Where to Learn About Fuel Line bending and Fitting

[Gusmax]

You might already know that automotive flares are 45 deg and JIC/aircraft flares are 37 deg. Therefore you cannot use the flaring tools from HF.

[Saville]

Originally Posted by Gusmax

You might already know that automotive flares are 45 deg and JIC/aircraft flares are 37 deg. Therefore you cannot use the flaring tools from HF.

I do already know that and I own an aircraft flaring tool (Rolo)

Doesn't hurt to mention it though.

Thanks

[BobTurner]

When it comes to bending 90 deg, my bending tool came with very explicit instructions for initial length vs final (up-right) lengths. Or, you could do the math.

[Saville]

Originally Posted by BobTurner

When it comes to bending 90 deg, my bending tool came with very explicit instructions for initial length vs final (up-right) lengths. Or, you could do the math.

I have read that even with quality bending tools there can be a slight flattening of the tubing. And there has to be some stretching I would think. I would think that trying to get an accurate value by math would be difficult. But maybe I'm wrong.

[BobTurner]

My observation is that the outside radius does have a small amount of stretching/flatening. But the inside radius is slightly compressed/flattened as well. They seem to average out!

[TS Flightlines]

Gregg---alot of this is just practice, and knowing what your equipment does. Not a rule of thumb, but a pretty good quide is to cut your tube +- .180 long. That will allow you to square the end of the tube, and flare it with a +- .090 .
Take a piece of scrap tube that you have and bend it to the desired shape and flare one side so it will fit. See how much too long it is on the other side, and know what your flare bar will do, give yourself +- .090 for the flare. Should end up being pretty close.
Different tube benders with different radius will yield a different tube cut length.

Tom

[sjhurlbut]

Very humble advice Tom.

Only advice I can give you is at least consider TS Flightlines. You'll NEVER have a leak - especially brake lines. I've used TS on my last 2 RVs solely - not a hard line in the plane. AN4 lines aren't too bad and you can muscle then in place if you have to but I can assure you a pretty AN6 line that requires a couple 180 bends is varsity.

If you're set on hard lines I use a copper tube (very thin) or thick soder that I can bend anywhere. You can actually insert it into the fitting and make marks where you want the flares to end up. Then try and replicate it on the bench with a tube bender.

By the time you do all that, redo it, swear, redo it again the TS lines will be on your doorstep.

[Bcone1381]

https://bearhawkforums.com/forum/too...cation-pattern

This thread on another forum shows how to make a pattern for fuel line. People with no experience are making fuel lines with 6 bends that fit the first time without doing a trial and error mayhem.

Every bend has three dimensions. A distance, a clocking, and an angle. You must fabricate and quantify those three dimensions before doing it for real.

Brooks

[rapid_ascent]

I think you just need to jump in and start practicing flaring. Start with your roll of tubing and start learning how to do the flare. Get a magnifier that you can inspect the flare afterwards. Some say that should be 10x. I have a big magnifier lamp that I inspect mine with. Look for cracks or scoring.

I found a nice set of instructions for flaring on the General Aircraft Hardware site.
https://www.gen-aircraft-hardware.co...eel_Tubing.asp
It uses a rigid flaring tool on stainless tubing but most of the tubing prep steps are still applicable.

The bending tools are easy to use once you figure out the L and R marks on the tool. Put a little grease on area where the tube is formed around and it?s pretty simple.

I work from one end. Make the flare. If your screw it up cut it off and redo. Once you have a good flare then measure to the first bend. Mark the tubing make the bend. Check the length is correct. Measure to the next bend and work toward the other end. This is a good way to practice too. You will mess up plenting of tubing at least I did.

[gasman]

Hi Gregg,

You already have a Rolo so that means you are going to do tubing. I used a tubing bender from HF.... https://www.harborfreight.com/tubing..._q=tube+bender you will need to make some bends and waste some tubing and file and sand the rough edges till you can bend a 90 without any marks on the tubing. Applying electric tape in drag locations really helps.

As far as flairs, I found that a flair DOES NOT change the finished length by any significant amount. You can check this yourself.

An easy way to make up lines that fit is to make some parts that will help you. First, take a measured piece of tubing that will fit in your Rolo to flair. Measure it, flair it and measure it again. Do this with a 90 and 45 also. Understand where your bend starts and ends.

A few marks on these bends will tell you how much tubing you are using to make that bend. Mark a start point where it will match the mark on your bender. Make a mark every 1/8 inch the full distance of the bend area plus some so you can see what is consumed in a bend.

To help with your mock-up of a line, consider some made up bends, some flairs with known dimensions (say 1 or 2"), some 3/8 wooden dowel (for runs) and some 3/8 ID vinyl tubing cut into small 1/2" sections to connect the dowel, the flairs, and the bends to mock-up the line you want to make. Then just add up the dimensions of each piece and transfer the bend marks to your project tubing. Make up the longest line first so you can continue to cut the dowel to make the rest.

Do buff the lip of your flairs so they clear the threads of the coupling nut and fit the sleeve. Do not over flair (crush) with the Rolo, stop when you feel resistance.