Wear and tear from static line.

[SWOOOPDUDE 0]

I did a quick( because a;my computer time at work is limited, and b;I'm a lazy bastard.) search and didn't find anything so I'll throw this out there. What kind of usual or unusual signs of wear and tear do you guys/girls see on your canopies from frequent static lining? I check the usual stuff; bridal, bridal attatchment point, top skin, bottom skin, ribs, line attatchments.......am I missing anything?
Kinda thinking the center b's and c's are taking the bulk of the force needed to break the sl. ??

[nicknitro71 0]

In a S/L set up the break cord breaks at around 80LB so usually there should not be more than 80LB of force that is applied to any component of the rig.

In constrast a 28" Z-po PC will pull with a force of 160 LB at terminal. I assure you that BASE canopies are built much stronger than Skydiving mains...

Bottom line: no sweat unless you are doing something very wrong with your S/L set up.

Memento Audere Semper

903

[lifewithoutanet 0]

This isn't specific to your question, but I think there's a lot of good info in what follows that could be applied contextually to what you're asking.

I got the following from some Emails I exchanged w/ Martin Tilley at Asylum regarding strengths of different points of a canopy and am reprinting with his permission.

Credit goes to:
Martin Tilley- Asylum Designs / Adam Filippino- Consolidated Rigging

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Per Mil C-44378 T/1, 0-3(standard type use/"normal" fabric for parachutes) type cloth has a 47psi tensile strength and 5 lb tear strength (warp and fill). On the bias, these numbers are higher.

However, the strength of the canopy in the context mentioned really has more to do with the reinforcement tapes than the fabric. Loads travel from the line attachments which are rated at 600psi in tension, these loads are reacted by span-wise and chord-wise tapes in the seams and the v-tapes in the ribs. Ultimately forces are carried into the upper surface seams or into the bridle attachment assembly which will hold a minimum of 750psi.

We have not quantified the strengths of the canopy at any given point but have ensured that loads are carried through structures that can not only sustain all anticipated stresses but do so throughout the canopy's anticipated life.

Theoretically, when taken to failure, a well designed canopy will fail at the stitch holes between panels as this is the weakest link.

In practice, and by design, suspension lines fail first because the loss of one or two is less critical than a failure of the canopy.

If you are wondering what the strongest part of the canopy is. That would be the line attachments structure. This includes the attachment loops and all tapes radiating out from that point. This area sees the most stress.

The bridle attachment point is very robust, but principally for durability. It is not required to carry very high loads compared to the line attachments.

Hope this helps. Even if it doesn't, it's still some really good info to have.
-C.

[nicknitro71 0]

Nice reading.

Funny thing is that when my Viper blew up due to a 200kts deployment no line broke but the bridle attachment point ripped off the canopy and three cells ripped at the bottom skin fabric. None of the stitching ripped.

Memento Audere Semper

903

[base736 0]

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Funny thing is that when my Viper blew up due to a 200kts deployment no line broke but the bridle attachment point ripped off the canopy and three cells ripped at the bottom skin fabric. None of the stitching ripped.

You probably just did it wrong.

[lifewithoutanet 0]

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Funny thing is that when my Viper blew up due to a 200kts deployment no line broke but the bridle attachment point ripped off the canopy and three cells ripped at the bottom skin fabric. None of the stitching ripped.

Ah...that was due to the black rubber band you had larksheaded around your tailgate, then twisted and stowed around your canopy (a la lineover) into your bridle attachment point. Those damn things are STRONG.

Were there any other contributing factors to the self-destruction of your Viper? Age/# of jumps?

Not questioning you or doubting your knowledge one bit, just wondering how this could have happened. Any thoughts?

-C.

[TomAiello 26]

Also remember that a BASE canopy and a skydiving canopy like Nick's Viper may have variances in construction and deployment.

-- Tom Aiello

Tom@SnakeRiverBASE.com
SnakeRiverBASE.com

[980 0]

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In a S/L set up the break cord breaks at around 80LB so usually there should not be more than 80LB of force that is applied to any component of the rig.

I'm not sure how to explain this in a way that will convince all the skeptics, so next time I see you, please ask me to demonstrate:

-break cord is rated at 80lbs break strength
-standard static line set up uses 80lb break cord tied into a loop with a surgeon's knot
-this loop requires a breaking force of 2 times the breaking strength, reduced by a factor for the greatest stress concentration in the system (the knot you use, the link you use, etc.), which generally works out to just under 160lbs on the bridle

and no, this doesn't mean that this method will suspend you if you weigh less than 160 lb

cya
sam

[JaapSuter 0]

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which generally works out to just under 160lbs on the bridle

I just want to confirm this as well, having tested this using a tensile tester. We averaged 158 lbs.

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this doesn't mean that this method will suspend you if you weigh less than 160 lb

Unless you were to carefully lower yourself and very slowly increase the force on the break cord. You know this of course, I just felt like pointing it out...

[LouYoung 0]

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which generally works out to just under 160lbs on the bridle

Didn't someone in this thread do some real testing that shows that the breaking strength of a standard static line set up is around 100 lbs? (Or did I read it wrong?)

You start with 80 lbs, loop the cord giving you 160, then subtract that 40 percent loss from tieing a knot in the loop to get 97 lbs give or take.

Lou

[nicknitro71 0]

Yeah I follow the math but as Lou said there is a reduction in strength due to the knot.

Even if the overall strength is 160LB, it is about the same as a 28" PC at terminal so again I would not sweat over it.

As for my mishap with my Viper I guess skydiving main canopies are not supposed to be deployed at 200Kits! The canopy had no more than 150 jumps total and it was in great shape. Remember that BASE canopies are much more overbuilt than SD mains yet I would not delpoy them at 200Knts

Memento Audere Semper

903

[Faber 0]

i replaced a bridel so far but that were on a hang up whith the carry on sl,before i started to ude the "cut away cord" he he
did i ever tell i love that set up..

Stay safe
Stefan Faber

[SWOOOPDUDE 0]

Thanks guys. Hadn't called any manufacturers to see what people were telling them. Just curious to know if anyone had expierienced any failures due to frequent sl'ing. I'll give Todd or Jimmy a call.

[DexterBase 1]

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I'll give Todd or Jimmy a call

Or Martin Tilly at Asylum Designs. 530-823-5222
He knows a little about BASE jumping too.

[Faber 0]

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Martin Tilly at Asylum Designs. 530-823-5222
He knows a little about BASE jumping too.

that were werry humble.. he knows sh!it loads of stuff,only bad thing about him is that he didnt make a jump whith me this summer

Stay safe
Stefan Faber