Newby question

[MotReklaw]

Hi,

I am considering the KF Sport package for my next project and have a question. Sometimes these questions are best answered in the flying community instead of asking the kit builder.

I understand there are two wing tanks and a header tank. What material are the tanks made of? Also, in reading the posts for the last few weeks, it seems there are problems with fuel flow.... Are these unusual problems? I certainly don't want to be concerned about whether the fuel is flowing smoothly to the engine....

(since I'm new here, I need to say that I am not trying to flame anyone, I'm just seeking information).

Thanks,
Tommy Walker in Alabama

[Dave S]

Tommy,

Every one of us was new to this at one time - And, IMHO - considering the fuel system is extremely important. Good question.

1) The current wing tanks are made of fiberglass - the filler cap is a steel neck and the outlet ports are threaded into the fiberglass directly. The header tank on the current models is behind the co-pilots seat with a fuel line running from each tank and a vent line for the header going to the right wing tank - header tanks are either molded poly or aluminum - you can get either.

2) I believe the fuel system, as designed, works just fine. There have been problems with mil-spec hoses swelling to create a restriction and, the lines from the wing tanks to the header tank must be all downhill to the header with no reverse loops to capture air bubbles and no kinks. Likewise, the vent line has to be all uphill & no kinks (basic plumbing - liquid flows downhill and air goes uphill) - if the build matches the design spec, I don't believe there will be any problems - just throw the mil spec hoses out.

3) If a person departs from the design specification - then you have to pay attention to determine if the modifications interfere with fuel flow.

4) Flying less than coordinated results in uneven fuel flow so one tank will show a lower fuel level than the other - that is an operational issue - not a design issue - Cruise in a kitfox requires right rudder pressure or an adequate rudder trim system. How do I know? - tried it - worked like that......

5) I did fuel flow testing on our kitfox - gravity and with the boost pump operating (boost pump is a modification to the design). Also experimented with fuel filters (also a design departure) between the wing tanks and the header tank, flow tested including running the tanks dry, didn't like the results and took the filters out.

6) Did some testing to see how nose down affects fuel flow and usable fuel - see attached photo - (OK - didn't land it that way - just dug a hole)

I believe the fuel system, as designed works fine.

Hope that helps some.

Sincerely

Dave S

[Dorsal]

Also, though the tanks are fiberglass the current ones are compatible with ethanol laced fuel.

[MotReklaw]

Thanks, that was my next question.

Are folks using rubber/plastic fuel lines or steel/aluminum lines for fuel?

Thanks,
Tommy Walker in Alabama

[Av8r3400]

Both, aluminum and flexible rubber/plastic, depending on the location and the need to flex.

[Av8r3400]

With fuel filters, remember that the flow from the wing tanks to the header tank is only via gravity and a minor blockage will stop this flow. The automotive paper filters will completely block very easily with only a small amount of water/ethanol contamination.

The flow from the header tank to the fuel pump is positive flow from the pump vacuum so this is the better (only?) place for a filter or Gascolator.

[MotReklaw]

Thanks for the replies.

Tommy Walker in Alabama

[kszaronos]

I too am a newby. I just bought a kitfox III. It had previously leaked fuel out of the co-pilot side wing fuel tank.

I had to put new lexonon the doors and clen-up the seating. Everything looks good now.

Question. I bought the very best fuel injection fuel line (black with the blue interior) to run to the metal fuel line running overhead on the pasenger side.

i want to conntect a piece of clear fuel betweenthe high and low sides of the fuel tank between the brass fittings to see how much fuel remains in the main tank. I noticed the the top brass fitting that I connect to coming out of the tank seems to spin a little up or down. It stops as it hit either the bottom or top of the wing.

It appears that maybe the previous owner tried to seal this with some sort of epoxy. This may have been where it leaked previoulsy.

I am not sure how to tighten this up? Is an epoxy the right thing for this or is there a way to get this tightened up?

I wouldlove a call form an experienced Kitfox owner. I have other questions. I livein Indianapolis.IN. 317-506-2854.

Thanks, Keith