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Thread: Alternate Turnbuckle Safetying Techniques?

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    rwanttaja's Avatar
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    Alternate Turnbuckle Safetying Techniques?

    Let me start by saying that I *have* looked at the options in AC43-13, and I am also aware of the MS clip-type turnbuckles.

    I had an internal brace wire of my Fly Baby slack off a little bit, and needed to tighten it up. One end is right at an inspection plate, but the other end is inside the wing further. My hand barely fits in the inspection ring, and can (barely) reach the far end of the turnbuckle. When it's in there, of course, it completely blocks the view of the turnbuckle (though Dad said a good mechanic has eyes in his fingertips).

    I've tightened it to where it needs to be, and am contemplating re-safetying it. Working at that far end, though, I feel like a proctologist trying to write his girlfriend's name inside someone's colon. I am NOT looking forward to trying to wrap the safety wire around that far end. I'm not even looking forward to trying to weasel off the end of the old safety wire that's still there.

    So...I'm looking for alternative methods. The basic requirement, of course, is something that keeps the thing from rotating on its own. I'm wondering if someone has come up with a method that doesn't require so much action at the far end of the turnbuckle. Anybody have methods that seem to work?

    The current turnbuckles seem to have ~0.032" brass safety wire. I'm kind of suspecting that might be easier to work with, though that doesn't meet the acceptable size for 1/8" cable per AC43-13 Table 7-8.

    Ron Wanttaja

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    Sam Buchanan's Avatar
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    Ron, I have a similar situation, though not quite as restrictive as yours, with the turnbuckles on the flying and landing wires of my Fokker D.VII wannabe. I wasn't pleased with the way my rendition of the AC43-13 method of safe tying the turnbuckles, so I used a different method that I like much better. I'll try to get a photo if I get to the hangar tomorrow but here is a brief description:

    Cut a length of wire about three times the length of the turnbuckle. You will need to fish the wire through the buried eyelet or fork then pull it through to where you have two equal lengths. Twist the wire about 1/2 the distance between the eyelet and center of the barrel. The two ends go through the hole in the barrel in opposing directions and are twisted together again. The free ends then go through the other eye or fork in opposing directions before the remaining free ends are twisted. Trim the twisted end and bend over as needed for personal safety.

    This resulted in a very nice looking safety wire that basically has the same function as a double-wrap safety but without having to wrap the free ends around the fork. I used 0.041" wire. Don't know if this made any sense but I enjoyed typing it.....
    Sam Buchanan
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    Quote Originally Posted by rwanttaja View Post
    Let me start by saying that I *have* looked at the options in AC43-13, and I am also aware of the MS clip-type turnbuckles....
    Worth another look, I think.

    Quote Originally Posted by rwanttaja View Post
    The basic requirement, of course, is something that keeps the thing from rotating on its own.
    So AC43-13 paragraph 7.179 allows for any turnbuckle safetying that meets the requirements of TSO-C21:

    http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgTSO.nsf/0/d21f3603188332d386256da500548f88/$FILE/C21b.pdf

    You, of course, are not going to perform all the testing required (and I'm sure Sam didn't either) to prove that some random scheme you come up with meets the TSO requirements, but as with everything EAB, you don't have to. Good guidance, but NOT required, as you well know. But at least if you look at the TSO, you'll know what the FAA thinks is important from a strength and fatigue standpoint for turnbuckle safety wiring.

    All that said, and given the restrictions that you've stated with respect to access, I'd think that the "(C) Single Wrap (Spiral)" scheme shown in AC43-13 Figure 7-26 would be close to what you could use. You should (with the eyes in the fingers of the one hand that you can fit in the wing [and I agree with your dad that every good mechanic has those eyes]) be able to create the safetying shown at the left end of the figure, get the wires through the hole in the barrel and then deal with the wraps at the access panel end.

    If you can't do the wraps at the panel end, then you can just twist the ends after inserting them both through then end to capture them (basically, finishing off the way Sam said).

    Quote Originally Posted by rwanttaja View Post
    The current turnbuckles seem to have ~0.032" brass safety wire. I'm kind of suspecting that might be easier to work with, though that doesn't meet the acceptable size for 1/8" cable per AC43-13 Table 7-8.
    Well, sure - the 0.032" wire will be easier than the 0.040" SS wire, but given what table 7-8 requires and what TSO-C21 is shooting for, I'd try hard to get that to work. If you can't get the 0.040" to work, Then maybe 0.032" SS, rather than 0.032" brass.

    Obviously, however, the 0.032" brass wire has worked, since that's what the original builder installed umpteen years ago. But still...

    My $0.02.

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    rwanttaja's Avatar
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    Thanks much for the suggestions and comments. I was able to do a conventional safety-wire job today, using 0.032" stainless steel wire. It ain't too neat, but it should work.

    Ron Wanttaja

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    Sam Buchanan's Avatar
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    Ron, glad you got your turnbuckle issue remedied. Here is the photo I promised earlier, maybe other builders will find it helpful. This isn't per the illustrations in AC43-13 but is easy to make and I don't think that turnbuckle is going anywhere. The cut end of the twisted wire is folded back on itself even though it doesn't look that way in the photo.

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    Last edited by Sam Buchanan; 12-11-2017 at 05:09 PM.
    Sam Buchanan
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    rwanttaja's Avatar
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    Wow, Sam, I really like that. Will use that system if I have to safety another one in the wing.

    Here's a shot in-progress of the turnbuckle. The old safety wire has been cut and not yet removed. The parallax of the camera shot makes it look like the far end of the turnbuckle is above the inspection hole, but it sure the heck ain't. The near end of the turnbuckle is centered.



    Note how the inspection hole was been roughly cut out...it tore my hand up a bit, until I spent a few minutes with some sandpaper smoothing it down.

    BTW, this is lit by one of those teeny-tiny LED worklights, tucked inside the wing. And I did remember to take it back out when I was done....

    Ron Wanttaja

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    Sam Buchanan's Avatar
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    Yep, that is a tight spot, am familiar with the anti-drag cables from helping my hangar neighbor with his Fly Baby project. The conventional "wrap" method is probably better in that situation, it would be really tough operating safety wire pliers in that space! My blood would be flowing after snagging the end of that cotter pin that wasn't finished properly......
    Last edited by Sam Buchanan; 12-11-2017 at 05:57 PM.
    Sam Buchanan
    EAA Technical Counselor
    The RV Journal RV-6 build log
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    This is a link to a Hints For Home-builders video that demonstrates a tool used to keep the turnbuckle from turning while your securing it with safety wire. In the video he talks about using it in a tight spot, like through an inspection hole. It seems like the tool would take up a lot of space and make it more difficult to wrap the safety wire but since I've never tried it I don't really know. The good news is that all the turnbuckles on my plane are relatively easy to reach.

    http://www.eaavideo.org/detail/video...autoStart=true

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    Quote Originally Posted by Tralika View Post
    This is a link to a Hints For Home-builders video that demonstrates a tool used to keep the turnbuckle from turning while your securing it with safety wire. In the video he talks about using it in a tight spot, like through an inspection hole. It seems like the tool would take up a lot of space and make it more difficult to wrap the safety wire but since I've never tried it I don't really know. The good news is that all the turnbuckles on my plane are relatively easy to reach.

    http://www.eaavideo.org/detail/video...autoStart=true
    The turnbuckle holding tools that utilize a roller chain body can be used in very tight areas......not sure how the "C" clamp ends work (seems kinda cumbersome) but all that's needed for most turnbuckles is a straight pin on the end of the roller chain. I agree with the narrator, these things have been around a long time and they work great - at least for tightening and loosening a turnbuckle. Not sure if they are of much assistance for safetying. Never used one for that.
    Last edited by martymayes; 12-12-2017 at 09:00 AM.

  10. #10
    Sam Buchanan's Avatar
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    Quote Originally Posted by Tralika View Post
    This is a link to a Hints For Home-builders video that demonstrates a tool used to keep the turnbuckle from turning while your securing it with safety wire. In the video he talks about using it in a tight spot, like through an inspection hole. It seems like the tool would take up a lot of space and make it more difficult to wrap the safety wire but since I've never tried it I don't really know. The good news is that all the turnbuckles on my plane are relatively easy to reach.

    http://www.eaavideo.org/detail/video...autoStart=true
    The tool demonstrated in the video is designed to assist with tensioning the turnbuckle, not safety wiring. Once the turnbuckle is properly tensioned, the tool is no longer needed and the turnbuckle can be safety wired in a conventional manner.
    Sam Buchanan
    EAA Technical Counselor
    The RV Journal RV-6 build log
    Fokker D.VII semi-replica build log
    YouTube Channel

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