I hope somebody can help me with this problem. I am at the end of a 1/4 scale sig cub build and am trying to find out what plastic or aluminum even cardboard tubing I can use, and where i can buy it, to put into the 1/2 in rib holes so I can run the servo leads through. Once the wing gets covered it would be a nightmare to try and get the leads threw if I ever needed to replace them. I know about tying a string or wire and threading it threw method but this is a long wing! This tubing should be as light as possible, obviously, and is proving very difficult to find. I have tried Home Depot, Lowes, Rona and many other places. They all have 1/2 in aluminum tubing only problem is the inside diameter is too thick and the servo leads will not pass through. I live in Erin Ont any help on this would be greatly appreciated.

I use this stuff, sometimes:

https://www.sonictronics.us/building...ies/con-do-it/

Not sure if they ship to Canada.

Per the item description: Con-Do-It is a clear plastic PVC tube that has been designed for modelers. Con-Do-It has an inside diameter of .50 inches with a thin .023 inch wall

It appears that the O.D. is 0.50 + (2 x 0.023) = 0.546, so you would have to enlarge your wing holes slightly.

Decades ago, we used to use empty giant Pixie Stix plastic straws for wire conduit, but they apparently are no longer made in a large enough diameter.

I just roll up a piece of paper.

rgburrill is absolutely correct. The tube does not carry any load and does not need to be strong. It only functions as a servo lead guide. Cut a strip of brown packing paper the length of the wing panel and about 5" wide. Roll it tightly around a 3/8"dowel to form a tube. Slide the dowel and paper tube into the wing and then let the tube "unwind" and remove the dowel. This method works even if you have already covered the wing.

All these years I've gotten by with just a thin string with a small lead fishing weight on the end. Tip the wing up vertical and let good ol gravity do the work as you feed the string in.

Rather than the string/weight method I use bead chain. Feed it into the wing root and it will find its way like magic.

Yeap,, then wick in some thin CA to stiffen it up and you have a fiber reinforced plastic tube

I just install a pull string while building.

String metode is what I use!