Forums: Skydiving: Gear and Rigging:
sigma main having tension knot malfunctions

 


Frankie84

Nov 13, 2012, 12:51 PM
Post #1 of 6 (1067 views)
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sigma main having tension knot malfunctions Can't Post

Hi

in the past year or so my dz has had 6 malfunctions due to tension/pressure knots (3/4 way up lines) on a sigma 370 main

-the first 2 happened within 6 weeks of each other, we (Tm's) discussed packing technique with packers, in refference to line tension and line stowing.
- no mals happened for about 6 weeks, on the 3rd we thought it was possible it was due to the line set as the lines where due for a reline
- we didnt have another malfunction for about 4 or 5 months
- the last 3 have happened within the last 2 months

- all different packers packed the malfunctions one of which was the dzso
- all on the that sigma 370 alone, other sigma canopys havnt had issues with

any ideas on how to resolve issue


Deyan  (D 322)

Nov 13, 2012, 1:12 PM
Post #2 of 6 (1035 views)
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Re: [Frankie84] sigma main having tension knot malfunctions [In reply to] Can't Post

My first guess is bad lines.

My second guess is too weak rubber bands.

My third guess is the kill line is too short or the drogue is due for replacement.


AggieDave  (D License)

Nov 13, 2012, 1:35 PM
Post #3 of 6 (1007 views)
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Re: [Frankie84] sigma main having tension knot malfunctions [In reply to] Can't Post

Dacron lines?

Untwist the control lines, when they start to twist up the cascade flattens out and will grab the C/D cascade in front of it during opening. It gets MUCH worse as the lines age. 3 of my 4 tandem chops were due to this.


irishrigger  (D 297)

Nov 13, 2012, 2:08 PM
Post #4 of 6 (981 views)
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Re: [AggieDave] sigma main having tension knot malfunctions [In reply to] Can't Post

we had a huge problem with tension knots also. even on newly replaced line sets. the issue was with the brakelines especially, i emailed UPT at the time and there was a fix that you could do.
you have 2 brake lines, the primary and secondary breaks. the fingertrap where the brake lines cascades where the excact same lenght making a lot of bulk there. if you adjust that fingertrap on the secondary brake line, IE make it shorter so that they are off set from the primary lines, that will help matters considerably. although a new lineset should have that correction already built into them.as someone else mentioned make sure the line twist are taking out on the brakelines every couple repacks. i know its a pain in the bud but it does help and reduces cutaways. we had something like 25-30 of them in a year. but we have knocked that right down these days.
hope that helps
rodger


Frankie84

Nov 13, 2012, 3:10 PM
Post #5 of 6 (929 views)
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Re: [irishrigger] sigma main having tension knot malfunctions [In reply to] Can't Post

Yes dacron lines. we try and reduce the control line twist, if i have time under canopy i generally try untwist them or i ask the packers when i land.

I'll have a look at the length of the primary and secondry when im at the dz next.
Thanks


parafredo  (D 639)

Nov 15, 2012, 3:34 PM
Post #6 of 6 (750 views)
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Re: [Frankie84] sigma main having tension knot malfunctions [In reply to] Can't Post

I can say that on almost 5000 Sigma 340 or 370 dacron or Vectran, you can eliminate a lot of those only by making sure that the trap door is not to long. Ask Mark Procos about us at Voltige2001 dz and ever since we keep the kill line long enough, we never had this kind of mal .They did a bulletin about the length that you should have and believe me, line stretch make a big difference. As soon as you feel yourself in a too long trap door, you get a chance to get tension knots, happen more on old lines as well. We reline our canopies every season. Hoping that helps to solve your problems



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