Quantcast

How much to flare fuel lines / brake lines

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

Battson

Well-Known Member
Joined
Jan 30, 2012
Messages
610
Location
New Zealand
Hey all,

I happen to be following Taiser's CH750 build thread, which is brilliant, and noticed some pretty large flares on his pitot tube lines. Obviously this isn't a pressure application so it'll be sweet as, but it got me thinking.

How much is the ideal amount to flare a tube end to get the best sealing and joint durability / life? My flaring tool was very inspecific in it's instructions, and I have seen a range of different practices. Is there a best practice?

Cheers
 

Dan Thomas

Well-Known Member
Joined
Sep 17, 2008
Messages
5,606
Hey all,

I happen to be following Taiser's CH750 build thread, which is brilliant, and noticed some pretty large flares on his pitot tube lines. Obviously this isn't a pressure application so it'll be sweet as, but it got me thinking.

How much is the ideal amount to flare a tube end to get the best sealing and joint durability / life? My flaring tool was very inspecific in it's instructions, and I have seen a range of different practices. Is there a best practice?

Cheers
See Tube Flaring Dimensions

Some specifications there.

If you buy this tool, you will get it right. It has a stop for the proper length of tubing to extend past the clamp so that the flare dimensions come out right.
 

Attachments

Battson

Well-Known Member
Joined
Jan 30, 2012
Messages
610
Location
New Zealand
That is the very tool I have! But the instruction didn't say to go until "the stop", you put the tube to the stop, then they said to flare "until light pressure is felt".
You basically feel "light pressure" from the time it makes any meaningful deformation to the tube...
So I was just going until it looked the same as what I am used to seeing.

I'd better go and re-check them all.
 

Joe Fisher

Well-Known Member
Joined
Feb 10, 2007
Messages
1,379
Location
Galesburg, KS South east Kansas
With that tool I can feel when both the inside and out side of the tube make contact in the flair. There is a very pronounced change in the effort required to turn the handle.
 

Richard6

Well-Known Member
Joined
Aug 14, 2010
Messages
705
Location
Plymouth, MN USA
OK, so maybe I don't know a flare from a dive, but it is my understanding that because of the pressures involved with brakes, that the flare fitting for brake lines should have a double flare. Maybe you are doing that but just not talking about it ?

Richard
 

Dan Thomas

Well-Known Member
Joined
Sep 17, 2008
Messages
5,606
OK, so maybe I don't know a flare from a dive, but it is my understanding that because of the pressures involved with brakes, that the flare fitting for brake lines should have a double flare. Maybe you are doing that but just not talking about it ?

Richard
Double flaring is commonly used on steel brake lines in automobiles. Sometimes I'll see it on aluminum aircraft hydraulic lines, but those systems handle 3000 PSI. A light airplane's brakes will seldom see 1000 PSI and a single flare should be fine.

Double flaring adds crack resistance and helps with sealing.

37° double flaring tools are pretty expensive.

Dan
 

Battson

Well-Known Member
Joined
Jan 30, 2012
Messages
610
Location
New Zealand
With that tool I can feel when both the inside and out side of the tube make contact in the flair. There is a very pronounced change in the effort required to turn the handle.
Yep I think I found it.
I haven't been going far enough, so I've deepened all the flairs to the correct measurements. I find the tool often comes up fractionally short of the diagram Dan posted. I had to do a few twice to get them a little deeper.

Thanks again for all the feedback. Saved me a lot of hassle here.
 
Top