K

Kimmer

I'm New Here
I must have some impairment that is unique to me. I haven't found anywhere in the forums where a 6A/7A/9A builder has had any real difficulty threading the 3/8" alu tube from the fuel valve to the tank. I find myself short on strength to push the tube through the S-turn from the gear mount and out the skin. Perhaps it needs to be a two man job?
Kim
RV 9A, soon onto the finishing kit
 
You are not alone!

Kimmer said:
I must have some impairment that is unique to me. I haven't found anywhere in the forums where a 6A/7A/9A builder has had any real difficulty threading the 3/8" alu tube from the fuel valve to the tank. I find myself short on strength to push the tube through the S-turn from the gear mount and out the skin. Perhaps it needs to be a two man job?
Kim
RV 9A, soon onto the finishing kit
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I speak only for myself, but I had a great deal of difficulty with that. I used those flexible tubing benders from Aircraft Spruce or comparable supplier, but it was a huge PITA,made me wish I had built the TD model. You may want to try removing the snap bushings so the holes are a little bigger, then slipping them back one when everything is in place. You can also slit them to take them off or on after the tubing is in place. Same for wires.
 
Tubing

Are you using the soft 'versa-tube"? That's the kind that usually comes all coiled up and you have to straighten it by hand.

The way I did mine was...

A) Using a piece a stiff wire (14 guage electrical wire works good) make a pattern for how the tubing should be bent in the area of the fuel selector.

B) Duplicate this with the fuel tubing. Cut, put nut and sleeve on, then flare. Leave the outboard tubing basically straight and leave it a little long for now.

C) Starting at the fuel selector, feed the fuel tube into the support holes (grommets on the tube but not in the holes makes it go easier). You may want to start with a slight arc in the tubing to make it go through easier.

D) Once you have it through, tighten to the fuel selector, and slide/snap the grommets into place. Then by using your thumbs gently push, pull, massage the tubing into it's final place around the back of the main gear weldments so it will not be touching any structure other than the grommets, and sticking straight out of the fuselage side. Trim/flare later.

E) Have a beer or advil (but not both) and repeat on the other side.

PS. You will have sore fingers for a day or so.

Bevan
 
Another solution...

... is to subdivide the problem into two simpler ones. I added a bulkhead fitting at the little support bracket instead of a snap bushing. The tubing on either side can be shaped, installed, or removed independently, and relatively easily.

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I usually found that if things seemed unreasonably difficult

I usually found that if things seemed unreasonably difficult it was time to stop and step back away from the task and not try to force it. Much time in the build process is spent thinking about how to do the immediate task correctly. Give it your full attention and think it through. Often a new tool solves the difficulty. I used a real tube bender to form my lines and I used bulkhead connectors to interface all lines at the wing to fuselage interfaces and the firewall interface. There is always more than one way to do the task and the problem is to find the best one for your application.

Bob Axsom
 
The divide-and-conquer approach another mentioned above works quite well.

First thing, order a bunch extra tubing (also the 1/4 for brakes). Your learning curve will consume it and you won't be tempted to salvage a poorly bent piece that should be discarded.

I use straight bulkhead unions on the brackets next to the selector. You'll have to figure out the runs for the individual tubes to fit your selector (and possibly pump). But at least they're short pieces. The little outer bracket will be captured on the completed outer tube. (I can speak for only t'draggers; the nose draggers will present more difficulty with the gear mounts.) Also, the lower hole in the little bracket is not aligned with the hole in the inner bracket as punched, as you can see in the posted picture. I drill a fresh hole in line with the inner bracket to keep the tube straight. (Nose draggers may vary here, also. Another good argument for T over N draggers!:D).

John Siebold
 
I had a very hard time getting these things to fit. So I didn't! I ended up buying about 4 feet of stainless steel flexible fuel line and the AN fittings from Pegasus Auto Racing's website. It took me awhile to figure out how to build a fuel hose correctly, but aside from that, it only cost about $50.

I've had the lines in and out a few times during the build and it is SO much easier to deal with. Thanks to Roberta Hegy for the Pegasus tip!
 
I had the misfortune to do it twice, on the same plane. The second time I used some oil on the outside of the tubing to make it slight easier thru those snap bushing. It made a huge difference. I pre bent and flared the side of the fuel valve and ran it some what longer on the tank side. It worked much better with some lubrication on the fuel line. Also, I would stay with the hard line as flexible lines have limited life and you will have to go thru this process in a few years.
 
Worked from Outside in

It's been awhile and it wasn't easy but I did mine working from the outside. I used the spring type tube bender in a few spots but mostly just worked the tubes by hand threading through the gear towers, etc.

I put the rubber grommets (2 per side) in place, put a little lube on the lines to make it easier to push through the grommets. I threaded the lines through the snap bushing but did not put the bushing in the ribs until I was done.

The first one was slow going but the second went much faster. I did all the flares after the lines were installed.
 
Bavafa said:
I would stay with the hard line as flexible lines have limited life and you will have to go thru this process in a few years.
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The steel braided teflon hoses do not have any service life limits. I think rubber-lined hoses have a five-year service limit (seven year shelf life).
 
Absolutely, positively much easier and less headache to use flexible teflon/steel braid lines. I put in the Al lines and was never happy with the potential for chafing on the gear tower, and the difficulty getting them to fit the fuel valve without stress (I have an Andair valve and its in an unusual position as well). The flexible lines are, in my opinion, much better on both counts. And they're not that expensive.

greg
 
Greg Arehart said:
Absolutely, positively much easier and less headache to use flexible teflon/steel braid lines. I put in the Al lines and was never happy with the potential for chafing on the gear tower, and the difficulty getting them to fit the fuel valve without stress (I have an Andair valve and its in an unusual position as well). The flexible lines are, in my opinion, much better on both counts. And they're not that expensive.
Click to expand...

I ran my aluminum tubing through clear plastic tubing, in the area of the gear towers, and any other spots for potential chafing. Personally, I prefer the aluminum tubing...........with bends from a tubing bender. My lines for fuel & brakes look a bit like artwork as the run along the left side of the cockpit/fuselage (RV6A).

L.Adamson --- RV6A
 
The RV-10 does something similar to the photo's below.

From the wing tank it goes into a bulkhead fitting (90 degrees in the case of the -10) and then a second piece to the fuel valve.

The original plans had a full run from tank to valve, however it was simply too challenging to run. So Vans later revised the plans to include a bulkhead fitting.

Phil


roee said:
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Sometimes an alternate route is ok

I used an alternate routing which was much easier to install:
RV6A419AlternateFuelLineRoute2.jpg

I have the Classic aero interior so all this is covered and protected.

I am in the hard line camp for this area. To much potential for relative movement with the flexible lines for my comfort.

Hans
 
I think that most of us who have built the 9A have struggled with this part of the build process. I know I went thru a BUNCH of tubing before I got it to my satisfaction. One thing that seemed to help me was to have all of the braces and the gear weldments LOOSE while I was trying to thread the tubing. That is, some of the screws and bolts were in place but loose enough so that there was some movement of the weldments and the braces. That seemed to give me a little leeway in snaking the tubing thru the various openings.
If any of the tubing between the tank and the fuel valve ever needs replacing I believe I will go the flexible hose route as well even if I have to replace the hoses periodically.
Just be sure that you don't have any bend that is too sharp where there could be kinking of the tubing and check carefully for any possible sites of chafing.
Keep your cool and if it gets too frustrating then back off for a while and work on another part of the build.
Good luck!

Peter K
9A 250 hrs
 
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