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Sigma Tandem Mains

 


skydiveoc  (D 12721)

Sep 13, 2004, 5:10 AM
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Sigma Tandem Mains Can't Post

Yes I love Sigma mains too and I think they have less pressure than my Icarus 365 and have more bottom end punch. But...I have chopped 5 in the past two years and 0 Icarus chops. All due to tension knots.

Anyone have similar numbers?


tspillers  (D 21601)

Sep 13, 2004, 6:04 AM
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Re: [skydiveoc] Sigma Tandem Mains [In reply to] Can't Post

How is the weather out there?

I assume you are on 4 grommet sliders?

It sounds like time for a line set issue to me, but I would have to see the lines.

PM me if you have questions. I know RWS is working with getting things back to normal so PM me or call Skydive Aggieland. (I shouldn't be there today)

Todd


crutch  (D 10182)

Sep 13, 2004, 6:27 AM
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Re: [skydiveoc] Sigma Tandem Mains [In reply to] Can't Post

My Sigma is three years old now, been relined once, after about 650 jumps. I have had one tension knot in the front right line group, but I was able to "pop" it loose before my decision altitude. I do know that when packing them, if one is not careful it is easy to "bunch and twist" the lines up a bit, I really believe this is what causes the tension knots. I pack 99% of the the tandems I jump, I do think this adds to the fact I haven't had a cut-away yet.


billbooth  (D 3546)

Sep 13, 2004, 7:26 AM
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Re: [crutch] Sigma Tandem Mains [In reply to] Can't Post

Some DZ's go 1,000's of tandem jumps without any malfunctions...other DZ's have malfunctons every few hundred jumps..on identical equipment. Everybody has the same body position at drogue release, so the only possible variable is packing. Hint: DZ's who flat pack have the lowest malfunction rates by far.


Premier SkymonkeyONE  (D 12501)

Sep 13, 2004, 9:34 AM
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Re: [billbooth] Sigma Tandem Mains [In reply to] Can't Post

And that is about the fifth time Bill has posted that to the forums. Though we do now have a couple of packers at Raeford who we let PRO pack, the majority of us still flat pack our tandems. We have had zero tandem malfunctions on Sigma mains since we put them into service in 2001. In my opinion, FLAT is where it's at.

Chuck


tspillers  (D 21601)

Sep 14, 2004, 9:38 AM
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Re: [SkymonkeyONE] Sigma Tandem Mains [In reply to] Can't Post

We pro pack, but we take steps to put the lines back in the middle after laying the tandem down.

We don't do as many tandems as you guys, but we have only had one mal and flat or pro would not have made a difference. It was a walk through the was created when the bag was placed into the container.

If you pro pack, you really need to take that step and put the lines back to the center. I was told a statistic (don't know the accuracy) that if you don't take that step, you should plan on a 1 in 200 line over malfunction.


atsaubrey  (A 44961)

Sep 14, 2004, 9:24 PM
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Re: [tspillers] Sigma Tandem Mains [In reply to] Can't Post

Im curious about the flat pack claim of less malfunctions. I flat pack my XX canopy, but after looking at it all, it appears that there would be a better chance of a lineover using this method. Am I just stupid?


tspillers  (D 21601)

Sep 14, 2004, 9:54 PM
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Re: [atsaubrey] Sigma Tandem Mains [In reply to] Can't Post

The flat pack on tandems will give you less of a chance for a lineover because you better control the lines. Specifically, when you lay a tandem main down, the D lines fall to the outside of the pack. With smaller canopies it becomes less of an issue because the lines are shorter (distance from slider stop to canopy attachment) and the canopy is smaller so it is easier to control on sport mains. So for those who pro pack tandems, you should be taking steps to put those lines back into the center of the canopy before S-folding. RWS has always recommended a flat pack for a more reliable (less malfunctions) opening.

Does that make sense. It is easier to show than explain.


bclark  (D 22626)

Sep 17, 2004, 5:29 PM
Post #9 of 14 (1480 views)
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Re: [tspillers] Sigma Tandem Mains [In reply to] Can't Post

I saw a rash of malfunctions on Sigma mains this year, 5 in a month. All tension knots, all Pro Packed. I agree that flat packing is a more reliable method of packing, but why is it that we can pro pack our Icarus 365's all day long without all these problems?


Premier slotperfect  (D 13014)

Sep 17, 2004, 7:16 PM
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Re: [bclark] Sigma Tandem Mains [In reply to] Can't Post

Quote:
All tension knots

Making sure that your packers are taking the twists out of the brakelines often will help prevent tension knots involving the upper control lines.

If I am packing a tandem rig myself, I do it on every jump. Cool

I take them out of my own canopy about every 10 jumps.


tspillers  (D 21601)

Sep 17, 2004, 8:19 PM
Post #11 of 14 (1466 views)
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Re: [bclark] Sigma Tandem Mains [In reply to] Can't Post

There are so many factors that can come into play. I believe though that one of them has to do with the lines. The Dacron used on Sigmas are better for openings (stretch with opening shock), but as they wear, they become clingly and attrack one another. This is why it is recommended to replace them around 300 jumps. Many people take them to 500. Some take them until they are way overdue. Of course there are also many factors that can effect the number of jumps you can get out of the lines as well.

Todd


riggerrob  (D 14840)

Sep 19, 2004, 7:02 AM
Post #12 of 14 (1436 views)
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Re: [tspillers] Sigma Tandem Mains [In reply to] Can't Post

In reply to:
There are so many factors that can come into play. I believe though that one of them has to do with the lines. The Dacron used on Sigmas are better for openings (stretch with opening shock), but as they wear, they become clingly and attrack one another. This is why it is recommended to replace them around 300 jumps. Many people take them to 500. Some take them until they are way overdue. Of course there are also many factors that can effect the number of jumps you can get out of the lines as well.

Todd

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

For comparison. Strong Enterprises recommend replacing the Spectra suspension lines on SET-400 canopies every 300 jumps. We have found that if you keep lines for more than 400 jumps, Spectra shrinks out of trim, off-heading openings occur more often and they don't flare very well.


riggerrob  (D 14840)

Sep 19, 2004, 7:10 AM
Post #13 of 14 (1435 views)
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Re: [tspillers] Sigma Tandem Mains [In reply to] Can't Post

In reply to:
The flat pack on tandems will give you less of a chance for a lineover because you better control the lines. Specifically, when you lay a tandem main down, the D lines fall to the outside of the pack. With smaller canopies it becomes less of an issue because the lines are shorter (distance from slider stop to canopy attachment) and the canopy is smaller so it is easier to control on sport mains. So for those who pro pack tandems, you should be taking steps to put those lines back into the center of the canopy before S-folding. RWS has always recommended a flat pack for a more reliable (less malfunctions) opening.

Does that make sense. It is easier to show than

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>.

After suffering a couple of line-overs on my sport main, I modified my packing technique. After flaking the bottom skin, I collect all the steering lines and most of the D-lines in the center of the pack job. Then I pinch those lines in the center seam as I wrap the tail around the canopy and roll it. I keep that grip on the steering lines until the canopy is laying on the floor. The I kneel on either side of the steering lines to prevent them from wandering while I squeeze air out of the canopy.

he end, I achieve the same result as you, the difference is that I keep such a firm grip on the steering lines, that they can never wander from the center line.


tspillers  (D 21601)

Sep 19, 2004, 4:51 PM
Post #14 of 14 (1420 views)
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Re: [riggerrob] Sigma Tandem Mains [In reply to] Can't Post

Makes sense...Have you tried it on a tandem? I may have to try it. We had a ride this weekend I believe due to the lines. We didn't have accurate records when we started with this rig, but I estimate we have close to 400 jumps on those lines. We will know in the future as we now track every time a specific tandem is used or items replaced.

Todd



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