dorbie

In either case the guy is looking up at his main with his head way back over his reserve tray when he chops so the freebag goes bouncing over his shoulder past his head. Great for video, maybe not so good for deployment, and another note to self about chopping.

Why did you ride it up above 4k once your realized? They'd have made it up faster after you got out. This seems like one of those situations where you need to overcome your inhibition to take action and exercise the safe option.

I've said that bag locks are caused by more than just double wraps (or similar) in about 5 posts, you must have missed that (although I had other failures in mind and mentioned it in several posts). I did read your posts on the geometry of the stows etc, and never entirely discounted it but I disagree with your final conclusions. Breaking strength is critical. This has become to and fro advocacy on an issue of judgement so I don't think we'll come to an agreement.

Seriously? And why have they added these two modifications then? It doesn't make much sense to deny contributing factors in an incident.

So you agree they have a lower break force. Bag locks are caused by more than just double wraps. Dismissing the threshold or likelihood of an event ignores a key part of the risk.

So anyone who doesn't agree with you and the points you make is smelly?? Stay with the facts, the PAs just indicate that even you think you are losing the argument. That wasn't a PA, not even close. Nice attempt at a distraction.

I was gonna ask about that, I think my slider has smaller grommets :-).

You're still ignoring DSE's incident. His packer packs all day long with no problems putting double wraps on bands then he does it to tube stows and it locks. But according to your assumptions they should just break, realize there are the same number of connections to the D-bag on a double wrapped stow and a single one, so one might conclude according to your earlier math it should just have broken. Now if that locks so readily (and you know it does because you and other advocates have told everyone not to double wrap tube stows), there are a few other scenarios that can cause a lock that have nothing to do with double wraps. Citing a precautionary safety advisory on select student gear about double wrapping bands does not equate to the well known risk associated with double wrapping tubes, our everyday experience as skydivers makes that clear. DSE's bag lock was caused by tube stows and the advice given to avoid that obviously and trivially undermines other claims made for tube stows. Something stinks here and it's due to the advocacy of a piece of gear some are determined to use. P.S. you don't get to isolate every mal involving tubes and say it wasn't the tube it was the packer, or it wasn't the tube it was the grommet. These things are intrinsically linked, taking every tube baglock and saying it could have been avoided if something else had been done right is a seriously flawed way of evaluating their safety.

And this is the point I keep bringing up whenever this debate comes up. I harbor no illusions that a carbon fiber 'cool' helmet is as safe as a Pro-tec...but by the same token, it's tough to confidently say that it isn't. Actually it's pretty easy to say that in most cases. There's no doubt from anyone who knows the physics of impacts, that a protec is better than most, however exactly what you're protecting against is critical if comparing two good helmets not a helmet and a skydiving 'hat'. Most skydiving 'hats' don't come close to a protec on any impact criteria. However if you want to get serious about testing there are real design tradeoffs to be made for keeping a jumper conscious after a moderate impact vs. keeping a jumper alive after a hard impact. These are not entirely compatible objectives, however most skydiving 'hats' don't come close to a protec helmet.

I dropped my altimaster and it started screwing up on jumps. I reset the alti and jumped it several times just to be sure and yep it was definitely screwed up. Altimeter's sometimes break even ones you trust, I'm not so sure there's much value in gear snobbery when it comes to Suunto, but I haven't checked it, skydiving involves rapid changes and some extreme conditions that might be a factor. P.S. my broken altimaster was reading about 1k higher on the ground after being reset each jump, which is a pretty undesirable feature in an alti.

I think you're fortunate the ground was soft. While you were gouging that hole in the earth your head and brain were decelerating, so because your helmet was able to travel INTO the soft earth an inch or two the forces stopping your head were spread significantly over time reducing the peak impact force. Had it been a harder surface the outcome may have been very different. It's good that the helmet offered some protection but a critical factor in an impact like this is the forces imparted on your head and therefore the helmet lining is at least as important as the shell. If you want to learn another useful lesson from this go and measure the depth of that divot your head made and compare that compression zone to the thikness of the lining on the next helmet you purchase.

It's not the strongest indictment, but it's part of a chain of events. No single factor would have led to the fatality, break the chain and you prevent the undesirable outcome. The investigator listed it as a factor. Her bag came out, and it highlights that the momentum of the bag and drag has the potential to reach line stretch with the correctly rigged stows even if your pilot chute is not correctly rigged, there's even video of a successful deployment with this error (after getting the bag out). It's not just about the force imparted by a correctly cocked and functioning pilot chute, these are not black & white systems, all sorts of crap might happen or go wrong that you'd preffer to survive. However there are other instances of bag locks due to the stows on otherwise good gear, you don't have to rest the case on that single incident, but we're retreading the same ground, there's no utility in repeating it.

DSE posted info on a bag lock directly attributable to tube stows to this thread, if you can selectively ignore that you can dismiss anything that hints at causality. The advice given on what not to do with tube stows in order to be safe is enlightening and makes a mockery of some claims made for them and you cannot address the line trapping issue with band geometry. Despite attempts to poison the well Sherman is not just a designer of rigs, but you can read his bio. He presents arguments that aren't merely an appeal to authority that are more compelling than line wear. One major reason jumpers have advocated tube stows on mains is that they do not break as often as rubber bands and are therefore more convenient. I have never even mentioned price, you've responded to a valid point with a straw man, but the nadir of your fallacies is the claim that in every band bag lock you've seen the band did not break. Tubes certainly break less readily than bands and are used because of this, dismissing the problem with this ignores the central issue. When mains are packed as carefully & expertly as reserves and deploy as predictably there might be stronger analogies to be drawn, buying all those freebags will be a lot less convenient than replacing bands though.

Yea if you say so. Perhaps he should have a chat with the guy who's designed containers and deployment systems to use mil-spec bands for 30 years and says "bands break for a reason, I designed it that way, use them". Nobody is impeding your beliefs or ability to jump. You're on a public forum offering advice that runs against the best expert advice out there, ignores a pretty obvious self-evident issue with non breaking stows and uses very selective anecdotes to claim the risks are equivalent. That's not about just your belief or right to jump whatever you want. You can recommend stows for their convenience all day long I really don't give a shit. I'd even agree with you, yep they're convenient, they don't break.

Yea, what does that John Sherman guy know anyway. Just go with the convenience factor and selective anecdotes. http://www.jumpshack.com/john.htm

I think you are trying to make a correlation where there isn't one. If someone packs their sport rig using tandem rubber bands they are bound to encounter problems eventually. Likewise if someone packs their sport rig with tandem sized tube stoes they're bound to run into problems eventually. The incident report indicates the problem had nothing to do with whether her stoes were rubber bands or tube stoes and more to do with using the right size. If your locking stoes are way too big (like tandem rubber bands or stoes) some of the canopy fabric can come out before getting to the locking stoes which can create a baglock by wedging the stoe and lines. I've seen this once. In fact, in that case, it appeared that if the person had been using tube stoes, the baglock wouldn't have happened. I don't have a picture of that particular one, but Videofly on here should still have it. I agree, there's no direct correlation with this incident. I'm still persuaded by the bands tendency to break when you have a line trapped in a loop and human factors in packing. maybe you would like to withdraw your statement!? No thanks, I don't want to add to or subtract from anything I've said there. You tried to bury the relevant portion of this incident by jumping to the final vague gear maintenence conclusion when the incident very clearly has relevance to the issue of choice of stows and can help inform a decision to go with stows that don't break in my opinion. There are also numerous bag locks directly attributed to tube stows on otherwise well maintained gear and you have never addressed lines trapped in the excess line loops, not double wrapping misses the point. Rubber bands break for a reason, or to word it more appropriately, they are used for a reason, and part of that reason is they break. They're not infallible but they are better than tube stows. There's a propensity for people to rationalize gear decisions with contrived arguments, I think this is happening in the 'debate' over tube stows. They are convenient, cool and less frustrating for some, but they have an unquantifiable added risk. It doesn't matter how much you want them to be safer or as safe as bands, they aren't and the evidence & risk is not swayed by your preference, only your decision is. Personally I'd quite like it if tube stows were as safe as bands, it's a shame they aren't. Pretending otherwise is just kidding yourself. This is not a new debate, I like the historical perspective this guy brings to the table: http://www.totalcontrol.com.au/services-select.asp?iServicesID=11 Skip to the last paragraph if you like, but read it and accept it. By all means jump whatever you like, but don't sell rationalizations that deny the added risk. Tube stows don't have to be as safe as bands and you can still jump them all day long if you like.

I think you are trying to make a correlation where there isn't one. If someone packs their sport rig using tandem rubber bands they are bound to encounter problems eventually. Likewise if someone packs their sport rig with tandem sized tube stoes they're bound to run into problems eventually. The incident report indicates the problem had nothing to do with whether her stoes were rubber bands or tube stoes and more to do with using the right size. If your locking stoes are way too big (like tandem rubber bands or stoes) some of the canopy fabric can come out before getting to the locking stoes which can create a baglock by wedging the stoe and lines. I've seen this once. In fact, in that case, it appeared that if the person had been using tube stoes, the baglock wouldn't have happened. I don't have a picture of that particular one, but Videofly on here should still have it. I agree, there's no direct correlation with this incident. I'm still persuaded by the bands tendency to break when you have a line trapped in a loop and human factors in packing.

If you think there's no lesson for tube stows in a fatality where a stow band being too large formed a key link in the incident chain then there is something wrong with the way you are thinking about this problem. P.S. Sorry, I think I better understand your confusion. I don't think "too large" means loose in this case.

Sorry if it appeared that I was claiming they would under all circumstances, it's not really my point. My point is a rubber band has a much greater chance of breaking before a tube stow will in scenarios where you need it to, and this is a factor in using rubber bands for stows. Comparing two options and saying they can both baglock ignores the most critical aspect of choosing the safer option. These systems do not have the same chance of failure.

That is incorrect. We jump complex & redundant systems, almost all incidents are the result of a chain of events. Here's is the relevant quote from the fatality report: "The main parachute could not escape from its deployment bag because some suspension line stowage bands were too large to allow the bag to open under the reduced pilot chute drag conditions" Perhaps you never read that part and wish to withdraw your statement.

A statistical sample of one careful jumper does not inform anyone about the risk from their use.

Where did you get that from? Read the MIL spec and there is nothing in it about breaking intentionally. I thought about rewording this when I wrote it to avoid this semantic issue since it was not just about the design of the band itself but it did not seem significant at the time. However to answer your question; FJC and discussions with experienced jumpers & riggers, and it's self evidently they do, they certainly have a propensity to break before a stronger stow will. Of course if you're arguing that they won't go for it. But make the claim or there's really no point of substance to be disputed.

I wonder if Claire Barnes was given similar advice. It's a safe bet she never realized it would be a link in the chain of events that would kill her.

Here is a scenario that fits the bill; this incident should be enough to make it clear that tube stows are not the best idea: http://www.dropzone.com/fatalities/Detailed/12.shtml Students off FJC can recognize tube stows as a risk. It's not just about double wrapping them, for example, rubber bands are designed to break in situations where lines get trapped in the excess loop. Jump what you like, but understand there's method to the minor inconvenience of correctly sized rubber bands.

Are you planning to attack your canopy or fly it?