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d_goldsmith

Breakcord

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I like the surgeon's knot. Thanks Michael.

I just realized that since it's a double loop the force applied to it is divided between the two strands. And the knot reduces the stength a bit. Anyone know the average percentage of strength lost on a surgeon's knot?

Has anyone ever used anything other than 80lbs break tape?

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Yes, the knot should in theory be the weakest link. Don't know about a surgeons knot for strength but on a climbing rope the figure eight knot is one of the strongest at 80% of the rope's weight/shockload rating.

So, would you not then expect break-cord to break at the knot!??! All the times I have found or seen the break-cord after a jump, it never seems to come apart near the knot. Any thoughts?

Also, I have heard as someone mentioned earlier about tying in lower down the bridle. I have always used the the PC loop with an extra piece of static 5or6 mm climbing cord to actually attach the break cord to. IN my thoughts, there shouldn't really be anymore shock load to the canopy/system even with an extra 3-4 feet of bridle because the break-cord will still break at the same amount of force. Any thoughts/explanations on this or really good reasons to tie into the bridle lower!!?

Thanks
SabreDave

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Has anyone ever used anything other than 80lbs break tape?



I have used fishing line, electrical tape and cotton twine. I know people who've also used condoms, plastic shopping bags and various other kinds of line.

Honestly, I think I'll stick to break cord until someone demonstrates that one of the alternatives is clearly better, which hasn't happened yet.
-- Tom Aiello

[email protected]
SnakeRiverBASE.com

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Any thoughts/explanations on this or really good reasons to tie into the bridle lower!!?



When they were doing the demo jump at the Superbowl, Apex had to do a bunch of drop tests to satisfy the various powers that were involved in the event. They found that tying break cord at the end of the bridle had a noticeable rate of premature breakage (if I recall correctly, Jimmy told me it was 1 in 20 or something), but that tying the cord halfway down the bridle reduced the premature breakages to the point that they were unable to create any with repeated test drops. They created bridles with sewn in loops to static line from, about halfway down, just for that demo.

An easy way to tie in partway down is to put an overhand loop in your bridle and tie to that.
-- Tom Aiello

[email protected]
SnakeRiverBASE.com

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Any thoughts/explanations on this or really good reasons to tie into the bridle lower!!?


Jimmy told me it was 1 in 20 or something), but that tying the cord halfway down the bridle reduced the premature breakages to the point that they were unable to create any with repeated test drops. They created bridles with sewn in loops to static line from, about halfway down, just for that demo.

An easy way to tie in partway down is to put an overhand loop in your bridle and tie to that.



Good to know. I mean, I heard different things from different people as you always will in this activity. I do always use the double break-cord method since premature breakage was obviously a concern at S/L heights. I must say one of the main reasons I have not done it that way is management of the bridle/ PC. Having seen others do it this way and lots of videos and some horror stories I didn't like the looks of it soo much. I liked having the PC right up at the S/L, bridle s-folded in my hand so the PC can't catch wind, dance around swinging 4 feet of bridle with it etc... I will however try it next time. I like the idea of having a bridle with sewn in point on it.
SabreDave

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So, would you not then expect break-cord to break at the knot!??! All the times I have found or seen the break-cord after a jump, it never seems to come apart near the knot. Any thoughts?



the knot is not the only stress concentration the cord sees

it also sees stress concentrations at both ends where it is attached to your bridle and the object


how you choose to attach it to the object and your bridle will determine how high those stress concentrations are and most likely it will break at the point of the highest stress concentration

unless of course there is some material defect in teh cord, in which case it might break there instead

which is why not only do I always use the double loop method, I always use different colours for each loop, to ensure I don't get both loops from the same batch of breakcord, or even worse, from the same area on the same batch of breakcord...

I have found that using 550 cord to tie to the object and a small rapide link to attach to my bridle, that even with an overhand knot the breakcord doesn't break at the knot.

in addition I have seen a really smart carry-with you set-up that carries EVERYTHING you brought, away with you...

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One of Nick's carry with you does exactly that, it carries even the broken cord that broke. However chances are the cord won't stay on the object anyway and if you are a tree hugger, cotton is biodegradable so you should go and find the TG rubber band!

The surgeon knot strength reduction is about 20-30% for those interested so the overall strength of a break cord loop is between 112-128 LBS. Also the 80 LBS rated strength is the minimum strength not the maximum. Also cotton is hydrophilic so its strength will vary according the humidity.

And d_goldsmith, you really seem to love posting mindless threads on topic that have been beaten to death. The I is not the place to learn BASE!

A S/L jump is the most mindless thing to do however people still kill themselves due to miss-rigging. Before you go and kill yourself seek advice from real experienced BASE jumpers not virtual ones. And if you want to keep the saga of mindless posts please learn from Maggot, at least his threads are funny as shit and he does not try to learn anything in here.
You know you have a problem when maggot is the voice of reason at the exit points

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I just got some great advise from "real experienced base jumpers" right here on "the I". Isn't that one of the greatest points of this forum?

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Any thoughts/explanations on this or really good reasons to tie into the bridle lower!!?



When they were doing the demo jump at the Superbowl, Apex had to do a bunch of drop tests to satisfy the various powers that were involved in the event. They found that tying break cord at the end of the bridle had a noticeable rate of premature breakage (if I recall correctly, Jimmy told me it was 1 in 20 or something), but that tying the cord halfway down the bridle reduced the premature breakages to the point that they were unable to create any with repeated test drops. They created bridles with sewn in loops to static line from, about halfway down, just for that demo.

An easy way to tie in partway down is to put an overhand loop in your bridle and tie to that.



That is some very interesting piece of information there. One thing popped up my mind though, if you tie the breakcord halfway down the bridle, how do you control the rest of the bridle (the upper part) and the PC ? Do you just let them hang below the exit ? Doesen't that have very high risk of bridle entanglement with the object since bridle is making a "loop" at the exit point ? That of course is no consern if exit point is "clean" and overhung (like the one in superbowl) but if you are SL'ning from cranes, A's ect it could be an issue. Any thoughts about that ?
http://www.ufufreefly.com

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One thing popped up my mind though, if you tie the breakcord halfway down the bridle, how do you control the rest of the bridle (the upper part) and the PC ? Do you just let them hang below the exit ? Doesen't that have very high risk of bridle entanglement with the object since bridle is making a "loop" at the exit point ? That of course is no consern if exit point is "clean" and overhung (like the one in superbowl) but if you are SL'ning from cranes, A's ect it could be an issue. Any thoughts about that ?



The chances of the bridle and/or PC entangling the object are much, much higher using this method. I really do not like it regardless who and where it was used. I know of at lest two incidents where this method could have resulted in two fatalities. TowerTopper can chime in hopefully sharing his view on this (one of the two incident).
You know you have a problem when maggot is the voice of reason at the exit points

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One thing popped up my mind though, if you tie the breakcord halfway down the bridle, how do you control the rest of the bridle (the upper part) and the PC ? Do you just let them hang below the exit ? Doesen't that have very high risk of bridle entanglement with the object since bridle is making a "loop" at the exit point ? That of course is no consern if exit point is "clean" and overhung (like the one in superbowl) but if you are SL'ning from cranes, A's ect it could be an issue. Any thoughts about that ?



The chances of the bridle and/or PC entangling the object are much, much higher using this method. I really do not like it regardless who and where it was used. I know of at lest two incidents where this method could have resulted in two fatalities. TowerTopper can chime in hopefully sharing his view on this (one of the two incident).



You could stow the remaining bridel with a rubber band to keep it together.

edit:
when I say stow I mean to just s-fold the remaining bridel and keep it together with a rubber band...
Michi (#1068)
hsbc/gba/sba
www.swissbaseassociation.ch
www.michibase.ch

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One thing popped up my mind though, if you tie the breakcord halfway down the bridle, how do you control the rest of the bridle (the upper part) and the PC ? Do you just let them hang below the exit ? Doesen't that have very high risk of bridle entanglement with the object since bridle is making a "loop" at the exit point ? That of course is no consern if exit point is "clean" and overhung (like the one in superbowl) but if you are SL'ning from cranes, A's ect it could be an issue. Any thoughts about that ?



The chances of the bridle and/or PC entangling the object are much, much higher using this method. I really do not like it regardless who and where it was used. I know of at lest two incidents where this method could have resulted in two fatalities. TowerTopper can chime in hopefully sharing his view on this (one of the two incident).



You could stow the remaining bridel with a rubber band to keep it together.

edit:
when I say stow I mean to just s-fold the remaining bridel and keep it together with a rubber band...



You could of course but wouldn't it be better to make a custom length (shorter) bridle for SL-purposes (and possibly ultra low FF) ? Then you wouldn't need to worry about the excess bridle.
http://www.ufufreefly.com

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wouldn't it be better to make a custom length (shorter) bridle for SL-purposes (and possibly ultra low FF) ? Then you wouldn't need to worry about the excess bridle.



Would it? Wouldn't that put the tail of the canopy even closer to the object and for what benefit? The purpose of the bungee isn't to short-line the bridle, it's to manage it until it is time to pay out in the deployment sequence. Also, what happens if the static-line breaks prematurely and you are towing the pilot-chute in your burble with a really short-bridle at very low airspeeds?
Skydiving Fatalities - Cease not to learn 'til thou cease to live

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wouldn't it be better to make a custom length (shorter) bridle for SL-purposes (and possibly ultra low FF) ? Then you wouldn't need to worry about the excess bridle.



Would it? Wouldn't that put the tail of the canopy even closer to the object and for what benefit? The purpose of the bungee isn't to short-line the bridle, it's to manage it until it is time to pay out in the deployment sequence.



I was referring to a case where you tie the breakcord halfway of the bridle, for example the Superbowl jump that Tom A commented on earlier. I don't see how normal length bridle in that case is paying out on deployment sequence if the breakcord is suppose to hold (almost) as long as you have bottom skin inflation.

Quote


Also, what happens if the static-line breaks prematurely and you are towing the pilot-chute in your burble with a really short-bridle at very low airspeeds?



The subject of the existence of burble on low airspeeds has been discussed pretty thoroughly here and I agree that there are different views about it.

I use normal lenght bridle, also on SL but the idea of a shorther bridle came up to me when Tom told the details of Jimmys tests for preparing the superbowl jump. I could think that shorter bridle would have the benefits of "breakcord halfway down the normal bridle" -setup but the jumper would not have to worry about "stowing" the excess bridle and getting it possibly entangled with the exit point. I agree that using a shorter bridle would have the downside of the PC being caught in the burble in case of breakcord premature break but then again if the breakcord (which is halfway down the bridle) breaks prematurely and the "excess" bridle is stowed away with bungee wouldn't there still be a risk of PC getting caught in burble since the bridle is actually shortened by the bungee ?
http://www.ufufreefly.com

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Yah, but it takes a lot less force to pull the bridle out of a bungee than it does to get you to line stretch. cpoxon must not have read the whole thread, but I was going to write the bungee idea until I read that he had coverred it.

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When I static line I like to attach the SL as close to the shrivel flap/pins as possible while still allowing me to stand-up at the exit point. In fact, I'll bring several different lengths of static line to still allow me to attach close to the pins and still stand up. (ie - If I'm standing on a platform and tying off to the platform the SL needs to be longer than if I'm tying off to a rail that's right behind my back.)

What to do with the extra bridle? The same thing I do on a handheld jump. I s-fold the bridle up to the pilot chute in my hand and execute a throw-and-go on exit. I pitch up and out to keep the bridle and PC away from the object yet ready to inflate if the break cord breaks prematurely.

Why do this? The shorter the static line, the lower the shock-loading applied to it at SL stretch. It probably means more with a shrivel flap than pins, but at heights lower than 150 ft, anything I can do to avoid a premature breakage of the break cord, I'll do. Also, pitching the PC up and out puts it above and away from the object.

I have video of this technique and the PC is inflated VERY quickly after the break cord breaks. Of course, canopy is inflating at the same time, but it sure looks like that PC is ready to do its job. (This was a 143 ft B with a 50 ft palm tree directly below and a 90 right required for landing.)

It's time now! My time now! Give me mine. Give me my wings! - MJK

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what happens if the static-line breaks prematurely and you are towing the pilot-chute in your burble with a really short-bridle at very low airspeeds?


you wont have a burble at werry low airspeeds..(my belive:P)

I can see serval places were i could/might would use a shorter bridel,i however hasnt done it yet,as you stated above what bennefit should it give(besides perhaps ULTRALOW FF-another dissusion)on a SL jump..
IF the object is so LOW that you need the extra few feets as safe magen,your in the wrong spot and shouldnt do the jump..

How low do people think of low as they speak SL?

Personaly im below 130ft or so if i really want to change my config on my gear as of right now..
doing a regular SL off 140ft will give you "plenty"(enough if you know the envioment) time to pop toogles and even do a slight turn and still land safely on hard ground..(my last jump off 140ft in strong headwind-sl off a S gave us 4-5 secs in the air(inkluding falling),we poped toogles and landed at grass just below exit point,off the same object in more ideale winds i had even more time..

IF you want to jump in the low end you better be thinking fast and feel good about your timeline from exit to landing,and be ready to hold on to your arse if somthing goes wrong,things happens really fast in that envioment, i still think my 0.78 loaded Vented Flik flyes as fast as my old xfire 99,when im flying down there,i have the same amount of time if not less to correct if i need to..

Craig,the above aint stated to you or respond to you personaly its just my humble oppinion,take it whith a grain of salt:)

Stay safe
Stefan Faber

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would a direct bag be better in this case at 111'.



It depends. A direct bag will get you open higher, but there are a couple of things I really like about s/l:

First, it is consistent. There's no chance of the bag being held a bit cockeyed. If something does go wrong, it's very likely a mechanical failure of some sort. Certainly, I won't leave behind a bag holder who will always wonder if he did something wrong.

Second, it's quick. If I tie the break cord onto a karabiner which is attached to a short leash beforehand, I can quickly get out of the vehicle, throw the leash around the railing, climb and jump.

If I was going sub-100, I would consider a direct bag, but obviously I'd need to have done a lot of practice with the bag holder beforehand.

Michael

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Absolutely 980… Thank you for your post…

Dave Goldsmith – You have numerous resources up here to answer your questions… If you would have asked me, I would have told you about dynamic force… If you drop a 5lbs weight at desk high level, it will break 80lbs cord.

Again, as 980 said, do your research before asking such basic questions…

Michael

BATMAN - (A.K.A. SBCmac ...)


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My bad... The actual experiment that I was taught is below:

“ Conduct a simple experiment to demonstrate this dynamic force. Attach a 9 foot bridle to a fixed point (the ceiling). At the bottom, attach a 5lb packing weight. The two are attached by a 80lb break cord. The 5lb weight is dropped from the ceiling and allow to freefall 9ft. The 5lb weight will generate enough dynamic force to break the 80lb break cord.”

Again… Dave – these are basic principles you should know before BASE jumping…

Michael

BATMAN - (A.K.A. SBCmac ...)


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Not to mention, here are the 612 search results that talk about BASE static line jumps on this site:

http://www.dropzone.com/cgi-bin/forum/gforum.cgi?do=search_results&search_forum=forum_22&search_string=static+line&search_type=AND&search_fields=sb&search_time=&search_user_username=&sb=score&mh=25

It took me 5 seconds to pull these via the built in search on this site...

Michael

BATMAN - (A.K.A. SBCmac ...)


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Yea, that would have to be a very tall desk.. ;)

From 9 ft it should take about 0.75 sec to fall, reaching 24 ft/s velocity with a momentum of 120 lb ft/s. Because it's deccelerated quickly(over a very short amount of time) it generates more force on the cord (more than 160 lbs) than just it's momentum.

Or something like that... ;)
"The evil of the world is made possible by nothing but the sanction you give it. " -John Galt from Atlas Shrugged, 1957

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Exactly the point... This is where the knot comes into play, because you can prematurely break the cord with the wrong/poorly done knot.

BATMAN - (A.K.A. SBCmac ...)


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