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Old 07-26-2017, 09:21 AM
Draker Draker is offline
Join Date: Jun 2016
Location: Livermore, CA
Posts: 97
Default Bill of materials for tank fuel return line(s)

I am not sure what my engine choice will be yet, but I think it would be a good idea to provision for a fuel return now while building the tanks just in case I need it later. I can always cap it off if I don't use it, correct? Does anyone have a materials list for these lines? I would assume it's similar to what's used for the vent, but larger:

* Some length of 3/8" soft aluminum tubing
* 6D flare nut and sleeve
* 6D bulkhead elbow and nut
* 6D spacer??

Since I'm planning to go dual flop tubes for fuel pickup, I can likely use the flare hardware already shipped with the standard wing kit, and only need to order the tubing and bulkhead hardware. Am I missing anything?

Is there consensus on how far to run the fuel return? Forum search shows some builders running it to the 2nd bay and some running it all the way to the most outboard bay. Is there consensus on which is better? I would think farthest from the pickup would be best, no?
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Old 07-26-2017, 09:39 AM
CubedRoot's Avatar
CubedRoot CubedRoot is offline
Join Date: Sep 2013
Location: Ooltewah, TN.
Posts: 543

I've been considering doing the same, since I am building my wings as well. I'd be interested to see what folks suggest for plumbing.
Lynn Dixon
RV-7 Slider -
Tail kit Completed - March 2017
Wing Kit Started - June 2017
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VAF Donation paid for 2017
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Old 07-26-2017, 10:20 AM
Bevan Bevan is offline
Join Date: Sep 2007
Location: BC
Posts: 1,538

My -06 return line enters the tank through the inboard end near the top of the tank. Inside the tank, the line continues outboard and makes a 90 deg turn forward (just before the first rib) where there is a T fitting about 2/3 from the rear of the tank. The forward (fuel goes straight through) port simply dumps fuel into the forward portion of the tank. Another -6 line is connected to the outboard side port which takes fuel to the outboard bay. This arrangement supports the tubing and fitting. Fuel is dumped into the first bay when there is headspace above the fuel (less than 3/4 full tanks). If the first bay is completely full, fuel takes the path of least resistance to the outer bay (in theory anyway) near the vent tube.

RV7A Flying
O-360-A1F6 (parallel valve) 180HP
Dual P-mags
Precision F.I. with AP purge valve
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Located in western Canada
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Old 07-28-2017, 08:26 AM
Draker Draker is offline
Join Date: Jun 2016
Location: Livermore, CA
Posts: 97

Thanks for the idea, Bevan. So you've got the capability to dump in both the first and last bay. What's the theory behind wanting to dump into the inboard bay first?

For completeness if anyone is actually using this thread to order parts, don't forget plastic snap bushings to go through the ribs: 5x BUSHING SB500-6 for 1 tank or 10x for both.
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Old 07-28-2017, 09:29 AM
Toobuilder's Avatar
Toobuilder Toobuilder is offline
Join Date: Jul 2009
Location: Mojave
Posts: 3,987

I just modified my tanks for the return line and dumped the return in the first bay. No bulkhead fitting needed this way, just use a standard AN union with a bulkhead nut on the inside.
WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

Michael Robinson
Harmon Rocket II -SDS EFI instalation in work
RV-8 - Flying
1940 Taylorcraft BL-65 -flying
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Old 08-04-2017, 12:36 PM
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jcarne jcarne is offline
Join Date: Jul 2016
Location: Worland, Wyoming
Posts: 493

I have just had to answer this question for myself and this is what I came up with. I am planning on attaching a VA-112 (which is for fuel testing drain) and inserting an AN816-6-2D into it. The fitting mentioned is supposedly supposed to go from 3/8" tube to 1/8" pipe thread which matches up to the threads on VA-112. The plan is just to cap the fitting unless I need it. I like this method as you don't have to worry about a bulkhead fitting spinning and causing a leak. I am also not concerned with going to a further bay as many people dump into first bay with success.
Jereme Carne
RV-7A Emp. done
Wings mostly done
Working on Fuselage
Finish kit on order
Exempt but gladly paying!
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