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Just wondering and curious who use a shorter bridle for low free fall (sub 190 ft)?
if yes, which lenght and why? (4ft instead of 6ft or...ecc)
Thanks

Why would that be a good idea??

or maybe just a three inch bridle from pc to lower pin and hope for the best. im thinking an 80 ft jump! thats logical right....



Bahhahahah!

I am wondering if someone did a timed canopy time on hop´n trow, and 0,5 - 1 sec freefall. How much is the difference?

up there is write that this a Technical Base Forum, no social-politic forum...
anyway thanks for your input

For that low of a freefall obviously you would want as much air catching the pilot chute as possible. A shorter bridle would just cause the standard dead air issue at a very low altitude, especially when you are talking about freefalling. What are your thoughts on the advantage of a short bridle? I can't see any advantages?

I'm guessing you're asking about a static line jump. I use a shortened bridle since that's how I was taught and it makes sense to me. Off the low stuff a couple extra feet can make the difference between landing broken or unbroken.

Check out the first post in this thread.

http://www.basejumper.com/...uest=6249021#2885553

Here's a video of Greeny using his shorter bridle setup from a 148' bridge.

http://www.youtube.com/watch?v=GlttsWMO4F4

 
I've been using a 7' bridle for SD freefall jumps with no problems whatsoever. Lower airspeed -> smaller burble -> shorter bridle.

My experience is that your above statement is absolutely wrong.
One´s burble is always the same volume as the volume displaced by one´s body irregardless of speed. The angle of the burble changes over velocity. The width and the height of the burble changes but typically remain dynamically ratiometric with each other through the acceleration. As in the at Xspeed, one would have a 6ft wide burble base extending 9ft up.
At XplusSpeed the burble would have say 3ft x 18ft.
The width of one´s burble is more important than the height. The length of the burble spreads out but the PC diameter remains the same. There are calcs on prop blasts that will ascertain this.
9ft has been a great middle ground for SU or SD.

Take care,
space

Your post says freefall...seems to me that if you're thinking that a slightly shorter bridle will make an object jumpable vs not, common sense says to find something taller to freefall from.

If you haven't already done so, put a large pc on there, like 48" if you're gonna play dirty low.

Your burble is always gonna be there to an extent bro. Best bet is to have a standard sized bridle to avoid any "in tow" issues.

as with so much in this sport...
your mileage may vary!

thus, if you think this is a good idea, try it off a forgiving object! develop your own experience base, with YOUR equipment. find out what works for you and your comfort zone. why trust internet advice when deciding to accept the additional risk?

(note: sub 190 is kinda vague. there is a big difference between the 140's and the 180's!)

i can loan my 52" :)

I think it would be a good idea for terminal... I think there is a reason we've had PC in tow fatalities in base. I know I've had knots in my bridle 2 times and it's not a good feeling after you begin packing. I've thought about shortening my bridle to 7' for terminal. Handheld and low delays I'm not as worried about it. Because of the lower airspeed not putting the bridle in a knot configuration.

The cause of bridle knots (and bridle-over malfunctions) is almost invariably pitch technique, not bridle length.

If you are getting knots in the bridle, the problem is how you are throwing the PC, not the length of your bridle.

If you flick your wrist as you release the PC (99% of the world's skydivers and 95% of the world's BASE jumpers do this), you will spin the PC so that the "flailing wad of bridle" precedes the PC to bridle extension. When this happens there is a small chance that the PC will interact with the bridle in a negative way, usually developing a bridle knot (but very, very occasionally causing a bridle/PC entanglement).

The fix to this problem is to improve your pitch technique so that the PC/bridle bundle moves to full bridle extension in good order, with the PC leading, apex first, followed by the bridle. Most people find it's easier to achieve this by making one of two modifications. They either:

a) switch their grip to "underhanded" so that they are wrapping the "web" of their hand around the "bulb" instead of palming the apex of the PC, or;

b) cocking their wrist backward as they release the PC, to create a shot putting type motion rather than a flicking motion.

It can also be helpful to think about delivering the PC toward your feet (only if you are flat--this can be quite dangerous if you are still head high), rather than your head.

I spend about 30 minutes on this material in my First Jump Courses, and I believe that everyone should know (and review) it.


edit to add: Note that there are also possible packing, rigging and gear modification fixes to this issue, for example packing the bridle into the pouch before the PC, or creating a "bridle pocket" that stages the bridle behind the PC and separate from it.

To elaborate a bit further (perhaps unnecessarily), the defining characteristics of a "good" PC toss are:


1) Delivers the PC to bridle stretch with authority;

2) Delivers the PC to bridle stretch in the best possible position to inflate immediately (or in the case of ultra low zero delay jumps, already inflated);

3) Keeps the PC/bridle bundle in the proper orientation (apex of PC leads, followed by bulk of PC, followed by bridle) for the full path of the PC travel to bridle extension.

I think this may be saying the same thing, but;

I read some US military research suggesting that the "burble" of a falling body is at no time greater than twice the width of the body (the shorter of the two dimensions presented to the airflow). The burble approaches this height logarithmically, so that most of the burbles "height" (distance above the falling body itself) is achieved in the last second before reaching terminal velocity. At go-and-throw type (very slow) airspeeds, the burble height was extremely small (single digit inches at most) on a human sized body.

This suggests to me that very short bridles could actually be an excellent tool to use for extremely low (sub 180 foot) freefall deployments.

Note that I am also a fan of pre-inflating the PC by using the "loft up" technique of PC deployment, where the PC is fully inflated and "placed" at bridle extension (easy to achieve with a 3-5' bridle) prior to the jumper committing to the exit.

I believe that the OP was asking about freefall.

The reason that we use a shorter bridle (or attach closer to the container) for a static line deployment is to reduce the chance of premature break cord separation.

When dropped 9' (standard bridle length), a velcro rig will create a premature break cord separation (i.e. the break cord breaks before the container opens, from the strength of the shrivel flap) a statistically significant percentage of the time (something around 5% is likely).

When the bridle length (or attachment point) is reduced to 4.5' (i.e. you've tied an overhand knot halfway down the bridle to attach to), the percentage of premature breakages falls to a number that is statistically unobservable in hundreds of test drops.

This data was primarily gathered starting with the Apex BASE Super Bowl demo jumps, which is when many people started using shorter bridles (or, more commonly intermediate attachment points) for static line jumps.

It's mostly not about height change--it's about reduction in variability. Because the shorter bridle allows you to fully preinflate the PC and place it at bridle extension, it allows you to virtually eliminate the chance of a PC hesitation, which allows much greater consistency. It is consistency (not faster opening speed) which is the holy grail of ultra low freefall.

This has happened when I believe the bridle or mesh becomes exposed before the bundle hits the airstream. I think I may modify my packing PC technique because at least in my case I think it's due to that.

Good to know :)

I was waiting this.
I think the same.

On a roll there!
Nice!

As you say, I also think the burble is not relevant at very low airspeeds. But for me important (maybe it is just a head thing) is the snag force to pop the pins or that could help me at any problems if the bridal gets caught at a corner of the container or any other place. This is why I very much prefer a bit of extra bridal to increase the snag force a bit to avoid at any means a pc in tow which would be deadly at low airspeeds. And I think the extra freefall time it takes to extract the extra 2 feet is not relevant in terms of opening speed of the canopy.

Thank you for all those good quality posts and information!

Do you have any information about the delays most of bridle knots occur? I always thought it's the longer ones. Never seen one personally (thank God!) but both cases I am aware of was terminal.

The thing that bothers me about that is that with longer delays the bridle is blown up as soon as the PC exits the pouch no matter how you hold it. Plus the same violent air flow orientates the PC apex down and mesh up (or even worse induces a vertical spin) as soon as extracted by the handle, spoiling completely the whole sequence, leading to a state where the bridle is waving above the PC ready for interaction
Can the bridle retention pocket prevent this? Folding the bridle inside folds of the PC apex can lead to hesitation, so it's not a good idea.
Can you suggest any other way to prevent the bridle from escaping that I'm not aware of ....

Personally I can see no other way preventing this scenario except of a violent throw, but I might be missing something ..


...sorry for the off topic

I did some test drops with a spring scale about ten years ago, and my conclusion was that this matters only on a velcro rig.

On a pin rig, with spectra (or other slippery material) loops, the pull force required to open the container is substantially less than the force required to extract the canopy. On a velcro rig, the pull force to open the shrivel flap is actually greater than the force required to extract the canopy in some cases.

For ultra low (sub 200') freefall jumps, I'd still recommend using a pin rig with slippery closing loops, checking pin tension after gearing up, and arching during the container opening (to ensure that you don't curl forward and increase the pin tension), though.

I don't think that we have a large enough sample to say with any certainty when "most" occur, statistically. I've seen bridle knots on delays from 3 seconds to terminal. Three of the four PC/bridle entanglements I know of happened at terminal, as well. The fourth was about a 4 second delay.



I'm not convinced that you can't effect this through pitch technique, even at terminal.



I don't know. But it's a good place to start working on the issue, because the drag from the wind probably won't extract the bridle from a pocket before the PC motion extracts it to bridle extension.




I was unaware that this could cause a hesitation. Can you explain how that happens, and what led you to this conclusion?

My opinion has always been that so long as the bridle is free to travel cleanly out of the PC (i.e. it's placed into a clear channel centered in the PC), it doesn't matter if you push the bridle folds up into the apex of the PC or not. Many people prefer to do this to create a more solid "handle" feeling to the PC, and I don't see that it causes any issues.



I think the bridle pocket is a good place to start. I've also seen some weird experimental systems with a bridle pocket sewn into the PC itself, to stage the bridle, but I never saw one that I thought was very good. There's also the idea of folding the bridle into the bottom of the pouch, before the PC is inserted, and keeping them separate.

On static line jumps I S-fold the bridle and stick
those folds in a tailgate band to control the slack.

Has anyone ever tried doing this on a stowed PC?
I am definitely NOT recommending it just curious.

Not to my knowledge.

this whole discussion looks like someone trying to make something which works good in to not to work good any more.

Let's complicate even more - it is funny to read how ideas blossoming fast!

Length of bridle works perfect in length of 7 to 10. No difference. What makes difference was described by Tom already ( Velcro vs.pin ). Also, For very low jumps place the bridle so that the fist pin which goes off is upper one not the bottom one. This way the force on bridle is even lower + there is no fear of bridle hooking the corner of the rig as the bridle goes out and away from the pack from the top, not the bottom.

Folding the bridle neatly and inside / next to mesh and that is it. Pure Rocket science this is!!!!

Not sure how it causes hesitation, but the advantage of wrapping the s-folded bridle tightly inside the mesh folds of the PC is that it stages the bridle and prevents excess from dropping out prematurely, which can flap around and, when the PC goes through the resultant bridle loop, would lead to a bridle knot, or worse.

There are many examples of video / photos I've seen (can't reference them though) where on a short (0.5s) delay I've seen an upside down PC and the bridle following more of an "N" shape than a straight line between the PC and the container. This is most likely due to lack of staging and premature dropping of the bridle, and should be avoided.

Oh sorry, my poor english again.. I should have said folds of mesh. Basically I was referring to the#22 and #26 posts of this topic : http://www.basejumper.com/..._latest_reply;so=ASC
"hiding the bridle inside the mesh to prevent it from escaping" kind of thinking... Pendragon just mentioned
but it's a dangerous idea anyway, shouldn't have mentioned it

Thanks Tom