flow out then follow with some alcohol to dry and dry things out.

Thanks for the advice
Cheers.

 

[flyinga]

Mike,
I don't think since you never got to zero or negative g that this would csuse so much oil on the belly. How much oil are you running in the sump? There has been lots of discussion about findint the "sweet spot" in oil quantity for your particular aircraft. I run right at 6 qts; IO360 angle valve. When I did my acro checkout for the airplane I didn't notice any increased oil usage or leakage.

Could you have a leak further forward that's getting under the belly skins? Perhaps from the firewall area?

 

[RVG8tor]

6Qts

Mike,
I don't think since you never got to zero or negative g that this would csuse so much oil on the belly. How much oil are you running in the sump? There has been lots of discussion about findint the "sweet spot" in oil quantity for your particular aircraft. I run right at 6 qts; IO360 angle valve. When I did my acro checkout for the airplane I didn't notice any increased oil usage or leakage.

Could you have a leak further forward that's getting under the belly skins? Perhaps from the firewall area?

I was at just over 6 qts, I fill up to 7 and let it go down to 6. It was 1/2 quart low after I go back. I downloaded the data from the EFIS and the lowest G was positive .125, it was recording every second so I am fairly certain I did not go negative. I did on another occasion with the same result
There I was at minus .125, thankfully my learning curve a steep and I have had not more slow at the top issues.

I can't see how oil is coming from the firewall as there is no evidence of that , The floor in the -8 is two levels until the wing spar and there is not oil in the wing spar cavity. I first thought with no fairing the oil may have wicked up the gear but it did not take that route.

Mystery so far.

 

[fl-mike]

The belly skin oil-can's inward in flight. The panel behind the rear seat. So perhaps the oil got pushed in there. I expect most of the belly is at higher pressure in (normal) flight and positive AOA.

As a bonus (!), you can expect to have paint adhesion issues along those seams down the road.

 

[RVG8tor]

That's on of my questions

The belly skin oil-can's inward in flight. The panel behind the rear seat. So perhaps the oil got pushed in there. I expect most of the belly is at higher pressure in (normal) flight and positive AOA.

As a bonus (!), you can expect to have paint adhesion issues along those seams down the road.

How does one go about trying to clean out this oil, my thoughts are in the first post, I am hoping someone with experience might have some ideas.

Cheers

 

[tadsargent]

Mike based on your comments I think you should find an instructor for aerobatics in the RV. 45 Kts is too slow at the top and the initial G pull is too low. Please get some assistance with the numbers

 

[AlexPeterson]

I'm no expert, but 3 g's entry is enough to nice loops in my O360/CS 6A. Just be sure to bring them on fairly quickly. I'm wondering if you are unloading a bit too fast on the vertical (90 degrees into the loop)? If the resultant loading on the oil is nearly straight aft, it will certainly come out of the breather.

As to cleaning out the oil... hmm. A good idea regardless of oil is to spray water up onto the belly when parked on a level surface. Wherever water seems to collect, drill a hole up through the skin. This will allow draining when parked in the rain. Perhaps pulling the floor skins and dousing some non-flammable solvent in there? Don't know what that solvent is, but it should drain out the just-drilled hole.

 

[RVG8tor]

Experienced

I'm no expert, but 3 g's entry is enough to nice loops in my O360/CS 6A. Just be sure to bring them on fairly quickly. I'm wondering if you are unloading a bit too fast on the vertical (90 degrees into the loop)? If the resultant loading on the oil is nearly straight aft, it will certainly come out of the breather.

As to cleaning out the oil... hmm. A good idea regardless of oil is to spray water up onto the belly when parked on a level surface. Wherever water seems to collect, drill a hole up through the skin. This will allow draining when parked in the rain. Perhaps pulling the floor skins and dousing some non-flammable solvent in there? Don't know what that solvent is, but it should drain out the just-drilled hole.

I have flown aerobatics just not in an RV. In my first attempts I pulled nicely for the first quarter loop and thought I should back off a bit and this got me slow. After this I talked with someone and figured out what I did wrong. I then went out and did a loop to a Cuban 8 to 3 leaves of a clover leaf all with no problems. This did give my right arm a workout, especially with the forward CG. I must say I was impressed with the energy of the RV, I thought I would loose energy stringing this maneuvers together but I found myself gaining altitude. My mistake was not talking through the maneuver with an experienced RV person first.

I do appreciate the caution and suggestion for training. Some good ideas on the cleaning up. I already drilled the drain hole, but the oil is thick when cold I may run a heater under there belly to make the oil run better then maybe good old Dawn Dish soap.

Cheers