Hard 90s on the return line?

rmartingt · #1 01-18-2019, 04:38 AM

I've now spent 3-4 hours trying to package fuel lines in the wing root and all I have to show for it is a bunch of wasted tubing and a list of what won't work. Decided to change course and put the fuel filters in the middle of the line under the forward covers. It'll be messier to inspect/clean them there but it's easier to work there than in the wing root and there are fewer bends in the supply line.

The issue I have now is trying to get the return lines connected. With the wings on I can't put anything too crazy in place so I'm trying to work with what's there; I did a poor job locating the return fittings and what worked in my head isn't working in reality (which is why I like to work in CAD for these sorts of things).

The only viable way I can see to get something in place is to put some sort of separable union in the wing root. My thought was an elbow right after the line comes out of the fuselage, pointing forward. Then the return can come forward, up and out to the tank.

I'm doing everything I can to avoid hard 90s on the supply end, including a custom fuel valve mount solution, but I can't see any reason why one or two hard 90s on the return side should be an issue. Is there anything I'm not thinking of?

TS Flightlines · #2 01-18-2019, 07:01 AM

Bob---90*s are ok as long as they have sufficient ID to flow the amount of fuel you need.
Pics of your install would be great.
Tom

219PB · #3 01-18-2019, 07:11 AM

Hard lines are possible. Here are some pictures of my 6. I am told that the 7 has a little more room to work with. The key is to use 1/8" aluminum TIG wire to make a pattern and then bend the tube to the pattern. You can look at my Kitlog webpage to see more pictures of my fuel system. I ran most all of my lines with rigid tubing.

BillL · #4 01-18-2019, 07:20 AM

Quote:

Originally Posted by 219PB

The key is to use 1/8" aluminum TIG wire to make a pattern and then bend the tube to the pattern.

+1 .

rv7charlie · #5 01-18-2019, 07:20 AM

If your filter is prior to the selector, You'll have to make a decision on how you'll service the filter. Draining the tank just to change the filter won't be fun (or particularly safe). I elected to install a ball valve prior to the filter in that space, mounted so the handle can't be moved to the closed position with the kick panel in place.

I agree with Tom about 90s in the return line; there's no significant 'head' on the return line, and it's pressurized, not being 'sucked' on, like the supply to the pump.

Charlie

charosenz · #6 01-21-2019, 10:07 AM

Great thread, also, Paul thanks for sharing the picture, looks very nice.

The comments from people who have worked through this and related issues and are willing to post comments and pictures are very helpful, especially for those like me who are a few months behind in the process.

I have other related questions on the FI system but I will post them in a separate thread. (Don't want to hijack this one.)

Charlie

rmartingt · #7 01-21-2019, 10:18 AM

Quote:

Originally Posted by rv7charlie

If your filter is prior to the selector, You'll have to make a decision on how you'll service the filter. Draining the tank just to change the filter won't be fun (or particularly safe). I elected to install a ball valve prior to the filter in that space, mounted so the handle can't be moved to the closed position with the kick panel in place.

That's how I'm planning to proceed as well.

I managed to get my valve connected with lines going through the inboard cover supports, but now I've run out of ferrules and B-nuts. I have more on order from Spruce (oh, it kills me to order from them and pay shipping, since I can practically walk over there whenever we visit my parents... but I need them now!) and will pick back up from there.

I managed to figure out a trick to get (at least shallow) bends closer together, and Tom from TS Flightlines sent me a couple brilliant suggestions as well (I'll leave posting those publicly to him, if he chooses). I should be able to pull this off and may not even need the 90 fittings like I thought.

Whenever I get everything in and routed I'll post pictures here and in my build thread. In the meantime, I'm working on rigging some flight controls while my fittings are on the way. May take a detour and mount the empennage as well so I can rig the controls there, too.