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Thread: Metal fuel lines

  1. #11
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    Default Re: Metal fuel lines

    Quote Originally Posted by Dan L View Post
    I built my EX in 2010 and have not had any problems with the plastic lines. But I have had a few leaks at the fittings. I would not recommend using the superglue suggestion in the manual on the fitting threads. The fitting will explode if you try to loosen or tighten it later if glued like this.

    I should add that I have used a couple hundred gallons of 91 car gas in mine too diluted with 100 LL.
    I have heard the later airplanes use only a drop or two of super glue. On the early ones they used a lot. Exploded fittings are no fun. Did the fuel drain retrofit and had to change a bunch of fittings.


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  2. #12
    Senior Member Dan L's Avatar
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    Default Re: Metal fuel lines

    Quote Originally Posted by raisedbywolves View Post
    I have heard the later airplanes use only a drop or two of super glue. On the early ones they used a lot. Exploded fittings are no fun. Did the fuel drain retrofit and had to change a bunch of fittings.


    Sent from my iPhone using Tapatalk
    I just put one drop on my fittings.

    When end I did the extra fuel drain SB is when I noticed the leaky fittings too. The plastic fuel lines are holding up fine though.
    Flying Carbon Cub EX #11 since 2011

  3. #13
    Senior Member 40m's Avatar
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    Default Re: Metal fuel lines

    My curiosity of other cold climate builders stems from my experience with problems of seepage at the fuel valve. I believe dissimilar materials expanding and contracting at different rates is the culprit. Hence the questions of others and my decision to use metal.

  4. #14
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    Default Re: Metal fuel lines

    Quote Originally Posted by 40m View Post
    My curiosity of other cold climate builders stems from my experience with problems of seepage at the fuel valve. I believe dissimilar materials expanding and contracting at different rates is the culprit. Hence the questions of others and my decision to use metal.

    I had had an eye opener today. When I got back from flying this am, I could smell gasoline. Got out of the plane and avgas running out the belly and down the tail wheel. Shutting fuel selector off made no difference. So we drained the fuel and started looking. Took awhile to narrow it down to rear fuel plastic fittings when the line leaves the Tee at the sump its routed to the corner of the extend baggage thru a 90 elbow. I put my hand into the area thru a bottom insp cover. Just barely put my fingers on the elbow and the line pulled out of the nylon comp elbow. It was connected enough to move fuel and leak at the same time. I think is was ready to separate any second and dump the fuel. With an impressive use of profanities I managed to take the line out. The nut seemed to be tight on the elbow
    but not compressing the hose enough. I disassembled the whole thing, retightened and installed.
    Not a big fan of plastic on gasoline line fittings

    stick your hand up there and check tightness of fittings


    image.png

    jim

  5. #15
    Senior Member Dan L's Avatar
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    Default Re: Metal fuel lines

    As I mentioned in another thread I had a few weeps in my fittings. The newer replacement fittings I got from CC seem to be better quality. Early on I had a leak where the quick drain exits behind the extended baggage. This was an aluminum fitting and the nut had bottomed out before it tightened up enough around the fuel line. A good idea to pressure check these on an EX before covering. I didn’t. I assume the factory does on their completed planes.

    Good you didnt have a real disaster.
    Flying Carbon Cub EX #11 since 2011

  6. #16
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    Default Re: Metal fuel lines

    Jim,

    Do you have an EX, FX, CC?? Just wondering who might have not tightened that fitting.

    The plastic fuel lines should have an insert (HDW-261-765) into the ends where they connect. Did you notice if that piece was in the end of the fuel line? That's what seals the lines in the fittings.


    P1060618.jpg


    P1060619.jpg

    The plastic nut should be hand snugged up and then turned another 1-1/2 to 2 turns with no thread sealer of any kind used. Then super glue is used at a couple of place (like at 9 and 3 oclock) right where the nut and threads meet after tightening. This melts the plastic to each other and prevents it from coming loose and torque seal should have been used to mark it as well.

    I always use balloons at 1 open end when done installing all the lines to check for a leak. A couple of days with the "control" balloon and the one attached to the end of the hose should tell you if you have even the smallest leak.

    Here is a forum post from one of "CHUCK & RYANS" building tips:

    We checked for leaks per the updated on line manual: using a bit of compressed air and soapy leak tester. BORING. Did not find any evidence of leaks and had a soapy mess on all the joints. I much prefer the balloon technique, which I have now refined to a fine art since an earlier post.

    First, the fuel tank lines on the left side were connected with a section of 3/8” hose. The clamps have to be really tightened down to prevent any slow leaks.

    Second, a balloon is placed on the right side, aft tank line. This is the most distant point from the gascolator. I placed a short section of 3/8 hose and put the balloon opening over that hose to assure a tighter fit. Electrical tape made a good seal around the balloon.

    Third, the aft drain was sealed with a threaded plug. The forward drain and the right forward fuel tank lines were sealed with a bolt, section of hose, and hose clamps. This left only the gasolator line open.



    Fourth, a balloon was inflated and taped on the fuselage as a ‘control’. Finally, the balloon on the aft right fuel tank line was inflated by blowing through the only open line to the gascolator (No compressor necessary!) After the balloon was inflated it was sealed with a section of hose, bolt, and clamps.



    Now the hard part. Waiting. I set this up a several days ago and both the control and test balloon are still inflated. I am much more confident that the system is leak free with these balloons than with the silly soapy mess.

    And this was a photo and post I used from my last couple of builds:

    Well, after 2 full days my balloon is still full of air in the fuel system test so I'm removing the balloons, etc. and be sure I have all the tie wraps installed over the lines, etc around the extended baggage/floor pieces.



    I will also go ahead now and apply the Super Glue (Loctite 401; RM0568-010) to all the threads of the plastic fittings AND I will put some weigh into the bottom of the baggage floor and now take my meth and go around and apply it to all the sides, back and bottom of all the aluminum pieces.

    Quote Originally Posted by Scouter View Post
    I had had an eye opener today. When I got back from flying this am, I could smell gasoline. Got out of the plane and avgas running out the belly and down the tail wheel. Shutting fuel selector off made no difference. So we drained the fuel and started looking. Took awhile to narrow it down to rear fuel plastic fittings when the line leaves the Tee at the sump its routed to the corner of the extend baggage thru a 90 elbow. I put my hand into the area thru a bottom insp cover. Just barely put my fingers on the elbow and the line pulled out of the nylon comp elbow. It was connected enough to move fuel and leak at the same time. I think is was ready to separate any second and dump the fuel. With an impressive use of profanities I managed to take the line out. The nut seemed to be tight on the elbow
    but not compressing the hose enough. I disassembled the whole thing, retightened and installed.
    Not a big fan of plastic on gasoline line fittings

    stick your hand up there and check tightness of fittings


    image.png

    jim
    Dave Embry
    "You only live once.....
    ..but if you do it right.....
    ....once is enough."..

  7. #17
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    Default Metal fuel lines

    The early factory airplanes used a lot of glue on the fittings, later used a couple drops, and you could tighten the lines without the fitting breaking
    Last edited by raisedbywolves; 01-20-2019 at 12:50 PM.

  8. #18
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    Default Re: Metal fuel lines

    Thanks Dave, that is a big help, very good info. 2013 SS

    the insert fell out of the end of the hose into the belly.. Retrieved it and reinstalled. I don't think it was tightened properly at assembly. I am very familiar with this style of compression fitting, we have
    55 or so trucks in our fleet with airbrakes that use nylon line, but brass fittings and inserts. The nut must be tightened enough to compress the ferrule against the hose

    i watch plastic items here in Maine contract and expand a lot. We use a lot of UHMW plastic. And most of our homes are covered in vinyl siding. The stuff moves a lot.

    The elbow in the plane is held captive by a zip tie, as well as the hose and i think that prevented the two from separating. Interesting to note the temp here in FL that morning was 42

    i guess it works ok, we would have heard if someone drained all fuel in flight

    Tom is it possible to change lines in a covered plane to something different?

    thx


    jim
    Last edited by Scouter; 01-21-2019 at 12:50 AM.

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