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Fuel system design questions

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  • #16
    Wow, the fuselage flex is something I hadn't considered. That does change my opinion on using 2 bulkhead fittings.

    Comment


    • X'N
      X'N commented
      Editing a comment
      You'll find in most hard plummed fuel systems they will engineer a 1/2 loop if you will that will compensate for flexing and expansion/contraction changes.

  • #17
    Hi Guys,

    I think I have stared down the lower portion of the fuel system.

    I intend to mount the fuel valve on the plate just forward of the tubing cluster under the front floor board.

    I will locate the gascolator in a position similar to what Jared and Mark have mentioned. The gascolator will be suspended from the floor board (with doubler).

    I will cantilever the tee fitting just past the former forward of the front door. I penetrated the former so low that I will have to plumb the tee as a “Run Tee” with the stem of the tee pointed up. Then a compound bend to get below the floor board. Then on to one of the tabs supporting the former just aft of the exhaust tunnel for a cushion clamp support. Then on to the fuel selector valve.

    I have a couple of questions.

    1) Concerning the run from the tee to beneath the floor board, will the fuel line fall outside the kick panel?

    2) Will the flap handle lie right on top of the fuel selector?

    I still need to figure out how to make a 1.4 in. hole in the steel plate.

    Thanks,
    Wes

    Comment


    • #18
      Best hole makers I've found for steel are rotabroach cutters. They look like they came out of a mill when finished. You can get them in large sizes like 13/8" for instance. A little bit of grinding with a drum and you're there.
      David Edgemon RV-9A N42DE flying RV-8 N48DE flying Patrol #232 N553DE in progress ! Plans built.

      Comment


      • dedgemon
        dedgemon commented
        Editing a comment
        tool costs dont count 😊😊😊

      • Wes Ragle
        Wes Ragle commented
        Editing a comment
        I know that's right. I waste more time trying to use the wrong tool than I spend earning the money to buy the right tool :-) Rotabroach is on order.

      • Wes Ragle
        Wes Ragle commented
        Editing a comment
        David,

        Had to wait twice. Once for the rotabroach and once for a 1/2" chuck drill.

        Worked perfect!

        Thanks for the tip.

        Wes

    • #19
      If you get a low profile fuel selector, the flap handle will happily lie above it.

      Comment


      • Wes Ragle
        Wes Ragle commented
        Editing a comment
        Yea. I have the Newton 4 way. Looks like it will fit on the plate and just avoid hitting the exhaust tunnel.

      • Battson
        Battson commented
        Editing a comment
        Yes - that is the very same one which I have.

        The clearance is too close due to the vibration of the tunnel in-flight. By using the existing plate, I had to lift mine 1/4" with a packer. I used hardwood, light cheap and available. This was easily concealed under the floorboards.

        You could also solve the problem my mounting the valve facing backwards, but that is pretty unattractive. A simple packer was no trouble at all.

      • Wes Ragle
        Wes Ragle commented
        Editing a comment
        Thanks for the tip.

        Since I intend to burn auto fuel I am a little concerned about keeping the fuel temperature as low as possible. So, I'll add some insulation over the exhaust tunnel. That will further reduce clearance.

    • #20
      Guys,

      I now have a rotabroach cutter and tube bender so I can proceed with the fuel system. I still have a couple of questions.

      1) Exactly what is the routing from the tee, just forward of the front former, to the fuel valve (mounted on the plate just forward of the tubing cluster)? Do I cut through the floor skin while staying as close to the side as possible, or what?

      2) Since I intend to suspend the gascolator from the floor board just forward of the shock strut (I will use a doubler but still, not too stable), should I run flexible lines from the fuel valve to the gascolator and then from the gascolator to the firewall?

      Thanks,

      Wes

      Comment


      • Mark Goldberg
        Mark Goldberg commented
        Editing a comment
        1) Yes, you have it Wes. The fuel lines run under the floor and should go under the floor in an out of the way place that will not interfere with your feet or anything else.

        2) I am not quite following you here. Most people mount the gascolator aft of the fuel selector valve where it is the lowest point in the fuel system. Any water should drain there. The fuel lines come in from each side to the fuel selector valve, then normally aft to the gascolator, then forward to a bulkhead fitting on the firewall. Aluminum 3/8" lines are normally used for this. Forward of the firewall rubber made up lines are normally used because of the engine vibration/movement. Hope this helps. Mark

      • Wes Ragle
        Wes Ragle commented
        Editing a comment
        Hi Mark,

        Thanks, I'll just keep the fuel line as close to the side as possible.

        As for #2:

        The fuel selector will be on the steel plate. The fuel selector output will turn 180 and run aft, penetrate the stainless former and on to the gascolator. The gascolator will be suspended, via the 10-20 screw holes in the top, from the floor board back by the gear strut. The output of the gascolator will then run forward, back through the former and on to the firewall.

        Does that make sense?

        I'm just concerned about the flex of the floor board moving a gascolator with hard lines.

        Thanks,

        Wes
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