Basejumper.com - archive

Curiosity has risen after a recent conversation. Any experience with velcro PCA, as opposed to a breakcord, on a BASE jump? How does it compare to , say, a 60 lb breakcord?

Can you elaborate on "velcro PCA"? Are you creating a system with velcro used to attach the static line to the object?

I've measured velcro container opening forces in the range of 15 pounds (as low as 11, as high as 19). That's a heck of a lot lower than the rating of most break cord.

What kind of system are you envisioning?

Actually, you sort of just answered my questioned. I figured it needed less force, but wasn't quite expecting it to be that low.

Just taking a look at this:

http://www.paragear.com/....asp?group=163#M5450

A configuration for S\L using this is supposedly safer than the breakcord type (in skydiving). I was recently discussing with someone the possibility of using it in BASE, and was wondering if practical experience was out there, and most importantly, how much force is needed.

Thanks.

Ah. Those systems appear to be intended to extract the PC prior to deployment.

Theresa Tran (see #30) proved that this was a bad idea in the BASE environment.

Yeah, that's bad. I wasn't thinking of PC extraction, though, that is, indeed, the intended use. Rather, I was thinking more of using it to tie off the PC, like a reusable and, more importantly, relatively consistent breakcord. It might not be too good of an idea, after all.

The jump is almost that of #30, only the PC would be tied off on the ground, not pulled from the BOC. Was that R-------- (I think that's what it's called) that she went in on? The one the BR guys jump a lot?

Close enough for public discussion.

Thanks for writing it before me,im happy you did while im not sure i could explain it rigth..

Ill go for the breakcord,just waiting on a shipmentThanks Blair

I didnt ask you Tom(about other ways)while you didnt recomend it in the artikle we talked about(PM),so i didnt think you would recomend other wayswhich you still says here

I now have this final Q..
How does cold water effect on a nude a## while landing on it(will raise my leg,and land on it,so i dont take so much force on my leg).

See:

Poynter's Vol I, 4.152 Fastener Tape, Hook and Pile, Nylon Mil-F-21840

this section lists specifications of velcro types, as well as sheer, peel and tension specs for velcro types.

Poynter's Vol II, 7.78 Static Line Manufacture

This section discusses static line manufacture - and particularly in this volume - shows a sandwich-type construction for the velcro pca. It does not mention pull forces attainable with this construction.

I guess the best thing to do is build something and pull-test it. As has been mentioned before, velcro is pretty consistent. The key is to design something that generates enough pull force. in the straight sheer direction, it can hold pretty well; hence the creation of the 'shrivel flap' for wayward headdown base jumpers.

But what I wanna know.... how are you gonna get the bit that you left on the object? For me that would be the determining factor as to whether to build it or not. It would be fine for a legal object where you can go back (or an object that you frequent), but it seems to me it leaves something pretty obvious (from the whuffo, "what is this and what's it doing here?" standpoint) behind.

ANyway.. lemme know how it turns out.

Gardner

while it were me he had that conversation whith..

I´ll have ground crew on the S,filming me,but i dont want them to PCA me..

For a more reasonble use of an tool to SL i agree whith you,i also dont want to leave too many footprints..

Hey Gardner, how ya doin'? sorry I missed you when you were in the area....good point about leaving something behind....one of my friends built a 'sandwich' type velcro s/l device...parts of which remained on a local 'S' for years....for the most part it worked very well, unless he got lazy and didn't keep the pile in good condition...then it tended to release just a bit prematurely-usually about half way through pulling the shrivel flap off....makes for some interesting video.
cya
michael

Worst case scenario, you're out six bucks (if you didn't make your own). I'd imagine a lot of low objects like that (save maybe towers) wouldn't be too tough to go back up and get your stuff.

I'd imagine that a velcro PCA would definitely come apart pretty easily. So let's say your PC and bridle are out. You have a strip of velcro on the bridle near the PC, and the velcro PCA attaches to it. You securely tie down the velcro PCA. Is there a downside to the velcro being too weak? I'll see if I can pull test some different velcros tomorrow.

I'd like to hear other people's results, as well.

Um, no. Worst case scenario some worker spots it, wonders what it is, keeps an eye on it, notices that it shifts position, hangs out and waits for you, and calls the police...

You get the idea.

But Tom under a SL you´ll always leave somthing behind rigth?un less you have some one up there or get it removed fast..or what?

At the dz that I Jm at they just started using zip ties instead of velcro on the pilot chute assist (on the static line). I asked the owner about this new method that we are using. I thought that maybe it was a new method being used and that they were buying these zip ties from para-gear for example. They are using regular zip ties from the hardware store. Apparently they have a test strength on the outside of the package. They are using 18 lb zip ties and doubling them. They pull tested them quite a bit before starting jumping them. The owner claimed that when doubling them up they break consistently around 36 lbs. He told me that there were other test strengths also.

Has anyone ever experimented with zip ties? I don't know why they wouldn't work (I have seen electrical tape, grocery bags and fishing line).

Matt

Not if the birds eat it. I bet you didn't think about that one, eh? Er...

Pull tested brand new velcro ten times. Ten for ten, it was 19 lbs (8.5 kilo).

Cool, would you mind describing the methods you used to test this?

I had about six inches of velcro. I tacked the male down to the floor on end for five tests, and both ends for the other five. I put the hook on fish scale in the center and put the female end over it, and pulled. The fish scale has a plastic "ring" around it that slides easily and is pushed by the indicator on the scale so that it stays in place after the pull has happened... a pretty normal piece of equipment at a DZ. This is the hook and loop type, not the "frizzy" kind. I'd like to try it on the frizzy type, as well.

I'll be putting velcro on my bridle, as I'll have the BASE PC pouch on my S3, and I'll pull test that, as well. That will be a better simulation, but I'd imagine the results will be similar, if not identical.

I have some pretty good experience with zip ties. We use 50-70lb ties. Why? Well, the rating has no tolerance. It could be +/- 50 lb.

I've seen a zip tie fail and the jump essentially became a 200 foot head down freefall. Hilarious on video but not good for laundry.

Be aware that placing a zip directly onto an object may weaken the zip considerably. For example, take a 50 lb zip and attach it to some angle iron. Now measure the force required to break it at different angles. My experience shows that this varies considerably.

For sub 160 foot s/ls I use two zips. One is a smaller loop than the other ensuring that it is broken before the backup and not simultaneously which would cause a large force on the bridle attachment point.

Never use zip ties in extremely cold weather. The material properties can be very different and they become brittle and break with reduced force. This depends on the material of the zip tie but the material spec isn't always apparent.

Always s/l with a correctly sized pilot chute in case the zip breaks before extraction.

Always get it on video. If not, it didn't happen.

S.

Okay see attached:

...this is just a design idea. USE AT YOUR OWN RISK!

So what do you all think? BLACK NASTY SQUIGGLY DEATH? or not?

Apart from a few obvious drawbacks I see no reason why it wouldn't work. The biggest drawback I see is the reduction of pull force as the diameter of the object around which the loop is wrapped increases. Resultant (vector) forces go way up as the angle of the "Y" increases - much the same as with climbing anchors.

Another drawback may be risk of snagging the bridle at the point where the webbing layers are stacked.

Another drawback may be the wear that the one piece of bridle may get when rapidly whipping around the object to which it was attached.

Another drawback is the size of the object to which you can tie off is limited by the amount of bridle you've built into the design

benefits? I dunno... other than you take the bit with you when you depart... nothing left behind.

The breakload should be increased above a single sandwich-type velcro construction because of the two legs... a little more load distribution.
____________________

This is just an exercise in theory... this has not been constructed. construct and jump at your own risk. you will be a test jumper.

Comments? Flames? Suggestions?

Later,
Gardner

hey man.. no worries. I scoped what we talked about. need two vehicles and a driver. it's a really busy place under there...

anyway, next time I plan to be in the area I'll call ahead and maybe we can do that and more.

take care,
Gardner

did i misunderstand the drawing or would this be a permenet setup?
If so i think it will be in the way,while jumping not SL,besides that i cant see any.. but im not your test jumper

yes it would be permanent, but you'd have a S/L bridle... and a regular freefall bridle..

you change pilot chutes, don't you?

Gardner

nope i usaly use my allaroundpc,i just turn a knot on it until i get the size i need

i see what you mean

I stuck around for several more hours doing tests (crappy weather at the DZ), and experimented with different angles. I'm at work, and will give some more details later, but the hardest pull for any configuration was 36 lbs, and after about 50 pulls, wear began to show. After 100 pulls, my 19 average went down to 16.

I like this design you've come up with for keeping the PCA with you. You've mentioned the drawbacks, but more specifically, based on yesterday's tests, the object to which the PCA is anchored needs to be somewhat thick. I found that if the angle of the "Y" is too pinched, the force was higher (pinched almost all the way in is when we were getting 36 lbs). If the "Y" is at least, just guessing here, 35 degrees or so, you're looking at about 23 lbs of pull force. Basically, the wider the "Y", the less force you need to part the velcro. Which is why when the velcro is flat (basically, the "Y" is as wide as possible, you get the minimum pull force of 19 lbs). Maybe if there was some sort of strap, constructed like a chest strap, on the side opposite the velcro, you could tighten or loosen the device to get the appropriate angle of the "Y", regardless of the diameter of object.

Covered area made a difference, as well. 1" by less than 3" took drastically less force than 3" or over. 3" and up was pretty much the same across the board, give or take a pound.

I like the idea of velcro because it is predictable, cheap, and easier to attain than breakcord. I think that, for the most part, it would work well as a PCA for tied down PCs. I don't know if I'd trust it for extracting the PC, though.

Yeah, very cool idea. Just examining the pic a little more. Making it permanent would be just fine. You're probably using the same PC for all SLs, so having a permanently modded bridle probably wouldn't be a big deal.

Here's a stow you could add to it.

Have fun with it guys...count me out.

Hey, just theorizing.

We've come up with the pros of this concept / device. Now I'd like to hear the cons. That is, reasons why this wouldn't work, as opposed to just, "My feet are coated... coated in chocolate." What?

Not quite following the chocolate thang, but I don't see what's wrong with break cord.
When it comes to gear, I am a huge proponent of keeping it as simple as possible. Using break cord for a s/l jump falls into this category (I personally don't like s/l jumps at all). IMHO, the bridle itself, as one's sole means of survival from launch to extraction, should be as clean, strong and simple as possible. Just the thought of pin bartacks or shrivel flap connections breaking while the rig is packed sends a cold shiver up the spine...having what looks like a much more complex system attached to the bridle [such as the ones drawn] increases the likleyhood of failure.
It seems to me that the more holes a needle puts in my bridle, the weaker my bridle will be, ultimately. Please correct me if I'm wrong.

Again, I don't even like s/l jumps, but that's just me.

haha Im wondering if Manbird is still jumping?