Fuel foaming

[Emory Schroeter]

MessageI was reading an article today about glow plugs in Model Airplane News. The writer stated that adding Armorall (silicone) to your fuel was a kiss of death to your glow plug. He said, it will still glow brightly, but the silicone kills the chemical reaction on the coil. 

Emory. 
  ----- Original Message ----- 
  From: Fletcher, Richard 
  To: 'discussion at nsrca.org' 
  Sent: Friday, August 13, 2004 4:53 PM
  Subject: Fuel foaming


  I have heard that adding a capful of Amorall to a gallon of fuel eliminates all fuel foaming.

    -----Original Message-----
    From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org] On Behalf Of Rcmaster199 at aol.com
    Sent: Friday, August 13, 2004 4:52 PM
    To: discussion at nsrca.org
    Subject: Re: hopper theory & practice


    If foaming is your problem, then a bladder tank will likely help. If it is not, then there will be no change, real or imagined, for that reason. There could be other problems tho.

    Make little mistake: if the fuel is foaming, the pump will most likely cavitate and be of little use in fuel delivery. I have long suspected this to be a significant contributor to pump problems we have been reading, by so many of us.

    To solve fuel foaming, isolate the tank from the vibratory source as much as possible. Any fuel delivery system will benefit, doesn't matter if it's simple pipe pressure, diaphragm pump, cline regulator or pressurized tank

    MattK
      Any one using a bladder tank with their Webra 145 or 160?  Some poeple at the local fuel has started using them in sports plane for fuel related problems.  Seems to sovle thier problems.

      Randy
        ----- Original Message ----- 
        From: Wayne Galligan 
        To: discussion at nsrca.org 
        Sent: Friday, August 13, 2004 10:43 AM
        Subject: Re: hopper theory & practice


        There has to be more pressure(muffler tap) to the main tank then there is draw from the carb in order for this system to work properly.  Inertia can effect this as I stated in one of my other posts.  I proved this in my Prophecy that had the tank higher then the needle valve and when I pressed a hard negative "g" load it would go lean.  At all other attitudes it ran fine, i.e, uplines, downlines, snaps, positive maneuvers.  All up it has its merits but the best is that it reduces the possibility of picking up air in the main feed line and reducing the possible lean run or lean burp, something you don't want happening on a turbine or helo engine.  The hopper will reduce the amount of air that enters the hopper when the main pickup encounters bubbles of foaming.   The hopper pickup will still be in bubbleless fuel (fairly fuel tank) if the tank is isolated well enough. Jet and helo guys use then for this reason.  The other is if you are trying to move weight forward for a tail heavy airplane. This makes good use of the fuel transfer and extra tank instead of adding lead ballast.  I think the bladder tank(like the Tettra) is the best alternative to bubbleless feed and I am seriously considering using it.  

        Wayne Galligan

        - Original Message ----- 
          From: Jim_Woodward at beaerospace.com 
          To: discussion at nsrca.org 
          Sent: Friday, August 13, 2004 7:54 AM
          Subject: Re: hopper theory & practice



          I'll take a stab as why the hopper tanks work.  Liquid may be incompressible, but it is "movable".  The hopper tank has a fuel entry and exit point.  Exit point being the clunk line that goes to the engine, entry point being the vent line.  The hopper tank becomes a reservoir of fuel.  Although I think you can argue that the entry and exit point fuel velocity (or suction force) is the same, this cannot be said for the middle of the tank were the suction force is diffused over a larger volumetric cross section.  The image in my mind is a wind tunnel's stilling chamber.  I think an interesting question would be this:  How small can a hopper tank be to still provide the ease of fuel draw we are looking for?  Can the hopper tank
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