Hey there Mr. Smarty Pants, you KNOW that "AMBIENT" is off-limits!! The contest is now 1 free packjob for everyone on the load every time you say that word. Oh wait, that means we'd have to jump your packjobs &-) OK instead, 1 complimentary CP groundcrew!! Yeah baby!! :D
I prefer s/l or pca anytime over d-bag. There is a much greater chance of d-bags not working properly, or being spun around (hence line twists), etc. And it is more hassle packing and transporting them.
A standard s/l will open a bit lower than a d-bag, but you can take steps to minimise this difference.
With d-bag, you are relying on another person. That is one variable I don't like to work with!!!
For objects that are very low, I use s/l. For objects that are "freefallable", I am happy to use pca but still have a large p/c as backup.
I bet there are more horror stories from d-bags than s/l!!!
>However in my experience, the majority static
>lines (or p/c holders) fail when the canopy is
>lifting out of the container. This point is when
>the static line is loaded the most (or the point
>when the p/c holder panics the most because they
>feel the loading and think they will get pulled
>over the edge).
Has anyone actually measured the forces involved here? It seems like it would be interesting to insert a force meter of some sort between the static line and the object, with synchronized video, in order to determine at what point during the deployment the force actually peaks, and what value it reaches. The experiment could be repeated with various body positions. I don't really feel like repeating someone else's work, but if it hasn't been done before then maybe it's worth doing.
Michael
}> PRAISE THE LORD! }> Can I get an Amen from ya Justin? Hope all is as well as can be, and that you're makin' the best of your current "situation". ...stay cool and keep a LOW profile... ...704
>>Okay, does anyone think it is possible to do a 200' b with a static line?
>
>I agree with the consensus above. It should be
>no problem to static line a 200' object.
<<stuff snipped>>
>9) Always have someone check the routing of the
>S/L and bridle before exit. Some people
>actually hold the bridle and or PC loosely in
>one hand (as if PCAing themself). I only do
>this in high wind (to keep the PC deflated),
>though.
<<more snipped>>
>--Tom Aiello
Tom,
Just curious: what is your definition of 'high wind' on a 200' S/L object, in general? What is your definition of 'high wind' on a 200' S/L B. with, perhaps, a moderately sketchy lz?
I can understand some noticeable or even measureable amount of wind depending on the object, but are we just talking 'high wind' in relative terms (meaning 2-4 kts? 5-7 kts? 8-10 kts? what?)?
Maybe I'm just old-school, but I'm pretty wind-intolerant on B's (especially low ones).
gardner
K. Gardner Sapp
Executive Director
The Alliance of Backcountry Parachutists, Inc.
P.O. Box 38202
Atlanta, Georgia 30334
gardner@backcountryparachutists.org
www.backcountryparachutists.org
A PCA or staticline, correctly done will open higher than a DB, Winds will play a major factor in and make a major difference in opening to flyability times, IMHO. Please explain if you think it otherwise.
take care,
space
I assumed a DB would open the highest...right from the start you're eliminating 9 feet of bridle, and generally the canopy is going to hit the air sooner...yes?/no?...Is the load being placed on the top of the canopy with a s/l or pca your reason for thinkin' otherwise? Does this "pre-load" cause/allow the canopy to fully inflate faster? Not tryin' to start an argument, only tryin' to learn...also the "opening alt" thread would probably be a good place to continue this discussion...
About two years ago, I did some relatively unscientific measurements (I weighted a rig and static lined it off with a spring scale measuring weights, then frame by framed the video).
It appeared to me that the maximum force on a velcro rig was at bridle extension (initial shrivel flap loading), and was around 20 lbs.
Max force on a pin rig was less (around 15 lbs) and occured on canopy extraction (after pin extraction).
I was alone, and using an 80' bridge for drop testing, so there was no test jumper (just a bunch of weights in a haulbag lashed into the rig).
Not very scientific, but it was the best I could rig up one bored weekend.
--Tom Aiello
tbaiello@ucdavis.edu
A while back, I static lined a sub 200' span with some sick fellows in red. The wind was about 15 mph at exit.
On a building, I usually won't tolerate much wind. The most I've had is around 15 at exit and 5 on the ground, but that was a 600' building.
On a static line building, I'd say that wind over 5 mph probably grounds me. I static lined a 240' building (actually the crane attached to it) last week, in 5 mph winds and a light rain, and came away shaking. That's probably my limit.
--Tom Aiello
tbaiello@ucdavis.edu
I believe that a Direct Bag will open faster than a Static Line, primarily because it does not distort the pack job as much. The Static Line causes center cell strip, deforming the pack job, and both slowing the opening and degrading heading performance (often critical at sub-freefall altitudes)
The pack job with less distortion opens faster, and with better heading.
--Tom Aiello
tbaiello@ucdavis.edu
I think that this is the issue, the 9ft. correctly done, a PCA could put your bridle attachment point- waiting for -line-stretch at a higher level than can DB,. if one has a good PCAr, seems to me that you would just be 3ft below, The geometry of the AP to risers give one 2 advantages, centercell inflation first, and orientation with the shoulders for on heading, this is only considering a no wind condition!
DB has the wind nailin the bottom skin at the same time all over, which makes it less likely to open on heading as a result of lack of geometric orientation to the jumper when compared to a PCA/SL which has the canopy´s center cell extended to line stretch, center cell extraction has only been an issue with FF, not with DB/PCA/SL or what do you think (anyone)?
take care,
space
>Okay, does anyone think it is possible to do a 200' b with a static line?
I agree with the consensus above. It should be no problem to static line a 200' object.
>Is it bad mojo to leave evidence?
In my opinion, yes. I'd say you're best off to clear the static lines away after the jump (either by having ground crew at the exit point retrieve them and walk down, or by going back up yourself after landing). At a minimum, you ought to clean up any left over static lines (from previous jumps) before each load, and have the last jumper clean up everyone else's gear before exiting.
>How would you go about doing this, attach somthing like an 80lbs break cord to your bridle?
A few months ago, at a friend's request, I wrote a short set of instructions on one possible static line setup. I'll post those instructions here. Please remember that I am not an expert, and that you need to evaluate the system for yourself. I have doubtless made oversights and errors, so please post any corrections that you think are necessary.
___________
Static lines are pretty simple. All they really entail is using some kind of breakable cord to attach the bridle to the object. Here's a rundown on one fairly standard method.
While still at home, starting with a packed rig:
1) Find a relatively cheap sling, and a carabiner you can afford to lose (you can replace these components with all kinds of stuff—I know one jumper who uses sailing lines and clips, and BR used a stainless steel cable and clip on the HOPE building escape rig--just make sure the gear you use is bomber, because if it breaks, you'll end up riding the white bus with the flashing lights). You'll leave these at the exit, and will either have to abandon them, or retrieve them after the jump.
2) Tie the break cord through (a) one end of the sling, and (b) the PC attachment point on your bridle (attach it to the bridle itself, not the PC, as it will load straighter, and be less likely to break prematurely). Use the standard static line knot. You can learn it from anyone who has packed static line rigs or teach yourself—I have attached a diagram below. Use this knot to minimize bends (weak points) in the line, to ensure consistent breaking tension.
3) Use a tailgate rubber band to control the bridle (S fold the bridle into the rubber band, so it will slide out easily).
4) Pack your PC with the whole mess (static line, carabiner, bridle, etc) all inside the PC, where you would normally stow the bridle. This step isn't critical, but it does make it much nicer to get the whole setup to the exit point.
At the object:
5) Put on your rig normally, with the PC still stowed. This avoids confusion with the bridle, and possible misrouting.
6) Unstow the PC, and have a friend check the bridle routing.
7) Use the carabiner to girth hitch the sling onto the exit point (hand rails are pretty good for this, but you may have to improvise). Sometimes, it helps to bring along a long sling or piece of rope/cord and some protection, so you can create an anchor to S/L off of (I used half my rack, and two forty foot slings creating the anchor for one 150' cliff, and I know that someone got so sick of building anchors at one popular static line cliff that they sank two bolts to static line off).
8) Climb onto the exit a few feet away from the static line, so that you don't tangle with it. Be careful to control the whole setup while you climb over.
9) Always have someone check the routing of the S/L and bridle before exit. Some people actually hold the bridle and or PC loosely in one hand (as if PCAing themself). I only do this in high wind (to keep the PC deflated), though.
10) Exit, and get on the opening fast. You won't have much time to fly.
Notes:
1) Leave the PC attached to your bridle. People have died taking their PC off, when the break cord broke prematurely.
2) Get your break cord from one of the gear manufacturers, or from a drop zone (it's the same stuff they use for student static line rigs). I don't recommend using electrical tape, shopping bags, condoms, or reeds (all of which I've seen used at various times, mostly by folks with funny accents and a tendency to say "no worries, mate!")
3) You will want to practice your S/L off something else (like a nice high span) to make sure you've got it straightened out.
4) I'm sure I missed something. Feel free to contact me via email, or post questions, if you want clarification.
___________
--Tom Aiello
tbaiello@ucdavis.edu
>Also I wanted to comment on the pilot chute. On
>any object where there's a possibility the pilot
>chute will help (for me this is anything over
>about 140 feet), I leave it attached. We've
>been doing a lot of jumps from a local 111-foot
>S, and finally I decided to remove the pilot
>chute. My thinking was this: On this
>particular object, the pilot chute probably
>won't do me any good in the case of a premature
>break.
This is not entirely true.
If the break cord prematurely breaks at the very start of the deployment sequence on a 111-foot object, then yes, it is highly debatable whether the majority of manufacturer-standard pilot chutes currently available would make a difference.
However in my experience, the majority static lines (or p/c holders) fail when the canopy is lifting out of the container. This point is when the static line is loaded the most (or the point when the p/c holder panics the most because they feel the loading and think they will get pulled over the edge).
At this point the static line has done some of the work and the p/c may be able to finish the job in less than 81 feet (111 feet of altitude minus the 30' of the distance from your toes to your p/c on line stretch). (Note you'd still need some altitude for bottom skin expansion and deceleration to occur otherwise just reaching line stretch won't be much help).
Basically the later into the deployment sequence the static line fails the more chance you will have.
A static line failure or a prematurely released PCA usually results in a much higher opening than what a throw-n-go freefall would have.
However that is not to say you should always leave your p/c on during a static line. There are situations that warrant it's removal in order to simplify the system, reduce p/c snag potential or improve the flight characteristics of the canopy.
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