Cable Cutting Through
Posted: Sun Jun 25, 2023 11:26 pm
by BRS
I’ve been watching this right rudder cable slowly cut throught the skin. I’ve not yet decided how I want to deal with this. Have others had this issue?
I’m not the builder, just the fixer. The installation looks suspect but I’ve not yet tried to find the area in the plans. Do you see any obvious departures from how it should be?
Thank You!
Re: Cable Cutting Through
Posted: Mon Jun 26, 2023 6:14 am
by sonex892.
I dont know what is causing the cable to saw away at the penetration but guess its possibly a misaligned slot or incorrect rear cable guide fairlead position.
I noticed in your photo there is some non standard stuff.
No springs at the rudder pedals. Its obviously by the way the cable is sagging allowing the cable to touch the bottom of the slot until tension is applied.
Nicopress, thimbles and straps instead of fork ends securing the cables to the rudder horn?. Maybe not an issue but not per plans.
Do you have a set of plans to refer to?
Steve
Re: Cable Cutting Through
Posted: Mon Jun 26, 2023 8:14 am
by Bryan Cotton
Yikes! I did mine to the plans. On my Waiex my cable exits were good, but I had to open up the ruddervator pushrod slots. Any contact when it comes to controls is too much. We used to do safety and clearance checks at Sikorsky during the build of an experimental aircraft and I carried that mentality over.
Re: Cable Cutting Through
Posted: Mon Jun 26, 2023 10:33 am
by BRS
Thanks Steve & Bryan for the reply.
Yes I do have a set of plans and now will dig them out. I know, should have done that first. I suspected pedal springs might be something that some folks do but really, that does not seem to be a safety of flight thing considering my feet don’t (but might one day) leave the pedals. This cable alignment though needs to be remidied. Like I said “not the builder but the fixer” and I’ve got more fix’n to do. So it seems.
I appreciate being able to bounce things like this off the forum group.
-brs
Re: Cable Cutting Through
Posted: Mon Jun 26, 2023 10:40 am
by GordonTurner
Hi Brock
As others have said, this installation is non-standard. I would encourage you to study the section of the plans, which isn’t always the easiest to understand. I would make a list of parts from the plans, and order all new components from Sonex. Flight controls really aren’t the place to screw around. That said, the home-brewed installation you have may in fact be satisfactory, but I would suggest needs a much more detailed review than we can provide on an Internet forum.
Hate to say it, but I also think a very thorough review of the rest of your flight control system would be advised, plans in hand.
Good luck, Gordon
Re: Cable Cutting Through
Posted: Mon Jun 26, 2023 11:12 am
by Area 51%
My money is on the exit slot being in the wrong location. Page F26 shows the correct locations. The aft end of the right-hand slot should only be 9in from the rear of the fuselage. The left side slot is 15in from the back.
I’m guessing the original builder assumed the sides were symmetrical.
I’ve seen more than one Sonex with a mislocated slot with a patch over it.
Re: Cable Cutting Through
Posted: Mon Jun 26, 2023 11:32 am
by Bryan Cotton
I also deleted my rudder return springs. Schweizer Aircraft also did not believe they were important.
Sounds like Randy has the cause figured out! I’d forgotten that detail.
Re: Cable Cutting Through
Posted: Mon Jun 26, 2023 4:25 pm
by BRS
Area 51% wrote:My money is on the exit slot being in the wrong location. Page F26 shows the correct locations. The aft end of the right-hand slot should only be 9in from the rear of the fuselage. The left side slot is 15in from the back.
I’m guessing the original builder assumed the sides were symmetrical…
This was my suspicion all along.
BTW - The entire control system has been carefully inspected. Not for conformity to experemental sonex plans but as a matter of good & reasonable practices. Good thing the cable is steel and the skin aluminum and not the other way around 
Re: Cable Cutting Through
Posted: Tue Jun 27, 2023 4:37 am
by Murray Parr
My Waiex B model has a similar issue, the pax side cable is so close to rubbing on the exit that I wrapped it in teflon tape and applied heat shink over that to make sure it doesn’t start wearing through. I double checked all the dimentions for the mixer controls and fairleads and all were exactly as per plans. I never saw a dimension for each exit so I will investigate that possibilty for mine. The pilot side has plenty of clearance
Re: Cable Cutting Through
Posted: Tue Jun 27, 2023 8:06 am
by Bryan Cotton
It’s a lot safer to open up the slot.
Re: Cable Cutting Through
Posted: Tue Jun 27, 2023 8:22 am
by Area 51%
Looking at the pictures, it would appear the slot on the left side is also not in it’s proper location. It’s as if the left and right panels had been swapped at birth.
Check behind the left exit fairing for fuselage damage ahead of the slot.
Re: Cable Cutting Through
Posted: Tue Jun 27, 2023 9:33 am
by BRS
Area 51% wrote:Looking at the pictures, it would appear the slot on the left side is also not in it’s proper location. It’s as if the left and right panels had been swapped at birth.
Check behind the left exit fairing for fuselage damage ahead of the slot.
Wow! Area51 I think you should change your handle to EagleEye. If you are right, that is good catch. Not that I’m going to swap the panels but I will have a good close look see. Swapped or not, there is some minor metal work in my near future.
Re: Cable Cutting Through
Posted: Tue Jun 27, 2023 11:41 am
by pappas
I would extend the slot aft to eliminate the interference with the cable using the dimensions in the plans.
Next, fab a “U” shaped aluminum doubler maybe .025 or.032 from scrap.
After that, I have always fabbed a similarly “U” shaped sacrificial “glide” (?) for lack of a better term from a 1/4 inch thick piece of plastic cutting board, or Teflon, or a similar type of material that is riveted to the fuselage and the aluminum doubler and resides between the cable and the fuselage.
The aluminum doubler and the Teflon glide can be fabbed to the same shape, match drilled, and installed at the same time with rivets of the appropriate length.
The Teflon will protect the fuselage without damaging the cable if there is any subsequent contact between the two.
Re: Cable Cutting Through
Posted: Tue Jun 27, 2023 7:25 pm
by BRS
I’m thinking like you Lou.
Except instead of aluminum I might just 3D print something.
The panels are definately swapped (pic). My neighbor suggested flipping the steering linkage and all to the other side then it would all line up like it is supposed to. Clever idea.
Re: Cable Cutting Through
Posted: Tue Jun 27, 2023 8:20 pm
by Bryan Cotton
BRS wrote:My neighbor suggested flipping the steering linkage and all to the other side then it would all line up like it is supposed to. Clever idea.
Except you would need to modify the tailwheel weldment. Which would be ok.
Re: Cable Cutting Through
Posted: Tue Jun 27, 2023 9:54 pm
by peter anson
Easiest fix is cut the new hole in the correct location and cover the old one but you need to do the left side too as the cable is obviously rubbing there as well. Who knows, you might even find it is nicer to fly without the extra drag on the cable.
Peter
Re: Cable Cutting Through
Posted: Wed Jun 28, 2023 1:57 am
by sonex892.
BRS wrote:My neighbor suggested flipping the steering linkage and all to the other side then it would all line up like it is supposed to. Clever idea.
It could be done, but would be a lot more work and new parts than it seems. None of these bits are symetrical so can’t simply be flipped. The rudder is hinged on the left, not the centerline.
Steve
Re: Cable Cutting Through
Posted: Wed Jun 28, 2023 10:00 am
by BRS
sonex892. wrote:… The rudder is hinged on the left, not the centerline.
Steve
Good point.
Re: Cable Cutting Through
Posted: Wed Jun 28, 2023 11:15 am
by Area 51%
I guess it wasn’t just the cable exits that got located on the wrong side. It certainly looks as if the two sides were exchanged for each other during assembly because the inspection covers also seem to be on the wrong side.
My question is how important are the locations of the inspection holes in the first place? I’m a Waiex builder, so I don’t know what those holes are used for. Does it not matter?
Re: Cable Cutting Through
Posted: Wed Jun 28, 2023 8:41 pm
by bcharlton
I don’t understand the extra hardware connecting the cables to the rudder horn. They should attach to the rudder horn. And…why is there
so much slack in the cables?