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Depower Lines Wear, Strength, Replacement

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Depower Lines Wear, Strength, Replacement

Postby Sun » Fri Aug 03, 2018 2:45 am

Gentlemen,

I have some Best Red bars, the ones that are essentially North bars on the chicken loop and QR, with Clamcleat trim blocks. See photos below.

My center lines (depower lines) are beginning to show some wear, especially near the point where they enter the QR. I have some questions about how much wear is ok, and what diameter rope to replace it with.

1) I see Dyneema rope like Amsteel has a breaking strength (when spliced) of at least 650kg for a 2.5 mm rope. Given that this style bar is supported by two ~4mm ropes, I am guessing there can be a decent amount of wear before things become dangerous. Is this true?

2) Does anyone know what the original diameter of the North / Best depower lines are? If I order some Amsteel, what is the appropriate diameter to use so that it threads through the QR correctly?

3) Best uses a bungee inside the rope where it passes through the plastic center line splitter. I will probably abandon this if I replace the rope with Amsteel. Is that extra thickness necessary for where the trim goes into the Clamcleat teeth? If it is, what is the appropriate material to splice into the Amsteel to give it some extra thickness?

4) I have not done any line splicing. What do you think is a reasonable quote from a local sail maker to make me a new depower line set using Amsteel?

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salvatoreone
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Re: Depower Lines Wear, Strength, Replacement

Postby salvatoreone » Tue Oct 23, 2018 7:52 am

Hi mate, I've got similar questions - my depower line is quite badly worn and want to replace it before anything bad happens.

Unfortunately nobody replied to your post... Have you sorted this out? Did you find any decent replacement for your depower line?

Cheers

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Re: Depower Lines Wear, Strength, Replacement

Postby Gyre » Thu Oct 25, 2018 3:02 am

Touching on Sun's questions 1 and 3 above: the depower ropes on my Flysurfer bars are a hollow ~4mm rope that has another rope (~2mm) inside it (similar to the way the bungee is threaded inside Sun's rope). That's for warning and for backup: if your thick rope is frayed enough that you can see the thin inner rope, then you know it's time to replace. And if you leave it way too long and the thick rope wears all the way through and breaks, you have the backup of the thin inner rope (strong enough to get you back to shore).
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Re: Depower Lines Wear, Strength, Replacement

Postby runner1 » Thu Oct 25, 2018 3:47 am

I have no idea about Best lines, but Naish do not have the internal lines shown by Gyre on Flysurfer

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Re: Depower Lines Wear, Strength, Replacement

Postby foilonfoil » Thu Oct 25, 2018 4:37 am

Many kite manufacturers use a depower line from Liros called D-Pro that has an additional coating on the Dyneema® to minimize abrasion.

Purchase depower line from the kite manufacturer or Liros for the coated version, or from Marine stores (Amsteel) for uncoated versions. Uncoated wears a little quicker. I myself have been using uncoated Amsteel from West Marine in recent months. Splicing is a fun hobby to learn... Plenty of youtube videos can demonstrate a modified (one end fixed) brummel splice. Splicing tools (fids) may set you back $10-$50.


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Re: Depower Lines Wear, Strength, Replacement

Postby Mossy 757 » Thu Oct 25, 2018 2:19 pm

I'd de-rig the bar, bring it to a West Marine, and get that stoutest Amsteel that slides perfectly through the hole in the bar without binding up a bunch.

That said, I use Ozone bars that have the poly tubing around the depower line and they're all literally perfect except where they go into/through the trimming mechanism unsheathed. No issues along the path of bar throw though.

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Re: Depower Lines Wear, Strength, Replacement

Postby collider » Thu Oct 25, 2018 3:45 pm

Splicing tools (fids) may set you back $10-$50.
Hollow aluminum knitting needles (cut at an angle) and guitar string (not wound) or picture wire (solid, not strands) attached to a cork will set you back less than that. No reason to buy expensive fids if you ask me.

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Re: Depower Lines Wear, Strength, Replacement

Postby kitexpert » Thu Oct 25, 2018 3:55 pm

1) No, it is not true. Fibers get weakened universally so depowerline may snap even though most of the thickness is still there. Fortunately it doesn't happen often and there is a lot of "excessive" thickness and strength in that line.

2) 5mm. This value is true when line is compressed. That is about the smallest diameter in which these lines go through.

3) It is not necessary, clam cleat will work. Bungee is for shortening free end when trimmer is pulled for depower. It is not very difficult to splice bungee cord inside of that kind of hollow braided line.

4) Do it yourself. Piece of steel wire or guitar string will do as a splicing tool. But there might be some issues with the clam cleat attachment with the thick spliced loop.

PU covered depowerlines are stiff and even stiffer when snowkiting. There might be also a bit more friction for the bar movement. Stopper ball and automatic untwisting are more difficult to have with covered depowerline, in many cases they just aren't there. Cover plastics do brake, in worst cases making bar unusable. Repair is more difficult than with unsheated bar.

Hole in the bar is not the limiting factor for the depower line thickness, it is the other parts line should go through.

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Re: Depower Lines Wear, Strength, Replacement

Postby kitexpert » Thu Oct 25, 2018 3:59 pm

collider wrote:
Thu Oct 25, 2018 3:45 pm
Hollow aluminum knitting needles (cut at an angle)
That is good one, thanks :thumb: In some cases fid is better than a piece of wire.

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Re: Depower Lines Wear, Strength, Replacement

Postby edt » Thu Oct 25, 2018 6:06 pm

typical sizes for those lines are between 2.5 and 3mm (1/8th of an inch) that's the one that goes through the north center (through the spinner) for the older mini 5th control bars, I think either will probably work, you should be able to measure that and figure out the exact size. typical chicken loop line sizes for other control bars are 5mm (3/16th of an inch) and those are often doubled. Remember that the strength of the rope is proportional to the cross section, not the diameter so a 5mm rope will be 4 times stronger than a 2.5mm rope. a 5mm line can hold about 2 tons while a 3mm line can hold about 1 ton, so typically the chicken lines on a control bar will be about 4 times stronger than it has to be and can be quite frayed before it snaps, while the north lines are a bit closer to spec, maybe only 2 times stronger than they need to be. Anyway, measure your old lines, I could be wrong about your line size! I typically ride all my gear until I snap a line, so from experience I can tell you that once it looks like a furry caterpillar it is about ready to snap, even if none of the strands in the 12 strand line are completely worn through. If you give up on the bungee inside the spliced line you can go with a thinner line, never had a problem doing that. Anyway those are the typical sizes, 3mm and 5mm (1/8th and 3/16th) doesn't hurt to have a bit of extra dyneema on hand, as the 3mm size is the same as your leaders and can also be used as a bridle repair. the 5mm is only useful as a chicken line replacement, as line that thick isn't used anywhere else.


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