sigma tension knots

[skydiveoc 0]

As some may have read in previous posts, Im having unusual number of Sigma 370 chops due to tension knots in steering and D lines.

So here I am again sniveling open watching the usual slack dance of the rear riser group while the fronts are taught. So I grab the rear and pull slightly and bingo...all the lines in the rears tighten up, slider eases down. Does anyone find this technique to minimize the knots?

So...maybe the canopy is trimmed funky with alot of forward pressure on opening? Anyone have any thoughts here? This canopy has less than 100 jumps on it and seems to have alot more slack during the opening than the others. It has been chopped twice.

josh

[AggieDave 6]

I do that as well. Something I found is that with a worn but still good lineset if the packers aren't untwisting the control lines (and flare toggles) then the cascade twists and flattens out. THAT grabs the hell out of the C/D cascade and is where I've had a number of tension knots (some that ended in chops, some were cleared with the aforementioned technique).

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[efs4ever 3]

I've had three of them. Thank you for that observation. I'll try it "next" time.

Russell M. Webb D 7014
Attorney at Law
713 385 5676
https://www.tdcparole.com

[crazydiver 0]

a;lskfjasl;kjf the Sigma tension knots... hate them...so common...

We thought it was an altitude thing for us at Mile Hi being at around 5000 ft. msl field elevation. There has been a number that I have been unable to clear and have gotten violent, but the riser thing works. I've pulled on the rears then let them snap back to full flight and that has worked (sometimes).

Love the Sigmas...favorite tandem canopy...hate the tension knots. I think the dacron lines could have something to do with it also since they tend to get "sticky" as they wear.

Cheers,
Travis

[skydiveoc 0]

It seems PD has taken the route of the rest of the aviation industry...must be the user's fault. Bad packing.

I cant believe they can ignore the response of the industry in regards to the dacron line including they're very own Skydive Deland now jumping Precision and Icarus because of the cutaways believed to be caused by the Dacron.

PD stated before they would never make a tandem main with Microline or Vectran because of the opening shock. I guess they would rather see fatalities caused by an increased chance of double mals (packer or rigger fault they would say) vs injuries from hard openings (manufacturer's fault).

I phasing to Icarus one canopy at a time.

[riggerrob 558]

That techinque also works on "most" of the tension knots on Strong tandem mains.
I tend to use steering toggles, pull them down into a stall, then throw my hands up rapidly.
Most of the time, tension knots fall out as the lines go slack.

[crazydiver 0]

Quote

It seems PD has taken the route of the rest of the aviation industry...must be the user's fault. Bad packing.

I cant believe they can ignore the response of the industry in regards to the dacron line including they're very own Skydive Deland now jumping Precision and Icarus because of the cutaways believed to be caused by the Dacron.

PD stated before they would never make a tandem main with Microline or Vectran because of the opening shock. I guess they would rather see fatalities caused by an increased chance of double mals (packer or rigger fault they would say) vs injuries from hard openings (manufacturer's fault).

I phasing to Icarus one canopy at a time.

I'm not 100% sure, but I think the dacron line choice comes from Bill Booth and UPT not PD. Although PD manufactures the canopies (and wouldn't want to sell a product with components that cause issues for the user) I think that UPT has the ultimate decision as to the line choice on the canopy since it is a UPT product that is simply manufactured by PD. I remember Bill Booth saying some time ago that he never wants spectra or vectran on his tandems due to the opening force absorption of dacron.

Cheers,
Travis

[skydiveoc 0]

Of course they want dacron...so they can boost the sales of freebags, pilot chutes, drogues, risers, mains...with all those cutaways.

Actually, I think I do have a problem canopy. Rear line groups are consistently jiggling slack on opening while others in the lineup are remaining taught. Think I'll send it back for a trim check.

[skydived19006 4]

How do the Sigma canopies open? Are they consistently slow, similar to Icarus, fast, or inconsistent? Anyone willing to admit changing line type on a Sigma canopy to something other than Dacron?

That said, it's generally not that simple. You could slow the deployment with a slightly larger slider, but now you're really screwing with canopy design, etc.

I agree, I'd rather jump Icarus even if you prefer the Sigma flight characteristics to get away from the tension knot issue. I have over 1500 jumps on Icarus tandem mains (zero malfunctions), and could count on one hand the number of times (actually I think once) I've seen a tension knot, and the canopy was open and flying, just cleared it with steering toggle.

Experience is what you get when you thought you were going to get something else.

AC DZ

[Mixoligist 0]

I've found the best way to aviod tension knots on our sigma is to use the icarus 330

..................................
Better you than me
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[matthewcline 0]

For the last two days I have been going back through my log books and see I have over 600 Sigma jumps (combo of 340, 370 and 395).

I have never had a tension knot.
With the others (Precision, Rage, HOP etc) only the EZ-384 (not mine but the DZ's) got chopped for issues (line over I could not clear with the toggles, it was a steering line, poor packing was the cause).

Most of the pack jobs are PRO but a few are stacked as well.

I think this particular canopy is out of trim, but I am not a rigger, just a UPT I/E.

Matt

An Instructors first concern is student safety.
So, start being safe, first!!!

[skypuppy 1]

In just over 500 Sigma jumps I've had 3 chops for tension knots and seen at least 2-3 others that I've cleared. I know of at least two others that were chopped for that reason last year at our dz. It does seem to happen a lot.

If some old guy can do it then obviously it can't be very extreme. Otherwise he'd already be dead.
Bruce McConkey 'I thought we were gonna die, and I couldn't think of anyone

[matthewcline 0]

But is it truly a "canopy design flaw" or a packing style flaw? or lack of packer attention?

I don't know, all I know is what I posted.

Matt

An Instructors first concern is student safety.
So, start being safe, first!!!

[billeisele 122]

Quote

That techinque also works on "most" of the tension knots on Strong tandem mains.
I tend to use steering toggles, pull them down into a stall, then throw my hands up rapidly.
Most of the time, tension knots fall out as the lines go slack.

tried that technique on Sunday no luck, maybe not rapidly enough

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