N

N161WM

I'm New Here
I have been following several threads on creating flared fittings for my fuel system. Before I get started I figured I'd post to my fellow builders for their advice and wisdom, to double-check my approach, and help counteract the Dunning-Krueger Affect:

  • 5250-O - based on several posts in this very forum on failed fuel lines (e.g. like this one), it seems that upgrading to 5250 from 3030 is a good investment. Opinions?
  • Double Flare - FAA 8083-30 says to double-flare aluminum tubing 3/8" and under. Some of the A&Ps I know say that this is standard for them for stronger and better-fitting ends. More opinions?
  • Double Flare Tool - Several folks in various locations recommended the Mastercool (71480) Black 37 Degree Hydraulic Flaring Tool ($278 at Amazon), vs. pro-grade maint-shop tools which cost a fortune. I got one. (vid) Any experiences or words of wisdom with the Mastercool?
  • Annealing - Big questions on this, FAA 8083-30 states: "Anneal brass, copper, and aluminum by heating to a dull red and cool rapidly in cold water." But I haven't seen anywhere in builder logs or the EAA how-to videos (like this) where anyone does this. I have a brazier that should get aluminum glowing at the end. Anyone have experience or advice?
  • Flare Size - I found this post regarding inspection of flare size to ensure it is the right size. Thanks!
  • Thread Seal - Based on this post I have purchased some Permatex Thread Seal for the non-flared portion of fittings. I also have some EZ-Turn Fuel Lube. I was going to use the Permatex on the NPT threads, and the Fuel Lube on the flared threads (not the flare). This sound right?
  • Torque - Picked up some crow-foot wrench fittings for my torque wrench to use for torque rather then counting blade-turns. Any opinions or advice with this method?
  • Cutting/Bending/Deburring - Got some basic Rigid-brand hw-store tools. These typically work ok? Any tips or guidance for planning bends for routing through the cabin?

Anything I am missing, or I should consider?

Thank you all for your collective wisdom, which has helped me immensely through my RV7a project to-date.
 
Along with teh Dunning-Krueger effect, you shoudl alwso recognize a fiew things about internet forums. Folks rarely post about what is normal - so you get ore posts out at the far edges of the bell shaped cure. For instance, I know a goodly number of folks use 5052 insted of the soft tubing that Van's supplies. But I would guess that of the almost 10,000 RV's flying, maybe 8,000 of those used the Van's supplied tubing, and they are doign just fine. And it sure is easier to shape! Of course, you don't get the bragging rights that come with using the more expensive stuff that way.... ;)

Annealing? Never heard of anyone doing it to their fuel lines. Cut them, dress the ends, flare them to spec, and install.

Van's "Section 5" works pretty well if you want to get the airplane finished and flying safely.
 
... my immediate reaction to your list ...

- alternate fuel nine metal/material?
You can if you want but it's not necessary
- Double flaring?
Same as above ... Simply not necessary
- annealing?
Unnecessary. Waaaaay too much trouble for simple fuel lines.
- sealant?
The a Permatex is fine for NPT threads; I would use no lubricant on the flare fitting threads
- Crow's foot for torque wrench ?
Sure. No problem.

I fab' my fuel lines very early in the build and kept them absolutely basic. I have never had any of those "neophyte" flare joint leak .... Not once.
 
Fully agree with Paul.

Before applying solutions, make sure you have a problem. I have 15 airplane years using the tubing provided by Van's. The only flared fitting leak was one of my first ones where I overly tightened the flaring tool. Once I figured this out I never had another leaker.

I recommend the standard aircraft flaring tool for all applications: Roto-Flair 37 degree, ACS part number 212FB.

I never use anything on flare fittings or nut threads. I use Permatex 59239 Teflon thread sealant for all pipe fittings.

Carl
 
Echo all the above, and

use the nominal torque recommended. I did lots of testing (confusion induced) and standard torque was confirmed.

Do add a drop of Boelube to the flaring tip during flaring. The RoloFlare (and others) is really easy to over torque when making flares, so be gentle and practice.
 
I too used the tool Rick links above. Being a tubing rookie, I knew I needed all the help I could get. That means aquiring great tools and taking the time to practice with them. The above tool also allows work in tighter spaces which is sometimes useful. No leaks so far.

Bevan
 
Thanks

Thanks to everyone who took the time to comment. I picked up an extra roll of the tubing vans provides and going to do a bunch of practice 6" flares. I appreciate the collective wisdom.
 
flares are very easy. Don't get the expensive flaring tool that takes a wrench and can put a flare in stainless; you'll DESTROY an aluminum thread with it if you don't have experience with them.

The simple cheap flaring tools that spruce sells are just fine, use light fingertip pressure to flare it, and stop when it starts to get just a wee bit stiff. You want to form the flare, not smash it into submission. 3003 tubing is very soft and flares with very little pressure.

Also, don't jump on the armchair-engineering bandwagon and start changing out tubing for more expensive, less ductile tubing. It'll be harder to bend, harder to flare, and easier to CRACK. There are places on the airplane where the flexible tubing is designed to give a little bit, like the way that the plans have you use a loop of tubing at the wheel rather than a flex line. If you use stiffer tubing than per plan, I'd anticipate a higher failure rate than the soft tubing due to vibration cracking. Van's design is well thought out and well field-proven.

Use a paste thread sealant on pipe threads (personally I use loctite 567 teflon paste). Don't use tape (which you seem to already know). DON'T use sealant or lubricant on the threads or the taper of a flared fitting. Torque isn't rocket science either; vans recommends hand tight plus a quarter turn, and that's perfectly adequate. The point is that it's a SMALL amount of torque. It's enough to keep the B-nut from backing off, but not enough to deform the flare.
 
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