Trouble in black conduit land

(old message removed)

conduit options

Think-Other options:

>pvc thin wall plumbing tubing
>Home Depot style blue plastic home electrical conduit
>Radio Shack electronic tubing
>partial conduit, protection on rib holes
>?

You are doing it right

I did the same thing, a real pain. I found piling from both sides of the hole to stretch it while simultaneously pulling through the hole. Keep at it you will prevail!

use something smooth

I had the same problem years ago with my qb wings. I ended up going to Lowes/Home Depot and getting some really light and smooth sprinkler system tubing. Much easier to get through the holes in the ribs plus much smoother to slide wires through. No regrets 8.5 years in.

Not sure, but ...

... I suspect 1/2" PEX would go thru those 3/4" holes nicely ....

Stretching it is the key to getting it through. Pull hard! I ran this stuff in both wings and it only took a few minutes.

Goop

I too remember mine being tough. Sounds normal.

Also, I read on VAF years ago that the conduit could creep after a while in service. I don't know if that is true but I hedged my bets and applied a little Amazing Goop everywhere the conduit went through a rib or bulkhead.

Work it from side to side

Bend the conduit tube so that a conduit 'ring' pops through on one side and then bend it the other way to pull the rest of that ring through. Pull on the tube all the while. Do 5 or six rings at a time on each wing rib in succession so that the conduit proceeds down the wing span like a caterpillar crawling along. Couldn't be done after the skins go on.

This worked for me but it is still a pain.

By the way, take a one inch piece of this stuff, light it and watch what happens. Then decide whether you want to use any of it in the cabin, especially up at the firewall.

Use a hair dryer to warm the conduit. Makes the pulling a lot easier.

Conduit install

When I did mine in our basement, my family thought I had given up and was hacking my project to little pieces. It's loud and makes you nervous. Wait til you bend the fuselage longerons with a big hammer. This may no apply to a 10.

Thin Wall Butyrate Tubing

For straight runs, i.e. wings & fuselage keel, clear thin-wall butyrate tubing is a good choice. It is semi rigid, has a very thin (1/32") wall and is clear so you can see what is "going on" inside. It comes in 6' lengths so a coupler of some sort is required - I turned some on my lathe from some PVC pipe scraps I had laying around.

The real beauty of this stuff is that with such a thin wall, a greater i.d. is realized - making a 3/4 o.d.net an 11/16 i.d. The usable interior area is 84%of the outside diameter - compare that with Van's corrugated flexible tubing and you get something like 56% (if sidewall thickness is approx. 3/32") - that is 50% more area for wire bundles!

I've used this stuff since 1985, and it has always performed flawlessly with no degradation observed over that time.

It is sold by U.S. Plastic Corp - usplastic.com as Tenite Butyrate Tubing in sizes from 1/2 o.d. to 6 o.d.

HFS

digidocs said:

First of all, thanks for all of the advice.

Update for prosperity:

I enlarged the holes that I could reach to 13/16", and commenced war. It was a major battle indeed, especially in the wing walk area where the skin was already installed and I could not enlarge the holes. The first 6-8" of conduit was destroyed in the pulling process. I cannot even imagine how you guys managed to pull this stuff through the entire wing using only 3/4" holes.

One more wing to go and then I will secure everything with 3M 5200 urethane.

Over and out,
David

Click to expand...

You did deburr the holes after you drilled the ribs, didn't you? It was a pain to pull, but I'm pleased with the results. The first photo below is the result of about 20 minutes work, worrying one corrugation at a time through the holes. THEN I discovered the pull-both-ways-and-stretch-it-out-a-little method. It probably took a couple of hours over three days or so to finish it up. My wife did ask what the #$!! was going on out in the shop.

middle of the wing

I found that starting the installation from the middle of the wing is easier. You only have half the length to wrestle in each direction.

What to use then?

Loman said:

Bend the conduit tube so that a conduit 'ring' pops through on one side and then bend it the other way to pull the rest of that ring through. Pull on the tube all the while. Do 5 or six rings at a time on each wing rib in succession so that the conduit proceeds down the wing span like a caterpillar crawling along. Couldn't be done after the skins go on.

This worked for me but it is still a pain.

By the way, take a one inch piece of this stuff, light it and watch what happens. Then decide whether you want to use any of it in the cabin, especially up at the firewall.

Click to expand...

Is there something better to use that's not flammable?

Conduit fix

Split the conduit down one side along the complete length. Then collapse the tubing slightly and pull it through the holes/grommets..This will also give you an option to have wires etc enter the conduit anywhere for stuff like pitot heat/stall warning..