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When I was taught how to pack rounds for BASE jumps back in the day one strongly-emphasized point was that unlike squares, when jumping a round the lines are best stowed in the container pack tray. I don't recall the reason given but I always stowed my lines in the pack tray and it worked well, though I never understood the reasoning.

Recently I was in a discussion on packing rounds for BASE jumps and I repeated what I had been taught and said I never understood the reasoning.

So today I talked with a long-time friend who is a master rigger and he said he had heard the same thing and it was bullshit.

He considers diapers with side-to-side line stowage to be the way to go (much like squares) and his reasoning is that in the scenario of an unstable deployment, the lines are pulled away from the jumper so there is a reduced entanglement hazard.

I agree and the only reason I can think of to not use a diaper on a round (although I never used one on any of my round BASE jumps) is purely psychological. Doing anything that chokes off airflow to a deploying canopy is scary and when it is a kind of canopy that is rarely jumped, seems that much scarier. I do not see any real issue, though.

Thoughts?

Walt

If you use a traditional diaper set-up it will probably slow the opening a bit because the diaper closes off the air channel until you reach line stretch.

If you tried to place the lines on the round canopy (as opposed to in the pack tray) with some sort of line stow (or pocket, which would probably work better) system without closing the air channel, you would create an asymmetric load along the skirt (where the line pocket was riding).

I can intuitively see how such a weight might contribute to an inversion (in much the same way we see tail inversions on square canopies with tail pockets and no rear multi-bridle attachment point). As the canopy began to expand while traveling to line stretch, the weight of the lines would push downward between the lines themselves and potentially start an inversion along the skirt.

On a square canopy, this tail inversion (induced by the weight of the lines) virtually always clears itself immediately during the inflation process. I would worry that with a round, it might lead to a larger malfunction, since skirt inversion is a well documented malfunction on a round canopy (particularly on undiapered round canopies).

Potential solutions to this problem might include spreading the weight of the lines around the skirt by creating several line pockets for different sets of gores, individual stowage of each line, or moving of the line pocket/stows further up the canopy away from the skirt. In any of those cases, though, it seems to me that the solution would add substantial complexity to the system (and the pack job).


> He considers diapers with side-to-side line stowage to be the way to go (much like squares) and his reasoning is that in the scenario of an unstable deployment, the lines are pulled away from the jumper so there is a reduced entanglement hazard.

While I can understand the argument, I am not certain that fixing a problem that hasn't manifested itself in the real world is worth potentially creating other problems, either by increasing the rate of inversion related malfunctions or by increasing the complexity of the gear and pack job.


In other words, it doesn't, so far, appear to be broke and I'd be concerned that fixing it might actually break it.

If your reasoning is correct, then stowing the lines in the pack tray is more or less a consequence of the desire to not 45 the skirt or otherwise cutoff the air channel by using a diaper.

Makes sense.


Walt

Personally, I just stack the lines in the container with pony tail rubberbands used to make line bites and to segregate the lines. I use one locking stow. Seems superior to using a diaper since the amount of force to unstow all the lines is much lower while still being able to sequence the opening.

I've often used rubber bands and just set them in the bottom of the pack tray.

I've also just free stowed the lines in the bottom of the pack tray.

I was wondering the other day if I should just try sewing a tail pocket (or similar pocket) into the bottom of the pack tray and using that.

I've seen some rounds with nose pockets (basically tail pockets instead of diapers).

I wonder if the best solution would be to use a nose pocket with a single locking stow (just as we do for squares)? In theory that should keep the lines together (inhibiting inversion) while also putting the lines up on the canopy. I'd still be curious what the weight of the lines would do to the deployment.

That's what I do (or used to do) also. Worked well.

Walt

a few of us jumped rounds recently and one was stowed in a diaper, one was pony tailed stowed in pack tray and one was stowed in the bands of the diaper, but not closed (set up more like a nose pocket, but stows instead of a pocket). all three opened similarly, but the diaper and nose stows appeared to have a little more snivel than the freestows in the pack tray.

A tailpocket in the pack tray is an interesting idea. As an aside, one thing I saw Space doing years ago that I thought was kind of cool was a sort of intermediate approach between a tailpocket with no line stows (other than the locking stow) and one with a full set of rubberband stows. He made some spandex tailpockets. Doesn't seem as durable, but it would hold the lines in place nicely.

I have seen the nose pocket used without any problems and I think it was a converted diaper. The single stow would avoid the issue of the skirt being unevenly loaded, but if only one locking stow is to be used and the skirt is not 45ed or closed off by a diaper, 460's method of just using a solid locking stow with no pocket or diaper would seem to be the way to go because it does the same thing with zero uneven loading on the skirt.

I am curious about the effect of the loading also. I know partial inversions can happen on rounds, and it's obvious what has to happen for a partial inversion to occur, but I have always had a hard time visualizing it.

For a partial inversion to occur, it seems like the riser tension would have to be dramatically uneven *and* there would need to be a significant lateral force on the looser side driving it downward and toward the tighter side *and* then, with perfect timing, the looser side would have to blow between a pair of the tight side's lines, block inside and outside airflow on the tighter side and the looser side would need to start inflating very quickly. It just does not seem to be anything but an extremely remote possibility but it's well-documented that it happens.

Very slow motion close up video of the partial inversion scenario would be awesome to watch.

Walt

 
As to the weight of the lines on a diaper. It's not a trivial amount of force. There is a good bit of mass there and it's a noticable jerk when you try to accelerate it. Most of my experiance with this is in the high speed range where it becomes very important. The weight of the lines pulls on one side and an apex line over the top can act like a line running over a pully. It can shift the apex dropping below the rest of the canopy and pulling up on the oposit gores on eather side of that line. Remember the Phantom that blew up at the airshow? The force can even be enough to damage the canopy. I've had it break the tape on the radial seam on canopies I have built. Now a days I make a point of useing a heavier tape on that seam.

You'll never be going fast enough to tear the canopy in half there on a base jump but you could shift the apex and make the canopy uneven. There are easy ways to fix this. First if you're building a canopy a heavier tape there that exends up to the top of the apex and forms a loop to carry the load is a good idea. Think C-9 in a Quarter bag. They did that shit for a reason. Another simple solution is to just add a loop and attach it to the tape on that seam. FFE finger traps an eye in the center of the apex line from the diaper to keep it from shifting. In fact the do two of them at 90 deg to each other. One thing I love about PDA is crown lines. I don't know why people don't make PDA's as a base jumping canopy. I've got a K-22 that I converted that works great. It's bias and the gore shape isn't too far off. Reduices the fill volume, spreads out the load, slows the decent, and moves the apex hole down where it's less of an issue on the speed of the opening. The K-22 has a rather large apex hole.

Lee

Weight of stowed lines causing sag enabled by crown lines makes perfect sense. I had never thought of that. Thanks for the explanation.

I don't remember a Phantom blowing up at an airshow but I do remember the AD requiring kevlar bands. Is that what prompted the AD?

Just guessing here, but regarding PDAs (pulled-down apexes) there is probably the association with Paracommanders, which were considered to have a much higher malfunction rate than reserves.

Assuming an open canopy, of course a canopy with a pulled-down apex will have a slower decent rate and faster forward speed. Is there any inherent reliability issue with the PDA, though?

Walt

Even with a shorter delay my opening sucked.

pussy

The K-20 is probably the best BASE round I've used, with the possible exception of the Tektite (which is virtually impossible to find these days).

Your mom!

out of interest, what are these K-20 and K-22 canopies ?

Old round parachutes.

Mine was made by Pioneer Aerospace quite some time ago. Pioneer stopped making civilian gear a long time ago. At this point they pretty much only make military equipment for government contracts.

I have no idea if the design is in production anywhere at this point.

Surfing around the Pioneer website, I see that they are part of a larger group that includes Parachutes de France, so I wonder if PdF could get K-20's for civilian use?

Back in the day when skydivers had round reserves there was a generation of rounds that was designed to be as low-volume and lightweight as they could make them, yet still strong enough for a terminal deployment.

For many years the standard round reserve was the 26 ft. diameter Lopo (low-porosity) canopy. The newer reserves, like the K-XX packed a *lot* smaller. As I recall, they came in three sizes--20 ft., 22-ft., and 26 ft. (Phantom was another low pack volume reserve with similar sizes)

A unique feature they had was the "cats eye" apex vent. Two overlapping pieces of fabric allowed air to flow through the vent during inflation but closed off the vent after the canopy was open.

Great BASE water jump canopies for sure.

The acid mesh problem and popularity of square reserves pretty much killed the market for those canopies but there are some still around.

Walt

 
My life alternates between being really bussy and really bord. would there actually be a market for a round water jump canopy? Things like the old k-20's are getting hard to find. If so what would you like to see in it? PDA? Type 2 or dacron lines? I don't see snatch force or opening shock being that big of an issue. How hard of an opening would you be willing to tolerate? How important are terminal opening caricteristics to you? How big would you want it to be? F-111 or lopo? I wonder if LoPo might hold up better to repeated water jumps. Nylon would probable be better then kevlar for a working canopy. More on topic what deployment system would you prefer on your jumps?

I don't know I'm just setting here looking over at one of my double neadles with a lap seam folder and tape foot on it... There's this big fucking roll of F111 in the corner that I have no idea what I'm going to do with... It's red though.

Lee

Lee

No doubt Tom would be the right guy to answer you questions but I can tell you my experience.

I made most of my BASE water jumps with (I think) a 23 ft. Pioneer tri-con. The biggest advantage that the lightweight canopies (like the K-XX) had was that they dried out a *lot* faster, which is a real convenience when making multiple loads in a day. The shorter line length was nice too because it took up less space while drying. Also nice because if the canopy oscillates, the swings are not as far.

I don't think terminal openings are going to be much of a consideration for that type of canopy, but Regarding openings, a nice staged opening is always a good thing.

For deployment we always stowed lines in the container pack tray and it worked well. A locking stow to help give a staged opening is good.

Just some thoughts.

Walt

I tell ya, there are sites where rounds totally rule. Water or a sandy landing.

BITD, everyone had line stows in their packing tray. We even put them in our skydiving rigs.

Rich Stein and I both had Preserve 3's. You could pack them in a bread sack and they would take all the opening shot that you could throw at em.

So we basically just did a super careful flake (you have to have some tension on the apex for it to pack well), and then a couple of narrow folds. Yeah, they had diapers, but no way would we use them.

They open very evenly and predictably. So they were good on say, a 600 foot cliff. You could burn it down further than a slider down jump could handle.

I mean, we REALLY burned it down. One advantage of this is that the things have such rotten forward drive, that if you get open low enough, no way would you hit the object. A guy died on this object(s) that we opened up by having a wall strike with a square.

I won't divulge sites, but there were two really biggies that people still flock to. I would jump a round barefoot if it was soft sand.

I loved them, but for only a few objects. They were just convenient. Pop your reserve, yard that sucker out, hook it up to your BASE rig and you are good to go. Packing them is different, so you need someone to show you how. It is very simple.

We used to put a fat rubber band over the apex to make them open faster. I dunno if it had any effect, but it didn't hurt.

I saw George Roso jump an old Para-Commander that was rotting beneath the riggers table. 600 foot cliff over water.

damn thing worked. The Para-Commander was the hottest of the hot round main back in the day when we were 3 years old. Crazy. Those things were so full of vents and stuff that they looked like a pile of carved up junk.