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Bending fuel lines and installing AN fittings

F

FlyingDiver

Well Known Member
Just started work on page 27iS-04 (RV-12iS), fabricating the F-12127K fuel line. Step 3 is:

Measure 21/32 in. [16.7 mm] from the tank end of the tube and mark the end of bend line. Measure 1 5/16 in. [33.3 mm] from the tank end of the tube and mark the start of bend line.

Flare the tank end of the tube.

Make the 38° bend by referencing Figure 2, View A-A. Place the nut and sleeve over the opposite end of the tube. Slide the sleeve against the flare.
Click to expand...

First, I can't do a bend that close to the end of the tube with the bending tool I have. I've ordered a smaller one, but in the meantime I can just add a couple inches when cutting the tube, do the bend, then cut off the excess. Then do the flare. Not the order in the plans, but should that matter?

Flaring that close to the bend is just barely doable with the flare tool, but I managed.

I cannot slide the AN819-6D sleeve over the bend, when I start from the opposite end. Even with the 38 degree bend. Never mind the 90 degree bend.

If I slide the sleeve on from the bent end, I can't slide it far enough down the tube to get the flare done. It's a very short straight end on the part.

I've now cut and attempted to fabricate this part 4 times. All wasted. Good thing I have another roll of the tubing on order.

I don't understand what I'm doing wrong. Any hints?

joe
 
The sleeve is there to support the back of the flare on the tube when thightening the nut.
The back part of the sleeve can be grinded of in whole or partly.
Remove the amount of material that is required to get the job done, not more.
This does not degrade the strength of the flared connection.

Good luck
 
Avanza said:
The sleeve is there to support the back of the flare on the tube when thightening the nut.
The back part of the sleeve can be grinded of in whole or partly.
Remove the amount of material that is required to get the job done, not more.
This does not degrade the strength of the flared connection.
Click to expand...

I'm not sure how doing that solves the problem. What sequence of actions (cut, bend, flare, etc) should I do in this case?
 
Learning to work with aluminum tubing can be frustrating. The best advice is to simply buy an extra coil of it and practice on it until you're comfortable with it. I've plumbed a few airplanes now and I still end up making a lot of scrap pieces before I'm happy with the results.

When you need to do a bend very close to a flare, you're basically always going to do some form of: put the sleeve and nut over the tube, slide them out of the way, flare the tube, put the sleeve against the flare, and bend. As you noticed, a nut will go around a corner, but a sleeve won't. If necessary, I will allow the sleeve to contact the "finger" on the tubing bender, being careful to protect the flare and the shoulder of the sleeve. You can get the bend quite close to the flare this way.
 
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We cheat---we have this:

Tom
 

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I managed to get it done, basically by cutting the tube overlength then bending, then putting the sleeve and nut on, then trimming to the minimum required to get it into the flare tool. I ended up with longer "ends" (past the bend) than the plans called for, but it worked out.

Here's the first one installed, but it was the other end that caused me the grief.

I have a bending tool with a smaller radius on order.
 

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First off if you could recycle all of the aluminum tubing that I wasted learning how to do the bends you could make an entire new plane. It takes time to learn how to do the flares correctly and to get the bend/flare where you want it. It also takes some time to figure out how to use the marking on your bending tool to get the lengths you want.

There are some basic limitations for the short lengths unless you modify your bending tool (which I have done). In general it is better for what you are trying to do to do the bend first and then add the flare to the end. There is a minimum distance for the bend to the flare that is set by the length of the sleeve plus the thickness of your flaring tool plus a tiny bit. The sleeve has to be slid onto the end after the bend for short segments. Don't forget to add the nut too, but it can make it around the bend while the sleeve can't.

Do a search for modifying your bending tool. Tom had some suggestions on that a while ago. It involves notching your bending tool to clear the sleeve and making a mandrel to support the tubing while you are making the bend. With these modifications you can do the flare first and do the bend on short lengths.

One more thing. There is a mil spec for flaring diameter. I found this to be helpful to determine when I had a good flare. I don't recall the number now unfortunately. Do a search. Getting a feel for how much pressure is required to get a good flare takes some time too and it depends on the type of material you are using.
 
Joe and others----we make the 12IS tubes to help the builder save some frustration and in some cases, money. NOT to skirt any SLSA regs or the 51% rule. The tubes are made to the Vans specs by their templates found in the construction guides. WE know that some of the tubes are difficult to make for those that are not VERY proficient in tube fabrication. Yep I personally know this. Like you guys, I blew through a LOT of tubing making some assemblies using off the shelf benders.

Yes---there are some that require the flare to be closer to the bend than a "regular' tube bender can do. Thats why I modified one of my hand benders to be able to put the flare closer to the bend. I use these for prototypes, one-offs--and some custom creations. All the production tubes----like those for the 12IS and the RV14 are done on the CNC bender.

I personally dont think your DAR is going to know, or care, if you made the tubes or had someone else make them. Perhaps Mel can chime in here. Yeah the 51% and the ELSA rues put you in a box, but safety and reliability shouls come first.

Tom
 
It kinda went like this.....

Page XX-X Take a load of aluminum tube, waste half of it, buy some more, curse and swear.

Nah

Hey Tom, Mike here - here is 16 numbers and an expiration date - Crack on :D

There are times in the build that you reach out to super nice people who do super nice stuff at extortionate prices, but it's worth it......;)
 
FlyingDiver said:
I've seen your stuff on the website. If I could buy your product and still register LSA I might do it. But I don't think I can.
Click to expand...

If you’re building ELSA, the 51% rule doesn’t apply - you can build and sell ELSA for profit if you want. E-AB is, of course, governed by 51%.
 
Ironflight said:
If you’re building ELSA, the 51% rule doesn’t apply - you can build and sell ELSA for profit if you want. E-AB is, of course, governed by 51%.
Click to expand...

It's not the 51% rule that concerned me, it's the LSA "Build exactly to plans with all parts supplied by the kit manufacturer" rule.
 
WEll-----Vans doesnt supply the pre-bent tubes on the 12IS---or any other. They provide the aluminum tubing, nuts and sleeves, and have the builder/fabricator make them to the templates they provide. So who knows who builds them?

Tom
 
Good point. I've got most of the ones done that aren't part of the pump and filter assembly. Only the mongo 7' one left. Don't need the others until I get my engine. Might be in touch then.
 
Soft tibing

Vans tubing is soft. One method I use is to partial bend with a tool and then add a union and tighten the flare to the union and hand bend the remaining way closer to the end. The union keeps everything for warping and leaves the flare perfect for no leaks. YMMV
 
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Just for giggles---here are the short tubes. We use 5052O tubing with the springback adjusted to match the install. (5052O is stiffer than 3003O). Tubes F12127A and D can be done but are long tubes. Shipping in an oversized box is ridiculous, and the probability of them geting even more bent during shipment is real. We would leave the forward end unflared, so the tube can be installed through the stock snap bushings. Fabulous if the bottom skin hasnt been rivited on!!

Tom
 

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PilotjohnS said:
Vans tubing is soft. One method I use is to partial bend with a tool and then add a union and tighten the flare to the union and hand bend the remaining way closer to the end. The union keeps everything for warping and leaves the flare perfect for no leaks. YMMV
Click to expand...

I’ve done similar to make a bend close to the flare fitting. I make the flare on the straight tube, install the B nut and sleeve, and then temporarily install a bulkhead fitting on the flared B nut tube (straight or 90*). Holding that bulkhead fitting gives your the leverage to make the bend by hand close to the fitting without damaging the flared end with the B nut/sleeve already installed. I use a spring type bending tool to make sure I don’t end up with a kink:

https://www.lowes.com/pd/Kobalt-1-4...G736mhSj5PIvmGRFTNEaAj4ZEALw_wcB&gclsrc=aw.ds


Make the bend, remove the bulkhead fitting and you’re done.
 
TS FLIGHTLINES

I can ABSOLUTELY recommend TOM for quality of product AND unmatched customer service ! I personally have made my last fuel or oil line …..
 
Tom,

What is the reason your F-12127D tube can only be installed in an E/A-B or an E-LSA after certification? Is it because you need to add an extra bulkhead fitting that isn’t specified in the 12iS plans?

Thanks,
Mark
 
This is why flareless MS fittings are better if you can find them. The only place Boeing used flared fitting was the O2 system.
 
rv9builder said:
Tom,

What is the reason your F-12127D tube can only be installed in an E/A-B or an E-LSA after certification? Is it because you need to add an extra bulkhead fitting that isn’t specified in the 12iS plans?

Thanks,
Mark
Click to expand...

My guess would be because the SLA manufacturing needs to be per the approved plans, or the DAR won't sign it off. After it's built and flying, "owner supplied parts" are allowed for maintenance.
 
Mark---from our website,"The aft portion is the difficult to build portion with all the bends. We connect it to an included bulkhead pass through fitting and then the builder need only fabricate the straight rigid tube portion forward of the bulkhead. This tube can only be installed on an EAB aircraft during the initial build, or retrofit to a 12iS ELSA AFTER Airworthiness is received."

Tom
 
Tom---in addition to being somewhat easier to install, the flareless fittings were originally rated to 7000 psi---depending on the tube material. Basically a 24* cone compression fitting, it can be easier to install the compression sleeve and to flare a tube.
Yes you can find the nuts, sleeves and unions/adapters at various aerospace hardware suppliers. Generally more expensive than AN fittings. BUT---does make repairs easy.

Tom
 
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