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ecolisurprise
Jul 10, 2011, 3:42 PM
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Tension Knot Specifics
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Hi Guys,
Does anyone have any specifics on the typical location of tension knots? For example,
1) where on the lines do they typically occur, above or below the slider stops?
2) Which line groups, control lines, inner or outer?
I'm trying to think of ways to prevent them.
Thanks
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DAVE858
Jul 10, 2011, 4:23 PM
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Re: [ecolisurprise] Tension Knot Specifics
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I would think that they would be more common on slider up jumps. Has anyone heard of or experienced tension knots on a slider off jump? As far as prevention goes, when I pack I always ensure that the red lines are to the inside of all the black lines. I run them up from the risers to the pack job & ensure none of the outer lines are wrapped around them. I am referring to slider off jumps, as I have not used my slider since 2 bridge days ago....
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Fledgling
Jul 10, 2011, 6:49 PM
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Re: [ecolisurprise] Tension Knot Specifics
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ecolisurprise wrote: 1) where on the lines do they typically occur, above or below the slider stops?
ecolisurprise wrote: 2) Which line groups, control lines, inner or outer?
ecolisurprise wrote: I'm trying to think of ways to prevent them.
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ecolisurprise
Jul 10, 2011, 7:02 PM
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Re: [Fledgling] Tension Knot Specifics
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I took some high speed video of a terminal opening of my ace260 w/ a 32'' vented zp pilot chute. i did a very neat flat pack on the thing, and it still looked like shit when it came out. Control lines were flopping around everywhere.
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SubTerminallyill
Jul 10, 2011, 8:47 PM
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Re: [Fledgling] Tension Knot Specifics
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Aren't tension knots typically on the steering lines? the way i see it is the toggles spin around after they they are released from your grip and they are not immediately stowed. they are then repacked with a twist in them. same for a situation where you released your toggles or the toggles were lost on an opening.
i was taught to walk the steering lines back from the canopy to the risers to untwist them during all pack jobs.
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Tedis
Jul 10, 2011, 9:07 PM
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Re: [SubTerminallyill] Tension Knot Specifics
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+1
That's it! I was told to untwist the steering lines on each and every packjob!
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Fledgling
Jul 10, 2011, 9:24 PM
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Re: [SubTerminallyill] Tension Knot Specifics
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SubTerminallyill wrote: Aren't tension knots typically on the steering lines?
SubTerminallyill wrote: i was taught to walk the steering lines back from the canopy to the risers to untwist them during all pack jobs.
Twisted control lines will tension knot more readily than twist free lines. So untwisting them helps to prevent tension knots but won't eliminate them.
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SubTerminallyill
Jul 10, 2011, 9:38 PM
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Re: [ecolisurprise] Tension Knot Specifics
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if your not already doing it... lay your canopy on its side. when its on its left side... pick up your furthest most right lines. (right steering and the line far most right on the rear riser and the line far most right on the front riser) walk them up to make sure they are in order.
next... grab all the steering lines and flake them out pulling back against the risers. make sure the tail section you are holding has the steering line attachment points in order and walk the line back to the risers untwisting the line.
i do this by squeezing tight on the steering line after the cascading lines with my fingers and walking it up to the risers. set the breaks and shaaazame... no tension knots in the steering lines.
repeat with the other side of the canopy.
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SubTerminallyill
Jul 10, 2011, 9:40 PM
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Re: [Fledgling] Tension Knot Specifics
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wait what? how will lines have tension knots if all lines are straight?
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TomAiello
Jul 10, 2011, 10:41 PM
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Re: [SubTerminallyill] Tension Knot Specifics
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SubTerminallyill wrote: wait what? how will lines have tension knots if all lines are straight?
Tension knots are not fully understood. They can certainly develop even in straightened lines.
Most documented BASE tension knots have occured between the control line cascade and the D line cascade.
I have good video of a slider down tension knot--it's on one of the early Will Forshay Bridge Day segments.
In my opinion, the most likely cause of tension knots is slack lines moving past each other prior to line stretch (i.e. canopy inflating out of sequence). The best remedy to this that we currently have available (and it's by no means certain) is to use the primary stow (locking stow) under the tail pocket, to help stage deployment such that the canopy reaches line stretch before it begins to expand.
Ecoli: Was your canopy free packed, or put in a bag? Skydiving rig or BASE rig? Did you use the locking stow? Did you use the tailgate with your slider for the terminal pack job?
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ecolisurprise
Jul 11, 2011, 5:10 AM
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Re: [TomAiello] Tension Knot Specifics
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Hi Tom,
It was put in a perigee pro with the primary locking stow under the tail pocket, with no tail gate.
(This post was edited by ecolisurprise on Jul 11, 2011, 5:13 AM)
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ecolisurprise
Jul 11, 2011, 6:09 AM
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Re: [TomAiello] Tension Knot Specifics
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In reply to: Most documented BASE tension knots have occured between the control line cascade and the D line cascade.
So this would occur below the slider stops?
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TomAiello
Jul 11, 2011, 6:18 AM
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Re: [ecolisurprise] Tension Knot Specifics
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ecolisurprise wrote: In reply to: Most documented BASE tension knots have occured between the control line cascade and the D line cascade. So this would occur below the slider stops?
Yes.
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ecolisurprise
Jul 11, 2011, 7:08 AM
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Re: [TomAiello] Tension Knot Specifics
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Pardon me if this is a dumb question, but why are cascades necessary? why not just have more lines?
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Fledgling
Jul 11, 2011, 7:18 AM
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Re: [SubTerminallyill] Tension Knot Specifics
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SubTerminallyill wrote: wait what? how will lines have tension knots if all lines are straight?
While it is possible to get a single line to tension knot on it self that is very rare. They usually occur when the D lines tension while the control lines are still amongst them trappping them in place. The reason it usually involves the control line and the D line cascade is because of the amount of lines present in that area (tandem canopies are prone to tension knots due to them havin 8 control lines). The reason you should untwist the brake lines is because neater control lines are less likely to hang up in the cascade for it to knot there.
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Fledgling
Jul 11, 2011, 7:30 AM
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Re: [ecolisurprise] Tension Knot Specifics
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ecolisurprise wrote: Pardon me if this is a dumb question, but why are cascades necessary? why not just have more lines?
Cascades aren't necessary. Many canopies are designed with continuous line sets. Not sure it would be a practical application for BASE as your line bulk would increase drastically. For the record every continuous line set i have ever seen still featured cascaded brake lines.
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Fledgling
Jul 11, 2011, 7:39 AM
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Re: [ecolisurprise] Tension Knot Specifics
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ecolisurprise wrote: Pardon me if this is a dumb question, but why are cascades necessary? why not just have more lines?
Also, this will not stop tension knots as continuous line sets still have their fair share of tension knots.
While tension knots occur around the D line cascade the cascade is not a defining factor just a convenient location. The D lines are significantly longer than the other lines and are left slack until it's their turn to tension. I believe it is this slack that allows them to get all messy and tangle with shit before they are tensioned.
For the record I have only witnessed BASE tension knots and have not experienced one my self. I have how ever chopped like 9 skydive canopies because of them so have had a good view of them from the drivers seat. But seeing as we are talking terminal jumps here it's all the same shit really. Once the canopy hits the wind and before the slider starts to move D lines can get messy.
(This post was edited by Fledgling on Jul 11, 2011, 9:46 AM)
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LukeH
Jul 11, 2011, 9:38 AM
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Re: [ecolisurprise] Tension Knot Specifics
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Are the thin slippery spectra lines of some slider up only base canopies less likely to have tension knots?
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Fledgling
Jul 11, 2011, 9:45 AM
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Re: [LukeH] Tension Knot Specifics
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LukeH wrote: Are the thin slippery spectra lines of some slider up only base canopies less likely to have tension knots?
In theory yes.
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hikeat
Jul 17, 2011, 2:34 PM
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I've been pondering if the tailgate or tape gate on slider up jumps could help to prevent tension knots. In theory if tension knots are caused by slack in the brake lines sliding past the d lines then a tailgate should remove the slack for at least the first stage of the opening.
Those that have experience with sl up tension knots, do you know if a tailgate or tapegate was used?
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TomAiello
Jul 17, 2011, 4:24 PM
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If the tailgate/tapegate is above the locking stow, how is it going to change anything? The cascades where the tension knot is most likely to appear are below the locking stow already, and I can't see adding the tailgate above the locking stow really doing much that the stow itself does not.
As a somewhat bizarre thought experiment, have you considered the idea of taping around the entire line bundle somewhere (or several places) along the length of the lines? Picture wrapping the lines with a loop of masking tape every 24" or something. Do you think that would change the incidence of tension knots?
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GreenMachine
Jul 17, 2011, 6:19 PM
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I had thought and sorta tried it,
on a Falcon 300, TARD, Perrine.
Worked well but too few jumps
to recommend it to anyone...
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kege
Jul 18, 2011, 8:44 AM
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Re: [LukeH] Tension Knot Specifics
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I had a thought the other day (yes I really did), when thinking about this tension knot business. Could the brake lines be made so that the final bits, everything above the cascades was made of a different, very slippery material?
I was thinking something unlike a regular line, but more like approx 1-2mm diameter synthetic material, kinda like super-heavy duty fishing line? And because of its slippery monofil structure it could be less prone to twist and turn on itself and its fellow brake lines?
The forces on the upper brake lines are not too great and the slider doesn't wear them down, so theoretically it would probably work. I sure don't know if it would help to avoid tension knots, but it might. What do you think?
Like I said this was a thought I had a few days ago. I don't get those very often and most of the time they suck.
Kerkko
BASE1184
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blitzkrieg
Jul 18, 2011, 11:07 AM
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Re: [kege] Tension Knot Specifics
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you should simply forget that you ever had that thought.
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