Are people using the rubber gas lines firnished in the kits or using braided stainless? I know we are building experimental, but using the rubber lines seem risky when dealing with a potential (or eventual) gas leak.

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Zentith maintains that the flexy rubber lines are ok and have not been a problem. However, they make me nervous, just like you, Blaine. I am concerned for future brittleness/hardening and just because it does not seem "worthy" of being in an airplane. Also, I worry about the joint where the hose goes over the barb fitting and gets clamped. I have had many a fuel or coolant seep in mowers, automobiles, snowblowers, etc over the years at joints like that.

Another worry, to me, is that much of the fuel lines are out of sight inside structure and cannot be monitored. In addition, certified aircraft flex hoses (unless they are the "lifetime" Teflon in Stainless braid hoses) are recommended to be replaced every decade or so due to age deterioration so it would be logical to do the same with the flex hoses supplied by Zenith. If you plumb the entire fuel system with the kit's rubber hose, that means dismantling and replacing your whole fuel system on a periodic basis.

Therefore, I plan on doing my fuel system in a combination of aluminum tube and flex lines. The flex lines will most likely be from automotive racing supply places, but it will be AN hardware, as will the fittings on the solid tube portions of the fuel system.

I intend to plumb my brakes with similar material instead of the poly tubeing that comes with the kits, as well.

There are braided stainless flex lines (and fittings for solid tube lines) of AN quality available from many automotive racing supply places. The one I mostly use is Summit Racing, but there are many more. There are also firms that specialize in making up brake flex lines for that same market, and their products will work great in our birds.

If the stainless braided line you use has a rubber hose inside the braid, you still need to replace the hose every decade or so to guard against ageing and embrittlement. I plan on using the more expensive stainless braided hose that has a Teflon hose inside it. The Teflon, literally, lasts forever without needing replacement for age.
I'm using aluminum with AN fittings in the wings and fuselage and through the firewall, using a bulkhead fitting, to the fuel pumps. Short length of SS braided hose to the engine. All for the same reasons you state. Some holes through the wing ribs may have to be differently aligned to accommodate the non-flex aluminum line. Be sure the Teflon lined hose will stay in the fitting under pressure.
I used injection hose, spendy, however very strong, overkill, maybe, but -------works for me
FYI the recommended replacement period for rubber parts is 5 years in service (see the Rotax manual). Rubber hoses of good quality work very well. We use fire sleeve over them in the engine compartment.

More interesting would be whether people use the 1/4" for the delivery to the Rotax - all lines can be 1/4" (6mm ID) but the installation manual calls for 8mm ID to the pump from (in effect) the gascolator. It works with the 6mm ID... What do people have?

You have raised some interesting arguments about fuel line types and I am adding dimensions and whether people are using fire-sleeve in their engine compartment - then we can add are people using proper firewall glands for their fuel lines - or just grommets?

Well done for opening a can of worms!!!
In Canada you must use 3/8" (larger than a possible ice crystal?) lines to the gascolator (another Canadian "must have"). Inlet of the Rotax 912 series engine fuel pump is 5/16" and outlet to the carbs is 1/4". I used quality automotive rubber lines, everything firewall forward is covered with firesleeve. Replace fuel lines every 5 years or on condition of inspection.

Hi Jonathan,

I know this post is very old now, but did you ever get an answer on the fuel hose being 6mm id from the gascolator to the mechanical pump? 

I have 6mm id from the gascolator to the mechanical pump and it works fine also. The hose is a bit hard to push over the mechanical pump barb, but it does go on and engine works fine.

What size do you have from the gascolator to the mechanical pump?

With the ever changing fuel availability problems we seem to be facing and the compatibility with different hose materials and service life limits I decided to go with 3/8 aluminum tubing for my fuel lines. I plan on adding inspection plates at the tubing fittings for periodic condition inspections. Once I close up the wings I don't intend to reopen them every 5 years to replace the hoses. By using some creative bends and joggles one can keep the number of fittings to a minimum. The plane will be doing duty in the medical missions field in India so the more trouble free the better. I like the idea of the stainless braided teflon hose forward of the firewall.
Thanks for the insight. I am thinking you are right; I do not want to open up a wing either. Where are you getting the tubing and fitting from?
Had Zenith rubber fuel lines on mine for 400 hours in two years. Changed them during upgrade. Nothing wrong with them at all.

Brake lines good, too. Changed during upgrade, too. Good as new. Rerouted them....
Just curious, do the solid lines work well with vibration, expansion, contraction, & rubbing on other parts & such? May not be an issue at all, just wondering.
Solid lines have worked great in certified and experimental planes for many, many decades now. You do need to guard against chafing and vibrating. The lines need to be clamped or secured in some manner along their entire length, ofton enough to keep the line stable and firm. When you go through a sheet of metal, you either need protective grommets or a bulkhead fitting, or the hole in the sheet needs to be big enough to allow lots of space around the solid line so that there can be no rubbing.
A pilot of an RV 10 made an emegency engine out landing at our grass strip in Angelton TX just last Thursday. He was at 7000 ft. AGL when he lost the engine so he had plenty of time to locate a field with the help of ATC. He found the aluminum fuel line had cracked in the engine compartment close to the carb. A very experienced local flyer/builder noted the line did not have a spiral-helical type bend at the point of failure that would allow for flexing of the line from vibration. He had some buddies drive over, they fixed it, and off he went.
Each type of hose has it's merits, but they both require proper installation techniques.


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