.

   The purpose of mounting the vent on the inboard side is that there is nothing in the way to turbulate the air flow and it gets a clean shot at incoming air. Nothing wrong with your over flow set up. If the model design and room allow, I drill two 1.8" holes through the fuselage for the vent and over flow fuel lines to attach to. The vent goes in from, and the over flow points straight out of can be bent to face downward and is plugged after filling the tank. If the space is limited like on a short nosed model, I just solder the tubing to a length of brass strip, and attach it to the top of fuselage in the same configuration as I mention before, and just c to the proper locations on the tank with fuel line. This just makes fueling the airplane so much easier when you get older and have arthritic knees!!

  Type at you later,
  Dan McEntee

If you want to AVOID the  airflow affecting the uniflow vent, hide it in an area of the model not exposed. Like in behind the engine or someplace. The vent does NOT need to be inboard of the tank to work properly. As soon as the amount of fuel that is inside the vent line at the beginning is consumed, the uniflow action starts, and it makes no difference where the free end is located, other than as it is affected by the airflow itself.

(Oh, boy! Off into the world of "stunt physics"!    )

If you want to AVOID the  airflow affecting the uniflow vent, hide it in an area of the model not exposed. Like in behind the engine or someplace. The vent does NOT need to be inboard of the tank to work properly. As soon as the amount of fuel that is inside the vent line at the beginning is consumed, the uniflow action starts, and it makes no difference where the free end is located, other than as it is affected by the airflow itself.

(Oh, boy! Off into the world of "stunt physics"!    )

    So, you skipped your Dale Carnegie meeting this week?

     The reason you want it inboard it is to avoid the possibility of air flowing in one side of the tube and fuel out the other side. This rarely happens but when it does the fuel comes streaming out - and the uniflow effect is defeated.  The issue is that surface tension may not be enough to keep the tube wet across the diameter, even in a 3/32 ID tube. You could use smaller tubing (it takes very little air flow to keep the pressure constant - like 6 ounces in 7 minutes) but then it's much more difficult to use it as the fill tube.

Same thing can happen with a "perpendicular" intake tube (that is, the end of the tube perpendicular to the airflow), but  is much more prone to happening when you have the vent on the inboard. Putting a bend in the tube also greatly reduces the chances of this happening. But in the simplest case, you hypothetically could just poke a hole in the wedge and it would hypothetically have the uniflow effect, however, it almost certainly will not work in practice.

  In any case, you want the intake end of the uniflow vent *above* the top surface of the tank (to prevent siphoning before you start the engine) and *inboard* of the tank to greatly reduce the possibility of the dual flow scenario.

     Brett

     

    Put on blanking plug with a cross-drilled hole, about #50 drill, for a vent. That makes it a net neutral pressure.

    Brett

Blanking Plug hey? I had to google that one. And still cant visualize how it looks or is attached to the the vent.  Would it be removable to let you fill the tank, and then attach the blanking plug to the uniflow vent with a piece of fuel tubing? Is the blanking plug just a piece of copper or brass tube capped off and it has a #50 hole drilled through the cross section of the tube?

Thanks Motorman.