Control Cable Heat Shrink

[whee]

Or, find a swager for the fittings and eliminate the nicopress.

I really like rotary swagged cables and wish I'd had the rudder cables rotary swagged. We used rotary swagged cables when we restored a Luscombe and they were great. It did take some effort to get the cables sized properly even when having the old cables for reference. It's doable for sure but sizing the cables with nicopress is easy.

[Archer39J]

Careful inspection of my photos shows that....
1) The initial position of the cable end slightly extends beyond the sleeve, complying with the guidance of AC43.13.
2) The photo of tag end of the cable after final compression clearly shows that its end is splayed out, meaning to me that all three compressions fully contact the tag end of the cable.
3) The EAA's Hint for Homebuiilder taught me this method, and confirms my belief that I am in compliance with AC.43.13.
4) If the initial position of the cable extends well beyond the sleeve, and after its compressed its covered with Shrink Wrap, and moisture can get to it and corrosion is then hidden from view, how is it more in compliance with AC43.13 than what the EAA hints for Homebuilders guidance gives?[/SIZE]

Looking at the reference document I agree with this interpretation of AC43.13-1B. But I can also totally see a DAR getting wrapped around this particular axle so to avoid any potential issue I'll leave it flush or slightly protruding.

But no heat shrink for me

[Bcone1381]

This discussion is good....I will be doing the same with my future cables...a slight adjustment when I cut it off so the tag end is flush with the elongated sleeve after compression.

[BTAZ]

As I have said before, we in the experimental crowd have options not available to the certified world. With those options comes the responsibility for each of us to use them wisely fully understanding the implications for which(to paraphrase Bcone) I want supporting data beyond "Some Guy On The Internet" even if "that guy" is the EAA.

For certified aircraft, Advisory Circular 43.13(note it is "Advisory" so not truly regulatory and I also think it is a bit lacking in detail with regards to this discussion) is there to use in the absence of manufacturer's instructions or other approved engineering data/support.

The Nicopress manufacturer instructions((http://www.versales.com/ns/nicopress/instruction32.pdf) require you to "pull enough cable through the sleeve so that the end will still protrude after crimping" are a bit clearer.

So while I personally wouldn't have a problem flying with control cables crimped as described(assuming the correct amount of crimp and the structure is likely going to fail well before the cable), without clarification from the Nicopress manufacturer, I would not be comfortable with the same crimp style in airframe support cables

[Archer39J]

I also think it is a bit lacking in detail with regards to this discussion

I think it's telling they don't specifically address the final configuration or specify a protrusion length, almost seems intentional.

Anyway let's not get too in the weeds on this one. I think we can now agree best practice would be to leave it flush or slight protruding.

Without heat shrink

[Battson]

If it's of any comfort, globally the electrical industry uses (and probably invented) heat shrink specifically to keep moisture out of cable joints, and make them last for many decades. Albeit electrical cable, but the principle is exactly the same.

Heat shrink will improve a cable joint's lifespan.

[Archer39J]

Chris mentioned this in post 5, and with a sealant (maybe silicone?) inside I could see how that would work, otherwise I can't see how moisture would be prevented from wicking into and under a plastic sheath. Wrapping plastic around a steel cable doesn't sound great to me. Just blocking the view makes it not worth it in my opinion, and I thought that before I watched the EAA video.

[fairchild]

would there be a way to take a short piece of either copper tubing or brass tubing and size it so it will just barely go on the tail - then maybe crimp it into the tail to contain and
cover the errant wires. then you could whip the encapsulated end to the cable beside it. - somehow- Maybe a loop of heat shrink shorter than the metal tube. Not sure if that would work.
maybe use some Parelketone on the end before you put the metal sleeve on to displace water. Or maybe silicone grease....
T

[davzLSA]

heres my 2 cents for what its worth, I think most regs will defer to the manufactures instructions and as long as that is done you know the cables will be safe. And the picture in the instructions did show a small bit of cable above the sleeve.

[Battson]

Chris mentioned this in post 5, and with a sealant (maybe silicone?) inside I could see how that would work, otherwise I can't see how moisture would be prevented from wicking into and under a plastic sheath. Wrapping plastic around a steel cable doesn't sound great to me. Just blocking the view makes it not worth it in my opinion, and I thought that before I watched the EAA video.

Proper heat shrink has heat sensitive glue inside it to create a waterproof seal. Personally I don't see the point in the cheap stuff without any glue, it doesn't do anything at all. Any electrical store will have good quality heat shrink.

That, combined with the grease / oil inside the cable will keep out all moisture.

[Bcone1381]

I am going to fabricate new cables. Mine do not comply with the Nicopress instructions. A number of highly respected builders who have weighed in on this thread have influenced me. I appreciate the input here...keep it coming. I am building at home, alone, for the first time. Home is a good environment to get stuff done, yet kind of in a vacuum. Its not an airport with experienced mechanics, builders, careful eyes, insightful ideas and an active EAA group to bounce around ideas.

McMaster-carr has a heat shrink end cap with an adhesive lining that I may install on the tag end of the exposed cable. Or, Maybe I will just slide a 1" piece of the adhesive heat shrink tubing 3/4" up the tag end of the cable for protection. I will try that first and see how it looks/works.

It seems as though the end cap will
-look good
-protect the builder and user from puncture wounds, scratches,
-be fully complying with AC43.13, Nicopress, and
-avoid the criticism of possible corrosion underneath heat shrink that has been brought up by the EAA, and evidently others, whether its a real risk or not.

Does that all seem like a reasonable solution?

Screen Shot 2017-11-19 at 9.18.43 PM.png

[Archer39J]

Brooks: If you're making them with a short but still protruding stub like we've agreed is correct then there shouldn't be any need for heat shrink I would think. As we've discussed their only purpose is to keep the builder safe from being poked.

Well, that and to shield a flight critical component from view.

Battson: That makes a lot more sense then, thanks.

[Bcone1381]

I crimped one up with about an 1/8th" raw end sticking out and I did not like it. The end of the sleeve mushrooms up, and a finger can still easily make contact with the raw cable end. It might be ok if it was protected with a drop of shoe goo. Still keeping my mind open to ideas though.

[BTAZ]

I I think there is something to be said for one piece of heat shrink over the tag end and continuing on to and over the compressed sleeve to make the end more "snag resistant" overall and help avoid what Battson described in an earlier thread.

[Archer39J]

Came across these videos in researching control cable techniques, not sure what I think about the welding part yet...

Use Cleco pliers to help make cable ends:

https://youtu.be/-m5v9MEdBPE

Welding frayed cable ends:

https://youtu.be/U_UXSyX0oz0

[BTAZ]

43 13B(excerpt here: http://www.337skymaster.com/document...inspection.pdf) is pretty clear about the torch method Page 7-33, section 7-147 B " Cut cables to length by mechanical means. The use of a torch, in any manner, is not permitted"

So while I like the idea for what they used it for(would have been handy for the bicycles I've re-cabled over the years) I don't think it should be used for the flight control cables discussed nor for any "structural brace cables".

And I found clarification in Figure 7-12 of the same document requiring 1/8" or more of "tag end" remaining outside the compressed sleeve..

[Archer39J]

Ah thanks for that weld reference, yeah heating the cable like that didn't sit well with me.

So I see what you mean on the 1/8" tail, and just to say I agree with the practice, but take a look at the order of compression in fig 7-12 (b) vs fig 7-14. They seem to be describing different methods for the two different applications, so I don't know if we can say 1/8" is "definitive" for thimble-eye splices. It seems odd they don't specify that and I have a suspicion it was intentionally omitted.