Round Reserve

[erdnarob 1]

Hello Megatron. Round parachute are not as safe as most of the people think they are at least relatively to a ram air parachute.
Round parachute when they are at line stretch, have their lower lateral band staying narrow. Some air rushes inside and start to inflate the top of the canopy first making the shape looking like an inverted pear. Bernoulli's principle then apply like an airfoil and pressure is higher inside than outside where the curve is then the whole canopy keeps on inflating.
If by any chance some tiny thread get around the lower lateral band there could be no inflation at all since there is almost no pressure to inflate the canopy at that level. Ram air canopies don't have that problem,
Also, in case of hard opening, the apex of a round parachute can bounce back toward the bottom and pass under the lower lateral band and then you have an inverted canopy or a big mess. Ram air canopies well packed have a rate of malfunction way lower than well packed round canopies. I hope what I am writing is clear otherwise see the Poyntr manual at "Round canopy inflation".

Learn from others mistakes, you will never live long enough to make them all.

[pchapman 279]

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Also, in case of hard opening, the apex of a round parachute can bounce back toward the bottom and pass under the lower lateral band and then you have an inverted canopy or a big mess.

I didn't think that happens at all.
It is when inflation starts, that fabric on one side of the skirt happens to get pushed between the lines somewhere else just under the skirt and blows through that opening. Then it catches more air and tries to drag through there. That gives partial inversions or temporary partial inversions, which may involve nylon burning against nylon which isn't good.

I never saw Poynter's round canopy statistics as very useful for the round vs. square debate. While he talks a little about diapers, his stats only applied to diaper-less rounds. (And much of that is even about hand deployed paratroop reserves!) While the data is useful for understanding fundamental round canopy behaviour, it has little relevance to rounds with any sort of staging, like diapers.

I'm still agnostic on the issue, to what degree diapers improve round canopy reliability. It helps a lot, but whether it gets to square canopy reliability, I've never been convinced, and have never seen numbers!

Does anyone have any numbers on diapered round reserve reliability?

A diaper does provide staging until the lines and canopy are tensioned, but still at the moment of diaper release, it seems one can still get an uneven skirt, such as from a shoulder low deployment.

It would be interesting to see USPA incident and accident reports from the 1980s, where one could look at issues with diapered rounds.

[riggerrob 643]

Look at Strong's numbers (from the 1980s) about how much diapers improve reliability.
Then look at Butler's numbers (from the late 1990s) about how much sliders improve reliability.

[riggerrob 643]

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Also, in case of hard opening, the apex of a round parachute can bounce back toward the bottom and pass under the lower lateral band and then you have an inverted canopy or a big mess.

I didn't think that happens at all.

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That rebound phenomenon is more likely to occur at the high-speed edge of the envelope.

Most low-speed (read skydiver speed) malfunctions are blow-under or partial-inversions, when part of the skirt (lower lateral band) blows across and under the other side and starts inflating "outside" on the wrong side of.

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[stratostar 5]

I've seen it happen live, a few of us were watching a guy go in one day,most had turned away aready and just before he was dead like at 200 or 300 ft he got open with a dipered phantom and it was a "wham" type opening and a hell of one at that, you could see clearly the rebound and invert of the canopy, it burned the shit out of it and even blew a few big holes in it and snapped a couple lines, but this guy lived and the dumbass had no clue how close he was to being dead. This was a free fall from 13K to opening of reserve.

you can't pay for kids schoolin' with love of skydiving! ~ Airtwardo

[crustySCSA69 0]

>>Round parachute are not as safe as most of the people think they are at least relatively to a ram air parachute.
..
..
>Ram air canopies well packed have a rate of malfunction way lower than well packed round canopies. I hope what I am writing is clear otherwise see the Poyntr manual at "Round canopy inflation".

untrue ... untrue ... and I don't care what Poynter said.. almost 1000 jumps on a 4-line NavyCony (in a bag) for a MAIN and EVERY opening was exactly the same ... about 1 1/2 seconds from letting go of the pilot chute and NEVER any pain at all... just a soft mush (it was the bag) .... and never a trace of a problem (again, the bag) Poynter compared rounds with diapers (don't work worth a damn) or no deployment device against Squares with all their nice sliders and such ...
.. why the boneheads never went with a free-bagged round reserve is beyond me

and by the way ... you cut the crown out of the Navy Cony (or whatever) because I agree they open from the top, and when you do that, you don't get over-pressure and inversions (total or partial)

.... and if you know what you are doing you can land one on your toes (toes of 1 foot if you have a 26 ' lopo) but you guys should not be allowed to mess around with these exquisitely engineered creatures unless you've had prior experience ... or at least 1000 square jumps ...