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I already had a discussion with one other individual about this, and the jump you're talkin' about was a slider up pack job (into a headwind, no less)...a totally different story altogether. I said that yes, I did see the oscillation, but did not see any heading problems caused by p/c oscillation alone. All of the slider down jumps were on...Slider up pack jobs with deployments at low air speed are notorious for off-headings, and therefore should be avoided on short delays with object strike potential. I don't see how a vented pilot chute would have changed the outcome of any of those jumps, and personally, I haven't been all that thrilled with what little vented p/c action I've seen. As all the big boys say: this is only my opinion, and I am no authority on any of this...
Oh, and don't try this stuff at home...it's dangerous

I am interested in peoples view on this. My PC's have non load tapes and are non AV. The people who make these PC's have a valid argument for the reasonings for this. The people I speak to about the negative side also have valid points. I see both sides and my feelings do lead me to believe that load taped and AV do help stop oscilation in some situations - (higher air speed) . I know of several jumps I have had with with Off Heading are caused by the PC oscilation (review of video) . Maily this is caused by the way I have thrown my PC on some jumps (I no longer throw this way!!) . Others where I "place" my PC I have had no problem with OH (other factors have effected this ). As has been mentioned on LOW jumps (as most of mine are ) is there a real advantage of load taped AV PC's? I would like some views to either comfirm my thoughts, cancel my thoughts or open my eyes to other areas!

My opinion (that is worth $hit) is that the way the PC is thrown and folded has more effect on the way it acts.

Be safe........... be a newbie thinking about things and wanting opinions..........

would also be interested in views on this - taking a 5 or 6 second slider up - as object allows - would you rather go 3 or 4 slider off because of off heading potential??? - do you regard the slider up deployment between 4 to 8 as a hazzard for off headings with certain wind speeds?

be safe........... be thinking of my views on an open forum!

I'm feeling reasonably current on this topic, as in the last 8 days I've made almost 25 slider up jumps with delays between 4-7 seconds, and watched several hundred more.

In a nutshell, there is absolutely a higher incidence of off headings with slider up deployments in this delay range. How much? I am not able to quantify, but I think it is increasing in a non-linear way as one takes delays lower than 7 seconds or so. By 3 seconds, the odds are getting pretty bad. Even going up from 3 to 5 is a big improvement in off heading potential, in my book.

While it is tempting to say that the solution to this issue is to just pull the slider down and take 3.5, there are other considerations. With a good exit and some solid tracking skills, one can gain MUCH more separation after 5 seconds slider up than after 3.5 seconds slider down. A good exit and a good track can put a jumper far enough away after 5 seconds to handle a full 180 no problem - given proper brake settings, proper response procedures, and not a massive line twist issue.

In general, I believe that the largest factor by far in off-heading causation is body position. For example, we had very few 180s while jumping Petronas this week - about 600 jumps, maybe 10 or so 180s. Exits were all flat and stable, due to the risk of object strike on that building.

Moving over to KL Tower, with less object strike risk, we went into aerials. In several hundred jumps, I saw dozens and dozens of 180s - many with line twists. Of course, this is because we were often deploying in wildly unstable positions - head down, on our sides, on our backs, rotating, etc. No amount of careful packing is going to make up for a flailing deployment - whether one is doing aerials on purpose or just because one has bad exit skills.


Peace,

D-d0g
ddog@wrinko.com
www.wrinko.com

I've separated this discussion from the NC BASE video thread, as it appears to be developing into a technical discussion more appropriately held on it's own.

Can you summarize that argument for us?


Be careful developing this habit if you intend to fly wingsuits. It could be a potentially fatal error in that environment.


My opinion is that the reduction in PC deformation makes the load tapes worthwhile. The tapes may create some weighting on the topskin, and thereby slow inflation. However, I do not believe this will become important until you are well under 200' (exit altitude). A deformed PC, on the other hand, will have negative effects at any altitude or airspeed (sometimes greater than others).


There was a large amount of PC data collected at the Petronas jumps, which is supposed to be collated and shared (right, BR? we're going to hold you to the sharing part). This ought to give us some good insight into the value of apex vents.

That said, I believe apex vents are a step in the right direction, but only a step. When viewed in profile, an inflated PC has a shape resembling a heart. The apex of the PC (and any apex vents) is actually in a lower pressure area of the inflated shape (the inverted 'V' at the top of the 'heart'). A more efficient vent (which ought to be a more efficient oscillation damper) could be placed at the topmost curve of the 'wings' of the 'heart', in the point of maximum inflated pressure. Viewed on a flattened PC, these vents would be approximately halfway from the apex to the skirt, arranged in a circular pattern (but probably not occupying the entire circumference, because that would result in over-venting and loss of snatch force). While such PC's have been built and some preliminary testing done, they are a long way from field use.

In my opinion, by far the most prevalent cause of PC orbiting is asymmetric attachment. Given a choice between an asymmetrically attached and vented PC, and a properly attached and unvented one, I will opt for symmetric attachment every time. It is also possible to manufacture a PC in such a way as to render asymmetric attachment impossible (Paratech rigging does this), but most manufacturers have opted not to do this for cost reasons.

See also PC Logic, Off-Heading Openings, and Off Heading at Opening in the BLiNC Technical Archives.

First: I've had great success on pretty much all my mesh slider up jumps, with delays ranging from 2 seconds to 14 seconds, with maybe one serious off-heading every 50 jumps. The others are all on-heading within 45 degrees. Most are within 15 degrees of on-heading according to observers. This has been achieved on maybe 9 different canopies of various sizes, manufactures, BASE specific, non-BASE specific canopies.

Issues: Freepack, pilot chute stowing.

Freepack: stage the opening as much as possible.
Fold stabilizers. Light roll on outer cells. Do not heavily expose the center cell. Be very careful on the tail flaking. Minimize the use of direct slider control. Consider factory side pack for shorter delays. Much success has been observed with this pack job on 3 to 5 second delays, first illuminated by BASE 74 (Richie S.). All of these factors have detailed reasons for the techniques. I prefer mesh slider up even on shorter delays even next to a solid object because of the extra response time and the minimal pendulum effect associated with a 180, with can be deadly on slider down next to a solid wall.

Pilot chute staging: This can be critical to on heading performance. Experiment. The ideal is between the mushroom pack and the burrito pack.

Too much to explain...

OK, but can you explain just this part:


What is a factory side pack?

Hi Tom.

OK. The factory side pack was basically the original pack job on ram air canopies. Check out any reserve guide from years ago. I've found they open faster, and this seems to be the concensus among many old timers (BASE #'s < 250). Much of their knowledge has been lost over the years, to the detriment of the jumpers of today. Its a basic stack pack, similar to what Dennis McGlynn advocates. However, to dial in this type of pack job, you must do some very specific things with the stabilizers and tail and are impossible to illustrate except in person. The pack job opens quicker than a propack simply because it has less folds. However, the disadvantage is that the pack job is prone to fall apart more during line stretch than a tighter-bound pro pack. Remember, the freepack is a completely different beast than a sleeved or bagged canopy and precautions must be taken to minimize torques on the canopy prior to inflation. The disclaimer is that there may always be exceptions to these general rules however. To see the difference in opening characteristics between the pro pack and the factory side pack, check out the Discovery Channel BASE program done by Tom Sanders circa 1992. Some of the same footage is in Tom's video "Over the Edge." Check out the building footage. Moe wears a red jump suit and a belly-mount camera and jumps his newly designed flat pro pack. And then Richie (BASE 74) jumps, wearing a yellow jump suit, (a JD Walker (BASE 37) BASE rig, which is a rig I still have), and his factory side pack. There is a noticable difference in the opening quality. Funny, Richie is jumping a Unit canopy, which has 2 bridle attachment points.

Which takes me to another point, it seems like a lot of the gear improvements of today are variations on experiments done in skydiving years ago. For example, the Stratocloud that my friend BASE 175 jumps, designed circa 1980, has bottom skin inlets and multiple attachment points. He had not a single opening on it more than 45 degrees off-heading in over 100 jumps on that canopy. I'm rambling... Also interesting is that he packed his canopy pre-tailgate and did not have any line-overs even over a history of 150 slider down jumps. Old knowledge is still useful.


The flat pro pack was first demonstrated I believe by Moe Villetto.

I have a couple issues with these statements.

Firstly, from what I've seen, a good (ideally) horizontal launch with no attempted track will give you better separation than a medium launch and attempting to track, for delays <5 seconds. A good launch can give you a horizontal separation rate of ~15 feet/second. Do the math. This is the reason Mark Hewitt (BASE 46), for example, will not jump buildings low enough that he cannot take a 3 second delay on, simply out of object strike potential. Frequently it's better to take it low with clearance than to open high with little clearance. That will keep you alive.

Secondly, body position is critical until the completion of the opening. You must stay relaxed and not look up during the inflation stages. If you are tense, any asymmetries are exaggerated. I've been recommending this to my friends who jump very highly loaded ellipticals and now they have nothing but on-heading openings. Before, off-headings were the norm and cutaways were frequent. You must stay relaxed and not move you arms up too soon and interfere with the risers in any way. Stay relaxed until you feel like you are in the saddle and then go at max speed getting an orientation, risers, toggles, etc.

>While it is tempting to say that the solution to this >issue is to just pull the slider down and take 3.5, >there are other considerations. With a good exit >and some solid tracking skills, one can gain MUCH >more separation after 5 seconds slider up than >after 3.5 seconds slider down. A good exit and a >good track can put a jumper far enough away after >5 seconds to handle a full 180 no problem - given >proper brake settings, proper response procedures, >and not a massive line twist issue.

Hey 460,

Email me at ted_biggs@yahoo.com when you get a chance.

Better yet, check your private messages here. I'll be sending you one shortly.

I agree with you completely on this. Particularly below five seconds delay, very few jumpers are able to make an effective transition to track that increases horizontal separation. Even those that can do not have 100% consistency.

Far better to launch hard with no track, than it is to focus less on the launch, miss the track transition, and end up pitching head-down and closer to the object.


Again, I agree with you 100% on this.

Peace,

D-d0g
ddog@wrinko.com
www.wrinko.com

dude, if you dial in the pack job you mesh slider up will open on heading with a rate that will allow to correct quickly. slider down 180's are harder to deal with because you experience a pendulum effect from you forward launch coupled with you canopy flying backwards, potentially with a half line twist. off-headings are not an issue if you know what you are doing. we're not frigging relying totally on the russian roullette aspect of the opening to survive. i've had full 180's from sub-300 objects with full corrections based on awareness of body position and how the canopy will open based on these body positions. think, think, think... CRW, particularly accidental CRW is the guide. Are the jumpers of today so unskilled they must rely totally on the luck of the draw of the gear they do not understand totally rather than learn the simpler skills of how to deal with the rapid emergencies of dealing with a crappy openings.

I hear what you are saying, but based on my limited experience (200 BASE jumps from 50+ objects), I respectfully disagree.

I have corrected full 180s both slider up and slider down - well slider down was actually more like 150 rightie, but with a buttress on the right. From those experiences, I would not be willing to say that I felt I could correct "faster" slider up than slider down. Additionally, I have found a higher incidence if line twists with sub-terminal slider up jumping than slider down, and it is off-headings plus line twists that really scare me most - slider or not.

For me, there are some jumps that are clearly slider up (over 600 feet or so rock drop, in general), some that are clearly slider down (sub-250 foot freefall or sub-200 foot static line/PCA), and then a "no-man's land" in the middle where much object strike risk resides. While you may have a super system for jumping with minimized risk in the no-mans's land, I believe I may have one also. In other words, different jumpers may develop different techniques (and corresponding different gear configurations) for this area of BASE with neither one nor the other being intrinsically "better," or at least not quantifiably proven to be be better on general, for all jumpers.

Too, there are some jumps where the Russian roulette element is really there in regards to off-heading issues. A good example of this is a static line exit in southern France, ALS altitude about 13,000 feet. With this exit, any rightie more than 45 degress, I believe, would be catastrophic no matter what (current) technology, jumper response, etc. Perhaps someone, somewhere has a gear config and the traning and natural ability (and hand/body speed) to respond to a 90 right from that exit and not have object strike. I've never met that person, nor seen that gear. Thus, jumping that exit (even PCA/static line) simply is a roll of the dice. Whether the chance is 1% of the rightie, or 30%, so long as it is significantly greater than 0% then a jumper doing that jump with the current generation of BASE gear is rolling the dice.

As a technical point, one need not (by definition) experience more "pendulum effect" slider down than slider up. That depends on the launch, and it is possible to soft launch slider down as it is slider up. True, a hard launch slider down from 400 feet might create more opening pendulum than the same launch slider up with the same delay, but in that case it is possible to jump with less push slider down, take a longer delay (since the opening sequence burns less altitude), get exactly the same separation on pressurization of canopy, and not get more systemic pendulum.

At the extreme, it is possible to generate effectively zero pendulum with a straight drop PCA exit from a S; it is also possible to exit hard from a PCA and generate lots of pendulum - but there are exits where the latter may be much safer than the former (trying to clear a ledge at 100 feet, for instance).

BASE, in my experience, militates often against "right" and "wrong" answers in many areas of consideration. There is black and white in BASE now - a set of things on which most jumpers generally agree, and the data support them - and then there are grey areas where either the data simply aren't there, or there are roughly equally valid approaches that come at a problem from different angles. Finally, there are alot of "it depends" zones, such as whether it is "better" to put a slider on for a 600 foot cliff jump or not. Well, that depends. . .

I know jumpers that are very competent at correcting slider-up off-headings during deployment sequence; I've even got video of that from last week's Malaysia jumping. However, I'm not sure that makes me willing to say that slider up is this always safer for jumping for someone who has that skill at the level that I've seen it. In fact, the jumper most capable of those sorts of corrections is also the one I know who is most leery of sub-terminal slider up jumping and the resultant off-heading issues therefrom.

There are interesting questions; I appreciate your dialogue and opinions on them very much - thanks.

Peace,

D-d0g
ddog@wrinko.com
www.wrinko.com

I may be reading your post incorrectly but I am not saying "hey I dont have the skills to deal with a 180" I was merely asking the about the increased probabilities to off headings from various factors - including the 4-7 delay.



This is what I was asking about.


Be Safe............

This is the great thing about BASE and it always goes into my instruction: Expose a person to as many ideas that are potentially well thought out and let a person make up their own mind as to what makes sense to them. There is no single authority on the art of the base technique and a person has to rely totally on themselves when putting their lives in their hands.

My only feeling is that based on wall strikes (a few pretty bad) i've seen, that slider down opened a little faster than the jumper could reliably respond too quickly. And mesh slider up just gives me a little more time in case of a 180, even though a off-heading is more likely. This is just knowledge I picked up from old timers who jumped old crappy gear and were top members of the 180 club. The truth is out there and it's good this forum is provocing a civilized technical discussion.

Was this data ever made public by BR?

I haven't seen it.