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-   -   Fuel return lines. Don't make this mistake (https://vansairforce.net/community/showthread.php?t=122839)

Bluelabel 02-16-2015 01:19 PM

Fuel return lines. Don't make this mistake
 
So, last week, we discovered our first major BOO BOO....
In starting to plan for attaching the wings, we were noting how we wanted to connect the fuel lines, i.e. make a piece of tubing, get hoses made etc...
Since we are going with the EFII Fuel Injection, we off course need a full return line into the tanks since it runs much like an automotive loop. Our fuselage had the return lines already plumbed when we got it since he was gong to put a Subaru in it. So we just had to plan on it for the tanks.
As it turns out, we placed the return line to the tank right where it will be in the way of the main spar... OUCH!!!
How could we have done such a bonehead thing you ask? Well, return lines are not part of the plans and it was one of the first times we had to make a decision as to where something would go. We picked a spot far from he fuel pickup but somehow didn't account for the spar....
After sulking over it for 30 minutes feeling like an idiot, and looking up every known adapter and fitting in existence, we came to the conclusion that the only fix is to bite the bullet, cut into the tank at the end, remove the the bulkhead fitting from the inside (as it was put in), seal it up, put in a new one, then seal the tank back up.... not looking forward to it.
I've been having dreams (well nightmares) that the first time we put fuel into the tanks that, even though they passed all our tests, they for some reason are going to leak like a siv. Maybe my subconscious knew what we did.....




The worst part.... 1/2" further out and we'd be fine.....
In the immortal words of Homer Simpson..."DOH!!"



majuro15 02-16-2015 05:44 PM

Man, I think I made the same mistake. Didn't even think about it. My return fitting is about 1 1/8" away from the wing spar, which I don't think is enough room to fit the front bulkhead spar in there and be able to thread a hose fitting on it. I may have to pull the bulkhead spar down from storage and just see.

Reading the plans, the thicker of the two fuselage spars goes towards the leading edge, correct?

Bummer. :(

Bluelabel 02-17-2015 02:46 PM

Quote:

Originally Posted by digidocs (Post 959832)


Hmmnnn...

Yup..... Guess I'm not the only one.....

Our tanks have been attached to the wings for almost a year.... Decided the best thing is to take them off and go in from the back... Nice clean hole that will be easier to get good seal on.

majuro15 02-17-2015 05:59 PM

I'm thinking for those who need to fix this, would it be feasible to remove the fuel sender unit and get access through that hole? I know it's tight and would require small hands, but it'd save cutting a new hole in the tank.

I plan to remove the fittings this way and patch the wrongly placed hole from the outside. Then relocate the fitting. If planned out properly, I think I can accomplish it without too much extra work.

John, separate question but do you have a source for the electrical connectors you are using? They seem like a nice solution.

Thanks!

jc11378 02-18-2015 07:51 AM

Quote:

Originally Posted by majuro15 (Post 960271)
I'm thinking for those who need to fix this, would it be feasible to remove the fuel sender unit and get access through that hole? I know it's tight and would require small hands, but it'd save cutting a new hole in the tank.

I plan to remove the fittings this way and patch the wrongly placed hole from the outside. Then relocate the fitting. If planned out properly, I think I can accomplish it without too much extra work.

John, separate question but do you have a source for the electrical connectors you are using? They seem like a nice solution.

Thanks!



Wow looks like I am in the same boat. I installed the BNC connector for my capacitance fuel quantity indication system in the same location. I will have to see how the center wing spars fit. I am hoping they just clear. Or I will have to cut holes in the rear baffles and install new ones. Man what a pain.

TFeeney 02-18-2015 08:32 AM

Sticky for -10?
 
Seems like enough people have done this - could we add to a sticky list of gotchas?
Doing a search only showed an RV14 gotcha sticky.

In my build, I've used Tim Olsen's list considerably for the RV10, but think this might be good to add to VAF.

Bluelabel 02-18-2015 09:46 AM

Quote:

Originally Posted by majuro15 (Post 960271)
I'm thinking for those who need to fix this, would it be feasible to remove the fuel sender unit and get access through that hole? I know it's tight and would require small hands, but it'd save cutting a new hole in the tank.

I plan to remove the fittings this way and patch the wrongly placed hole from the outside. Then relocate the fitting. If planned out properly, I think I can accomplish it without too much extra work.

John, separate question but do you have a source for the electrical connectors you are using? They seem like a nice solution.

Thanks!

I don't think the hole where the Sender goes is big enough. Not even for a tiny hand....

As for the connectors... they are Weather Pak. I think I got them from a combo of Amazon and Waytekwire.com. They come in a combos of 2-3-4-6 and you can just get the pins for the right gauge wire. Combined with some heat shrink they work really good.

majuro15 03-01-2015 03:39 PM

Okay, I gave it a shot last night and am happy to report that with proper planning and plenty of patience, it is possible to remove the ill placed fitting through the fuel sender hole.

I removed the fuel sender being careful to not strip the screws since they had proseal on them. I then safety wired my adjustable wrench to the front spar so I wouldn't lose it forever in the tank. I preadjusted the wrench and snaked it in the tank. Using a magnet extension wand, I was able to manuever the wrench into place on both the tubing flare nut and the bulkhead nut. Then I just tipped the tank on end to get the nut and small length of tubing I had attached to the inside nipple.

All this took me about 30 minutes and tired out my two fingers that I was able to fit in the hole, but in my opinion better than cutting a hole in the tank.

Next step is to patch the original hole from the outside using some AD41H rivets and a small patch and then relocate the AN fitting towards the leading edge on the other side of the vent fitting.

JDanno 03-02-2015 12:45 PM

You guys aren't the first nor will you be the last! How do I know.......?? :p

clutch22 03-02-2015 12:56 PM

I need school'd on fuel systems. I guess I didn't plan out my fuel system selection ahead of time and have been putting it off. (My QB wings are all sealed up.)

I'm wondering if it is possible to retrofit a fuel return to my tanks if I go with EFII. Does the return line need to be plumbed all the way to the outboard end of the tanks so that the fuel in the tank doesn't have pressure against the returning fuel, or does it have enough pressure to just dump it in at the inboard tank rib?

Sorry if this is a dumb question. :confused::)

P.S. I hope I'm not changing the subject too much on this topic. I just thought if it is possible to retro-fit, then I'm sort of in the same boat you guys are in except I dont have an existing interfering fitting/hole in my rib.

Thanks!


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