Control Cable Heat Shrink

[Archer39J]

I notice many builders are putting heat shrink tubing around the ends of their control and trim cables, some clear, some opaque. I'm wondering what the purpose of this is? I assume it's just to retain the cable that sticks out from the nicopress fitting, but if it's short enough is this an issue?

I ask because it A: seems unnecessary and B: could possibly serve to trap moisture against the cable if it were to enter the open ends. I'm thinking about how the vinyl covering that comes on AL sheet sometimes promotes corrosion.

[whee]

I did it to keep the end of the cables from poking me. The tube came off one of my cables and I've already poked myself on it several times.

It is possible to that moisture will get in there. If that concerns you then I wouldn't do it.

[Flygirl1]

Every single one of mine is heat shrunk for the same reason, to not get poked. A few have come off, but most have stayed put. I shrunk them all the way up onto the nicopress piece. I do not intend on any of those areas getting moisture, but if they do both ends are open so what goes in might come out?

[Archer39J]

Hmm and I suppose no more so than the nicopress fitting itself now that I think about it, I was just musing about the plastic/steel interface there.

I saw some photos having used black shrink, I would at least want to use clear so as to be able to inspect the cable fully.

[Chris In Milwaukee]

Oh yeah, those pokies hurt! And they get you when you least expect it.

There is an inner-wall melt version of many types of heat shrink that have an adhesive in there for weatherproofing connections (electrical, mainly). If you had to cut those off of a nicopressed fitting to inspect them, it would be super PITA, though.

[Battson]

I couldn't trim it close enough to leave no tail, and the tails can catch on things. Based on my experience, I think it's a safety consideration.

I had one situation when I dumped the flaps and the cable went a tiny bit slack for an instant, as the springs moved faster than the cable. The flap cable eye caught on the steel, and the whole system had jammed up when the cable tension had returned in the same instant. Easier to demonstrate than explain... I had to jiggle it free once we stopped and parked up. Once I got in there I saw that the heat shrink had come off, the loose cable end was frayed and hooking on things.

If you trim it too close, then you risk cutting into the load bearing cable. I put a steel plate in between the two pieces of the cable, to avoid accidentally cutting it. I still got some short tails.

And yes, the cut end of the cable is needle sharp and covered in grease, which presents a safety hazard on it's own.

[Bcone1381]

I did not use heat shrink on my cables. EAA Tips for Homebuilders says this is how they do it in OSH at the Weeks Hanger on the warbirds.... http://www.eaavideo.org/detail/video...ss-sleeve-tips

Compress the middle of the Nicopress sleeve first, followed by the end at the eye. Then stick a thin piece of steel between the two cables, and slide up to the sleeve.

Use your hand dandy Dremel Tool Cut-Off Wheel to cut off the tag end of the cable. Leave as little cable sticking out as possible, using the steel as your back stop.

When the sleeve gets it last compression, it naturally elongates measurable, enough to make that tag end hind inside a little cave with no pesky wires exposed to poke even a curious three year old.


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[Archer39J]

Oh nice, Brooks for the win. I'm liking that method, nothing to fall off, no pigtails to get caught or skewer a builder. Saving this in my 'build techniques' folder, thanks!

[BTAZ]

Note that method is likely OK but does not appear to comply to AC43.13-1B and, depending on who does the inspection, might be a headache.

There is a statement "If the cable end is inside the sleeve, the splice may not hold the full strength of the cable" on page 7-148 where they discuss Nicopress sleeves

So while I think it would be fine, it wouldn't surprise me if some DAR's or equivalent might not think the same..

[Archer39J]

Good catch, so just leave it sticking out a little.

ETA: Just watched the video and he mentions my same concern about moistue and inspection. Is the EAA advocating an incorrect method?

[Battson]

Note that method is likely OK but does not appear to comply to AC43.13-1B and, depending on who does the inspection, might be a headache.

There is a statement "If the cable end is inside the sleeve, the splice may not hold the full strength of the cable" on page 7-148 where they discuss Nicopress sleeves

So while I think it would be fine, it wouldn't surprise me if some DAR's or equivalent might not think the same..

That was my first thought too. Some inspectors will fail you on this stuff. I also like to think my cables are as strong as possible, given my life depends on it.

[Chris In Milwaukee]

There’s even a service bulletin for my Maule to that effect. There was an out-of-spec nicopress crimper at the factory, and a requirement to inspect all fittings for slippage. Best way to do that was to see if the “tail” had slid under the sleeve.

[BTAZ]

FYI, the Nicopress instructions(http://www.versales.com/ns/nicopress/instruction32.pdf) also require you to "pull enough cable through the sleeve so that the end will still protrude after crimping"

[alaskabearhawk]

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

[Bcone1381]

I stand by my work as being done in accordance with AC43.13-1b. This is kind of a long response, so if you want to get thru it quickly, skip the small print.

BTAZ, Thanks so much for inspecting my work and giving inputted being so respectful and civil. This is helpful. I say that because so often in our society outrage results from debate where non is needed or helpful. No outrage is felt by me, or desired from me in this response.

The Lord knows I need mentoring as I build., and I would love to make my cable over again if they do not meet AC43.13. My default and desire for debate is to use an authoritative document rather than a persons opinion, Groups opinion, or crown mentality. So, in my argument I quote an original document, interpret that document, and then choose what I think best practices that I can to fully comply with it. I don't have a problem with the Majority of the Groups method, but I think mine is better.

My source for arguing my viewpoint is AC43.13-1b, p.7-326. BTAZ, I did not find a page that was numbered 7-148 in AC43.13-1b. My source is dated Sept 8, 1998, is a PDF, that I downloaded I think from the FAA, but I could be wrong, and it may be old. So, I hope we are sourcing the same text. If not, please provide the text for inspection. Below is a direct quote from my source. BTW, My advice is NOT to take my advice, but rather go to the original document and decide for yourself. Next is two sentences I am using to argue my point. I included the entire section of eye splices at the end of this post.

Thimble Eye Splice.
Before undertaking a thimble eye splice, initially position the cable so the end will extend slightly beyond the sleeve, as the sleeve will elongate somewhat when it is compressed. If the cable end is inside the sleeve, the splice may not hold the full strength of the cable.

I believe the context of AC43.13 is:
1) Not that the cable has to extend WELL outside the sleeve after the compressions are completed.
2) Rather, the Initial position of the cable has to extend slightly beyond the sleeve before sleeve compression, and
3) If the cable end does not extend beyond the sleeve before compression and is thus inside the sleeve before compression then the slice may not hold the full strength of the cable.
4) Common sense tells me that if all three compressions fully contact the cable, then full strength is achieved no matter how much extends outside the sleeve.

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?
_________________________________________
ThimbleÂEye Splice.
Before undertaking a thimbleÂeye splice, initially position the cable so the end will extend slightly beyond the sleeve, as the sleeve will elongate somewhat when it is compressed. If the cable end is inside the sleeve, the splice may not hold the full strength of the cable. It is desirable that the oval sleeve be placed in close proximity to the thimble points, so that when compressed, the sleeve will contact the thimble as shown in figure 7Â14. The sharp ends of the thimble may be cut off before being used; however, make certain the thimble is firmly secured in the cable loop after the splice has been completed. When using a sleeve requiring three compressions, make the center compression first, the compression next to the thimble second, and the one farthest from the thimble last.

[BTAZ]

I don't think the concern is whether one is as strong as the other(I think it would be fine as logically cable extending beyond the final crimp isn't doing anything).

I do think there are DARs (and A&P/IAs that get involved in subsequent inspections during the life of the plane) out there that won't like it and will argue that their interpretation of 43.13(as well as the Nicopress instructions) will trump EAA Hints for Homebuilders