Possible tank leak search help needed.

[cap01]

there are some pictures of my tank project in my album . mine would have been somewhat more involved than yours if you intend to install the same size tank . I had two 6gallon tanks which wasn't enough gas so I replaced them with the 12 gallon tanks . required removing a rib and relocating braces . also my wings aren't rib stitched but I wish they were . feel free to ask if any questions come up

[beeryboats]

I called John Mcbean tonight to order a couple things, including a new aluminum header tank. I asked about what I was seeing inside my tanks, and it sounded like he wasn't too sure he liked the idea of loose hunks of resin floating around. He also said some tanks were factory Kreamed. Not good. I swear mine have that coating, but it must be very thin. I need to take some still photos so I can post them to the group for viewing and feed back.

[Av8r_Sed]

I have the early 90's fiberglass tanks that were Kreamed. They have never seen Ethanol gas and the Kream appears as a very thin whitish coating on top of the light tan fiberglass. I don't have any delamination of the Kream (yet) and no gobs of resin, though my tanks have only seen a couple of years with fuel. During the annual condition inspection I pull the finger strainers and inspect the tank interior but have found no loose material in them to date.

[HighWing]

I have the early 90's fiberglass tanks that were Kreamed. They have never seen Ethanol gas and the Kream appears as a very thin whitish coating on top of the light tan fiberglass. I don't have any delamination of the Kream (yet) and no gobs of resin, though my tanks have only seen a couple of years with fuel. During the annual condition inspection I pull the finger strainers and inspect the tank interior but have found no loose material in them to date.

This has been my experience exactly with one difference. I did use ethanol containing fuel in my first Model IV. When I first looked in my tanks - 1993 factory Kreemed - I was disappointed to find that the Kreem was a very thin coating rather than the thick rubbery coating I had expected. It was my expectation that was wrong. I believe the Kreem was initially used to fill pinholes in the fiberglass rather than fill the exposed weave of the glass or protect the resin. I re-Kreemed once in the right tank because of very small leaks on the top of the tank just outboard of the filler neck that somehow caused eighth inch blisters In the Aerothane. After removing the Kreem, I tried filling with fuel and the tank held fuel like a colander would hold water - drips everywhere. After re-Kreeming the right tank - no issues for the rest of the 900 hours of flight time over nine years. This was with mostly autogas with 10% EOH but avgas on long cross countries.

Folks often relate the Kreem coming off in sheets to "mold release" This is not likely as the tanks are made up in female molds and then mated. The mold release would be on the outside - the smooth side. My guess is that the Kreem failures resulted because polyester resin is oxygen inhibited and the resin surface exposed to the air will not cure, but remain tacky due to the oxygen contact. Add Kreem to a layer of uncured resin and eventually the uncured resin will dissolve away leaving the Kreem floating on nothing. (The likely reason the new EOH resistant tanks require chemical rinsing before use is also due to the oxygen inhibited uncured resin on the (inside) surface of the tank - dissolve the uncured surface resin and move it to the carburetor and you will have a mess). Surface Type resin has a wax in the resin that floats to the surface and protects the surface from the oxygen, but I am not comfortable with adding Kreem to a waxed surface either.

I suspect over the years, more than one vendor manufactured the tanks - both my tank sets were manufactured by Denney Aerocraft. And without a doubt, even with a single vendor, different workers made up the tanks. These resins are extremely technique sensitive. A lot of variation can be introduced by resin quality, mix ratios, shop temperatures and simple attention to detail. Remember the old adage, "Don't buy a car assembled on Mondays or Fridays". I am afraid that some of us got tanks "made" on a Monday or Friday. The sad thing, in my opinion, is that the Kreem unfairly took the rap. Put any coating on a poorly prepared surface, whether it be a fuel tank liner or the finish on a flaperon and bad things can happen.

[beeryboats]

Thanks Lowell. Did you get your bleed screw back? When I talked to John he said to stay away from oxygenated fuel (autogas). I never did figure out if it was in relation to the tanks or the hoses.

So how bad a job is it to change the tanks? I'm not so worried about the price as I am about the job itself. How bad does it look when you're done? How did the paint match turn out? And I assume the wings have to come off.

I knew there was a fuel leak issue when I bought the plane, but I hoped it was a bad line. I had no idea the early tanks were crap until I bought the old girl, brought her home, and got on the forums. Yuck! Help!

[beeryboats]

Can those of you that built your Kitfox's back in the '90's tell me if I take the wings off, can I shake the odd bits in the tanks outboard so I can suck them out with the vacuum through the filler neck? I really don't want to remove the wings, and I really, really don't want to replace the tanks. She is so pretty I just can't stand taking a knife to the wing fabric. But I don't see anything amiss besides the chunks of resin. So, can I take the wings off and shake this crap near the filler neck or not? Where are the holes in the baffles?

[Wheels]

Here is a pic of the old tank on top of the new one. note the obvious difference in the material. You can count the new fittings, one of them is the fuel return.
I know you don't want to do it. I don't blame you and it isn't for the faint of heart. I would not tackle it without an A&P mechanic and now you have a bill.

As for taking off the wings, no problem on a model IV. take a look at the items you will disconnect. Pitot, fuel lines, strobes, return lines, hinge pins and voila, a two man job in about 2 hours if you go slow. Do you have disconnects on all your electrical? can you vacuum out the tanks and not remove them? Did yo say you didn't like the visual filters?
can you get more crap out of the wings by shaking them or is a vacuums the safe way? I changed em, I'm happy, I know I have done everything I can do to give a clean fuel supply to my plane.
For what its worth. I believe it was free.