Fuel System

[adam.rigden]

I have an early Kitfox 5 outback.

Currently I am finishing up the fuel system, specifically the fuel lines from the fuel tanks to the header tank. My question is should the screen fittings that screw into the tanks be inspected periodically for contaminants such as part of an annual inspection? Does anyone know how robust the threaded holes in tanks are? Is there threaded inserts or it just into the fiberglass. My fear is that the threads will tear out of the tank after repeated removal.

I have also read that these early tanks break down after a while can cause engine failure by plugging filters, gascolator etc. Can anyone comment???

Adam Rigden

Kitfox V Outback

[efwd]

Hi Adam
On the SS7 the fiberglass is fairly beefed up compared to the tank walls. My fuel strainer threads in nicely and it didn't feel like it was stretching the fiberglass at all. I was concerned with removing the strainer since the number one rib is pretty close and may prohibit one from getting the strainer out. I then came across an Article in Kitplane magazine that suggested that strainers are not necessarily routinely removed for checking on a regular basis. I know someone here has reported pulling strainers annually that is how I come into the subject in the first place. Your 5 may not have come with the type of tanks we now have that are sealed some other way. I won't be removing strainers regularly.
Eddie

[jmodguy]

Adam,
I am also building an older Model 5 Outback (@ 1995) and the tanks were lined with Kreem. I have read several stories about this stuff delaminating from the tank surface whether it be metal or fiberglass.
I talked with John McBean a few months back and he told me they are using a different resin now which is more suitable for avgas so they no longer use a sealer.
I called Hirsch enterprises who market a slosh tank liner that is used by auto restoration community. He recommended that I strip out the old Kreem using a paint stripper safe for use on fiberglass. Its by Klean Strip and is called Aircraft Stripper for Fiberglass. Picked up a gallon at an auto parts store for $30. It's water clean up too. Once the tank is clear of the kreem, clean out the tank, and pour in the sealer and slosh it around. Pour out the excess and let it dry.
Or you can buy a new set of tanks for @ $900.00!

[Av8r3400]

For the record, my old plane had cream coated tanks. 1996-ish vintage.

I never had any peeling or problems with the cream. I used a mechanic's scope every annual to inspect them and never found an issue. I used non-ethanol contaminated auto fuel with an occasional shot of 100LL on long trips.

[pperry]

Not saying the paint stripper won't work, but Kreem is soluble in both acetone and MEK. I used the MEK because when I tested by putting some of the flaking kreem in a small container of each, it dissolved quicker and more consistently in the MEK, so I was able to slosh with the MEK and drain before it would soften the fiberglass too much. I then re-sloshed with Kreem thinned a little with MEK so that it would contact all the nooks etc in the tanks.
Paul Perry KF4 Speedster....kit was 90's vintage finished in 2001 by another person, the peeling Kreem was thought to be caused by the tank mfg not cleaning the release agent good enough before applying the Kreem.

[HighWing]

Lots of myths about Kreem. Yes there were some instances of peeling, but very few. My 900 hour experience with factory Kreemed tanks is exactly like Larry's. Release agent? That is on the mold surface of the tank - the smooth surface or outside, not the surface showing the fabric weave. Use MEK to remove the Kreem if you find it necessary. If it was me, based on my experience, it would be Kreem once again, but thinned as was mentioned.

[Floog]

My logic: You have two tanks feeding the engine simultaneously. It's very unlikely that BOTH strainers would clog up at the same time. If fuel flow slows/stops in ONE tank (not a life threatening event), then I would inspect the strainer(s). I often replenish JUST ONE nearly empty tank. In about half an hour, both tanks show equal fuel which tells me all is well with the strainers. If it ain't broke.....

[PapuaPilot]

I recently did my first condition inspection and decided to inspect the fuel tank finger stainers to see if anything had broken loose in the tanks. Doing was very easy. I made sure the fuel level was low enough to fold the wings back, which needs to be done anyway for the inspection. With the wings folded I removed the fuel drains and used a borescope to see the screens. The good news is both finger screens were perfectly clean. I don't think I will do this every year though, I just wanted to know if there was anything in there from the build. I bought the kit second hand and didn't do the Kreem application.

[jiott]

I agree with Floog, and like Phil's boroscope method of looking at the strainers if you feel a need. I am very leery about repeatedly removing and replacing fittings in a fiberglass tank, even the drain fittings. In my experience, what usually happens is the fiberglass threads slowly become expanded untill it is impossible to properly tighten the pipe threaded fitting. At that point you are relying on pipe dope of some kind to seal it up. One of my drain fittings in my brand new tank screwed so far in that I was concerned about proper sealing. So I certainly would avoid taking that one out unless absolutely necessary.

[TahoeTim]

You could scope them from the filler cap hole too. That's what I do on my vintage plane.