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Difficulty bending fuel line from tank to shutoff valve - RV-12iS

bsbarnes10

Active Member
Hi All,
I'm having a lot of difficulty getting one particular piece of tubing bent. On page 27iS-04 there is a template and instructions to bend the piece from the tank back to the shutoff valve. At the tank end there is a 38 degree bend that starts only 16.7 mm from the end of the tube. The instructions say to flare the end, then bend it (38 degrees), then slide the nut and sleeve from the opposite end of the tube. I've tried this a couple different ways and can't seem to get it right>

1. Doing it as recommended in the KAI - The sleeve won't fit over the bend in the tubing

2. Alternate method 1 - Flare the end, slide on the sleeve, then use my HF tubing bender. Problem here is that the sleeve is larger than the tubing so it won't fit down into the groove on the bender. I can get it butted right up to the edge and then roll the tube in the bender but then the bend starts further from the end of the tube (about 1/2" further) so it's not matching the template.

3. Alternate method 3 - Attempting to hand bend over wooden forms/table edges/etc. just flattens the tubing at the bend.


Any suggestions?

Thanks!
 
Hi All,
I'm having a lot of difficulty getting one particular piece of tubing bent. On page 27iS-04 there is a template and instructions to bend the piece from the tank back to the shutoff valve. At the tank end there is a 38 degree bend that starts only 16.7 mm from the end of the tube. The instructions say to flare the end, then bend it (38 degrees), then slide the nut and sleeve from the opposite end of the tube. I've tried this a couple different ways and can't seem to get it right>

1. Doing it as recommended in the KAI - The sleeve won't fit over the bend in the tubing

2. Alternate method 1 - Flare the end, slide on the sleeve, then use my HF tubing bender. Problem here is that the sleeve is larger than the tubing so it won't fit down into the groove on the bender. I can get it butted right up to the edge and then roll the tube in the bender but then the bend starts further from the end of the tube (about 1/2" further) so it's not matching the template.

3. Alternate method 3 - Attempting to hand bend over wooden forms/table edges/etc. just flattens the tubing at the bend.


Any suggestions?

Thanks!

Those tubes can be a bit of a pain. To do that particular tube, we have a modified flaring tool that can flare it close to the end with the sleeve installed on it.

If you are unable to get it to work and would rather have us fabricate it for you, send an email and we will be happy to do just that tube ala-carte versus the complete kit.

Happy building!
Steve

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Sand

Another trick. Fill the line with sand and hand bend it. Jusy make sure you clean it thoroughly.
 
Cut the sleeve

There is another thread that discussed this.One of the solutions was to cut the sleeve so that it just extended to the end of the flare nut. That makes it short enough to get over the 38 degree bend. That is what I did & it worked.
 
Cerrobend

Now if you need to make some radical or complicated bends in tubing. Gotta get you some “Cerrobend”. It metal that melts @158 Fahrenheit conversely it solidifies at @157 Fahrenheit, this stuff is like magic. Just melt some shavings from the ingot in a double boiler or a convenient heat source also heat and keep the tube above 158 degrees or the Cerrobend will set up before you get the tube full, use the kitchen stove at its lowest setting to keep the tube warm while filling (preferably when the wife isn’t home :D ) After you’ve filled the tube bend it anyway you want it will NOT collapse, in fact you can bend the tube so tightly that the outside radius wall will tear. Once you got it bent to your satisfaction warm it up and pour out the Cerrobend ( saving it as you can reuse it indefinitely)
 

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Bruce---The issue with hand benders is that the flare is extended out from the bend farther than the drawing or the template. So I took a hand bender---an Imperial 364, and modified it to get the flares closer to the bend. I cut a slot at the '0' mark and relieved the inside to allow the sleeve to rest. I also removed about 1/2 the sleeve tail, to where the tail just extends past the aft side of the nut. I took a AN832 bulkhead fitting and made a threaded 'mandrel' and turned some of the threads down on the lathe. This supported the tube against the fulcrum as it was bent.

In some cases, like the tube you are talking about, the flare is still to far from the bend. The solution was to move the flare closer to the bend. So I flared the tube, shortened the sleeve so it could pass around the tube bend, and made an internal mandrel to support the tube against the fulcrum during bending. Once the bend process was completed, I install the nut and sleeve to work on the other side. WE have a 3 axis CNC mandrel bender with some special dies we designed to to that now, but I still use the handbender for some prototype jobs.

OH---most of what I was bending was 5052O, 6061T6, and 304 and 316 Stainless, not 3003O that is provided in the kits. 3003O is soft enough to bend by hand if necessary.

Tom
 

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These are all some really fantastic replies, thank you!!

I'm going to start with a modified hand bender but may resort to some of the other options. The quick and insightful responses are much appreciated!
 
HF bender and HF clamp with one pad removed. You'll have to hold the clamp to keep it in place. A little Boelube in the trough of the pivot helps.
 

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I have been helping a STEM program build a RV12iS and they received the tubing shown in Post #2. It was really nice to have that group of tubing done by the pros. I’m sure the mentors and students could have had a lot of practice and redoes by trying those challenging tubing fixtures.

Just saying they were really nicely done and thanks for the support from TSFlightlines.
 
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