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Bending Technique - Fuel Pipes

n4322b

Active Member
Having tried various bending tools and techniques as well as consuming significant lengths of piping, short of filling the pipe with sand or similar, I'm still unhappy with the result.
Fuel piping on the 7 seems designed to remove the last of my hair, and my knuckles so that I'd appreciate if anyone can point me to past threads (i have searched) that help ?
or indeed techniques that are adaptable to the multiple bends in the 7 ?

Thanks
Ian
 
for most bending, I used the slide over springs that keep the roundness during bending. They came with a pipe flaring kit. For tighter radius bends, I used the hand held bending tool. You can get them at harbor freight.

Larry
 
Ian---tell us what part you are having issues with.
Actually the 3003O that Vans supplies is pretty easy to bend, even by hand.

Tom
 
You mentioned multiple bends……are you having trouble getting a length of tubing to connect properly after it requires several bends?

A way to help with this is to take a coat hanger or a piece of welding rod and bend a template in it that replicates the bends/fit you need. Then make your bends in the tubing to match.
 
the runs out to the wings are one issue with the multiple bends and the second is the andair suggested bend to connect between their fuel valve and their filter on an andair fuel pump.

For the andair issue - I can't seem to get enough pipe to bend whilst allowing enough to then later flare the pipe for the fittings.

For the main runs out to the wings my bends are poor and show some slight constriction in places.

Hand bending didn't work for me. I tried a cylinder or larger diameter, a small bending brake type tool and eventually had more success with a plier type tool having a central die and two outer rollers.

I haven't tried a bending spring but as pointed out the tube is pretty soft.

(Another slight issue was inserting the snap bushings after routing the pipe through the brackets, even after splitting the bushing it won't press in with the pipe in situ)
 
I could show you my scrap pile. I just considered it a steep learning curve, and bought plenty of extra fuel line.

For that little joggle on the end, between the filter and the pump, I started the bend just enough so that I could still get the ferrule past it, then put the ferrule and B-nut on and finished the bend by hand. It took a little doing, but it can be done!
 
I could show you my scrap pile. I just considered it a steep learning curve, and bought plenty of extra fuel line.

For that little joggle on the end, between the filter and the pump, I started the bend just enough so that I could still get the ferrule past it, then put the ferrule and B-nut on and finished the bend by hand. It took a little doing, but it can be done!

i gave up and tried steel braided teflon but im not happy with that so I might go back and try again.

Thanks
 
I use one of these. Works well.

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Dave
 
Gave up

I gave up on these multi bends from wings to fuel valve. Here is what I did instead. A few more connections, but there is no pressure here so dont expect any leaks.
 

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Ian---you have chosen the Andair pump and filter with the "J" tube. Yep pretty tough to do---
See the pic---stainless tube at the discharge side of the valve. YES IT CAN BE DONE, even with out a 3 axis CNC bender. I build a few with a hand bender and flaring tool. Didnt say it was easy, we now do them on the CNC.

Tom
 

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There is a mathematical formula that one can use to make incredibly accurate (multiple) bends in tubing. We had to do it in A&P school but I think it can be found in AC 43.13.1B. It takes time to lay it out but the results can be really satisfying. Obviously, one needs to have the proper bending tools - no need to fill anything with sand or any of that old-school stuff.
 
I gave up on these multi bends from wings to fuel valve. Here is what I did instead. A few more connections, but there is no pressure here so dont expect any leaks.
John, I did the same. Works fine, and is much more maintainable. The long tubes with crazy bends that you can barely get in when the aircraft is in your workshop will be really hard to replace in the field.
 
John, I did the same. Works fine, and is much more maintainable. The long tubes with crazy bends that you can barely get in when the aircraft is in your workshop will be really hard to replace in the field.

I was trying to avoid those extra connections. Another builder I know in UK has done the same and it seems the simplest now.
Ill get my inspector to look at the current result before scrapping it I think.

Thanks for all the suggestions
 

Yep - I tried one of the harbor freight variety. I had to chamfer off some of the grooving to avoid it damaging the pipework. The limitation of the tool seems to be the length of free pipe to sit under the stop.

Below is the tool I managed with best of all but still not satisfactory.

https://www.amazon.co.uk/Brake-Bend...s=bending+machine+pipe&qid=1632049026&sr=8-14
 
We didnt like the long tubes with bends to the wings either, and the possible issues with installation. So for the Andair 7T valve, make these. Rigid tubes at the valve that transition to teflon hose. Have done these for years.
Those with the Vans brass valve can use a 90* hose end on each valve side, and then hose. Beats a bunch of bends, and maybe even several unintended ones made during the installation process. With really good understanding of the plans intention and preparation, you can install the rigid tubes.

Tom
 

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We didnt like the long tubes with bends to the wings either, and the possible issues with installation. So for the Andair 7T valve, make these. Rigid tubes at the valve that transition to teflon hose. Have done these for years.
Those with the Vans brass valve can use a 90* hose end on each valve side, and then hose. Beats a bunch of bends, and maybe even several unintended ones made during the installation process. With really good understanding of the plans intention and preparation, you can install the rigid tubes.

Tom

That's neat !
 
Embrace the suck ... ! You can do it
 

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Dinner

All of a sudden I feel like having spaghetti to tonight for dinner

PS looks like two lines are touching from the pic. better check.
 
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I'm not going to flame Bill's bending capabilities. With a stock type bender, you just cant get enough space between bends, and flare the tube close enough to the bend. Thus, tubes that appear long between bends, and fairly long drops from the bends to the flares. Thats just the nature of the stock style hand benders. Yes we fought that too. We found an answer before the CNC bender and flaring machine, that works well, especially for prototyping, or single bends.

I've posted pics of my hand bender here before, so I wont do it again. To flare a tube pretty close to the bend, without the big flaring machine, I use a Rigid RFT 37 tool from Genuine Aircraft Hardware. I have relieved the aft side of the flaring bar to accept a 90* bent tube, to be able to flare it close to the bend. Our flaring dies for the Olsen machine at our production shop is this way, and works very well.

Normally, when doing a quick job or a prototype, I'll flare the tube first, then bend it. Had one the other day that we needed to shorten the drop on a previously bent tube. Thus the flaring bar modification.

Tom
PS====thats hose you can make the "J" tube from the Andair valve to the Andair pump/filter on the RV7s using the Andair pump to fit under the stock covers.
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I used a handheld bender and some creative flare / bend sequence to make it all work. I'm more comfortable with hard lines whenever possible in places where there is no movement, thought it was worth the effort.

and no, nothing touches, 1/4" clearance at the closest point. Just hard to show in the photo.
 
I've posted pics of my hand bender here before, so I wont do it again.

I’ve had a search but can’t seem to find it - would you mind sharing a pic of how you relieved the tool for the sleeve / nut?

I have an Imperial 470FH which came with my tool kit - but haven’t used it as yet. Got my fuselage kit coming later this year - never done any tube bending whatsoever - would appreciate it if anyone had a basic 101.
 
double flare

I’ve had a search but can’t seem to find it - would you mind sharing a pic of how you relieved the tool for the sleeve / nut?

I have an Imperial 470FH which came with my tool kit - but haven’t used it as yet. Got my fuselage kit coming later this year - never done any tube bending whatsoever - would appreciate it if anyone had a basic 101.

Hi Trent, if you have not yet done any flares, you might want to look at this. Everyone will tell you that it's not needed, but boy, are the flares nice.

https://www.mastercool.com/product/72480-37-flaring-double-flaring-hydraulic-tool-kit/

https://vansairforce.net/community/showthread.php?p=768961

They are kind of expensive, and perhaps one of your other building buddies has one you can borrow. If not, buy one and lend it to others to recover the cost.
 
Embrace the suck ... ! You can do it

Granted that Vans said "there are many ways to tackle the issue" you've done a great job in that regard. Almost saleable as artwork !

I like the slotted brackets. I wa=s pondering whether the 14 clip on brackets might be adapted too.
 
a nexus area . . .

Embrace the suck ... ! You can do it

Nicely done, Bill!!

Now for your next challenge in this area/space, route the wires under the fuel pump plate, through the spar, and enlarge a new hole. :D

It's a challenge to get the keep wires under the fuel pump plate away from the 3D puzzle but it can be done.

This is a nexus area and should be noted on the drawings like an hot spot on taxi diagrams. "warning, think ahead"
 
Here it is and just so happens to have the my original prototype of the Andair "J" tube for the Andair pump.

Tom
 

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Just buy a nice hand bender. Cheap tools will give you cheap results. The good Imperial lever benders are around $120. BUT they produce very good results.
The triple benders, like the Imperial 470 are good for thinner wall tubing, and different sizes. But dont get crazy with them---yeah I BROKE one----completely my fault---trying to bend .065 wall 3/8 stainless.

You can get an inexpensive bender, a good one, or a really good one.

Tom
 

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