Reserve tension knots: tandem vs sport reserves

[skydiverek 54]

 

I was wondering why tension knots on the tandem reserves are far more common than on sport (solo) reserves.

I recall reading about approx 10 tandem reserve tension knots cases, and only about one sport reserve tension knot case.

What is the reason for that, considering that (worldwide) there are more sport reserve rides, then tandem reserve rides. Does it have anything to do with the fact that tandem reserves are mostly lined with Dacron, as opposed to sport reserve mostly lined with Microline ?

 

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[Deimian 43]

That would be my guess. Dacron is far more bulky and less slippery than spectra, so I can image it is more prone to tension knots. But is is just speculation on my end.

[skydiverek 54]

Tandem lines are also longer that solo lines. More length = more opportunity to tangle-up, I am guessing.

[gowlerk 1,903]

22 hours ago, skydiverek said:

 

I was wondering why tension knots on the tandem reserves are far more common than on sport (solo) reserves.

I recall reading about approx 10 tandem reserve tension knots cases, and only about one sport reserve tension knot case.

What is the reason for that, considering that (worldwide) there are more sport reserve rides, then tandem reserve rides. Does it have anything to do with the fact that tandem reserves are mostly lined with Dacron, as opposed to sport reserve mostly lined with Microline ?

 

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This entire question rests on a very shaky anecdotal experience of what you recall reading. A better is question would be to ask if incidents reports reflect your assertion.

[RiggerLee 61]

I haven't looked at the numbers but I've seen friction knots on both. And yes that totally anecdotal. Working with larger canopies we do see some interesting things. I think the first question is the quality of the staging of the line deployment. As canopies get bigger and the bulk and mass of the lines gets larger how they are retained becomes more important to a clean deployment. For example we wound up using 80 lb. Break tie for the line shows. This canopy has 15 cells and 7 non cascaded line groups of 1000 lb line. Which basically adds up to a metric shift ton of line. We also tie the line bundle. Actually we do it twice. Once in four bundles then in one big one. Total pain in the ads but if you look at the really high speed footage of the line deployment it makes a big difference. Some times I wonder if tandem canopies are large enough to justify that effort? I think it's border line but as tandems are trending smaller I think the problem will get better not worse. 

 

Lee

[eric.fradet 17]

I know it is common in military forces to use them, but I have a hard time to imagine we would use break cord in tandem line stows !, I would say that it will be more logical for myself to work on a reserve bag capable of a better retaining the stows lines during the snatch force, I am also wondering if the MARD system does not request the more violent extraction of the reserve after cutaway, explaining we have more tension knots on Tandem reserves compare the past

[RiggerLee 61]

To clarify in the example given we are looking at between 1000 to 2000 lb of snatch force depending on fuel burn off acting on a 65 lb bag. That's why the 80 lb. The locking shows are also made of 1 inch tape.

 

I was thinking more of the bundling of the lines. Tieing them with a light cord at about 12 inch intervals before showing. Since we have eight main risers with a short split to 16 we bundle in 4 groups every 24 inches then then the full bundle in between for a tie every 12 inches. On smaller canopies I've seen them do it in right and left then the full bundle. I was wondering if the larger tandem reserves with non cascaded lines would justify the effort. But I think as things trend small it will be unnessisary. 

 

Watching high speed it does make a difference. You can see the bundle deploy. The ties hold through line stretch. The main bundle spreads and you can see the slider splitting the 4 sub bundles as it comes down. Way more orderly then the chaos of a normal deployment. But I have to tell you it sucks. My ass gets sore setting on the floor tieing all those lines.

 

Lee