Adding return line to QB tank?

[digidocs]

Hi there,

I'd like to add a fuel return line to my quickbuild fuel tank. I thought I remembered seeing a thread on this once, but I can't seem to find it. Does anyone else remember it or have any good ideas on how to procede?

The tank is on the bench.

Thanks,
David

[Mike S]

I did this on my 10, pretty easy if not on the plane.

After looking at everything I decided to put the return line right above the big hole for the fuel sender.

Drilled and deburred the hole, then used a piece of electrical wire through the bulkhead fitting, tied a knot half way in the wire. Fed the wire up into the tank through the sender hole, and back out the hole the fitting was to live in. The wire let me pull the bulkhead fitting into place without any problems.

The wire was long enough to have the tail hang out the fuel sender hole, and I was able to remove it after fitting the washer and nut on the bulkhead fitting.

I did a dry run first just to make sure it would work, then got out the pro seal and got it in pretty easy.

A piece of strong string would work instead of the wire, I am sure.

Sorry, dont have any photos.

[ctbecker]

My return line goes thru the ribs to the most outboard bay to ensure that the warm fuel returning from the engine mixed well with the remaining fuel in the tank.

[rleffler]

It may not have to go to the tank......

I have a AFP purge valve that runs back to a tee in the tunnel from the right fuel tank. The tee is in line between the fuel valve and the tank.

To purge fuel, I just set the fuel selector to the left tank, turn on the pump, and the hot fuel goes back into the right tank.

Much easier that running a line all the way back to the tank.

[airguy]

If it's just the purge quantity from the AFP purge line, I would tap it into the supply line of the boost pump. If it's constant return and it needs to go to the tank, the way I did it was to remove the access plate on the tank, drill another hole in it where you want it, and I ran a piece of 3/8" line a couple bays deep in the tank to avoid foaming/splashing the fuel in the same bay where the pickup is. I just made a loop of safety wire through a hole in the bottom of the rib holes in the tank ribs (I was only able to reach 1 rib deep), and passed the 3/8" aluminum line through that loop as I put the plate back on. That will keep it from moving around during flight.

[ppilotmike]

What type of engine setup would require such a return line to the tanks? (I'm thinking diesel?)

[digidocs]

Hi guys,

Thanks for the replies thus far. I'm adding the continuous flow returns to each tank to allow me to use a recirculating fuel system with mogas. Although the diesel would be very cool!

It sounds like a standard bulkhead fitting and proseal is the way to go. I like the idea of extending the tube internally to get the return flow away from the intake, too.

David

[RVbySDI]

Originally Posted by airguy

If it's just the purge quantity from the AFP purge line, I would tap it into the supply line of the boost pump. If it's constant return and it needs to go to the tank, the way I did it was to remove the access plate on the tank, drill another hole in it where you want it, and I ran a piece of 3/8" line a couple bays deep in the tank to avoid foaming/splashing the fuel in the same bay where the pickup is. I just made a loop of safety wire through a hole in the bottom of the rib holes in the tank ribs (I was only able to reach 1 rib deep), and passed the 3/8" aluminum line through that loop as I put the plate back on. That will keep it from moving around during flight.

I have the ECI fuel injection that requires fuel return lines. I plumbed mine through the Z-brackets on the rear baffle and all the way back to the outboard bay. However, if doing it again or doing a retrofit on an existing tank I would be inclined to do what is described above. Penetrate the end plate with a bulkhead fitting and then run a tube through at least the first interior rib of the tank up high on the rib. I cannot imagine why this would not work well.

Originally Posted by ppilotmike

What type of engine setup would require such a return line to the tanks? (I'm thinking diesel?)

My ECI fuel injection setup umps more fuel through the mechanical fuel pump than the engine can burn so the excess flow is returned back to the supplying tank.

[F1Boss]

You can rivet the same fitting that is used to attach the quick drain to the outside of the tank where needed, and attach the return line there. Put grease on the drill bits when drilling holes to catch the alum bits. Rivet with sealed end pull rivets. Form-a-gasket #2 can be used as the sealer. Piece o cake!

A bulkhead fitting can turn when the line is being attached - very bad juju.

Carry on!
Mark

[chaskuss]

Originally Posted by airguy

snipped the way I did it was to remove the access plate on the tank, drill another hole in it where you want it, and I ran a piece of 3/8" line a couple bays deep in the tank to avoid foaming/splashing the fuel in the same bay where the pickup is. snipped

Did you install snap bushings or some other method of preventing the return tube from chafing on the ribs?

Charlie