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billvon

Replacing Nitro lines

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I just replaced the lower brake lines on my Nitro with Dacron (old ones were shortening a bit) and noticed a few things.

One, I made the stow to canopy length a few inches longer, and it definitely improved the openings. If I didn't occasionally use packers I would have put two or three catseyes in the line to vary the brake settings, just to see what would happen.

Two, the Nitro is cool in that you can replace every line on the canopy without sewing. I thought I would have to sew at least the upper fingertrap, but once I understood their scheme I realized I could build the lines first and then attach them.

BTW, since we don't have a bartacker I've been straight-stitching all the fingertraps. Anyone see any problems doing this?

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The down fall of sewing with a straight stitch on line is that the straight stitch has no elasticity so if the line stretches, the straight stitch is more likely to break where the bartack or zig zag most likely will not.
However, on most canopys, the bartack is there really as a back up and the finger trap is what actually provides the holding power.
Providing there is sufficient line contained with in the finger trap, you should be O.K. but you may want to have some one throw a few bartacks in for you just to be on the safe side.
K

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I just did. If you dig further in the PPM, you should find a section regarding the elasticity of different stitches and why and where they are used.
Once upon a time, I knew a woman who built her own canopy and did not know where to set her line trim for maximum opening performance and flight. So she simply did not put any bartacks in the canopy so she change the trim after each jump as needed. Worked just fine and the canopy went on to be a very successful product in the BASE world

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However, on most canopys, the bartack is there really as a back up and the finger trap is what actually provides the holding power.



The finger trap will hold when under load, the bar tack or zigzag is there for when the line is in a relaxed state. That is when a finger trap will shift and possibly come completely out.

That and it keep the jumpers from freaking out.:P

Or you can use this method.

Finger Trap

Sparky
My idea of a fair fight is clubbing baby seals

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I just replaced the lower brake lines on my Nitro with Dacron (old ones were shortening a bit) and noticed a few things.

One, I made the stow to canopy length a few inches longer, and it definitely improved the openings. If I didn't occasionally use packers I would have put two or three catseyes in the line to vary the brake settings, just to see what would happen.



Bill,
A straight sew works fine although it's not very pretty. What works even better is an overhand knot right @ the top of the finger trap (loop end). Using this method your loops will want to be a little smaller than with sewing. It works just fine and will never come undone, every jump makes the knots tighter. If you want to be really super sure the traps will not undo themselves, use the knot and straight sew method. In the days of round parachutes with core and sheathing type line it was the knots that did all the work not the stiching. Hell I even saw people shortlining rounds and instead of re-sewing they just used duct tape. Now that's really not pretty!

Mick.

Mick.
Two, the Nitro is cool in that you can replace every line on the canopy without sewing. I thought I would have to sew at least the upper fingertrap, but once I understood their scheme I realized I could build the lines first and then attach them.

BTW, since we don't have a bartacker I've been straight-stitching all the fingertraps. Anyone see any problems doing this?

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Bill, as I recall, your Nitro has the black Technora lines, is that right? If so, then your original factory lower control lines (or what many refer to as brake lines) were made of Dacron, and I can assure you that Dacron lowers do not shorten; if anything they elongate slightly with use.

It's really not surprising that lowering the brake settings (moving the cat's eye closer to the toggle) made the openings feel a little smoother; that is the case with many canopy designs. But what you need to remember is now your canopy will be flying faster after deployment, so that is a consideration for things like doing big-ways, etc.

If I understand your question, you're saying you used a straight stitch to make a new set of lower control lines. Here is the issue to consider; if you use a fiber for lines that has a good bit of elasticity, such as Dacron has, then a straight stitch is not a good idea, as the line itself will stretch more during opening than the straight stictch will. This will eventually lead to broken stitches. If, however, you use a line with little or no elasticity, then the nylon thread in the stitching will give more than the line itself and present no problem. So, long story short, with Dacron control lines you should use a zig zag or bartack to allow the stitch to "give" with the line during opening forces.

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>What works even better is an overhand knot right @ the top of the finger
> trap (loop end). Using this method your loops will want to be a little
>smaller than with sewing.

I thought about that, but a) I didn't know how much additional line I'd need to allow for the knot and b) the dacron line is thick enough that I was worried about the bulk where the slider passes over the upper line attach point. But I may try that as an experiment next time.

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>your Nitro has the black Technora lines, is that right? If so, then your >original factory lower control lines (or what many refer to as brake lines)
>were made of Dacron, and I can assure you that Dacron lowers do not
>shorten; if anything they elongate slightly with use.

Hmm, not sure why they seemed to be shorter then. They were getting short enough (or the other lines were lengthening enough) that the tail of the canopy was beginning to be deflected in full flight. Risers haven't changed.

> So, long story short, with Dacron control lines you should use a zig zag
>or bartack to allow the stitch to "give" with the line during opening forces.

Dang, and all I have here is a straight stitch. I guess we're going to need a new machine.

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>What works even better is an overhand knot right @ the top of the finger
> trap (loop end). Using this method your loops will want to be a little
>smaller than with sewing.

I thought about that, but a) I didn't know how much additional line I'd need to allow for the knot and b) the dacron line is thick enough that I was worried about the bulk where the slider passes over the upper line attach point. But I may try that as an experiment next time.



3/8" per knot the bulk is nedgebile the slider does'nt care.

Mick.

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>What works even better is an overhand knot right @ the top of the finger
> trap (loop end). Using this method your loops will want to be a little
>smaller than with sewing.

I thought about that, but a) I didn't know how much additional line I'd need to allow for the knot and b) the dacron line is thick enough that I was worried about the bulk where the slider passes over the upper line attach point. But I may try that as an experiment next time.



3/8" per knot the bulk is nedgebile the slider does'nt care.

Mick.






Ya know what? My bad, I didn't realize you were using 550 dacron, that is bulky. I was thinking 825 Spectre. Ignore the previous post.


Mick.

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The JS method for finger trapping does not work well with Dacron because it's too bulky. I love using it with HMA though.



Someone told me that before too. I didn't believe em and did the JS Fingertrap trick and it worked perfectly for my Dacron equiped stiletto. no problems with it at all.

Marc
otherwise known as Mr.Fallinwoman....

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