Rudder Cable Interference

[Jeff Moreau]

I have the boarding step fitted and clecoed in place on my RV8-A and the left rudder cable is going to make contact with the tubular section of the step (the piece that attaches to the baggage floor rib). I know that several builders have experienced this problem. Is it necessary to put any type of material between the cable and the step tube to eliminate rubbing or is it ok for the cable to make contact with the metal tube?

[Wicked Stick]

Jeff,

I'm building an 8, so I don't have any first hand knowledge of your situation, but common sense would tell me that you don't want a control cable rubbing on anything metal that would pre-maturely cause a cable to break.

Perhaps you can slip on a piece of hose like the others that came with the cable and attach it around the area where it is rubbing against the step. That way at least the cable is rubbing on a piece you can replace the tube if it starts to wear through the plastic/nylon tube.

Call Van's or e-mail them a picture of the interference. See what they suggest.

[Jeff Moreau]

I spoke with tech support at Van's. They informed me that this is a very common problem. In fact their factory demo aircraft has a rudder cable which contacts the step support tube. They said if it really bothers me then I should wrap the tube with some type of low friction tape. Just thought that everyone would like to know.

[jim_geo]

That's why I didn't choose an 8. ....... just kidding

[Wicked Stick]

That's why I didn't choose an 8. ....... just kidding

Um, the 8 does not have this issue, just the 8A with the steps..
I got a chance to look at the drawings the other night, and I can now see why that happens on the 8A design.

If it were me, I'd use something that could always be removed and replaced to keep the cable from wearing on the step support shaft.

WS

[chaskuss]

Jeff,
I originally intended to put steps on both sides of my 8A. I went as far as making mirror image reinforcement pieces of the right side of the F-807 bulkhead and installing them. The best solution I've seen for your problem was the following.
The builder notched the horizontal part of the internal step tube directly below the rudder cable. He then cut a section of 4130 1" diameter tubing (same thickness as the step) lengthwise. This half a tube was then installed into the notch and welded in. It allowed plenty of cable clearance & retained the strength of the unit.
That said, after speaking to several 6A and 8A builders, I decided to forgo the step all together. Instead, I'll carry a lightweight, collapsable plastic step, which I can stow in the forward luggage compartment.
Since I'm 6'4" tall, I don't need the step. My folding step stool will be for the convenience of passengers.
The builders I spoke to said that it's nearly impossible to keep that step from rusting. Some tried paint, so chrome or nickel plating. Over time, none worked. I was also told that I could expect to whack my shins on that step a lot.
It's your plane, you make the call.
Charlie Kuss

[Jeff Moreau]

I appreciate your response. I wish that I had the choice of not installing the step. I am assembling a quick-build kit and it already had the step hole cut out through the side of the fuselage skin. I have the step in place and riveted. Do you know of any type of welding that would allow me to use the method that you described without damaging any of the surrounding area?

[chaskuss]

Jeff,
I doubt that any type of welding could be performed with the step installed without melting the UHMW inner retainer block. One other way to fix this "might" work. Place wet rags on the step on and near the inner UHMW retainer. Quickley heat the area where the cable rubs with an oxygen/acytalyne torch and indent the affected area with the ball end of a ball peen hammer. It wouldbe a good idea to place the wet rags near all nearby skins as well, to minimize excess heat there. This will leave you with a sand/prime/paint repair to the area where the powder coating will have burned off.
All in all, I think that any fix would best be done off the fuselage. Of course, that means drilling out the rivets.
Charlie

[Snap]

Why not make a small cradle from nylon, then make it sit on the internal step pipe. It would not have to be thick, just enough to let the cable rub on it and you could replace it quickly if you fasten it right.

What do you think?

[Jeff Moreau]

I am planning on doing exactly that. I ordered a piece of 1/16" Teflon Sheet from Aircraft Spruce and am working on a design right now.l