What causes control lines to curl up?!

[David Ebers]

I am having a problem with my control lines curling up after 30 to 40 flights. By curling I mean like a cork screw or if you take a spring and stretch it out. The curling starts about 5 feet from the lead outs and are 5-10 feet long. Both lines are doing this and the set becomes useless.

After the third set of lines curled (slow learner) I treated the next set of lines better. I've always untwisted after every flight. I no longer dragged the handle while rolling the lines up. I cleaned them before I rolled them up after the last flight of the day. I also swapped ends, handle to lead outs, every other flying session. I thought this had cured the problem until yesterday morning. When I went to untwist the lines after the second flight, curls!

I make my own lines from 7 strand X .015 from MBS. Before I make another set I would appreciate any advice.

Thanks

[Dan Berry]

You need to run the lines with them not hooked to a handle several times.

[Dave Harmon]

Each line will unravel slightly as tension is applied.
It gets worse over time and if not corrected will cause a huge snarl.
As Dan said....unhook from the airplane, then starting at the handle run out each line in your fingers to take out the twist that will cause the snarl.
I jam a couple of screwdrivers or ball drivers in the ground and hook the handle over it then run out the lines toward the open ends at the airplane end as I am cleaning up for the day.
Solves that problem.

[Tim Wescott]

You need to run the lines with them not hooked to a handle several times.

I just made it a habit to do that every time I run out the lines.  Clip the lines to the plane, unwind 'em, drop the empty reel on the line ends.  Walk back to the plane, grab the handle, run them out to the handle with my finger in between (or with a rag with denatured alcohol), clip 'em to the handle.  I've never had a twist develop.

[Cody bishop]

For 40 sized planes you need at least .018 I use power pro 100lb test fishing line they NEVER kink or twist they have are stronger I have neaver seen anyone have issues with them in my area we even use them for speed limit combat

[Steve Helmick]

Flew last Thursday for the first time this year, and had some problems with a new set of Tom Morris lines when I first tried to unwind them. Since I always hook the lines to the airplane first and leave the handle for last, it was logical and easy-peasy to walk each line out individually, pulling the line through a rag, then hooking the handle up. Gotta get the twists out of each line. I always hook the lines to the plane first, and handle last. One benefit is that at a contest, I can take the handle off, wind up the lines to the plane, but leave them hooked to the plane...saves them from getting stomped on by those who tend to do that sort of thing.

Flew four flights on the old SV-11/PA .51 last Thursday, partly because it's more suitable to fly off grass, and partly just because I wanted to revisit the old girl dog. Changed from CF 3-blade BE prop to cheap APC 12-4. Had to play with launch rpm, handle spacing, and leadout location, since I probably didn't fly it after the LO guide broke out of the tip rib and subsequent repair. It'll be better next Thursday, weather co-operating. Remind me to put in a new spraybar, Tim!    Steve

[Steve Helmick]

Can't argue with that...I'd guess that this was about the 2nd or 3rd time for me to have this trouble, in 60-ish years of flying CL. But that IS the solution!    Steve

[Curare]

How are you getting the lines off your reel? unwinding them straight off, (like a hose reel) or letting them spool off sideways, like a side-cast fishing reel? If you spool off sideways you'll be imparting a twist in the lines straight off the bat.

[john e. holliday]

I unroll the lines like a garden hose after connecting to the plane.   At end of day I walk the lines out after disconnecting from plane and using my allen driver to stake them to the ground.  Then roll/wind  them up on the reel.   I am converting over to the kite reels as they are more durable.

[Dave Hull]

Take some scrap cable material. Grab it with your hands a foot or two apart. Run it over the edge of a board or the edge of your bench with some tension in it. Everywhere it touched the edge will now be curly. When they serve the cable strands and then stretch it they are putting very slight yield and memory into the cable. That is why the strands stay together and it behaves like a larger wire, but is more flexible. When you do anything that re-stresses or reforms the cable you unseat the memory of it being twisted into a cable. There are lots of ways to do this.

You can start getting squiggles if you put some twists into the pair of lines by flying some loops, then try to brute force the twists when you run the lines out next time by either putting them between your fingers or by squeezing with a rag and pulling toward the handle. Do you keep pulling until the handle is hanging in the air and waiting as it untwists? Not always curlies, so there may be other things needed to cause that kind of damage. But certainly squiggles and kinks. As one of our southern hemispherical brethren mentioned, letting the lines come off the spool in loops (ie. not rolling them on or rolling them off; as in don't wind them like kite string!) will either put a lot more twists into a cable--or will take them out.

Combat line get curlies all the time when they cross lines and the circular cable cross sections are upset. Think point-loading again. Edge of bench is just someone else's lines, now.

I always figured that the reason that early in control line modeling, guys tried to use swivel line connectors, was to take care of individual wire twist. It would help neutralize some of the ways cables can be damaged, but not most ways and not the most likely ways. However, swivels were too weak and unreliable and caused way more serious problems than the minor line-handling issues that they helped... and were correctly outlawed in my opinion.

I always understood that the cable was effectively stretched during manufacture. But I have often taken a new set of lines and hooked them up to the fence and pull tested/stretched them before use. If they pop I'd rather they didn't do it when hooked up to hundreds of hours of work on balsa and paper. And, it should "seat" the strands if they weren't already tight. I use a gage because people are not well calibrated when you try to pull X-pounds. Overstressing them is probably just as bad as not testing them at all.

The toughest to handle are the .008 stranded 1/2A lines. But they fly so good ya gotta have 'em. If you can get used to handling those without damage, then all the larger sizes are easy. Solids have other handling issues....

McSlow

[John Watson]

I use a separate reel for each line , does anyone else do this? I don't have any problem doing that.

[David Ebers]

Thanks to all who took the time to give advice and experience. I'll treat my lines differently from now on.

I was able to salvage two of the four sets by running the lines individually disconnected from the handle.

I was surprised by this curling thing. The last time I flew control line was in the eighties. Back then I only had one set 60X.018 lines and a hot rock handle. I used this set on everything I flew from Jr satans to a Ringmaster to a Twister. Probably had several hundred flights with them. Rarely disconnected the handle, never cleaned them and they never curled.

[Ara Dedekian]

For 40 sized planes you need at least .018 I use power pro 100lb test fishing line they NEVER kink or twist they have are stronger I have neaver seen anyone have issues with them in my area we even use them for speed limit combat

         Ditto! I've stopped using steel lines. Patiently waiting for AMA to make Spectra lines legal in stunt.

         Ara

[Doug Moisuk]

So 50 years ago we used swivels on both ends of the lines. We stopped that due to strength issues with that. But I still remember line curls?

[Dave Hull]

Agree, Doug.

I'd bet that most squigglies come from lateral pressure from handling, like doing a bunch of loops on one flight, then brute-forcing the twists out with rag or fingers as you walk out to the handle. Swivels would do nothing for you in this case. The individual lines don't need to untwist. Jamming your finger between the two lines and then pulling as you walk out is just one way to abuse lines....and I’ve tried them all.

Dave

PS--One thing that I think is unfortunate because it obscures what is going on is that a lot of guys call these stranded steel cables "braided." Well, they aren't. Braiding is a very simple weave that can hold things together. Hair is braided.  Outer jackets on avionics electrical cables may be braided (or woven). Ground strap material is woven. The cable lines we use are served into a twist and the pretensioning and memory holds them that way. Most of these are 1x7 configuration which means it has one strand comprised of seven wires arranged with six in a hexagonal pattern around the single core wire. (Technically this is now called a “strand” by cable guys. Multiple strands become a “cable.” Except with a 1x7 configuration, the strand is the whole cable.) Some fliers are using a 1x19 configuration which is more flexible, but the downside is that the individual wires are more susceptible to damage. The theoretical strength difference is minimal, something like 4% higher for the 1x19 in new condition just because the packing is more dense. I think with the standard helix, the stretch in the 1x19 is somewhat larger. The stretch in something like StayStrates (Progress Aero Works) or the older StayStrates(?) should be even less for an equivalent cross section because the wires are soldered together and do not tend to untwist and lengthen under tension. If you damage these wires due to abuse you really regret it because they are more expensive. I've made a lot of these line sets....

PS2--The mil specs for stainless aircraft cables used to specify the prestretching load to be 50% of the rated load for 5 seconds. The idea in control applications (rudder cables, elevator cables, etc.) was so that after rigging they did not become slack after a few flights. This kind of sounds like what we do every pull test, no?

[Dan Berry]

Brand new lines need to be de-stressed individually. Maybe this wasn't the case in olden times but I have figured out that it is true now.

[M Spencer]

Too Small a REEL ,

The Mega Snots in N Z in the early 70's used " 14 inch Reels ,

To run out lines IN the Circle , and reel in ' efficently .

But the big thing was they didnt ' curl up . Tales by the Fireside elaborated this , back then . There . 

[phil c]

Stresses are built into stranded lines when they are made, by the process.  Seven strand lines generally have a center strand wrapped with the six other strands.  The outer strands are twisted as they are wound around the core strand.  The twisting and wrapping have to be very carefully balanced to make a straight cable.  Every time the cable is stressed by pull or vibration the strands tend to reset and may cause a twist.

Separate and untwist the lines after every flight.  As said, you may have to untwist each line separately by running them out several times to get the twists out. Wrap them up with as little tension as possible.  Just the tension from winding the lines up can introduce twist.  Two separate line reels certainly doesn't hurt  but properly made lines won't have a problem on a single reel.  Even our hand winding up a set of lines on a reel puts quite a bit of tension on the inner strands.

At one point we got a large roll of line, over 1000ft.  We never got a single set of lines off that reel that didn't have bad problems getting twisted after every flight.  At times they would twist up so badly we couldn't even get them separated without getting a kink.

[David Ebers]

Could be I'm hurting my lines when I make them. I anchor the first made end, unroll the line to a table that has a wrapping jig set at what ever length I want. I pull/stretch the line, clamp it and wrap the end. I don't know exactly how much I pull/stretch. It's quite a bit more than a normal flight load, probably closer to a pull test load.

[jfv]

How are you wrapping them around the reel?  If you hold the reel and wrap the lines around the reel with your hand, the lines will twist.  You need to spin the reel to wrap the line on the reel without touching the lines.  Just a thought.

[Dave Hull]

Obviously, a pull test load is not supposed to damage the lines. The problem is that it is very hard to know how much pull you have applied without using a scale. Your method appears to require you to pull the line pretty tight so that you can use a jig. I don't use a jig, I just hand wrap them after marking to length. That way I can do the wrapping under some good light, and up close. (Nearsighted.) So finger tight on both lines to match the lengths works for me. This assumes that both lines come off the same spool of wire so any differences in fabrication are minimal. Because I use very fine serving wire, there really is no need for a jig, because you don't need any force to make the wraps. So the first time I load up the lines is in a load test before I hook them up to a plane.

Obviously different methods work, and some suit a person better than others.

Still, if you get squigglies on properly built new lines after an initial pull test, and when you know you let the individual lines untwist when you laid them out the first time, I would say there is something wrong with the wire. I have seen some .015 wire that seemed like it was not circular is cross section. You could see it, and perhaps a characteristic like that makes them more prone to squiggles.

The worst lines I ever had were some solids for one of the higher power racing classes. It really was not the correct wire. They came off of a too-small spool, and we were suspicious that they did not have sufficient temper. It was impossible to straighten them without a wire straightening machine (rollers) and so we only flew them once before we folded them up and threw the snarl into the dumpster. Probably most of us can relate to your frustrations. Wish you the best of luck figuring out what works for you!


Dave

Ref.

Solid wire straightening roller

https://www.novoprecision.com/products/precision-wire-straighteners-lubricators/?msclkid=d5763295f55412e04ccd6912f2f814dc&utm_source=bing&utm_medium=cpc&utm_campaign=Equipment%202&utm_term=wire%20straighteners&utm_content=Wire%20Straighteners

[eric rule]

I spoke to my cable supplier a few days ago about this issue. He explained to me that when they manufacture the cable ( 1 X 7 which is a center strand with 6 strand wrapped around the center) they have to make certain that they "stress relieve" the individual strands before they wrap (twist) them. If the individual strands are not properly stress relieved the finished cable will inevitably curl up. He said what you end up with looks like an old time fishing line that snagged after cast when you used an old style rod and reel.

I suspect you may have experienced a bit of this problem with your lines.

As you seem to have solved the problem you should continue "walking the lines" with a rag after each use.

[Ara Dedekian]

Too Small a REEL ,

The Mega Snots in N Z in the early 70's used " 14 inch Reels ,

To run out lines IN the Circle , and reel in ' efficently .

But the big thing was they didnt ' curl up . Tales by the Fireside elaborated this , back then . There . 

       Our club got a donation from a 90+ year old gentleman of his C/L planes and equipment. Mohawk 29s, OK 29s, a Cox Spacebug etc. so I'm quessing stuff from the late '50s early '60s. His line reel was a ~16" bicycle wheel. We thought he was daft. Who knew!!

       Ara

[Dave Hull]

The bicycle wheel thing may have had it roots from flying big speed jobs. Those use large solid wire(s) that do not tolerate little dinky plastic spools. Old bike rims worked pretty good. And you sure don't want a reel that will get away from you. A bunch of thick music wire is just a big spring, waiting to release all that energy you just wound into it.  Ka-Zing! Of course, you could make something custom that might suit you better than a bicycle wheel--but that's a lot of work!

Dave