Defeated by ribbed conduit installation

Of all the things that would incite choice words this morning... I, for the life of me, cannot get the Van's ribbed conduit through the fuselage wiring holes (eventually the wing holes also, since they're the same size). I've read on Smitty's site about trying to squeeze the end and rocking the ribs through. But I can't even get the first ribs of conduit through.

Any other tips, maybe enlarging the hole itself? Or are there other options for a flexible wiring tube at Lowes Aviation or similar that I should just ditch Van's tubing for? Been reading in the archives, and I don't want to use rigid aluminum or plastic tubing. Complicates my designed wiring runs from the baggage area back.

Thanks!

What size conduit and hole?

Don't enlarge the holes. (Assuming you made them 3/4" to accommodate the standard Van's conduit.)

You just need to yank the conduit, pull really hard. Yes, it sounds awful when you do it but it works and doesn't hurt anything.

After it is in place, use some ProSeal at each rib to secure the conduit and keep it from being cut over time, due to vibrations.

N941WR said:

Don't enlarge the holes. (Assuming you made them 3/4" to accommodate the standard Van's conduit.)

You just need to yank the conduit, pull really hard. Yes, it sounds awful when you do it but it works and doesn't hurt anything.

After it is in place, use some ProSeal at each rib to secure the conduit and keep it from being cut over time, due to vibrations.

Click to expand...

+1 -Yep - Do a bench test, it is an unnatural sound. Acclimate yourself.

Well there's Saturday morning idiot check #1... The conduit is 5/8", but the holes are also, a consequence of the plans assuming snap bushings. Probably need to check my wing rib holes also now.

So they should be 3/4"? Is this mentioned anywhere and I just missed it?

Missed the "Van's conduit" in your post. So, yes, as the others have said, pull harder and wear earplugs

http://www.vansaircraft.com/pdf/Wing_Wiring.pdf

Doh! Forgot about that sheet. It's filed away in the back of my plans binder, where I have all of my "completed supplemental plans". Well, then my wings are most likely okay. Just need to enlarge the fuselage holes. And buy stock in earplugs. I'll let y'all know how it goes later this afternoon. Thanks!

I drilled mine a little bigger, don't remember the exact size. Still a good pull to get it through. Do a test on a bit of scrap...

Hairdryer will make the conduit a bit more flexible.

When using the unibit, it creates a beveled opening on the drilling side. I also cleaned up the hole from the other side. The resulting sharp knife edge was dulled with 400 grit paper making it smooth and round.

It seems to me that the minuscule additional material removed made it smooth sailing to get it thtough. As the other said, pull it through while stretching it.

Also start from the middle, that will minimize the travel distance.

Just pull a section through one hole then pull that amount through the next hole and work it eventually through all of the holes. Then go back to the beginning and repeat. You can't really just pull on the end you have to work it through one rib at a time. It is pretty loud but the more you pull the more it stretches the conduit so that helps. I heard this was a big problem from this site but frankly I didn't think it was such a big deal.

I used clear RTV on each rib location to hold the conduit in place and prevent vibration from the rib cutting through the conduit. With the clear you can hardly tell the RTV is there.

I gave up and split mine longways with a pair of scissors, then glued it to each rib with some RTV.

One other thing, cut a hole on the right conduit, in the aileron bellcrank bay before running any wires. This will allow you to run wires to a future roll servo.

Right there with you Bill. Doing the same at one of my two fuselage tail runs, for the pitch servo.

The noise isn't as bad I thought. In order to not try and enlarge the existing 5/8" bushing'd holes in the center spar carry through and seatback / rear spar bulkhead, all those holes remain the same. I will transition to the conduit at holes I cut in the middle of the inner baggage compartment floor rib webs. My other rationalization here is there are too many interconnects under the seats for conduit to be useful. Wire bundles entering and exiting the conduit will have the woven sleeve (whatever that stuff is really called) to protect it from the edges of the conduit.

Yep, royal pain in the a$$. I was able make it a bit easier by pinching the tubing where it went into the hole I was working it through, forming a crease that folded into the tubing. I also made a tool out of PVC piping with a longitudinal indentation formed in one side by heating. Made it slightly easier.

Running wires thru conduit

Once you get the conduit noisily thru the holes, use some light string tied around a cotton ball, insert into tube and use air hose to blow cotton ball and string thru far end.
Slick. Now you can pull wires, and an extra string for future pull, with ease.

Pat Garboden
Katy, TX
RV9A. N942PT

Yep. You can also use some extra string and tie it into a loose loop. Now you can continuously pull wires as often as you like.

Scott, maybe I'm too late commenting if you've already gone ahead. But there's an alternative point of view you may not have heard about.

Years ago, my first technical advisor told me he abandoned the idea of conduit in his wings and he went ahead without it. The drawbacks include: It's flammable, that's why commercial aircraft don't use this product. It retains any heat inside that may build up in the wires. If you have a wire or wires that exit the conduit somewhere along the way, you have to cut into it or make holes or provisions for that. I can imagine it's a hassle. And finally, the frustrating experience you've described getting it installed. There may be other reasons, these came to mind.

He just inserted snap bushings in each wing rib. The ribs and wires can all be reached from the openings in the bottom of the wing to reach in and pull the wires through the snap bushings. You could still use a pull string. Spiral wrap can be installed easily around the wire bundle between each set of ribs. Wires can easily exit the bundle anywhere along the way. Heat buildup is not a problem. If one wire needs to be pulled out or checked for maintenance, it's not a problem. Nor is it a problem to reinstall it or add another wire or two at some point.

After carefully considering everything he told me, I ended up returning the conduit that I had purchased to Vans, and I went this route for my wings. I hope it's helpful to consider!

Pat, Russ - Yup, again right there with ya on the cotton ball and string plan.

Bruce - I'm very much debating this. Haven't installed anything in the wings yet. I'm more inclined to leave the wings open with bushings than the tailcone. Just thinking in terms of anything that might have to be installed down the road.

conduit

I used water heater drain pipe found at Lowes or Home Depot. It is the same O.D. as the schedule 40 pvc but half the wall thickness. Real light. Takes two per wing. Has fittings that needs to be cutoff and I used the pvc couplers from the thicker pipe. Nice thing is they are smooth inside and a hole can be drilled in it mid wing for servo or pitot wires. Dave