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Permalink Reply by Jim and Amelia Isaacs on December 12, 2019 at 4:29am

Carl,

However you decide to route everything make sure you physically isolate the electrical from the fuel. Here’s what AC 43.13 .1b says:

11-126. FLAMMABLE FLUIDS AND GASES. An arcing fault between an electrical wire and a metallic flammable fluid line may puncture the line and result in a fire. Every effort must be made to avoid this hazard by physical separation of the wire from lines and equipment containing oxygen, oil, fuel, hydraulic fluid, or alcohol. Wiring must be routed above these lines and equipment with a minimum separation of 6 inches or more whenever possible. When such an arrangement is not practicable, wiring must be routed so that it does not run parallel to the fluid lines. A minimum of 2 inches must be maintained between wiring and such lines and equipment, except when the wiring is positively clamped to maintain at least 1/2-inch separation, or when it must be connected directly to the fluid-carrying equipment. Install clamps as shown in figure 11-10. These clamps should not be used as a means of supporting the wire bundle. Additional clamps should be installed to support the wire bundle and the clamps fastened to the same structure used to support the fluid line(s) to prevent relative motion.

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Permalink Reply by Carl Orton on December 12, 2019 at 10:44am

Understand. So how did YOU install? I said strobes, but these are the zenith aeroleds that are, well, LEDs. Also, and I’m not trying to justify, these are not solid fuel lines but steel braid over carbon impregnated Teflon hose. And, only tefzel, shielded wire. 

would like to know your implementation.  Thanks for the reply. 

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Permalink Reply by John Austin on December 12, 2019 at 7:38am

Carl,

I did utilize the vertical supports to run my fuel lines, pitot/static lines, and nav/strobe wiring, but I did not try to bundle it all through the oblong hole.  I ran one stainless steel braided line from each fuel tank through the support's oblong hole on each side of the fuselage.  I waited until after the support was riveted as I did not want to risk having to drill out a rivet, etc., and risk puncturing the fuel line with a drill!  Also, after I ran the fuel line, I slipped a corrugated plastic loom sleeve over the line and ran it down the support.  I did this to physically isolate the braid from the aluminum channel so there would be no possibility of fretting and possibly also reduce potential for vibration by "filling up" the support's channel a bit more.  I also ran the pitot/static lines on the left side through the support via separate, grommeted holes rather than try to cram them in with the fuel line and/or have to enlarge the oblong hole:

On the right, I ran the right tank fuel line through that support's oblong hole, again sleeving it with corrugated loom. I ran my nav/strobe wiring and fuel sender wiring from the left side to the right through the transverse support channel in a corrugated plastic loom.  Then, I ran the wiring from both wings down the right vertical channel - again, through separate, grommeted holes.  I used aviation-grade, Tefzel coated/insulated shielded wiring.  My nav/strobe's are LED, so no high-voltage currents are involved - I think the possibility of arcing-through to the fuel line by traversing the braided wire shield, the Tefzel, and the fuel line's corrugated loom is about zero.  One good thing about quality stainless braided fuel lines with Teflon lining and AN fittings - they seal well ... in all these years and hundreds of hours, I've never detected the faintest whiff of gas fumes in the cockpit.

John

N750A

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Permalink Reply by Carl Orton on December 12, 2019 at 10:53am

Thanks for the details, John. So, just to confirm:

1. No loom around the pitot static lines in the channel? Any concerns with chafing against rivets or that extruded L angle in the channel?

2. You mentioned loom around your wires thru the transverse channel, but did you run loom around the wires in the right vertical channel?

Thanks; always enjoy your tip posts!

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Permalink Reply by John Austin on December 12, 2019 at 11:42am

At first, I "thought" I remembered I didn't put the pitot/static lines or wiring in their own looms, but, after reviewing my build pictures (that was 8+ years ago!), apparently I did put both the pitot/static lines in the left vertical support and the wiring in the right vertical support in separate looms.

I "think" what I did was run the pitot/static lines down on the left and the wiring on the right, then from below where they exit the support, I slipped slit plastic corrugated loom over them and pushed it up from below.  Then, I secured the tops of the looms with zip ties through the oblong holes, and then fed the fuel line down from above and slipped loom over it and fed that down from above, too.  The fuel line loom is exposed at the top so I could easily secure it there with a zip tie and of course down at the bottom where it exits the support.

Once you get everything in place, the natural stiffness of the fuel line, the pitot/static lines, and the wiring with their associated looms tends to "wedge" their gentle curves in the support channel and nothing seems to be rattling around loose to invite chafing or fretting.

John

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Permalink Reply by Carl Orton on December 12, 2019 at 4:43pm

Thanks, John! Helps more than you know....

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