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.

[PapuaPilot]

I considered that, but there are baffles in the tanks and I couldn't see the finger screens. Feeding a bore scope through the baffling holes would prove to be challenging, not to mention the possibility of submerging the bore scope in the fuel.

[cirrusjetpilot]

You could the cheap borescope sold on Amazon. I have this one and use often

https://www.amazon.com/Endoscope-Depstech-Inspection-Megapixels-Smartphone/dp/B01MYTHWK4/ref=sr_1_1?ie=UTF8&qid=1489016598&sr=8-1-spons&keywords=borescope&psc=1

Alex

[jrevens]

It seems to me that if the strainers are anyway accessible/visible through the filler cap hole that it's much more desirable to do it that way than removing the fittings, for many obvious reasons. Draining the tanks, if necessary to protect the bore-scope, seems like much less work and much less problematic... just my opinion. Of course if they are clogged with something they would have to come out.

[jiott]

I can verify the strainers are not visible thru the fuel cap as Phil says. There is at least one if not two baffles in the way (on my SS7) and the holes thru the baffle are not large. I have been thru this drill with a boroscope when I stupidly dropped a fuel measuring gauge stick into the tank and was trying to see where it was. Fortunately it didn't slide thru the baffle hole and I was able to fish it out after several hours of frustration. To me a boroscope would only make sense if you removed the drain fitting because it is nearby and in the same baffle bay as the strainer.

[HighWing]

I am a bit confused here, but most likely because all my experience is with Denney Kitfoxes. I agree with those who are reluctant to remove fittings screwed into fiberglass. But, isn't the drain fitting screwed into fiberglass?

While I had my first Model IV, I removed the finger strainers for each annual - nine years worth. In those tanks, there was a Reducing Bushing screwed into the fiberglass tank and the finger strainer was screwed into that. I would hold the bushing in a wrench and remove the finger strainer without disturbing the bushing to tank threads. Are the new tanks designed to have the finger strainer screwed directly into the fiberglass?

As a side note, I only found foreign material once in all those annual inspections. It consisted of fairly large chunks of rubber consistent with what you might expect after an overhaul of an avgas fuel dispensing set-up. Nothing that would cause a problem given the fuel strainers, but definitely a likely issue with only a fuel port at the exit from the tank.

[jiott]

Yes Lowell you right, the drain fittings are also screwed into fiberglass. That's why I will continue to avoid removing them unless I feel a real need. What Phil and I were trying to say was that removing the drain fitting was the only practical way to insert a boroscope to look at the strainer without removing it.

I am open to correction here if I am wrong (its been 3.5 years since I assembled it) but I believe the finger strainer basket is attached to the bushing which screws into the fiberglass, and the 90 degree fuel barbed fitting screws into the bushing. If I am wrong and Lowell's description is correct for the SS7, that would be great-get the strainer out without disturbing the fiberglass thread.

[PapuaPilot]

Like Jim says, it is almost impossible to get past the baffles with a bore scope. The drains are right by the finger screens and made it easy to check them.

In my model 5 the wing drain fitting screws right into the fiberglass. That is why I am reluctant to do this every year. It would be nice if there was a threaded brass fitting put in there when the tanks are manufactured so we can remove the drains without worrying about ruining the threaded fiberglass.

FYI I used Fuel Lube when I reinstalled the drain fittings.

[jrevens]

Yes Lowell you right, the drain fittings are also screwed into fiberglass. That's why I will continue to avoid removing them unless I feel a real need. What Phil and I were trying to say was that removing the drain fitting was the only practical way to insert a boroscope to look at the strainer without removing it.

I am open to correction here if I am wrong (its been 3.5 years since I assembled it) but I believe the finger strainer basket is attached to the bushing which screws into the fiberglass, and the 90 degree fuel barbed fitting screws into the bushing. If I am wrong and Lowell's description is correct for the SS7, that would be great-get the strainer out without disturbing the fiberglass thread.

Yes, you're right Jim... at least my tanks are also that way. Not trying to be an alarmist, but that is one issue I thought about before and during installing my tanks. I wish I had given it more thought. I did think of enlarging the hole for the strainer assembly, tapping it for the next size larger pipe thread, then permanently installing a brass bushing with epoxy on the threads. Same with the drain valves, because the o-rings in those things usually have to be replaced sometime, which usually requires removing the valve. But then I decided that whoever designed these particular assemblies probably knew what they were doing, and that there was historical experience to verify that they were robust and proper. That may or may not be the case. It would be interesting to get an idea of how many flying Kitfox tanks constructed/assembled like this are out there, for how long, and what the experiences have been. That might (or might not) be comforting. :confused: I'm sure only a relatively small percentage of strainers have actually had to be removed for inspection. At least I would like to believe that.

[PapuaPilot]

I did think of enlarging the hole for the strainer assembly, tapping it for the next size larger pipe thread, then permanently installing a brass bushing with epoxy on the threads.

I thought about that too. What you describe here would be the repair to do if there is ever a problem reinstalling the drain valve. The only change I would suggest would be to use fuel tank sealant (PRC) instead of epoxy to glue the brass fitting in.

[Guy Buchanan]

Mine's like Lowell's- finger strainer into brass bushing into tank. I check yearly and use the 2-part polysulfide to re-seal.